METHOD OF PURIFICATION OF CUBIC BORON NITRIDE Russian patent published in 1999 - IPC

FIELD: technology of superhard materials. SUBSTANCE: method includes grinding of product of synthesis of cubic boron nitride containing alpha-boron nitride, catalyst, graphite, cubic boron nitride; placing of product into sleeve of stainless of stainless steel; washing with water; fusing together with alkali metal hydroxide or their mixture at 300- 350 C, with mixture-hydroxide ratio of 1(4-6); washing up to obtaining neutral reaction; filtering; placing again in sleeve and adding of sodium nitrate with mixture-sodium nitrate ratio of 1:3; heating up to 450-500 C for 15-60 min; adding of 1 g of alkali metal hydroxide per gram of mixture; reduction of temperature down to 300-350 C and holding at this temperature for 15-30 min; washing of sediment. Data of X-ray phase analysis shows absence of impurities in purified boron nitride. EFFECT: higher efficiency of purification due to reduced consumption of reagents by factor of 1.5-2 and purification duration by factor of 2. 3 cl, 4 ex