Synthesis of cubic boron nitride at reduced pressures in the presence of Co[(NH_3)_6]Cl_3

摘要

Crystallization of cubic boron nitride (cBN) was studied by subjecting hexagonal boron nitride (KBN) to high P-T conditions in the presence of a well known catalyst namely Li3N and an ammonia containing solid compound such as hexaamine cobalt (III) chloride and ammonium fluoride. These solid compounds are known to decompose at high temperatures liberating ammonia, which is used in its supercritical state for cBN crystallization at reduced pressures. It was found that using these ammonia containing solid compounds in addition to the normal catalysts (Li_3N, Mg_3N_2, etc.), cBN can be synthesized at pressures as low as 30 kb as compared to 60 kb required in dry conditions without using these ammonia containing solid compounds and this process seems to be very promising for synthesizing cBN at reduced pressures.