Abstract Boric oxide fibers having a maximum diameter of about 10 microns are heated in an ammonia atmosphere under such conditions as to produce partially nitrided fibers consisting essentially of B, N, O and H wherein the N is present to the extent of from about 35 percent to about 55 percent. The partially nitrided fibers are then heated in an inert atmosphere at a temperature of at least about 1800*C while simultaneously subjecting the fibers to sufficient longitudinal tension as to at least prevent longitudinal shrinkage of the fibers and preferably to cause elongation of the fibers during heating. The resulting fibers, consisting essentially of boron nitride, are of high purity and are characterized by a relatively high Young''s modulus of elasticity, which renders them especially suitable for reinforcing plastic, ceramic or metal matrices in the preparation of fiber reinforced composites.
A yarn consisting of a plurality of fibers as set forth in claim 1.
Claim 2
Dependent Claim
14 words
A yarn as set forth in claim 2 which consists essentially of continuous filaments.
Claim 3
Dependent Claim
14 words
A yarn as set forth in claim 2 which consists essentially of staple fibers.
Claim 4
Dependent Claim
38 words
A reinforced composite comprising a matrix of a material selected from the group consisting of plastics, ceramics and metals, said matrix having embedded therein a sufficient amount of fibers as set forth in claim 1 to effect reinforCement.
Claim 5
Dependent Claim
22 words
A polycrystalline fiber as set forth in claim 1 having a maximum Young''s modulus of elasticity of about 75 X 106 psi.