Patent ID: 9388509
Filing Date: 2016-07-12
CPC Classification: C30B,Y10T

Claim Text:
1. A method of forming polycrystalline SiC material comprising the steps of: (a) positioning bulk carbon at a first location inside of a graphite crucible, wherein the bulk carbon is gas-permeable and vapor-permeable; (b) positioning a mixture comprised of elemental silicon (Si) and elemental carbon (C) at a second location inside of the graphite crucible; (c) following steps (a) and (b), removing adsorbed gas, or moisture, or volatiles or some combination of adsorbed gas, moisture and volatiles from the mixture and the bulk carbon positioned inside of the graphite crucible by heating the mixture and the bulk carbon positioned inside of the enclosed crucible to a first temperature which is below the melting point of the elemental Si; (d) following step (c), forming as-synthesized silicon carbide (SiC) inside of the crucible by heating the mixture positioned inside of the enclosed crucible to a second temperature sufficient to initiate a reaction between the elemental Si and the elemental C of the mixture that forms the as-synthesized SiC inside of the crucible, wherein during each of steps (c) and (d) a vacuum pump evacuates at least the inside of the enclosed crucible; and (e) following step (d), forming polycrystalline SiC material inside of the gas-permeable and vapor-permeable bulk carbon by heating the as-synthesized SiC and the bulk carbon in the presence of a temperature gradient sufficient to cause the as-synthesized SiC to sublime and produce vapors that migrate under the influence of the temperature gradient into the bulk carbon where the vapors condense on the bulk carbon and react with the bulk carbon forming the polycrystalline SiC material, wherein a lowest temperature of the temperature gradient is a third temperature.