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Li X.,Kunming University of Science and Technology | Wu D.,Kunming University of Science and Technology | Wang J.,Kunming University of Science and Technology | Zhu W.,Kunming University of Science and Technology | And 6 more authors.
Microporous and Mesoporous Materials | Year: 2016

Large-sized spherical mesoporous silica (LMS > 3 mm) has been synthesized through a pseudomorphic transformation method. For this, cetyltrimethylammonium bromide (CTAB) was selected as a templating agent and commercial silica spheres were used as the parent silica material. The effects of synthesis parameters, such as NaOH:SiO2 molar ratio, reaction time, and ethanol:H2O volume ratio, have been quantitatively investigated. The structure and morphology of the spheres have been investigated by N2 sorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The pore structure of LMS obtained from a molar ratio of 140H2O:0.1NaOH:0.27CTAB after 48 h was examined with the addition of ethanol, and the optimal volume ratio of ethanol:H2O was identified as 0.252. Under the optimum conditions, high-quality mesoporous silica spheres were synthesized with a high specific surface area (about 1078.19 m2/g) after post-hydrothermal treatment. The ordered pore structure was maintained over four cycles in recyclability experiments on the reaction solution. The large-sized particles showed improved capacity for Pb2+ removal, suggesting that they might be applied as a basic material for heavy metal adsorption in treating industrial or natural waste water. © 2016 Elsevier Inc. All rights reserved. Source


Luo T.,Kunming University of Science and Technology | Luo T.,Engineering Research Center for Silicon Metallurgy and Silicon Materials of Yunnan Provincial Universities | Lv G.,Kunming University of Science and Technology | Lv G.,Engineering Research Center for Silicon Metallurgy and Silicon Materials of Yunnan Provincial Universities | And 8 more authors.
Journal of Crystal Growth | Year: 2013

A transient global simulation was carried out to investigate the effect of pulling-down rate on the temperature distribution, melt convection and melt/crystal (m-c) interface in vacuum directional solidification purification process for SoG-Si in metallurgical route. Simulation results show that pulling-down rate has little effect on flow behavior of melt. The isotherms change in the bottom area of silicon for 10 μm/s pulling-down rate is larger than that of 5 μm/s, and it may lead to higher thermal tress in this part of the silicon ingot. The m-c interface is less convex to the crystal and its variation is smaller for 10 μm/s, it further contributes to desirable crystal growth. We found that silicon ingots produced by vacuum directional solidification purification with pulling-down rate of 10 μm/s can meet the crystal morphology requirement of solar grade silicon (SoG-Si). So we proposed a new route for metallurgical production of solar wafers which combining with removal of impurities and ingot casting process into a process. Preparation of multi-crystalline silicon (mc-Si) by the directional solidification process will have large-size columnar grain growth and produce the solar wafers with appropriate technological parameters for directional solidification process. © 2013 Elsevier B.V. Source


Ma W.,Kunming University of Science and Technology | Ma W.,Engineering Research Center for Silicon Metallurgy and Silicon Materials of Yunnan Provincial Universities | Yang X.,Kunming University of Science and Technology | Yang X.,Engineering Research Center for Silicon Metallurgy and Silicon Materials of Yunnan Provincial Universities | And 2 more authors.
TMS Annual Meeting | Year: 2015

Cast multicrystalline silicon ingots are widely used in photovoltaic manufacturing. A key issue to achieve high solar cell efficiencies is to attain an optimized temperature field during directional solidification (DS) process. This paper reports numerical investigation of multicrystalline silicon (mc-Si) ingot production using two major types of DS furnace. Specific examination is made on thermal distribution, interface shape and stress field. Evaluation is performed for the applicability of thermal system design to reduce thermal stress, improve crystal quality and enhance energy efficiency. The effects of procedure parameters and geometric configuration on temperature distribution are discussed as well to provide the viable solutions for systems optimization. Copyright © 2015 by The Minerals, Metals & Materials Society. All rights reserved. Source


Yang X.-W.,Kunming University of Science and Technology | Yang X.-W.,State Key Laboratory Complex Nonferrous Metal Resour Cleaning Utilization Yunnan Province | Ma W.-H.,Kunming University of Science and Technology | Ma W.-H.,State Key Laboratory Complex Nonferrous Metal Resour Cleaning Utilization Yunnan Province | And 8 more authors.
Guocheng Gongcheng Xuebao/The Chinese Journal of Process Engineering | Year: 2016

Bio-char reductant was prepared with walnut shells, and characterized to analyze the relationship between chemical components, functional group distribution and resistivity. The results showed that resistivity of bio-char declined from 6288.7 to 1515.9 μΩ·m with increasing of pyrolysis temperature from 400℃ to 1450℃. Fixed carbon content increased and volatile matter content declined with increasing of pyrolysis temperature. Carbonyl and aliphatic functional groups in the char were gradually decomposed, the interlamellar spacing of d002 on the lattice plane decreased gradually, its crystallinity, aromatization and carbon structure ordering degree increased with increasing of pyrolysis temperature. In the pyrolysis temperature range of 500~700℃, high-performance bio-char reductant with high yield (≥24%), high resistivity (≥5800 μΩ·m), high fixed carbon content (≥80%) and low ash content (≤4%) was obtained. The char had developed pores, and could be used as the reductant for industrial silicon production. © 2016, Science Press. All right reserved. Source


Li X.,Kunming University of Science and Technology | Han C.,Kunming University of Science and Technology | Zhu W.,Kunming University of Science and Technology | Ma W.,Kunming University of Science and Technology | And 8 more authors.
Journal of Chemistry | Year: 2014

Amino-functionalized mesoporous silica MCM-41 materials have been prepared to develop efficient adsorbents of Cr(VI) in wastewater, using silica fume as silica source. Functionalization with amino groups has been carried out by using grafting method. The materials have been characterized by means of X-ray diffraction (XRD), nitrogen (N adsorption-desorption, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Adsorption potential of the material for Cr(VI) removal from aqueous solution was investigated by varying experimental conditions such as pH, initial metal concentration, and contact time. The equilibrium data were analyzed using the Langmuir and Freundlich isotherm by linear regression analysis, and the results show that the adsorption equilibrium data obeyed the Langmuir model. In addition, the kinetics analysis revealed that the overall adsorption process was successfully fitted with the pseudo-second-order kinetic model. © 2014 Xitong Li et al. Source

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