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

紫外光/光电子法是在弱电场的作用下，利用紫外光照射光电子发射体发射出的光电子/负离子的独特充电技术。本工作以Au(10 Nm)和掺锡In_2O_3(ITO)(5 Nm)为光电子发射体的圆柱形杀菌灯为光源，在254 nm紫外灯上涂布了一种新型的圆柱形光电子发射器充电器，以产生光电子/负离子。充电实验中使用了单分散的氯化钠颗粒(粒径分别为24和56 nm)作为样品气溶胶。用自行研制的盒式充电器和应用这种充电技术的新型充电器对超细氯化钠颗粒进行充电，并根据凝聚核计数器测量的数浓度来检验充电的有效性。通过对不带电超细粒子的荷电率、穿透率和带电粒子在直流电场作用下的穿透率(充电穿透率)的比较，发现新型充电器比箱式充电器有相当大的优势。虽然在荷电区施加交变电场降低了荷电率，但提高了带电粒子数量计算中最重要的荷电穿透比。

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.