6 Materialchemie
Filtern
Erscheinungsjahr
- 2019 (164) (entfernen)
Dokumenttyp
- Vortrag (164) (entfernen)
Sprache
- Englisch (124)
- Deutsch (39)
- Mehrsprachig (1)
Referierte Publikation
- nein (164)
Schlagworte
- Mikroplastik (17)
- TED-GC-MS (16)
- Nanoparticles (10)
- Microplastics (9)
- Analytik (8)
- Surface functionalization (8)
- Atomic Force Microscopy (AFM) (6)
- Corrosion (6)
- Laser-induced periodic surface structures (LIPSS) (6)
- Nanocomposites (6)
Organisationseinheit der BAM
- 6 Materialchemie (164)
- 6.6 Physik und chemische Analytik der Polymere (59)
- 6.1 Oberflächen- und Dünnschichtanalyse (35)
- 6.3 Strukturanalytik (29)
- 6.2 Material- und Oberflächentechnologien (26)
- 6.7 Materialsynthese und Design (17)
- 7 Bauwerkssicherheit (9)
- 4 Material und Umwelt (8)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (8)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (6)
Eingeladener Vortrag
- nein (164)
Formation of interphases between inorganic nanofillers and thermoplastic matrices are usually correlated to short-range interactions which does not exceed more than tens of nanometers away from the surface of the filler. Nevertheless, in nanocomposites with thermosetting matrices, the effect of nanofillers on the properties of the matrix is not limited to the immediate vicinities, but a long-range property alteration of the bulk polymer may be observed. The interaction between nanofillers and the polymer can disturb the curing reaction and alters the chemical, physical and mechanical properties of the polymer network in the matrix phase. In our studies, we aim to investigate short and long-range interphases of a nanocomposite system consisting of a thermosetting matrix (DGEBA) filled with an inorganic nanoparticle (boehmite). For this purpose, a combination of atomic force microscopy (AFM)-based approaches is implemented. Scanning kelvin probe microscopy (SKPM) was used to map the compositional contrast and the interphase with different electrical properties than the bulk. The mechanical properties of the interphase were probed by high resolution intermodulation AFM. (ImAFM). Furthermore, infrared spectroscopy AFM (AFM-IR) is used to investigate the chemical structure of the matrix at different distances from the nanoparticle. SKPM and (AFM-IR) measurements both show a long-range (to 10 µm) effect of boehmite on the chemical structure and surface potential of the bulk epoxy, respectively, whereas ImAFM force measurements reveals a short-range mechanical interphase between the filler and the matrix. The AFM-IR demonstrated the existence of unreacted anhydride hardener at the interphase. This indicates the preferential absorption of anhydride on the surface of boehmite. The consequence of such a selective interaction between the inorganic filler and the epoxy components is disturbance of the epoxy-hardener stoichiometric ratio, the curing mechanism. and the alteration of bulk properties of the matrix.
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.
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.
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.
Using magnetic materials for energy conversion as an example, this lecture shows how X-ray tomography investigations can contribute to structure elucidation in composites and solid samples. The components are tested non-destructively in order to characterize cracks, pores and other defects and their influence on the functional properties three-dimensionally and in good time in the life cycle of the material. If you combine microtomography with other methods of magnetic material characterization, you can make unique statements about the structure and the functional properties.
Using magnetic materials for energy conversion as an example, this lecture shows how X-ray tomography investigations can contribute to structure elucidation in composites and solid samples. The components are tested non-destructively in order to characterize cracks, pores and other defects and their influence on the functional properties three-dimensionally and in good time in the life cycle of the material. If you combine microtomography with other methods of magnetic material characterization, you can make unique statements about the structure and the functional properties.
Perhaps due in no small part to its historical mystique, mechanochemistry has been shrowded in relative obscurity for quite some time. The successes of mechanochemistry in organic synthesis have often been curtailed by a fundamentally limited mechanistic understanding. Lately, however, the community has made great strides towards understanding the fundamentals, as well as large steps forward regarding industrially significant scale-up via twin-screw extrusion. A variety of recent work has traded in some of mechanochemistry’s mystique for simple, straight-forward chemical guidelines.
Functional materials for energy conversion are important technology drivers needed for the implementation of low carbon energy. Therefore, researchers commonly focus on improving the intrinsic properties of a functional material. However, for applications, the extrinsic properties are at least as important as the intrinsic ones. Consequently, it is important to investigate and understand the external and internal structure of semi-finished products and especially defect dependent properties. The extrinsic properties may change during application and the life cycle of the material as well as through processing and molding steps.
Our studies show how X-ray tomographic (XCT) investigations can contribute to structure investigations in composites and massive samples using the example of magnetic materials for energy conversion. The components are tested non-destructively in 3D in order to localize and characterize cracks, pores, inclusions as well as other defects and their influence on the functional properties and also “in-time” during the life cycle of the material. Exsitu and in-situ experiments performed with non-destructive XCT are predestinated to follow damaging mechanisms of materials under certain load conditions, atmospheres or liquids, e.g. went through several working cycles of a functional material. By combining microtomography with other methods of magnetic and classical material characterization, unique statements about the structure and the functional properties can be made.
From the applications point of view, sometimes complex, three-dimensional geometries are needed to fully exploit the functional properties of the materials, e.g. to ensure a high surface area for heat exchange. Since many functional materials are brittle and difficult to form, shaping is often a big challenge. In principle, additive manufacturing processes offer the possibility to produce complex, porous components from poorly formable alloys.
If all stages of additive manufacturing are accompanied by X-ray tomographic imaging, the process of finding the optimal parameters for material processing can be significantly accelerated.
Based on the quality control of the initial powder material used and also investigations of the shape and arrangement of defects within the molten structure and their relationship with the melting path scanning strategy, Xray tomography has proven to be an ideal tool for additive manufacturing, even for functional materials. Overall, tomographic methods are important tools for the development of functional materials to application maturity.
This talk was given within the scope of the SIMS-22 conference in October 2019 in Kyoto (Japan). It deals with the surface analytical investigation of nanoparticles by PCS-assisted ToF-SIMS. This technique is applicable to core-shell nanoparticles, in order to distinguish a complete encapsulation from an incomplete encapsulation of the core by the shell material. Furthermore, the depletion process of organic nanoparticle coatings caused by UV-weathering is investigated. Finally, the significance of grouping studies for nanomaterials research and risk assessment is demonstrated.
It was found for inorganic/polymer nanocomposites that a so-called Rigid Amorphous Phase (RAF) is formed in the interfacial region by adsorption of polymer segments onto the nanoparticles. The segmental dynamics of RAF is expected to be altered, as compared to the pure matrix, which might percolate into the entire system, affecting the overall nanocomposite properties. Here, the structure and molecular mobility of epoxy-based PNCs with different nanofillers (layered double hydroxide and boehmite) was studied by a combination of calorimetric and X-Ray scattering techniques. Temperature modulated DSC (TMDSC) showed that depending on the nanofiller, RAF can reach up to 40 wt % of the system or, on the contrary, the overall mobility of the matrix might increase due to the presence of particles. Such contrasting results, including the high amount of RAF, which was never shown before for epoxy-based PNCs, emphasize the importance of interfaces. Additionally, glass transition and glassy dynamics were investigated by a novel technique, Flash DSC (heating rates up to 10 kK/s) employed for the first time to a thermosetting system and electrospun fibers, which did not result in their degradation. It was used to study both the vitrification kinetics and glassy dynamics of the PNCs, for instance further confirming the presence of RAF and its impact on the overall material properties.
Das Fügeverfahren Kleben bietet viele Vorteile, wie z.B. das Verbinden unterschiedlicher Materialklassen, geringe thermische Belastung (und damit ggf. verbundene Strukturveränderung/-schwächung) der Fügeteile und eine Lastverteilung über den gesamten Fügebereich. Die Auswahl an verfügbaren Klebstoffen und Vorbehandlungsoptionen sind dabei - wie die Applikationen auch - vielfältig. Es werden vier Applikationsbeispiele zu Referenzklebverbunden aus Edelstahl, zur Plasmaaktivierung von Niedrigenergie-Polymeren, zur Bestimmung der Haftfestigkeit von Lackierungen auf GFK und zur Wirkung von Primern vorgestellt. Einige Polymere weisen z.B. Eigenschaften auf, die eine Herstellung von festen und dauerhaft beanspruchbaren Kleb-verbindungen erschweren. Im Allgemeinen geht dies mit geringen Oberflächenenergien einher. Mittels Oberflächenvorbehandlung, z.B. durch Plasmafeinreinigung bzw. Plasmaaktivierung, können die Grenzflächen solcher Polymere - bezogen auf die Eignung als Fügeteile (Klebfestigkeit) oder als Substrat (Haftfestigkeit) – optimiert bzw. die Oberflächenenergie erhöht werden. Schnelle, zuverlässige und statistisch abgesicherte Prüfverfahren zur Ermittlung von Verbund-eigenschaften sind dabei unverzichtbar.
Challenges in Traceable Size Measurement of Non-Spherical, Non-Monodisperse Nanoparticles - nPSize
(2019)
Size measurement of nanoparticles (NP) becomes a challenging analytical problem when non-spherical shapes must be traceably measured. However, most industrial NPs have irregular shapes and broad size distribution making it often more complex to follow European regulatory to identify a material as a nanomaterial according to which accurate measurement of the smallest dimension and its size Distribution is necessary.
The European research project nPSize - Improved traceability chain of nanoparticle size measurements aims to fill this gap by developing potential non-spherical reference nanoparticles, measurement procedures and physical modelling to improve the traceability chain, comparability and compatibility for NP size measurements between different methods. Therefore, new model NP with well-controlled shape has been synthesized and are supposed to be systematically characterized using the traceable methods scanning/transmission electron microscopy, atomic force microscopy and small angle X-ray scattering.
Following NP candidates are under investigation with respect to their homogeneity and stability: (i) titania nanoplatelets (10-15 nm thickness x 50-100 nm lateral), (ii) titania bipyramides (~60 nm length x 40 nm width), (iii) titania acicular particles (100 nm length x 15-20 nm width; aspect ratio 5.5/6), (iv) gold nanorods (~10 nm width x 30 nm length), and (v) gold nanocubes (~55 nm x 55 nm x 55 nm). In addition, sample preparation procedures as well as measurement analysis procedures with evaluation of appropriate measurands and descriptors for each material class and method are being developed to support standardization. To underpin the traceability of the size measurement of nonspherical NP, physical modelling of the signals in e.g. electron microscopy techniques will be used and in combination, the implementation of machine learning is aimed to facilitate measurement Analysis procedures, especially regarding the accurate thresholding/segmentation of the NPs.zeige mehr
Nowadays, different nanoparticles have been developed for commercial applications. However, since data on toxicity are barely available, their increasing application in cosmetic products, food and their release in the environment might cause severe problems. Since a range of physical, chemical, and biological characteristics of NPs are closely related to particle size and surface functionalization, precise separation and surface groups quantification is essential to acquire an in-depth understanding of their properties.
In this work, the performance of asymmetrical flow field flow fractionation (AF4) and capillary electrophoresis (CE) for the separation of nanoparticles (NPs) with different sizes, coatings, and coating densities was investigated and optimized.
For the first time, a two-dimensional off-line hyphenation of both techniques (AF4-CE) was developed. The results clearly demonstrated, that AF4-CE hyphenation can significantly improve the separation resolution and reduce the peak broadening in CE. Also, for the first time, CE was employed to determine the coating density of NPs and the results were in good agreement with the values acquired with conductometric titration.
Die zunehmenden Nachweise von Kunststoffen in verschiedenen Umweltmedien erfahren in den letzten Jahren weltweit ein zunehmendes wissenschaftliches, gesellschaftliches und politisches Interesse. Besondere Aufmerksamkeit erfahren Kunststoffpartikel von 1-1.000 µm sogenanntes Mikroplastik. Es wurde mittlerweile in Wasser, Böden, Luft und Biota nachgewiesen. Obwohl die Wirkungen auf die natürlichen Umweltfunktionen noch unklar sind und kontrovers diskutiert werden, ist allein durch die ubiquitäre Präsenz eine systematische Erfassung von Eintragsquellen und Verbleib der Partikel über alle Umweltmedien notwendig, um Maßnahmen zur Reduktion der Einträge zu veranlassen.
Für eine zuverlässige Erfassung sind medienübergreifende Verfahren zu entwickeln, welche die drei analytischen Schritte, Probennahme, Probenaufbereitung und Detektion beinhalten. Die Verfahren adressieren unterschiedliche Zielgruppen, welche verschiedene analytische Informationen fordern. Für die akademische Bewertung werden Verfahren mit hohem analytischen Aufwand favorisiert, welche möglichst detaillierte Information über Partikelsorte, -größe, -zahl und -oberflächenbeschaffenheit geben. Im Gegensatz dazu, fordern Anwender aus der Praxis schnelle und einfache Monitoring Verfahren, welche die Bestimmung eines Massengehaltes, bzw. eines Grenzwertes zulassen. Allen ist gemeinsam, dass ein hoher interdisziplinärer Anspruch besteht, der sowohl technische Voraussetzungen zur repräsentativen Probennahme und die Limitationen von Detektionsverfahren berücksichtigt, als auch die Fachkompetenz von Biologen, Umweltwissenschaften, Analytiker und Polymerwissenschaftler einschließt.
Verfahren zum Mikroplastiknachweis müssen auch verschieden Proben mit sehr unterschiedlichen Gehalten an natürlicher Matrix gerecht werden. So müssen allein für Wasser Verfahren entwickelt werden, die Mikroplastik verschiedener Form (sphärische Partikel, komplexe Bruchstücke, Fasern) aus Medien mit sehr variablen Partikelanteil (u.a. Trinkwasser, Oberflächenwasser, Abwasser) repräsentativ erfassen sowie schnell und kostengünstig sind – einschließlich der notwendigen Probenaufbereitung. Die jeweiligen Detektionsverfahren müssen z.B. einzelne Partikel oder integrale Gehalte über drei Dekadenklassen für thermoplastische und insbesondere auch elastomere Partikelsorten erfassen können.
Polymers of intrinsic microporosity (PIMs) have recently emerged as novel materials for a broad range of high-performance applications from gas separation to electronic devices. The very rigid, contorted polymer chains show only limited molecular mobility and therefore pack inefficiently giving rise to intrinsic microporosity with pore sizes generally smaller than 1 nm resulting in BET surface areas larger than 700 m2/g. Using conventional thermal analysis techniques, no glass transition temperature (Tg) of PIMs could be unambiguously detected up to now. Employing fast scanning calorimetry (FSC) based on a one chip sensor, decoupling the time scales responsible for the glass transition and the thermal decomposition is a reliable strategy to overcome this limitation. The FSC device is capable to heat and cool a small sample (ng-range) with ultrafast rates of several ten thousand K/s. Evidence of a glass transition is obtained for a series of PIMs with different chain rigidities. Local small-scale fluctuations are held responsible for the glass transition of highly rigid PIMs rather than segmental motions as in conventional polymers.
Crystalline molecular materials with mechanical flexibility are promising for technological development. This is particularly true for the development of advanced materials with optoelectronic and biomedical applications. While a growing number of mechanically flexible crystalline molecular materials are being reported,1 they remain scarce. At present, most discoveries are serendipitous, as limited design strategies are currently known. Amongst these strategies Desiraju et. al. suggested that elastic materials must contain herringbone structures.2 For plastic crystals, the so-called ‘shape-synthon’ strategy has been developed, in which weak non-covalent interactions are introduced into structures to facilitate mobility of molecules.3 This includes formation of slip planes. Generally, these models have performed very well at predicting and rationalizing the mechanical properties of new materials. Recently, however, a family of one-dimensional covalent networks (coordination polymers; CPs) has been described, which show mechanical elasticity. With drastically different structural chemistry, these systems do not seem to adhere to the currently established rules. Herein, we present the first such system: a plastically bendable crystal of a 1D CP, [Zn(-Cl)2(3,5-Cl2Py)2]n (where 3,5-Cl2Py = 3,5-dichloro pyridine). This CP crystallizes in a tetragonal, and can therefore be bent over two major faces to acute angles without fracturing. We conducted bending and indentation experiments to quantify the mechanical properties of the CP crystal. This was complimented by Vibrational (Raman and Terahertz) spectroscopy and theoretical calculations for deeper understanding of molecular level structural deformation.
Biocide mitigation strategies of microbiologically influenced corrosion (MIC) in the oil and gas industry have been primarily used to eliminate the growths of sulfate-reducing microorganisms (SRM). However, methanogenic Archaea (MA) can also be highly corrosive by using iron as an electron source for methanogenesis. Because of the fundamental physiological differences between archaea and bacteria, responses of MA towards SRM-specific biocides cannot be deduced using SRM. Due to the lack of information available on the effect of biocides on corrosive MA, we selected THPS, glutaraldehyde, nitrate and perchlorate to compare against corrosive SRM.
Preliminary results showed that at low concentrations of THPS (0-10 ppm), growth of MA was not affected, methane production and corrosion rates (0.1 mm/yr) were comparable between the different THPS concentrations. On the contrary, the SRM strain showed decreased corrosion rates (0.18 mm/yr to 0.03 mm/yr) with increasing THPS concentrations. Further corrosion tests including electrochemical measurements of different biocides on the growth of MA and SRM will be conducted. Such knowledge not only provide important insights on the physiological response of MA to biocides but also contribute to more effective mitigation strategies that can be both economic and environmentally beneficial.
Bacterial biofilms have the capacity to develop and thrive in virtually all circumstances and surfaces, even in the most challenging environmental conditions. The pervasive and recalcitrant existence of biofilms renders them to be a significant safety risk and economical encumbrance in a wide array of industries and technologies, and therefore is a priority area of research.
It is essential to develop an improved understanding of the mechanisms implicated during biofilm formation, such as in the case of the diffusion of bacterial-secreted extracellular electron transporters, which are purported to play an important role during biocorrosion by exoelectrogenic bacteria. Hence, a fundamental understanding of electron transfer mechanisms between bacteria and extracellular electron acceptors will contribute insight to our understanding of charge transport and chemistry at the biofilm – external insoluble electron acceptor interface.
In the present work, Attenuated Total Reflection - Fourier transform-infrared (ATR-FTIR) spectroscopy has been coupled to electrochemical techniques for the nondestructive, in situ spectro-electrochemical monitoring of biofilms in real-time. Shewanella sp. have been selected for this investigation due to their adaptable exoelectrogenic respiratory capacities and their notable ability to reduce metals via several different mechanisms of extracellular electron transfer mechanisms, including self-secreted flavin shuttles. Gold-thin film model substrates have been used due to their inert nature and for their ability to permit precise manipulation of the substrate surface polarization. Additionally, hydrogels comprised of calcium cross-linked alginate have been used to mimic the architectural features of extracellular polymeric substances which are integral to a bacterial biofilm, to allow the study of electron-transporting flavin molecules in an artificial biofilm. The results will demonstrate patterns of diffusion, akin to how flavins would diffuse in a naturally occurring biofilm, and how polarization affects this process. Furthermore, insight will be gained on how the redox behavior of flavins can influence the development and evolution of a biofilm.
This interdisciplinary approach should shed light on bacterial electron transfer mechanisms which could contribute towards emerging technologies which seek to better understand such mechanisms for novel antifouling strategies, renewable energies, and bioremediation.
Microbiologically induced corrosion due to bacterial biofilms causes several problems in industrial systems, technical applications and in medicine. Prior to the formation of a biofilm on a substrate, planktonic cells attach on the surface. Hence, the properties of the surface play a key role in biofilm formation and are of great importance for the development of strategies to prevent bacterial attachment and biofilm formation.
This project aims at clarifying to which extent surface micro-/nanostructuring and chemical functionalization affects bacterial attachment and whether a synergistic combination of the two can be used to control bacterial adhesion. To answer these questions, model surfaces with regular patterns of 5-10 micrometers in size have been prepared, which provide distinct zones differing in terms of their chemistry or nano-roughness. This was achieved by micro contact printing of self-assembled monolayers with different functional groups and deposition of patterned ZnO nanorod arrays for studying the effect of surface chemistry and morphology, respectively. Typical contrasts studied were combinations of positively/negatively charged, hydrophobic/hydrophilic or flat/rough.
The attachment behavior of bacteria on tailored surfaces were studied in a flow chamber as a function of time. The strain Pseudomonas fluorescens SBW25 was chosen as a model organism. DNA-intercalating dyes such as Syto9 have a high affinity to adsorb on ZnO nanorods. To overcome this limitation a genetic modification was performed by introducing a gene which expresses a green fluorescent protein in P. fluorescens SBW25 enabling the quantitative evaluation of the flow chamber studies by means of fluorescence microscopy. Further analysis of the attachment behavior was performed by means of scanning electron microscopy.
The presentation will summarize the results of our systematic study on the role of individual parameters on bacterial attachment and highlight synergistic combinations, showing an inhibition or enhancing effect. As the investigations with model substrates enable a precise control of the surface parameters, this approach can be applied to different microorganisms and material systems to achieve a correlative description of bacterial adhesion on solid surfaces.
Oxidation effects on the functionality and formation of laser-induced periodic surface structures
(2019)
In the last decades, the formation of laser-induced periodic surface structures (LIPSS) has been widely studied, not only to stablish a general understanding of the main mechanisms present during the irradiation with ultrashort laser pulses, but also to identify the main processing parameters for its fabrication on various technical materials. However, an important and almost always present effect that is typically set aside is the material oxidation during or after the laser processing. Usually, this leads to optical, chemical, structural and mechanical alterations that are seldomly studied in detail. Therefore, in this work we present a study that includes the formation of LIPSS on Ti6Al4V alloy for tribological applications were different oxidations layers are involved.
The material characterization using different techniques, such as energy dispersive X-ray analyses (EDX), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy (µ-RS), and depth-profiling Auger electron microscopy (AEM), and other techniques, confirms the formation of a non-negligible superficial oxide layer – strongly dependent on the specific processing parameters. We perform tribological experiments on laser irradiated samples oxidized by alternative ways to have a comparison on its friction performance. The obtained results show significant differences that depend directly on the thickness and the quality of the oxidized layer. This may open a fertile research area until now barely explored with clear impact on LIPSS based applications.
This presentation reviews current and expected developments in the field of laser-induced periodic surface structures (LIPSS, ripples). These surface nanostructures are a universal phenomenon and can be generated on almost any material by irradiation with intense linearly polarized radiation. LIPSS are formed in a “self-ordered” way and are often accompanying laser material processing applications. The structures can be produced in a single-step process and enable surface functionalization through the adaption of optical, mechanical and chemical surface properties. Their spatial periods typically range from several micrometers down to less than 100 nanometers, exhibiting a clear correlation with the polarization direction of the laser radiation used. Various types of LIPSS have been classified, relevant control parameters were identified, and material specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics, through time-resolved optical experiments and theoretical simulations. Special attention will be paid to a comparison of the currently available formation theories for LIPSS with a discussion of their respective strengths and weaknesses. Currrently explored applications featuring surface functionalization in the fields of optics, surface wetting, medicine, and tribology will be discussed.
This presentation reviews the current state in the field of Laser-induced Periodic Surface Structures (LIPSS). These surface nanostructures are a universal phenomenon and can be generated on almost any material by irradiation with intense linearly polarized laser radiation. LIPSS are formed in a “self-ordered” way and are often accompanying material processing applications. They can be produced following a single-step process and enable surface functionalization through the adaption of optical, mechanical and chemical surface properties. Their structural sizes typically range from several micrometers down to less than 100 nanometers exhibiting a clear correlation with the polarization direction of the laser radiation. Various types of surface structures are classified, relevant control parameters are identified, and their material specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics, through time-resolved optical experiments and theoretical simulations. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the femtosecond to picosecond range. During the past years significantly increasing industrial and research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical, biological, or chemical surface properties. In this contribution the mechanisms of formation and current trends and applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting properties, the mimicry of the natural texture of animals, the tailoring of surface colonization by bacterial biofilms, the advancement of leadless medical pacemakers, and the improvement of the tribological performance of nanostructured metal surfaces.
In arid sun-exposed environments, rock-inhabiting fungi dominate microbial communities on rock surfaces. Fungi are known to enhance rock weathering, although the exact mechanisms are not completely understood. These natural processes can be simulated by reproducible experimental systems. Particularly attractive are genetically amenable rock-weathering fungi, where certain traits can be knocked-out to identify weathering-relevant functions. Here, we studied the effect of the rock-inhabiting fungus Knufia petricola A95 and its melanin-deficient mutant (ΔKppks) on the weathering of a Fe-bearing olivine. We examined the olivine dissolution kinetics and looked at the olivine-fungus interface. For the former we inoculated olivine powder with the fungus in batch and mixed flow reactors and analysed the medium solution by ICP-OES, for the latter biofilm-covered olivine sections from flow-through reactors were analysed by FIB-TEM.
In general olivine dissolution was lower when olivine was incubated without fungi: the abiotic olivine dissolution rates were lowest and the surface of the abiotically reacted olivine sections showed no etching. Various chemical analyses show Fe (oxyhydr)oxide precipitation on top of the abiotically reacted olivine, indicating its role in inhibiting olivine dissolution. Both the wild type (WT) and ΔKppks solubilised and bound significant amounts of Fe released by olivine dissolution. Fe (oxyhydr)oxide precipitation was thus reduced, explaining the enhanced olivine dissolution in their presence. Particularly efficient at preventing Fe precipitation were attached WT cells: the inhibition of olivine dissolution almost completely disappeared. The attachment capacity of the WT is most likely caused by the production of WT-specific extracellular polymeric substances. Our presented experimental systems allowed the precipitation of Fe (oxyhydr)oxides and included a rock-inhabiting fungus and thus simulated weathering processes relevant to natural ecosystems.
Neuartige Materialien, die bekannte (Werk-)Stoffe mit neuen Funktionalitäten ausstatten, spielen eine zunehmend wichtige Rolle im Bereich der Materialforschung und -prüfung. Das Spektrum neuartiger Materialien reicht von der gezielten Oberflächenfunktionalisierung und -strukturierung makroskopischer Materialien, dünnen Beschichtungen bis hin zu mikro- und nanoskaligen Kompositmaterialien und funktionalen Materialien an der Schnittstelle zur Biologie, Biotechnologie, nachhaltige Energiespeicherung und Sensorik. Dabei bieten neuartige Materialien die Chance, Werkstoffe und Produkte mit erweiterter oder verbesserter Funktionalität zu erhalten und Sicherheit bereits im Designprozess zu berücksichtigen. Durch dieses breite Anwendungsspektrum und die Herausforderungen, die solche Materialien für die Sicherheit in Chemie und Technik mit sich bringen, sind diese in allen Themenfeldern der BAM repräsentiert (Material, Analytical Sciences, Energie, Infrastruktur und Umwelt).
Die Aufgaben der BAM erstrecken sich dabei von der Herstellung von Referenzmaterialien für Industrie, Forschung und Regulation, über die Erstellung von standardisierten Referenzverfahren für nachhaltige Messungen im Umwelt- und Lebenswissenschaftsbereich bis hin zur Bereitstellung von belastbaren und zitierbaren Referenzdaten. Durch die genaue Charakterisierung neuartiger Materialien können potentiell problematische Substanzen identifiziert und deren Risiken besser abgeschätzt werden. In diesem Beitrag werden einige aktuelle Beispiele aus diesen Bereichen vorgestellt.
Die gemeinsame Forschungsstrategie der Bundesoberbehörden zur Nanotechnologie wurde 2016 veröffentlicht. Die darin enthaltenen Aufgaben wurden von den Bundesoberbehörden vielfältig bearbeitet. Diese Präsentation gibt einen Überblick über die Projekte, die von der BAM bis 2019 bearbeitet wurden/werden und sich in den Rahmen der Forschungsstrategie einordnen.
Nach einer Übersicht zu den immer schneller aktualisierenden Rahmenbedingungen von Politik und Gesellschaft folgt eine Übersicht zu materialwissenschaftlichen Problemen des Recyclings von Kunststoffen. Lösungsansätze aus der Forschung reichen von einfacher Optimierung bis hin zur radikalen Neukonstruktion der polymeren Werkstoffe. Aus dem bereits möglichen Ansatz "performance-by-design" wird ein neuer Weg des "recycling-by-design" adressiert. Dies inkludiert methodisch eine skalenübergreifende Modellierung und die Depolarisation bis zum Monomer.
In well-annealed thin polymer films, with non-repulsive polymer/substrate interactions, an irreversibly adsorbed layer is expected to from. These adsorbed layers have shown greate potential for technological applications. However, their growth kinetics and molecular dynamics are still not fully understood. This is partly due to the hard accessibility of these layers in thin films. Here, the irreversibly adsorbed layers of homopolymer thin films are revealed by solvent-leaching experiments. First, the growth kinetics of these layers is investigated as a function of annealing time, annealing temperature, leaching time and the original filme thickness. The film thickness, topography and the quality of the adsorbed layer is controlled by Atomic Force Microscopy (AFM). Secondly, the molecular mobility of the adsorbed layer is investigated by Broadband Dielectric Spectroscopy (BDS). A recently developed nanostructured capacitor arrangement is employed to measure the layer with a free surface. The results are quantitatively compared and discussed with respect to recently published work.
Mechanische, topometrische und optische Charakterisierung von Schichten mit Stand der Normung
(2019)
Der Vortrag „MECHANISCHE, TOPOMETRISCHE UND OPTISCHE CHARAKTERISIERUNG VON SCHICHTEN MIT STAND DER NORMUNG“ widmet sich unterschiedlichen Beschichtungssystemen und deren mechanischer, topometrischer und optischer Charakterisierung. Über die entsprechenden aktuellen Normen wird informiert. Es betrifft Verfahren wie die Instrumentierte Eindringprüfung (IIT), Centrifugal Adhesion Testing, Weißlichtinterferenzmikroskopie, Tastschnittverfahren und Ellipsometrie (SE).
The cleaning of black carbon covered Italian marble and limestone sculptures is a challenging task for restorers and scientists, especially when black soot is penetrated into the porous surface of a stone.
Numerous sculptures of the Bode-Museum underwent two domestic fires at the repository in Berlin in May 1945, where soot damaged the surface of these artworks. Promising results in removing black layers were achieved by the application of modified gels to artificially weathered and sooted Carrara marble mockups. However, transferring the cleaning method to original samples requires a cautious proceeding with respect to short-term and long-term implications. To understand physico-chemical reactions, the analytics of gel-treated marble surfaces is of essential importance.
Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) and Auger electron spectroscopy (AES) were used to gain insights into surface chemistry and the distribution of chemical groups or fragments and enable a deeper understanding of the functionality of the applied gels and of the efficiency of tested cleaning processes. Depth profiling by ToF-SIMS is introduced as a tool to study the penetration behavior of applied cleaning chemicals.
The contribution presents the analytical methods, their possibilities and challenges, and summarizes initial results of this study.
Applications on Surface Functionalization by Laser-Induced Periodic Surface Structures (LIPSS)
(2019)
In recent years, the understanding on the formation of laser-induced periodic surface structures (LIPSS) has led to an emerging variety of applications that modify the optical, mechanical and chemical properties of many materials. Such structures strongly depend on the used polarization and are formed usually after irradiation with ultrashort linearly polarized laser pulses. Some specific formation mechanisms to explain every situation are still to be uncovered, but the most accepted explanation relies on the interference of the incident laser beam with electromagnetic surface waves that propagate or scatter at the surface of the irradiated materials. This leads to an intensity modulation that is finally responsible for the selective ablation in the form of parallel structures with periodicities ranging from hundreds of nanometers up to some micrometers. The versatility when forming such structures is based on the high reproducibility with different wavelength, pulse duration and repetition rate laser sources, customized micro- and nanometric spatial resolutions and compatibility with industrially relevant processing speeds when combined with fast scanning devices. In this contribution, we review the latest applications in the rapidly emerging field of surface functionalization through LIPSS, including biomimetic functionalities on fluid transport, control of the wetting properties, specific optical responses in technical materials, improvement of tribological performance on metallic surfaces and bacterial and cell growth for medical devices among many others.
The Systematic Review of ISO/DIS 15632 Selected Instrumental Parameters for the Specification and Checking of Energy-Dispersive X-Ray Spectrometers for Use in Electron Probe Microanalysers is discusssed. Zero strobe peak, better description of dead-time and of the pulse-processing electronics are the major issues under discussion.
Boehmite nanoparticles has been successfully functionalized with APTES. After APTES functionalization further modification with tailored molecules e.g. via carboxylic acids is possible. The tailored surface functionalization is strongly enhanced by improved coupling protocols. Arbitrary variation of the functionalization degree is possible. Thereby the temperature stable APTES functionalization enables a wide range of functional groups.
By TGA-MS analysis strong evidence for the bonding situation of the APTES on the boehmite surface has been found. Additionally first experiments has been performed to predict the polymer-particle compatibility enhancement via reverse wetting angle measurements with AFM.
The presentation points out and discusses potential future projects on microbeam analysis which shall benefit from the pre-standardisation platform VAMAS (Versailles Project on Advanced Materials and Standards) which is basically related to Organisation and participation in international inter-laboratory comparisons. Ideas and strategies of better synergies between VAMAS and ISO projects (including promotion and a dedicated liaison) are discusssed.
Grouping of nanomaterials (NM) promises to serve effectively to reduce the extensive safety testing needs associated with regulatory risk assessment. Key challenges in this task are how to rapidly and cost-efficiently generate the needed data, and how to best combine structural material characteristics with biological effects data. Herein, we performed NM grouping from combining existing physiochemical data with high-throughput screening (HTS)-derived hazard assessment data generated in the human lung epithelial cell line BEAS-2B. Twenty-one NMs from the European Joint Research Centre´s Representative Nanomaterials Repository (diverse nanoforms of substances ZnO, SiO2 and TiO2) and five reference chemicals were analyzed by HTS assays for cytotoxicity/cell viability (CellTiterGlo, Dapi-staining), oxidative stress (8-OHdG), apoptosis (Caspase-3), and DNA damage repair (γH2AX). Additionally, physicochemical data relevant for grouping of NMs under REACH (ECHA, 2017 Appendix R.6-1) were collated for 15 of the NMs, including from EU-funded projects (NanoReg2, caLIBRAte) and the OECD Testing Programme of Nanomaterials. The diverse data types were scaled, normalized and integrated using a newly developed scoring pipeline inspired by the US-EPA Toxicological Prioritization Index (ToxPi). Results demonstrated that the in vitro-derived hazard data permitted substance-based grouping of the selected NMs, whereas integration of physicochemical data deepened the grouping of specific nanoforms within each substance group. Furthermore, a case study on 10 TiO2 NMs showed that hazard-based grouping allowed for read across of physicochemical data between 6 NMs acting as source nanoforms and 4 NMs acting as target nanoforms. The ToxPi tool and scoring pipeline permitted transparent visualization of the final grouping, while giving equal weight to different types of data/results related to structure and biology. Overall, this study aligns fully with the ECHA recommendations for grouping of NM (Appendix R.6-1), i.e. i) to aim at identification of criteria for grouping nanoforms (and non-nanoforms) within one substance, and ii) to provide additional information beyond physicochemical data to support read across between nanoforms.
Seit einigen Jahren wird in den Medien viel über das Thema Mikroplastik (MP) diskutiert. Dabei wird häufig von einer großen Anzahl an MP-Partikeln in allen Bereichen der Umwelt, wie dem Wasser, dem Boden, der Luft und in Biota sowie über mögliche Gefahren ausgehend von MP, berichtet. Jedoch sind diese Studien häufig nicht untereinander vergleichbar, da verschiedene Konzepte der Probennahme, der Aufbereitung und unterschiedliche Detektionsverfahren verwendet werden. Um diesen Mangel an vergleichbaren und aussagekräftigen Daten zu beheben, wird aktuell versucht, eine Harmonisierung der Mikroplastikanalytik voranzutreiben. Neue, schnellere Methoden zur MP Quantifizierung wurden entwickelt. Gleichzeitig werden neue Strategien zur Probenahme und Probenvorbereitung konzipiert, da hier die Fehlerquellen besonders große Auswirkungen auf das Ergebnis haben.
In diesem Vortrag werden verschiedene Verfahren bezogen auf Probennahme, -vorbereitung und Analytik gezeigt und bezüglich ihres möglichen Ergebnisses diskutiert.
Metal-organic frameworks (MOFs) are suitable materials for gas storage of small molecules due to their nanoporous, crystalline structure. The extensively studied MOF HKUST-1 consist of Cu(II)-dimers in a paddlewheel structure, with 1,3,5-benzenetricarboxylic acid (BTC) as organic linker. Instability to humidity remains an issue for many types of MOFs, and for HKUST-1, it has been found that exposure to water vapor creates a surface barrier which reduces the gas uptake rate.
Near-ambient pressure XPS (NAP-XPS) is a promising method for investigations of the stability and interaction of HKUST-1 with various gas molecules. The oxidation state of copper can be monitored before, during and after exposure to various gases. This does not only provide information on the stability of the MOFs, but also on the interaction with the gas molecules.
NAP-XPS measurements of HKUST-1 exposed to methanol, pyridine and water vapor were performed with EnviroESCA, a laboratory NAP-XPS instrument developed by SPECS. Cu 2p, O 1s and C 1s core level spectra and Cu LMM Auger spectra were acquired at pressures ranging from high vacuum to 4 mbar to assess the oxidation state of copper and the stability of the organic linker. Reference measurements in argon atmosphere were conducted in order to have reference spectra with similar full width of half maxima (FHWM) as the spectra measured in reactive atmospheres. Peak fit analysis of the Cu 2p3/2 core level spectra shows that, as expected, the photoelectron signal mainly originates from Cu(II) species. The contribution from Cu(I) is negligible for samples exposed to argon and methanol, but approximately 4% for samples exposed to water vapor and 8% for samples exposed to pyridine. Within the error of the peak fit analysis, there are no changes in relative Cu(II) percentage with increasing water, methanol or pyridine exposure time pointing to saturation reached already at the lowest time of exposure.
Two epoxy-based nanocomposites with different nanofillers (layered double hydroxide and boehmite) were investigated employing temperature modulated DSC, flash DSC and broadband dielectric spectroscopy. Detailed investigation on the molecular mobility of the two systems showed the effect of the fillers on the structure of the bulk epoxy matrix and the interface formed at the polymer/particle interface
New reference material candidates for traceable size measurement of non-spherical nanoparticles
(2019)
New model nanoparticles with well-controlled shape were synthesized within the EMPIR project nPSize - Improved traceability chain of nanoparticle size measurements. Their systematic characterization takes place by the traceable methods scanning/transmission electron microscopy, atomic force microscopy and small angle X-ray scattering. Following reference nanoparticle candidates are under investigation with respect to their homogeneity and stability: titania nanoplatelets (10-15 nm x 50-100 nm), titania bipyramides (~60 nm x 40 nm), titania acicular particles (100 nm x 15-20 nm; aspect ratio 5.5/6), gold nanorods (~10 nm x 30 nm), and gold nanocubes (~55 nm x 55 nm x 55 nm).
Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, by means of inelastic neutron scattering, the vibrational density of states (VDOS) and the molecular mobility were investigated for PIM-1, the prototypical polymer with intrinsic microporosity. 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 the 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.
Elastic fixed window scans were measured on a neutron backscattering spectrometer to have an overview about the molecular dynamics at a time scale of ca. 1 ns. The temperature dependence of the estimated mean squared displacement shows a step-like increase in the temperature range from 100 K to 250 K indicating the onset of some molecular mobility. The nature of this motional process was analyzed in detail by quasielastic neutron scattering combining Time-of-Flight and backscattering where the data are discussed with regard to both the q- and the temperature dependence.
Einkomponentige alkaliaktivierte Bindemittel (AAB), d. h. AAB, bei denen der Aktivator als Feststoff im Bindemittel vorliegt, weisen Vorteile hinsichtlich der praktischen Anwendung im Bauwesen gegenüber konventionellen AAB auf. Einkomponentige AAB lassen sich als Gemische aus reaktiver Silica und Natriumaluminat herstellen, wobei die Reaktionsprodukte von der eingesetzten Silica und den Verhältnissen Na2O/Al2O3/SiO2/H2O abhängen: Während Mikrosilica und ähnliche Reststoffe zu zeolithreichen Produkten führen, erhält man aus Reisschalenasche vollständig amorphe Gele (sog. «Geopolymere»). Mörtel auf Basis solcher Bindemittel entsprechen den Anforderungen von DIN 19573:2016-03 hinsichtlich des Widerstands gegen Schwefelsäureangriff (Prüfung bei pH = 1 für 70 d) und sind damit potentiell als Reparatursysteme für Abwasserinfrastruktur geeignet. Untersuchungen mittels 29Si-MAS-NMR und 1H-29Si-Kreuzpolarisations(CP)-MAS-NMR sowie REM-Aufnahmen von erhärteten und dem Schwefelsäureangriff ausgesetzten AAB zeigen, dass der hohe Säurewiderstand v. a. auf die Fällung von Silicagel an der Grenzfläche Mörtel/Säure zurückzuführen ist, wodurch der Korrosionsfortschritt in darunterliegenden Schichten verlangsamt wird.
Porous materials play an important role in several fields of technology, especially for energy applications like photovoltaics, electrolysis or batteries. The activity of thin porous films is affected by properties like porosity, film thickness, chemical composition of the material as well as the homogenous dispersion of the active species within the porous matrix. The complex morphology of such porous films constitutes a challenge even for modern analytical techniques and requires new approaches employing the combination/complementation of data of different analytical methods. In this contribution we characterize thin mesoporous iridium-titanium mixed oxide film properties by complementary analysis of SEM/EDS, ToF-SIMS, NanoSIMS, AES and spectroscopic ellipsometry.
Mesoporous iridium oxide - titanium oxide (IrOx-TiOx) films can be prepared by a well-established Synthesis route via soft-templating. IrOx-TiOx films are very sensitive to the conditions of synthesis. Analysis by SEM and NanoSIMS imaging suggests IrOx-TiOx films with and without a homogenous dispersion of IrOx within the TiOx film matrix under different synthesis conditions.
Auger electron spectroscopy (AES) analysis in the depth-profile mode as well as cross-section line-scan AES measurements of an inhomogeneous IrOx-TiOx film indicate the presence of an IrOx-rich Phase dispersion both at the surface of IrOx-TiOx film as well as within the film.
The contribution will assess in detail the sensitivity of the synthesis conditions and the characterization of the thin metal oxide films. Moreover, the correlation between and comparison to other measurement techniques will be discussed.
The test material EDS-TM001 together with an accompanying software package, “EDS spectrometer check”, have been made available in 2009 by BAM to be employed by EDS (energy-dispersive X-ray spectrometer) users to check the performance of an EDS with a SEM. With EDS-TM001/002 test material, this periodical check is simplified to the acquisition of only one 10 kV spectrum. The software “EDS spectrometer check” is destined to evaluate automatically this spectrum and determine the EDS performance in terms of energy resolution and calibration, as well as possible alteration of low-energy efficiency due to detector contamination. Energy resolution can be compared with the specified values according to the international ISO standard ISO 15632:2012.
EDS-TM is a synthetic material consisting of a 6 μm thick layer of C, Al, Mn, Cu and Zr deposited on a steel (EDS-TM001) or silicon (EDS-TM002) substrate. The chemical composition of EDS-TM was chosen such as to give nearly equal intensities of the low energy lines in a 10 kV spectrum, thus, making it very sensitive against spectrometer efficiency changes. New results and gained experiences will be presented.
When the FWHM of the X-ray lines in the EDS-TM spectrum are determined, the spectrum Background must be subtracted accurately. The applied physical background subtraction procedure is robust and considers the transmission of the detector window. While the previous version considers only Moxtek AP windows, the new software version includes selection of silicon nitride window and the case of windowless detector.
New reference material candidates for traceable size measurement of nonspherical nanoparticles
(2019)
Size measurement of nanoparticles (NP) becomes a challenging analytical problem when non-spherical shapes must be traceably measured. However, most industrial NPs have irregular shapes and broad size distribution making it often more complex to follow European regulatory to identify a material as a nanomaterial according to which accurate measurement of the smallest dimension and its size Distribution is necessary.
The European research project nPSize - Improved traceability chain of nanoparticle size measurements aims to fill this gap by developing potential non-spherical reference nanoparticles, measurement procedures and physical modelling to improve the traceability chain, comparability and compatibility for NP size measurements between different methods. Therefore, new model NP with well-controlled shape has been synthesized and are supposed to be systematically characterized using the traceable methods scanning/transmission electron microscopy, atomic force microscopy and small angle X-ray scattering.
Following NP candidates are under investigation with respect to their homogeneity and stability: (i) titania nanoplatelets (10-15 nm thickness x 50-100 nm lateral), (ii) titania bipyramides (~60 nm length x 40 nm width), (iii) titania acicular particles (100 nm length x 15-20 nm width; aspect ratio 5.5/6), (iv) gold nanorods (~10 nm width x 30 nm length), and (v) gold nanocubes (~55 nm x 55 nm x 55 nm). In addition, sample preparation procedures as well as measurement analysis procedures with evaluation of appropriate measurands and descriptors for each material class and method are being developed to support standardization. To underpin the traceability of the size measurement of nonspherical NP, physical modelling of the signals in e.g. electron microscopy techniques will be used and in combination, the implementation of machine learning is aimed to facilitate measurement Analysis procedures, especially regarding the accurate thresholding/segmentation of the NPs.
Bacterial samples are typically freeze dried or cryo-prepared prior to XPS analysis to allow for measurements in ultra-high vacuum (UHV). The sample environment in the near-ambient pressure (NAP) XPS instrument EnviroESCA allows for measurements in up to 15 mbar water vapor, thus, sample preparation is no longer restricted to UHV-compatible techniques. For instance, biofilms grown in medium can be transferred directly from the medium to the measurements chamber, maintaining a humid environment throughout the measurements. Considering the complexity of bacterial samples, sample preparation must be carefully considered in order to obtain meaningful and reproducible results.
In this talk, various strategies for sample preparation of bacteria and biofilms for NAP-XPS measurements will be discussed. Model systems of planktonic bacteria, artificial biofilms resembling the exopolysaccharide matrix and biofilms have been characterised in various conditions. The stability and homogeneity of the samples was assessed by monitoring the C1s core level peak at different sample locations. The quality of the XPS-spectra is also influenced by the gas environment, which will be exemplified by core level spectra of P. Fluorescens acquired in air, water vapor and ultra-high vacuum.
Core-shell nanoparticles (CSNPs) have become indispensable in various industrial applications. However, their real internal structure usually deviates from an ideal core-shell structure. To control how the particles perform with regard to their specific applications, characterization techniques are required that can distinguish an ideal from a non-ideal morphology. In this work, we investigated PTFE-PMMA (four samples) and PTFE-PS (six samples) polymer CSNPs with constant core diameter (45 nm) but varying shell thickness (4-50 nm). As confirmed by transmission scanning electron microscopy (T-SEM), the shell completely covers the core for the PTFE-PMMA nanoparticles, while the encapsulation of the core by the shell material is incomplete for the PTFE-PS nanoparticles. X-ray photoelectron spectroscopy (XPS) was applied to determine the shell thickness of the nanoparticles. The software SESSA V2.0 was used to analyze the intensities of the elastic peaks and the QUASES software package to evaluate the shape of the inelastic background in the XPS Survey spectra.
For the first time, nanoparticle shell thicknesses are presented which are exclusively based on the analysis of the XPS inelastic background. Furthermore, principal component analysis (PCA) assisted time-of-flight secondary ion mass spectrometry (ToF-SIMS) of the PTFE-PS nanoparticle sample set revealed a systematic variation among the samples and, thus, confirmed the incomplete encapsulation of the core by the shell material. Opposed to that, no variation is observed in the PCA scores plots of the PTFE-PMMA nanoparticle sample set. Consequently, the complete coverage of the core by the shell material is proved by ToF-SIMS with a certainty that cannot be achieved by XPS and T-SEM.
A look inside nanoparticles
(2019)
Small-angle scattering is the method of choice when it comes to obtaining information about the interior of nanoparticles. The aim is to make nanotechnology safer. While the use of small-angle neutron scattering (SANS) is limited to a few instruments in the world, small-angle X-ray scattering (SAXS) is widely accessible, with an upward trend. The example of core-shell particles shows how simple their analysis is with data from an Anton Paar laboratory system. Here, SAXS is a central tool for the development of new reference materials based on poly(methyl) acrylate-PVDF core-shell particles. The dimensions of the cores and shells can be precisely determined. A detailed analysis makes it possible to show that the cores contain fluorinated and nonfluorinated polymers, whereas the shell consist only of PVDF. This core-shell particles with a diameter around 40 nm show a significantly higher PVDF beta phase content than the PVDF homopolymer when using an emulsion polymerization technique. This finding is of importance with respect to applications in electroactive devices.
Im Vortrag wird die Problematik Mikroplastik eingeführt und ein Probenset aus dem Mittelmeer mit ersten Ergebnissen besprochen. Die Alterung von Polymeren im Umweltkontext sowie Möglichkeiten der Analyse von Polymeralterungsfortschritten werden diskutiert. Die thermoanalytische Methode mit Zersetzungsgasanalytik (TED-GC-MS) wird eingeführt und deren Einsatzmöglichkeiten in der Thematik umrissen.
Der Vortrag beschreibt den Entwicklungsprozess des Analysenverfahrens TED-GC-MS zur Bestimmung von Mikroplastikgehalten in Umweltproben im Rahmen des BMBF-Projektes MiWa. Die Funktionsweise, die Automatisierung und die Optimierung einzelner Geräteparameter und Leistungsdaten werden gezeigt. Untersuchungen des Einflusses von Probenmatrices werden dargestellt und die Ergebnisse einiger Messkampagnen und Ringversuche vorgestellt, die die Routinefähigkeit des Verfahrens dokumentieren.
The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has enormous influence on the early hydration of cement. C3A as the most reactive phase of Portland cement plays a significant role in early hydration reactions and affects the rheological performance. Therefore, this talk presents experimental results about the influence of delayed addition of PCEs on the Hydration of alite and C3A-gypsum pastes investigated by isothermal heat flow calorimetry. Complementary in-situ XRD was carried out on C3S and C3A-gypsum pastes to analyze hydration and phase changes related to the addition of PCE. Cement pastes with a delayed addition of PCE showed less retardation compared to simultaneous addition. The alteration caused by PCE is much more pronounced for C3A-gypsum mixes. With a delayed addition of SP, the hydration of C3A is less retarded or even accelerated. It is obvious that there is less retardation the later the addition of SP. Furthermore, the PCE alter the hydration of C3A when added delayed and exhibit changes in kinetics and Hydration rates. XRD results showed that more C3A is dissolved in the presence of PCE. Also, the gypsum depletion occurs earlier in the presence of PCE and even faster with delayed addition. Without PCE AFm starts to form just after the gypsum depletion. However, in the presence of PCE AFm already starts to form at the beginning of the hydration. Due to the faster gypsum depletion in the presence of PCE, also the transformation from ettringite into AFm begins earlier, but takes longer as without SP.
Femtosecond laser-induced periodic surface structures: from light localization to applications
(2019)
This presentation reviews the current state in the field of Laser-induced Periodic Surface Structures (LIPSS). These surface nanostructures are a universal phenomenon and can be generated on almost any material by irradiation with intense linearly polarized laser radiation. LIPSS are formed in a “self-ordered” way and are often accompanying material processing applications. They can be produced following a single-step process and enable surface functionalization through the adaption of optical, mechanical and chemical surface properties. Their structural sizes typically range from several micrometers down to less than 100 nanometers exhibiting a clear correlation with the polarization direction of the laser radiation. Various types of surface structures are classified, relevant control parameters are identified, and their material specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics, through time-resolved optical experiments and theoretical simulations. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
Nanomaterials are present in our everyday life. Paint coats, sunscreens, catalysts and additives for tyres are good examples for the use of such materials in mass-market products. The problem of the safety of nanomaterials is recognized as a problem for health and environment, which lead to the special registration of nanomaterials according to an annex of REACH as of 2020. But a great problem for the risk assessment of nanomaterials that several factors could influence the hazardous nature of them. Additional to composition, crystal structure, size and shape the surface properties of such particles belong to these parameters for risk assesment. The reason for the relevance of the surface is obvious: the smaller the particle, the higher is the share of the surface. Additionally, the surface is the region of the particle which interacts with the surrounding which is another crucial factor for the understanding the effect of a nanomaterial on health and environment. In the OECD Testing Programme on Manufactured Nanomaterials exists consequently an Endpoint 4.30 Surface Chemistry in Chapter 4. PHYSICAL AND CHEMICAL PROPERTIES. In summary, there is obviously a need for a correlation between surface chemical analytic data and toxicity. To fill in this gap, we present surface analytic results obtained with X-ray photoelectron spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry and correlate them with cytotoxic data gain by high-throughput screening experiments. It must be noted, that these experiments were done at the same set of titania materials taken from the JRC (Joint Research Centre of the European Union) Nanomaterials Repository. As material TiO2 was chosen due to its widespread use in consumer products, e.g. paint coats and sunscreens. With this new approach a better understanding of the influence of surface properties on the toxicity can be expected leading to a better risk assessment of these materials.
Die zunehmenden Nachweise von Kunststoffen in verschiedenen Umweltmedien erfahren in den letzten Jahren weltweit ein zunehmendes wissenschaftliches, gesellschaftliches und politisches Interesse. Besondere Aufmerksamkeit erfahren Kunststoffpartikel von 1-1.000 µm, sogenanntes Mikroplastik. Es wurde mittlerweile in Wasser, Böden, Luft und Biota nachgewiesen. Obwohl die Wirkungen auf die natürlichen Umweltfunktionen noch unklar sind und kontrovers diskutiert werden, ist allein durch die ubiquitäre Präsenz eine systematische Erfassung von Eintragsquellen und Verbleib der Partikel über alle Umweltmedien notwendig, um Maßnahmen zur Reduktion der Einträge zu veranlassen.
Für eine zuverlässige Erfassung sind medienübergreifende Verfahren zu entwickeln, welche die drei analytischen Schritte, Probennahme, Probenaufbereitung und Detektion beinhalten. Die Verfahren adressieren unterschiedliche Zielgruppen, welche verschiedene analytische Informationen fordern. Für die akademische Bewertung werden Verfahren mit hohem analytischen Aufwand favorisiert, welche möglichst detaillierte Information über Partikelsorte, -größe, -zahl und -oberflächenbeschaffenheit geben. Im Gegensatz dazu, fordern Anwender aus der Praxis schnelle und einfache Monitoring Verfahren, welche die Bestimmung eines Massengehaltes, bzw. eines Grenzwertes zulassen. Allen ist gemeinsam, dass ein hoher interdisziplinärer Anspruch besteht, der sowohl technische Voraussetzungen zur repräsentativen Probennahme und die Limitationen von Detektionsverfahren berücksichtigt, als auch die Fachkompetenz von Biologen, Umweltwissenschaften, Analytiker und Polymerwissenschaftler einschließt.
Verfahren zum Mikroplastiknachweis müssen auch verschieden Proben mit sehr unterschiedlichen Gehalten an natürlicher Matrix gerecht werden. So müssen allein für Wasser Verfahren entwickelt werden, die Mikroplastik verschiedener Form (sphärische Partikel, komplexe Bruchstücke, Fasern) aus Medien mit sehr variablen Partikelanteil (u.a. Trinkwasser, Oberflächenwasser, Abwasser) repräsentativ erfassen, sowie schnell und kostengünstig sind – einschließlich der notwendigen Probenaufbereitung. Die jeweiligen Detektionsverfahren müssen z.B. einzelne Partikel oder integrale Gehalte über drei Dekadenklassen für thermoplastische und insbesondere auch elastomere Partikelsorten erfassen können.
No matter whether you are doing X-ray diffraction or scattering, at wide or small angles, in a lab or at a synchrotron, you will need a bespoke sequence of up to twenty different corrections before it gets about right (at our latest count). Our library now does this automatically and reliably to get you the data you deserve – in absolute units and with uncertainty estimates – without the pain. This talk will highlight the development of the modular library, the sequence and its foundation, show its applicability to real-world datasets, and highlight a possible way forward
In contrast to microplastics, little is known about nanoplastics (1 to 100 nm). In order to make the dectecability of nanoplasics more reliable, we started to develop nanoplastic reference materials. This project also aims to anser the question of how the single chain conformation of bio(polymers) changes in contact with nanoplastics. Small-angle X-ray and neutron scattering methods are suitable methods for studing this topic. Recently the soft and hard interactions between polystyrene nanoplasics and human serum albumin corona was investigated with small-angle neutron scattering. Here we concentrate on small-angle X-ray scattering as our favorite method to study how (bio)polymers change their conformation in contact with nanoplastics. The scattering of bovine serum albumin in its native state can be detected easily. The scattering pattern of this biopolymer changes dramatically when its globular stucture changes to a coil structure. Modeling of chain conformations and the calculation of the scattering pattern is relatively easy to perform. Numerous model calculations will be provided to predict the changes of conformation of single bio(polymer) chains when in conatact with nanoplastics. These predictions will be compared with recent experimenal results from in situ measurments of bio(polymers) in contact with nanoplastics. The impact of temperature, polymer concentration and salt on the single-chain conformation changes will be discussed.
The number of publications reporting the amount of microplastic (MP) all over the world increased rapidly. Methods used so far are very time consuming and not able to provide information on total contents. As harmonised sampling, sample preparation and analysis strategies are missing different studies can hardly be compared and quantitative data, including identification and mass contents of the polymers found, are missing. This leads to a lack of comprehensive understanding of MP occurrence, source and entry pathways into the environment.
We developed a method, Thermal Extraction/Desorption-Gaschromatography-Massspectrometry, as a fast screening method for MP analysis. Solid residues of water samples are heated up to 600 C under a N2 atmosphere without any sample preparation. The collected decomposition gases are separated in a gas chromatography system and detected in a mass spectrometer. Mass contents of the identified polymers can be calculated.
In this presentation we will show first results from the influent of the wastewater treatment plant Kaiserslautern (Germany) and its combined sewage system as possibly entry pathway. In order to determine the relevance of wastewater split streams analysis of grey water will be conducted. Samples are fractionally filtered by a sieve cascade with mesh sizes of 500, 100, 50 µm.
In X-ray fluorescence (XRF), a sample is excited with X-rays, and the resulting characteristic radiation is detected to detect elements quantitatively and qualitatively. Quantification is traditionally done in several steps:
1. Normalization of the data
2. Determination of the existing elements
3. Fit of the measured spectrum
4. Calculation of concentrations with fundamental parameters / MC simulations / standard based
The problem with standard based procedures is the availability of corresponding standards. The problem with the calculations is that the measured intensities for XRF measurements are matrix-dependent. Calculations must, therefore, be performed iteratively (= time consuming) in order to determine the chemical composition.
First experiments with gold samples have shown the feasibility of machine learning based quantification in principle. A large number of compositions were simulated (> 10000) and analyzed with a deep learning network. For first experiments, an ANN (Artificial Neural Network) with 3 hidden layers and 33x33x33 neurons was used. This network learned the mapping of spectra to concentrations using supervised learning by multidimensional regression. The input layer was formed by the normalized spectrum, and the output layer directly yielded the searched values. The applicability for real samples was shown by measurements on certified reference materials.
Synchrotron radiation sources with their unique properties in terms of intensity, polarization and adjustability offer a wide range of possibilities in materials research. A basic introduction about the creation and special properties of synchrotron radiation will be given. Examples of current work at BAMline, the high-energy measuring facility of the Federal Institute for Materials Research and Testing at the synchrotron BESSY, are used to illustrate the possibilities and limitations of existing measuring methods. It will be shown how the formation of corrosion layers can be tracked, how the abrasion of implants leads to the introduction of heavy metals into the surrounding bone matrix and how the detection of smallest impurities in gold is possible by optimizing the measuring conditions. Finally, an outlook at the hardware and software developments to be expected in the coming years is given.
µ-FTIR spectroscopy is a widely used technique in microplastics research. It allows to simultaneously characterize the material of the small particles, fibers or fragments, and to specify their size distribution and shape. Modern detectors offer the possibility to perform two-dimensional imaging of the sample providing detailed information. However, datasets are often too large for manual evaluation calling for automated microplastic identification. Library search based on the comparison with known reference spectra has been proposed to solve this problem.
To supplement this ‘targeted analysis’, an exploratory approach was tested. Principal component analysis (PCA) was used to drastically reduce the size of the data set while maintaining the significant information. Groups of similar spectra in the prepared data set were identified with cluster analysis. Members of different clusters could be assigned to different polymer types whereas the variation observed within a cluster gives a hint on the chemical variability of microplastics of the same type. Spectra labeled according to the respective cluster can be used for supervised learning. The obtained classification was tested on an independent data set and results were compared to the spectral library search approach.
Der Vortrag gibt den aktuellen Stand der Normung im Bereich der Oberflächentechnik insbesondere der Oberflächenanalytik und der Oberflächenmess- und -prüftechnik wider. Vorgestellt wird der Status technischer Berichte, Normenentwürfe und Normen u.a. zur Bewertung von Auflösung und Schärfe mit strahlbasierten Methoden im Nanometer- und Mikrometerbereich, zur Messung von Schichtdicken und Nanopartikeln in kritischen Dimensionen einschließlich Größen- und Formverteilungen mittels REM, zur Messung der Schichtdicke von Nanomaterialien und zur Klassifizierung von Kohlenstoffschichten mittels Ellipsometrie, zur Standardisierung der Ellipsometrie, zur Kalibrierung von Konfokalmikros-kopen für die Formmessung, zur linear elastisch dynamischen instrumentierten Eindringprüfung, zur Messung der flächenbezogenen Masse mittels AAS und ICP, zur Schichtpotentialmessung von Mehrfach-Nickelschichten, zur Schichtdicken und Flächen-widerstandsbestimmung sowie zur Bestimmung der Schichthaftung mittels Zentrifugentechnologie.
Laser-induced periodic surface structures: from nanoscaled light localization to applications
(2019)
In this contribution the current state in the field of Laser-Induced Periodic Surface Structures (LIPSS) is reviewed. This includes the mechanisms of formation and current applications, particularly the colorization of technical surfaces, the control of surface wetting properties, the tailoring of surface colonization by bacterial biofilms, and the improvement of the tribological performance of nanostructured metal surfaces.
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 α1-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 α2-process found at temperatures lower than α1-process, is assigned to the fluctuation of translational in plane movements of the triphenylene core inside distorted columns. This can be considered as a glass transition of 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.
Porous materials play an important role in several fields of technology, especially for energy applications like photovoltaics, electrolysis or batteries. The activity of porous films is affected by properties like porosity, film thickness, chemical composition of the material as well as the crystallinity of the framework. The complex morphology of such porous films constitutes a challenge even for modern analytical techniques and requires new approaches employing the combination/complementation of data of different analytical methods. In this contribution we characterize thin mesoporous iridium-titanium mixed oxide film properties by Electron Probe Microanalysis (EPMA) with energy dispersive X-ray spectroscopy (EDS) at an SEM.
The Dark Side of Science
(2019)
The Joint Summer School of the two Marie Skłodowska-Curie Innovative Training Networks (ITN) “BioCapture” and “GlycoImaging”, funded by the EU within the Horizon 2020 framework programme, which are both devoted to the development of new methods for cancer biomarker and cancer cell detection, will take place at the Adlershof Campus of BAM. 19 Early stage researchers of both projects will convene, discuss their own science and plan future collaborative research. Training in scientific writing (instructor: Luita Spangler, Free University of Berlin), an employability workshop (Antti Kapanen, University of Applied Sciences Berlin) and first contacts with the “dark side of science” (Brian R. Pauw, BAM) will complement the programme of the summer school.
There are different ways how to prove the quality of the results obtained by electron microscopy and related microanalysis techniques, e.g. use of validated standard operation procedures, participation in proficiency testing exercises, use of certified reference materials, etc. International standards are able to provide requirements, specifications, guidelines or characteristics of methods, instruments or samples with the final goal that these can be used consistently in accredited laboratories. In the field of electron microscopy and microbeam analysis standardization and metrology are terms which are encountered rather seldom at major conferences and scientific publications. Nevertheless, spectra formats like EMSA/MSA for spectral-data exchange or tagged image file format (TIFF) for SEM, guidelines for performing quality assurance procedures or for the specification of X-ray spectrometers as well as of certified reference materials (CRMs) in EPMA, or measurement of average grain size by electron backscatter diffraction (EBSD), or guidelines for calibrating image magnification in SEM or TEM are ISO standards already published and used successfully by a large part of the electron microscopy and microbeam analysis community. A main and continuous task of ISO/TC 202 and its subcommittees is to identify and evaluate feasible projects/proposals needed to be developed into new international standards, particularly in respect to recent but established technology, such the silicon drift detector (SDD) EDS one.
Another international platform in the frame of which pre-standardization work can be organized is VAMAS (Versailles Project on Advanced Materials and Standards). International collaborative projects involving aim at providing the technical basis for harmonized measurements, testing, specifications, and standards to be further developed at ISO level. One key point of VAMAS activities is constituted by inter-laboratory comparisons for high-quality data. In the field of microbeam analysis, the technical working area (TWA) 37 Quantitative Microstructural Analysis deals with corresponding projects. Good ideas, e.g. on analysis of low-Z materials/elements and at low energies are particularly encouraged by directly contacting the author. Support and already available guidance will be supplied.
Measurement of nanoparticle size (distribution) becomes a challenging analytical problem when non-spherical nanoparticles must be accurately measured. Most industrial nanoparticles have not only non-spherical shapes but also possess polydisperse size distributions, and due to their agglomeration/aggregation state are difficult (or even impossible) to be addressed individually. Moreover, driven by regulatory purposes related to the identification of a material as a nanomaterial, the accurate measurement of the smallest dimension of a (nano)particulate material makes the analysis even more complex.
In the first phase of the EU Project nPSize - Improved traceability chain of nanoparticle size measurements (https://www.bam.de/Content/DE/Projekte/laufend/nPSize/npsize.html), the efforts are focused on synthesis of nanoparticles of well-defined, non-spherical shape. Following candidates of reference materials (CRM) with certifiable particle size (distribution) are under characterization with respect to their homogeneity and stability: (i) titania nanoplatelets (10-15 nm thickness x 50-60 nm lateral), (ii) titania bipyramides (~60 nm length x 40 nm width), (iii) titania acicular particles (100 nm length x 15-20 nm width; aspect ratio 5.5/6), (iv) gold nanorods (~10 nm width x 30 nm length), and (v) gold nanocubes (~55 nm x 55 nm x 55 nm).
Everything SAXS
(2019)
In der DIN EN ISO 14577 Metallische Werkstoffe – Instrumentierte Eindringprüfung zur Bestimmung der Härte und anderer Werkstoffparameter sind die Durchführung und Auswertung des Verfahrens, sowie die Kalibrierung der zu verwendenden Prüfmaschine genormt. In dieser Norm werden auch grundsätzliche Aussagen zur Bestimmung der Messunsicherheit gemacht.
An Beispielen aus der täglichen Prüfpraxis werden verschiedene Möglichkeiten, aber auch die Grenzen der Bestimmung der Messunsicherheitbei der Instrumentierten Eindringprüfung beschrieben und kritisch diskutiert.
This presentation reviews the current state in the field of Laser-induced Periodic Surface Structures (LIPSS). These surface nanostructures are a universal phenomenon and can be generated on almost any material by irradiation with intense linearly polarized radiation. LIPSS are formed in a “self-ordered” way and are often accompanying material processing applications. They can be produced in a single-step process and enable surface functionalization through the adaption of optical, mechanical and chemical surface properties. Their structural sizes typically range from several micrometers down to less than 100 nanometers and show a clear correlation with the polarization direction of the laser radiation. Various types of surface structures are classified, relevant control parameters are identified, and their material specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics, through time-resolved optical experiments and theoretical simulations. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
Porous materials play an important role in several fields of technology, especially for energy applications like photovoltaics, electrolysis or batteries. The activity of porous films is affected by properties like porosity, film thickness, chemical composition of the material as well as the crystallinity of the framework. The complex morphology of such porous films constitutes a challenge for modern analytical techniques and requires approaches employing the combination/complementation of data of different analytical methods. In this contribution we characterize thin mesoporous iridium-titanium mixed oxide film properties by spectroscopic ellipsometry (SE).
Mesoporous iridium oxide - titanium oxide (IrOx-TiOx) films were prepared via dip-coating of a solution containing a triblock-copolymer as structure-directing agent, an iridium precursor as well as a titanium precursor in ethanol. Deposited films with different amounts of iridium (0 wt%Ir to 100 wt%Ir) were synthesized and calcined in air. The thin films were analyzed with SE using the Bruggeman effective medium approximation (BEMA) for modelling. The results were compared with electron probe microanalysis (EPMA) as part of a combined SEM/EDS/STRATAGem Analysis.
Outline
- maging ellipsometry: oncept and setup
- Basic theory: ellipsometry on tilted/curved surfaces
- Geometric considerations
- Tilt-induced cross-polarization
- Application: coating analysis on microlensarray
- Mueller-Matrix Imaging
- Conversion to Delta-Psi Image
- Layer-thickness of ITO coating
In the last years, the implementation of imaging ellipsometry in the variety of optical characterization techniques has shown tremendous potential to analyze the topology of surfaces in the lateral dimension. In the later studies, this contrast-rich surface images were affiliated with changes of the refraction indices, Absorption bands or layer thicknesses. However, it was realized that additional factors like curvature or scattering can have a great Impact on the ellipsometric readout of the analyzed system. In this study, we focus on the systematic evaluation of structural anomalies and inhomogenities of several Basic systems. This includes spherical particles as a model for microscopic curved surfaces in a range of 0.25 to 25 μm in diameter. In the macroscopic regime several conventional convex lenses were analyzed. Additional affords were made to generate microscopic concave model systems by applying nanoindentation with a spherical indentation unit. With this method calottes with a depth of 0.04 to 2 μm and radius of 2.5 μm were made. The macroscopic counterpart is delivered by conventional concave lens systems. For all systems, a variety of different bulk materials was investigated. This includes metal oxides, metals and polymers as well as combinations of each by applying coatings on the bulk materials with different layer thicknesses.
To analyze these structural anomalies and inhomogenities properly, Mueller-Matrix imaging ellipsometry is the method of choice to address cross- and depolarization effects that occur due to the curved surfaces.
Supplementary methods were used for an independent characterization of the topological properties of all structural anomalies and inhomogenities. This includes AFM and SEM for the microscopic samples (microparticles and nanoindented holes) and white light interferometry for the macroscopic lenses.
This study results in a systematic screening of different coated and uncoated material systems with a topology that does not fit into conventional ellipsometry and thus is analyzed by Muller-Matrix imaging ellipsometry. This will help in quality control and is a contribution to the understanding of the polarizing effects of non-ideal Systems analyzed by ellipsometry.
Up until several years ago, tensile and compressive tests have been exclusively carried out as single-sample tests within a tensile, hardness or universal testing machine. The availability of centrifuge technology changed this situation in 2013 in several ways because centrifugal force is used as testing force within a rotational reference frame.
Firstly, multiple-sample strength testing became feasible for both tensile load condi-tions, e.g. determination of composite, bonding or adhesive strength, and compressive load conditions, e.g. hardness, compressibility and compactibility. Secondly, there is no need for a two-sided sample clamping and double-cardanic suspensions as samples are simply inserted using a one-sided sample support. Thirdly, shear forces can be avoided by means of guiding sleeves which steer test stamps acting as mass bodies for either tensile or compressive testing. Fourthly, up to eight samples can be tested under identical conditions within a very short period of time, typically within 15 minutes including sample loading and unloading. Hence, either a reliable statistics (of identical samples) or a ranking (of different samples) can be derived from one test run.
The bench-top test system is described in detail and demonstrated that centrifugal force acts as testing force in an appropriate way because Euler and Coriolis force do not affect the testing results. Examples for both tensile strength testing, i.e. bonding strength of adhesives-bonded joints and adhesive strength of coatings, and compres-sive strength testing, i.e. Vickers-, Brinell- and ball indentation hardness and deter-mination of spring constants, are presented, discussed and compared with conven-tional tests within tensile, hardness or universal testing machines.
At present, a maximum testing force of 6.5 kN can be realized which results at test stamp diameters of 5 mm, 7 mm, and 10 mm in tensile or compressive stress values of 80 MPa, 160 MPa, and 320 MPa. For tensile strength, this is already beyond bonding strength of cold- and warm-curing adhesives. Moreover, centrifuge technology is compliant to standards such as EN 15870, EN ISO 4624, EN ISO 6506/6507 and VDI/VDE 2616. Programmable test cycles allow both short-term stress and log-term fatigue tests. Based on a variety of examples of surface and bonding technology, applications in both fields R&D and QC are presented. Meanwhile, centrifuge technology is also accredited according to DIN EN ISO/IEC 17025.
Plastics and rubber are used in many applications, such as packaging, building, construction and mobility. Due to their favourable properties like light weight, flexible processing and low costs their production and consequently their input into the environment has increased significantly over the last decades. In the environment, oxidation processes and mechanical abrasion lead to the decomposition of these plastics into small fragments, called microplastic (< 5 mm). By definition, microplastics only involve thermoplastics and duroplastics but elastomers made out of synthetic polymers (e. g. styrene butadiene rubber), modified natural polymers (e. g. natural rubber) and products of synthetic polymers (e. g. tires) are also part of the current microplastic discussion. The main entry pathway of rubber into the environment is the wear of used tire treads in road traffic. Lassen et al. showed that 60 % of the microplastic emissions in Denmark into the environment come from secondary microplastics generated by tires. Rain events can cause microplastic and rubber to get from the street into the street inlets. Depending on the sewage system, these waters are sometimes not cleaned in the sewage treatment plants and reach the surface waters untreated.
To analyse microplastic particles in samples, mainly FTIR or Raman spectroscopic methods are applied at present. Rubber or tire particles in environmental samples cannot be analysed by these methods, because the added carbon black leads to annoying absorption and fluorescent effects.
We developed a thermoanalytical method, the so-called TED-GC-MS (thermal extraction desorption gas chromatography mass spectrometry), which allows the simultaneous detection of microplastic and tire wear with almost no sample preparation in about 2.5 h. The TED-GC-MS is a two-step analytical method which consists of a thermobalance and a GC-MS system. Up to 50 mg of an environmental sample is heated up to 600 °C in a nitrogen atmosphere. During pyrolysis, between 300 and 600 °C polymer-specific decomposition products are produced and collected on a solid phase. Afterwards the substances are desorbed, separated and analysed using the GC-MS.
The aim of the present work is to present the TED-GC-MS as a time efficient screening method to quantify the industrial most relevant polymers in street run-off samples. Analytical challenges in the determination of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and polyamide (PA), polymethyl methacrylate (PMMA) and styrene-butadiene-rubber (SBR) as a component of tire wear are honestly discussed.
The study area is a 200 m long section of the Clayallee in Berlin, a representative typical urban catchment area. The road run-off in this section flows through the gullies directly into a sample chamber, which directs the runoff in an open channel to the rainwater sewer of this area. The sample chamber allows a sample to be taken directly from the road run-off without mixing with the run-off from other areas. The sample chamber is equipped with an automatic sampler. The automatic sampler is controlled by a conductivity sensor to detect the storm event at an early stage. The sensor gives the sampler a signal to start the sampling program when it gets in contact with water and reaches a certain conductivity threshold. The capacity of the sample container is 100 l and the maximum delivery of the automatic sampler is 2.8 l/min.
Afterwards, the water was pumped through various stainless-steel sieves with a diameter of approximately 20 cm and mesh widths of 500, 100, 50 μm. The obtained solids were steam sterilized, freeze-dried and measured with the TED-GC-MS.
The results of the TED-GC-MS-measurements are summarized in Figure 1. It shows the polymers which were detected in 1 mg of the dry masses of various street run off samples obtained during a period of 1.5 years. We detected PMMA, PS, PP, PE and SBR, as a component of tire wear in the samples. The quantification of the polymers leads to amounts of PS, PP, PE and SBR between 0 µg and 10 µg. PMMA was only detected in traces.
Advanced wastewater treatment by the application of activated carbon is used to eliminate organic micropollutants in large scale wastewater treatment plants. However, underlying adsorption processes are unclear. On the one hand, compositions of wastewater differ and are very complex. On the other hand, activated carbons have physicochemical properties which impair investigations on adsorption mechanisms, since they are non-graphitic, non-graphitizable and have a highly disordered microstructure. This leads to their large surface areas and internal pore structure but also implies heteroatoms and functional groups. These are not easily accessible for research but affect the adsorption of organic micropollutants. Thermogravimetric analysis and evolved gas analysis can provide valuable insights into these kinds of systems. First, pyrolysis makes functional surface groups accessible, e.g. through decarboxylation, which facilitates characterisation of activated carbons. Second, adsorbates can be investigated by thermal desorption or decomposition, depending on the sorption conditions of the organic micropollutants. Single component systems as well as multi component systems with competing organic background matter are compared for various activated carbons. Surprising distinctions in the adsorption mechanisms will be presented.
Im Vortrag wird der Ansatz zur Aufklärung von Adsorptionsprozessen, die in der Wasserphase stattgefunden haben, mittels Thermogravimetrie und Zersetzungsgasanalyse vorgestellt.
Es wird allgemein gezeigt wie TGA zur Charakterisierung von Aktivkohleoberflächen genutzt werden kann und welche Unterschiede sich in verschiedenen Adsorbat-Systemen zeigen. Im Detail wird die thermische Zersetzung von adsorbiertem Carbamazepin an drei verschiedenen Aktivkohlen präsentiert.
Materials with a high acid resistance are required in different important infrastructures. Examples include repair systems for sewer structures, where biogenic sulfuric acid corrosion is the major degradation mechanism. Low-calcium alkali-activated materials (AAMs) have been repeatedly observed to exhibit high acid resistance. However, the reasons for the high acid resistance of these materials were not fully under¬stood until recently, and the use of highly alkaline activator solutions to produce AAMs appears to hamper their commercial uptake. These issues have been tackled by characterising one-part AAMs and studying their alteration when exposed to sulfuric acid.
One-part AAMs were synthesized by mixing blends of solid silica and sodium aluminate with water, and subsequent curing at 60–80 °C. Acid resistance testing was performed according to DIN 19573, i.e. exposure to sulfuric acid at pH = 1 for 70 days. Characterisation of the cured and the acid-exposed materials was done by XRD, ATR-FTIR, SEM as well as 29Si, 27Al and 1H MAS NMR spectroscopy, including cross-polarisation and double-resonance methods.
Materials synthesized from industrial silicas were gel-zeolite composites, containing a substantial amount of unreacted ‘excess’ silica, while materials synthesized from rice husk ash were fully amorphous, containing ‘excess’ hydrous alumina. The sulfuric acid resistance of mortars based on these binders conformed to the requirements of DIN 19573 for sewer repair applications. The high acid resistance was caused by precipitation of silica gel at the mortar–solution interface, inhibiting further degradation. The presence of alumina gel may inhibit bacterial activity, potentially further improving performance in sewer environments.
The phase assemblage of silica/sodium aluminate-based one-part AAMs can be adjusted via choice of the silica starting material. Properly designed materials exhibit excellent acid resistance, caused by precipi¬tation of silica gel which protects subjacent regions, and they may also inhibit bacterial activity.
Der Vortrag beschäftigt sich mit den gängisten Methoden zur Probennahme, -vorbereitung und Detektion von Mikroplastik. Das Zusammenspiel von Fragestellung und Methode wird betont. Es wird auf das Dikussionspapier Analytik des BMBF-Forschungsschwerpunktes Plastik in der Umwelt besonders hingewiesen sowie Bemühungen zur Normierung der Methoden auf deutscher und internationaler Ebene dargestellt.