Catalytic effect of potassium carbonate on carbothermic production of hexagonal boron nitride

摘要

Effect of potassium carbonate addition on the carbothermic formation of hexagonal boron nitride (hBN) was investigated by keeping the K_2CO_3 added B_2O_3+C mixtures in nitrogen atmosphere at 1400 °C for 40-160 min. K_2CO_3 amount was varied in the range of 10-60 wt% of the B_2O_3+C mixture. Products were subjected to XRD and quantitative analyses, SEM and TEM observations, and particle size measurement. Amount of hBN increased considerably with K_2CO_3 addition;;also particle size and crystallinity improved. Catalytic role of K_2CO_3 was suggested as forming a potassium borate melt in which hBN particles form, in addition to carbothermic formation reaction. Effect of K_2CO_3 on increasing the hBN amount decreased when it was used over 40%. This was attributed to the rapid evaporation of the formed potassium borate liquid.