Showing papers by "Yury Gogotsi published in 1995"
TL;DR: In this paper, the Gibbs energy minimization (GEM) computer code was used for the analysis of SiC, TiC, TaC, NbC, WC and B4C in the temperature range 300-1000 °C in high pressure steam.
Abstract: Thermodynamic analyses for the corrosion of SiC, TiC, TaC, NbC, WC and B4C in the temperature range 300–1000 °C in high-pressure steam have been conducted using a Gibbs energy minimization computer code. The calculated results are compared to experimental results for corrosion of these carbides in a hydrothermal fluid above the critical point. The formation of carbon has been predicted and observed for all these carbides, except B4C. Carbon is formed at low H2O : carbide molar ratios. Lower pressure also promotes carbon formation. For a high H2O : carbide molar ratio, the carbon will be oxidized to CO and CO2. The hydrothermal method can be used for producing carbon coatings of nanometre to micrometre thickness on the surface of carbides.
59 citations
TL;DR: In this article, the effects of oxidation in air and corrosion in high-temperature, high-pressure water on the mechanical properties of three commercially available amorphous Si-Ti-C-O (Tyranno) fibers with different oxygen contents (12%--18%) and diameters (8--11 {mu}m) were investigated.
Abstract: The effects of oxidation in air and corrosion in high-temperature, high-pressure water on the mechanical properties of three commercially available amorphous Si-Ti-C-O (Tyranno) fibers with different oxygen contents (12%--18%) and diameters (8--11 {mu}m) were investigated. The fibers were exposed to isothermal treatments at elevated temperatures and subsequently tested at room temperature. Structural changes in the fibers after oxidation and corrosion were also studied in order to understand better the degradation mechanisms of the fibers. Oxidation resulted in the formation of vitreous silica films and decreases of strength and Young`s modulus of the fibers. Hydrothermal corrosion under 100 MPa water pressure started above 300 C and resulted in the formation of a carbon layer on the surface of the fibers. Dissolution of silica in water during the treatment was observed. Corrosion at temperatures above 400 C led to the formation of relatively thick carbon films which delaminated easily. It caused a decrease of strength and Young`s modulus of the fibers. The hydrothermal method can be used for producing carbon coatings with thickness up to 2 {micro}m on the surface of silicon carbide fibers. The degrading of the mechanical properties after oxidation and corrosion was controlled by the thickness of the oxidemore » or carbon layer. Based on this fact, it is possible to predict changes in the mechanical properties from the oxidation data.« less
46 citations
TL;DR: In this article, a mixture of SiC powder with diamond seeds was subjected to hydrothermal treatment at 700-750 °C under pressures of 100-500 MPa, where diamond seeds were present.
Abstract: Mixtures of SiC powder with diamond seeds were subjected to hydrothermal treatment at 700–750 °C under pressures of 100–500 MPa. The results of this study demonstrate that well crystallised diamond is formed after hydrothermal treatment of SiC when diamond seeds are present.
33 citations