Espin M J, Valverde J M, Quintanilla M A S, Castellanos A
Department of Applied Physics II, University of Seville, Avenida Reina Mercedes, 41012 Seville, Spain.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Jan;79(1 Pt 1):011304. doi: 10.1103/PhysRevE.79.011304. Epub 2009 Jan 27.
The electromechanical behavior of a gas-fluidized bed of insulating silica nanoparticles is investigated. When fluidized by gas, these nanoparticles form highly porous agglomerates of size of the order of hundreds of microns, which gives rise to a nonbubbling fluidization regime. Bed expansion is enhanced by an imposed alternating electric field for oscillation frequencies in the range between tens and hundreds of hertzs and field strengths of about 1 kV/cm . Nanoparticle agglomerates are naturally charged and experience forced oscillations that cause an increase of the gas flow shear on their surface. As a consequence, the agglomerate size is expected to decrease, which can explain the observed behavior. A model based on the balance between attractive and flow shear forces is presented that accounts for agglomerate size reduction as the strength of the field is increased.
研究了绝缘二氧化硅纳米颗粒气固流化床的机电行为。当用气体流化时，这些纳米颗粒形成尺寸为数百微米量级的高度多孔团聚体，这导致了一种非鼓泡流化状态。对于几十到几百赫兹的振荡频率和约1 kV/cm的场强，外加交变电场会增强床层膨胀。纳米颗粒团聚体自然带电并经历强迫振荡，这会导致其表面气体流动剪切力增加。因此，团聚体尺寸预计会减小，这可以解释所观察到的行为。提出了一个基于吸引力和流动剪切力平衡的模型，该模型解释了随着场强增加团聚体尺寸减小的现象。
