The composition and size distribution of cutting waste were characterized. The Si-rich powders were obtained from the cutting waste using a physical sedimentation process, and then further purified by removing impurit...The composition and size distribution of cutting waste were characterized. The Si-rich powders were obtained from the cutting waste using a physical sedimentation process, and then further purified by removing impurity using acid leaching. The effects of process parameters such as acid leaching time, temperature and the ratio of solid to liquid on the purification efficiency were investigated, and the parameters were optimized. Afterwards, the high-purity Si ingot was obtained by melting the Si-rich powders in vacuum furnace. Finally, the high purity Si with 99.96%Si, 1.1×10^-6 boron （B）, and 4.0×10^-6 phosphorus （P） were obtained. The results indicate that it is feasible to extract high-purity Si, and further produce SoG-Si from the cutting slurry waste.展开更多
To realize the comprehensive utilization of coal-fired industrial solid wastes, a novel high-strength board was prepared from calcium silicate slag, fly ash, and flue gas desulfurization(FGD) gypsum. The changes in mi...To realize the comprehensive utilization of coal-fired industrial solid wastes, a novel high-strength board was prepared from calcium silicate slag, fly ash, and flue gas desulfurization(FGD) gypsum. The changes in mineral phases, chemical structure, and morphology during hydration were investigated by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), and scanning electron microscopy(SEM). A traditional board made from quartz and lime was prepared as a reference. The novel board not only consumes a lot of solid wastes, but also meets the strength requirement of the class-five calcium silicate board according to the Chinese Standard JC/T 564.2—2008. Microanalysis showed that hydrated calcium silicate gel(C-S-H(I)), ettringite, tobermorite, and xonotlite were successively generated in the novel board by synergistic hydration of the mixed solid wastes. The board strength was improved by the formation of tobermorite and xonotlite but decreased by unhydrated quartz. It was demonstrated that quartz was not completely hydrated in the traditional board. As a result, the flexural strength of the traditional board was much lower than that of the novel board.展开更多
The low yield of MXene is normally related to the delaminating step,contributing to the key technical challenges in moving toward industrial applications.Here,a shearing-force-driven strategy is proposed for re-exfoli...The low yield of MXene is normally related to the delaminating step,contributing to the key technical challenges in moving toward industrial applications.Here,a shearing-force-driven strategy is proposed for re-exfoliating waste MXene residue to prepare oxidatively stable MXene composites in a low-cost manner,where the strong shear stress in the assisted solvent,such as carbon nanotubes(CNTs),chitosan(CS),and polyacrylamide(PAM)aqueous solutions,acts on the surface of MXene(Ti_(3)C_(2)T_(x))through coordination between hydroxyl and Ti atoms,resulting in a rapid and efficient exfoliation of waste Ti_(3)C_(2)T_(x)residue under stirring.Furthermore,this formed coordinate bond helps to stabilize the low-valent Ti atoms on the surface of MXene,thereby enhancing the oxidative stability of Ti_(3)C_(2)T_(x).Besides,the CNT@MXene composite is selected to construct a free-standing membrane to encapsulate Si nanoparticles,achieving a high and reversible capacity after 50 cycles.This work supports the concept of valorizing waste and adopts a fluid shear forceassisted method to re-exfoliate waste residues,which greatly reduces the cost of processing and improves the chemical stability of MXene.More importantly,this work has uncovered a new direction for the commercialization of MXene composites and has significantly improved the realworld applications of MXene-based materials.展开更多
Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Ch...Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Chemical routes,mainly the modified Siemens process,have dominated the preparation of polycrystalline SoG-Si;however,traditional chemical techniques employ a series of complex chemical reactions involving various corrosive and hazardous reagents.In addition,large amounts of complex waste solar cells and Si kerf slurry waste gradually accumulate and are difficult to recycle using these approaches.New methods are required to meet the demand for SoGSi preparation and Si waste recycling.The metallurgical route shows promise but is hindered by the problem of eliminating B and P from metallurgical-grade Si(MG-Si).Various pyrometallurgical treatments have been proposed to enhance the removal of B and P from MG-Si.This article reviews Si refining with slag treatment,chlorination,vacuum evaporation,and solvent refining,and summarizes and discusses the basic principles and recent representative studies of the four methods.Among these,solvent refining is the most promising and environmentally friendly approach for obtaining low-cost SoG-Si and is a popular research topic.Finally,a simple and green approach,i.e.,a combination of solvent refining,slag treatment,or vacuum directional solidification,is proposed for low-cost SoG-Si preparation using MG-Si or Si wastes as raw materials.展开更多
基金Project (51074043) supported by the National Natural Science Foundation of ChinaProject (2011BAE03B01) supported by the National Technology Support Program of ChinaProject (N120409004) supported by the Fundamental Research Funds for Central Universities,China
文摘The composition and size distribution of cutting waste were characterized. The Si-rich powders were obtained from the cutting waste using a physical sedimentation process, and then further purified by removing impurity using acid leaching. The effects of process parameters such as acid leaching time, temperature and the ratio of solid to liquid on the purification efficiency were investigated, and the parameters were optimized. Afterwards, the high-purity Si ingot was obtained by melting the Si-rich powders in vacuum furnace. Finally, the high purity Si with 99.96%Si, 1.1×10^-6 boron （B）, and 4.0×10^-6 phosphorus （P） were obtained. The results indicate that it is feasible to extract high-purity Si, and further produce SoG-Si from the cutting slurry waste.
基金financial support of the National High-Tech Research and Development Program of China (No. 2012AA06A118)the Natural Science Foundation of Inner Mongolia (No. 2014MS0521)the Key Science & Technology Development Project of Baotou City (No. 2013Z1016)
文摘To realize the comprehensive utilization of coal-fired industrial solid wastes, a novel high-strength board was prepared from calcium silicate slag, fly ash, and flue gas desulfurization(FGD) gypsum. The changes in mineral phases, chemical structure, and morphology during hydration were investigated by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), and scanning electron microscopy(SEM). A traditional board made from quartz and lime was prepared as a reference. The novel board not only consumes a lot of solid wastes, but also meets the strength requirement of the class-five calcium silicate board according to the Chinese Standard JC/T 564.2—2008. Microanalysis showed that hydrated calcium silicate gel(C-S-H(I)), ettringite, tobermorite, and xonotlite were successively generated in the novel board by synergistic hydration of the mixed solid wastes. The board strength was improved by the formation of tobermorite and xonotlite but decreased by unhydrated quartz. It was demonstrated that quartz was not completely hydrated in the traditional board. As a result, the flexural strength of the traditional board was much lower than that of the novel board.
基金financially supported by the National Natural Science Foundation of China(No.52102470)the Natural Science Foundation of Jiangsu Province(No.BK20200047)+1 种基金General Project of Natural Science Research in Jiangsu Universities(22KJB15003)Scientific Research Project for Doctor Degree Teachers of Jiangsu Normal University(21XSRX003)。
文摘The low yield of MXene is normally related to the delaminating step,contributing to the key technical challenges in moving toward industrial applications.Here,a shearing-force-driven strategy is proposed for re-exfoliating waste MXene residue to prepare oxidatively stable MXene composites in a low-cost manner,where the strong shear stress in the assisted solvent,such as carbon nanotubes(CNTs),chitosan(CS),and polyacrylamide(PAM)aqueous solutions,acts on the surface of MXene(Ti_(3)C_(2)T_(x))through coordination between hydroxyl and Ti atoms,resulting in a rapid and efficient exfoliation of waste Ti_(3)C_(2)T_(x)residue under stirring.Furthermore,this formed coordinate bond helps to stabilize the low-valent Ti atoms on the surface of MXene,thereby enhancing the oxidative stability of Ti_(3)C_(2)T_(x).Besides,the CNT@MXene composite is selected to construct a free-standing membrane to encapsulate Si nanoparticles,achieving a high and reversible capacity after 50 cycles.This work supports the concept of valorizing waste and adopts a fluid shear forceassisted method to re-exfoliate waste residues,which greatly reduces the cost of processing and improves the chemical stability of MXene.More importantly,this work has uncovered a new direction for the commercialization of MXene composites and has significantly improved the realworld applications of MXene-based materials.
文摘Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Chemical routes,mainly the modified Siemens process,have dominated the preparation of polycrystalline SoG-Si;however,traditional chemical techniques employ a series of complex chemical reactions involving various corrosive and hazardous reagents.In addition,large amounts of complex waste solar cells and Si kerf slurry waste gradually accumulate and are difficult to recycle using these approaches.New methods are required to meet the demand for SoGSi preparation and Si waste recycling.The metallurgical route shows promise but is hindered by the problem of eliminating B and P from metallurgical-grade Si(MG-Si).Various pyrometallurgical treatments have been proposed to enhance the removal of B and P from MG-Si.This article reviews Si refining with slag treatment,chlorination,vacuum evaporation,and solvent refining,and summarizes and discusses the basic principles and recent representative studies of the four methods.Among these,solvent refining is the most promising and environmentally friendly approach for obtaining low-cost SoG-Si and is a popular research topic.Finally,a simple and green approach,i.e.,a combination of solvent refining,slag treatment,or vacuum directional solidification,is proposed for low-cost SoG-Si preparation using MG-Si or Si wastes as raw materials.
