Research Progress of Synthesis Methods of Boron Carbide Powder

As a refractory non-metallic superhard carbide material, boron carbide (B4C) has attracted more and more attention, and the research on its preparation methods and application has became one of the hot topics. B4C not only has ultra-high hardness, but also has many excellent properties such as high melting point, high neutron absorption, chemical stability, low density and so on. It has been widely used in mechanical equipment, abrasives, and catalytic carriers. However, with the potential of B4C powder in the field of refractory antioxidants, high temperature thermocouples, protective armor, and nuclear reactor shielding materials and so on. The B4C powder obtained by the traditional preparation met-hod has uneven particle size and high impurity content, especially the coarse particles and single morphology, which can not fully exert the excellent performance of B4C, and severely limits the application of B4C powder. Compared with the traditional B4C powder, the powder with high purity, low dimension and uniform particle size can effectively improve the sintering performance and fracture toughness of B4C materials. Therefore, it is more meaningful to prepare B4C powders with high purity, uniform size, small particle size, and high aspect ratio. However, it is difficult to synthesize B4C powders because B4C is composed of more than 90% covalent bonds and the kinetic and thermodynamic conditions of the synthesis process are complicated. Especially, it is difficult to synthesize B4C powders with high performance and wide application fields by low cost and simple process requirements. Therefore, more and more researchers have improved the synthesis method in various ways to obtain B4C powder with excellent performance, thereby improving the sintering properties of B4C powder and improving fracture toughness, so as to meet more and more application fields and more demanding application environments. In recent years, many literatures reported that B4C powders with high purity, low dimension and uniform particle size can be obtained by various methods. B4C powders prepared by elemental synthesis method have small output but high purity in general. The minimum particle size of B4C obtained by the most commonly used carbothermal reduction method in the industry is 20-30 nm. The fast and energy-saving self-propagating high-temperature synthesis method can obtain a sheet-like B4C with a thickness of 10-50 nm. B4C with special morphology such as rods and fibers is mainly synthesized by chemical vapor deposition. Nano-sized B4C powders have also been obtained by some new synthetic methods such as solvothermal reduction, VLS growth, and particle beam synthesis. These latest achievements are mainly achieved by changing the types of raw materials, improving the quality of raw materials, using raw materials with different morphologies, using catalysts, and combining various methods. In addition, theoretical research on the B4C generation process has also contributed to the development of various synthetic methods. The recent progress of synthesis methods of B4C was reviewed, focusing on the development and research status of elemental synthesis, carbothermal reduction, self-propagating high-temperature synthesis, and chemical vapor deposition for the preparation of high-purity, low-dimensional B4C. Additionally, the development directions in synthesis of B4C were out looked. © 2019, Materials Review Magazine. All right reserved.