Method of obtaining a filament-containing composite with a boron nitride coated matrix

Claim 1

A process for producing a composite containing a layer of boron nitride coated filaments embedded in a ceramic matrix which comprises the following steps: (a) providing matrix-forming ceramic material; (b) admixing said matrix-forming material with an organic binding material; (c) forming the resulting mixture into a tape; (d) depositing a coating of boron nitride on a filament leaving no significant portion thereof exposed, said filament having a diameter of at least about 50 microns and a length at least about 10 times its diameter; (e) forming a plurality of said boron nitride coated filaments into a layer wherein said coated filaments are spaced from each other and at least substantially parallel to each other; (f) disposing said layer of coated filaments intermediate the faces of two of said tapes forming a layered structure; (g) laminating the layered structure to form a laminated structure; (h) heating said laminated structure to remove said organic binding material leaving no significant deleterious residue; and (i) hot pressing the resulting porous structure at a sufficient temperature under a sufficient pressure for a sufficient period of time to consolidate said structure to produce said composite having a porosity of less than about 5% by volume, said composite containing no significant reaction product of said coated filaments and said matrix, said matrix having a thermal expansion coefficient which ranges from lower than that of said coated filaments to less than about 15% higher than that of said coated filaments, at least about 10% by volume of said composite being comprised of spaced boron nitride coated filaments.