Carbothermic Reduction of Amorphous Silica Refined from Diatomaceous Earth

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Vol. 41; no. 2; pp. 350 - 358
• Main Authors: Hakamada, Masataka, Fukunaka, Yasuhiro, Oishi, Toshio, Nishiyama, Takashi, Kusuda, Hiromu
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.04.2010; Springer; Springer Nature B.V
• Subjects: Applied sciences; Carbothermic reactions; Characterization and Evaluation of Materials; Chemistry and Materials Science; Diatomaceous earth; Exact sciences and technology; Heating; Materials processing; Materials Science; Melting; Melts; Metallic Materials; Metallurgy; Metals. Metallurgy; Nanotechnology; Process metallurgy; Production of metals; Quartz; Reduction; Silica; Silicon; Silicon carbide; Silicon dioxide; Structural Materials; Surfaces and Interfaces; Temperature; Thin Films; Amorphous Silica; Diatomaceous Earth; Heated Sample; SiO2; Carbothermic Reduction; Carbothermy; Silica
• ISSN: 1073-5615; 1543-1916; 1543-1916
• DOI: 10.1007/s11663-009-9332-1

Aimed at developing solar-grade Si (SOG-Si) resources, amorphous silica (AS) refined from diatomaceous earth was reduced carbothermically. The reactivity of quartz—typically crystalline silica—also was investigated for comparison. Preliminary experiments confirmed an intermediate phase of SiC during the carbothermic reaction. SiC was produced more easily by heating AS mixed with graphite within 2 hours at 1773 K in a resistance furnace, whereas quartz remained unreacted under the same condition. The AS mixed with SiC then was heated in an electrode impulse furnace. An Si peak was identified in the X-ray diffraction (XRD) pattern of the sample reacted within 30 seconds at 2273 K. Chemical analysis indicated that the mole ratio of reduced Si to initial SiO 2 increased with a heating time of 15–30 seconds. It almost reached a constant depending on the heating temperature. The initial stage may correspond to a significant reduction from SiO 2 to Si in the solid–solid or solid–gas reaction systems. The next stage probably is a slow vaporization of SiO(g). Once the reduced Si melts with SiO 2 at the high temperature, the melt partially covers the surface of SiO 2 to prevent contact with SiC. A better reactivity for refined AS is observed than for quartz.