Method for manufacturing silicon carbide bodies

Claim 1

A method for manufacturing a reaction bonded silicon carbide body comprising: heating, in a vacuum or an inert atmosphere, to at least the melting temperature of elemental silicon, a porous compact consisting essentially of a uniform mixture of silicon carbide grain and finely divided elemental carbon while said compact is in contact with a mixture of finely divided elemental silicon and a small amount of finely divided uniformly distributed elemental carbon, whereby upon said heating a portion of the elemental silicon in the silicon-carbon mixture reacts with the carbon in said silicon-carbon mixture to form a friable, porous matrix of silicon carbide which guides the flow of molten elemental silicon from the mixture into said porous compact wherein at least some of the molten silicon reacts with the carbon in said compact to form additional silicon carbide thereby to provide a reaction bonded silicon carbide body.

Claim 2

A method for manufacturing a reaction bonded silicon carbide body comprising: heating, in a vacuum or an inert atmosphere, to at least the melting temperature of elemental silicon, a porous compact consisting essentially of a uniform mixture of silicon carbide grain and finely divided elemental carbon while said compact is in contact with a mixture of finely divided elemental silicon and a small amount of finely divided uniformly distributed elemental carbon, whereby upon said heating a portion of the elemental silicon in the silicon-carbon mixture reacts with the carbon in said silicon-carbon mixture to form a friable, porous matrix of silicon carbide which guides the flow of molten elemental silicon from the mixture into said porous compact wherein at least some of the molten silicon reacts with the carbon in said compact to form additional silicon carbide thereby to provide a reaction bonded silicon carbide body.

Claim 5

A method for manufacturing a reaction bonded silicon carbide body comprising: (1) forming an assembly of two compacts in contact with each other, one of said compacts consisting essentially of a uniform mixture of from about 70% to 95% by weight silicon carbide grain and the remainder finely divided elemental carbon and the other of said compacts consisting essentially of a uniform mixture of from about 87% to 97% by weight finely divided elemental silicon and the remainder finely divided elemental carbon; (2) heating said assembly in a vacuum or an inert atmosphere to the melting temperature of silicon whereby a portion of said elemental silicon reacts with the carbon in said second-mentioned compact to form a friable, porous, silicon carbide matrix and whereby the remainder of said silicon permeates said first-mentioned compact wherein at least at a portion of said silicon reacts with the carbon in said first-mentioned compact such that said first-mentioned compact is converted to a reaction bonded silicon carbide body; and (3) thereafter removing said friable, porous, silicon carbide matrix from said reaction bonded carbide body.

Claim 6

A method for manufacturing a reaction bonded silicon carbide body comprising: (1) forming an assembly of two compacts in contact with each other, one of said compacts consisting essentially of a uniform mixture of from about 70% to 95% by weight silicon carbide grain and the remainder finely divided elemental carbon and the other of said compacts consisting essentially of a uniform mixture of from about 87% to 97% by weight finely divided elemental silicon and the remainder finely divided elemental carbon; (2) heating said assembly in a vacuum or an inert atmosphere to the melting temperature of silicon whereby a portion of said elemental silicon reacts with the carbon in said second-mentioned compact to form a friable, porous, silicon carbide matrix and whereby the remainder of said silicon permeates said first-mentioned compact wherein at least at a portion of said silicon reacts with the carbon in said first-mentioned compact such that said first-mentioned compact is converted to a reaction bonded silicon carbide body; and (3) thereafter removing said friable, porous, silicon carbide matrix from said reaction bonded carbide body.

Claim 9

A method for manufacturing a reaction bonded silicon carbide body comprising: (1) forming an assembly of two compacts in contact with each other, one of said compacts consisting essentially of a uniform mixture containing from about 75 to 95 parts by weight silicon carbide grain, from about 5 to 25 parts by weight finely divided elemental carbon and from about 5 to 15 parts by weight organic binder and the other of said compacts consisting essentially of a uniform mixture containing from about 90 to 97 parts by weight finely divided elemental silicon, from about 3 to 10 parts by weight finely divided elemental carbon and from about 3 to 10 parts by weight organic binder; (2) heating said assembly to a temperature sufficient to decompose the organic binder in said compacts; (3) heating said assembly in a vacuum or an inert atmosphere to the melting temperature of said silicon whereby a portion of said silicon reacts with the carbon in said second-mentioned compact to form a friable, porous, silicon carbide matrix and whereby the remainder of said silicon permeates said first-mentioned compact wherein at least a portion of said silicon reacts with the carbon in said first-mentioned compact such that said first-mentioned compact is converted to a reaction bonded silicon carbide body; and (4) thereafter removing said friable, porous, carbide matrix from said reaction bonded silicon carbide body.

Claim 10

A method for manufacturing a reaction bonded silicon carbide body comprising: (1) forming an assembly of two compacts in contact with each other, one of said compacts consisting essentially of a uniform mixture containing from about 75 to 95 parts by weight silicon carbide grain, from about 5 to 25 parts by weight finely divided elemental carbon and from about 5 to 15 parts by weight organic binder and the other of said compacts consisting essentially of a uniform mixture containing from about 90 to 97 parts by weight finely divided elemental silicon, from about 3 to 10 parts by weight finely divided elemental carbon and from about 3 to 10 parts by weight organic binder; (2) heating said assembly to a temperature sufficient to decompose the organic binder in said compacts; (3) heating said assembly in a vacuum or an inert atmosphere to the melting temperature of said silicon whereby a portion of said silicon reacts with the carbon in said second-mentioned compact to form a friable, porous, silicon carbide matrix and whereby the remainder of said silicon permeates said first-mentioned compact wherein at least a portion of said silicon reacts with the carbon in said first-mentioned compact such that said first-mentioned compact is converted to a reaction bonded silicon carbide body; and (4) thereafter removing said friable, porous, carbide matrix from said reaction bonded silicon carbide body.

Claim 15

A method for manufacturing a body containing at least about 60% by weight silicon carbide and the remainder substantially all elemental silicon, said method comprising heating, in a vacuum or an inert atmosphere, to at least the melting temperature of elemental silicon for from one-half to six hours, a compact having a porosity such that from about 20% to 50% by volume thereof consists of voids, and consisting essentially of a uniform mixture of from about 70% to 95% by weight silicon carbide grain and from about 5% to 30% by weight finely divided elemental carbon, said heating being performed while said compact is in contact with a uniform mixture of from about 87% to 97% by weight finely divided elemental silicon and the remainder finely divided carbon, the amount of elemental silicon being greater than that stoichiometrically required to react with the total of the carbon in said silicon-carbon mixture and in said compact.

Claim 16

A method for manufacturing a body containing at least about 60% by weight silicon carbide and the remainder substantially all elemental silicon, said method comprising heating, in a vacuum or an inert atmosphere, to at least the melting temperature of elemental silicon for from one-half to six hours, a compact having a porosity such that from about 20% to 50% by volume thereof consists of voids, and consisting essentially of a uniform mixture of from about 70% to 95% by weight silicon carbide grain and from about 5% to 30% by weight finely divided elemental carbon, said heating being performed while said compact is in contact with a uniform mixture of from about 87% to 97% by weight finely divided elemental silicon and the remainder finely divided carbon, the amount of elemental silicon being greater than that stoichiometrically required to react with the total of the carbon in said silicon-carbon mixture and in said compact.