A. A. Аkberdin, A. S. Kim, R. B. Sultangaziev.
ABSTRACT
A complete thermodynamic analysis of chemical transformations in the BaO-B2O3-C system in the temperature range 1400–3000 K was performed using the «Terra» software package. It has been established that even before the reduction process begins, the products of interaction between boron and barium oxides are barium ortho-Ba3B2O6 and barium metaborate BaB2O4 with crystallization temperatures of 1656 and 1378 K, respectively. Carbon reduction of a mixture of oxides with a high (90BaO + 10B2O3) and low (35BaO + 65B2O3) content of barium oxide was studied. It was found that in all cases the interaction products can be carbide BaC2 and barium hexaboride BaB6, as well as boron carbide B4C. When processing a mixture rich in barium oxide, barium carbide BaC2 prevails in the smelting products, while barium hexaboride prevails in the boron oxide – rich mixture. The formation of barium borates complicates the recovery process due to the reduced activity of BaO and B2O3 in them. As strong basic (BaO) and acidic (B2O3) oxides, they form strong compounds. The temperature of the beginning of barium reduction to BaC2 from BaO is 1500 K, and from Ba3B2O6 – 2200 K. Joint recovery of barium and of boron is derived from the borate of barium with the formation of BaB6. In both mixtures, the appearance of barium hexaboride in the melting products is recorded at 2300 K. The presence of BaB6 in the condensed phase indicates the possibility of producing a complex Ferroalloy that simultaneously contains boron and barium, known as effective alloying and modifying elements.
Numerical simulation of the technology uses the method of mathematical planning of the experiment. The equations of dependence of the number of formed phases on the flow rate of BaO, B2O3 and temperature are obtained. The entire range of oxide compositions was studied in accordance with the state diagram of the BaO-B2O3 system. The equations allow you to select the temperature and charge conditions of melting to obtain the required compositions of condensed phases. The results of numerical experiments obtained in this work can be applied to the production of borbarium alloys and the synthesis of high-temperature materials based on BaB6, BaC2 and B4C.
KEY WORDS:
boron, barium, alloy, modeling, phase, barium carbide, barium hexaboride, approximating equations, coefficient of determination.
DOI: 10.31857/S0235010621030026