Abstract: Dense, essentially flawless, complex refractory or metal shapes are formed by preparing a casting slip of fine refractory or metal powder wherein the slip liquid preferably contains 0.1 to 10% by weight of a hydrogen bond forming compound, casting the slip, freezing the cast slip, removing the solid form from the mold, drying, and finally firing to sinter the refractory or metal particles.

Abstract: High density, sintered refractory articles composed of: 60 to 98% by weight of boron carbide and 2 to 40% by weight of silicon carbide, and 0 to 10% by weight of aluminum. As a result of the composition, products with densities in excess of 94% of theoretical can be produced by cold pressing followed by a pressureless heat treatment.

Abstract: A castable slip of a bimodal distribution of silicon carbide particles is prepared, the slip preferably containing a water miscible curable resin. A shaped body is cast in a plaster of paris mold which also preferably contains a small amount of a water soluble polymer. The casting and mold are then heat treated to increase the strength of the green casting. In a preferred embodiment of the invention the resin in the slip is cured by the heat treating step. The mold is then removed by decomposing the mold material, preferably by dipping the mold in acid to attack the mold material (e.g. the water soluble polymer or the plaster of paris itself). The cured resin in the casting is sufficiently resistant to attack by the acid to survive the mold removal. In an alternative embodiment the silicon carbide body is heated to a sufficiently high temperature (e.g. 650.degree.-750.degree. C) to slightly oxidize the SiC and to strengthen the green casting.

Abstract: A process for fabricating high density aluminum modified boron carbide compositions comprising the steps of blending specific quantities of powdered boron carbide and powdered aluminum together with a small quantity of temporary organic binder, preforming this mixture to the desired shape with high pressure at room temperature, followed by final densification of the finished product at a temperature below the sintering temperature of boron carbide and at a pressure as low as 500 psi. The resulting compositions are near theoretical density and possess a degree and type of strength which make them well suited as protective armor against penetration by ballistic projectiles.

Abstract: Silicon nitride based refractory articles with flexural strengths at room temperature of up to 150,000 p.s.i. and at 1375.degree. C of up to about 117,000 p.s.i. result when mixtures of 80 to 98.5% by weight of silicon nitride, 1 to 15% by weight of yttrium oxide, and 0.5 to 10% by weight of thorium oxide are pressure sintered according to conventional methods.

Abstract: Silicon carbide articles are formed by wet milling a mixture of silicon carbide having an average particle size less than 10 microns, and colloidal graphite; eliminating powder agglomerates larger than 325 mesh (U.S. Standard Sieve Series); drying the milled powder and pressing it to the desired shape; and finally, firing the preform at approximately 2000.degree. C. in the presence of silicon, converting the graphite to silicon carbide.

Abstract: High density sintered silicon carbide articles are formed by first forming a green blank or billet out of powdered silicon carbide, heat treating the billet to cause it to lightly sinter and become partially densified, shaping the billet to the desired final dimensions and configuration, and fully sintering and densifying the partially sintered shape by heat alone or by heat in the presence of silicon. The product of the process possesses high mechanical strength and may be very fine grained.