STUDY OF DYNAMIC BEHAVIOR OF NANOMETER-SIZED AEROSOL PARTICLES AND ION CLUSTERS

本研究采用微分迁移率分析仪（DMA）结合凝聚核计数器（CNC）或静电计（EM）作为粒子探测器，研究了纳米尺度气溶胶粒子和离子团簇的动力学行为。所得结果可概述如下。在第一年，迁移率的理论和实验研究的情况下，极细的颗粒需要低电场进行分类时，气溶胶粒径测量与DMA已经进行。因此，很明显，迁移率的变化是由于（i）扩散混合的轨迹不同大小的粒子，和（ii）存在的空间电荷场，除了施加的字段。此外，最重要的结果可以总结如下：（i）小于平均值的颗粒在小于理想值的电压下被分类;（ii）大于平均值的颗粒在大于理想值的电压下被分类;（iii）大于平均值的颗粒在大于理想值的电压下被分类。 ...更多信息 e理想;（iii）较大的气溶胶浓度导致较大的位移;（iv）由于布朗扩散效应，即使在低气溶胶浓度下也会发生迁移率位移;以及（v）迁移率位移仅在第一DMA中重要，并且对于第二DMA可以安全地忽略。在第二年，使用串联DMA系统进行粒度测量，以根据第一年的结果准确确定颗粒的尺寸。通过金属丝网和层流管的纳米尺寸的颗粒的渗透已经进行。所获得的结果可以总结为：（i）粒子中电荷的存在不影响它们的穿透行为;（ii）现有的理论，Cheng和Yeh对于金属丝网以及Gormley和Kennedy对于管，对于Stokes-Einstein直径低至2nm的粒子是准确的;以及（iii）粒子不从金属表面反弹，即，在此基础上，进行了双极空气离子荷电和中和气溶胶粒子的实验研究。结果表明，对于大于3nm的粒子，只要选择适当的离子迁移率和质量，我们的实验结果与Fuchs的理论符合得很好。在小于3nm的尺寸范围内，偏差是相当大的和突然的。少

In this research, dynamic behavior of nanometer-sized aerosol particles and ion clusters was studied by measuring with the differential mobility analyzer (DMA) combined with a condensation nucleus counter (CNC) or an electrometer (EM) as a particle detector. The results obtained can be summarized below. At the first year, a theoretical and experimental study of mobility shift in the case of extremely fine particles requiring low electric fields for their classification when performing aerosol size measurements with the DMA has been carried out. As a result, it was made clear that the mobility shift is due to (i) diffusive mixing of trajectories of different-sized particles, and (ii) the existence of a space-charge field in addition to the applied field. Furthermore, the most important results can be summarized thus : (i) particles smaller than the average are classified at voltages smaller than the ideal ; (ii) particles larger than the average are classified at voltages larger than th … More e ideal ; (iii) larger aerosol concentrations lead to larger shifts ; (iv) mobility shifts occur even at low aerosol concentrations due to Brownian diffusion effects ; and (v) mobility shifts are important only in the first DMA,and can be safely neglected for the second. At the second year, particle size measurement were done using a tandem DMA system to accurately determine the size of the particles on the basis of the results of the first year. Penetration of nanometer-sized particles through a wire screen and a laminar flow tube has been carried out. The results obtained can be summarized thus : (i) the presence of electrical charges in the particles do not affect their penetration behavior ; (ii) the existing theories, Cheng and Yeh for wire screens and Gormley and Kennedy for tubes, are accurate for particles with Stokes-Einstein diameter down to 2nm ; and (iii) particles do not rebound from the metallic surfaces, i.e., all the particle-metal collisions are effective, Furthermore, an experimental study of charging and neutralization of aerosol particles by bipolar air ions has been carried out. As a result, if adequate value of ion mobility and mass are chosen, our experimental results agree very well with Fuchs'theory for particles larger than about 3nm. In the size range below 3nm, deviations are considerable and abrupt. Less