Abstract: Ceramic composites of silicon carbide (SiC) grains and boron carbide (B.s4 C) grains which are uniformly coated with SiC are produced by reacting stoichiometric mixtures of silicon boride (SiB.sub.4, SiB.sub.6) and carbon (graphite or carbon black) in situ.

Abstract: A process for the production of dense polycrystalline silicon carbide shaped articles, includes the steps: (a) heating a powder compact containing silicon carbide and alumina or a precursor thereof together with a secondary sintering assist, to an intermediate temperature for an extended dwell, and then (b) heating the product of step (a) to a higher temperature for sufficient time to produce a dense polycrystalline silicon carbide product. The secondary sintering assist includes one or more rare earths or their precursors, for example scandia, yttria or dysprosia.

Abstract: A method for producing a crack-free recrystallized silicon carbide body, icluding the steps of:a) providing a raw powder batch including:i) at least 40 w/o fine fraction having a particle size of less than 10 microns, the fine grain fraction including silicon carbide and fine free carbon, wherein the fine free carbon is present in an amount of at least 0.10 w/o of the raw batch, the fine free carbon having a surface area of at least 10 m.sup.2 /g,ii) at least 40 w/o coarse grain fraction having a particle size of at least 30 microns, the coarse grain fraction including silicon carbide and coarse free carbon, wherein the coarse free carbon is present in an amount of at least 0.10 w/o of the coarse grain fraction,the raw batch having a total silica content of at least 0.5 w/o,the raw batch having a total silicon carbide content of at least 96 w/o,b) forming the raw batch into a green body, andc) recrystallizing the green body to provide a recrystallized silicon carbide body having a density of between 2.

Abstract: A composite sintered body of silicon carbide and silicon nitride having a nano-composite structure in which fine SiC particles are dispersed in Si.sub.3 N.sub.4 particles and grain boundaries and fine Si.sub.3 N.sub.4 particles are dispersed in SiC particles is produced by (a) adding at least one sintering aid, boron and carbon to a mixed powder of silicon carbide and silicon nitride to form a green body, the sintering aid being (i) Al.sub.2 O.sub.3 or AlN and/or (ii) at least one oxide of an element selected from Groups 3A and 4A of the Periodic Table, and (b) sintering the green body by HIP or by a high-temperature normal sintering method.

Abstract: A process for sealing an end face of a ceramic honeycomb structure includes introducing an expansive material which can be burned off, into through-holes not to be sealed, among through-holes of the honeycomb structure, expanding the expansive material to temporarily seal the through-holes not to be sealed, at their ends, filling a sealant into ends of through-holes to be sealed, and burning off the expansive material and sintering the sealant at the same time.

Abstract: A process of producing high density articles of boron carbide and all transition metal carbides that optionally contain 1 to 50% by volume of borides is disclosed. The process involves the steps of homogeneously mixing boron carbide, titanium oxide and carbon powders, or homogeneously mixing transition metal carbide with its oxide, boron carbide and carbon when sintering transition metal carbides, forming the powder mixtures into a shaped green body, and sintering the body in a controlled atmosphere at a temperature of from 1900.degree. C. to 2100.degree. C. The shaped articles thus obtained have the theoretical density of at least 95% and preferably greater than 99% of theoretical density of selected composite and flexural strength of at least 350 MPa, preferably grater than 450 MPa.

Abstract: A sintered silicon carbide (SiC) body prepared by a process which contains the steps of: (a) preparing a raw batch containing: (i) a raw silicon carbide mixture containing about 10 to about 90 weight percent of an .alpha.-phase SiC powder and about 90 to about 10 weight percent of a .beta.-phase SiC powder; (ii) aluminum oxide (Al.sub.2 O.sub.3) powder, about 3 to 15 weight percent of the raw silicon carbide mixture; (iii) yttrium oxide (Y.sub.2 O.sub.3) powder, about 2 to 10 weight percent of the raw silicon carbide mixture; (iv) an organic binding agent and a dispersing agent; and (v) deionized water; (b) drying the raw batch to form a green body; (c) heating the green body at temperatures between about 400.degree. and 800.degree. C. to remove the organic binding agent and the dispersing agent; and (d) subjecting the green body to a two-stage pressureless sintering process, first at a first sintering temperature between about 1,800.degree. and about 1,950.degree. C. for 0.5 to 8.

Abstract: A silicon carbide ceramic body having a high degree of lubricity as a result of large graphite inclusions in the body. The graphite inclusions have an average size of at least about 100 micrometers. The graphite-loaded silicon carbide component is preferably formed by spray drying graphite particles independent of the silicon carbide, blending the graphite agglomerates and silicon carbide to form a raw batch, forming the raw batch into a green body, and sintering the green body to produce a graphite-loaded silicon carbide ceramic body having good density and good strength.