TY - JOUR A1 - Rodrigues, A. C. P. A1 - Feller, A. A1 - Agudo Jácome, Leonardo A1 - Azevedo, C. R. F. T1 - Use of synthetic Fe3O4-rich tribofilms to investigate the effect of microconstituents, temperature and atmosphere on the friction coefficient during pin-on-disc tribotest N2 - This work investigates the effect of the tribotesting parameters (temperature, atmosphere, and third body chemical composition) on the coefficient of friction (CoF) during pin-on-disc dry (PoD) sliding tribotests using artificial third bodies. The third body comprised nanometric Fe3O4-based binary to quaternary chemical compositions containing copper, graphite, and zirconia. These mixtures were manually or ball-milled prepared, and pin-on-disc tribotests were conducted at 23 °C and 400 °C under air or nitrogen atmospheres. Combining PoD and artificial third body to create synthetic tribofilms might be useful for testing new formulations of Cu-free friction materials. Microstructural characterisation of the tribofilms was used to study the stability of the Fe3O4, copper, and graphite nanoparticles under different testing conditions to understand their effects on the CoF. For the Fe3O4-C-ZrO2-X systems, the ball milling mixing promoted the formation of turbostratic graphite in the tribofilm, impairing the lubricating effect of the graphite under air atmosphere at 23 °C. The formation of monoclinic CuO in the tribofilms during tribotests at 400 °C under air and N2 atmospheres promoted a lubricating effect. KW - Tribology KW - Microstructure KW - Oxide KW - Transmission electron microscopy PY - 2022 U6 - https://doi.org/10.1088/2051-672X/ac9d51 SN - 2051-672X VL - 10 IS - 4 SP - 044009-1 EP - 044009-18 PB - IOP Pobilishing AN - OPUS4-56467 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Giovannelli, F. A1 - Chen, Cong A1 - Díaz-Chao, P. A1 - Guilmeau, E. A1 - Delorme, F. T1 - Thermal conductivity and stability of Al-doped ZnO nanostructured ceramics N2 - Pure and Al-doped ZnO powders have been sintered by Spark Plasma Sintering. Al doping allows the ceramics to reach a relative density greater than 90% at a sintering temperature of 500°C. The morphology of powder nanoparticles impacts the final grain size of the sintered bulk compounds. A ceramic sintered from isotropic nanoparticles of 30 nm in diameter can reach an average grain size of 110 nm, whereas a ceramic sintered from platelets and isotropic nanoparticles exhibits an average grain size in the submicrometric range. The influence of ceramic grain size on the thermal conductivity has been investigated. It shows that substantial decrease of the grain size from several microns down to 100 nm reduces the thermal conductivity from 29.5 to 7.8 W/m K at 100°C. The stability of nanostructured ceramic has also been checked. After SPS, an annealing at 500°C in air also leads to grain growth. KW - Spark plasma sintering KW - Oxide KW - Thermal conductivity KW - Nanostructuring PY - 2018 U6 - https://doi.org/10.1016/j.jeurceramsoc.2018.07.032 SN - 0955-2219 VL - 38 IS - 15 SP - 5015 EP - 5020 PB - Elsevier Science CY - Amsterdam AN - OPUS4-45740 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Noack, J. A1 - Emmerling, Franziska A1 - Kirmse, H. A1 - Kemnitz, E. T1 - Sols of nanosized magnesium fluoride: formation and stabilisation of nanoparticles N2 - The formation of magnesium fluoride sols and xerogels according to the fluorolytic sol–gel synthesis based on the reaction of Mg(OMe)2 with non-aqueous HF has been thoroughly investigated by X-ray scattering (WAXS/XRD), TEM, SAXS, DLS and 19F MAS NMR spectroscopy. Mechanistic insights were gained by following the reaction progress and formation of intermediate phases of the fluorination of magnesium alkoxides. For F:Mg ratios of 0.3 and 0.4 the formation of two crystalline phases was observed containing the recently obtained compound [Mg6F2(OCH3)10(CH3OH)14] hexanuclear dicubane units. The stoichiometric reaction yields magnesium fluoride nanoparticles with crystallite sizes below 5 nm, which show broad reflections in the X-ray diffraction pattern. Metal fluoride sols prepared by this way undergo tremendous changes over the first several weeks after synthesis. Immediately after the fluorination, particles of about 120 nm—probably agglomerates—are formed, which break apart in the course of about one month of ageing and low-viscous, transparent sols with particles of about 12 nm are obtained. At the same time structural re-organisation processes within the magnesium fluoride particles are observed by an increase of the (110) reflection in WAXS. KW - Surface modification KW - Colloidal particles KW - Gold nanoparticles KW - Gel synthesis KW - Small-angle scattering KW - Oxide KW - Polyelectrolytes KW - Aggregation KW - Dispersion PY - 2011 U6 - https://doi.org/10.1039/c1jm11943e SN - 0959-9428 SN - 1364-5501 VL - 21 IS - 38 SP - 15015 EP - 15021 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-26183 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kautek, Wolfgang A1 - Sorg, N. A1 - Krüger, Jörg ED - Brieger, M. T1 - Optical second-harmonic generation (SHG) on semiconductor electrodes by means of femtosecond and nanosecond-pulse lasers N2 - In situ optical second-harmonic generation (SHG) on centrosymmetric crystalline semiconductor electrodes opens up a new field of in situ investigations of hurried solid state interfaces and metal front contacts relevant to electronic and photovoltaic devices, which are rarely accessible by other methods. Photoelectrochemical nanosecond- and femtosecond-pulse laser investigations of silicon (111) electrodes show that in situ SHG is feasible in such complex interfacial systems. In a p-p polarization configuration, the azimuthal dependence of the SHG from oxide-covered and bare n-Si (111) electrodes, with and without Ni contact deposits, have been studied. Etching and regrowth of silicon oxides as well as burried interfacial electric field distributions were monitored. In situ SHG is shown to be extremely sensitive to trapped interfacial charge, crystal misorientations and surface step arrays. An advantage of femtosecond-pulses is the fact that illumination fluences that are well below the damage threshold, but still with sufficient power density, can be applied. (Author) T2 - 1st International Symposium on Semiconductor Processing and Characterization with Lasers - Applications in Photovoltaics CY - Stuttgart, Germany DA - 1994-04-18 KW - Femtosecond-Pulse Laser KW - Sub-Picosecond-Pulse Laser KW - Semiconductors KW - Silicon KW - Second-Harmonic Generation KW - SHG KW - Nonlinear Electroreflectance KW - Etch Process KW - Oxide KW - Interfacial Electronic States KW - Fermi-Level Pinning KW - MOS Diode PY - 1995 SN - 0-87849-683-1 U6 - https://doi.org/10.4028/www.scientific.net/MSF.173-174.285 SN - 0255-5476 N1 - Serientitel: Materials science forum – Series title: Materials science forum IS - 173/174 SP - 285 EP - 290 PB - Trans Tech Publ. CY - Aedermannsdorf AN - OPUS4-11672 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lippitz, Andreas A1 - Unger, Wolfgang A1 - Boese, O. A1 - Kemnitz, E. T1 - y-Al2O3 by Au 4f7/2-referenced XPS and XAES N2 - Powder x-ray diffraction (XRD) defined -Al2O3 has been investigated by x-ray photoelectron spectroscopy (XPS) and x-ray excited Auger electron spectroscopy (XAES). The Au 4f7/2 orbital is used for static charge referencing. This feature originates from well-defined and chemically inert 20 nm highly dispersed gold particles deposited on the sample surface. The particles, with a narrow particle size distribution, were obtained from a highly purified colloidal solution (sodium concentration below 1 mg/l). This procedure allows a determination of gold-referenced XPS and XAES data sets. ©2001 American Vacuum Society. KW - Au 4f referenced XPS data KW - Aluminium KW - Oxide PY - 2001 UR - http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=SSSPEN&ONLINE=YES&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&possible4=lippitz&possible4zone=author&bool4=and&fromyear=2001&OUTLOG=NO&viewabs=SSSPEN&key=DISPLAY&docID U6 - https://doi.org/10.1116/11.20020305 SN - 1055-5269 SN - 1520-8575 VL - 8 IS - 1-4 SP - 214 EP - 219 PB - AIP CY - Woodbury, NY AN - OPUS4-1910 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -