Abstract: Rhombohedral system boron nitride is produced by heating a boron material selected from the group consisting of boron oxide, boric acid and an oxygen-containing boron compound capable of forming boron oxide when heated, at a temperature of from 1200.degree. to 2100.degree. C. to vaporize boron oxide and reacting the vaporized boron oxide with hydrogen cyanide or cyanogen gas.

Abstract: A process for preparing cubic boron nitride comprises heating hexagonal boron nitride and magnesium boron nitride at a temperature of at least 1350.degree. C. under a pressure at which the cubic boron nitride is thermodynamically stable, whereby the cubic boron having high strength and high purity can readily be obtainable. Also disclosed is a process for the preparation of magnesium boron useful as a starting material for the above process. This process comprises mixing hexagonal boron nitride and magnesium nitride or metal magnesium in a molar ratio of hexagonal boron nitride/magnesium being at least 0.6, and heating the mixture thus obtained, at a temperature of from 950.degree. to 1250.degree. C. under atmospheric pressure in a non-oxidizing atmosphere, e.g. a nitrogen atmosphere.

Abstract: Fibrous potassium titanate comprises heating to a temperature of 950.degree. C. to 1300.degree. C. potassium titanate of the general formula K.sub.2 O.nTiO.sub.2 in which n is from 3 to 5, or a mixture of materials from which potassium titanate is formed, to form is manufactured by decomposition a solid phase of potassium hexatitanate and a liquid phase of potassium titanate of the general formula K.sub.2 O.nTiO.sub.2 (2.ltoreq.n.ltoreq.3), cooling said potassium hexatitanate and potassium titanate slowly to a temperature of 900.degree. C. to 950.degree. C., and controlling the rate of said cooling to cause a bonding of said potassium hexatitanate and said potassium titanate to form a solid phase of potassium tetratitanate fibers, whereby potassium titanate according to said general formula in which n is from 4 to 6 is caused to grow in single crystal form.

Abstract: A diamond powder is produced by a shock compressing method using a carbon precursor obtained by an organic compound such as furan resin, its derivative, a thermosettable resin, as a carbon source.

Abstract: SIALON sintered product having the formulaSi.sub.6-z Al.sub.z O.sub.z N.sub.8-z(z is 0 to 4.2) is produced by sintering a molded product of the starting materials for SIALON in the condition of covering the surface of said molded product with a mixed powder of Si.sub.3 N.sub.4 and SiO.sub.2 as main components in nitrogen gas atmosphere.

Abstract: A process for producing cubic system boron nitride comprises contacting calcium or strontium boron nitride with hexagonal system boron nitride and heating at higher than 1,450.degree. C. under the thermodynamically stable pressure for cubic system boron nitride.

Abstract: A single crystal of yttrium-iron garnet or solid solution comprising aluminum oxide component, gallium oxide component, iron oxide and/or the other rare earth oxide component is produced by a floating zone method.

Abstract: A single crystal of lanthanum hexaboride is used as a tip of a thermionic emission cathode.

Abstract: Fibrous alkali metal titanate is prepared by mixing 5-50 mole % of an alkali metal titanate or an alkali metal titanate forming components with a flux of an alkali tungstate or molybdate, and heating the mixture at 700.degree.-1,350.degree. C to grow the fibrous product in the molten flux mixture.