Production of B4C-TiB2 composite powder by self-propagating high-temperature synthesis

Abstract

Advanced ceramics find significant application areas due to their superior mechanical, electrical, magnetic chemical and thermal properties. By combining these materials, significant properties can be obtained as a result of production of the composites of hard metal compounds in nanoscale dimensions. Self-propagated high-temperature synthesis (SHS) is one of the prominent methods for the production of such nanoparticles. SHS is a combustion synthesis method. In this study, nanocomposite powders of B₄C-TiB₂ were synthesized by SHS method. FactSage software was used for thermochemical simulation and computational stoichiometric optimization. In the experimental step, 2 different SHS sets were prepared. In the first stage, B₄C and TiB₂ powders were synthesized. The B₄C-TiB₂ composite was produced in the final set of experiments. Then, production parameters of B₄C-TiB₂ composite powders, from B₂O₃, TiO₂, and carbon black, were investigated. Magnesium powder was used as reductant agent. Afterwards, HCl leaching process was performed, and acid concentration was optimized. The effect of carbonic acid and H₂O₂ addition on dissolution of undesired phases was also been investigated as a new method. Products were characterized by XRD, SEM and BET analysis. B₄C-TiB₂ composite powder with quite high surface area, fine particle size and high porosity could be synthesized with reasonable purity. According to the results, the optimum molar ratios were determined as TiO₂:B₂O₃:Mg:C = 1:3:12:1.6. Optimum acid concentration was found to be 10.5 M for leaching process, and carbonic acid addition on leaching step found to be effective on TiO₂ removal. The highest purity could be obtained with 50%-50% stoichiometry. It has also been determined that the synthesis of B₄C-TiB₂ composite powder has a positive effect on both the chemical content and the morphology that will increase the sintering ability.