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Kinetic study on bastnaesite concentrate mechanochemical decomposition in NaOH solution

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Journal of Rare Earths 2020年第4期38卷 418-426页

作者： Jiang Liu Zhihe Dou Ting’an Zhang Key Laboratory of Ecological Metallurgy of Multi-Metal Intergrown Ores of Ministry of Education School of MetallurgyNortheastern UniversityShenyang 110819China

mechanochemical reaction involves simultaneous chemical reaction and particle crushing;the latter increases the effective reaction area and improves the reactivity,thus enhancing its *** classical shrinking core model was used to model the kinetics of bastnaesite mechanochemical decomposition in NaOH solution,which shows a questionable *** reaction is a dynamic process,where the particle shape and concentration in reaction interface undergo constant ***,a physically consistent model was applied to describe the *** variations in OH^-concentration and particle shape were considered in the revision of *** the variation in OH^-concentration in solution with time,the model with varying OH^-concentration agrees better with the experimental data,improving the regression coefficients to between 0.936 and *** introducing fractal geometry to deal with the irregular system,the model was further optimized,and the regression coefficients increase to between 0.940 and *** these models considere shrinking particle approaches and controlling mechanisms for the diffusion and chemical ***,the fractal model with varying OH^-concentration was selected to describe the mechanochemical decomposition of bastnaesite,which indicates that the process is controlled by chemical reaction.

关键词： Bastnaesite concentrate mechanochemical decomposition Sodium hydroxide Kinetics Rare earths

Difference of Mullite Whiskers between Ytterbia-Doped Aluminum Hydroxide-Silica Gel and mechanochemical Process

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Journal of Rare Earths 2006年第Z2期24卷 51-53页

作者：梁龙李建保林红郭钢锋何明生 State Key Laboratory of New Ceramics and Fine Processing Department of Materials Science and EngineeringTsinghua University

A number of processing routes were developed for the synthesis of mullite whiskers. Mullite whiskers that were derived from ytterbia-doped aluminum hydroxide-silica gel were studied; another process for preparing mullite whiskers from Al2O3-SiO2 oxide mixtures by mechanochemical method was encountered by chance. The method of ytterbia-doped aluminum hydroxide-silica was used to enhance mullite formation from gel. For adding ytterbia, mullite formation can take place at 1000℃and almost single-phase mullite can be achieved at 1150℃, which is a significantly lower temperature than mechanochemical method. This enhancement of mullite formation is also attributed to refinement of aluminum hydroxide-silica by gel. Furthermore, well-developed single-crystal mullite whiskers were produced from the gel powder instead of normal-shaped grains. The presence of YbO might have promoted the formation of nanosized Al2O3 particles, which then acted as a template leading to mullite whiskers at higher sintering temperature.

关键词： mullite whiskers ytterbia-doped gel mechanochemical rare earths

Preparation of Compound Ultrafine CeO2 by Wet-Solid-Phase mechanochemical Modification

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Journal of Rare Earths 2004年第Z1期22卷 42-45页

作者： Gu Ziyin Chen Weifan（China National Special Superfine Powder Engineering Research Center, Nanjing University of Science & Technology, Nanjing 10094, China） Hu Pinggui Li Yongxiu Engineering Research Center for Rare Earth Nanchang UniversityNanchang 330047 China 　　 Engineering Research Center for Rare Earth Nanchang UniversityNanchang 330047 China Engineering Research Center for Rare Earth Nanchang UniversityNanchang 330047 China

To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium carbonate as raw material was *** effect of modifier reaction percentage, reaction time, calcining temperature and modifier amount on particle size, density, suspensibility, and hardness of compound CeO2 powder was *** phase evolutions of preparation process were characterized by *** micrograph of the final product shows that compound CeO2 powders obtained are well-dispersed, spherically-shaped, uniformly-sized and submicron-sized *** method is readily available in raw material, low in cost, simple in process, and has great potential for *** compound CeO2 powders of different physical properties can be synthesized by controlling the above-mentioned influence factors in preparation process.

关键词： ultrafine compound CeO2 powder mechanochemical modification preparation rare earths

Application of mechanochemical synthesis of advanced materials

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Journal of Advanced Ceramics 2012年第2期1卷 130-137页

作者： Hao WU Qiang LI Department of Chemistry East China Normal UniversityShanghai 200062China

An overview is given of recent development of mechanochemical processes for the preparation of advanced *** fundamental mechanical effects are firstly compared and *** important application fields are listed as follow... 详细信息

关键词： mechanochemical advanced materials composite materials nano scale

Facile mechanochemical Green Fabrication of CuBr(tu)3 Nanowires as Electrochemical Supercapacitor Electrodes

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Chinese Journal of Structural Chemistry 2018年第7期37卷 1155-1159页

作者：朱梅花巫学敏牛百通郭迪郭鸿旭 College of Chemistry & Environmental Minnan Normal University

CuBr（tu）3 nanowires（tu： thiourea） was prepared by a facile mechanochemical green method for the first time and their application as electrode for supercapacitors is also studied. The as-prepared CuBr（tu）3 nanowires show length of around 4 μm and width of 50~60 nm. Those nanowires exhibited high specific capacitance of 1408 F·g^（-1） at a scan rate of 5 mV·s^（-1） and 1683 F·g^（-1） at current density of 10 A·g^（-1） in a 2M KOH electrolyte. This study provides a simple, efficient, and environmental strategy to fabricate novel nanoscale electrode materials constructing metal-organic frameworks.

关键词： CuBr(tu)3 nanowires supercapacitor mechanochemical

Promoting effect of FeOx addition on the mechanochemically prepared vanadium-based catalyst for real PCDD/Fs removal and mechanism insight

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Journal of Environmental Sciences 2024年第3期137卷 478-487页

作者： Minghui Tang Ling Wang Hongxian Li Xinlei Huang Cuicui Du Shengyong Lu State Key Laboratory for Clean Energy Utilization Institute for Thermal Power EngineeringZhejiang UniversityHangzhou 310027China

Industrial-use VOx-based catalysts usually have a higher active temperature window (>250-300℃),which becomes a“bottleneck”for the practical application of PCDD/Fs catalytic degradation *** this work,VO_(x)-FeO_(x)/TiO_(2) catalyst prepared via mechanochemically method was investigated for the catalytic removal of PCDD/*** removal efficiency of 1,2-DCBz,pure PCDD/Fs gas generated in the lab,PCDD/Fs from actual fue gas,long-term were studied,and the degradation mechanism was explored using FTIR and *** degradation efficiency of 1,2-DCBz and PCDD/Fs on VO_(x)-FeO_(x)/TiO_(2) were higher than that of VO_(x)/TiO_(2)catalyst,and the optimal FeOx addition ratio was 3 wt.%.The characterization results show that the addition of FeOx can effectively improve the pore structure,surface acidity,and VOx dispersion of the catalyst,thus contributing to increasing the V^(5+)content and surface-active oxygen,which is conducive to the improvement of adsorption and redox performance of the *** the actual MSWI (municipal solid waste incineration)fue gas,the PCDD/Fs removal efficiency over VTi-3Fe-MC maintained long-term stability,higher than 85%for 240 *** result was not significantly reduced compared with the data obtained in the *** to the analysis results of intermediate products by FTIR and GC-TOFMS,it can be inferred that the epoxidation fracture of benzene ring is the rate-limiting step of dioxin catalytic degradation *** work gives an in-depth view into the PCDD/Fs removal over VO_(x)-FeO_(x)/TiO_(2) catalysts and could provide guidelines for the rational design of reliable catalysts for industrial applications.

关键词： PCDD/F removal MSWI fue gas VO_(x)-FeO_(x)/TiO_(2) mechanochemical GC-TOFMS

mechanochemical Synthesis of Nano Calcium Silicate Particles at Room Temperature

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New Journal of Glass and Ceramics 2011年第2期1卷 49-52页

作者： Shiv Prakash Singh Basudeb Karmakar Glass Science and Technology Section Glass DivisionCentral Glass and Ceramic Research Institute (CSIR India) 196 Raja S.C. Mullick Road Kolkata 700032 India

Nano-sized calcium silicate powders were synthesized at room temperature by the new mechanochemical method using a high energy planetary ball mill. The formation of calcium silicate from its raw materials (calcium carbonate and dehydrated silica gel) was monitored by the XRD analysis with progression of ball milling. It is observed that the synthetic process comes to an end through the following three sequential stages: comminution of raw materials, recombination of comminuted raw materials to final product, and comminution of final product to smaller sizes. The nanostructure of the synthesized powder was realized by the FESEM photomicrograph, TEM image and XRD analyses. These analytical observations have revealed that the nano-sized polycrystalline calcium silicate particles are formed after about 6 h of ball milling and they are spheroidal in shape. The average particle size of the as-generated calcium silicate nanocrystalline powders is found to be around 21 nm which decreases with increasing ball milling but increases with annealing at elevated temperature.

关键词： mechanochemical Processing Calcium Silicate Nanoparticle XRD FESEM TEM

Low Temperature Chlorination of Nd2O3by mechanochemical Method with CCl4

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Materials Sciences and Applications 2013年第7期4卷 419-431页

作者： Takayuki Nagai Shin-Ichi Kitawaki Nobuaki Sato Institute of Multidisciplinary Research for Advanced Materials Tohoku University Sendai Japan Nuclear Fuel Cycle Engineering Laboratories Japan Atomic Energy Agency Naka Japan Nuclear Fuel Cycle Engineering Laboratories Japan Atomic Energy Agency Naka Japan Institute of Multidisciplinary Research for Advanced Materials Tohoku University Sendai Japan

For a chlorinating method at low temperature, the possibility of chlorination of Nd2O3 by a mechanochemical reaction with CCl4 was studied using a planetary ball mill. The mechanochemical experiments were conducted by changing the pot materials, milling time, molar ratio of CCl4/Nd2O3, and revolution speed. As the results of obtained products by X-ray diffractometry and Raman spectroscopy, it was confirmed that the chlorination to NdOCl from Nd2O3 with CCl4 was advanced at room temperature in a zirconia or tungsten pot with balls. We found that an extension of the milling time and an increase of the number of ball were effective to the chlorination to NdOCl and that tensile stress remained in the milled powder by using a planetary ball mill.

关键词： mechanochemical Method Carbon Tetrachloride Neodymium Oxide Low Temperature Chlorination Neodymium Oxychloride XRD RAMAN Spectroscopy

The hydration behavior of calcium phosphates via the mechanochemical treatment

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The hydration behavior of calcium phosphates via the mechano...