C - Chemistry – Metallurgy – 04 – B
Patent
C - Chemistry, Metallurgy
04
B
C04B 35/58 (2006.01) B01J 3/06 (2006.01) C01B 21/064 (2006.01) C04B 35/5831 (2006.01)
Patent
CA 2056509
PROCESS FOR PREPARING POLYCRYSTALLINE CUBIC BORON NITRIDE AND RESULTING PRODUCT ABSTRACT OF THE DISCLOSURE The present invention is directed to an HP/HT process for making polycrystalline CBN particles and compacts from graphitic boron nitride (GBN) (including PBN, HBN, and mixtures) in the substantial absence of bulk catalytically- active material. The inventive process modulates the HP/ET conditions of the process and comprises doping said GBN with between about 0.1 and 50 weight-% of non-BN atoms or elusters thereof, an amount thereof being incorporated into the CBN lattice for at least lowering the pressure required for making said polycrystalline CBN in the absence of said atoms or clusters thereof The plesence of non-BN atoms/clusters or foreign atoms is termed "doping" and should be contrasted to the formation of a "composite" as disclosed in commonly-assigned U.S.S.N. 367,299, filed June 16, 1989. Doping of GBN with foreign atoms in accordance with the present invention involves the atomic level dispersion of foreign atoms independent of concentration. Thus, for present purposes, it is the size of foreign atoms and their distribution that determines whether a doped GBN material for processing in accordance with the present invention has been made or whether a conventional composite has been made. A composite, it will be appreciated, refers to the bulk addition of foreign material to GBN. In this regard, it should be understood that the same percentage of foreignatoms may be defined as suitable for producing a "composite" conventionally, but that this definition refers to macroscopic (particle size) mixtures; whereas, the same percentage may be termed a "doped" mixture for present purposes if the foreign atoms are present in an atomic level dispersion of atoms or clusters thereof. The resulting CBN product forms yet another aspect of the present invention. Another technique for moderating the HP/HT conditions in forming the CBN comprising coforming GBN atoms or clusters thereof isolated from each other by non-GBN clusters or particles. For present purposes, "coforming" means that the GBN and non-GBN materials are formed in the stated physical relationship simultaneously or at the same time. Acceptable techniques for this coformation include, for example, chemical vapor deposition, solgel techniques, polymer pyrolysis, and combustion synthesis techniques.
Company General Electric
Craig Wilson And Company
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