15271. The diffusion model successfully predicted minimum A1 concentrations for protective A1203 scale formation during cyclic oxidation of Ni-Cr-AI(Zr) alloys containing more than 20% Cr.2. The success of the diffusion model in predicting N~ is strongly dependent on the ability to account for partial oxide spallation. The use of the oxide spalling model (16) provides this ability.3. It is not necessary to account for surface recession or the effect of the Cr concentration gradient on the diffusion of A1 when predicting minimum A1 concentrations for protective A1203 scale formation on Ni-Cr-AI(Zr) alloys.4. The decrease and subsequent recovery in the value of the solute concentration at the alloy surface is dependent on the amount of oxide which spalls each cycle and increases with an increasing number of thermal cycles. The increase in the amount of recovery with an increasing number of cycles is without a satisfactory explanation.
ABSTRACTOxidation studies of CVD a-Si3N4 were performed in dry oxygen, oxygen-argon, and oxygen-nitrogen-argon gas mixtures of various oxygen and nitrogen partial pressures at a total pressure of I atm at 1100~176Parallel oxidation studies of single-crystal silicon were also conducted for direct comparison. It was observed that the oxidation of both Si3N4 and Si followed parabolic growth kinetics with activation energies of about 115 kcal/mol and about 30 kcal/mol, respectively. The formation of a single layer of SiO2 and evolution of N2 could not account for the much lower parabolic rate constants and much higher activation energy for Si3N4 than for Si during the oxidation. Detailed characterization of the oxidation scales using ellipsometry, step-by-step etching, SIMS, and XPS techniques indicated that a duplex oxidation scale consisting of SiO2 and SieN20 was formed when Si3N4 was oxidized. The intermediate Si2N20 scale was identified as a singlephase material, not a physical mixture of Si3N4 and SIO2. The low oxidation rate and high activation energy for SigN4 during the oxidation were attributed to the formation of Si2N20 and low oxygen diffusivity in this structurally dense phase. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.81.226.78 Downloaded on 2014-09-04 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.81.226.78 Downloaded on 2014-09-04 to IP
ABSTRACTThe available thermodynamic and phase equilibria data for the binary systems Cd-Te, Cd-Se, and Cd-S have been analyzed using an associated solution model for the liquid phases and considering the CdTe, CdSe, and CdS phases as line compounds. The phase diagrams and the thermodynamic properties calculated from the model parameters agree well with the experimental data.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.81.226.78 Downloaded on 2014-09-04 to IP