TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Wurzler, Nina
A1 - Hampel, Marco
A1 - Witt, Julia
A1 - Schenderlein, Matthias
T1 - In situ imaging of corrosion processes
N2 - The presentation summarizes our recent results on the coupled electrochemical methods for high resolution corrosion studies. The combination of Scanning Electrochemical Microscopy (SECM) and multielectrode (MMA) based real-time corrosion monitoring was presented as a new method for achieving high time resolution in local electrochemical analysis. Correlative imaging by means of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) was demonstrated as a tool for the investigation of local corrosion processes initiated by the intermetallic particles (IMPs) on AA2024-T3 aluminium alloy.
T2 - BAM-IfW Workshop
CY - Dresden, Germany
DA - 28.03.2019
KW - MIC
KW - Atomic Force Microscopy (AFM)
KW - Corrosion monitoring
KW - Corrosion
PY - 2019
AN - OPUS4-50291
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Wurzler, Nina
A1 - Hampel, Marco
A1 - Sobol, Oded
A1 - Schütter, Jan David
T1 - Effekt der Vorkonditionierung und Umweltparameter auf die Anheftung und Biofilmbildung
N2 - Aktuelle Ergebnisse des Fachbereiches auf dem Gebiet MIC.
T2 - Treffen der GfKORR/DECHEMA Fachgruppe MikroMatz
CY - Berlin, Germany
DA - 09.04.2019
KW - MIC
KW - Korrosion
KW - Korrosionsüberwachung
KW - Biofilmbildung
PY - 2019
AN - OPUS4-50292
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Almalla, Ahed
T1 - Application of atomic force microscopy (AFM) for in situ corrosion studies of thin film covered AA2024 T3 aluminium alloy surface
N2 - The performance of functional coatings and adhesively joined hybrid components relies strongly on the stability of the polymer-metal interface. With the increasing utilization of multi-material structures in the automotive and aerospace industry, it is of great scientific and technical interest to understand the processes leading to interface degradation and to develop novel strategies to increase corrosion and delamination resistance.
The aim of this project is to develop thin epoxy-based films and their carbon nanofiller loaded composites on aluminium alloy AA2024-T3 as a model system and to investigate their interfacial stability under corrosive and coupled corrosive-mechanical load. Spin coating was used for the layer-by-layer deposition of poly[(o-cresyl glycidyl ether)-co-formaldehyde] and poly-(ethylenimine) bi-layers. Atomic force microscopy (AFM) results indicate a very homogeneous and dense film with low surface roughness. Carbon nanofillers were introduced either by mixing into the coating components or in between individual layers to control the separation between the carbon nanofillers and alloy surface. The film chemistry and barrier properties were characterized by means of spectroscopic and electrochemical methods, respectively. The degradation and delamination behavior of the epoxy-based films was characterized by means of in situ AFM corrosion experiments. The quantitative imaging (QI) mode allowed the observation of hydrogen-generation induced blister formation during exposure to corrosive electrolyte and how the local corrosion processes evolved with exposure time. Complementary energy dispersive X-ray spectroscopy (EDX) analysis was performed to correlate the corrosion behavior with the different intermetallic particle chemistries and distributions. The presentation will summarize our results on the effect of interface chemistry and carbon nanofiller – alloy separation on the initiation of local corrosion processes on thin film covered AA2024-T3 aluminium alloys.
T2 - EuroCorr2019
CY - Sevilla, Spain
DA - 09.09.2019
KW - Corrosion
KW - Atomic Force Microscopy (AFM)
PY - 2019
AN - OPUS4-50293
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Fernandes Jamar, Marina
A1 - Stepien, Daniel
T1 - In situ atomic force microscopy (AFM) analysis of materials under combined corrosive and mechanical load
N2 - In service, most materials are operated under simultaneous corrosive and mechanical load and there are very few methods capable for testing material degradation under these conditions, especially when it comes to high resolution analysis. For this purpose, in this work, a tensile module capable of uniaxial stretching and compression with up to 5 kN force was integrated into an AFM stage. The elimination of the need for sample unmounting and remounting and the resulting possibility of keeping the sample under constant mechanical load during AFM measurements not only enables a precise positioning of the area of interest but also allows for the analysis of processes in the elastic deformation regime.
This methodology was demonstrated for two case studies. Scanning Kelvin Probe Force Microscopy (SKPFM) was used as the main tool to characterize the deformation behavior. Moreover, a flexible electrochemical measurement cell was used to enable electrochemical analysis by means of electrochemical impedance spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) during AFM measurements at different levels of strain. The in situ AFM results are complemented by microstructure analysis by means of electron backscatter diffraction (EBSD).
In the first case study, the deformation induced delamination of a thin organic coating on AA2024 T3 aluminium alloy was investigated as a function of alloy surface treatment. The formation of cracks in the insulating passive film enabled an early detection of deformation processes by means of SKPFM. The second case study focused on the comparison of corrosion and deformation behavior of conventional and additively manufactured 316 stainless steels. In comparison to the conventional 316 stainless steel, the effect of processing was clearly detectable on the additively manufactured material as zones of inhomogeneous potential, which also affected the initiation of local corrosion processes. The contribution will provide detailed information on the new AFM setup and summarize our results from both case studies.
T2 - EuroCorr2019
CY - Sevilla, Spain
DA - 09.09.2019
KW - Corrosion
KW - Coupled corrosive and mechanial load
KW - Atomic Force Microscopy (AFM)
PY - 2019
AN - OPUS4-50294
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Schenderlein, Matthias
A1 - Hampel, Marco
A1 - Almalla, Ahed
T1 - Coupled electrochemical, microscopic and spectroscopic techniques for the analysis of local corrosion and mic processes
N2 - Summary of the research topics of the division 6.2 and recent results
T2 - HZDR-IRE Institutscolloquium
CY - Dresden, Germany
DA - 24.09.2019
KW - MIC
KW - Localised corrosion
KW - Corrosion monitoring
KW - Biofilmbildung
KW - Atomic Force Microscopy (AFM)
PY - 2019
AN - OPUS4-50295
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Almalla, Ahed
A1 - Fernandes Jamar, Marina
A1 - Stepien, Daniel
T1 - Untersuchung lokaler Korrosionsprozesse mittels kombinierter elektrochemischer und mikroskopischer Methoden
N2 - Aktuelle Forschungsergebnisse - Korrosionseigenschaften von AA 2024-T3 und AM-316 unter gekoppelter korrosiv/mechanischer Beanspruchung.
T2 - MPIE Düsseldorf, Sitzung der GfKORR Arbeitskreise Grundlagen und Simulation und Korrosionsuntersuchung und überwachung
CY - Dusseldorf, Germany
DA - 20.11.2019
KW - Corrosion
KW - Atomic Force Microscopy (AFM)
KW - Coupled corrosive/mechanical load
PY - 2019
AN - OPUS4-50296
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Wurzler, Nina
A1 - Witt, Julia
A1 - Dimper, Matthias
A1 - Wagner, R.
A1 - Lützenkirchen-Hecht, D.
T1 - Changes in passive film chemistry of stainless steels in the presence of iron reducing bacteria
N2 - Summary of the results obtained at DELTA-Beamline 8 in 2018.
T2 - DELTA User Treffen
CY - Dortmund, Germany
DA - 28.11.2018
KW - MIC
KW - Corrosion
KW - XANES
PY - 2018
AN - OPUS4-50312
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Özcan Sandikcioglu, Özlem
A1 - Wurzler, Nina
A1 - Hampel, Marco
A1 - Witt, Julia
A1 - Schenderlein, Matthias
T1 - Combined electrochemical techniques for the investigation of corrosion processes
N2 - Short presentation of BAM, a summary of the methods available in FB 6.2 and recent results on MIC and high resolution corrosion studies
T2 - Institute Seminar: Jerzy Haber Institute of Catalysis and Surface Chemistry
CY - Cracow, Poland
DA - 07.11.2018
KW - MIC
KW - Corrosion
KW - Atomic Force Microscopy (AFM)
KW - Combined corrosive and mechanical load
PY - 2018
AN - OPUS4-50313
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Ávila Calderón, Luis Alexander
A1 - Hammerschmidt, T.
A1 - Stotzka, R.
A1 - Forti, M.
A1 - Olbricht, Jürgen
A1 - Skrotzki, Birgit
A1 - Lenze, A.
A1 - Gedsun, A.
A1 - Hickel, Tilmann
A1 - Tsybenko, H.
A1 - Chmielowski, M.
A1 - Hunke, S.
A1 - Shakeel, Y.
T1 - Demonstration of the Infrastructure Use Case 02: Framework for curation and distribution of reference datasets
N2 - In our current view, reference datasets in the MSE domain represent specific material properties, e.g., structural, mechanical, … characteristics. A reference dataset must fulfill high-quality standards, not only in precision of measurement but also in a comprehensive documentation of material, processing, and testing history (metadata). This Infrastructure Use Case (IUC) aims to develop a framework for generating reference material datasets using creep data of a single crystal Ni-based superalloy as a best practice example. In a community-driven process, we aim to encourage the discussion and establish a framework for the creation and distribution of reference material datasets. In this poster presentation, we highlight our current vision and activities and intend to stimulate the discussion about the topic reference datasets and future collaborations and work.
T2 - NFDI-MatWerk Conference
CY - Siegburg, Germany
DA - 27.06.2023
KW - Referenzdaten
KW - Reference data
KW - Creep
KW - Metadata schema
KW - Syngle Crystal alloy
PY - 2023
AN - OPUS4-57924
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Ávila Calderón, Luis Alexander
A1 - Hammerschmidt, T.
A1 - Gedsun, A.
A1 - Forti, M.
A1 - Olbricht, Jürgen
A1 - Stotzka, R.
A1 - Skrotzki, Birgit
A1 - Shakeel, Y.
A1 - Hunke, S.
A1 - Tsybenko, H.
A1 - Aversa, R.
A1 - Chmielowski, M.
A1 - Hickel, T.
T1 - IUC02 Framework for Curation and Distribution of Reference Datasets using Creep Data of Ni-Base Superalloys as an Example
N2 - In our current view, reference datasets in the MSE domain represent specific material properties, e.g., structural, mechanical, … characteristics. A reference dataset must fulfill high-quality standards, not only in precision of measurement but also in a comprehensive documentation of material, processing, and testing history (metadata). This Infrastructure Use Case (IUC) aims to develop a framework for generating reference material datasets using creep data of a single crystal Ni-based superalloy as a best practice example. In a community-driven process, we aim to encourage the discussion and establish a framework for the creation and distribution of reference material datasets. In this poster presentation, we highlight our current vision and activities and intend to stimulate the discussion about the topic reference datasets and future collaborations and work.
T2 - NFDI-MatWerk Conference
CY - Siegburg, Germany
DA - 27.06.2023
KW - Referenzdaten
KW - Reference data
KW - Syngle Crystal alloy
KW - Creep
KW - Metadata schema
PY - 2023
AN - OPUS4-57923
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zänker, Steffen
A1 - Scholz, Gudrun
A1 - Krahl, Thoralf
A1 - Prinz, Carsten
A1 - Emmerling, Franziska
A1 - Kemnitz, E.
T1 - Luminescent properties of Eu3+/Tb3+ doped fluorine containing coordination polymers
JF - Solid State Sciences
N2 - Lanthanides doped coordination polymers (CPs) with different binding motifs were synthesized to investigate the influence of the different fluorine positions in the structure on the decay time τ of the excited states. Fluorine can be integrated into the network mechanochemically via a fluorinated organic linker, here barium tetrafluoroterephthalate Ba(p-BDC-F4)2 or directly via a metal-fluorine bond (barium terephthalate fluoride BaF(p-BDC)0.5). The CP with a metal-fluorine bond shows the highest lifetime of the excited states of lanthanides (Eu3+, Tb3+ or Eu3+& Tb3+). The excitation of the lanthanides can be performed directly via the excitation wavelength typical for lanthanides and via the excitation wavelength of the linker. This enabled the simultaneous excitation of Eu3+ and Tb3+ in one CP. In the emission spectra (λem = 393 nm) of the mixed doped CPs (Eu3+ and Tb3+) the bands of both lanthanides can be observed. The integration into the crystal lattice and the homogeneous distribution of the lanthanides in the CPs is shown by X-ray diffraction, TEM, STEM-EDS measurements and the long decay times.
KW - Alkaline earth metal coordination polymers
KW - Fluorine coordination polymers
KW - Lanthanides doped coordination polymers
KW - Luminescence
PY - 2021
DO - https://doi.org/10.1016/j.solidstatesciences.2021.106614
VL - 117
SP - 106614
PB - Elsevier Masson SAS
AN - OPUS4-52559
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zänker, Steffen
A1 - Scholz, G.
A1 - Xu, W.
A1 - Kemnitz, E.
A1 - Emmerling, Franziska
T1 - Structure and properties of fluorinated and non-fluorinated Ba-coordination polymers - the position of fluorine makes the difference
JF - Journal of Inorganic and General Chemistry
N2 - As the most electronegative element, fluorine has a strong influence on material properties such as absorption behaviour or chemical and thermal stability. Fluorine can be easily integrated into coordination polymers (CPs) via a fluorinated acetate, here trifluoroacetate in Ba(CF3COO)2, or directly via a metal fluorine bond (BaF(CH3COO)). In the present study both possibilities of fluorine integration were tested and their effect on structure and properties of barium coordination polymers was investigated in comparison with the non-fluorinated barium acetate (Ba(CH3COO)2). In addition to the study of their thermal behaviour and their decomposition temperature, the CPs structures were tested for their application as possible anode materials in lithium ion batteries and for their sorption of water and ammonia. The properties of the CPs can be traced back to the individual structural motifs and could thus trigger new design ideas for CPs in LIBs and/or catalysis.
KW - Alkaline earth metal coordination polymers
KW - Lithium-ion battery
KW - Water stability
KW - Fluorine coordination
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524041
DO - https://doi.org/10.1002/zaac.202000360
SN - 0044-2313
VL - 647
IS - 9
SP - 1014
EP - 1024
PB - Wiley-VCH GmbH
AN - OPUS4-52404
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zänker, Steffen
A1 - Scholz, G.
A1 - Marquardt, Julien
A1 - Emmerling, Franziska
T1 - Structural changes in Ba-compounds of different hardness induced by high-energy ball milling – evidenced by 137Ba NMR and X-ray powder diffraction
JF - Zeitschrift für anorganische und allgemeine Chemie
N2 - Changes in the global bulk and local structures, of three different barium compounds (BaZrO3, BaF2, and BaFCl),were induced by mechanical milling and followed using X-ray powder diffraction (PXRD), subsequent microstructure analysis, and 137Ba solid state NMR spectroscopy. Harder materials like BaZrO3 experience significantly higher structural changes upon milling than softer materials like BaF2. Moreover, soft materials with layered structures, like BaFCl, show a pronounced structural change during the milling process. By combining PXRD and solid state NMR, detailed information on the changes to the global and local structures were obtained, which are of interest for mechanochemical synthesis, mechanically treated catalysts or ionic conductors.
KW - Mechanochemistry
KW - X-ray diffraction
KW - Solid state NMR
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-547397
DO - https://doi.org/10.1002/zaac.202200026
SN - 0044-2313
VL - 648
IS - 10
SP - 1
EP - 8
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-54739
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zänker, Steffen
A1 - Scholz, G.
A1 - Heise, M.
A1 - Kemnitz, E.
A1 - Emmerling, Franziska
T1 - New 2D layered structures with direct fluorine-metal bonds: MF(CH3COO) (M: Sr, Ba, Pb)
JF - CrystEngComm
N2 - New coordination polymers with 2D network structures with fluorine directly coordinated to the metal ion were prepared both via mechanochemical synthesis and fluorolytic sol–gel synthesis. Depending on the synthesis route, the samples show different particle sizes, according to SEM imaging. The crystal structures of barium acetate fluoride, strontium acetate fluoride, and lead acetate fluoride (BaFIJCH3COO), SrFIJCH3COO) and PbFIJCH3COO)) were solved from X-ray powder diffraction data. The structure solution is backed by the results from 19F MAS NMR, FT IR data, and thermal analysis. The calculated chemical shifts of the 19F MAS NMR spectra coincide well with the measured ones. It turns out that the grinding conditions have a remarkable influence on the mechanochemical synthesis and its products. Our systematic study also indicates a strong influence of the atomic radii of Ca, Sr, Ba, and Pb on the success of the syntheses.
KW - Mechanochemistry
KW - Coordination polymers
PY - 2020
DO - https://doi.org/10.1039/d0ce00287a
VL - 22
IS - 16
SP - 2772
EP - 2780
PB - Royal Society of Chemistry
AN - OPUS4-50789
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zutta Villate, J. M.
A1 - Viviana Rojas, J.
A1 - Hahn, Marc Benjamin
A1 - Anselmo Puerta, J.
T1 - Synthesis of 198Au nanoparticles sub 10 nm due optimization on local dose by Monte Carlo simulations for cancer treatment
JF - Journal of Radioanalytical and Nuclear Chemistry
N2 - To enhance the biological effects of radiation damage in cancerous cells, we present an alternative approach to the use of gold nanoparticles (AuNP), focusing on the synthesis and characterization of highly monodisperse, spherical radioactive gold nanoparticles 198AuNP. The size of the AuNP size was optimized with the help of Geant4/TOPAS particle scattering simulations, and energy deposition per nm3 per decay for varying radii (2–10 nm) was evaluated. This work is the foundation for ongoing experimental work to evaluate cell death induced by 198AuNP which aims for the use of radioactive gold nanoparticles in cancer treatment.
KW - AuNP
KW - Beta decay
KW - Beta particle
KW - Brachytherapy
KW - Cancer treatment
KW - Nanoparticles
KW - Nanoparticle
KW - DNA
KW - DNA damage
KW - Dosimetry
KW - Energy deposit
KW - Gamma ray
KW - Geant4
KW - Geant4-DNA
KW - Gold Nanoparticles
KW - LEE
KW - Low energy electrons
KW - MCS
KW - Microdosimetry
KW - Monte-Carlo simulation
KW - NP
KW - Synthesis
KW - TEM
KW - OH radicals
KW - Particle scattering
KW - Radiation damage
KW - Radiationtherapy
KW - Radioactive decay
KW - Radiolysis
KW - Simulation
KW - TOPAS
KW - TOPAS-nbio
PY - 2022
DO - https://doi.org/10.1007/s10967-022-08355-5
SN - 1588-2780
SP - 1
EP - 9
PB - Springer Nature
AN - OPUS4-55132
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zutta Villate, J. M.
A1 - Hahn, Marc Benjamin
T1 - Radioactive gold nanoparticles for cancer treatment
JF - European physical journal D
N2 - Dose enhancement by gold nanoparticles (AuNP) was shown to increase the biological effectiveness of radiation damage in biomolecules and tissue. Most of the current studies focus on external beam therapy on combination with AuNP. Here we present a Monte-Carlo study (Geant4) to characterise radioactive AuNP. Radioactive 198 Au emits beta and gamma rays and is considered for applications with solid tumours. To effectively apply 198 AuNP their energy deposit characteristics have to be determined in terms of intrinsic and extrinsic properties e.g. AuNP diameter, AuNP density, and their clustering behaviour. After each decay process, the energy deposit, inelastic scattering events, kinetic energy spectrum of secondary particles within the AuNP themselves and in a spherical target volume of water up to 1 μm radius were determined. Simulations were performed for AuNP radii ranging from 2.5 nm to 20 nm radius, different cluster sizes and densities. The results show an increase of the energy deposit in the vicinity of the AuNP up to 150 nm. This effect nearly vanishes for distances up to one micron. For the case of AuNP clusters and the same activity, the enhancement of the energy deposit increases with the relative gold mass percentage and therefore can be adjusted by changing AuNP radius or clustering behaviour.
KW - Gold
KW - Nanoparticle
KW - Cancer
KW - Monte-Carlo
KW - Simulation
KW - Cluster
PY - 2019
DO - https://doi.org/10.1140/epjd/e2019-90707-x
SN - 1434-6060
SN - 1434-6079
VL - 73
IS - 95
SP - 1
EP - 7
PB - Springer
CY - Berlin
AN - OPUS4-47964
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zuffa, Caterina
A1 - Cappuccino, Chiara
A1 - Casali, Lucia
A1 - Emmerling, Franziska
A1 - Maini, Lucia
T1 - Liquid reagents are not enough for liquid assisted grinding in the synthesis of (AgBr)(n-pica) n
JF - Physical Chemistry Chemical Physics
N2 - This study investigates the mechanochemical reactions between AgBr 3-picolylamine and 4-picolylamine. The use of different stoichiometry ratios of the reagents allows [(AgBr)(n-pica)]n and [(AgBr)2(n-pica)]n to be obtained, and we report the new structures of [(AgBr)2(3-pica)]n and [(AgBr)2(4-pica)]n which are characterized by the presence of the following: (a) infinite inorganic chains, (b) silver atom coordinated only by bromide atoms and (c) argentophilic interactions. Furthermore, we studied the interconversion of [(AgBr)(n-pica)]n/[(AgBr)2(n-pica)]n by mechanochemical and thermal properties. The in situ experiments suggest that [(AgBr)(3-pica)]n is kinetically favoured while [(AgBr)2(3-pica)]n is converted into [(AgBr)(3-pica)]n only with a high excess of the ligand. Finally, the liquid nature of the ligands is not sufficient to assist the grinding process, and the complete reaction is observed with the addition of a small quantity of acetonitrile.
KW - Mechanochemistry
KW - Complex
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-594755
DO - https://doi.org/10.1039/d3cp04791a
SN - 1463-9076
SP - 1
EP - 10
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-59475
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Zubia Aranburu, Judith
A1 - Cappella, Brunero
A1 - Zabala Eguren, A.
A1 - Buruaga Lamarain, L.
A1 - Aginagalde Lopez, A.
A1 - Bonse, Jörn
A1 - Schwibbert, Karin
T1 - Quantification of the adhesion force of E. coli on Ti via single-cell force spectroscopy
T2 - Libro de Actas del XL Congreso Anual de la Sociedad Española de Ingeniería Biomédica
N2 - Antibiotic resistance is a growing global problem which poses a massive threat to human health. Although human activity contributes to the acceleration of the process, bacteria have a self-driven stabilisation mechanism to protect themselves from such and other external threats: biofilm formation. Nonetheless, it is the adhesion of a single bacterial cell to a surface that triggers the formation of such network of biomolecules and microorganisms, as well as its hazardous consequences. The main objective of this work was to quantify the adhesion force of a single E. coli cell on a Ti substrate via the AFM-related single-cell force spectroscopy, with both the cell and the substrate material being of high clinical relevance. A set of 25 x 25 force displacement curves was acquired with a maximum force of 3.2 nN without dwell time, yielding a topography map and an adhesion force map that showed to be correlated. A mean adhesion force of 0.85 ± 0.175 nN was measured and the presence of cell appendages on the bacterial cell wall was verified through individual force-displacement curves. Bacterial viability was assessed after the measurements via live/dead staining.
T2 - XL Congreso Anual de la Sociedad Española de Ingeniería Biomédica CASEIB 2022
CY - Valladolid, Spain
DA - 23.11.2022
KW - Bacteria
KW - Atomic force microscopy
KW - Force distance curve
PY - 2022
SN - 978-84-09-45972-8
SP - 217
EP - 220
AN - OPUS4-57039
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zou, T.
A1 - Nonappa, N.
A1 - Khavani, M.
A1 - Vuorte, M.
A1 - Penttilä, P.
A1 - Zitting, A.
A1 - Valle-Delgado, J. J.
A1 - Elert, Anna Maria
A1 - Silbernagl, Dorothee
A1 - Balakshin, M.
A1 - Sammalkorpi, M.
A1 - Österberg, M.
T1 - Experimental and Simulation Study of the Solvent Effects on the Intrinsic Properties of Spherical Lignin Nanoparticles
JF - The journal of physical chemistry. B
N2 - Spherical lignin nanoparticles (LNPs) fabricated via nanoprecipitation of dissolved lignin are among the most attractive biomass-derived nanomaterials. Despite various studies exploring the methods to improve the uniformity of LNPs or seeking more application opportunities for LNPs, little attention has been given to the fundamental aspects of the solvent effects on the intrinsic properties of LNPs. In this study, we employed a variety of experimental techniques and molecular dynamics (MD) simulations to investigate the solvent effects on the intrinsic properties of LNPs. The LNPs were prepared from softwood Kraft lignin (SKL) using the binary solvents of aqueous acetone or aqueous tetrahydrofuran (THF) via nanoprecipitation. The internal morphology, porosity, and mechanical properties of the LNPs were analyzed with electron tomography (ET), small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and intermodulation AFM (ImAFM). We found that aqueous acetone resulted in smaller LNPs with higher uniformity compared to aqueous THF, mainly ascribing to stronger solvent−lignin interactions as suggested by MD simulation results and confirmed with aqueous 1,4-dioxane (DXN) and aqueous dimethyl sulfoxide (DMSO).
More importantly, we report that both LNPs were compact particles with relatively homogeneous density distribution and very low porosity in the internal structure. The stiffness of the particles was independent of the size, and the Young’s modulus was in the range of 0.3−4 GPa. Overall, the fundamental understandings of LNPs gained in this study are essential for the design of LNPs with optimal performance in applications.
KW - Lignin
KW - Electron tomography
KW - Intermodulation AFM
KW - Modulus
KW - SAXS
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546948
DO - https://doi.org/10.1021/acs.jpcb.1c05319
SN - 1520-5207
VL - 125
IS - 44
SP - 12315
EP - 12328
PB - ACS
AN - OPUS4-54694
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zosef, M.
A1 - Fahmy, Alaa
A1 - El Hotaby, W.
A1 - Hassan, A.
A1 - Khalil, A.
A1 - Anis, B.
T1 - High performance graphene-based PVF foam for lead removal from water
JF - Journal of Materials Research and Technology-Jmr&T
N2 - The synthesis and optimization of superior and eco-friendly sorbents for Pb(II) pose a great challenge in the field of water treatment. The sorbent was developed by introducing graphene oxide (GO) into the matrix of polyvinyl formaldehyde (PVF) foam. The immobilization of GO in PVF results in significant increase in the maximum adsorption capacity (Qt) of GO powder for Pb(II), from ≈800 to ≈1730 mg g−1 in the case of GO/PVF foam. As compared with GO powder in Pb(II) aqueous solutions, PVF matrix keeps GO sheets stable without any agglomeration. The large surface area of GO sheet allows the abundant oxygenated functional groups on its surface to participate effectively in the Pb(II) adsorption process, leading to the huge increase of the Qt. Adsorption isotherms and kinetic studies indicated that the sorption process of Pb(II) on GO/PVF was done on heterogenous surface by ion-exchange reaction. The GO/PVF foam showed an excellent reusability for more than 10 cycles with almost the same efficiency and without any significant change in its physical properties.
KW - Water treatment
KW - Graphene oxide
KW - Lead ions
KW - Polyvinyl formaldehyde foam
KW - Superior sorbent
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523013
DO - https://doi.org/10.1016/j.jmrt.2020.08.011
VL - 9
IS - 5
SP - 11861
EP - 11875
PB - Elsevier B.V.
AN - OPUS4-52301
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zorn, R.
A1 - Yin, Huajie
A1 - Lohstroh, W.
A1 - Harrison, W.
A1 - Budd, P.M.
A1 - Pauw, Brian Richard
A1 - Böhning, Martin
A1 - Schönhals, Andreas
T1 - Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity - the Boson peak of PIM-1
JF - Physical Chemistry Chemical Physics
N2 - Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, the vibrational density of states (VDOS) for PIM-1, the prototypical polymer with intrinsic microporosity, is investigated by means of inelastic neutron scattering. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid). The measured data show the characteristic low frequency excess contribution to VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers. For an annealed PIM-1 sample, the Boson peak shifts to higher frequencies in comparison to the un-annealed sample. These changes in the VDOS of the annealed PIM-1 sample are related to changes in the microporous structure as confirmed by X-ray scattering.
KW - Polymers
KW - Boson peak
KW - Neutron scattering
KW - Physical aging
KW - Polymer of intrinsic microporosity
PY - 2018
DO - https://doi.org/10.1039/C7CP07141H
SN - 1463-9076
SN - 1463-9084
VL - 20
IS - 3
SP - 1355
EP - 1363
PB - The Royal Society of Chemistry
AN - OPUS4-43808
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zorn, R.
A1 - Szymoniak, Paulina
A1 - Kolmangadi, Mohamed Aejaz
A1 - Wolf, M.
A1 - Alentiev, D.
A1 - Bermeshev, M.
A1 - Böhning, Martin
A1 - Schönhals, Andreas
T1 - Low frequency vibrational density of state of highly permeable super glassy polynorbornenes – The Boson peak
JF - Physical Chemistry Chemical Physics
N2 - Inelastic incoherent neutron time-of flight scattering was employed to measure the low frequency density of states for a series of addition polynorbornenes with bulky side groups. The rigid main chain in combination with the bulky side groups give rise to a microporosity of these polymers in the solid state. The microporosity characterized by the BET surfaces area varies systematically in the considered series. Such materials have some possible application as active separation layer in gas separation membranes.
All investigated materials show excess contributions to the Debye type density of states characteristic for glasses known as Boson peak. The maximum position of the Boson peak shifts to lower frequency values with increasing microporosity. Data for PIM-1 and Matrimid included for comparison are in good agreement to this dependency. This result supports the sound wave interpretation of the Boson peak.
KW - Polynorbornes
KW - Neutron Scattering
PY - 2020
DO - https://doi.org/10.1039/d0cp03360j
SN - 1463-9076
VL - 22
IS - 33
SP - 18381
EP - 18387
PB - Royal Chemical Society
AN - OPUS4-51165
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zorn, R.
A1 - Szymoniak, Paulina
A1 - Kolmangadi, Mohamed Aejaz
A1 - Malpass-Evans, R.
A1 - McKeown, N.
A1 - Tyagi, M.
A1 - Böhning, Martin
A1 - Schönhals, Andreas
T1 - Low frequency vibrations and diffusion in disordered polymers bearing an intrinsic microporosity as revealed by neutron scattering
JF - Crystals
N2 - The microscopic diffusion and the low frequency density of states (VDOS) of PIM-EATB(CH3) are investigated by inelastic and quasi-elastic neutron scattering where also the demethylated counterpart of PIM-EA-TB(H2) is considered. These intrinsic microporous polymers are characterized by large BET surface area values of several hundred m2/g and pore sizes between 0.5 and 2 nm. Detailed comparison is made to the archetype of polymers of intrinsic microporosity, PIM-1, and polynorbornenes also bearing a microporosity. Due to the wavelength of neutrons, the diffusion and vibrations can be addressed on microscopic length and time scales. From the inelastic neutron scattering experiments the low frequency density of states (VDOS) is estimated which shows excess contributions to the Debye-type VDOS known as Boson peak. It was found that the maximum frequency of the Boson peak decreases with increasing microporosity characterized by the BET surface area. However, besides the BET surface area, additional factors such as the backbone stiffness govern the maximum frequency of the Boson peak. Further the mean squared displacement related to microscopic motions was estimated from elastic fixed window scans. At temperatures above 175 K, the mean squared displacement PIM-EA-TB(CH3) is higher than that for the demethylated counterpart PIM-EA-TB(H2). The additional contribution found for PIM-EATB(CH3) is ascribed to the rotation of the methyl group in this polymer because the only difference between the two structures is that PIM-EA-TB(CH3) has methyl groups where PIM-EA-TB(H2) has none. A detailed comparison of the molecular dynamics is also made to that of PIM-1 and the microporous polynorbornene PTCNSi1. The manuscript focuses on the importance of vibrations and the localized molecular mobility characterized by the microscopic diffusion on the gas Transport in polymeric separation membranes. In the frame of the random gate model localized fluctuations can open or close bottlenecks between pores to enable the diffusion of gas molecules.
KW - Polymer of intrisic microporosity
KW - Neutron scattering
KW - Boson peak
KW - Methyl group rotation
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538490
DO - https://doi.org/10.3390/cryst11121482
VL - 11
IS - 12
SP - 1
EP - 16
PB - MDPI
CY - Basel
AN - OPUS4-53849
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zocca, Andrea
A1 - Müller, Bernd R.
A1 - Laquai, René
A1 - Kupsch, Andreas
A1 - Wieder, Frank
A1 - Benemann, Sigrid
A1 - Wilbig, Janka
A1 - Günster, Jens
A1 - Bruno, Giovanni
T1 - Microstructural characterization of AP40 apatite-wollastonite glass-ceramic
JF - Ceramics international
N2 - The microstructure of an apatite-wollastonite (code name AP40) glass-ceramic is analyzed in this study by combining 2D microscopy, phase analysis, X-ray absorption and synchrotron X-ray refraction computed tomography (XCT and SXRCT, respectively). It is shown that this combination provides a useful toolbox to characterize the global microstructure in a wide scale range, from sub-micrometer to millimeter. The material displays a complex microstructure comprising a glassy matrix with embedded fluorapatite and wollastonite small crystals. In this matrix, large (up to 200 μm) spike-shaped structures are distributed. Such microstructural features are oriented around a central sphere, thereby forming a structure resembling a sea urchin. A unique feature of SXRCT, in contrast to XCT, is that internal interfaces are visualized; this allows one to show the 3D distribution of these urchins with exceptionally good contrast. Furthermore, it is revealed that the spike-shaped structures are not single crystals, but rather composed of sub-micrometric crystals, which are identified as fluorapatite and diopside phases by SEM-EDX analysis.
KW - Glass-ceramic
KW - X-ray refraction
KW - Computed tomography
KW - Microstructure
PY - 2023
DO - https://doi.org/10.1016/j.ceramint.2022.12.130
SN - 0272-8842
VL - 49
IS - 8
SP - 12672
EP - 12679
PB - Elsevier Science
CY - Amsterdam
AN - OPUS4-57452
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zhang, X.
A1 - Zhang, J.
A1 - Wang, H.
A1 - Rogal, J:
A1 - Li, H.-Y.
A1 - Wei, S.-H.
A1 - Hickel, Tilmann
T1 - Defect-characterized phase transition kinetics
JF - Applied physics reviews
N2 - Phase transitions are a common phenomenon in condensed matter and act as a critical degree of freedom that can be employed to tailor the mechanical or electronic properties of materials. Understanding the fundamental mechanisms of the thermodynamics and kinetics of phase transitions is, thus, at the core of modern materials design. Conventionally, studies of phase transitions have, to a large extent, focused on pristine bulk phases. However, realistic materials exist in a complex form; their microstructures consist of different point and extended defects. The presence of defects impacts the thermodynamics and kinetics of phase transitions, but has been commonly ignored or treated separately. In recent years, with the significant advances in theoretical and experimental techniques, there has been an increasing research interest in modeling and characterizing how defects impact or even dictate phase transitions. The present review systematically discusses the recent progress in understanding the kinetics of defect-characterized phase transitions, derives the key mechanisms underlying these phase transitions, and envisions the remaining challenges and fruitful research directions. We hope that these discussions and insights will help to inspire future research and development in the field.
KW - Kinetics
KW - Atomistic models
KW - Phase transitions
KW - Defects
PY - 2022
DO - https://doi.org/10.1063/5.0117234
SN - 1931-9401
VL - 9
IS - 4
SP - 1
EP - 42
PB - AIP
CY - New York, NY
AN - OPUS4-56507
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zhang, Kun
A1 - Carrod, Andrew J.
A1 - Del Giorgio, Elena
A1 - Hughes, Joseph
A1 - Rurack, Knut
A1 - Bennet, Francesca
A1 - Hodoroaba, Vasile-Dan
A1 - Harrad, Stuart
A1 - Pikramenou, Zoe
T1 - Luminescence Lifetime-Based Sensing Platform Based on Cyclometalated Iridium(III) Complexes for the Detection of Perfluorooctanoic Acid in Aqueous Samples
JF - Analytical Chemistry
N2 - Luminescence lifetimes are an attractive analytical method for detection due to its high sensitivity and stability. Iridium probes exhibit luminescence with long excited-state lifetimes, which are sensitive to the local environment. Perfluorooctanoic acid (PFOA) is listed as a chemical of high concern regarding its toxicity and is classified as a “forever chemical”. In addition to strict limits on the presence of PFOA in drinking water, environmental contamination from industrial effluent or chemical spills requires rapid, simple, accurate, and cost-effective analysis in order to aid containment. Herein, we report the fabrication and function of a novel and facile luminescence sensor for PFOA based on iridium modified on gold surfaces. These surfaces were modified with lipophilic iridium complexes bearing alkyl chains, namely, IrC6 and IrC12, and Zonyl-FSA surfactant. Upon addition of PFOA, the modified surfaces IrC6-FSA@Au and IrC12-FSA @Au show the largest change in the red luminescence signal with changes in the luminescence lifetime that allow monitoring of PFOA concentrations in aqueous solutions. The platform was tested for the measurement of PFOA in aqueous samples spiked with known concentrations of PFOA and demonstrated the capacity to determine PFOA at concentrations >100 μg/L (240 nM).
KW - Perfluorooctanoic Acid (PFOA)
KW - Cyclometalated iridium (III) complexes
KW - Luminescent lifetime
KW - Optically active surfaces
KW - ToF-SIMS
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-594535
UR - https://pubs.acs.org/doi/10.1021/acs.analchem.3c04289
DO - https://doi.org/10.1021/acs.analchem.3c04289
VL - 96
IS - 4
SP - 1565
EP - 1575
PB - American Chemical Society (ACS)
AN - OPUS4-59453
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zauer, M.
A1 - Prinz, Carsten
A1 - Adolphs, J.
A1 - Emmerling, Franziska
A1 - Wagenführ, A.
T1 - Sorption surfaces and energies of untreated and thermally modified wood evaluated by means of excess surface work (ESW)
JF - Wood Science and Technology
N2 - Water vapor sorption surface areas and sorption energies of untreated
and thermally modified Norway spruce [Picea abies (L.) Karst.], sycamore maple (Acer pseudoplatanus L.) and European ash (Fraxinus excelcior L.) were investigated by means of dynamic vapor sorption (DVS) measurements and excess surface work (ESW) evaluation method, respectively. Adsorption and desorption experiments in the hygroscopic range and desorption tests from water saturation were conducted.
Thermodynamically, ESW is the sum of the surface free energy and the isothermal isobaric work of sorption. From the amount adsorbed in the first Minimum a specific surface area similar to the BET surface area can be obtained. The results show that untreated spruce has a significantly higher specific water vapor Sorption surface and sorption energy compared to both hardwoods maple and ash. Thermal modification of the woods leads to a significant reduction of water vapor Sorption surface and sorption energy. The determined surface area and energy are higher in desorption direction than in adsorption direction, whereby the highest values in Desorption direction from water saturation, especially for maple and ash, were obtained.
The surface areas calculated by means of the ESW method are similar to the surface areas calculated by means of the BET method, particularly in adsorption direction.
KW - Excess surface work
KW - Dynamic vapor sorption
KW - Wood
KW - BET
PY - 2018
DO - https://doi.org/10.1007/s00226-018-1021-2
SN - 1432-5225
SN - 0043-7719
VL - 52
IS - 4
SP - 957
EP - 969
PB - Springer
CY - Berlin Heidelberg
AN - OPUS4-44975
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zarinwall, A.
A1 - Waniek, Tassilo
A1 - Saadat, R.
A1 - Braun, U.
A1 - Sturm, Heinz
A1 - Garnweitner, G.
T1 - Comprehensive Characterization of APTES Surface Modifications of Hydrous Boehmite Nanoparticles
JF - Langmuir
N2 - Hydrous boehmite (γ-AlOOH) nanoparticles (BNP) show great potential as nanoscale filler for the fabrication of fiber reinforced nanocomposite materials. Notably, the particle−matrix interaction has been demonstrated to be decisive for improving the matrix-dominant mechanical properties in the past years. Tailoring the surface properties of the nanofiller enables to selectively design the interaction and thus to exploit the benefits of the nanocomposite in an optimal way. Here, an extensive study is presented on the binding of (3-aminopropyl)triethoxysilane (APTES), a common silane surface modifier, on BNP in correlation to different process parameters (concentration, time, temperature, and pH). Furthermore, a comprehensive characterization of the modified BNP was performed by using elemental analysis (EA), thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA-MS), and Kaiser’s test (KT). The results show an increasing monolayer formation up to a complete surface coverage with rising APTES concentration, time, and temperature, resulting in a maximal grafting density of 1.3 molecules/nm². Unspecific multilayer formation was solely observed under acidic conditions. Comparison of TGA-MS results with data recorded from EA, TGA, and KT verified that TGA-MS is a convenient and highly suitable method to elucidate the ligand binding in detail.
KW - Boehmite
KW - Nanoparticle
KW - Surface
KW - APTES
KW - Functionalization
KW - BET
KW - TGA
KW - Grafting
KW - Nanocomposite
KW - Silane
PY - 2020
DO - https://doi.org/10.1021/acs.langmuir.0c02682
VL - 37
IS - 1
SP - 171
EP - 179
PB - ACS Publications
AN - OPUS4-51954
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CHAP
A1 - Zarinwall, A.
A1 - Waniek, Tassilo
A1 - Finke, B.
A1 - Sadaat, R.
A1 - Sturm, Heinz
A1 - Garnweitner, G.
ED - Sinapius, M.
ED - Ziegmann, G.
T1 - Particle Surface Modification
T2 - Acting Principles of Nano-Scaled Matrix Additives for Composite Structures
N2 - Whilst a decisive role of the particle-matrix interphase on the mechanical properties of nanoparticle-filled polymers has been demonstrated in the last years, the arbitrary design of this interphase remains a very challenging goal. In principle, this could be realized via an appropriate surfacemodification of the nanofiller prior to its incorporation in the polymer. For most systems, such as for boehmite nanofillers, however, the interaction of organic modifiers with the particle surface has not been studied in detail, and only single studies are known rather than systematic investiga- tions on the effects of different chemical functions anchored on the particle surface. In this chapter, we present an extensive study on the binding of APTES, a common silane surface modifier, with boehmite, and show that thermogravimetric analysis (TGA) coupled with mass spectrometry (MS) is a convenient and highly suitable method to elucidate the ligand binding in detail. Furthermore, a two-step coupling strategy is presented, demonstrating that based on APTES anchored to the parti- cle surface, the condensation of various carboxylic acids can be utilized to enable highly diverse chemical properties of the nanofillers, which leads to very different particle-matrix interactions in the nanocomposites.
KW - APTES
KW - Boehmite
KW - Nanoparticle
KW - TGA-MS
PY - 2021
SN - 978-3-030-68522-5
SN - 978-3-030-68523-2
DO - https://doi.org/10.1007/978-3-030-68523-2
SN - 2194-8240
SN - 2194-8259
SP - 119
EP - 142
PB - Springer Nature Switzerland AG
CY - Cham
AN - OPUS4-53727
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Zvereva, V.
A1 - Martynova, S.
A1 - Asanov, I.
A1 - La Fontaine, C.
A1 - Roudenko, O.
A1 - Gubanov, A.
A1 - Plyusnin, P.
A1 - Korenev, S.
A1 - Asanova, T.
T1 - Insight of the thermal decomposition of ammonium hexahalogenoiridates(IV) and hexachloroiridate(III)
JF - PCCP
N2 - Thermal decomposition of (NH4)3[IrCl6]·H2O, (NH4)2[IrCl6] and (NH4)2[IrBr6] in reductive and inert atmospheres has been investigated in situ using quick-EXAFS and temperature-resolved powder X-ray diffraction. For the first time, (NH4)2[Ir(NH3)Cl5] and (NH4)2[Ir(NH3)Br5] have been proven as intermediates of thermal decomposition of (NH4)3[IrCl6]·H2O, (NH4)2[IrCl6] and (NH4)2[IrBr6]. Thermal degradation of (NH4)2[IrCl6] and (NH4)2[IrBr6] is a more complex process as suggested previously and includes simultaneous formation of (NH4)2[Ir(NH3)Cl5] and (NH4)2[Ir(NH3)Br5] intermediates mixed with metallic iridium. In the inert atmosphere, complexes (NH4)[Ir(NH3)2Cl4] and (NH4)[Ir(NH3)2Br4] as well as [Ir(NH3)3Br3] were proposed as possible intermediates before formation of metallic iridium particles
KW - Thermal decomposition
KW - Iridium compounds
KW - EXAFS
KW - In situ PXRD
PY - 2020
DO - https://doi.org/10.1039/D0CP02743J
VL - 22
IS - 40
SP - 22923
EP - 22934
AN - OPUS4-51224
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Sukhikh, A.
A1 - Kraus, Werner
A1 - Gromilov, S.
T1 - Synthesis and Crystal Chemistry of Octahedral Rhodium(III) Chloroamines
JF - Molecules
N2 - Rhodium(III) octahedral complexes with amine and chloride ligands are the most common starting compounds for preparing catalytically active rhodium(I) and rhodium(III) species. Despite intensive study during the last 100 years, synthesis and crystal structures of rhodium(III) complexes were described only briefly. Some [RhClx(NH3)6-x] compounds are still unknown. In this study, available information about synthetic protocols and the crystal structures of possible [RhClx(NH3)6−x] octahedral species are summarized and critically analyzed. Unknown crystal structuresof(NH4)2[Rh(NH3)Cl5],trans–[Rh(NH3)4Cl2]Cl·H2O,andcis–[Rh(NH3)4Cl2]Clarereported based on high quality single crystal X-ray diffraction data. The crystal structure of [Rh(NH3)5Cl]Cl2 was redetermined. All available crystal structures with octahedral complexes [RhClx(NH3)6-x] were analyzed in terms of their packings and pseudo-translational sublattices. Pseudo-translation lattices suggest face-centered cubic and hexagonal closed-packed sub-cells, where Rh atoms occupy nearly ideal lattices.
KW - Pseudo-translationalsublattices
KW - Rhodiumcomplexes
KW - Ligandsubstitution
KW - Crystalstructure
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508194
DO - https://doi.org/10.3390/molecules25040768
VL - 25
IS - 4
SP - 768
PB - MDPI
CY - Basel
AN - OPUS4-50819
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Spektor, K.
A1 - Khandarkhaeva, S.
A1 - Fedotenko, T.
A1 - Pakhomova, A.
A1 - Kupenko, I.
A1 - Rohrbach, A.
A1 - Klemme, S.
A1 - Crichton, W. A.
A1 - Dyachkova, T. V.
A1 - Tyutyunnik, A. P.
A1 - Zainulin, Y. G.
A1 - Gramilov, S. A.
A1 - Dubrovinsky, L. S.
T1 - Decomposition of single-source precursors under high-temperature highpressure to access osmium–platinum refractory alloys
JF - Journal of alloys compounds
N2 - Thermal decomposition of (NH4)2[OsxPt1-xCl6] as single-source precursors for Os-Pt binary alloys has been investigated under ambient and high pressure up to 40 GPa. Thermal decomposition of mixed-metal (NH4)2[OsxPt1-xCl6] precursor in hydrogen atmosphere (reductive environment) under ambient pressure results in formation of β-trans[Pt(NH3)2Cl2] and α-trans-[Pt(NH3)2Cl2] crystalline intermediates as well as single and twophase Os—Pt binary alloys. For the first time, direct thermal decomposition of coordination compound under pressure has been investigated. A formation of pure metallic alloys from single-source precursors under pressure has been shown. Miscibility between fcc- and hcpstructured alloys has been probed up to 50 GPa by in situ high-pressure X-ray diffraction. Miscibility gap between fcc- and hcp-structured alloys does not change its positions with pressure up to at least 50 GPa.
KW - High-pressure high-temperature
KW - Osmium
KW - Platinum
KW - Phase diagrams
KW - Alloys
KW - Single-source precursors
PY - 2020
DO - https://doi.org/10.1016/j.jallcom.2019.152121
VL - 813
SP - 152121
PB - Elsevier
AN - OPUS4-50019
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yusenko, Kirill
A1 - Smekhova, A.
A1 - Kuzmin, A.
T1 - Extended X-Ray absorption fine structure (exafs) to study local constitution of high-entropy alloys
N2 - Modern design of superior multi-functional alloys composed of several principal components requires in-depth studies of their local structure for developing desired macroscopic properties. Herein, peculiarities of atomic arrangements on the local scale and electronic states of constituent elements in the single-phase face-centered cubic (fcc)- and body-centered cubic (bcc)-structured high-entropy Alx-CrFeCoNi alloys (x = 0.3 and 3, respectively) are explored by element-specific X-ray absorption spectroscopy in hard and soft X-ray energy ranges. Simulations based on the reverse Monte Carlo approach allow to perform a simultaneous fit of extended X-ray absorption fine structure spectra recorded at K absorption edges of each 3d constituent and to reconstruct the local environment within the first coordination shells of absorbers with high precision.
T2 - SPP2006: ordering in high-entropy alloys
CY - Online meeting
DA - 05.10.2021
KW - EXAFS
KW - High-entropy alloys
PY - 2021
AN - OPUS4-54015
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Petrushina, M.
A1 - Dedova, E.
A1 - Portnaygin, A.
A1 - Papynov, E.
A1 - Filatov, E.
A1 - Korenev, S.
A1 - Gubanov, A.
T1 - Effect of temperature and pressure on mixed oxide solid solutions
JF - Inorganic Chemistry Communication
N2 - A hydrothermal synthesis of ZrW2-xMoxO8 (0 ≤ x ≤ 2) from the corresponding precursors is reported in this paper. High-temperature and high-pressure data are presented for the sample with x = 1.6. An increase in temperature initiates the phase transition from tetragonal precursor to orthorhombic-ZrW2-xMoxO8 (x = 1.6) with the subsequent formation of cubic and trigonal phases. The thermolysis parameter of the disordered cubic ZrW2-xMoxO8 (x = 1.6) phase is 803 K, and the coefficient of thermal expansion is α = -4.6∙10–6 K−1. Data on ZrW2-xMoxO8 (x = 1.6) structure as a function of pressure are obtained for the first time. Pressureinduced changes from cubic to orthorhombic ZrW2-xMoxO8 (x = 1.6) phase at 1.38 GPa are observed. The sample amorphization is irreversible during decompression.
KW - Phase transition
KW - High-pressure
KW - Complex oxides
PY - 2020
DO - https://doi.org/10.1016/j.inoche.2020.107965
VL - 117
SP - 107965
PB - Elsevier B.V.
AN - OPUS4-50821
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Petrushina, M.
A1 - Dedova, E.
A1 - Portnaygin, A.
A1 - Papynov, E.
A1 - Filatov, E.
A1 - Gubanov, A.
T1 - Pressure induced change in the ZrWMoO8
JF - MaterialsTodayProceedings
N2 - In this paper we report high-pressure synchrotron x-ray powder diffraction data for the cubic ZrWMoO8. For the first time, extensive structural study of ZrWMoO8 solid solution as a function of pressure was performed. This study shows that disordered cubic-ZrWMoO8 (space group Pa) transforms to ordered cubic-ZrWMoO8 (space group P) at low pressure. A further high-pressure influence leads followed by amorphization of the sample at 2.2 GPa. All transformations are irreversible. Our work will have high impact in the design of new composite materials with well-defined thermal expansion, especially for applications under extreme conditions and high mechanic stress.
KW - Phase transition
KW - High-pressure
KW - Complex oxides
PY - 2020
DO - https://doi.org/10.1016/j.matpr.2019.12.141
VL - 25
IS - 3
SP - 428
EP - 430
PB - Elsevier Ltd.
AN - OPUS4-50822
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Khandarkhaeva, S.
A1 - Bykov, M.
A1 - Fedotenko, T.
A1 - Hanfland, M.
A1 - Sukhikh, A.
A1 - Gromilov, S.
A1 - Dubrovinsky, L.
T1 - Face-centered cubic refractory alloys prepared from single-source precursors
JF - Material
N2 - Three binary fcc-structured alloys (fcc–Ir0.50Pt0.50, fcc Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50) were 14 prepared from [Ir(NH3)5Cl][PtCl6], [Ir(NH3)5Cl][PtBr6], [Rh(NH3)5Cl]2[PtCl6]Cl2 and 15 [Rh(NH3)5Cl][PdCl4]·H2O, respectively, as single-source precursors. All alloys were prepared by 16 thermal decomposition in gaseous hydrogen flow below 800 °C. Fcc–Ir0.50Pt0.50 and fcc–Rh0.50Pd0.50 17 correspond to miscibility gaps on binary metallic phase diagrams and can be considered as 18 metastable alloys. Detailed comparison of [Ir(NH3)5Cl][PtCl6] and [Ir(NH3)5Cl][PtBr6] crystal 19 structures suggests that two isoformular salts are not isostructural. In [Ir(NH3)5Cl][PtBr6], specific 20 Br…Br interactions are responsible for crystal structure arrangement. Room temperature 21 compressibility of fcc–Ir0.50Pt0.50, fcc–Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50 has been investigated up to 50 GPa 22 in diamond anvil cells. All investigated fcc-structured binary alloys are stable under compression. 23 Atomic volumes and bulk moduli show good agreement with ideal solutions model. For fcc–24 Ir0.50Pt0.50, V0/Z = 14.597(6) Å3·atom-1, B0 = 321(6) GPa, B0' = 6(1); for fcc–Rh0.66Pt0.33, V0/Z = 14.211(3) 25 Å3·atom-1, B0 =259(1) GPa, B0' = 6.66(9); for fcc–Rh0.50Pd0.50, V0/Z = 14.18(2) Å3·atom-1, B0 =223(4) GPa, 26 B0' = 5.0(3).
KW - High-pressure
KW - Refractory alloys
KW - Platinum group metals
KW - Single-source precursors
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508176
DO - https://doi.org/10.3390/ma13061418
VL - 13
IS - 6
SP - 1418
PB - MDPI
CY - Basel
AN - OPUS4-50817
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Kabelitz, Anke
A1 - Schokel, Alexander
A1 - Wagner, Ralf
A1 - Prinz, Carsten
A1 - Kemnitz, E
A1 - Emmerling, Franziska
A1 - Krahl, Thoralf
A1 - de Oliveira Guilherme Buzanich, Ana
T1 - Local Structure of Europium-Doped Luminescent Strontium Fluoride Nanoparticles: Comparative X-ray Absorption Spectroscopy and Diffraction Study
JF - ChemNanoMat
N2 - Rare-earth based luminescent materials are key functional components for the rational design of light-conversion smart devices. Stable Eu3+-doped strontium fluoride (SrF2) nanoparticles were prepared at room temperature in ethylene glycol. Their luminescence depends on the Eu content and changes after heat treatment. The crystallinity of heat-treated material increases in comparison with as-synthesized samples. Particles were investigated in solution using X-ray diffraction, small-angle X-ray scattering, and X-ray spectroscopy. After heat treatment, the size of the disordered nanoparticles increases together with a change of their local structure. Interstitial fluoride ions can be localized near Eu3+ ions. Therefore, non-radiative relaxation from other mechanisms is decreased. Knowledge about the cation distribution is key information for understanding the luminescence properties of any material.
KW - SrF2
KW - EXAFS
KW - Eu
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-540094
DO - https://doi.org/10.1002/cnma.202100281
VL - 7
IS - 11
SP - 1221
EP - 1229
PB - Wiley Online Library
AN - OPUS4-54009
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yusenko, Kirill
A1 - Emmerling, Franziska
A1 - de Oliveira Guilherme Buzanich, Ana
T1 - X-Ray absorption spectroscopy to study multicomponent materials
N2 - Detailed study of multicomponent systems in solid-state as well as in solution using X-ray diffraction and X-ray spectroscopy is one of the most common topics in modern materials chemistry. 5-6 component high-entropy alloys such as fcc- and bcc-structured AlxCoCrFeNi and fluorescent nanoparticles based on fluorite-structured SrF2 doped by rare-earth metals in organic solutions have high complexity and their local structure cannot be resolved using only diffraction. X-ray absorption spectroscopy should be applied to understand peculiarities in their local structure and make a link between structure on short and long ranges and their macroscopic properties. Here, based on two representativee examples, we discuss how a combination of several X-ray absorption edges might give new insights into complex materials.
T2 - Virtual meeting of the African Light Source
CY - Online meeting
DA - 15.11.2021
KW - EXAFS
KW - Synchrotron studies
PY - 2021
AN - OPUS4-54014
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yusenko, Kirill
A1 - Domonov, D.
A1 - Pechenyuk, S.
A1 - Belyevskii, A.
T1 - Formation of Nanostructured Carbon from [Ni(NH3)6]3[Fe(CN)6]2
JF - Nanomaterials
N2 - The products of thermal decomposition in an argon atmosphere of [Ni(NH3)6]3[Fe(CN)6]2 as a precursor has been studied. Decomposition products were studied up to 800◦C. Above 600◦C, all coordination bonds in the residues are broken with a formation of Ni3Fe, Fe, and free carbon with a small admixture of nitrogen. Elementary carbon can be easily separated from metals by treatment with a water solution of hydrochloric acid. Only carbon is responsible for the specific surface of the composite products. The released carbon has a high degree of graphitization and begins to oxidize in air above 500°C and is completely oxidized above 700°C.
KW - Carbon materials
KW - Double complex compound
KW - Thermal decomposition
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508188
DO - https://doi.org/10.3390/nano10020389
VL - 10
IS - 2
SP - 389
PB - MDPI
CY - Basel
AN - OPUS4-50818
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yusenko, Kirill
A1 - de Oliveira Guilherme Buzanich, Ana
A1 - Radtke, Martin
T1 - Studies of high-entropy alloys using x-ray absorption fine structure at the bamline
N2 - BAM line is multipurpose high-energy beamline. To extend studies of multicomponent alloys using EXAFS we perform own research and user experiments requiring multiedge spectroscopy, high-temperature and chemically aggressive sample environments. Our study of multicomponent alloys and high-entropy alloys open new perspectives in understanding their reactivity, corrosion, phase transformations and local ordering.
T2 - SPP2006: large scale facilities
CY - Online meeting
DA - 02.11.2021
KW - Synchrotron studies
KW - High-entropy alloys
KW - EXAFS
PY - 2021
AN - OPUS4-54016
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yusenko, Kirill
T1 - Single-source precursors strategy to access refractory high-entropy alloys for electrocatalytic applications
N2 - High-entropy alloys containing up to 6 platinum group metals can be prepared by thermal decomposition of single-source precursors non requiring high temperature. We prepare the first example of a single-phase hexagonal high-entropy alloy. Heat treat- ment up to 1500 K and compression up to 45 GPa do not result in phase changes, a record temperature and pres- sure stability for a single-phase high-entropy alloy. The alloys show pronounced electrocatalytic activity in methanol oxidation, which opens a route for the use of high-entropy alloys as materials for sustainable energy conversion.
T2 - HEA2020: first international virtual workshop on high-entropy alloy and complex solid solution nanoparticles for electrocatalysis
CY - Online meeting
DA - 06.10.2020
KW - High-entropy alloys
KW - Single-source precursors
PY - 2020
AN - OPUS4-54013
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yusenko, Kirill
A1 - de Oliveira Guilherme Buzanich, Ana
A1 - Radtke, Martin
A1 - Reinholz, Uwe
A1 - Riesemeier, Heinrich
A1 - Emmerling, Franziska
T1 - BAMline 2.0 – further technical developments for a broader multipurpose hard X-ray beamline at BESSY II
N2 - We show further development of our beamline in the contexst of further itermational collaboration.
T2 - PACC and AfSC
CY - Accra, Ghana
DA - 28.01.2019
KW - Synchrotron radiation
PY - 2019
AN - OPUS4-47317
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yusenko, Kirill
T1 - Reaction of high-entropy alloys with hydrogen under extreme conditions
N2 - In the current study, we investigate an interaction under high-pressure high-temperature of single phase fcc-, hcp- and bcc-structured high-entropy alloys with hydrogen, carbon and nitrogen to obtain high-entropy hydrides, carbides and nitrides. Structural changes in high-entropy alloys upon compression and heating in the presence of these light elements are in the focus of our investigation. An easy route to high-entropy hydrides, carbides and nitrides will open new synthetic horizons in compositionally complex materials. Our study suggests that high-entropy alloys form high- entropy hydrides mainly with a composition close to M:H 1:1 ratio. Hydrides can be obtained under compression with hydrogen as a pressure compression medium or using hydrogen fluid as reactive agent.
T2 - Intermetallics 2023
CY - Bad Staffelstein, Germany
DA - 03.10.2023
KW - HEA
PY - 2023
AN - OPUS4-58555
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - You, Zengchao
A1 - Nirmalananthan-Budau, Nithiya
A1 - Resch-Genger, Ute
A1 - Panne, Ulrich
A1 - Weidner, Steffen
T1 - Separation of polystyrene nanoparticles bearing different carboxyl group densities and functional groups quantification with capillary electrophoresis and asymmetrical flow field flow fractionation
JF - Journal of Chromatography A
N2 - Two sets of polystyrene nanoparticles (PSNPs) with comparable core sizes but different carboxyl group densities were made and separated using asymmetric flow field flow fractionation (AF4), capillary electrophoresis (CE), and the off-line hyphenation of both methods. Our results revealed the significant potential of two-dimensional off-line AF4-CE hyphenation to improve the separation and demonstrated for the first time, the applicability of CE to determine the functional group density of nanoparticles (NPs). Compared to the result acquired with conductometric titration, the result obtained with synthesized 100 nm sized PSNPs revealed only a slight deviation of 1.7%. Commercial 100 nm sized PSNPs yielded a deviation of 4.6 %. For 60 nm sized PSNPs, a larger deviation of 10.6 % between both methods was observed, which is attributed to the lower separation resolution.
KW - Nanoparticle
KW - A4F
KW - Capillary electrophoresis
KW - Carboxyl group
PY - 2020
DO - https://doi.org/10.1016/j.chroma.2020.461392
VL - 1626
SP - 461392
PB - Elsevier B.V.
AN - OPUS4-51080
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yin, Huajie
A1 - Chua, Y. Z.
A1 - Yang, B.
A1 - Schick, C.
A1 - Harrison, W.
A1 - Budd, P.
A1 - Böhning, Martin
A1 - Schönhals, Andreas
T1 - First clear cut experimental evidence for a glass transition in a polymer with intrinsic microporosity: PIM-1
JF - Journal Physical Chemistry Letters
N2 - Polymers with intrinsic microporosity (PIMs) represent a novel, innovative class of materials with great potential in various applications from high-performance gas separation membranes to electronic devices. Here for the first time, for PIM-1, as the archetypal PIM, fast scanning calorimetry provides definitive evidence for a glass transition (Tg=715 K, heating rate 3·10^4 K/s) by decoupling the time-scales responsible for glass transition and decomposition. As the rigid molecular structure of PIM-1 prevents any conformational changes, small-scale bend and flex fluctuations must be considered the origin of its glass transition. This result has strong implications for the fundamental understanding of the glass transition and for the physical aging of PIMs and other complex polymers, both topical problems of materials science.
KW - Polymers with intrinsic microporosity
KW - Fast Scanning Calorimetry
PY - 2018
DO - https://doi.org/10.1021/acs.jpclett.8b00422
SN - 1948-7185
VL - 9
IS - 8
SP - 2003
EP - 2008
PB - ACS
AN - OPUS4-44683
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yin, Huajie
A1 - Chapala, P.
A1 - Bermeshev, M.
A1 - Pauw, Brian Richard
A1 - Schönhals, Andreas
A1 - Böhning, Martin
T1 - Influence of Trimethylsilyl Side Groups on the Molecular Mobility and Charge Transport in Highly Permeable Glassy Polynorbornenes
JF - ACS Applied Polymer Materials
N2 - Superglassy polymers with a large fractional free volume have emerged as novel materials with a broad range of applications, especially in the field of membrane separations. Highly permeable addition-type substituted polynorbornenes with high thermal resistance and chemical stability are among the most promising materials. The major obstacle for extending the practical membrane application is their strong tendency to physical aging, leading to a partial decline in their superior transport performance over time. In the present study, broadband dielectric spectroscopy with complementary X-ray scattering techniques were employed to reveal changes in microporous structure, molecular mobility, and conductivity by systematic
comparison of two polynorbornenes with different numbers of trimethylsilyl side groups. Their response upon heating (aging) was compared in terms of structure, dynamics, and charge transport behavior. Furthermore, a detailed analysis of the observed
Maxwell−Wagner−Sillars polarization at internal interfaces provides unique information about the microporous structure in the
solid films. The knowledge obtained from the experiments will guide and unlock potential in synthesizing addition-type polynorbornenes with versatile properties.
KW - Dielectric spectroscopy
KW - Molecular mobility
KW - Electrical conductivity
KW - Gas separation membranes
PY - 2019
DO - https://doi.org/10.1021/acsapm.9b00092
SN - 2637-6105
VL - 1
IS - 4
SP - 844
EP - 855
PB - ACS
CY - Washington DC
AN - OPUS4-47838
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yin, Huajie
A1 - B, Yang
A1 - Chua, Y. Z.
A1 - Szymoniak, Paulina
A1 - Carta, M
A1 - Malpass-Evans, R
A1 - McKeown, N
A1 - Harrison, W
A1 - Budd, P
A1 - Schick, C
A1 - Böhning, Martin
A1 - Schönhals, Andreas
T1 - Effect of backbone rigidity on the glass transition of polymers of in-trinsic microporosity probed by fast scanning calorimetry
JF - ACS Macro letters
N2 - Polymers of Intrinsic Microporosity (PIMs) of high performance have developed as materials with a wide application range in gas separation and other energy-related fields. Further optimization and long-term behavior of devices with PIMs require an understanding of the structure-property relationships including physical aging. In this context the glass transi-tion plays a central role, but with conventional thermal analysis a glass transition is usually not detectable for PIMs be-fore their thermal decomposition. Fast scanning calorimetry provides evidence of the glass transition for a series of PIMs, as the time scales responsible for thermal degradation and for the glass transition are decoupled by employing ultrafast heating rates of tens of thousands K s-1. The investigated PIMs were chosen considering the chain rigidity. The estimated glass transition temperatures follow the order of the rigidity of the backbone of the PIMs.
KW - Polymers of intrinsic microporosity
KW - Fast scanning calormetry
PY - 2019
DO - https://doi.org/10.1021/acsmacrolett.9b00482
SN - 2161-1653
VL - 8
IS - 8
SP - 1022
EP - 1028
PB - ACS Publications
AN - OPUS4-48617
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yin, Huajie
A1 - Schönhals, Andreas
A1 - Böhning, Martin
T1 - Molecular Mobility and Charge Transport in Polymers of Intrinsic Microporosity (PIMs) as Revealed by Dielectric Spectroscopy
N2 - Polymeric membranes represent a low-cost, energy efficient solution for gas separation. Recently polymers of intrinsic microporosity (PIMs) have emerged as prestigious membrane materials featuring a large concentration of pores smaller than 1 nm, a BET surface area larger than 700 m2/g and high gas permeability and selectivity. Unusual chain structure combining rigid segments with sites of contortion gives rise to the intrinsic microporosity. However, this novel class of glassy polymers are prone to pronounced physical aging. The initial microporous structures approach a denser state via local small scale fluctuataions, leading to a dramatic reduction in the gas permeabilities. For the first time, dielectric relaxation spectroscopy with state-of-the-art high-resolution analyzers was employed to investigate three representative PIMs with a systematic change in chain rigidity: PIM-EA-TB 〉 PIM-1 〉 PIM-MDPH-TB. The molecular mobility, the charge transport and their response upon heating (aging) in the polymers were measured in a broad temperature range through isothermal frequency scans during different heating / cooling cycles. Multiple dielectric processes following Arrhenius behavior were observed for the investigated polymers. Local fluctuations, Maxwell-Wagner-Sillars (MWS) polarization and structural relaxation phenomena were discussed and attempted to be correlated with the structural features of PIMs. Moreover, all PIMs showed conductivity in the glassy state. The significant increase in the conductivity with increasing temperature far below the glass transition temperature of PIMs is explained in terms of the loosely packed microporous structure and the formation of local intermolecular agglomerates due to interaction of π-electrons in aromatic moieties of the polymer backbone.
T2 - American Chemical Society (ACS) National Meeting & Expo 2019
CY - Orlando, FL, USA
DA - 31.03.2019
KW - Dielectric spectroscopy
KW - Polymeric membrane
KW - Polymers of intrinsic microporosity
PY - 2019
AN - OPUS4-47805
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yin, Huajie
A1 - Chua, Y. Z.
A1 - Yang, B.
A1 - Schick, C.
A1 - Böhning, Martin
A1 - Schönhals, Andreas
T1 - Probing the glass transition temperature of polymers of intrinsic microporosity (PIMs) by fast scanning calorimeter
N2 - High performance polymers of intrinsic microporosity (PIMs) have emerged as novel materials with broad applications from gas separation to electronic devices. Sufficiently rigid, even contorted polymer chains show only limited molecular mobility, therefore undergo inefficient packing and give rise to intrinsic microporosity with pore size generally smaller than 1 nm and BET surface areas larger than 700 m2/g. Further performance optimization and long-term stability of devices incorporating PIMs rely on our understanding of structure-processing-property relationships and physical aging, in which glass transition plays a key role. Up to now no glass transition temperature (Tg) of PIMs could be detected with conventional thermal analysis techniques before degradation. Decoupling the time scales responsible for the glass transition and the thermal decomposition is a reliable strategy to overcome this. This was achieved by employing fast scanning calorimetry (FSC) based on a chip sensor, which is capable to heat and cool a small sample (ng-range) with ultrafast rates of several ten thousand K/s. FSC provides definitive evidence of glass transition of a series of PIMs with a special consideration on the chain rigidity. The determined glass transition temperature of these PIMs follows the order of the rigidity of their backbone structures. FSC provides the first clear-cut experimental evidence of the glass transition of PIM-EA-TB with a Tg of 663 K, PIM-1 of 644 K and PIM-DMDPH-TB of 630 K at a heating rate of 1Χ104 K/s. Local fluctuations are featured in glass transition of highly rigid PIMs. As conformational changes are prevented by the backbone rigidity, the glass transition must rather be assigned to local small scale fluctuations.
T2 - American Chemical Society (ACS) National Meeting & Expo 2019
CY - Orlando, FL, USA
DA - 31.03.2019
KW - Glass transition
KW - Polymers of intrinsic microporosity
KW - Fast scanning calorimeter
PY - 2019
AN - OPUS4-47806
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yildirim, Arda
A1 - Szymoniak, Paulina
A1 - Sentker, K.
A1 - Butschies, M.
A1 - Bühlmeyer, A.
A1 - Huber, P.
A1 - Laschat, S.
A1 - Schönhals, Andreas
T1 - Dynamics and ionic conductivity of ionic liquid crystals forming a hexagonal columnar mesophase
JF - Physical Chemistry Chemical Physics
N2 - For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflate ionic liquid crystals (ILCs) having different length of alkyl chains were investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. Three dielectric active processes were found by BDS for both samples. At low temperatures, a γ-process in the plastic crystalline state is observed which is assigned to localized fluctuations of methyl groups including nitrogen atoms in the guanidinium head. At higher temperatures but still in the plastic crystalline state, an α1-process takes place. An α2 process was detected by SHS but with a completely different temperature dependence of the relaxation times than that of the α1-relaxation. This result is discussed in detail, and different molecular assignments of the processes are suggested. At even higher temperatures, electrical conductivity is detected and an increase in the DC conductivity by four orders of magnitude at the phase transition from the plastic crystalline to the hexagonal columnar mesophase is found. This result is traced to a change in the charge transport mechanism from a delocalized electron hopping in the stacked aromatic systems (in the plastic phase) to one dominated by an ionic conduction in the quasi-1D ion channels formed along the supermolecular columns in the ILCs hexagonal mesophases.
KW - Ionic liquid crystalls
PY - 2018
DO - https://doi.org/10.1039/c7cp08186c
SN - 1463-9084
SN - 1463-9076
VL - 20
IS - 8
SP - 5626
EP - 5635
PB - Royal Society of Chemistry
AN - OPUS4-44254
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yildirim, Arda
A1 - Sentker, K.
A1 - Smales, Glen Jacob
A1 - Pauw, Brian Richard
A1 - Huber, P.
A1 - Schönhals, Andreas
T1 - Collective orientational order and phase behavior of a discotic liquid crystal under nanoscale confinement
JF - Nanosale advances
N2 - The phase behavior and molecular ordering of hexakishexyloxy triphenylene (HAT6) DLC under cylindrical nanoconfinement is studied utilizing differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), where cylindrical nanoconfinement is established through embedding HAT6 into the nanopores of anodic aluminum oxide membranes (AAO), and a silica membrane with pore diameters ranging from 161 nm down to 12 nm. Both unmodified and modified pore walls were considered, and in the latter case the pore walls of AAO membranes were chemical treated with n octadecylphosphonic acid (ODPA) resulting in the formation of a 2.2 nm thick layer of grafted alkyl chains. Phase transition enthalpies decrease with decreasing pore size, indicating that a large proportion of the HAT6 molecules within the pores has a disordered structure, which increases with decreasing pore size for both pore walls. In the case of the ODPA modification the amount of ordered HAT6 is increased compared to the unmodified case. The pore size dependencies of the phase transition temperatures were approximated using the Gibbs Thomson equation, where the estimated surface tension is dependent on the molecular ordering of HAT6 molecules within the pores and upon their surface. DS was employed to investigate the molecular ordering of HAT6 within the nanopores. These investigations revealed that with a pore size of around 38 nm, for the samples with the unmodified pore walls, the molecular ordering changes from planar axial to homeotropic radial. However, the planar axial configuration, which is suitable for electronic applications, can be successfully preserved through ODPA modification for most of the pore sizes.
KW - Discotic Liquid Crystals
KW - Nanoconfinement
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475222
DO - https://doi.org/10.1039/c8na00308d
SN - 2516-0230
VL - 1
IS - 3
SP - 1104
EP - 1116
PB - RSC
AN - OPUS4-47522
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
A1 - Krause, Christina
A1 - Zorn, R.
A1 - Schönhals, Andreas
T1 - Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy, advanced calorimetry and Neutron Scattering
N2 - Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n=5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations a γ-relaxation due to localized fluctuations as well as two glassy dynamics the αcore and αalkyl relaxation were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n=8 from a rigid constrained (n=5,6) to a softer system (n=10,12) on a molecular lenght scale was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition. The results were confirmed by in- and quasielastic neutron scattering
T2 - Confit 2022
CY - Grenoble, France
DA - 10.10.2022
KW - Glassy Dynamics
KW - Discotic Liquid Crystals
PY - 2022
AN - OPUS4-56661
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yildirim, Arda
A1 - Krause, Christina
A1 - Zorn, R.
A1 - Lohstroh, W.
A1 - Schneider, G. J.
A1 - Zamponi, M.
A1 - Holerer, O.
A1 - Frick, B.
A1 - Schönhals, Andreas
T1 - Complex molecular dynamics of a symmetric model discotic liquid crystal revealed by broadband dielectric, thermal and neutron spectroscopy
JF - Soft Matter
N2 - The molecular dynamics of the triphenylene-based discotic liquid crystal HAT6 is investigated by broadband dielectric spectroscopy, advanced dynamical calorimetry and neutron scattering. Differential scanning calorimetry in combination with X-ray scattering reveals that HAT6 has a plastic crystalline phase at low temperatures, a hexagonally ordered liquid crystalline phase at higher temperatures and undergoes a clearing transition at even higher temperatures. The dielectric spectra show several relaxation processes: a localized gamma-relaxation a lower temperature and a so called alpha-2-relaxation at higher temperatures. The relaxation rates of the alpha-2-relaxation have a complex temperature dependence and bear similarities to a dynamic glass transition. The relaxation rates estimated by hyper DSC, Fast Scanning calorimetry and AC Chip calorimetry have a different temperature dependence than the dielectric alpha-2-relaxation and follows the VFT-behavior characteristic for glassy dynamics. Therefore, this process is called alpha-1-relaxation. Its relaxation rates show a similarity with that of polyethylene. For this reason, the alpha-1-relaxation is assigned to the dynamic glass transition of the alkyl chains in the intercolumnar space. Moreover, this process is not observed by dielectric spectroscopy which supports its assignment. The alpha-2-relaxation was assigned to small scale translatorial and/or small angle fluctuations of the cores.
The neutron scattering data reveal two relaxation processes. The process observed at shorter relaxation times is assigned to the methyl group rotation. The second relaxation process at longer time scales agree in the temperature dependence of its relaxation rates with that of the dielectric gamma-relaxation.
KW - Discotic Liquid Crystals
PY - 2020
DO - https://doi.org/10.1039/c9sm02487e
VL - 16
IS - 8
SP - 2005
EP - 2016
PB - Royal Chemical Society
AN - OPUS4-50466
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yildirim, Arda
A1 - Krause, Christina
A1 - Huber, P.
A1 - Schönhals, Andreas
T1 - Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry
JF - Journal Molecular Liquids
N2 - Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n = 5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations probing the molecular mobility, a c-relaxation due to localized fluctuations as well as two glassy dynamics, the acore- and aalkyl-relaxation, were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n = 8 from a rigid constrained (n = 5,6) to a softer system (n = 10,12) was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene-like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition.
KW - Discotic liquid crystals
KW - Broadband dielectric spectroscopy
KW - Advanced calorimetry
PY - 2022
DO - https://doi.org/10.1016/j.molliq.2022.119212
VL - 358
SP - 1
EP - 10
PB - Elsevier B.V.
AN - OPUS4-54721
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yildirim, Arda
A1 - Kolmangadi, Mohamed Aejaz
A1 - Bühlmeyer, A.
A1 - Huber, P.
A1 - Laschat, S.
A1 - Schönhals, Andreas
T1 - Electrical conductivity and multiple glassy dynamics of crow-ether based columnar liquid crystals
JF - The Journal of Physical Chemistry B
N2 - The phase behavior of two unsymmetrical triphenylene crown ether-based columnar liquid crystals (CLCs) bearing different lengths of alkyl chains, KAL465 and KAL468, was investigated using differential scanning calorimetry (DSC). A plastic crystalline (Cry), columnar liquid crystalline (Colh) and an isotropic phase were observed along with two glass transitions in the Cry phase. The molecular mobility of the KAL compounds was further studied by a combination of broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques. By the BDS investigations, three dielectric active relaxation processes were observed for both samples. At low temperatures, a γ-process in the Cry state was detected and is assigned to the localized fluctuations taking place in the alkyl chains. An α2-process takes place at higher temperatures in the Cry phase. An α3 process was found in the Colh mesophase. The advanced calorimetric techniques consist of fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS) employing temperature modulated DSC and FSC (TMDSC and TMFSC). The advanced calorimetric investigations revealed that besides the α2 process in agreement with BDS, a second dynamic glass transition (α1-process) is present which is not observed by dielectric spectroscopy. The results are in good agreement with the glass transitions detected by DSC for this process. The temperature dependences of the relaxation rates of the α1 , α2 and α3 processes are all different. Therefore, different molecular assignments for the relaxation processes are proposed. In addition to the relaxation processes, a conductivity contribution was explored by BDS for both KAL compounds. The conductivity contribution appears in both Cry and Colh phases, where the conductivity increases by ca. one order of magnitude at phase transition from the crystalline to the hexagonal phase.
KW - Columnar Liquid Crystal
PY - 2020
DO - https://doi.org/10.1021/acs.jpcb.0c06854
VL - 124
IS - 39
SP - 8728
EP - 8739
PB - ACS
AN - OPUS4-51374
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yildirim, Arda
A1 - Bühlmeyer, A.
A1 - Hayash, S
A1 - Haenle, J. C.
A1 - Sentker, K.
A1 - Krause, Christina
A1 - Huber, Patrick
A1 - Laschat, Sabine
A1 - Schönhals, Andreas
T1 - Multiple glassy dynamics in dipole functionalized triphenylene-based discotic liquid crystals revealed by broadband dielectric spectroscopy and advanced calorimetry – assessment of the molecular origin
JF - Physical Chemistry Chemical Physics
N2 - A selected series of dipole functionalized triphenylene-based discotic liquid crystals (DLCs) was synthesized and investigated in a systematic way to reveal the phase behavior and molecular dynamics. The later point is of particular importance to understand the charge transport in such systems which is the key property for their applications such as organic field-effect transistors, solar cells or as nanowires in molecular electronics, and also to tune the properties of DLCs. The mesomorphic properties were studied by polarizing optical microscopy, X-ray diffraction, and differential scanning calorimetry, which were compared to the corresponding unfunctionalized DLC. The molecular dynamics were investigated by a combination of state-of-the-art broadband dielectric spectroscopy (BDS) and advanced calorimetry such as fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). Besides localized fluctuations, surprisingly multiple glassy dynamics were detected for all materials for the first time. Glassy dynamics were proven for both processes unambiguously due to the extraordinary broad frequency range covered. The a1-process is attributed to fluctuations of the alky chains in the intercolumnar space because a polyethylene-like glassy dynamics is observed. This corresponds to a glass transition in a confined three-dimensional space. The a2-process found at temperatures lower than a1-process, is assigned to small scale rotational and/or translational in plane fluctuations of the triphenylene core inside distorted columns. This can be considered as a glass transition in a one-dimensional fluid. Therefore, obtained results are of general importance to understand the glass transition, which is an unsolved problem of condensed matter science.
KW - Discotic Liquid Crystals
KW - Broadband dielectric spectroscopy
KW - Flash DSC
KW - Specific heat spectroscopy
PY - 2019
DO - https://doi.org/10.1039/c9cp03499d
SN - 1463-9076
VL - 21
IS - 33
SP - 18265
EP - 18277
PB - RSC
AN - OPUS4-48739
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
A1 - Szymoniak, Paulina
A1 - Sentker, K.
A1 - Butschies, M.
A1 - Bühlmeyer, A.
A1 - Laschat, S.
A1 - Huber, P.
A1 - Schönhals, Andreas
T1 - Molecular Mobility and Ionic Conductivity of Ionic Liquid Crystals Forming a Hexagonal Columnar Mesophase
N2 - For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflates ionic liquid crystals (ILCs) having different length of alkyl chains was investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). SHS was carried out by differential AC-chip calorimetry at higher frequencies and temperature modulated DSC at lower frequencies. These ILCs can form a hexagonal ordered columnar mesophase. Two relaxation processes were found by BDS for both samples. At low temperatures, a γ-processes is observed which is assigned to specific localized fluctuations. At higher temperatures, α1-processes take place. α2 processes were also detected by SHS but with a completely different temperature dependence of the relaxation times. Different molecular assignments of α1- and α2-processes are suggested. At even higher temperatures, conductivity was detected by BDS.
T2 - Spring Meeting of German Physical Society
CY - Berlin, Germany
DA - 12.03.2018
KW - Ionic liquid crystals
PY - 2018
AN - OPUS4-44504
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
A1 - Sentker, K.
A1 - Huber, P.
A1 - Schönhals, Andreas
T1 - Collective Orientational Order and Phase Behavior of a Discotic Liquid Crystal under Confinement
N2 - Discotic liquid crystals (DLCs) are a promising class of soft matter for electronic applications. This is due to their ability to self-organize into columns in a hexagonal columnar mesophase, driven by the overlapping of the π orbitals of their aromatic cores. This leads to a high charge-carrier mobility along the column axis. Previous studies on DLCs showed that their properties, such as phase transition temperatures and enthalpies, are susceptible to nanoconfinement. In this study, 2,3,6,7,10,11 hexakis[hexyloxy] triphenylene (HAT6) was confined into parallel aligned cylindrical nanopores of anodic aluminum oxide (AAO) membranes by melt infiltration. Furthermore, the pore surfaces of a series of membranes were chemically modified, resulting in a more hydrophobic pore surface than the unmodified ones. Collective orientational order and phase behavior of HAT6 confined into modified and unmodified nanopores of AAO were investigated by broadband dielectric spectroscopy and differential scanning calorimetry respectively.
T2 - Spring Meeting of German Physical Society
CY - Berlin, Germany
DA - 12.03.2018
KW - Discotic Liquid Crystals
PY - 2018
AN - OPUS4-44506
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
T1 - Liquid Crystals Forming a Columnar Mesophase: Structure, Dynamics and Electric Conductivity
N2 - The molecular dynamics and ionic conductivity of ionic liquid crystals (ILCs) forming a columnar mesophase, two linear-shaped tetramethylated guanidinium triflates ILCs having different lengths of alkyl chains, were investigated by a combination of Broadband Dielectric Spectroscopy (BDS) and Specific Heat Spectroscopy (SHS). Three processes were detected by BDS; at low temperature γ-process, at higher temperatures α-process and at even higher temperatures conductivity. The γ-process indicates localized fluctuations, and the α-process designates cooperative fluctuations. Slightly different restrictions were found for conductivity processes of LC536 and LC537 due to the slightly different lengths of alky chains. The conductivity mechanisms in the plastic crystalline and the columnar mesophase have been revealed by BDS and different charge carriers were assigned for the different phases. Furthermore, the cooperative dynamics were also probed by SHS. The cooperative dynamics probed by the different techniques (BDS and SHS) compared, and assigned to the different restrictions on the cooperativity due to the difference in the sensitivity of the techniques.
T2 - Seminar Vortrag Technische Universität Berlin
CY - Berlin, Germany
DA - 28.06.2018
KW - Columnar Liquid Crystals
KW - Ionic Liquid Crystals
PY - 2018
AN - OPUS4-45383
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
A1 - Sentker, Kathrin
A1 - Huber, Patrick
A1 - Schönhals, Andreas
T1 - Collective Orientational Order and Phase Behavior of a Discotic Liquid Crystal under Confinement
N2 - Discotic liquid crystals (DLCs) are a promising class of soft matter for electronic applications. This is due to their ability to self-organize into columns in a hexagonal columnar mesophase, driven by the overlapping of the π orbitals of their aromatic cores. This leads to a high charge-carrier mobility along the column axis. Embedding liquid crystals into nanopores of anodic aluminum oxide (AAO) results in a 2D nanoconfinement of these materials. This confinement affects their properties, compared to the bulk, such as phase transition temperatures and enthalpies, molecular mobility, and crystallization.
In this study, 2,3,6,7,10,11 hexakis[hexyloxy] triphenylene (HAT6) was confined into parallel aligned cylindrical nanopores of AAO membranes by melt infiltration. The membrane as confining hosts used have varying pore diameters, from 10 nm to 160 nm, covering a broad pore size range, thus, a better understanding of the confinement effect on phase behavior and molecular configuration in the pores. Furthermore, it is aimed to obtain axial ordering or to increase degree of axial ordering by chemically modifying the surfaces of the pores. Therefore, the pore surfaces the membranes were chemically modified, resulting in a more hydrophobic pore surface than the unmodified ones. The phase behavior was explored by a power-compensated DSC allowing the detecting of small changes in the phase behavior. In the literature, dielectric spectroscopy was demonstrated as a method to monitor molecular order inside the pores. Here, we also investigate the collective orientational order, corresponding to dominating molecular ordering, by dielectric spectroscopy.
T2 - 10th Conference on Broadband Dielectric Spectroscopy and its Applications
CY - Brussles, Belgium
DA - 26.08.2018
KW - Confined Columnar Liquid Crystals
PY - 2018
AN - OPUS4-45916
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
A1 - Sentker, Kathrin
A1 - Bühlmeyer, Andrea
A1 - Laschat, Sabine
A1 - Huber, Patrick
A1 - Schönhals, Andreas
T1 - Molecular dynamics of dipole functionalized triphenylene-based discotics
N2 - Since discovery of discotic liquid crystals (DLCs), consisting of a disklike rigid aromatic core and flexible alkyl chains attached to the core, dating back to Chandrasekhar’s work in 1977, they have been extensively investigated to reveal their fundamental properties and potential for applications. The researches on DLCs in last decades showed that DLCs can be considered as promising materials for organic electronic applications since they exhibit one dimensional high charge mobility along the column axis in a columnar mesophase. The mobilies of the rigid aromatic core and the flexible alkyl chains can influence their application properites, e.g. the charge carrier mobility, therefore, it needs to be explored in detailed.
In this study, a series of dipole functionalized triphenylene-based discotics, forming a columnar mesophase, were investigated to reveal the influence of the functionalization on phase behavior, molecular dynamics and as well as conductivity. The molecular mobility of the discotics was probed by broadband dielectric spectroscopy (BDS). In addition to conductivity and localized dynamics, glassy dynamics were also observed. The phase behavior of the material was explored by a power-compansated differential scanning calorimetry (DSC). Beside the phase transition temperatures and enthalpies, thermal glass transitions were found for all the materials. Moreover, the glassy dynamics were further investigated by Flash DSC, which is a chip-based calorimetry technique allows fast heating and cooling rates as high as 10000K/s.
T2 - 10th Conference on Broadband Dielectric Spectroscopy and its Applications
CY - Brussles, Belgium
DA - 26.08.2018
KW - Columnar liquid crystals
PY - 2018
AN - OPUS4-45918
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
A1 - Szymoniak, Paulina
A1 - Sentker, Kathrin
A1 - Huber, Patrick
A1 - Schönhals, Andreas
T1 - Molecular Mobility and Ionic Conductivity of Ionic Liquid Crystals Forming a Hexagonal Columnar Mesophase
N2 - For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflates ionic liquid crystals (ILCs) having different length of alkyl chains was investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. SHS was carried out by differential AC-chip calorimetry at higher frequencies and temperature modulated DSC at lower frequencies.
Two relaxation processes were found by BDS for both samples. At low temperatures, a γ-processes is observed which is assigned to specific localized fluctuations. At higher temperatures, α1-processes take place. α2 processes were also detected by SHS but with a completely different temperature dependence of the relaxation times. Different molecular assignments of α1- and α2-processes are suggested. At even higher temperatures, conductivity was detected by BDS. An increase in the DC conductivity by four orders of magnitude at the phase transition from the plastic crystalline to the hexagonal columnar mesophase is found. This result is traced to a change in the charge transport mechanism from a delocalized electron hopping in the stacked aromatic systems (in the plastic phase) to one dominated by an ionic conduction in the quasi-1D ion channels formed along the supermolecular columns in the ILC hexagonal mesophases.
T2 - 10th Conference on Broadband Dielectric Spectroscopy and its Applications
CY - Brussles, Belgium
DA - 26.08.2018
KW - Ionic Liquid Crystals
PY - 2018
AN - OPUS4-45914
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yildirim, Arda
A1 - Bühlmeyer, A.
A1 - Hayashi, S.
A1 - Haenle, J. C.
A1 - Sentker, K.
A1 - Huber, P.
A1 - Laschat, S.
A1 - Schönhals, Andreas
T1 - Molecular Dynamics of Dipole Functionalized Triphenylene-based Discotics
N2 - In this study, the molecular dynamics of a series of dipole functionalized triphenylene-based discotics, forming a columnar mesophase, were investigated by broadband dielectric spectroscopy (BDS). In addition to conductivity and localized dynamics, glassy dynamics were also observed. At higher temperatures an α1-processes and at low temperatures an α2 processes were detected having a completely different temperature dependence of its relaxation times. Different molecular assignments of α1- and α2-processes are suggested. The phase behavior of the material was explored under helium purge down to 100 K by differential scanning calorimetry (DSC). Besides the phase transition temperatures and enthalpies, one or two thermal glass transitions were found for all the materials. Moreover, the glassy dynamics were further investigated by Flash DSC, which is a chip-based calorimetry technique allowing for fast heating and cooling rates as high as 10000K/s.
T2 - Spring Meeting of German Physical Society
CY - Regensburg, Germany
DA - 01.04.2019
KW - Liquid Crystals
PY - 2019
AN - OPUS4-47827
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yesilcicek, Yasemin
A1 - Haas, S.
A1 - Suárez Ocano, Patricia
A1 - Zaiser, E.
A1 - Hesse, René
A1 - Többens, D. M.
A1 - Glatzel, U.
A1 - Manzoni, Anna Maria
T1 - Controlling Lattice Misfit and Creep Rate Through the γ' Cube Shapes in the Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy with Hf and W Additions
JF - High Entropy Alloys & Materials
N2 - Trace elements play an important role in the fine-tuning of complex material properties. This study focuses on the correlation of microstructure, lattice misfit and creep properties. The compositionally complex alloy Al10Co25Cr8Fe15Ni36Ti6 (in at. %) was tuned with high melting trace elements Hf and W. The microstructure consists of a γ matrix, γ' precipitates and the Heusler phase and it is accompanied by good mechanical properties for high temperature applications. The addition of 0.5 at.% Hf to the Al10Co25Cr8Fe15Ni36Ti6 alloy resulted in more sharp-edged cubic γ′ precipitates and an increase in the Heusler phase amount. The addition of 1 at.% W led to more rounded γ′ precipitates and the dissolution of the Heusler phase. The shapes of the γ' precipitates of the alloys Al9.25Co25Cr8Fe15Ni36Ti6Hf0.25W0.5 and Al9.25Co25Cr8Fe15Ni36Ti6Hf0.5W0.25, that are the alloys of interest in this paper, create a transition from the well-rounded precipitates in the alloy with 1% W containing alloy to the sharp angular particles in the alloy with 0.5% Hf. While the lattice misfit has a direct correlation to the γ' precipitates shape, the creep rate is also related to the amount of the Heusler phase. The lattice misfit increases with decreasing corner radius of the γ' precipitates. So does the creep rate, but it also increases with the amount of Heusler phase. The microstructures were investigated by SEM and TEM, the lattice misfit was calculated from the lattice parameters obtained by synchrotron radiation measurements.
KW - High entropy alloy
KW - Lattice misfit
KW - Creep
KW - Transmission electron microscopy
KW - X-ray diffraction
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565655
DO - https://doi.org/10.1007/s44210-022-00009-1
SP - 1
EP - 9
PB - Springer
AN - OPUS4-56565
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yesilcicek, Yasemin
A1 - Wetzel, Annica
A1 - Witt, Julia
A1 - Stephan-Scherb, C.
A1 - Ozcan, Ozlem
T1 - Investigation on gradient Fe-Ni-Cr-Mn alloy using diffusion multiples
N2 - The high-throughput synthesis and characterization of potential material combinations plays an important role in accelerating the development of new materials. Diffusion controlled synthesis of gradient alloys is widely used to create phase diagrams, and it is also one of the most effective combinatorial approaches for rapid realization of potential material combinations.
This study focuses on the synthesis and investigation of the quaternary multi-principle-element alloy (MPEA) FeNiCrMn by means of diffusion multiples, the correlation of their microstructural and chemical characterization data with their application relevant properties like local mechanical and corrosion properties. A diffusion system was set up by combining an equimolar ternary alloy (FeNiCr) with a single diffusing metallic component (Mn) with the highest interdiffusion coefficient. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to collect microstructural and compositional information which were correlated to local mechanical properties studied with nanoindentation. Local corrosion properties were investigated by means of Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). We have observed that a >50 μm deep homogeneous diffusion zone was formed the thickness of which scales with the duration of the thermal treatment. Beyond the Mn-concentration gradient in the FeNiCr matrix, a distinct Cr-rich secondary phase, characterized by high hardness and elastic modulus values appeared. We synthesized MPEAs with selected compositions from the diffusion zone as well as the Cr-rich phase as bulk alloys for electrochemical corrosion studies under different environmental conditions. The presentation will summarize the results of our correlative study on the mechanical properties and corrosion resistance of the quaternary multi-principle-element alloy (MPEA) FeNiCrMn family.
T2 - MRS Spring 2023
CY - San Francisco, California, USA
DA - 10.04.2023
KW - Chemically Complex Materials
KW - CCMat
KW - Diffusion multiples
PY - 2023
AN - OPUS4-59404
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yesilcicek, Yasemin
A1 - Wetzel, Annica
A1 - Witt, Julia
A1 - Dimper, Matthias
A1 - Ozcan, Ozlem
T1 - Corrosion and mechanical properties of multi principal element alloys designed by using diffusion couples
N2 - The efficient exploration of novel alloy chemistries is crucial for advancing the development of new materials. Diffusion-controlled synthesis of gradient alloys is an intelligent approach for creating phase diagrams and to effectively identify potential material combinations with tailored properties.
This project focusses on the design of quaternary multi-principle-element alloys (MPEAs) using diffusion couples. Our diffusion system contains an equimolar ternary alloy (FeNiCr) and additional single diffusing elements e.g. Mn and Mo. We determined the optimal temperature ranges for the diffusion thermal treatment by means of ThermoCalc simulations with the aim to form single-phase MPEAs. Microstructure and chemical characterization of the diffusion couples were performed by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). For most alloy couples, the diffusion zone contained a single-phase alloy matrix with diffusion-induced compositional gradient as well as precipitation phases. This heterogeneity makes the diffusion couples interesting materials to investigate local mechanical and corrosion properties. Thus, local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). Nanoindentation was used for the analysis of local mechanical properties.
Based on the results of the local corrosion analysis, we have selected single-phase alloy chemistries along the diffusion zone and reproducibly synthesized these alloys in bulk for detailed corrosion studies by means of potentiodynamic polarization and SECM.
The presentation will briefly summarize our methodology and motivation for using diffusion couples as an efficient tool for exploring phase diagrams of MPEAs in the search for new alloy chemistries and the results of our correlative study on the mechanical and corrosion properties of these materials.
T2 - 244th ECS Meeting
CY - Gothenburg, Sweden
DA - 08.10.2023
KW - Chemically Complex Materials
KW - CCMat
KW - Corrosion
PY - 2023
AN - OPUS4-59407
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Yesilcicek, Yasemin
A1 - Wetzel, Annica
A1 - Witt, Julia
A1 - Dimper, Matthias
A1 - Ozcan, Ozlem
T1 - Correlation of corrosion and mechanical properties of Fe-Ni-Cr-Mn alloy synthesized by diffusion multiples
N2 - The efficient exploration of novel alloy compositions is crucial for advancing the development of new materials. One widely utilized approach for creating phase diagrams is the use of diffusion-controlled synthesis for gradient alloys. This method is also an effective means for rapidly identifying potential material combinations.
The present study focusses on the exploration of quaternary multi-principle-element alloys (MPEAs) using diffusion multiples. We established a diffusion system by combining an equimolar ternary alloy (FeNiCr) with single diffusing elements Mn and Mo. Using ThermoCalc simulations, we determined suitable temperature ranges where we can expect the formation of single-phase alloys. Depending on the diffusion constants of the selected metals, diffusion times were adjusted to obtain diffusion zones with a depth of greater than 50 μm. Microstructural and compositional information was gathered via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) and correlated to local mechanical properties evaluated by means of nanoindentation. Local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM).
Our results indicate that the ThermoCalc simulations have a good predictive power for crystallographic phases. However, especially with the Mn-FeNiCr system, formation of Cr-rich secondary phases were observed, which led to Cr-depletion and thus to localized corrosion processes in the matrix at the vicinity of the secondary phases. Based on the results of the local electrochemical tests, we have selected single-phase compositions along the diffusion zone and synthesized these alloys in bulk for corrosion studies by means of potentiodynamic polarization and SECM.
The presentation will summarize our methodology using diffusion couples as an
efficient tool for exploring compositional spaces of MPEAs in the search for novel single-phase alloys and the results of our correlative study on the mechanical and corrosion properties of these materials.
T2 - EUROCORR2023
CY - Brussels, Belgium
DA - 27.08.2023
KW - Chemically Complex Materials
KW - CCMat
KW - Corrosion
PY - 2023
AN - OPUS4-59408
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wurzler, Nina
A1 - Sobol, Oded
A1 - Altmann, Korinna
A1 - Radnik, Jörg
A1 - Özcan Sandikcioglu, Özlem
T1 - Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins—Part I: Effect on surface chemistry and corrosion behavior
JF - Materials and Corrosion
N2 - Stainless steel AISI 304 surfaces were studied after a mild anodic polarization for oxide growth in the presence and absence of two derivatives of vitamin B2 (riboflavin and flavin mononucleotide) that can be secreted by metal‐reducing bacteria and act as a chelating agent for iron species. The alterations in oxide chemistry were studied by means of surface‐sensitive techniques such as X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry analysis. The complementary electrochemical characterization revealed a preferential growth of an oxide/hydroxide iron‐rich film that is responsible for an altered pit initiation and nucleation behavior. These findings suggest that as the corrosion behavior is determined by the interplay of the chemical and electronic properties, only a mild anodic polarization in the presence of redox‐active molecules is able to alter the chemical and electronic structure of the passive film formed on stainless steel AISI 304. This helps to achieve a profound understanding of the mechanisms of microbially influenced corrosion (MIC) and especially the possible effects of the redox‐active biomolecules, as they may play an important role in the corrosion susceptibility of stainless steel surfaces.
KW - Corrosion
KW - Stainless steel
KW - Surface analysis
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528117
DO - https://doi.org/10.1002/maco.202012191
VL - 72
IS - 6
SP - 974
EP - 982
PB - Wiley
AN - OPUS4-52811
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wurzler, Nina
A1 - Schütter, J. D.
A1 - Wagner, R.
A1 - Dimper, M.
A1 - Lützenkirchen-Hecht, D.
A1 - Özcan Sandikcioglu, Özlem
T1 - Trained to corrode: Cultivation in the presence of Fe(III) increases the electrochemical activity of iron reducing bacteria – An in situ electrochemical XANES study
JF - Electrochemistry Communications
N2 - This paper reports results from in situ electrochemical X-ray absorption near-edge spectroscopy (XANES) studies of the corrosion processes on model thin iron films in the presence of iron reducing bacteria Shewanella putrefaciens. Here we investigate the electrochemical activity of two cultures grown in the presence and absence of Fe(III) citrate in the culture medium. The XANES spectra and the OCP data of the Fe sample incubated with the culture grown in absence of Fe(III) did not show any significant changes during twenty hours of monitoring. In the case of the culture grown in Fe(III) containing medium, an accelerated dissolution of the iron film was observed together with the formation of a mixed Fe(II)-Fe(III) hydroxide surface layer. The open circuit potential (OCP) steadily approached the free corrosion potential of iron in neutral chloride containing electrolytes, indicating a continuous dissolution process without passivation.
KW - Microbiologically influenced corrosion
KW - XANES
KW - Electrochemistry
KW - Iron reducing bacteria
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-505732
DO - https://doi.org/10.1016/j.elecom.2020.106673
VL - 112
SP - 106673
PB - Elsevier B.V.
AN - OPUS4-50573
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wurzler, Nina
A1 - Schutter, Jan David
A1 - Wagner, R.
A1 - Dimper, Matthias
A1 - Lützenkirchen-Hecht, D.
A1 - Özcan Sandikcioglu, Özlem
T1 - Abundance of Fe(III) during cultivation affects the microbiologically influenced corrosion (MIC) behaviour of iron reducing bacteria Shewanella putrefaciens
JF - Corrosion Science
N2 - The effect of the presence of Fe(III) during the cultivation on the electrochemical activity and corrosion behaviour of dissimilatory iron reducing bacteria Shewanella putrefaciens was studied by means of ex situ and in situ X-ray absorption near-edge spectroscopy (XANES). Stainless steel AISI 304 and thin iron films were studied as substrates. XANES analysis indicated an accelerated iron dissolution and growth of an oxide/hydroxide film for the culture grown with Fe(III) in comparison to the culture grown in absence of Fe(III). Electrochemical Analysis indicated that the biofilm resulted in acceleration of the general corrosion but provides protection against local corrosion.
KW - Stainless Steel
KW - XANES
KW - Iron
KW - Cyclic Voltammetry
KW - Microbiological Corrosion
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513788
DO - https://doi.org/10.1016/j.corsci.2020.108855
VL - 174
SP - 108855
PB - Elsevier Ltd.
AN - OPUS4-51378
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wurzler, Nina
A1 - Wagner, Ralph
A1 - Schutter, Jan David
A1 - Das, Chayanika
A1 - Dimper, Matthias
A1 - An, Biwen
A1 - Koerdt, Andrea
A1 - Lützenkirchen-Hecht, Dirk
A1 - Özcan Sandikcioglu, Özlem
T1 - Effect of cultivation conditions on the electrochemical activity of metal reducing bacteria (mrb) on stainless steel surfaces
N2 - Investigation of the electrochemical activity of two cultures grown with and without abundance of Fe(III) and their different ability to reduce and therefore dissolve iron oxides in steel and model iron thin films.
T2 - Eurocorr2019
CY - Sevilla, Spain
DA - 09.09.2019
KW - X-ray spectroscopic techniques
KW - Microbiologically influenced corrosion
KW - MIC
KW - XANES
KW - Metal reducing bacteria
KW - In situ
PY - 2019
AN - OPUS4-49692
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wurzler, Nina
A1 - Kleinbub, Sherin
A1 - Koerdt, Andrea
A1 - Özcan Sandikcioglu, Özlem
T1 - Effect of conditioning layers on the attachment and biofilm formation of electroactive bacteria on stainless steel
N2 - The characteristics of different molecules chosen as representatives for specific functionalities in conditioning layers play an important role on attachment behavior and later biofilm formation of bacteria. The chemical composition is a major component influencing the attachment but there is a conglomerate of influences.
T2 - Eurocorr2018
CY - Krakow, Poland
DA - 09.09.2018
KW - Conditioning layer
KW - Stainless steel
KW - Bacterial attachment
PY - 2018
AN - OPUS4-46487
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Woydt, Mathias
A1 - Wäsche, Rolf
A1 - Brandt, Guido
A1 - Ehrke, Roman
T1 - Tribology in hot steam - for waste heat recovery or for energy harvesting -
N2 - The wear rates of self-amted alumina couples show that friction as well as wear is largely determined by the above mentioned hydro-thermal conditions. The presence of water and ist amount available in the surrounding system either in liquid or in gaseous from plays a key role for friction and wear behavior and cabe benefical for the tribological profile of steam degradation resistant materials. Hot steam enhances the tribo-chemical formations of oxides and hydroxides on MgO-ZrO2, alumina and antimony impregnated carbon.
T2 - 21th International Colloquium Tribology
CY - Stuttgart/Ostfildern, Germany
DA - 09.01.2018
KW - Friction
KW - Alumina
KW - Hot steam
PY - 2018
AN - OPUS4-43895
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wolff, M.
A1 - Wonneberger, R.
A1 - Freiberg, K.E.
A1 - Hertwig, Andreas
A1 - Bonse, Jörn
A1 - Giebeler, L.
A1 - Koitzsch, A.
A1 - Kunz, C.
A1 - Weber, H.
A1 - Hufenbach, J.K.
A1 - Müller, F.A.
A1 - Gräf, S.
T1 - Formation of laser-induced periodic surface structures on Zr-based bulk metallic glasses with different chemical composition
JF - Surfaces and Interfaces
N2 - Bulk metallic glasses (BMG) are amorphous metal alloys known for their unique physical and mechanical properties. In the present study, the formation of femtosecond (fs) laser-induced periodic surface structures (LIPSS) on the Zr-based BMGs Zr46Cu46Al8, Zr61Cu25Al12Ti2, Zr52.5Cu17.9Al10Ni14.6Ti5 (Vit105) and Zr57Cu15.4Al10Ni12.6Nb5 (Vit106) was investigated as a function of their different chemical composition. For this purpose, LIPSS were generated on the sample surfaces in an air environment by fs-laser irradiation (λ = 1025 nm, τ = 300 fs, frep = 100 kHz). The surface topography was characterized by scanning electron microscopy and atomic force microscopy. Moreover, the impact of LIPSS formation on the structure and chemical surface composition was analyzed before and after fs-laser irradiation by X-ray diffraction and X-ray photoelectron spectroscopy as well as by transmission electron microscopy in combination with energy dispersive X-ray spectroscopy. Despite the different chemical composition of the investigated BMGs, the fs-laser irradiation resulted in almost similar properties of the generated LIPSS patterns. In the case of Zr61Cu25Al12Ti2, Vit105 and Vit106, the surface analysis revealed the preservation of the amorphous state of the materials during fs-laser irradiation. The study demonstrated the presence of a native oxide layer on all pristine BMGs. In addition, fs-laser irradiation results in the formation of laser-induced oxide layers of larger thickness consisting of an amorphous ZrAlCu-oxide. The precise laser-structuring of BMG surfaces on the nanoscale provides a versatile alternative to thermoplastic forming of BMG surfaces and is of particular interest for the engineering of functional material surfaces.
KW - Bulk metallic glasses
KW - Femtosecond laser
KW - Laser-induced periodic surface structures (LIPSS)
KW - Chemical analysis
KW - Oxidation
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581799
DO - https://doi.org/10.1016/j.surfin.2023.103305
SN - 2468-0230
VL - 42
SP - 1
EP - 11
PB - Elsevier B.V.
AN - OPUS4-58179
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Wolf, Jako
A1 - Stawski, Tomasz
A1 - Smales, Glen Jacob
A1 - Thünemann, Andreas
A1 - Emmerling, Franziska
T1 - SI Files for "Towards automation of the polyol process for the synthesis of silver nanoparticles"
N2 - The graphml file: reaction_graph_AgNP.graphml is included. It contains topological information (Fig. 1 in the main text) about the reaction setup and metadata with reaction condtions. It used by the Python API used to control the Chemputer.
SAXS reports. The complete report sheets generated by McSAS are included. They contain extended information characterising the size distributions and the fitting parameters.
NP3_I: saxs_report_NP3_I.pdf
NP3_II: saxs_report_NP3_II.pdf
NP3_III: saxs_report_NP3_III.pdf
NP3_IV: saxs_report_NP3_IV.pdf
NP5_I: saxs_report_NP5_I.pdf
NP5_II: saxs_report_NP5_II.pdf
NP5_III: saxs_report_NP5_III.pdf
KW - Automated synthesis
KW - Silver
KW - Nanoparticles
PY - 2022
DO - https://doi.org/10.5281/zenodo.5910614
PB - Zenodo
CY - Geneva
AN - OPUS4-55197
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wolf, J.
A1 - Stawski, Tomasz
A1 - Smales, Glen Jacob
A1 - Thünemann, Andreas
A1 - Emmerling, Franziska
T1 - Towards automation of the polyol process for the synthesis of silver nanoparticles
JF - Scientific Reports
N2 - Metal nanoparticles have a substantial impact across diferent felds of science, such as photochemistry, energy conversion, and medicine. Among the commonly used nanoparticles, silver nanoparticles are of special interest due to their antibacterial properties and applications in sensing and catalysis. However, many of the methods used to synthesize silver nanoparticles often do not result in well-defned products, the main obstacles being high polydispersity or a lack of particle size tunability. We describe an automated approach to on-demand synthesis of adjustable particles with mean radii of 3 and 5 nm using the polyol route. The polyol process is a promising route for silver nanoparticles e.g., to be used as reference materials. We characterised the as-synthesized nanoparticles using small-angle X-ray scattering, dynamic light scattering and further methods, showing that automated synthesis can yield colloids with reproducible and tuneable properties.
KW - Sillver
KW - Nanoparticles
KW - Automated synthesis
KW - Chemputer
KW - Scattering
KW - SAXS
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546803
DO - https://doi.org/10.1038/s41598-022-09774-w
VL - 12
IS - 1
SP - 1
EP - 9
PB - Nature Springer
AN - OPUS4-54680
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Witt, Julia
T1 - In situ Atomic Force Microscopy (AFM) studies of corrosion processes on thin film coated AA2024-T3 aluminium alloy surfaces
N2 - The performance of functional coatings relies strongly on the stability of the polymer-metal interface. The increasing utilization of multi-material structures in the automotive and aerospace industry necessitates a fundamental understanding of the processes leading to interface degradation for the development of novel strategies to increase corrosion and delamination resistance.
The aim of this project is to investigate the corrosion processes at the buried interface of thin film coated aluminium alloy AA2024-T3 under corrosive and coupled corrosive-mechanical load. A spin coating procedure was developed to synthesize epoxy-like coatings and their nanofiller loaded composites with controlled thickness by layer-by-layer deposition of poly[(o-cresyl glycidyl ether)-co-formaldehyde] and poly-(ethylenimine) bi-layers. Our results indicate that the incorporation of graphene into the epoxy-based coatings leads to the improvement of mechanical and barrier properties. Furthermore, the functional groups play important roles in the interfacial bonding between polymer matrix and the nanofillers. Atomic force microscopy (AFM) results indicate very homogeneous and dense films with a thickness of ~25 nm per bi-layer and the successful integration of the nanofillers into the composite coatings. Ellipsometry measurements of film thickness verified a proportional film growth with the number of deposited layers.
The degradation and delamination behavior of the coating systems was characterized by means of in situ AFM corrosion experiments. Complementary energy dispersive X-ray spectroscopy (EDX) analysis was used to correlate the corrosion and delamination behavior with the different intermetallic particle chemistries and distributions. The presentation will summarize our results on the effect of coating composition and build-up on the local corrosion processes on thin film covered AA2024-T3 aluminium alloys.
T2 - Eurocorr 2021
CY - Online meeting
DA - 20.09.2021
KW - In situ AFM
KW - Corrosion
KW - Thin epoxy-based films
PY - 2021
AN - OPUS4-54053
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Witt, Julia
A1 - Almalla, Ahed
A1 - Özcan Sandikcioglu, Özlem
T1 - In situ AFM studies of deformation and corrosion processes on AA2024-T3 aluminium alloy
N2 - The performance of functional coatings and adhesively joined hybrid components relies strongly on the stability of the polymer-metal interface. With the increasing utilization of multi-material structures in the automotive and aerospace industry, it is of great scientific and technical interest to understand the processes leading to interface degradation and to develop novel strategies to increase corrosion and delamination resistance.
The aim of this project is to develop thin epoxy-based films on aluminium alloy AA2024-T3 as a model system and to investigate their interfacial stability under corrosive and coupled corrosive-mechanical load. Electrochemical and spectroscopic methods were used for the characterisation of the film properties and in situ corrosion experiments were performed by means of AFM. The deformation properties of the aluminium alloy and the model coatings were investigated by means of scanning Kelvin probe force microscopy (SKPFM) utilizing the integrated tensile stage.
The presentation will give a brief overview of the capabilities of the new AFM setup to foster future collaborations and summarize our work on the interface stability of model coatings.
T2 - Abteilungskolloquium FB6
CY - Berlin, Germany
DA - 27.11.2018
KW - Corrosion
KW - In situ Atomic Force Microscopy (AFM)
KW - Aluminium alloy
KW - Scanning Kelvin Probe Force Microscopy (SKPFM)
PY - 2018
AN - OPUS4-48027
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Witt, Julia
A1 - Almalla, Ahed
A1 - Özcan Sandikcioglu, Özlem
T1 - AFM-Untersuchungen von funktionellen Beschichtungen und Strukturänderungen unter mechanischer Beanspruchung
N2 - Die Rasterkraftmikroskopie (AFM) hat sich in den letzten Jahren als eine vielseitige Abbildungstechnik von Oberflächen mit einer sehr hohen Ortsauflösung etabliert. Über die Untersuchung der reinen Oberflächentopographie sind erweiterte Modi in der Lage, gleichzeitig Informationen über die elektrischen und magnetischen Eigenschaften sowie Adhäsionsprozesse auf Oberflächen zu liefern. Interessanter wird es, wenn das AFM mit geeigneten Messzellen für in-situ-Untersuchungen in kontrollierten Atmosphären oder in Elektrolyten unter elektrochemischer Kontrolle ausgestattet ist. Dies ermöglicht die Untersuchung von Korrosions- und Adhäsionsprozessen unter Bedingungen, die die Betriebsumgebung repräsentieren.
Ein aktueller Forschungsschwerpunkt unseres Fachbereiches liegt in den Untersuchungen der Deformationseigenschaften von Funktionsschichten auf Leichtmetalllegierungen, sowie in situ Untersuchungen des Korrosionsverhaltens unter kombinierter korrosiver und mechanischer Beanspruchung mittels AFM. Durch die Integrierung eines Zug-Druckmoduls in den Probentisch des Rasterkraftmikroskops haben wir jetzt die Möglichkeit, verschiedene Materialien uniaxialen Umformversuchen mit bis zu 5 kN Kraft zu unterziehen. Dabei können unter anderem auch zyklische Belastungen genutzt werden, um Ermüdungsprozesse zu simulieren. Da die Messungen in situ ohne die De- und Remontage der Probe durchgeführt werden, ermöglicht der Aufbau nicht nur Messungen mit präziser Positionssteuerung, sondern auch die Untersuchung von Prozessen im elastischen Bereich, die für die Aufklärung der Mechanismen, die zu Ermüdungsversagen führen, entscheidend sind.
Die Posterpräsentation wird detaillierte Informationen zum neuen AFM-Setup liefern und unsere aktuellen Ergebnisse zur Verformung dünner Schutzschichten auf AA2024-T3 zusammenfassen.
T2 - Hybrid, Materials and Structures
CY - Bremen, Germany
DA - 18.04.2018
KW - Kelvinsondenkraftmikroskopie
KW - Funktionelle Beschichtungen
KW - Kombinierete korrosive und mechanische Beanspruchung
KW - Lokale Korrosion
KW - Delamination
KW - Deformation
PY - 2018
AN - OPUS4-46522
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Witt, Julia
A1 - Almalla, Ahed
A1 - Stepien, Daniel
A1 - Özcan Sandikcioglu, Özlem
T1 - Multilayer thin coatings for corrosion protection of AA2024-T3 aluminium alloy
N2 - The performance of adhesively joined hybrid components relies strongly on the stability of the adhesive-material interface. With the increasing utilization of multi-material structures in the automotive and aerospace industry, it is of great scientific and technical interest to understand the processes leading to adhesive failure and to develop novel strategies to increase corrosion and delamination resistance of adhesive joints.
The aim of this study is to develop thin epoxy based films and their carbon nanofiller loaded composites on aluminium alloy AA2024-T3 and to investigate their interfacial stability under corrosive and coupled corrosive-mechanical load. Spin coating was used for the layer-by-layer deposition of poly[(o-cresyl glycidyl ether)-co-formaldehyde] and poly-(ethylenimine) bi-layers. Carbon nanofillers are introduced either by mixing into the coating components or in between individual layers. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis was performed to investigate the porosity and water uptake of the model films, respectively. Atomic force microscopy (AFM) results indicated a very homogeneous and dense film with low surface roughness. The bi-layer thickness ranged between 30 to 40 nm. Electrochemical measurements show a higher corrosion resistance with the increase of the bi-layer number.
The main novelty of this contribution is the in-situ AFM investigations under coupled corrosive-mechanical load. For this purpose, a tensile module capable of uniaxial stretching and compression with up to 5 kN force was integrated into the AFM stage. Stretching experiments were performed to investigate the mechanical properties and adhesion of the films, as well as structural changes of the film morphology during uniaxial deformation. The contribution will provide detailed information on the new AFM setup and summarize our results on the stability of model epoxy and nanocomposite films on AA2024-T3.
T2 - EURADH 2018
CY - Lisbon, Portugal
DA - 05.09.2018
KW - Electrochemical Empedance Spectroscopy (EIS)
KW - Scanning Kelvin Probe Force Microscopy (SKPFM)
KW - Corrosion
KW - Delamination
KW - Aluminium
KW - Epoxide
PY - 2018
AN - OPUS4-46513
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Witt, Julia
T1 - Exploring innovative Materials and in situ techniques
N2 - Presentation of some projects conducted in recent years related to corrosion studies and research on electrocatalysis. The talk was part of a seminar at the University of Toronto and took place within the framework of a scientific exchange stay.
T2 - Seminar at the University of Toronto
CY - Toronto, Canada
DA - 11.10.2023
KW - Multi-principal element alloys (MPEAs)
KW - Electrocatalysis
KW - Corrosion
KW - Materials acceleration platforms (MAPs)
PY - 2023
AN - OPUS4-59029
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wintzheimer, S.
A1 - Szczerba, Wojciech
A1 - de Oliveira Guilherme Buzanich, Ana
A1 - Kashiwaya, S.
A1 - Klein, A.
A1 - Jaegermann, W.
A1 - Toupance, T.
A1 - Shmeliov, A.
A1 - Nicolosi, V.
A1 - Heuzé, K.
A1 - Mandel, K.
A1 - Dembski, S.
T1 - Discovering the determining parameters for the photocatalytic activity of TiO2 colloids based on an anomalous dependence on the specific surface area
JF - Particle & Particle Systems Characterization
N2 - The photocatalytic (PC) performance of titanium dioxide (TiO2) nanoparticles strongly depends on their specific surface, the presence of crystal defects, their crystal phase, and the exposed crystal facets. In order to understand which of these factors contributes most significantly to the PC activity of TiO2 colloids, all of them have to be individually analyzed. This study entails the synthesis of five anatase nanocrystal samples. By maintaining the same reactant ratios as well as hydrothermal sol–gel synthesis route and only varying the autoclaving time or temperature, different crystallite sizes are obtained under comparable experimental conditions. A decrease in PC performance with increase in specific surface area is found. Such an unexpected counterintuitive result establishes the basis for a better understanding of the crucial factors that ultimately determine the PC activity. These are investigated by studying nanocrystals bulk and surface structure and morphology using a selection of complementary analysis methods (X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), X-ray diffraction (XRD)…). It is found that a change in the nanocrystal morphology from an equilibrium state truncated tetragonal bipyramid to a more elongated rod-like structure accompanied by an increase in oxygen vacancies is responsible for an augmented PC activity of the TiO2 nanocrystals.
KW - Ti-based colloids
KW - Photocatalysis
KW - Spectroscopy
KW - XAFS
PY - 2018
DO - https://doi.org/10.1002/ppsc.201800216
SN - 0934-0866
SN - 1521-4117
VL - 35
IS - 9
SP - 1800216, 1
EP - 10
PB - Wiley Online Library
AN - OPUS4-46068
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wilke, Marco
A1 - Röder, Bettina
A1 - Paul, Martin
A1 - Weller, Michael G.
T1 - Sintered glass monoliths as supports for affinity columns
JF - Separations
N2 - A novel stationary phase for affinity separations is presented. This material is based on sintered borosilicate glass readily available as semi-finished filter plates with defined porosity and surface area. The material shows fast binding kinetics and excellent long-term stability under real application conditions due to lacking macropores and high mechanical rigidity. The glass surface can be easily modified with standard organosilane chemistry to immobilize selective binders or other molecules used for biointeraction. In this paper, the manufacturing of the columns and their respective column holders by 3D printing is shown in detail. The model system protein A/IgG was chosen as an example to examine the properties of such monolithic columns under realistic application conditions. Several specifications, such as (dynamic) IgG capacity, pressure stability, long-term performance, productivity, non-specific binding, and peak shape, are presented. It could be shown that due to the very high separation speed, 250 mg antibody per hour and column can be collected, which surpasses the productivity of most standard columns of the same size. The total IgG capacity of the shown columns is around 4 mg (5.5 mg/mL), which is sufficient for most tasks in research laboratories. The cycle time of an IgG separation can be less than 1 min. Due to the glass material’s excellent pressure resistance, these columns are compatible with standard HPLC systems. This is usually not the case with standard affinity columns, limited to manual use or application in low-pressure systems. The use of a standard HPLC system also improves the ability for automation, which enables the purification of hundreds of cell supernatants in one day. The sharp peak shape of the elution leads to an enrichment effect, which might increase the concentration of IgG by a factor of 3. The final concentration of IgG can be around 7.5 mg/mL without the need for an additional nano-filtration step. The purity of the IgG was > 95% in one step and nearly 99% with a second polishing run.
KW - Affinity Chromatography
KW - Affinity Extraction
KW - Affinity Separation
KW - Protein Purification
KW - Down Stream Processing
KW - Antibody Purification
KW - Diagnostic Antibodies
KW - Therapeutic Antibodies
KW - Automated Purification
KW - HPLC
KW - FPLC
KW - IgG determination
KW - Concentration step
KW - Monoclonal Antibodies
KW - Polyclonal Antibodies
KW - Human Plasma
KW - Glass Support
KW - Borosilicate Glass
KW - Monolith
KW - Sintered Material
KW - Additive Manufacturing
KW - Column holder
KW - Construction
KW - Open Science
KW - Citizen Science
KW - Protein A
KW - Regeneration
KW - High-Speed Separations
KW - Robustness
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527581
DO - https://doi.org/10.3390/separations8050056
SN - 2297-8739
VL - 8
IS - 5
SP - 1
EP - 16
PB - MDPI
CY - Basel
AN - OPUS4-52758
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wilke, Manuel
A1 - Akhemtova, Irina
A1 - Rademann, K.
A1 - Emmerling, Franziska
T1 - Mechanochemical synthesis of cerium(IV)-phosphonates
JF - Journal of materials science
N2 - The syntheses and crystal structures of two cerium(IV) phosphonates are presented. Cerium(IV) bis(phenylphosphonate) Ce(O3PC6H5)2 1 can be formed from precipitation and mechanochemical reaction, whereas cerium(IV) bis(carboxymethylphosphonate) monohydrate Ce(O3PCH2COOH)2 H2O 2 is only accessible via ball milling. All reactions proceed very fast and are completed within a short time span. In situ measurements for the syntheses of 1 show that the product occurs within seconds or a few minutes, respectively. The structures were solved from powder X-ray diffraction data.
KW - In situ studies
KW - Mechanochemistry
KW - XRD
PY - 2018
DO - https://doi.org/10.1007/s10853-018-2507-x
SN - 0022-2461
SN - 1573-4803
VL - 53
IS - 19
SP - 13733
EP - 13741
PB - Springer Science + Business Media B.V.
AN - OPUS4-45672
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wiesner, Yosri
A1 - Hoffmann, Thomas
A1 - Range, David
A1 - Altmann, Korinna
T1 - Microplastics in sediments of the river Rhine—A workflow for preparation and analysis of sediment samples from aquatic river systems for monitoring purposes
JF - Applied Research
N2 - AbstractMicroplastics (MP) can be detected in all environmental systems. Marine and terrestrial aquatic systems, especially the transported suspended solids, have often been the focus of scientific investigations in the past. Sediments of aquatic river systems, on the other hand, were often ignored due to the time‐consuming sample preparation and analysis procedures. Spectroscopic measurement methods counting particle numbers are hardly suitable as detection methods, because there are plenty of natural particles next to a small number of MP particles. Integral methods, such as thermoanalytical methods are determining the particle mass independently of the inorganic components.In this study, a workflow for sample preparation via density separation and subsequent analysis by thermal extraction desorption‐gas chromatography/mass spectrometry is presented, which leads to representative and homogeneous samples and allows fast and robust MP mass content measurements suitable for routine analysis. Polymers were identified and quantified in all samples. Polyethylene and styrene‐butadiene rubber are the dominant polymers, besides polypropylene and polystyrene. Overall, total polymer masses between 1.18 and 337.0 µg/g could be determined. Highest MP concentrations in riverbed sediment are found in sites characterized by low flow velocities in harbors and reservoirs, while MP concentrations in sandy/gravelly bed sediments with higher flow velocities are small.
KW - Microplastics
KW - Density separation
KW - TED-GC/MS
KW - NaI
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597335
DO - https://doi.org/10.1002/appl.202200125
SP - 1
EP - 10
PB - Wiley VHC-Verlag
AN - OPUS4-59733
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wiesner, Yosri
A1 - Giovannozzi, A.M.
A1 - Fadda, M.
A1 - Sacco, A.
A1 - Putzu, M.
A1 - Norberta, S.
A1 - Lorenzo, M.
A1 - Miclea, P.-T.
A1 - Benismail, N.
A1 - Maltseva, A.
A1 - van Bavel, B.
A1 - Altmann, Korinna
T1 - Reference material candidates for Microplastic analysis
N2 - Microplastic reference material is required for validation and harmonization purposes. This includes the analysis of the pure polymer particles and the validation of the respective measurement methods. In addition, there is the harmonization of different laboratories. On the other hand, sample preparation methods must be validated and harmonized with regard to their recovery and subsequent analysis in the respective matrices. For this purpose, we produce reference material candidates in the form of tablets with different mass fractions and particle numbers of polyethelene terephthalate. In the presentation first measurement results by µ-Raman, µ-FTIR, pyrolysis-GC-MS and TED-GC/MS will be presented.
T2 - SETAC Europe 34th Annual Meeting
CY - Seville, Spain
DA - 05.05.2024
KW - Reference material
KW - Microplastics
KW - PlasticTrace
PY - 2024
AN - OPUS4-60019
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wiesner, Yosri
A1 - Altmann, Korinna
T1 - MIKROPLASTIK – von der Probenvorbereitung bis zur Analytik
N2 - Der Vortrag beschreibt die Herausforderungen bei der Analyse von Mikroplastik inklusive Probennahme, Probenvorbereitung und Detektion. Es werden Ergebnisse aus dem BMBF-Projekt RUSEKU vorgestellt.
T2 - LABO-Anwendertag
CY - Online meeting
DA - 23.11.2021
KW - Mikroplastik
KW - TED-GC/MS
KW - Mikroplastik-Analytik
PY - 2021
AN - OPUS4-53829
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wiesner, Yosri
A1 - Eisentraut, Paul
A1 - Altmann, Korinna
T1 - Erfassung von Degradationsprodukten und Additiven sowie temperaturspezifische Pyrolyseprodukte mittels TED-GC/MS
N2 - Im der Präsentation werden, neben der Möglichkeit der Mikroplastikquantifizierung, auf weitere Anwendungsfelder der Methode TED-GC/MS eigegangen. Dies beinhaltet die Erfassung von Degradationsprodukten UV/O2 geschädigter Polymere und die Detektion von Additiven. Die Optimierung der Methode betreffend Messzeit und materialspezifischer Messanforderung sind ebenfalls Gegenstand.
T2 - Kolloquium Massenspektrometrie von Polymeren
CY - Berlin, Germany
DA - 09.05.2023
KW - TED-GC/MS
KW - Polymere
KW - Degradation
KW - Additive
PY - 2023
AN - OPUS4-57480
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wetzel, Annica
A1 - von der Au, Marcus
A1 - Dietrich, P. M.
A1 - Radnik, Jörg
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
T1 - The comparison of the corrosion behavior of the CrCoNi medium entropy alloy and CrMnFeCoNi high entropy alloy
JF - Applied Surface Science
N2 - This work presents the determination of the corrosion characteristics of CrCoNi (medium entropy alloy) and CrMnFeCoNi (high entropy alloy) in 0.1 M NaCl and 0.1 M H2SO4. The morphology and chemical composition of the oxide layers formed on CrCoNi and CrMnFeCoNi were comparatively analyzed by scanning Kelvin probe microscopy (SKPFM) and scanning electron microscopy (SEM) and supported with chemical analysis by means of inductively coupled plasma mass spectrometry (ICP-MS) and X-Ray photoelectron spectroscopy (XPS). The analysis of the 3p core level peaks showed that the oxide layer (native and after anodic passivation) on CrCoNi consisted mainly of Cr oxides, while the oxide layer on CrMnFeCoNi was primarily composed of a mixture of Cr and Fe oxides. In addition, XPS was utilized to assess the oxide layer thicknesses. These results were compared to the thicknesses obtained by means of electrochemical impedance spectroscopy (EIS), with both approaches yielding values up to about 4 nm depending on the electrolyte and the alloy. Cyclic polarization measurements indicated superior corrosion resistance of CrCoNi in both aqueous environments compared to CrMnFeCoNi, as well as to AISI 304 stainless steel.
KW - Medium entropy alloy
KW - High entropy alloy
KW - SKPFM
KW - XPS
KW - Passivation
KW - Corrosion
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-559902
DO - https://doi.org/10.1016/j.apsusc.2022.154171
SN - 0169-4332
VL - 601
SP - 1
EP - 10
PB - Elsevier B.V.
AN - OPUS4-55990
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wetzel, Annica
A1 - Morell, Daniel
A1 - von der Au, Marcus
A1 - Wittstock, Gunther
A1 - Ozcan, Ozlem
A1 - Witt, Julia
T1 - Transpassive Metal Dissolution vs. Oxygen Evolution Reaction: Implication for Alloy Stability and Electrocatalysis
T1 - Transpassive Metallauflösung vs. Sauerstoffentwicklung:
Auswirkungen auf Legierungsstabilität und Elektrokatalyse
JF - Angewandte Chemie International Edition
N2 - Multi-principal element alloys (MPEAs) are gaining interest in corrosion and electrocatalysis research due to their electrochemical stability across a broad pH range and the design flexibility they offer. Using the equimolar CrCoNi alloy, we observe significant metal dissolution in a corrosive electrolyte (0.1 M NaCl, pH 2) concurrently with the oxygen evolution reaction (OER) in the transpassive region despite the absence of hysteresis in polarization curves or other obvious corrosion indicators. We present a characterization scheme to delineate the contribution of OER and alloy dissolution, using scanning electrochemical microscopy (SECM) for OER-onset detection, and quantitative chemical analysis with inductively coupled-mass spectrometry (ICP-MS) and ultraviolet visible light (UV-Vis) spectroscopy to elucidate metal dissolution processes. In-situ electrochemical atomic force microscopy (EC-AFM) revealed that the transpassive metal dissolution on CrCoNi is dominated by intergranular corrosion. These results have significant implications for the stability of MPEAs in corrosion systems, emphasizing the necessity of analytically determining metal ions released from MPEA electrodes into the electrolyte when evaluating Faradaic efficiencies of OER catalysts. The release of transition metal ions not only reduces the Faradaic efficiency of electrolyzers but may also cause poisoning and degradation of membranes in electrochemical reactors.
N2 - Multi-Hauptelement-Legierungen (MPEAs) gewinnen in der Korrosions- und Elektrokatalyseforschung aufgrund ihrer elektrochemischen Stabilität über einen breiten pH-Bereich und der Vielfalt der möglichen chemischen Zusammensetzungen zunehmend an Interesse. In unseren Untersuchungen mit der äquimolaren CrCoNi-Legierung in einem sauren Elektrolyten (0.1 M NaCl, pH 2) beobachteten wir eine signifikante Metallauflösung, die mit der Sauerstoffentwicklungsreaktion (OER) im transpassiven Bereich einhergeht, obwohl in zyklischen Polarisationskurven keine Hysterese auftrat oder andere offensichtliche Korrosionsindikatoren vorlagen. In diesem Artikel wird ein Charakterisierungskonzept eingeführt, dass die Beiträge der OER und der Legierungsauflösung differenziert. Hierfür kommt die elektrochemische Rastermikroskopie (SECM) zum Nachweis des Beginns der OER und die quantitative chemische Analyse mit induktiv gekoppelter Massenspektrometrie (ICP-MS) und UV/Vis-Spektrometrie zur Aufklärung der Metallauflösungsprozesse zum Einsatz. Die elektrochemische In situ-Atomkraftmikroskopie (EC-AFM) zeigte, dass die intergranulare Korrosion der dominierende Mechanismus der transpassive Metallauflösung von CrCoNi ist. Diese Ergebnisse besitzen erhebliche Auswirkungen für die Beurteilung der Stabilität von MPEAs in Korrosionssystemen und der Stromausbeute von OER-Katalysatoren auf der Basis von MPEAs. Die Daten unterstreichen die Notwendigkeit der analytischen Bestimmung von Metallionen, die von MPEA-Elektroden freigesetzt werden. Die Freisetzung von Übergangsmetallionen verringert nicht nur die Stromausbeute von Elektrolyseuren, sondern kann zu einer Schädigung von Membranen in elektrochemischen Reaktoren führen.
KW - Transpassive dissolution
KW - Corrosion
KW - Multi-prinicpal element alloys (MPEAs)
KW - Passivation
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597045
DO - https://doi.org/10.1002/anie.202317058
SP - 1
EP - 8
PB - Wiley VHC-Verlag
AN - OPUS4-59704
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wetzel, Annica
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Rhode, Michael
T1 - Local corrosion properties of high/medium entropy alloys in aqueous environments
N2 - High and medium entropy alloys gained increasing academic and industrial interest as novel materials for engineering applications. This project is aiming to clarify and compare the general and local corrosion properties of high entropy alloy CrMnFeCoNi and medium entropy alloy CrCoNi in different aqueous environments. The focus lies on the local corrosion processes that result either from microstructural imperfections (inclusions, defects at grain boundaries etc.) in the base material or processing related changes in the microstructure and/or local composition.
The corrosion behavior of the alloys was monitored via potentiodynamic polarization experiments and the local corrosion characteristics were further investigated by means of scanning electrochemical microscopy (SECM). Their passivation behavior was analyzed in three different electrolyte systems (NaCl, H2SO4 and NaClO4; c = 0.1M). The characterization of the surface morphology and composition of the passive film was performed by means of atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy (SEM/EDX) and X-Ray photoelectron spectroscopy (XPS), respectively.
Considering long term corrosion effects, electrochemical work was supported with immersion tests and the analysis of corrosion products by SEM/EDX and XPS depth-profiling. Our results indicate that the medium entropy alloy CrCoNi has a significantly higher corrosion resistance in comparison to the high entropy alloy CrMnFeCoNi. The presentation will summarize some of our results on the mechanistical aspects of the observed high corrosion resistance.
T2 - EUROCORR 2020
CY - Online meeting
DA - 07.09.2020
KW - High Entropy Alloys
KW - Corrosion
KW - Medium Entropy Alloys
KW - Atomic Forc Microscopy
KW - Scanning Kelvin Probe Force Microscopy
KW - Potentiodynamic Polarization
PY - 2020
AN - OPUS4-53787
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wetzel, Annica
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Rhode, Michael
T1 - Corrosion Properties and Protective Oxide Film Characteristics of CrMnFeCoNi High Entropy Alloy and CrCoNi Medium Entropy Alloy
N2 - High and medium entropy alloys gained increasing academic and industrial interest as novel materials for engineering applications. This project is aiming to clarify and compare the general and local corrosion properties of high entropy alloy CrMnFeCoNi and medium entropy alloy CrCoNi in different aqueous environments. The focus lies on the local corrosion processes that result either from microstructural imperfections (inclusions, defects at grain boundaries etc.) in the base material or processing related changes in the microstructure and/or local composition.
The corrosion behavior of the alloys was monitored via potentiodynamic polarization experiments and the local corrosion characteristics were further investigated by means of scanning electrochemical microscopy (SECM). Their passivation behavior was analyzed in two different electrolyte systems (NaCl and H2SO4 c = 0.1M). The characterization of the surface morphology and composition of the passive film was performed by means of atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy (SEM/EDX) and X-Ray photoelectron spectroscopy (XPS), respectively. To analyze the semiconducting properties of the passive film Mott-Schottky analysis was conducted.
Considering long term corrosion effects, electrochemical work was supported with immersion tests and the analysis of corrosion products by SEM/EDX, ICP-MS and XPS depth-profiling. Our results indicate that the medium entropy alloy CrCoNi has a significantly higher corrosion resistance due to the higher concentration of chromium in comparison to the high entropy alloy CrMnFeCoNi. The presentation will summarize our results on the mechanistical aspects of the observed high corrosion resistance.
T2 - ISE Annual 72nd meeting
CY - Online meeting
DA - 29.08.2021
KW - High Entropy Alloys
KW - Aqueous Corrosion
KW - Medium Entropy Alloys
KW - Atomic Forc Microscopy
KW - Scanning Kelvin Probe Force Microscopy
KW - Potentiodynamic Polarization
KW - Electrochemical Impedance Spectroscopy
KW - ICP-MS
PY - 2021
AN - OPUS4-53789
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wetzel, Annica
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Rhode, Michael
T1 - Corrosion Properties and Protective Oxide Film Characteristics of CrMnFeCoNi High Entropy Alloy and CrCoNi Medium Entropy Alloy
N2 - High and medium entropy alloys gained increasing academic and industrial interest as novel materials for engineering applications. This project is aiming to clarify and compare the general and local corrosion properties of high entropy alloy CrMnFeCoNi and medium entropy alloy CrCoNi in different aqueous environments. The focus lies on the local corrosion processes that result either from microstructural imperfections (inclusions, defects at grain boundaries etc.) in the base material or processing related changes in the microstructure and/or local composition.
The corrosion behavior of the alloys was monitored via potentiodynamic polarization experiments and the local corrosion characteristics were further investigated by means of scanning electrochemical microscopy (SECM). Their passivation behavior was analyzed in three different electrolyte systems (NaCl, H2SO4 and NaClO4; c = 0.1M). The characterization of the surface morphology and composition of the passive film was performed by means of atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy (SEM/EDX) and X-Ray photoelectron spectroscopy (XPS), respectively.
Considering long term corrosion effects, electrochemical work was supported with immersion tests and the analysis of corrosion products by SEM/EDX and XPS depth-profiling. Our results indicate that the medium entropy alloy CrCoNi has a significantly higher corrosion resistance due to the higher concentration of Chromium in comparison to the high entropy alloy CrMnFeCoNi. The presentation will summarize our results on the mechanistical aspects of the observed high corrosion resistance.
T2 - EuroMat 2021
CY - Online meeting
DA - 12.09.21
KW - High Entropy Alloys
KW - Aqueous Corrosion
KW - Medium Entropy Alloys
KW - Atomic Forc Microscopy
KW - Scanning Kelvin Probe Force Microscopy
KW - Potentiodynamic Polarization
KW - Electrochemical Impedance Spectroscopy
KW - ICP-MS
PY - 2021
AN - OPUS4-53790
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wetzel, Annica
A1 - Özcan Sandikcioglu, Özlem
A1 - Witt, Julia
A1 - Rhode, Michael
T1 - Corrosion Properties and Protective Oxide Film Characteristics of CrMnFeCoNi High Entropy Alloy and CrCoNi Medium Entropy Alloy
N2 - High and medium entropy alloys gained increasing academic and industrial interest as novel materials for engineering applications. This project is aiming to clarify and compare the general and local corrosion properties of high entropy alloy CrMnFeCoNi and medium entropy alloy CrCoNi in different aqueous environments. The focus lies on the local corrosion processes that result either from microstructural imperfections (inclusions, defects at grain boundaries etc.) in the base material or processing related changes in the microstructure and/or local composition.
The corrosion behavior of the alloys was monitored via potentiodynamic polarization experiments and the local corrosion characteristics were further investigated by means of scanning electrochemical microscopy (SECM). Their passivation behavior was analyzed in three different electrolyte systems (NaCl, H2SO4 and NaClO4; c = 0.1M). The characterization of the surface morphology and composition of the passive film was performed by means of atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy (SEM/EDX) and X-Ray photoelectron spectroscopy (XPS), respectively.
Considering long term corrosion effects, electrochemical work was supported with immersion tests and the analysis of corrosion products by SEM/EDX and XPS depth-profiling. Our results indicate that the medium entropy alloy CrCoNi has a significantly higher corrosion resistance due to the higher concentration of Chromium in comparison to the high entropy alloy CrMnFeCoNi. The presentation will summarize our results on the mechanistical aspects of the observed high corrosion resistance.
T2 - EUROCORR 2021
CY - Online meeting
DA - 20.09.2021
KW - High Entropy Alloys
KW - Aqueous Corrosion
KW - Medium Entropy Alloys
KW - Atomic Forc Microscopy
KW - Scanning Kelvin Probe Force Microscopy
KW - Potentiodynamic Polarization
KW - Electrochemical Impedance Spectroscopy
KW - ICP-MS
PY - 2021
AN - OPUS4-53791
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wetzel, Annica
A1 - Morell, D.
A1 - Ozcan, Ozlem
A1 - Witt, Julia
T1 - The Interplay of Anodic Passivation and Oxygen Evolution of Medium Entropy Alloys in Aqueous NaCl Electrolytes at Different pH
N2 - Due to their favorable mechanical and anti-corrosion properties, medium entropy alloys (MEA) are of high academic and industrial interest as novel materials for engineering and catalytic applications. Previous studies on general corrosion behavior indicate high current densities at high anodic potentials for MEAs. Further investigations of the underlying transpassive dissolution and local corrosion behavior remain scarce.
To understand the passivation behavior of MEAs CrCoNi and FeCrNi at high anodic potentials, the mechanisms of transpassive dissolution and the oxygen evolution reaction were investigated in this project. Scanning electrochemical microscopy (SECM) was applied in the interrogative mode for the detection of evolving metal species and oxygen. By means of ICP-MS analysis, dissolved metal species were quantified to provide a fundamental understanding on the transpassive dissolution. As the oxygen evolution reaction (OER) may contribute a large percentile to the observed current at high anodic potentials, SECM measurements were employed to analyze the onset of the OER. Potentiodynamic, potentiostatic and chronoamperometric techniques as well as different electrolytes were used to induce precisely controlled corrosion loads during the SECM experiments and for the ICP-MS analysis. Macroscopic corrosion properties of the alloys, electrical and chemical properties of the passive films were studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and X-Ray Photoelectron Spectroscopy (XPS), respectively.
Finally, the analysis of the corrosion morphology and the potential of the surface before, during and after passivity breakdown was carried out by means of in-situ atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM). The presentation will summarize our results on the interplay of anodic passivation and oxygen evolution of MEAs in aqueous NaCl electrolytes.
T2 - MRS Spring 2023
CY - San Francisco, California, USA
DA - 10.04.2023
KW - Chemically Complex Materials
KW - CCMat
KW - Corrosion
PY - 2023
AN - OPUS4-59405
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wetzel, Annica
A1 - Yesilcicek, Yasemin
A1 - Witt, Julia
A1 - Ozcan, Ozlem
T1 - Old materials, new life: Using diffusion-controlled synthesis for discovery of novel alloy systems
N2 - Multi principal element alloy (MPEAs) concept allows us to rethink how we develop application-tailored, sustainable materials. The vast composition space leads to nearly indefinite material combinations and will facilitate finding Pareto optimal materials with lower CO2 footprint and avoidance of critical minerals as design criteria. To probe this large compositional space efficiently, the use high-throughput screening methods is inevitable. Diffusion-controlled synthesis of gradient materials is the optimal technique for screening complex compositional materials that would otherwise require comprehensive modelling or experimental efforts.
In this study, we have used a series of diffusion couples of pure metals and alloys with the aim to create a materials library with correlated data on composition and microstructure. With future recycling prospects in mind, and possible applications of Cu containing alloys in electrocatalytic carbon dioxide reduction and antimicrobial alloys we have generated diffusion couples of brass (Cu63Zn37) and bronze (Cu89Sn11) with either pure metals (Fe, Ni, etc.) or with binary or ternary alloys (FeNi, FeNiCr etc.). For different diffusion times and temperatures, we calculated diffusion constants for the material combinations. Following a detailed characterisation of the gradient materials, we have investigated general and local corrosion properties, electrocatalytic activity for oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CRR) as well as mechanical properties (hardness, elastic modulus) on single-phase alloys synthesized in bulk by means of vacuum arc-melting based on the selected local compositions.
In most cases, due to the short diffusion times, the contact between the diffusion couples lead to two separate diffusion zones and thus, different alloy families on both sides. Especially with ternary alloys, interesting selective diffusion processes and unexpected repulsion effects were observed. The presentation will provide an overview of the gradient materials with a focus on the functional properties of single-phase alloy families derived from them.
T2 - MRS Spring 2023
CY - San Francisco, California, USA
DA - 10.04.2023
KW - Chemically Complex Materials
KW - CCMat
KW - Corrosion
KW - Electrocatalysis
PY - 2023
AN - OPUS4-59406
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weise, Matthias
A1 - Hertwig, Andreas
A1 - Beck, Uwe
T1 - Scanning White Light Interference Microscopy - Measurement of Topometry and Layer Thickness
N2 - 3D coherence scanning interferometry (CSI) is anoptical, non-contact and rapide measurement technique using a defined bandwidth of white light at normal incidence. White light interference microscopy (WLIM) providest here-dimensional surface topometry data up to a resolution of 0.4 µm lateral and 0.1 nm vertical. Three operating modi, surface, films and advanced films, enable measurements of step heights, roughness, wear volume, cone angle, surface pattern and layer thickness. Traceability to SI system is ensured by certified standards (PTB/NIST) within a DAkkS DIN EN ISO/IEC 17025:2018 accredited lab.
T2 - EFDS, V2019, Vakuum und Plasma, WS 4, Beschichtungen für Werkzeuge & Bauteile
CY - Dresden, Germany
DA - 08.10.2019
KW - DIN EN ISO/IEC 17025:2018
KW - Certified standards
KW - White light interference microscopy(WLIM)
KW - 3D coherence scanning interferometry (CSI)
KW - Topometry
PY - 2019
AN - OPUS4-49323
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weigert, Florian
A1 - Müller, A.
A1 - Häusler, I.
A1 - Geißler, Daniel
A1 - Skroblin, D.
A1 - Unger, Wolfgang
A1 - Radnik, Jörg
A1 - Resch-Genger, Ute
T1 - Combining HR‑TEM and XPS to elucidate the core–shell structure of ultrabright CdSe/CdS semiconductor quantum dots
JF - Scientific reports
N2 - Controlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the applicationrelevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.
KW - Photoluminescence
KW - Single particle
KW - Microscopy
KW - Particle architecture
KW - Thickness
KW - SAXS
KW - Shell
KW - XPS
KW - TEM
KW - Semiconductor
KW - Quantum dot
KW - Photophysics
KW - Quantum yield
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-517911
DO - https://doi.org/10.1038/s41598-020-77530-z
VL - 10
IS - 1
SP - 20712
PB - Springer Nature
AN - OPUS4-51791
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H. R.
T1 - Sn(II)2-ethylhexanoate-catalyzed polymerizations of L-lactide in solution – Solution grown crystals of cyclic Poly(L-Lactide)s
JF - Polymer
N2 - L-lactide (LA) was polymerized in toluene by means of neat tin(II) 2-ethylhexanoate (SnOct2). Concentration, time and temperature were varied. The isothermally crystallized polyLAs (PLA) were characterized in the virgin state with regard to topology, molar mass, melting temperature (Tm), crystal modification, high or low Tm morphology, crystallinity and crystal thickness. Even a small amount of solvent favored cyclization relative to polymerization in bulk, so that cyclic polylactides were obtained at 115 ◦C and even at 95 ◦C. At all temperatures the α-modification of PLA was obtained along with crystallinities up to 90%. With 6 M solution the high Tm morphology with Tm’s > 190 ◦C was obtained at 115 ◦C. The crystal thickness of crystallites grown from solution at 115 ◦C was on the average 10–20% higher than that of PLA polymerized in bulk. At a polymerization temperature of 75 ◦C cyclization was incomplete and fewer perfect crystallites were formed. A new hypothesis for the crystal growth of cyclic polyLAs is proposed.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
KW - Polymerization
PY - 2022
DO - https://doi.org/10.1016/j.polymer.2022.125142
SN - 0032-3861
VL - 255
SP - 1
EP - 9
PB - Elsevier
CY - Oxford
AN - OPUS4-55283
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H. R.
T1 - Alcohol-initiated and Tin(II) 2-ethylhexanoate-catalyzed polymerization of L-lactide in bulk – About separate crystallization of cyclic and linear Poly (L-lactide)s
JF - Polymer
N2 - Alcohol-initiated ROPs of L-Lactide were performed at 140 ◦C in bulk with variation of the initiator/catalyst ratio and time. Lower ratios favor the formation of cycles which upon annealing display a change of the MALDI mass peak distribution towards a new maximum with a “saw-tooth pattern” of the mass peaks representing the cycles.
Such a pattern was not observed for the mass peak of the linear chains. The coexistence of these patterns indicate that linear and cyclic poly (L-lactide)s (PLA) crystallize in separate crystals, and that the crystallites of the cycles are made up by extended rings. High Tm and ΔHm values confirm that these extended-ring crystallites represent a thermodynamically optimized form of PLA. Experiments with preformed cyclic and linear PLAs support this interpretation.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
KW - Polymerization
PY - 2023
DO - https://doi.org/10.1016/j.polymer.2023.126355
VL - 285
IS - 126355
SP - 1
EP - 9
PB - Elsevier Ltd.
AN - OPUS4-58355
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -