Abstract: CBN abrasive grains contain 0.01% by weight or more of Si and, the majority of the surfaces of its grains consist of {111} planes. In the method for producing CBN abrasive grains, a C source, an Si source, and at least one member selected from the group consisting of alkali hydride, alkali-earth hydride, and a synthetizing catalyst of CBN which may be the alkali hydride and alkali-earth hydride, are mixed together with HBN and are subjected to the treatment.

Abstract: Cubic boron nitride crystals are grown by subjecting reaction materials of low pressure phase boron nitride, a solvent material, and cubic boron nitride seeds to pressure and temperature conditions in the cubic boron nitride-stable region. The reaction materials are in the form of a pair of a superimposed solvent material plate and a low pressure phase boron nitride plate or a pile made of a plurality of the pairs of the superimposed solvent material plate and low pressure phase boron nitride plate, and a plurality of the seeds are disposed on either one or each of the confronting surfaces of the pair of the superimposed solvent material plate and low pressure phase boron nitride plate. Alternatively, the reaction materials are in the form of a plate made of a mixture of the solvent material and the low pressure phase boron nitride or a pile made of a plurality of the mixture plates, and a plurality of the seeds are disposed on a surface of each plate. The seeds have a particle size of not larger than 150 .

Abstract: A boron nitride type compound of the formula: LiMBN.sub.2 where M is calcium or barium and other similar compounds are provided. These compounds are prepared by heating a mixture of (i) finely divided Li.sub.3 N or metallic lithium, (ii) finely divided alkaline earth metal nitride selected from Ca.sub.3 N.sub.2, Mg.sub.3 N.sub.2, Sr.sub.3 N.sub.2, Ba.sub.3 N.sub.2 and Be.sub.3 N.sub.2, and/or an alkaline earth metal selected from Ca, Mg, Sr, Ba and Be, and (iii) hexagonal boron nitride at 800.degree. to 1,300.degree. C. in an inert gas or ammonia atmosphere thereby to react the ingredients (i), (ii) and (iii) with each other in a molten state, and then, cooling the reaction product to be solidified. The above-mentioned compounds are useful as a catalyst for use in the production of cubic boron nitride from hexagonal boron nitride.

Abstract: Diamond crystals are grown by subjecting reaction materials of nondiamond carbon, a solvent metal, and diamond seeds to pressure and temperature conditions in the diamond-stable region. The reaction materials are in the form of a pair of a superimposed solvent metal plate and a nondiamond carbon plate or a pile made of a plurality of the pairs of the superimposed solvent metal plate and nondiamond carbon plate, and a plurality of the seeds are disposed on either one or each of the confronting surfaces of the pair of the superimposed solvent metal plate and nondiamond carbon plate. Alternatively, the reaction materials are in the form of a plate made of a mixture of the solvent metal and the nondiamond carbon or a pile made of a plurality of the mixture plates, and a plurality of the seeds are disposed on a surface of each plate. The seeds have a particle size of not larger than 50 .mu.