Molten salt synthesis of highly ordered and nanostructured hexagonal boron nitride
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© 2019 Elsevier B.V. Hexagonal boron nitride (h-BN) is a well-known ceramic that has wide application areas ranging from electronics to metallurgy. However, highly ordered h-BN is conventionally synthesized at high temperatures above 1800 °C. In this work, we investigated the formation of BN from boric acid (H 3 BO 3 )-ammonium chloride (NH 4 Cl) mixture in the sodium chloride (NaCl)-potassium chloride (KCl) eutectic salt. We report the synthesis of highly ordered and nanostructured h-BN at 1000 °C using molten salt synthesis. The effect of starting composition, synthesis temperature, and dwell time on BN formation and its structural ordering were systematically investigated. It is concluded that the molten salt plays important roles in the formation of BN and its structural ordering, which is achieved by i) decomposing the boron (B)-nitrogen (N) bearing reactants that lead to the formation of BN layers, and ii) increasing the mobility of BN layers formed. Furthermore, we propose a possible reaction mechanism that governs the BN formation from the reactant mixture in molten salts and explain the observations based on thermodynamic and kinetic considerations.
author list (cited authors)
Örnek, M., Wang, K., Xiang, S., Hwang, C., Xie, K. Y., & Haber, R. A.