Control and Separation of Ultra Fine Particles using Eleectrostatic Foree

高温度静电抑制方法的可行性被证明用于分离超精细颗粒的超精细颗粒，通过热激活的CVD（化学蒸汽沉积）技术从反应气体流中合成。Silicon nitride particles were produced in a tubular flow reactor by using the NH_3/SiCl_4 reaction system at 1200 C and atmospheric pressure。反应系统将NH_4Cl按-产品在房间温度下处于固态状态。房间温度下的分离，因此，硅腈和氯化氨粒子的混合物。使用高于340 ° C的静电预处理技术，并使用NH_4Cl的sublation温度，因此，如果Si_3N_4颗粒可以直接从反应气体流收集，没有NH_4Cl的颗粒，使用Ac-corona表面放电的新的电子系统已经开发出来，以有效地充电颗粒，因为dc-电晕释放在反应系统的复杂气体组成和高温下不能稳定地使用。一个高AC电压，峰值电压高于10千伏，频率为10千赫，已应用于电气系统产生高频率SC-电晕表面放电。负高电压约1 KV使用了作为一个grid voltage to take out monopolar ions from the AC-corona in order to charge the particles monopolar and作为DC-field voltage to migrate the charged particles to a collection zone.硅nitride particles在1200 C by the CVD method were under submicron size and completely collected by the electrostatic separation system。X射线差异分析表明，所收集的粒子在500 ° C的高温条件下不含NH_4Cl按产品的粒子。

The feasibility of the high temperature electrostatic precipitation method was demonstrated for separation of the ultra-fine particles synthesized by thermally activated CVD (Chemical Vapor Deposition) technique from a reaction gas stream. Silicon nitride particles were produced in a tubular flow reactor by using the NH_3/SiCl_4 reaction system at 1200゜C and atmospheric pressure. The reaction system produces the NH_4Cl by-product that is in solid state at room temperature. Separation under room temperature presents, therefore, a mixture of silicon nitride and ammonium chloride particles. Using the electrostatic precipitation technique above about 340゜C, the sublimation temperature of NH_4Cl, it is expected that Si_3N_4 particles as the product may be directly collected from the reaction gas stream, without particles of the NH_4Cl by-product.The new electrode system using Ac-corona surface discharge was developed to charge the particles efficiently because Dc-corona discharge did not stably occur in complex gas composition of the reaction system and at high temperature. A high AC-voltage with peak voltage above 10KV and frequency of 10KHz was applied for the electrodes system to generate a high frequency SC-corona surface discharge. Negative high voltage about 1KV was used as a grid voltage to take out monopolar ions from the AC-corona in order to charge the particles monopolar and as DC-field voltage to migrate the charged particles to a collection zone.The silicon nitride particles prepared at 1200゜C by the CVD method were under submicron size and completely collected by the electrostatic separation system. The X-ray diffraction analysis indicated that the particles collected under high temperature condition of 500゜C contains no particle the NH_4Cl by-product.