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

UV/光电子充电法是我们开发的一种独特的充电技术，它利用弱电场作用下的紫外光照射从光电子发射器发射的光电子/负离子。本课题研制了一种新型的圆柱形光电子发射体充电器，该充电器涂敷在254 nm紫外线灯上，以圆柱形杀菌灯为光源，利用Au（10 nm）和掺锡氧化铟（ITO）（5 nm）组成的光电子发射体产生光电子/负离子。单分散NaCl颗粒（粒径：24和56 nm）被用作我们的充电实验中的样品气溶胶。用先前开发的箱式充电器和应用该充电技术的上述新型充电器对超细NaCl颗粒进行充电，并基于由凝聚核计数器测量的数浓度来检查有效性。在直流电场作用下，对不带电超细颗粒的荷电率、穿透率和带电颗粒的穿透率（荷电穿透比）进行了比较，发现新型荷电器较箱式荷电器有较大的优势。虽然在充电区域施加交变电场会降低充电率，但增加了充电穿透率，这是计算带电粒子数量的最重要因素。

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.