Carbothermic formation of boron nitride

Formation of boron nitride by reaction of boric oxide with carbon and nitrogen was studied. It was found from the results of experiments conducted by holding B2O3-activated C mixtures under a flowing nitrogen atmosphere that formation of boron nitride was complete in 120 min at 1500 °C. After cleaning the reaction product from the ash of the activated carbon and from the unreacted B2O3 pure BN powder was obtained. B4C was found to exist as an intermediate species in the reaction products of the experiments in which BN formation was not complete. The results of experiments conducted with the objective of gaining an insight into the reaction mechanism by using different geometrical arrangements show that liquid B2O3 and solid carbon need not be in contact in the formation of BN from B2O3, C and N2 and indicate that the reaction proceeds through a gaseous boron containing species which is most probably B2O3(g).