Sintered dense silicon carbide
AssigneeGeneral Electric Company
InventorSvante Prochazka
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Abstract
A method of making a dense silicon carbide ceramic is disclosed involving the steps of homogeneously dispersing silicon carbide with a sufficient amount of a boron containing additive and a carbonaceous additive, forming the powder mixture into a shaped green body and then sintering the body in a controlled atmosphere and in the absence of external pressure at a temperature of about 1900.degree.-2100.degree. C. such that density of the body is at least 85% of the theoretical density of silicon carbide. The complex shaped silicon carbide product formed thereby is also disclosed.
Claims23
A method of making a pre-shaped dense sintered silicon carbide ceramic article comprising the steps of:
- a. forming a homogeneous dispersion of a submicron powder of
- 1. .beta.-silicon carbide,
- 2. a boron containing compound in an amount equivalent to about 0.3-3.0% by weight of boron based on said silicon carbide, and
- 3. an elemental carbon source selected from the group consisting of elemental carbon and a carbonaceous additive in an amount equivalent to 0.1-1.0% by weight of elemental carbon based on said silicon carbide,
- b. shaping the homogeneous dispersion into a green body substantially of the form of said desired final pre-shaped sintered article and of dimensions larger than those of said desired sintered article by the amount of sintering shrinkage, and
- c. sintering the green body in an inert atmosphere chemically-inert with respect to silicon carbide at atmospheric pressure or below atmospheric pressure at a temperature of about 1900.degree. -2100.degree. C until the ceramic article has a density of at least 85% of theoretical, said carbonaceous additive being pyrolyzable to produce said elemental carbon at a temperature below sintering temperature.
A method of making a pre-shaped dense sintered silicon carbide ceramic article comprising the steps of:
- a. forming a substantially homogeneous first dispersion of a submicron powder of .beta.-silicon carbide, a boron containing additive in an amount equivalent to about 0.3-3.0% by weight of boron based on said silicon carbide,
- b. incorporating in said first dispersion a carbonaceous additive in an amount equivalent to 0.1-1.0% by weight of elemental carbon after pyrolysis based on said silicon carbide, to form a second dispersion,
- c. pyrolyzing said second dispersion at a temperature which decomposes the carbonaceous additive to elemental carbon.
- d. shaping the resulting pyrolyzed dispersion into a green body substantially in the form of said desired pre-shaped sintered article and of dimensions larger than those of said desired sintered article by the amount of sintering shrinkage, and
- e. sintering the green body in an inert atmosphere chemically inert with respect to silicon carbide at atmospheric pressure or below atmospheric pressure at a temperature of about 1900.degree.-2100.degree. C until the ceramic article has a density of at least 85% of theoretical.
A pre-shaped sintered ceramic article consisting essentially of silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, the sintered ceramic article having a density of at least 85% of theoretical.
A pre-shaped sintered ceramic article consisting essentially of .beta.-silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, the sintered ceramic article having a density of at least 85% of theoretical and a fine grained uniform microstructure.
A pre-shaped sintered silicon carbide ceramic article consisting essentially of .beta.-silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, said ceramic article having a density of at least 95% of theoretical and a uniform grain size of less than 10 microns.
Dependencies are inferred from the claim text.