Synthesis of h-BN through spark plasma sintering with urea and boric acid as the starting materials

Abstract

This present work investigated the capability of the spark plasma sintering (SPS) method to synthesize h-BN powders from urea and acid boric mixture without any extra additives. Accordingly, the 1:1 M ratio of the starting materials was mixed through a simple method at the aqueous solution and then dried at a hot plate (80 °C) while it was stirred. Subsequently, the mixture was directly inserted to a graphite mold and the sintering process was performed with the constant pressure of 10 MPa and the initial vacuum condition of 19 Pa, as well as the maximum temperature of 1950 °C. Then, the obtained powders were ground and the graphite foils as the separators were removed from the sample. The prepared thin layer of the specimen was milled by the agate mortar. The characterization of the obtained powders was done without any post treatment. The XRD patterns demonstrated only h-BN peaks, as the applied high sintering temperature removed any impurities at this system according to the vacuum condition. The FESEM images of the synthesized powders demonstrated the formation of flower-like h-BN powders. Moreover, the HRTEM images of the prepared powders showed the formation of a highly crystalline h-BN.