Abstract: There is disclosed a method for depositing a diamond film on a substrate which utilizes high density direct current glow discharge at a glow-arc transition region to form plasma between a cathode and an anode in a reactor, wherein the cathode maintains its temperature at a range of 2,100 to 2,300.degree. C. and is composed of a plurality of U-shaped filaments which are aligned parallel to one another to form an array and each of which is made by bending a conductive wire.

Abstract: A invention provides a method for production of diamond particles. The solvent metallic disk of a starting material specimen used in this diamond synthesis is divided into two layers. An intermediate layer is interposed between the two solvent metallic layers, so that the diamond crystals, formed on the two solvent metallic surfaces in contact with graphite disks and influenced by gravity, are not floated on the upper surface of the solvent metallic disk but grown at their positions in the individual solvent metallic layers at which they were nucleated. Hence, the method of this invention results in formation of the same number of diamond products, having the same size and desired good quality, on opposed surfaces or the upper and lower surfaces of the solvent metallic disk. The intermediate layer is a thin disk made of tungsten or molybdenum and having a thickness ranged from 10 .mu.m to 100 .mu.m.

Abstract: A process for preparing large granules of cubic boron nitride from hexagonal boron nitride, which comprises using a binary alloy of Al-Mg as a catalyst under high temperature and pressure wherein binary alloy can be obtained by gas spraying of the alloy melt or grinding the agglomerates and easily treated due to its low activity, whereby the resultant cubic boron nitride crystal has large size without impurities.