| In recent years,photovoltaic technology based on crystalline silicon solar cells has developed rapidly,and the demand for crystalline silicon solar cells has increased year by year.In the existing diamond wire cutting process for the production of crystalline silicon battery chips,about 35%of the 6N grade high-purity silicon is waste in the form of diamond wire saw silicon powder（DWSSP）,which causes economic losses and environmental pollution.Due to the fact that DWSSP is mainly composed of 6N grade high-purity silicon and has a low content of metal impurities,effective recovery of DWSSP can reduce environmental pollution,increase production profits,and reduce the production cost of high-purity silicon.This article mainly conducts quantitative and qualitative analysis on the surface oxide layer of silicon particles in DWSSP ultrafine powder layer by layer.After determining the content of DWSSP oxide layer,the oxide layer is recycled and reused using vacuum carbothermal reduction.The specific research content is as follows:（1）Revealed the composition and structure of surface oxides on DWSSP silicon particles.Using the principle of SiO2crystal transformation,SiO2Ca O phase diagram analysis,and oxygen conservation rules,crystal form transformation experiments were conducted at temperature 1673K,and DWSSP and Ca O slagging experiments were conducted at temperature 1973K.It was determined that DWSSP has a three-layer structure,consisting of SiO2shell,middle SiOxlayer,and innermost Si particles.The SiO2,SiOx,and Si contents in five different oxygen content DWSSP were calculated using the Ca O addition amount in the DWSSP and Ca O slag making experiments.The general formulas for calculating the SiO2,SiOx,and Si contents in DWSSP were obtained through linear fitting,with SiO2=(0.90×O（T）)+0.54、SiOx=(0.16×O（T）)+27.86、Si=(-1.06×O（T）)+71.60。（2）The（35）GTof SiC reduction of SiO2reaction at atmospheric pressure was calculated using thermodynamic software,and the feasibility temperature of SiC reduction of SiO2at atmospheric pressure was verified through experiments.The reduction experiment was conducted using SiC and SiO2under atmospheric conditions at temperatures ranging from 1573K to 1973K.The results showed that under atmospheric conditions at reaction temperatures ranging from 1573K to 1973K,SiC could not reduce SiO2to Si,which is consistent with the calculation results of thermodynamic software.（3）The（35）GTof SiC reduction of SiO2under vacuum was calculated using thermodynamic software,and the feasibility of SiC reduction of SiO2under vacuum was verified through experiments at temperature and pressure.The reduction experiments of SiC and SiO2were conducted at 10-1Pa,10-2Pa,10-3Pa,and temperatures ranging from 1573K to 1973K.The results showed that SiC can reduce SiO2to Si at a vacuum of 10-3Pa and a temperature of 1973K,which is consistent with the results calculated by thermodynamic software.Based on the temperature and pressure obtained from the experimental investigation,an experiment was conducted to reduce SiO2on the surface of DWSSP silicon particles using SiC.The results showed that SiC can effectively reduce SiO2on the surface of DWSSP silicon particles to Si under a vacuum of 10-3Pa and a temperature of 1973K.This article completes the exploration of the composition and structure of the oxide layer of DWSSP,providing a theoretical basis for the recycling and material preparation of DWSSP.And using the vacuum SiC reduction method,a new solution is provided for the recovery and utilization of high-purity silicon in the DWSSP oxide layer. |
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