Fabrication of small dense silicon carbide spheres

A process for producing sintered spherical or nominally spherical particles of polycrystalline silicon carbide having a density greater than 80% of the theoretical density for silicon carbide and having a diameter ranging from about 5 microns to about 2000 microns which consists essentially of forming a slurry comprised of sinterable silicon carbide powder, a liquid medium and an agglomerate-forming binder in solution and/or suspension in said liquid medium, said sinterable silicon carbide powder having an average particle size which is submicron and which consists essentially of silicon carbide, a boron additive selected from the group consisting of boron and boron carbide in an amount equivalent to from about 0.3% by weight to about 3% by weight of boron based on said silicon carbide, and an amount of a carbonaceous additive equivalent to from about 0.1% by weight to about 5% by weight of free carbon based on said silicon carbide, said carbonaceous additive being selected from the group consisting of free carbon, a carbonaceous organic material which completely decomposes at a temperature ranging from 50.degree. C. up to 450.degree. C. to free carbon and gaseous product of decomposition, and mixtures thereof, spraying said slurry into droplets into a spray dryer wherein said droplets are dried into spherical or nominally spherical agglomerates, said agglomerate-forming binder being present in an amount of at least about 1% by weight of said agglomerate and at least sufficient to form said agglomerate, said agglomerate-forming binder being thermally removable at an elevated temperature ranging up to 450.degree. C. leaving no significant amount thereof, and sintering said agglomerates at a temperature ranging from about 1900.degree. C. to about 2300.degree. C. at about or below atmospheric pressure in a vacuum or atmosphere which has no significant deleterious effect thereon, said agglomerates being of a size which produces said sintered particles, said slurry being characterized as sprayable into droplets into a hot air spray dryer wherein said droplets are dried into spherical or nominally spherical agglomerates.

A process for producing sintered spherical or nominally spherical particles of polycrystalline silicon carbide having a density greater than 80% of the theoretical density for silicon carbide and having a diameter ranging from about 100 microns to about 10,000 microns which consists essentially of cascading or rolling sinterable silicon carbide powder and contacting said powder with an effective amount of a spray or mist of liquid to produce spherical or nominally spherical agglomerates, said sinterable silicon carbide powder having an average particle size which is submicron and which consists essentially of silicon carbide, a boron additive selected from the group consisting of boron and boron carbide in an amount equivalent to from about 0.3% by weight to about 3% by weight of boron based on said silicon carbide, and an amount of a carbonaceous additive equivalent to from about 0.1% by weight to about 5% by weight of free carbon based on said silicon carbide, said carbonaceous additive being selected from the group consisting of free carbon, a carbonaceous organic material which completely decomposes at a temperature ranging from 50.degree. C. up to 450.degree. C. to free carbon and gaseous product of decomposition, and mixtures thereof, and sintering said spherical or nominally spherical agglomerates at a temperature ranging from about 1900.degree. C. to about 2300.degree. C. at or below atmospheric pressure in a vacuum or atmosphere which has no significant deleterious effect thereon, said spherical or nominally spherical agglomerates being of a size which produces said sintered particles.