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Kinetics of antimony production via carbothermal reduction of Sb2O3–carbon powder–NaCl mixture using microwave and conventional heating was investigated to identify the dominant controlling mechanism. Results of conventional heating revealed the temperature range of conventional carbothermal reduction reaction is 500°C to 800°C, with the average activation energy of each stage being 81.97 kJ/mol (α = 0.1–0.5), 65.17 kJ/mol (α = 0.5–0.75), and 69.86 kJ/mol (α = 0.75–1.0), respectively. In the microwave field, the carbothermal reduction reaction of raw materials can be completed at 600°C to obtain antimony, and the weight loss data of the carbothermal reduction process were recorded for the first time. The above results show that the microwave field enhanced the interfacial chemical effect, accelerated the interfacial diffusion from the metal phase to the oxide phase, and reduced the activation energy of the carbon thermal reduction process to 6.85 kJ/mol. The growth index of antimony grain growth process is estimated to be 4.33, controlled by the surface diffusion. These data provide a reliable theoretical basis for studying the reduction reactions of minerals in microwave fields. [ABSTRACT FROM AUTHOR]

In this work, a clean microwave carbothermal reduction of Sb2O3 mineral to prepare metallic antimony ingot is proposed. Response surface methodology was used to optimize condition for microwave carbothermal reduction of Sb2O3. The roasting temperature, roasting duration, carbon powder ratio and NaCl addition ratio was collected to carry out a four-factor and three-level experiment. In the optimized conditions, a >77.0% yield of antimony ingot can be obtained under roasting temperature of 730 °C, roasting time of 60min, carbon powder ratio of 0.3, NaCl addition amount of 4%. More than 99% Sb content of metallic Sb ingot is obtained in the microwave field. The mechanism of microwave carbothermal reduction of Sb2O3 was investigated by XRD, SEM-EDS and Mapping analysis, the results show that the microwave reduction process is divided into three stages based on the melting point of antimony, namely, 25 °C–400 °C, 400 °C–630 °C, and above 630 °C, which differ in terms of phase transformation. In the microwave field, the reduction of Sb2O3 to Sb particles can be completed within 15 min. Microwave metallurgical technology is conducive to the sustainable development of antimony metallurgy, and also provides a clean technology for the metallurgy industry.

β-Sialon powders were synthesized by microwave-assisted carbothermal reduction of powder materials resultant from a sol–gel process using Si(OC 2 H 5 ) 4 , Al(NO 3 ) 3 ·9H 2 O and sucrose (C 12 H 22 O 11 ) as the main starting materials and artificial neural networks (ANNs) was applied to model and predict relative contents of β-Sialon in the final product samples. β-Sialon was formed at as low as 1250 °C by using the technique developed with the present work. Furthermore, addition of Fe 2 O 3 promoted the β-Sialon formation. As-prepared β-Sialon ultrafine powders were granular with primary size of about 69 nm. A back propagation (BP) ANNs was used to establish a model to predict the reaction extents (relative contents of β-Sialon) under various processing conditions. The results indicated that the BP ANNs could be effectively used to establish the nonlinear relationships between the relative contents of β-Sialon and the processing conditions. [ABSTRACT FROM AUTHOR]