A review on the methods of preparation of elemental boron

The review presents four main techniques of preparation of elemental boron: molten salt electrolysis, metallic reduction, hydrogen reduction, and decomposition of boron compounds. For electrolysis, the molten salt systems, boron precursors, and mechanisms are summarized. Four kinds of hydrogen reduction of boron compounds are briefly introduced. In chemical vapor deposition process, the purity, conversion rate, morphology, and deposition rate of the produced boron are major concerns. Like hydrogen reduction, decomposition of boron compounds can be used to produce the high-purity and ultra-fine boron, but high-cost and severe reaction conditions limit its applications in large scale. Metal reduction method is improved through new preparation and purification process. All in all, boron powders with high-purity, small size, and narrow size distribution are preferred in the high-tech fields. Additionally, the robust boron nanostructures and more effective and greener synthetic strategies are also anticipated. (c) 2015 Curtin University of Technology and John Wiley & Sons, Ltd.