气流粉碎/静电分散制备超微粉体失电规律研究

Investigation on the electric charge decay of micropowder prepared by jet milling/electrostatic dispersion

采用气流粉碎与静电分散复合法（气流粉碎/静电分散）制备得到的超微粉体具有较好的分散性,然而粉体颗粒所带电量在空气中会逐渐发生消散流失,导致分散效果逐渐减弱甚至消失。本文以CaCO3粉体和钡铁氧体粉体为研究对象,设计了一种新型非接触测量方案来实现荷电粒子电量衰减特性的连续测量,对两种荷电粉体颗粒在空气中的失电过程进行了实验研究。结果表明,荷电粉体颗粒荷质比在空气中的消散呈指数关系衰减;原始荷电电压越高,荷质比的初始衰减速率越大,且在整个衰减过程中相同静置时间下的荷质比数值亦越大;此外,粉体颗粒对所荷电量的贮存能力与颗粒粒径及其相对介电常数有关,颗粒粒径愈小,相对介电常数愈大,则其电荷贮存性能愈佳。

The micropowders prepared by the combination method of jet milling and electrostatic dispersion（jet milling/electrostatic dispersion,J/E） show the good dispersibility,but the electric charge carried by particles will vanish gradually in air,making the dispersion effect of particles weaken and even disappear.Using CaCO3 powder and barium ferrite powder as the raw materials,a novel non-contact method was designed to measure the electric charge decay of the charged particles in this paper,and the charge decay process of two different powders was investigated.The results indicate that,the attenuation of charge to mass ratio（q/m） of the charged particles presents the exponential relationship in air.The higher the charging voltage is,the larger the initial rate of decay is,and the charge to mass ratio is larger at the same time of repose during the whole decay process.In addition,the charge storage performance of powders is related to the particle size and the relative permittivity,the smaller the particle size is and the larger the relative permittivity is,the better the charge storage performance shows.