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A new method for preparing ultrafine powders -- Precipitation transformation method

机译：一种制备超细粉的新方法-沉淀转化法

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摘要

The particle sizes of ultrafine powders are between cluster and fine powders, with the particle diameters generally in the range of 1--100 nm. When compared with common materials consisting of bigger particles, materials consisting of nanometer-size particles have many special properties. These include small-sized effect, surface and interface effect, quantum-sized effect and macro-quantum tunnel effect. The new synthesis methods are continuously emerging to meet the needs of studies and applicationsof ultrafine powders. The preparation methods can be classified into three categories: the solid state, liquid state and gaseous state methods. We have established a new liquid state method--the precipitation transformation method. Its theoretical basislies in the difference in solubility (k_(sp)) of insoluble or slightly soluble products. The precipitation transformation is completed via changing the concentration of precipitation transformation agent and transformation temperature, During the precipitation transformation, the particle growth of new-produced precipitates is controlled and the formation of hard agglomerates is avoided by adding surfactant (tween-80). And thus the monodispersed ultrafine powders can be obtained finally. This method has many advantages, i. e. the experimental apparatuses are simple, economic and easy to operate with high productivity, and the starting materials are cheap and easily obtained. We have already prepared the ultrafine powders of Ni(OH)_2, NiO, CuO, La(OH)_3, ZnO, Co(OH)_2, Co_3O_4 and so on by this method.
机译：超细粉末的粒径在簇状粉末和细粉末之间，粒径通常在1--100nm的范围内。与由较大颗粒组成的普通材料相比，由纳米尺寸颗粒组成的材料具有许多特殊性能。这些包括小尺寸效应，表面和界面效应，量子尺寸效应和宏观量子隧道效应。不断出现新的合成方法以满足超细粉的研究和应用需求。制备方法可分为三类：固态，液态和气态方法。我们建立了一种新的液态方法-沉淀转化法。其理论依据是不溶或微溶产物的溶解度差异（k_（sp））。通过改变沉淀转化剂的浓度和转变温度来完成沉淀转化。在沉淀转化期间，通过添加表面活性剂（吐温-80），可以控制新产生的沉淀物的颗粒生长，并避免了硬团​​聚物的形成。因此最终可以得到单分散的超细粉末。该方法具有许多优点，即。 e。该实验装置简单，经济，易于操作，生产率高，原料便宜且易于获得。我们已经通过这种方法制备了Ni（OH）_2，NiO，CuO，La（OH）_3，ZnO，Co（OH）_2，Co_3O_4等的超细粉末。

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