Abstract: Composite materials, articles and cutting tools are prepared by densification to form a body comprising whiskers of hard refractory transition metal carbides, nitrides or carbonitrides uniformly distributed in a two-phase silicon nitride matrix. A first phase comprises silicon nitride grains and the second phase is an intergranular phase formed from one or more suitable densification aids. Optionally, dispersoid particles and/or polycrystalline fibers may also be incorporated. The preferred composite article or cutting tool has a fracture toughness equal to or greater than about 3.5 MPa.m.sup.1/2.

Abstract: Single crystal whiskers of carbides, nitrides and carbonitrides of Ti, Zr, Hf, V, Nb, Ta, and W coated with one or more layers of different carbides, nitrides, or carbonitrides of Ti, Zr, Hf, Nb, Ta, or W or oxides of Al, Zr, or Hf. A process for the whisker production is also disclosed.

Abstract: A reactor for producing single crystal metal carbide, nitride, or carbonitride whiskers, where the metal is one or more of Ti, Zr, Hf, Nb, Ta or W. The reactor walls and inner fixtures provide the substrate surfaces, greatly increasing the surface area available for whisker growth. Preferred substrate materials are nickel or high nickel alloy coated with TiC or TiN, or, for carbide or carbonitride whiskers, nickel impregnated graphite. An alternate embodiment provides a collecting chamber and vibrating means to mechanically detach whiskers, allowing for more efficient batch, or continuous operation.

Abstract: A method for coating single crystal whiskers of carbides, nitrides or carbonitrides of Ti, Zr, Hf, V, Nb, Ta, or W with one or more layers of a carbide, nitride or carbonitride of Ti, Zr, Hf, Nb, Ta, or W, or oxides of Al, Zr, or Hf. The method involves flowing past the whiskers at about 1025.degree.-1125.degree. C. a mixture of hydrogen and one of the following gaseous mixtures: Group I comprises one or more of Ti, Zr, Hf, Nb, Ta, or W hhalides mixed with one or more of N.sub.2, NH.sub.3, or suitable free carbon forming aliphatic hydrocarbons. The atomic ratio of carbon and/or nitrogen to metal is about 5:1-16:1, and the volume ratio of hydrocarbon and/or N.sub.2 and/or NH.sub.3 to H.sub.2 is about 1:5 to 1:20. Group II comprises one or more Al, Zr, or Hf halides mixed with one or more suitable oxygen donor gases, in proportions selected to form the desired metal oxide.

Abstract: A chemical vapor deposition process for producing single crystal whiskers of metal carbides, nitrides, or carbonitrides involving flushing a reaction chamber including a suitable substrate surface heated to 1025.degree.-1125.degree. C., and flowing reactant gases past the substrate to form whiskers. The reactants comprise a halide of Ti, Zr, Hf, Nb, Ta or W and one or more of nitrogen, ammonia and suitable aliphatic hydrocarbons. The atomic ratio of carbon and/or nitrogen to metal is about 5:1 to 16:1; the volume ratio of hydrocarbon and/or nitrogen and/or ammonia to hydrogen is about 1:50-1:20. The preferred substrate materials are nickel or a high nickel alloy coated with TiC or TiN, or, for carbide whiskers, nickel impregnated graphite. The reactor walls and internal fixtures preferably provide the substrate surfaces. A more efficient batch process and a continuous process for whisker growth are disclosed.