BN ceramics are mechanically durable, thermally stable, highly wear-resistant, and manufactured using advanced ceramic processes.

Abstract

The invention relates to a method for producing high-purity boron nitride (BN) powder, with h-BN or c-BN as the primary phase, low residual oxygen and carbon content, and a large specific surface area; and also relates to a technology for producing superhard, mechanically durable, wear-resistant, thermal shock-resistant, and oxidation-resistant BN ceramics. The BN powder is synthesized by a cryo-aerosol ion-gel method, freeze-drying, plasma activation, and nitrification in an NH3 / N2 environment. The process includes preparation of the BNOC precursor, microsphere formation, freeze-drying, pre-pyrolysis, nitrification, crystallization, purification, and surface deoxidation by plasma treatment. The obtained BN powder has a purity of 98÷99.9% by weight, oxygen content less than 1.0%, residual carbon less than 0.5%, particle size from 0.2÷5 µm or BN flakes from 20÷500 nm and specific BET surface area from 50÷300 m² / g.From this BN powder, BN ceramics are manufactured by mixing with c-BN, h-BN, or t-BN, AIN, Si3N4, SiC, B4C, TiB2, ZrB2, and sintering additives, then grinding, shaping, sintering with SPS or hot pressing, HIP treatment when necessary, and finishing. The resulting BN ceramics have a relative density of 95-99%, Vickers hardness greater than 30 GPa, fracture toughness of 4-7 MPa.m1 / 2, and high wear resistance, thermal shock resistance, and oxidation resistance. The product is suitable for use as a superhard cutting material, heat press molds, wear-resistant parts, heat-resistant insulators, heat-dissipating composites, adsorbent materials, catalysts, and technical components operating under harsh conditions.