TY - JOUR A1 - Abere, M. J. A1 - Zhong, M. A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Ultrafast laser-induced morphological transformations JF - MRS Bulletin N2 - Ultrafast laser processing can be used to realize various morphological surface transformations, ranging from direct contour shaping to large-area-surface functionalization via the generation of “self-ordered” micro- and nanostructures as well as their hierarchical hybrids. Irradiation with high-intensity laser pulses excites materials into extreme conditions, which then return to equilibrium through these unique surface transformations. In combination with suitable top-down or bottom-up manufacturing strategies, such laser-tailored surface morphologies open up new avenues toward the control of optical, chemical, and mechanical surface properties, featuring various technical applications especially in the fields of photovoltaics, tribology, and medicine. This article reviews recent efforts in the fundamental understanding of the formation of laser-induced surface micro- and nanostructures and discusses some of their emerging capabilities. KW - Laser ablation KW - Laser-induced periodic surface structures (LIPSS) KW - Surface morphology KW - Oxidation KW - Tribology PY - 2016 DO - https://doi.org/10.1557/mrs.2016.271 SN - 0883-7694 SN - 1938-1425 VL - 41 IS - 12 SP - 969 EP - 974 PB - Cambride University Press AN - OPUS4-38637 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ammann, Dominic A1 - Becker, Roland A1 - Kohl, Anka A1 - Hänisch, Jessica A1 - Nehls, Irene T1 - Degradation of the ethyl glucuronide content in hair by hydrogen peroxide and a non-destructive assay for oxidative hair treatment using infra-red spectroscopy JF - Forensic science international N2 - The assessment of quantification results of the alcohol abuse marker ethyl glucuronide (EtG) in hair in comparison to the cut-off values for the drinking behavior may be complicated by cosmetic hair bleaching. Thus, the impact of increasing exposure to hydrogen peroxide on the EtG content of hair was investigated. Simultaneously, the change of absorbance in the range of 1000–1100 cm-1 indicative for the oxidation of cystine was investigated non-destructively by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) using pulverized portions of the respective hair samples. Hair samples treated with hydrogen peroxide consistently displayed a significantly increased absorbance at 1040 cm-1 associated with the formation of cysteic acid. The EtG content decreased significantly if the hair was treated with alkaline hydrogen peroxide as during cosmetic bleaching. It could be shown that ATR-FTIR is capable of detecting an exposure to hydrogen peroxide when still no brightening was visible and already before the EtG content deteriorated significantly. Thus, hair samples suspected of having been exposed to oxidative treatment may be checked non-destructively by a readily available technique. This assay is also possible retrospectively after EtG extraction and using archived samples. KW - Hair testing KW - Oxidation KW - Bleaching KW - Cysteic acid KW - HPLC–MS/MS PY - 2014 DO - https://doi.org/10.1016/j.forsciint.2014.07.029 SN - 0379-0738 SN - 1872-6283 VL - 244 SP - 30 EP - 35 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-31755 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Arlt, Tobias A1 - Manke, I. A1 - Wippermann, K. A1 - Schröder, A. A1 - Mergel, J. A1 - Riesemeier, Heinrich A1 - Banhart, J. T1 - Röntgen-Kanten-Tomografie und -Radiografie zur Untersuchung von Alterungseffekten in Brennstoffzellenmaterialien JF - MP materials testing KW - Resolution neutron-radiography KW - Local current distribution KW - Water transport KW - Carbon-dioxide KW - Methanol KW - Platinum KW - Oxidation PY - 2010 SN - 0025-5300 VL - 52 IS - 10 SP - 692 EP - 697 PB - Hanser CY - München AN - OPUS4-23045 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Baláž, M. A1 - Tešinský, M. A1 - Marquardt, Julien A1 - Škrobian, M. A1 - Daneu, N. A1 - Rajňák, M. A1 - Baláž, P. T1 - Synthesis of copper nanoparticles from refractory sulfides using a semi-industrial mechanochemical approach JF - Advanced Powder Technology N2 - The large-scale mechanochemical reduction of binary sulfides chalcocite (Cu2S) and covellite (CuS) by elemental iron was investigated in this work. The reduction of Cu2S was almost complete after 360 min of milling, whereas in the case of CuS, a significant amount of non-reacted elemental iron could still be identified after 480 min. Upon application of more effective laboratory-scale planetary ball milling, it was possible to reach almost complete reduction of CuS. Longer milling leads to the formation of ternary sulfides and oxidation product, namely cuprospinel CuFe2O4. The rate constant calculated from the magnetometry measurements using a diffusion model for Cu2S and CuS reduction by iron in a large-scale mill is 0.056 min−0.5 and 0.037 min−0.5, respectively, whereas for the CuS reduction in a laboratory-scale mill, it is 0.1477 min−1. The nanocrystalline character of the samples was confirmed by TEM and XRD, as the produced Cu exhibited sizes up to 16 nm in all cases. The process can be easily scaled up and thus copper can be obtained much easier from refractory minerals than in traditional metallurgical approaches. KW - Mechanochemistry KW - Copper sulfides KW - Copper nanoparticles KW - Magnetometry KW - Oxidation PY - 2020 DO - https://doi.org/10.1016/j.apt.2019.11.032 VL - 31 IS - 2 SP - 782 EP - 791 PB - Elsevier B.V. AN - OPUS4-50665 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brandes, E. A1 - Hieronymus, Hartmut T1 - Sicherheit bei mikrostrukturierten Reaktoren - Ergebnisse und Schlussfolgerungen aus Untersuchungen am Beispiel von Ethan/Sauerstoff-, Ethen/Sauerstoff- und Ethen/Lachgas-Gemischen JF - PTB-Mitteilungen N2 - Die Mikroverfahrenstechnik (typische innere Abmessungen der Apparaturen < 1000 pin) erfährt zunehmend Interesse für industrielle Anwendungen. Grund hierfür sind verschiedene Vorteile gegenüber konventionellen chemischen. Reaktoren wie ein erhöhter Wärme- und Stofftransport und größere spezifische Phasengrenzen. Hierdurch können im Zuge einer Prozessintensivierung höhere Raum-Zeil-Ausbeuten und Selektivitäten und darüber hinaus eine sicherere Prozessführung erreicht werden. Dies trifft vor allem dann zu, wenn als Oxidationsmittel reiner Sauerstoff, Distickstoffmonoxid (Lachgas) oder ähnliche Substanzen mit hohem Oxidationspotential eingesetzt werden. Vielfach wird angenommen, dass Mikroreaktoren inhärent sicher gegenüber Deflagrations- und Detonationsvorgängen sind. Durchmesser der Reaktionskanäle von 0,5 nun und kleiner lassen Flammendurchschläge zumindest bei Stoffen der Explosionsgruppen I1A und TIB für Gemische mit Luft als Oxidationsmittel und Umgebungsbedingungen (ca. 20 °C, ca. 1.013 mbar) als ausgeschlossen erscheinen. Für die in der Mikroverfahrenstechnik bevorzugten Reaktionsbedingungen wie erhöhter Druck, erhöhte Temperatur und vor allem Oxidationsmittel mit erhöhtem Oxidalionspotential gilt dies jedoch nicht. KW - Mikroreaktor KW - Explosion KW - Detonation KW - Oxidation PY - 2011 SN - 0030-834X VL - 121 IS - 1 SP - 55 EP - 58 PB - Wirtschaftsverl. NW CY - Bremerhaven AN - OPUS4-23515 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chandra, K. A1 - Dörfel, Ilona A1 - Wollschläger, N. A1 - Kranzmann, Axel T1 - Microstructural investigation using advanced TEM techniques of inner ocide layers formed on T92 steel in oxyfuel environment JF - Corrosion Science N2 - T92 steel was oxidized at 650 °C for 1000 h in dry and wet oxyfuel gases. The microstructure of inner oxide layer was investigated using scanning transmission electron microscopy and energy dispersive spectroscopy on thin lamellas of oxide cross-sections. The oxides were composed of fine equiaxed grains and separated into Fe-rich and Cr-rich regions. Fe-rich regions were wustite and iron sulphide while Cr-rich regions consisted of Fe-Cr spinel with different stoichiometries. Precipitates of (W,Mo)-rich oxides were formed within the oxide scale and beneath the oxide/alloy interface. Often iron sulphide and (W,Mo)-rich oxide were surrounded by Cr-rich spinel. KW - Steel KW - STEM KW - High temperature corrosion KW - Oxidation KW - Internal oxidation PY - 2019 DO - https://doi.org/10.1016/j.corsci.2018.12.008 SN - 0010-938X SN - 1879-0496 VL - 148 SP - 94 EP - 109 PB - Elsevier AN - OPUS4-47423 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chandra, K. A1 - Kranzmann, Axel T1 - High temperature oxidation of 9–12% Cr ferritic/martensitic steels under dual-environment conditions JF - Corrosion engineering, science and technology N2 - In normal operations, the opposite surfaces of the power plant components are exposed to two different environments, i.e. air/flue gas on the one side and steam on the other side. Exposure under such dual-environment can lead to accelerated corrosion of the components on the air side. The oxidation behaviour of ferritic/martensitic steel T92 was investigated under dual-environment in a specially designed test equipment. The samples were exposed to dry oxyfuel flue gas (CO2–27%N2–2%O2–1%SO2) on one side and to steam on the other side up to 1000 h at 650°C. The formation of oxide scales was characterised by optical microscopy and scanning electron microscopy with attached energy-dispersive spectroscopy. Oxidation rate of specimens under dual-Environment condition was almost three times higher than that in single-environment condition. This is explained based on hydrogen transport through the bulk alloy from the steam side to the flue gas side. KW - Oxidation KW - Dual-environment KW - Oxyfuel KW - Ferritic/martensitic steel KW - Steam PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-457101 DO - https://doi.org/10.1080/1478422X.2017.1374049 VL - 53 IS - 31 SP - 27 EP - 33 PB - Taylor & Francis AN - OPUS4-45710 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chandra, Kamlesh A1 - Kranzmann, Axel A1 - Saliwan Neumann, Romeo A1 - Oder, Gabriele A1 - Rizzo, F. T1 - High temperature oxidation behavior of 9-12 % Cr ferritic/martensitic steels in a simulated dry oxyfuel environment JF - Oxidation of metals N2 - The materials in oxyfuel power plant will be subjected to CO2– and SO2–rich gases on the fireside. The oxidation behaviour of two 9–12 % Cr steels T92 and VM12 was studied under dry oxyfuel environment in the temperature range of 580–650 °C for up to 1,000 h. The oxide structure and morphology were analyzed using various experimental techniques. A complex temperature dependence of oxidation rate is observed for both T92 and VM12 whereby the oxidation rate decreased with increasing temperature. This is attributed to increased Cr-enrichment in the inner scale with increasing temperature. T92 and VM12 alloys are also susceptible to carburization in an oxyfuel environment. KW - Oxyfuel environment KW - Ferritic/martensitic steel KW - Oxidation KW - High temperature corrosion KW - Carburization KW - Steel KW - EPMA KW - SEM PY - 2015 DO - https://doi.org/10.1007/s11085-014-9521-4 SN - 0030-770X SN - 1573-4889 VL - 83 IS - 3-4 SP - 291 EP - 316 PB - Springer CY - New York, NY AN - OPUS4-32737 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chandra, Kamlesh A1 - Kranzmann, Axel A1 - Saliwan Neumann, Romeo A1 - Rizzo, F. T1 - Comparative study on high temperature oxidation of T92 steel in dry and wet oxyfuel environments JF - Oxidation of metals N2 - Fireside oxidation of T92 steel was studied after exposure times up to 1000 h in the temperature range of 580–650 °C in simulated dry (CO2–27 % N2–2 % O2–1 % SO2) and wet (CO2–20 % H2O–7 % N2–2 % O2–1 % SO2) oxyfuel environments. Water vapour addition to the oxyfuel gas substantially increased the oxidation rate. The oxide scales developed under wet environment contained more defects, resulting in higher access of oxidants to the substrate material and enhanced oxidation. In addition, the oxide scales had lower chromium enrichment in the inner layer as compared to that in the dry condition. The oxide scales consisted of hematite and magnetite in the outer layer and a mixture of (Fe, Cr)-spinel, sulphides and wustite in the inner layer. The sulphur distribution differed between the oxide scales developed in dry and wet oxyfuel environments. Sulphur was mainly concentrated in the inner layer and at the oxide/alloy interface. In contrast to the wet oxyfuel gas, very high sulphur concentration was measured in the inner oxide scale formed in the dry oxyfuel gas. Additionally, Fe-sulphide was formed at the interface of inner and outer oxide layer in the wet condition. KW - Oxyfuel environment KW - Oxidation KW - High temperature corrosion KW - Water vapour KW - Sulphur PY - 2015 DO - https://doi.org/10.1007/s11085-015-9565-0 SN - 0030-770X SN - 1573-4889 VL - 84 IS - 3-4 SP - 463 EP - 490 PB - Springer CY - New York, NY AN - OPUS4-34585 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falk, Florian A1 - Sobol, Oded A1 - Stephan-Scherb, Christiane T1 - The impact of the microstructure of Fe-16Cr-0.2C on high-temperature oxidation – sulphidation in SO2 JF - Corrosion Science N2 - This study elucidates the impact of the microstructure of Fe-16Cr-0.2C on oxide layer formation at 650 ◦C in Ar-0.5 % SO2. A cold-rolled and two heat-treated states of the alloy were exposed for up to 1000 h. The samples were characterised in detail from microstructural and chemical perspectives using scanning electron microscopy (SEM), X-ray diffraction (XRD) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The microstructural modification of the alloy by heat-treatment was advantageous. It was found that Cr-carbides support chromia formation and reduce sulphidation when their area fraction is low and diameter is small. KW - Steel KW - Iron KW - SIMS KW - SEM KW - High temperature corrosion KW - Oxidation KW - Sulphidation PY - 2021 DO - https://doi.org/10.1016/j.corsci.2021.109618 VL - 190 SP - 109618 PB - Elsevier Ltd. AN - OPUS4-53001 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gajewski, Sven A1 - Maneck, Heinz-Eberhard A1 - Knoll, Uta A1 - Neubert, Dietmar A1 - Dörfel, Ilona A1 - Mach, Reinhard A1 - Strauß, Birgid A1 - Friedrich, Jörg Florian T1 - Purification of single walled carbon nanotubes by thermal gas phase oxidation JF - Diamond and related materials N2 - Single walled carbon nanotubes (SWNT) have been produced in an electric arc discharge by using a graphite rod as anode which is filled with a powder mixture of graphite and metallic catalysts like nickel and yttrium. The soot material containing approximately a third of SWNT was collected from the cathode region as a soft, voluminous material. The main by-products in this process are amorphous carbon and graphitic nanoparticles which have to be removed by an appropriate purification process. The as-produced soot material was purified by gas phase oxidation in air at 355 °C. The oxidation of amorphous carbon in air is advantageous against wet chemical methods because it is better controllable. Thermogravimetric analysis and electron microscopy were used to investigate the oxidation behavior of the different kinds of carbon. Oxidation of SWNT and amorphous carbon occurs simultaneously even at moderate temperatures, whereas amorphous carbon is more rapidly oxidized than SWNT. For optimizing the purification procedure by gas phase oxidation, kinetic studies were used to determine the oxidation time for each component in the soot at a given temperature. So it is possible to remove the amorphous carbon quantitatively with minimal losses of SWNT. But it was found that graphitic nanoparticles have the highest stability against oxidation and could therefore not be quantitatively removed by this method without the complete destruction of SWNT. Therefore, the electric arc discharge process has to be a controlled process for minimum production of graphitic nanoparticles to obtain a material with a high content of SWNT. KW - Nanotubes KW - Cathodic arc discharge KW - Amorphous carbon KW - Oxidation PY - 2003 DO - https://doi.org/10.1016/S0925-9635(02)00362-X SN - 0925-9635 VL - 12 IS - 3-7 SP - 816 EP - 820 PB - Elsevier CY - New York, NY AN - OPUS4-2516 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinrich, Sebastian A1 - Plettig, M. A1 - Klemm, E. T1 - Role of the Ti(IV)-superoxide species in the selective oxidation of alkanes with hydrogen peroxide in the gas phase on titanium silicalite-1: an in situ EPR investigation JF - Catalysis letters N2 - The interaction of TS-1 with gaseous hydrogen peroxide at temperatures above 373 K has been investigated by in situ EPR measurements. Treatment of TS-1 with hydrogen peroxide in the gas phase leads to a strong EPR signal, assigned to the Ti(IV)-superoxide species. In contrast to investigations with liquid hydrogen peroxide, here only one Ti(IV)-superoxide species could be detected in the EPR spectrum. The time constant of the reaction of the Ti(IV)-superoxide species detected by in situ EPR measurements was much larger than that observed for the rate of consumption of propane or propene via gas chromatographic analysis. Thus, we conclude that the Superoxide species may take part in the oxidation reaction (via side reactions or the formation of unselective products), but is probably not the main responsible species in the oxidation of propane or propene. KW - Titanium silicalite-1 KW - EPR KW - Oxidation KW - Hydrogen peroxide KW - Superoxide KW - Alkanes PY - 2011 DO - https://doi.org/10.1007/s10562-010-0534-6 SN - 1011-372X VL - 141 IS - 2 SP - 251 EP - 258 PB - Kluwer CY - Dordrecht AN - OPUS4-23553 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Keller, Julia A1 - Haase, Hajo A1 - Koch, Matthias T1 - Electrochemical simulation of biotransformation reactions of citrinin and dihydroergocristine compared to UV irradiation and Fenton-like reaction JF - Analytical and Bioanalytical Chemistry N2 - Mycotoxins occur widely in foodstuffs and cause a variety of mold-related health risks to humans and animals. Elucidation of the metabolic fate of mycotoxins and the growing number of newly discovered mycotoxins have enhanced the demand for fast and reliable simulation methods. The viability of electrochemistry coupled with mass spectrometry (EC/ESI-MS), Fenton-like oxidation, and UV irradiation for the simulation of oxidative phase I metabolism of the mycotoxins citrinin (CIT) and dihydroergocristine (DHEC) was investigated. The specific reaction products are compared with metabolites produced by human and rat liver microsomes in vitro. Depending on the applied potential between 0 and 2000 mV vs. Pd/H-2 by using a flow-through cell, CIT and DHEC are oxidized to various products. Besides dehydrogenation and dealkylation reactions, several hydroxylated DHEC and CIT species are produced by EC and Fenton-like reaction, separated and analyzed by LC-MS/MS and ESI-HRMS. Compared to reaction products from performed microsomal incubations, several mono- and dihydroxylated DHEC species were found to be similar to the reaction products of EC, Fenton-like reaction, and UV-induced oxidation. Consequentially, nonmicrosomal efficient and economic simulation techniques can be useful in early-stage metabolic studies, even if one-to-one simulation is not always feasible. KW - Mycotoxins KW - In vitro KW - Electrochemistry KW - Oxidation PY - 2017 DO - https://doi.org/10.1007/s00216-017-0350-6 SN - 1618-2642 VL - 409 IS - 16 SP - 4037 EP - 4045 PB - Springer CY - Heidelberg AN - OPUS4-40492 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kirner, Sabrina V. A1 - Slachciak, Nadine A1 - Elert, Anna Maria A1 - Griepentrog, Michael A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Sahre, Mario A1 - Dörfel, Ilona A1 - Sturm, Heinz A1 - Pentzien, Simone A1 - Koter, Robert A1 - Spaltmann, Dirk A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization JF - Applied Physics A N2 - Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms. KW - Femtosecond laser KW - Titanium KW - Oxidation KW - Friction PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-445609 DO - https://doi.org/10.1007/s00339-018-1745-8 SN - 0947-8396 SN - 1432-0630 VL - 124 IS - 4 SP - 326, 1 EP - 10 PB - Springer-Verlag AN - OPUS4-44560 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kirner, Sabrina A1 - Wirth, Thomas A1 - Sturm, Heinz A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Nanometer-resolved chemical analyses of femtosecond laser-induced periodic surface structures on titanium JF - Journal of Applied Physics N2 - The chemical characteristics of two different types of laser-induced periodic surface structures (LIPSS), so-called high and low spatial frequency LIPSS (HSFL and LSFL), formed upon irradiation of titanium surfaces by multiple femtosecond laser pulses in air (30 fs, 790 nm, 1 kHz), are analyzed by various optical and electron beam based surface analytical techniques, including micro-Raman spectroscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The latter method was employed in a high-resolution mode being capable of spatially resolving even the smallest HSFL structures featuring spatial periods below 100 nm. In combination with an ion sputtering technique, depths-resolved chemical information of superficial oxidation processes was obtained, revealing characteristic differences between the two different types of LIPSS. Our results indicate that a few tens of nanometer shallow HSFL are formed on top of a ∼150 nm thick graded superficial oxide layer without sharp interfaces, consisting of amorphous TiO2 and partially crystallized Ti2O3. The larger LSFL structures with periods close to the irradiation wavelength originate from the laser-interaction with metallic titanium. They are covered by a ∼200 nm thick amorphous oxide layer, which consists mainly of TiO2 (at the surface) and other titanium oxide species of lower oxidation states underneath. KW - Laser-induced periodic surface structures (LIPSS) KW - Femtosecond laser KW - Oxidation KW - Titanium KW - Auger electron spectroscopy PY - 2017 DO - https://doi.org/10.1063/1.4993128 SN - 0021-8979 VL - 122 IS - 10 SP - 104901, 1 EP - 9 PB - AIP Publishing CY - Melville, NY, USA AN - OPUS4-41905 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - von der Ehe, Kerstin A1 - Wolff, Dietmar A1 - Jaunich, Matthias T1 - Effect of high-dose gamma irradiation on (U)HMWPE neutron shielding materials JF - Radiation Physics and Chemistry N2 - High and ultra-high molecular weight polyethylenes were gamma-irradiated with doses up to 600 kGy. The changes in the material properties were analysed using DSC, DMA, IR spectroscopy, as well as measurements of density and insoluble content. The irradiation led to an increase of the degree of crystallinity because of chain scissions during irradiation, leading to shorter and thus more mobile chains. Both the plateau value of the shear modulus G′ and the insoluble content increased with Irradiation dose, indicating the formation of additional crosslinks. Furthermore, IR spectroscopy revealed irradiation induced oxidation and the formation of double bonds, indicating that some of the hydrogen atoms responsible for the neutron shielding capability have been released. KW - Ultra high molecular weight KW - Polyethylene KW - Gamma irradiation KW - Crosslinking KW - Oxidation PY - 2018 DO - https://doi.org/10.1016/j.radphyschem.2017.02.014 SN - 0969-806X VL - 142 SP - 29 EP - 33 PB - Elsevier AN - OPUS4-42941 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lehmann, M. A1 - Schartel, Bernhard A1 - Hennecke, Manfred A1 - Meier, H. T1 - Dendrimers consisting of stilbene or distyrylbenzene building blocks synthesis and stability JF - Tetrahedron N2 - On the basis of Wittig-Horner reactions and protection group techniques compound 7 for the core and the components 9a-c and 11a-c for the dendrons were prepared and linked in the final step. The convergent synthesis yielded constitutionally and configurationally pure dendrimers (2a-c, 2a'-c') which consist of distyrylbenzene units. Their thermo-oxidative stability in the presence of air was studied by chemiluminescence and compared to the dendrimers 1 consisting of stilbene units. KW - Chemiluminescence KW - Dendrimers KW - Diphenylethylenderivate KW - Oxidation KW - Wittig reactions PY - 1999 DO - https://doi.org/10.1016/S0040-4020(99)00823-6 SN - 0040-4020 SN - 1464-5416 VL - 55 IS - 47 SP - 13377 EP - 13394 PB - Elsevier Science CY - Kidlington AN - OPUS4-1539 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, F. A1 - Lai, S. A1 - Tong, H. A1 - Lakey, P. S. J. A1 - Shiraiwa, M. A1 - Weller, Michael G. A1 - Pöschl, U. A1 - Kampf, C. J. T1 - Release of free amino acids upon oxidation of peptides and proteins by hydroxyl radicals JF - Analytical and Bioanalytical Chemistry N2 - Hydroxyl radical-induced oxidation of proteins and peptides can lead to the cleavage of the peptide, leading to a release of fragments. Here, we used high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and pre-column online ortho-phthalaldehyde (OPA) derivatization-based amino acid analysis by HPLC with diode array detection and fluorescence detection to identify and quantify free amino acids released upon oxidation of proteins and peptides by hydroxyl radicals. Bovine serum albumin (BSA), ovalbumin (OVA) as model proteins, and synthetic tripeptides (comprised of varying compositions of the amino acids Gly, Ala, Ser, and Met) were used for reactions with hydroxyl radicals, which were generated by the Fenton reaction of iron ions and hydrogen peroxide. The molar yields of free glycine, aspartic acid, asparagine, and alanine per peptide or protein varied between 4 and 55%. For protein oxidation reactions, the molar yields of Gly (∼32-55% for BSA, ∼10-21% for OVA) were substantially higher than those for the other identified amino acids (∼5-12% for BSA, ∼4-6% for OVA). Upon oxidation of tripeptides with Gly in C-terminal, mid-chain, or N-terminal positions, Gly was preferentially released when it was located at the C-terminal site. Overall, we observe evidence for a site-selective formation of free amino acids in the OH radical-induced oxidation of peptides and proteins, which may be due to a reaction pathway involving nitrogen-centered radicals. KW - Peptides KW - Proteins KW - Oxidation KW - Hydroxyl radicals KW - LC-MS KW - Amino acid analysis KW - Bovine serum albumin KW - Ovalbumin KW - Tripeptides KW - Ortho-Phthalaldehyde KW - AAA KW - Degradation KW - Fragmentation KW - Mechanism PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-398714 UR - http://link.springer.com/article/10.1007%2Fs00216-017-0188-y DO - https://doi.org/10.1007/s00216-017-0188-y SN - 1618-2650 SN - 1618-2642 VL - 409 IS - 9 SP - 2411 EP - 2420 PB - Springer CY - Heidelberg AN - OPUS4-39871 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, F. A1 - Lakey, P. S. J. A1 - Berkemeier, T. A1 - Tong, H. A1 - Kunert, A. T. A1 - Meusel, H. A1 - Cheng, Y. A1 - Su, H. A1 - Fröhlich-Nowoisky, J. A1 - Lai, S. A1 - Weller, Michael G. A1 - Shiraiwa, M. A1 - Pöschl, U. A1 - Kampf, C. J. T1 - Atmospheric protein chemistry influenced by anthropogenic air pollutants: nitration and oligomerization upon exposure to ozone and nitrogen dioxide JF - Faraday Discussions N2 - The allergenic potential of airborne proteins may be enhanced via post-translational modification induced by air pollutants like ozone (O3) and nitrogen dioxide (NO2). The molecular mechanisms and kinetics of the chemical modifications that enhance the allergenicity of proteins, however, are still not fully understood. Here, protein tyrosine nitration and oligomerization upon simultaneous exposure of O3 and NO2 were studied in coated-wall flow-tube and bulk solution experiments under varying atmospherically relevant conditions (5–200 ppb O3, 5–200 ppb NO2, 45–96% RH), using bovine serum albumin as a model protein. Generally, more tyrosine residues were found to react via the nitration pathway than via the oligomerization pathway. Depending on reaction conditions, oligomer mass fractions and nitration degrees were in the ranges of 2.5–25% and 0.5–7%, respectively. The experimental results were well reproduced by the kinetic multilayer model of aerosol surface and bulk chemistry (KM-SUB). The extent of nitration and oligomerization strongly depends on relative humidity (RH) due to moisture-induced phase transition of proteins, highlighting the importance of cloud processing conditions for accelerated protein chemistry. Dimeric and nitrated species were major products in the liquid phase, while protein oligomerization was observed to a greater extent for the solid and semi-solid phase states of proteins. Our results show that the rate of both processes was sensitive towards ambient ozone concentration but rather insensitive towards different NO2 levels. An increase of tropospheric ozone concentrations in the Anthropocene may thus promote pro-allergic protein modifications and contribute to the observed increase of allergies over the past decades. KW - Oxidation KW - Nitration KW - Cross-linking KW - Ozone KW - Nitrogen dioxide KW - Dimer KW - Air pollution KW - Diesel KW - Aeroallergens KW - Pollen KW - Tyrosine KW - Nitrotyrosine KW - BSA KW - Albumin PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-418482 DO - https://doi.org/10.1039/c7fd00005g SN - 1359-6640 VL - 200 SP - 413 EP - 427 PB - Royal Society of Chemistry CY - London AN - OPUS4-41848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Werner A1 - Jakob, Ines T1 - Oxidative resistance of high-density polyethylene geomembranes JF - Polymer degradation and stability N2 - Data are reported from oven aging in air for more than 13 years (!) and from water immersion tests for 6 years at 80 °C on various high-density polyethylene geomembranes (GM) used in landfill lining. The mechanical properties and oxidative induction times (OIT) of the samples were monitored during the long-term testing. Aging behavior in hot air is different from that in hot water. During oven aging a slow, exponential decrease of OIT is observed. Even after 13.6 years there is no indication of an oxidative degradation of the mechanical properties. During immersion in water a strong reduction in OIT occurs within the first year, after which time the curve levels off. Oxidation starts when very low OIT-values are reached after about 5 years at which time the mechanical strength rapidly falls to values below the yield point. We conclude from these data that the service life of HDPE GM's is essentially determined by the slow loss of stabilizers due to migration. The oxidation starts only after the depletion of antioxidants and then quickly leads to brittleness of the sample. However, no complete oxidative deterioration has been observed to date. We estimate by the van't Hoff rule that under normal ambient conditions many centuries will have to pass before the functional mechanical properties of state-of-the-art stabilized HDPE bulk material will be reduced below acceptable limits by oxidative degradation. KW - Durability KW - HDPE geomembrane KW - Oxidation KW - Oxidative resistance testing PY - 2003 DO - https://doi.org/10.1016/S0141-3910(02)00269-0 SN - 0141-3910 SN - 1873-2321 VL - 79 IS - 1 SP - 161 EP - 172 PB - Applied Science Publ. CY - London AN - OPUS4-2134 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -