A Carbon-Free Way for Obtaining Nanoscale Silicon

Nikolay Lyakhov,Evgeniya Devyatkina,Tatiana Grigoreva,Tatyana Udalova,Tatiana Talako,Sergey Vosmerikov

doi:10.3390/powders1010003

Abstract

The nanosized silicon powder has been produced by reduction of silica with magnesium in an argon medium using both the mechanically activated self-propagating high-temperature synthesis and the direct mechanochemical synthesis and has been investigated by X-ray phase analysis, Infrared spectroscopy, electron scanning microscopy, and energy dispersive X-ray spectroscopy. The optimal Mg:SiO2 ratio has been found to provide the minimum content of contaminant impurities of magnesium silicide and silicate in mechanically activated self-propagating high-temperature synthesis. For the first time, direct mechanochemical synthesis of Si via reduction of silica with magnesium has been implemented. Optimal component ratio and mechanical activation parameters have been determined, yielding Si/MgO composites without impurity phases (magnesium silicide and silicate). A purification procedure has been proposed for separating silicon obtained from magnesium oxide and other impurity phases. The ratio of initial components has been determined, at which purified silicon has the least amount of impurities. The particle size of silicon powder obtained was 50–80 nm for the mechanically activated self-propagating high-temperature synthesis, and 30–50 nm for the direct mechanochemical synthesis.

Highlights

Nanostructured silicon is a promising material for lithium-ion batteries [1,2], photovoltaics systems [3,4], photocatalysis [5], nanoenergetics materials [6], and thermoelectrics [7,8]
Metallurgical-grade silicon is industrially produced by carbothermal reduction of silica [9]
In systems where the combustion temperatures are significantly higher than the melting temperatures of the reactants, the preparation of powder nanosized products is a serious problem

Summary

Introduction

Nanostructured silicon is a promising material for lithium-ion batteries [1,2], photovoltaics systems [3,4], photocatalysis [5], nanoenergetics materials [6], and thermoelectrics [7,8]. Metallurgical-grade silicon is industrially produced by carbothermal reduction of silica [9]. This process cannot fabricate nanostructured material as the temperature of carbothermic reduction (over 1900 ◦ C) is higher than the melting point of silicon (1414 ◦ C). This process is multistage, energy consuming, and rather dangerous ecologically. In systems where the combustion temperatures are significantly higher than the melting temperatures of the reactants (first of all, magnesium- and aluminothermic processes), the preparation of powder nanosized products is a serious problem.

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Conclusion