Effect Of High Pressure And Temperature On The Structure Transformation Of Boron-Rich B-C-N Compound

In this paper, B-C-N precursor was prepared by a chemical process using boric acid and melamine as starting materials. Then cubic B-C-N compound was synthesized by HPHT treatment.XRD, EDX, SEM and FTIR were used to characterize the structure, composition, morphology and chemical bonds of the samples. The results indicate: after the treatment at about 1200~1600 ℃ and 5.5 GPa, no cubic B-C-N phase is obtained from the tubostratic precursor synthesized by chemical process. With the assistance of Ca3B2N4 catalyst, cubic B-C-N is prepared at two conditions, one 5.5 GPa and higher than 1200 ℃, and the other 6 GPa and higher than 1100 ℃. Basing on the analysis above, a P-T phase diagram is obtained, which shows that hexagonal B-C-N can transform to cubic B-C-N only under 5.5 GPa or higher; while pressure elevates, the temperature synthesizing cubic B-C-N falls and the elevation of temperature (<1600 ℃) is favorable for the transformation.