粉体的静电分级

Electrostatic Classification of Fine Powders

为了达到对粉体的精确分级,以满足制备粉体过程中越来越严格的粒度控制要求,采用静电分级的方法,即给颗粒带上静电,并使其在静电场中根据颗粒带电的不同而分级,并以此方法为基础研制了一种静电分级设备.实验测得粒径在75μm以下的铜粉的荷质比极大值为-14.8nC/g,W10,W20,W40SiC(粒径分别为10,20,40μm)粉体的荷质比的极大值分别为-90.6,-43.2,-50.7nC/g.可以明显看出铜粉的分级效果.碳化硅粉体II细粉大于25μm的累积质量分数从原料的3.77%下降到细粉的2.39%,碳化硅粉体III细粉大于25μm的累积质量分数从原料的1.80%下降到细粉的0.93%.结果表明,静电分级是一种具有发展前景的分级方法.

For obtaining precise powder classification to adapt the strict need for special size powder, a new method and apparatus which charges the particles with electrostatic charges and then put them into an electric field to make them classified in the particle sizes was presented in this work. The charging and classifying test was done on -75 gna copper powder and different sizes of SiC powder. The results show that the maximum ratio of charge to mass is -14.8 nC/g for copper powder, -90.6, -43.2, -50.7 nC/g for W10, W20 and W40 SiC powder samples respectively. The micrographs of the classified copper powder show that the high charge voltage leads to better classification result. The classification results of SiC powder are evaluated by cumulating mass fraction. The cumulating mass fraction of powder above 25 μm promoted from 3.77% to 2.39% for sample Ⅱ and from 1.80% to 0.93% for sampleⅢ . The electrostatic classification of powder is a future potential method.