Jean-Pierre Manaud

Thorough characterization of sputtered CuO thin films used as conversion material electrodes for lithium batteries.

CuO thin films were prepared by radio frequency magnetron sputtering using a copper target in a (Ar + O2) reactive mixture. Different sputtering parameters were varied including oxygen flow rate, total pressure, target-substrate distance, substrate temperature and target orientation. As expected, the thin film chemical composition is strongly dependent on the oxygen flow rate. CuO thin films having a good electronic conductivity (9.3 × 10(-1) S·cm(-1)) were obtained with an oxygen concentration of 12%. The texture and the columnar growth are amplified when the target is tilted. Preliminary electrochemical results highlight that CuO thin film performances in lithium systems are tightly related to their morphology and structure.

Dehydriding kinetics of a mechanically alloyed mixture Mg–10wt.%Ni

Abstract The rate-controlling steps for the dehydriding reaction of a mechanically alloyed mixture Mg–10wt.%Ni were determined by comparing empirical results with theoretical rate equations established earlier. For its dehydriding reaction at 575–615 K and 0.52–2.6 bar H 2 , the rate-controlling steps are considered the nucleation of α-solid solution of hydrogen in the range 0 H d ≤0.5, and both the bulk and Knudsen flow in the ranges higher than 0.5 H d ≤1.0 (mainly by Knudsen flow in the higher reacted ranges).

Low temperature, fast deposition of metallic titanium nitride films using plasma activated reactive evaporation

Titanium and titanium nitride thin films were deposited on silica glass and W substrates at a high coating growth rate by plasma-activated reactive evaporation (ARE). The crystal structure, preferred orientation and grain size of the coatings were determined by x-ray diffraction (XRD) technique using Cu-Kα x rays. The analysis of the coating morphology was performed by field-emission scanning electron microscopy (FE-SEM). The composition of the films was analyzed by Auger electron spectroscopy (AES) and electron-probe microanalysis (EPMA). The titanium and titanium nitride condensates were collected on a carbon-coated collodion film then characterized by transmission electron microscopy (TEM) in order to study the structures of the deposits at very short deposition times. The resistivity of the films was measured by using the four-point-probe method. The titanium coatings were found to consist of very fine particles (40nm in grain size) and to exhibit a strong (002) texture. The titanium nitride coatings ...

Comparison of the properties of TiSi2 films obtained by silicon and titanium co-sputtering and by composite target sputtering

Abstract Titanium disilicide films were deposited by sputtering from a sintered target or from two targets (titanium and silicon) on both n- and p-type wafers. These films were annealed using rapid thermal annealing and were analyzed using several analytical methods including Rutherford backscattering spectrometry, secondary ion mass spectrometry, X-ray diffraction and transmission electron microscopy. Targets with different residual impurity percentages have been used. Results show that the film properties are affected not only by the elaboration process but also by the initial quality of the targets. The layers obtained by co-sputtering have a resistivity as low as 13 μΩ cm and are formed with grain size of more than 1 μm.

A new thermochemical process for hydrogen production

Abstract A new thermochemical water-splitting cycle using the oxydo-reduction couples Ag+/Ag0 and Cu2+/Cu+ is described. It includes four main reaction steps, some of them requiring a solvent. At the maximum temperature of 570°C the thermal efficiency is about 41%.

Phenomena Leading to a Modification of the Nano-Sized Structure during Resistance Upset Welding of ODS Steel Cladding

ODS steels (Oxide Dispersion Strengthened) are candidate materials for fuel cladding in Sodium Fast Reactors (SFR). These materials have good mechanical properties at high temperature due to a dispersion of nanometer-sized oxides into the matrix. Previous studies have shown that melting can induce a decrease of the mechanical properties at high temperatures due to modifications of the nanometer-sized oxide dispersion. Therefore the fusion welding techniques are not recommended and the solid state boundings has to be evaluated. This study is focused on resistance upset welding. Welding experiments and numerical simulations are coupled. The numerical simulation is developed in order to have a better understanding of the thermal and the mechanical phenomena occurring during the welding process. The simulation shows that the welding steps can be divided in two stages. First, the temperature of the contact between pieces increases. Second, the heat generation is mainly located in the cladding leading to the collapse and forging the pieces. The microstructural observations confirm that the major deformation is located in the cladding. Oxide dispersion modification and dynamical recrystallisation has been found for welds achieved with a non optimized process parameter set. The deformation and the temperature seem to be of prime importance in the modification of the oxide dispersion.

SYNTHETIC INTERFACES DESIGNED FOR SiC REINFORCED TITANIUM OR INTERMETALLIC MATRICES

Various filament coatings were investigated in order to control the fiber/matrix interaction in titanium or aluminide matrix composites. Making use of the sputtering technique metallic, intermetallic and oxide layers were deposited onto silicon carbide filaments. The composites processed with these protected reinforcements according to the diffusion bonding method allowed the advantages of the Si, TiSi2 or Y2O3 coatings to be pointed out. Compared to the well known pyrocarbon layers, these in erphases offer a better oxidation resistance while delaying fiber-matrix chemical reaction.