Jean Besson

A comparative study of the oxidation with water vapor of pure titanium and of Ti-6Al-4V

The oxidation kinetics of pure titanium and of Ti-6Al-4 V by water vapor were studied between 650 and 950°C and from 0.5 to 18 Torr. The results showed a marked similarity of the oxidation behavior for both the alloy and pure titanium. The rate curves had the same appearance. At low temperatures (below 750°C) they exhibited two stages. At high temperature the first of these stages was not observed. Scanning electron microscopy (SEM) and electron probe analyses of the scale showed that the structure of the scales was also similar over the temperature range 750–900°C: they consisted of two layers of rutile, and, in the case of the alloy, of a thin sublayer of alumina between the other two. Furthermore, SEM examination of the surface of oxidized specimens revealed the existence of whiskers.

Double Phonon Processes in Cadmium Sulfide

The bands of infrared absorption in hexagonal cadmium sulfide have been studied over a wide range of temperatures and are assigned to double‐phonon processes. An analysis of these absorption peaks on the basis of four frequencies is proposed. The temperature‐dependence of the location and intensity of these bands give indications upon the anharmonic parameter and Gruneisen constant of the crystal. Anharmonic forces are shown to be responsible for the coupling between normal vibrational modes.

La protection du cuivre par siliciuration superficielle

Abstract By cracking monosilane on heated nickel foils we prepared a solid solution Ni — Si on the nickel. The behaviour of so coated nickel, in oxygen, at high temperatures was investigated. The protective efficiency of this coating was correct as no oxidation could be detected up to 800°C. At higher temperatures the oxidation scale consisted of two layers, respectively a mixed layer (NiO and SiO 2 ) in contact with the metal, covered by a pure NiO layer. Kinetic curves were of sigmoidal type. The first part corresponded to a nucleation process and in the following stage the reaction rate was controlled by the outward cationic diffusion through the two layers.

La réaction du disulfure de carbone gazeux sur le tantale. Étude cinétique de la formation d'un sulfocarbure nouveau

The kinetics of the reaction between Ta and CS2 have been studied over the temperature range 800–1085 °C and at pressures between 10–250 Torr. The thermogravimetric curves obtained exhibit an initial parabolic stage followed by a slower linear stage. The influence of gas pressure on the parabolic stage is tentatively explained by a diffusion mechanism involving neutral cation vacancies in the reaction product.

Estimation des grandeurs thermodynamiques des iodures de hafnium

Resume Les grandeurs thermodynamiques existantes des iodures solides et gazeux de hafnium ont ete recensees et de nouvelles valeurs estimees sont proposees. Cette estimation est faite par comparaison systematique avec les composes equivalents du zirconium, pour lesquels de nouvelles valeurs ont ete recemment publiees.

Aspect cinetique er morphologique de la reaction du disulfure de carbone gazeux avec le cuivre

Abstract The reaction of copper with gaseous carbon disulfide has been studied in the temperature range 230–700°C for pressures from 10 to 220 torrs. The form of gravimetric curves depends on temperature: between 230 and 400°C the rate law is linear after a period during which the reaction rate decreases. At higher temperatures (470 2 S is, in both cases, compact and adherent. At lower temperatures, the results can be explained by two parallel mechanisms: the sorption of CS 2 and its decomposition in the gaseous phase. At higher temperatures, the parabolic law is related to a diffusion mechanism. Some hypothesis are made about the sorption of sulphur.