| 摘要 |
60SD00282 PROCESS FOR PREPARING POLYCRYSTALLINE CUBIC BORON NITRIDE AND RESULTING PRODUCT The present invention is directed to an HP/HT process for making polycrystalline CBN particles and compacts from GBN in the substantial absence of bulk catalytically-active material. The inventive process modulates the HP/HT conditions of the process and comprises incorporating into said GBN, non-BN atoms or clusters thereof in an amount for at least lowering the pressure required for making said polycrystalline CBN in the absence of said atoms or clusters thereof. The presence of non-BN atoms/clusters or foreign atoms can be termed "doping" and should be contrasted to the formation of a "composite". 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 foreign atoms 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.
|
