Synthesis of h‐BN composite powders via aluminothermic reduction combustion route

Abstract

Abstracth‐BN composite powders were prepared by an aluminothermic reduction combustion synthesis route using a mixture of B2O3 and Al as raw material, and MgO as diluent under low‐pressure nitrogen (.6 MPa). The phase transformation and structural evaluation during the combustion synthesis were investigated. Samples with B2O3 to Al molar ratio of 1:6 exhibited the highest diffraction peaks of h‐BN, in which the phases are h‐BN, Al2O3·7AlN, AlN, and MgAlON spinel phase. The combustion wave quenching test revealed that h‐BN is mainly formed via following routes: first, Al reacts with nitrogen; then the resulting AlN reacts with B2O3 to form h‐BN. Due to solid solution formation between Al2O3, AlN, and MgO, both MgAlON and Al2O3·7AlN were formed in the resulting samples. The composite powders obtained by aluminothermic reduction combustion synthesis in this work exhibit potential application in refractories industry for replacing graphite in carbon‐containing refractories.