Preparation of Silicon Carbide Powder from Amorphous Silica and Investigation of Synthesis Mechanism

Abstract

An innovative process for preparing silicon carbide (SiC) from acid leaching residue of ferronickel slag through a carbon–thermal reduction process was proposed in this study. The results indicate that the acid leaching residue is an ideal silicon source for SiC preparation according to its high amorphous silica content of 84.20% and fine particle size of d50 = 29.16 μm. Compared with carbon black, activated carbon, and graphite, coke is the more appropriate carbon source for SiC preparation. A micron-size SiC powder with grade of 88.90% and an average particle size (d50) of 44.68 μm can be obtained under the following conditions: the mass ratio of coke to leaching residue as 1.2:1, in an air atmosphere, reducing at 1600 °C for 3 h, following by decarbonizing at 700 °C for 4 h. The XRD, SEM and FTIR analyses show that the prepared powder is 3C-SiC and belongs to the β-SiC crystal type. Based on thermodynamic analysis and micromorphology observation, it can be concluded that with amorphous silica as the silicon source, the carbon–thermal synthesis of SiC powder follows both the solid–solid reaction mechanism and the gas–solid mechanism. The SiC created through solid–solid reaction is primarily nucleated in situ on amorphous SiO2, with a size close to that of the original acid-leaching slag, while the SiC generated according to the gas–solid mechanism mainly nucleates heterogeneously on the surface of carbon particles, resulting in a smaller particle size and mostly adhering to the surface of solid–solid nucleated SiC particles. This study provides a feasible method for the effective utilization of amorphous silica, which is also significant for the efficient consumption of the vast acid leaching residue.

Synergistic Activation of Electric Furnace Ferronickel Slag by Mechanical Grinding and Chemical Activators to Prepare Cementitious Composites

“…The slag contains various minerals, such as olivine, tenacious pyroxene, magnesium peridotite, turbidite, and amorphous minerals [ 8 ]. Proper treatment of slag is crucial for sustainable ferronickel smelting given the substantial unit slag emission during the process, which amounts to 12–14 tons, and China’s annual production of ferronickel slag exceeding 30 million tons [ 9 , 10 , 11 , 12 , 13 , 14 ]. The cement industry is currently facing the challenge of reducing energy consumption and greenhouse gas emissions.…”