具有高振实密度的单分散和亚微米级球形银粉的合成

本文采用传统化学还原法,以硝酸银为银源,明胶为分散剂,抗坏血酸为还原剂,合成了振实密度高、单分散、球形的亚微米级银粉。系统地研究了反应物浓度,分散剂用量,溶液pH值,原料添加方式和反应温度对银颗粒特性的影响。采用扫描电子显微镜(SEM),激光粒度分析仪,X-射线衍射(XRD)和能量色散谱(EDS)对所制备银粉的特性进行了表征。SEM和激光粒度分析仪结果表明银粉呈单分散的球形,粒径范围在(0.40~1.05) μm。最优条件下制备的银粉的振实密度为4.55 g/cm³。     

Submicro-sized LiMn2O4 prepared by a sol–gel, spray-drying method

Submicro-sized LiMn₂O₄ powders were produced by a sol–gel, spray-drying method in which a brown gel precursor was prepared via the reaction of LiOH alkaline solution with 1 M Mn(CH₃COO)₂. The gel precursor was then transferred into a dry precursor powder via a spray-dry process. After heating treatment the spinel LiMn₂O₄ powder was obtained. The composition and the crystal size of the samples were strongly affected by the spray speed in the drying process and the heating temperature. The structure and the morphology of LiMn₂O₄ powder were investigated by DTA, TGA, IR, XRD and SEM methods. It was discovered that submicro-sized LiMn₂O₄ powder could be formed under the conditions of rotating spray speed of 15 000 rpm and syntheses temperature of 700 °C. The electrochemical properties of LiMn₂O₄ samples in 1 M LiPF₆, EC:DMC = 1:1 solution were tested by measuring the voltammograms and charge–discharge curves. The submicro-sized LiMn₂O₄ sample made at 700 °C has a capacity of 128 mAh g^–1 and good cycle stability for Li⁺ intercalation reaction. This method may be applied to the industrial-scale production of superfine LiMn₂O₄ powder for use in lithium ion batteries.