Carbides decomposition temperatures/pressures

The best results were obtained with compound 21 that exhibited high vapor pressure and low decomposition temperature (<523 K). Various CVD conditions were applied and gave in all cases shiny, dark-brown deposits.43 XRD and XPS analyses of the deposits indicated the presence of a vanadium carbonitride phase with little contamination from oxygen and free carbon. The films were less adherent on steel substrates than on silicon ones. The steel substrates seemed to suffer corrosion due to the presence of Cl-containing species. We had noticed the same feature in the case of Cl-containing precursors to vanadium carbide. Therefore, in order to increase the volatility of compound 23 and to reduce the Cl content of the molecule, we prepared compounds 24 and 25. Unfortunately, the yields obtained in their syntheses were much too low to permit TG and CVD experiments. 

III. In this process a tungsten wire, which serves only as a substratum for the deposit, is heated to glowing in an atmosphere consisting of a volatile halide of the metal, a carbon compound and Hg. Moers recommends the use of hydrocarbons such as toluene, instead of CO the deposition of free carbon with the carbide is avoided if the partial pressure of the hydrocarbon in the system is low. The hydrogen atmosphere facilitates considerably the reaction at the glow wire by reducing the decomposition temperatures of the halides to a much greater extent than does reduced pressure or even vacuum. 

Ucon HTF-500. Union Carbide Corp. manufactures Ucon HTE-500, a polyalkylene glycol suitable for Hquid-phase heat transfer. The fluid exhibits good thermal stabHity in the recommended temperature range and is inhibited against oxidation. The products of decomposition are soluble and viscosity increases as decomposition proceeds. The vapor pressure of the fluid is negligible and it is not feasible to recover the used fluid by distiHation. Also, because the degradation products are soluble in the fluid, it is not possible to remove them by filtration any spent fluid usuaHy must be burned as fuel or discarded. The fluid is soluble in water. 

The crystalline properties of silicon, silicon nitride, and silicon carbide nanoparticles produced in a laboratory aerosol reactor were measured by Cannon et al. (1982). Particles were produced using a COi laser to irradiate aerosol precursor gases. For example, silane (SiHj) u.sed to produce silicon particles could be healed adiabatically to the reaction temperature as long as the gas pressure wa.s maintained above 0,05 atm. At lower pressures, beat conduction to the cell walls balanced the heat absorbed by the gases, Silicon particles were generated at about 100() C by silane decomposition ... 

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