Effect of bias application on c-BN synthesis by induction thermal plasmas under atmospheric pressure

Synthesis of c-BN was enhanced with DC bias application on the substrate in atmospheric pressure induction plasmas in this study. Previous c-BN synthesis has been performed under reduced pressure using explosive and hazardous gases. For industrial application such as coating on cutting tools, improvement of c-BN synthesis method has been strongly required. Therefore, the purpose of this paper is to investigate the mechanism of enhanced c-BN synthesis with bias application using safe starting material, h-BN and boron powder, under atmospheric pressure. The bias application leads to the optimum B/N ratio as well as the reduction of oxygen impurity in the deposits, resulting in the successful c-BN synthesis under atmospheric pressure. Important process for c-BN formation is attributed to the formation of high density of activated species such as N⁺, and the quenching process on the substrate. We conclude that bias application is important to increase activated species.