Effect of calcium carbonate addition on carbothermic formation of hexagonal boron nitride

Effect of CaCO3 on formation of hexagonal boron nitride (h-BN) was investigated by holding CaCO3 free and CaCO3 added activated carbon–boric oxide mixtures under nitrogen atmosphere at 1500 °C for 30–120 min. Amount of CaCO3 addition was varied in the range of 0–50 wt.% of the initial mixture. Products were characterized by powder X-ray diffractometry, FT-IR analysis, quantitative chemical analysis, scanning electron microscopy and BET specific surface area analysis. It was observed that calcium carbonate addition led to an increase in the amount and the grain size of hexagonal boron nitride and a decrease in the amount of boron carbide forming. Ten weight percent calcium carbonate addition was found to be the optimum value for increasing the yield of hexagonal boron nitride and decreasing the formation of boron carbide.