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Control and Separation of Ultra Fine Particles using Eleectrostatic Foree

利用静电力控制和分离超细颗粒

基本信息

批准号：
62550685
负责人：
YAMAMOTO Hideo
金额：
$ 1.22万
依托单位：
Institute of lndustrial Science, University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

项目摘要

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.

研究了高温静电沉淀法分离反应气体中化学气相沉积（CVD）法合成的超细颗粒的可行性。采用NH_3/SiCl_4反应体系，在1200 ℃常压下，在管式反应器中制备了氮化硅颗粒。反应体系中产生的副产物NH_4Cl在室温下为固态。因此，在室温下的分离呈现氮化硅和氯化铵颗粒的混合物。在NH_4Cl升华温度340 ℃以上，采用静电沉淀技术，可望直接从反应气流中收集Si_3N_4颗粒，采用交流电晕表面放电的新电极系统，由于直流电晕放电的存在，电晕放电在反应体系的复杂气体组成和高温下不稳定发生。在电极系统上施加峰值电压大于10 KV、频率为10 KHz的高交流电压，产生高频SC电晕沿面放电。采用1 KV左右的负高压作为栅压，从交流电晕中引出单极离子，使粒子单极带电，并作为直流电场，使带电粒子迁移到收集区，在1200 ℃下用CVD法制备的氮化硅粒子尺寸小于亚微米，并被静电分离系统完全收集。X射线衍射分析表明，在500 ℃高温条件下收集的颗粒中不含NH_4Cl副产物颗粒。