Investigation on preparing boron nitride by nitriding pure boron at 1200-1550

Boron nitride(BN) was prepared by nitriding pure boron(B) deposited on carbon substrates by chemical vapor deposition(CVD).Thermodynamic analysis of preparing BN by nitriding CVD B at 1200-1550℃ was firstly performed.And then,the effects of nitridation conditions,including temperature,nitridation atmosphere and CVD B microstructure,on the conversion of B to BN were analyzed by scanning electron microscopy(SEM),energy dispersion spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).Results show that the conversion degree of B to BN firstly increased and then slightly decreased with rising temperature.The nitridation degree was controlled by mutual actions between the nitridation of B and consumption of the effective nitrogen source(NH3).The morphology of products and the reaction mechanism between B and N were influenced by nitridation temperature.At high temperatures(1400-1500℃),BN with highly ordered microstructure was produced.On using N2-H2 as nitridation atmosphere instead of NH3-H2-N2,no BN was obtained in the studied temperature range.The microstructure and component of BN obtained in nitridation process were little affected by the microstructure of CVD B.