Study on the microstructure and distribution of impurity phases in metallurgical grade silicon

Abstract:

The compositions and contents of precipitates in metallurgical grade silicon (MG-Si) directly affect the activity and selectivity of silicone monomer synthesis. Therefore, it is particularly significant to investigate the relationship between impurity content and precipitates correspondence in MG-Si. In this study, the microstructures and distributions of precipitates in MG-Si before and after refining are investigated by using scanning electron microscope (SEM) and energy dispersive X-Ray spectroscopy (EDX). It is found that due to the high content of Ca and Al contents in MG-Si before refining, its impurity phases are mainly Si2Al2Ca, Si-Al-Ca, Si8Al6Fe4Ca etc., but after refining, Fe is the main element in MG-Si, so its phases mainly include FeSi2(Al), FeSi2Ti, Si8Al6Fe4Ca, etc. In addition, the statistics conducted by Image Pro Plus show that the Si2Al2Ca and Si8Al6Fe4Ca phases account for respectively 48% and 30% of the precipitates composition before refining, while the FeSi2(Al) phase accounts for 68% after refining, and the only Ca-containing phase (Si8Al6Fe4Ca) accounts for 7% of the precipitates content. Here we compare the compositions and proportions of precipitates in MG-Si before and after refining, in order to explore the law of impurity content on precipitated phases, so as to prepare the best downstream MG-Si raw material for silicones.

Key words:Metallurgical grade silicon; Microstructure; Precipitates; DMDCS