Search results for "Metallurgy"
showing 10 items of 1419 documents
Oxygen Diffusion in Alumina. Application to Synthetic and Thermally Grown Al<sub>2</sub>O<sub>3</sub>
2005
S. Chevalier, B. Lesage, C. Legros, G. Borchardt, G. Strehl, M. Kilo Laboratoire de Recherches sur la Reactivite des Solides, CNRS UMR 5613, Universite de Bourgogne, F-21078 Dijon, France Laboratoire d’Etudes des Materiaux Hors Equilibre, CNRS UMR 8647, Universite Paris XI, F-91405 Orsay, France. Institut fur Metallurgie, TU Clausthal, Robert Koch Strasse 42, D38678 Clausthal-Zellerfeld, Germany. * sebastien.chevalier@u-bourgogne.fr
Effect of Mechanoactivation on Interfacial Interaction in Metal/Oxide Systems
2006
Properties of interfaces in solid state metal/oxide joints (Al/SiO2, Al/MgO, Al/glass, Mg/MgO, Mg/SiO2, In/glass etc.) are reported. The interfaces were formed by plastic deformation of metal on the oxide surface at room temperature. Their structure, chemical composition, and micromechanical properties were studied by the AFM, XRD, SIMS, optical microscopy, and precision microindentation techniques. A noticeable adhesion was observed for metals with high affinity for oxygen and only in the regions of the maximum shear stress. Formation of an interfacial reaction zone with an oxygen concentration gradient is detected. In this zone metals are nanostructured and noticeably hardened. The effect…
Fast determination of impurities in metallurgical grade silicon for photovoltaics by instrumental neutron activation analysis
2010
Standard wafer solar cells are made of near-semiconductor quality silicon. This high quality material makes up a significant part of the total costs of a solar module. Therefore, new concepts with less expensive so called solar grade silicon directly based on physiochemically upgraded metallurgical grade silicon are investigated. Metallurgical grade silicon contains large amounts of impurities, mainly transition metals like Fe, Cr, Mn, and Co, which degrade the minority carrier lifetime and thus the solar cell efficiency. A major reduction of the transition metal content occurs during the unidirectional crystallization due to the low segregation coefficient between the solid and liquid phas…
Mechanically stable metal layers for ohmic and blocking contacts on CdZnTe detectors by electroless deposition
2015
CdZnTe detectors are commonly exploited for the detection of gamma rays. However, obtaining mechanical stable, low noise contacts on CdZnTe is still an issue. In particular, ohmic contacts would be preferable for high flux applications. In this work, we show that it is possible to obtain mechanical stable gold contacts by electroless deposition in methanol solution. Moreover, we show that electroless deposited nickel contacts are also mechanical stable and are good candidates for the realization of ohmic contacts on high resistivity CdZnTe crystals.
Effects of radiation and hydrogen-loading on the performances of raman-distributed temperature fiber sensors
2015
International audience; The integration of Raman-distributed temperature fiber-based sensors (RDTS) into the envisioned French deep geological repository for nuclear wastes, called Cigéo requires evaluating how the performances of RDTS evolve in harsh environments, more precisely in presence of H2 or γ-rays. Both H2 and radiations are shown to affect the temperature measurements made with the single-ended RDTS technology. The amplitudes of the observed effects depend on the different classes of multimode fibers varying in terms of composition and coatings. By selecting the most tolerant fiber structure for the sensing, we could maintain the RDTS performances for such application. A hardeni…
Short range ordering and phase separation in rapidly quenched Ni80 57Fe1P19 amorphous alloys solution treated at different temperatures
1990
Abstract Electrochemical measurements and Mossbauer spectroscopy were used to study a rapidly quenched Ni80 57Fe1P19 amorphous alloy solution treated between 920 and 1500 °C. Different short range orderings were shown in amorphous alloys solution treated at different temperatures. This finding can be associated with phase separation occurring in the liquid state. This phase separation can be inherited in slightly relaxed amorphous state.
Long-Term Stability of (Ti/Zr/Hf)CoSb1−xSnxThermoelectric p-Type Half-Heusler Compounds Upon Thermal Cycling
2015
The effect of thermal cycling upon the thermoelectric performance of state-of-the-art p-type half-Heusler materials was investigated and correlated with the impact on the structural properties. We simulated a heat treatment of the material similar to actual applications in the mid-temperature range, such as occurs during the energy conversion from an automotive exhaust pipe. We compared three different compositions based on the (Ti/Zr/Hf)CoSb1−xSnx system. The best and most reliable performance was achieved using Ti0.5Hf0.5CoSb0.85Sn0.15, which reached a maximum figure of merit ZT of 1.1 at 700 °C. The intrinsic phase separation and resulting microstructuring, which are responsible for the …
Numerical and experimental study of a niobium reactor preheating for titanium production by a vapor-phase reduction
2020
Morphology and magnetoresistance of Co2Cr0.6Fe0.4Al-based tunnelling junctions
2009
Some ferromagnetic Heusler compounds are theoretically predicted to be half metallic materials, i.e. to be characterized by a huge spin polarization at the Fermi energy. We investigate the correlations between junction preparation conditions, morphology and transport properties of planar MgO/Co2Cr0.6Fe0.4Al/AlOx/Co/CoOx/Pt tunnelling junctions. Epitaxial Co2Cr0.6Fe0.4Al thin films were deposited by dc and rf magnetron sputtering on different buffer layers (Cr, Fe, MgO) on MgO(1 0 0) substrates. By RHEED, LEED and in situ STM investigations different surface morphologies were observed. Atomically flat surfaces with Co2Cr0.6Fe0.4Al unit cell sized steps (B2 structure) were obtained by rf sput…