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超微粒子是指颗粒尺寸大于原子簇(cluster)而小于微粉(fine powder),一般在1～100nm之间。当小粒子尺寸进入纳米量级时,显示出了普通大颗粒材料不具有的特性,即小尺寸效应、表面与界面效应、量子尺寸效应和宏观量子隧道效应。目前伴随着超微粉研究与应用,其制备新方法不断出现,概括起来分3大类:固相法、液相法和气相法。本方法是在综合各种液相法的基础上,发展的一种新的制备超微粉的技术——沉淀转化法。其理论依据是根据难溶化合物溶度积(k_(sn))的不同,通过改变沉淀转化剂的浓度、转化温度以及借助表面活性剂来控制颗粒生长和防止颗粒团聚,获得单分散超微粒子。该法具有实验设备简单,原料成本低、工艺流程短、操作方便、产率高等优点。利用该法我们已经成功的制备出了Ni(OH)_2,NiO,CuO,La(OH)_3,ZnO,Co(OH)_2和Co_3O_4等氢氧化物和氧化物超微粉。 超微粉制备过程如下:(1)氧化铜超微粉:准确称取一定量的Cu(NO_3)_2·3H_2O(A.R.)配制成溶液,与化学计量一定浓度的无水碳酸钠溶液反应,生成浅蓝色碱式碳酸铜沉淀,磁搅拌至无气泡产生,加入一定量的表面活性剂吐温-80,继续搅拌0.5h,再加入一定浓度化学计量的碳酸钠溶液,一定温度加热搅拌1h,过滤并用蒸馏水洗涤三次以上,得到黑色氧化铜超微粉末;(2)氢氧化
Ultrafine particles are particles that are larger than the cluster and smaller than the fine powder, typically between 1 and 100 nm. When the size of small particles is in the order of nanometers, it shows the characteristics that ordinary large particles do not have, namely, small size effect, surface and interface effect, quantum size effect and macroscopic quantum tunneling effect. At present, with the research and application of ultrafine powder, new methods of preparation continue to emerge, which can be summarized into three categories: solid phase method, liquid phase method and gas phase method. The method is based on the synthesis of a variety of liquid phase method, the development of a new technology for the preparation of ultrafine powder - precipitation conversion method. The theoretical basis is that the monodispersed particles are obtained by changing the concentration of the conversion agent, the conversion temperature and the surfactant to control the particle growth and prevent the particles from agglomerating according to the solubility product (k_ (sn)) of the insoluble compound. The method has the advantages of simple experimental equipment, low raw material cost, short process flow, convenient operation and high yield. Using this method, we have successfully prepared hydroxides and oxides such as Ni (OH) 2, NiO, CuO, La (OH) 3, ZnO, Co (OH) 2 and Co_3O_4. Superfine powder preparation process is as follows: (1) copper oxide superfine powder: accurately weighed a certain amount of Cu (NO_3) _2 3H_2O (AR) formulated into a solution, and a certain concentration of stoichiometric anhydrous sodium carbonate solution to produce light blue Alkali copper carbonate precipitation, magnetic stirring until no bubbles, adding a certain amount of surfactant Tween -80, stirring was continued for 0.5h, then add a certain concentration of stoichiometric sodium carbonate solution, a certain temperature heating and stirring 1h, filtered and used Washed with distilled water more than three times to obtain black copper oxide ultrafine powder; (2) hydroxide