The present invention is a method of forming large device quality single crystals of silicon carbide. The sublimation process is enhanced by maintaining a constant polytype composition in the source materials, selected size distribution in the source materials, by specific preparation of the growth surface and seed crystals, and by controlling the thermal gradient between the source materials and the seed crystal.

Sublimation of silicon carbide to produce large, device quality single crystals of silicon carbide

An approach for the growth of high-quality epitaxial silicon carbide (SiC) films and boules, using the Chemical Vapor Deposition (CVD) technique is described here. The method comprises modifications in the design of the typical cold-wall CVD reactors, providing a better temperature uniformity in the reactor bulk and a low temperature gradient in the vicinity of the substrate, and an approach to increase the silicon carbide growth rate and to improve the quality of the growing layers, using halogenated carbon-containing precursors (carbon tetrachloride CCl 4 or halogenated hydrocarbons, CHCl 3 , CH 2 Cl 2 , CH 3 Cl, etc.), or introducing other chlorine-containing species in the gas phase in the growth chamber. The etching effect, proper ranges, and high temperature growth are also examined.

Method, system, and apparatus for the growth of SiC and related or similar material, by chemical vapor deposition, using precursors in modified cold-wall reactor

Pressureless sintered silicon carbide ceramic bodies, having an equiaxed microstructure and an alpha crystalline habit can be produced by firing shaped bodies, containing finely divided silicon carbide, boron source such as boron carbide, carbon source such as phenolic resin and a temporary binder, at a sintering temperature of from about 1900° C. to about 2250° C., depending on the sintering atmosphere, under conditions such that a coating of carbon source is maintained on the finely divided silicon carbide, and sufficient boron is maintained within the shaped body during firing. Boron can be maintained within the shaped body by various techniques, such as the use of a "seasoned boat" or graphite container for the body being sintered, which has been saturated with boron by exposure to boron at or about the temperature of sintering. There is also disclosed a process for producing a sintered silicon carbide ceramic body, with or without the equiaxed crystal microstructure, from silicon carbide powders of alpha or beta crystal structure, or amorphous noncrystalline silicon carbide, or mixtures thereof.

Sintered alpha silicon carbide ceramic body having equiaxed microstructure

COMPOSITION AND METHOD FOR FORMING APROTECTIVE COATING ON CARBON-CARBON SUBSTRATES ABSTRACT OF THE INVENTION In accordance with the invention, a composition of matter is provided for forming a coating for protecting carbonaceous substrates from degradation at elevated temperatures. The composition of matter is a mixture of particulate silicon, silicon carbide and alumina. The mixture contains between about 40%and 50% silicon by weight of the total composition, between about 30% and 50% silicon carbide by weight of the total composition and between about 20% and 30% alumina by weight of the total composition. Amethod is provided for forming a primary protective coating on carbonaceous substrates utilizing the aforesaid mixture. An enhancement coating is provided for sealing the primary coating in applications where the substrate will be subjected to elevated temperatures and temperature cycling.

Composition and method for forming a protective coating on carbon-carbon substrates

Titanium diboride graphite composite articles are produced by mixing TiO2, petroleum coke and a binder to form a plastic dispersion. Articles are shaped by molding or extrusion and baked to carbonize the binder to form a baked carbon-TiO2 composite. The article is impregnated with a molten or dispersed boron compound, then heated to drive TiB2 forming reaction. The article is then further heated to a graphitizing temperature to form a graphite-TiB2 composite useful as a cathode component in a Hall aluminum reduction cell.

Titanium diboride-graphite composites

Shaped silicon carbide ceramic articles of high density, e.g., at least 90 percent of theoretical, are produced by cold pressing and sintering boron-containing high purity, submicron beta silicon carbide powder. The silicon carbide powder is produced preferably by gas phase reaction of silicon halide, e.g., silicon tetrachloride, carbon source reactant, e.g., halogenated hydrocarbon, and boron source reactant, e.g., boron trichloride, with a hydrogen plasma.

Submicron beta silicon carbide powder and sintered articles of high density prepared therefrom

Refractory metal diboride articles having an overall density of 50-90 percent of theoretical and a matrix of near theoretical density, e.g., 95-99 percent are described. They may be made by cold pressing and sintering an intimate mixture of submicron Group IVb metal diboride powder and finely divided solid hydrocarbon, e.g., microcrystalline petroleum wax. The hydrocarbon remains particulate in the cold pressed piece but is driven out by heat at the beginning of the sintering operation, thereby leaving voids which remain as gross pores surrounded by a dense matrix in the sintered article. Submicron boride powders capable of forming the dense matrix contain a minor proportion of a sintering or densifying aid such as carbon or a metal carbide such as titanium carbide, tungsten carbide, or boron carbide. The articles so produced are lighter in weight than non-porous articles of the same size, have high electrical conductivity and, by virtue of the dense matrix, have excellent resistance to chemical attack.

Frederick G. Stroke

Papers

Submicron beta silicon carbide powder and sintered articles of high density prepared therefrom

Porous refractory metal boride article having dense matrix