The effect of thermal shock-based heat-treatment on the cost-effective and low-temperature synthesis of needle-like r-BN

Abstract

While a variety of techniques have been applied to prepare h-BN powders of different morphology, only a few r-BN synthesis methods are presented. In this study, the h-BN structures have been synthesized through controlled nitridation at temperatures lower than 950 ℃. First, a precursor was prepared at 65 ℃ from boric acid and urea, making huge bubbles of B-N-C and flattened at higher temperatures. However, r-BN hollow needle-shaped structures were formed from these h-BN nanosheets by thermal shock-based heat treatment, where the flattening process stopped and sheets rolled. The as-synthesized samples were analyzed by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), simultaneous thermal analysis (STA: thermogravimetric (TGA), and differential thermal analysis (DTA)), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) techniques. The h-BN nanosheets are about 500 nm thick, while needle-type structures are approximately 0.88–17 µm long. The specific surface area of mesoporous nanosheets and needle-like hollow r-BN mesoporous structures is 358 and 75 m2/g, respectively. In this research, h-BN and r-BN are synthesized in sheet-like and needle-like morphologies, respectively.