Abstract: A coating for sealing carbon--carbon composites against hydrogen. The coating comprises a first layer of silicon carbide and a second layer of a glass, glass-ceramic or a low-melting-point metal such as tin or an alloy thereof. Particularly when such second layer is a glass, e.g. an SiO.sub.2 -containing glass, or a glass-ceramic, preferably the silicon carbide coating is pretreated, e.g. by oxidation thereof to form a thin layer of SiO.sub.2 prior to application of the glass layer. The glass layer can be an SiO.sub.2 glass formed by sputtering or by decomposition of tetraethylorthosilicate (TEOS) applied to the oxidized silicon carbide coating. An alkali metal oxide, e.g. Na.sub.2 O, or an alkaline earth metal oxide, e.g. BaO, can be added to the SiO.sub.2 glass.

Abstract: A coating for sealing carbon-carbon composites against hydrogen. The coating comprises a first layer of silicon carbide and a second layer of a glass, glass-ceramic or a low-melting-point metal such as tin or an alloy thereof. Particularly when such second layer is a glass, e.g. an SiO.sub.2 -containing glass, or a glass-ceramic, preferably the silicon carbide coating is pretreated, e.g. by oxidation thereof to form a thin layer of SiO.sub.2 prior to application of the glass layer. The glass layer can be an SiO.sub.2 glass formed by sputtering or by decomposition of tetraethylorthosilicate (TEOS) applied to the oxidized silicon carbide coating. An alkali metal oxide, e.g. Na.sub.2 O, or an alkaline earth metal oxide, e.g. BaO, can be added to the SiO.sub.2 glass.

Abstract: An oxidation protection coating for metal substrate surfaces. The coating, according to a preferred embodiment, comprises an initial or first layer of a glass-ceramic, such as a barium aluminosilicate composed chiefly of baria, silica and alumina; or mullite, composed of silica-alumina or, alternatively, baria-silica. Titanium dioxide, nickel oxide or SnO.sub.2 can be added. The next layer of the coating is comprised of alumina or silicon carbide. The third or final layer is comprised of a thin layer of silica or a high-silica material, e.g., a silica containing 4% B.sub.2 O.sub.3. For a thicker third layer, particles of a dark solid, such as boron silicide, ferrous oxide, ferric oxide, nickel oxide, manganese dioxide, carbon or silicon carbide, can be incorporated. The three-layer coating provides high emittance and low catalytic activity for the recombination of oxygen and nitrogen, as well as being a hydrogen diffusion barrier.

Abstract: A carbonaceous material is subjected to a hydrotreating process in which it is desulfurized, deasphalted and demetallized by reaction with hydrogen in a molten medium in the presence of potassium hydroxide and water. The water is present in an amount sufficient to minimize the formation of gaseous hydrocarbonaceous products but insufficient to significantly reduce the effectiveness of potassium hydroxide as the hydrotreating agent. The process is characterized by producing a very small amount of gaseous hydrocarbonaceous products, desulfurizing the carbonaceous feed to the extent of at least about 80%, deasphalting the feed to the extent of at least about 60%, and demetallizing the feed to the extent of at least about 90%. In a preferred embodiment, spent potassium hydroxide is regenerated and recycled to the molten medium.