Development of Charging Device for Superfine Particles Using UV/Photoelectron Method

紫外/光电子法是利用弱电场作用下紫外照射光电子发射器发射的光电子/负离子进行充电的一种独特技术。研制了一种新型包覆在254nm紫外灯表面的圆柱形光电子发射器充电器；采用由Au （10nm）和锡掺杂In_2O_3 (ITO) （5nm）组成的光电子发射器的圆柱形杀菌灯作为紫外光源，产生光电子/负离子。以单分散的NaCl颗粒（粒径分别为24 nm和56nm）作为气溶胶样品进行充电实验。对超细氯化钠颗粒分别采用先前研制的盒式充电机和上述新型充电机进行充电，并通过缩聚核计数器测量的电荷浓度来验证其有效性。在直接电场作用下，对未带电超细粒子的充电比、穿透比、带电粒子的穿透比（充电-穿透比）进行了比较，发现新型充电器明显优于盒式充电器。在充电区施加交变电场虽然降低了充电比，但增加了计算带电粒子数最重要的电荷穿透比。

UV/photoelectron method developed by us is a unique charging technique using the photoelectrons/negative ions emitted from a photoelectron emitter by UV irradiation under an application of weak electric field. In this work, the new type charger of cylindrical photoelectron emitter coated on 254nm of UV-lamp was developed ; cylindrical germicidal lamp with photoelectron emitter composed of Au (10nm) and tin-doped In_2O_3 (ITO) (5nm) was used as UV-light source to generate the photoelectrons/negative ions. Mono-dispersed NaCl particles (particle diameter : 24 and 56nm) were used as sample aerosols in our charging experiments. Superfine NaCl particles were charged with a box type charger developed previously and the above new type charger applying this charging technique and, the validity was examined based on the number concentration measured by a condensation nuclei counter. The considerable predominance of the new type charger over the box type charger was found in comparison of charging ratio and penetration ratio of uncharged superfine particles and, penetration ratio of charged particles (charging-penetration ratio) under the application of direct electric field. Although charging ratio was decreased by the application of alternating electric field in the charging region, charging-penetration ratio, the most important thing in counting the number of charged particles, was increased.