【作者】 孙敏；

【导师】 刘奎仁；

【作者基本信息】 东北大学 ， 有色金属冶金， 2019， 硕士

【摘要】 面临着环境污染严重和资源短缺的双重压力,人们越来越关注对可再生能源的开发利用。近几十年,随着光伏产业的发展,对制备太阳能电池所用的晶体硅片的需求不断增大。晶体硅片在生产过程中,会有大量的硅被磨削成粉形成切割废料,不仅造成太阳能级晶体硅的浪费,而且造成环境污染。因此,切割废料的综合利用已经成为研究的热点。本论文旨在利用晶体硅切割废料作为原料,通过内热法制备碳化硅,不仅解决了切割废料中硅资源回收繁琐的难题,而且通过内热法制备出高附加值的碳化硅。这对于切割废料资源化的生态利用、高性能材料的研发和环境保护都具有重要意义。本文以晶体硅金刚线切割废料为原料,对热内法制备SiC(包括α-SiC及β-SiC)的冶炼工艺进行研究。主要研究内容如下:(1)对切割废料的物化性质进行研究。通过X射线衍射分析(XRD)、扫描电镜(SEM)、化学分析、粒度分析等分析手段对原料物相组成、微观形貌、化学组成、粒度分布等进行研究。XRD分析结果显示,晶体硅切割废料主要由Si、Si02、Fe和Fe203组成;粒度分析结果表明,切割废料粒径主要集中在0.5～10 μm,平均粒径为1μm;化学分析测得切割废料中Si的质量分数为65.69%,Si02的质量分数为23.24%,Fe的质量分数为8.56%,Fe203的质量分数为2.51%。(2)对切割废料进行酸洗除铁研究。研究了硫酸体系下浸出温度、浸出时间、硫酸浓度、液固比等对除铁率的影响,并得出最佳工艺条件:浸出温度为90℃、浸出时间为3.5 h、硫酸浓度为4 vol%、液固比为3:1。酸洗除铁后原料中的铁含量降低至0.12%,除铁率达到98.92%。(3)对以切割废料为原料采用内热法制备β-SiC粉体的工艺进行研究。研究反应温度、保温时间、硅碳比以及碳源等因素对合成产物β-SiC粉体纯度、粒度和形貌的影响;并确定较优的制备β-SiC粉体的工艺条件:反应温度为1650℃、保温时间为5 h、硅碳比为5:3、碳源为活性炭。在该条件下合成的β-SiC结构完整,结晶度好,颗粒粒径约为235 μm,纯度为97.63%,球磨韧性为53.71%,显微硬度为2750 MPa,磁性物含量为 0.054%。(4)对以切割废料为原料采用内热法制备α-SiC粉体的工艺进行研究。研究反应温度、保温时间和硅碳比等因素对合成产物α-SiC粉体纯度、粒度和形貌的影响。并确定较优的制备α-SiC粉体的工艺条件:反应温度为1950℃,保温时间为8 h,硅碳比为5:4,碳源为活性炭。在该条件下合成的α-SiC的其颗粒粒径达到495.461 μm,纯度达到98.86%,球磨韧性为75.27%,显微硬度为3125 MPa,磁性物含量为0.025%,符合工业磨料碳化硅的要求。更多还原

【Abstract】 Faced with the double pressure of serious environmental pollution and resource shortage,people are paying more and more attention to the development and utilization of renewable energy.In recent decades,with the development of the photovoltaic industry,the demand for crystalline silicon wafers for preparing solar cells has been increasing.In the production process of crystalline silicon wafers,a large amount of silicon is ground into powder to form cutting waste,which not only causes waste of solar grade crystalline silicon,but also causes environmental pollution.Therefore,the comprehensive utilization of cutting waste has become a research hotspot.This thesis aims to use silicon crystal cutting waste as raw material to prepare silicon carbide by internal heat method,which not only solves the problem of cumbersome recycling of silicon resources in cutting waste,but also produces high value-added silicon carbide by internal heat method.It is of great significance for the ecological utilization of cutting waste resources,the development of high-performance materials and environmental protection.In this paper,the smelting process of SiC(including α-SiC and β-SiC)prepared by thermal internal method was studied by using crystalline silicon diamond wire cutting waste as raw material.The main research contents are as follows:(1)Research on the physicochemical properties of cutting waste.X-ray diffraction analysis(XRD),Scanning electron microscope(SEM),chemical analysis,particle size analysis and other analytical methods were used to study the phase composition,microstructure,chemical composition and particle size distribution of the raw materials.The results of XRD analysis show that the crystalline silicon cutting waste is mainly composed of Si,SiO2 Fe and Fe2O3;The results of particle size analysis show that the particle size of the cutting waste is mainly concentrated in 0.5～10 μm and the average particle size is 1 μm.Chemical analysis showed that the mass fraction of Si in the cutting waste was 65.69%,the mass fraction of SiO2 was 23.24%,the mass fraction of Fe was 8.56%and the mass fraction of Fe2O3 was 2.51%.(2)Research on pickling and removing iron from cutting waste.The effects of leaching temperature,leaching time,liquid-solid ratio and sulfuric acid concentration on the iron removal rate were studied,and the optimum process conditions were obtained:leaching temperature was 90℃,leaching time was 3.5 h,sulfuric acid concentration was 4 vol%,the liquid to solid ratio was 3:1.The iron content in the raw material after pickling and iron removal was reduced to 0.12%,and the iron removal rate reached 98.92%.(3)The process of preparing β-SiC powder by internal heat method using cutting waste as raw material was studied.The effects of synthesis temperature,holding time,silicon-carbon ratio and carbon source on the purity,particle size and morphology of the synthesized β-SiC powder were studied.The process conditions for preparing β-SiC powder were determined:the reaction temperature was 1650℃,the holding time was 5 h,the silicon to carbon ratio was 5:3,and the carbon source was activated carbon.The β-SiC synthesized under this condition has a complete structure and good crystallinity.The particle size was about 235 μm,the purity was 97.63%,the ball milling toughness was 53.71%,the microhardness was 2750 MPa,and the magnetic content was 0.054%..(4)The process of preparing α-SiC powder by internal heat method using cutting waste as raw material was studied.The effects of synthesis temperature,holding time and silicon-carbon ratio on the purity,particle size and morphology of the synthesized α-SiC powder were studied.The process conditions for preparing α-SiC powder are determined:the reaction temperature was 1950℃,the holding time was 8 h,the silicon to carbon ratio was 5:4,and the carbon source was activated carbon.The α-SiC synthesized under this condition has a particle size of 495.461 μm,a purity of 98.86%,a ball milling toughness of 75.27%,a microhardness of 3125 MPa,and a magnetic content of 0.025%,which meets the requirements of industrial abrasive silicon carbide.更多还原