微波-超声波喷雾热解法制备超细球形ITO粉体的研究

以InCl_3·4H_2O和SnCl_2·2H_2O为原料,水为溶剂溶解作为前驱体溶液,采用微波管式炉加热联合超声波喷雾热解法制备得到ITO粉体。实验研究了不同微波热解温度和添加柠檬酸对ITO产品的微观形貌的影响,利用TG-DSC、XRD、SEM、EDS、TEM对样品的结构特征和微观形貌进行了表征分析。研究结果表明,前驱液浓度、温度和添加剂是影响氧化铟锡(ITO)粉体形貌的关键因素。得到粒径较小、分散性好和形貌呈球形的超细粉体的最佳条件为:温度650℃,前驱体原溶液浓度0.01mol/L,柠檬酸浓度0.004mol/L,载气速率0.6L/min,加入200目滤网。     

Research on microwave drying technology in the procedure of preparation of V2O5 from ammonium polyvanadate (APV)

High-quality vanadium pentoxide powder is an important product of the vanadium industry and was usually prepared from ammonium polyvanadate (APV) using a roasting process combined with a drying pretreatment. Conventional hot air drying is usually used for the drying of APV, the heat transfer of which is from outside to inside thus limited the efficiency of the drying pretreatment. In the present paper, microwave heating was applied as an alternative heating method for the drying of APV because of its advantages including selective heating, high heating efficiency, low energy consumption, and green environmental protection. An experimental comparison between hot air drying and microwave drying is provided, and the results show that microwave drying is more energy-saving and faster. The drying characteristics of APV under the irradiation of microwave energy were investigated. The influences of factors including microwave power, material quality, and initial moisture content on microwave drying were studied. The results show that the microwave power, initial moisture content, and initial mass are positively proportional to the microwave drying efficiency of APV. Additionally, the Page model was robust in describing the kinetics of microwave drying and hot air drying of APV. This study provides fundamental knowledge on the microwave drying process and provides the trial for the industrial applications of microwave heating on the preparation of V₂O₅.     

Process optimization for treatment of methyltin mercaptide effluents using modified semi-coke

The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry was suitably modified by treating it with phosphoric acid, with a thermal activation process. The objective of the process optimization is to reduce the chemical oxygen demand （COD） and NH4＋-N in the methyltin mercaptide industrial effluent. The process variables considered for process optimization are the semi-coke dosage, adsorption time and effluent pH. The optimized process conditions are identified to be a semi-coke dosage of 80 g/L, adsorption time of 90 min and a pH value of 8.34. The ANOVA results indicate that the adsorbent dosage and pH are the significant parameters, while the adsorption time is insignificant, possibly owing to the large range of adsorption time chosen. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy and nitrogen adsorption isotherm. The average BET surface area of modified semi-coke is estimated to be 915 mE/g, with the average pore volume of 0.71 cm3/g and a average pore diameter of 3.09 nm, with micropore volume contributing to 52.36%.     

Non-isothermal microwave leaching kinetics and absorption characteristics of primary titanium-rich materials

The non-isothermal leaching kinetics of primary titanium-rich material by microwave heating was investigated, and the temperature-pressure curves of leaching system and microwave absorption characteristics of mixture solutions before and after leaching were measured. The research of non-isothermal kinetics was evaluated by the leaching rate of Fe and the total apparent velocity equation of the non-isothermal kinetics of leaching for primary titanium-rich material by microwave heating was obtained. It is shown from the temperature-pressure curves that the high temperature and high pressure of closed leaching system are favorable to the enhancement of the leaching rate of Fe. Microwave absorption characteristics of mixture solutions before and after leaching show that there are abrupt changes of microwave absorption characteristics for 15% HCl solution and the mixture solution after leaching by 20% HCl.     

Temperature rising characteristics of ammonium diurante in microwave fields

The temperature rising characteristics of ammonium diurante, triuranium octaoxide (U₃O₈), and their mixture were investigated under microwave irradiation, aiming at exploring newly theoretical foundation for advanced metallurgical methods. The temperature rising curves showed that ammonium diurante had weak capability to absorb microwave energy, while triuranium octaoxide had the very strong absorption capability. The temperature of mixture containing 20% of U₃O₈ could rise from room temperature to 1171 K within 280 s. The ability to absorb microwave energy for the mixture with different ratios increased with the increase in the amount of U₃O₈. These are in good agreement with the results of Maxwell-Garnett effective medium theory. It is feasible to calcine ammonium diurante by adding of small amounts of U₃O₈ in microwave fields.     

响应曲面法优化微波干燥白炭黑研究

基于中心组合设计的响应曲面法,研究了微波干燥温度、干燥时间和白炭黑厚度及其交互作用对白炭黑相对脱水率的影响,得到了影响因素与白炭黑相对脱水率之间的二次方数学模型,获得了微波干燥白炭黑的优化工艺条件,即干燥温度90℃,干燥时间32min,物料厚度10mm,此条件下白炭黑的相对脱水率为99.68%。所得物料经粉碎,采用行业标准和激光粒度仪进行表征测试,其加热减量为1.2%,灼烧减量为49.8%,平均粒度为11μm。     

Thermodynamics of leaching roasted jarosite residue from zinc hydrometallurgy in NH4Cl system

The thermal decomposition process of jarosite residue and the solubility of various oxides presented in the decomposed residue in NH₄Cl-H₂O system were studied. The results of heat decomposition of jarosite residue show that the insoluble ZnFe₂O₄ phase in the residue can be decomposed at temperatures ranging from 500 °C to 650 °C for 1 h. The OLI Systems software was used to study the thermodynamics of the solubility of various metal oxides existing in the decomposed residue in NH₄Cl-H₂O system. The results show that the solubility of ZnO, PbO, CdO, CuO and Ag₂O is high, while the solubility of Fe₂O₃ is less than 10^?4 mol/L in the pH range from 4.0 to 9.0. The calculated data are in accordance with the experimental results.     

氧化锌烟尘脱氯技术研究进展

目前氧化锌烟尘已发展成为锌冶炼企业的重要原料,其氯含量直接影响着生产能耗和产品质量等。本文综述了氧化锌烟尘的来源以及氯对锌电积的影响,并从预处理脱氯和溶液脱氯等两个方面,介绍了具体的多膛炉焙烧、碱洗和离子交换等多种脱氯方法,在分析和总结各自方法优缺点的基础上,结合微波冶金的特点,提出了微波焙烧脱氯新工艺,并对新工艺的发展提出了建议。     

氢氧化锆非等温热分解动力学研究

利用TG-DTG-DSC技术研究了氢氧化锆非等温热分解过程,应用模型法和非模型法对热分解过程进行了动力学分析,建立了动力学函数,得到了氢氧化锆热分解反应机理。氢氧化锆在氮气中热分解的活化能E=71.26 kJ/mol,指前因子lgA=18.20,机理函数积分式g(α)=[-ln(1-α)]4,微分式f(α)=(1-α)[-ln(1-α)]-3/4,反应机理为随机成核和随后生长。     

Single step synthesis of indium tin oxide by ultrasonic spray and microwave assisted pyrolysis

Ultrafine indium tin oxide (ITO) powders were successfully synthesised by the combined methods of ultrasonic spray and microwave assisted pyrolysis, which is a single step, facile, rapid and continuous method without post-heating treatment. Crystallinity, morphology and microstructure of the samples were investigated by X-ray diffractometer, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscope, selected area electron diffraction pattern and laser grain size analyser. Results indicate that pure solid solution ITO ultrafine powders with homogeneous and narrow size distribution, highly dense and smooth surface morphology can be obtained under optimum conditions. Each uniform spherical particle consisted of many smaller crystallites with diameter of <10 nm.