Sheath formation around a dielectric droplet in a He atmospheric pressure plasma
Sheath formation around a dielectric droplet in a He atmospheric pressure plasma
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DOI：
10.1063/5.0103446
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发表时间：
2022-08
影响因子：
3.2
通讯作者：
M. Meyer;G. Nayak;P. Bruggeman;M. Kushner
中科院分区：
文献类型：
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作者：
M. Meyer;G. Nayak;P. Bruggeman;M. Kushner
正在研究大气压等离子体和液体之间的界面相互作用，以解决从纳米颗粒合成到去污和化肥生产的各种应用。其中许多应用涉及激活液滴，其中液滴完全浸入血浆中并与血浆协同作用。为了更好地理解这些相互作用，对大气压下工作在氦中的射频辉光放电进行了二维模拟，其中嵌入了尺寸为几十微米的有损介质液滴。在射频循环中，研究了液滴周围形成的鞘的性质。体等离子体中的电场使介质液滴极化，而外部电场中的电子漂移被液滴遮挡。体电场和鞘电场之间的相互作用在液滴一侧的赤道产生E/N(电场/气体数密度)最大，其中体电场和鞘电场沿同一方向排列，沿相反的赤道方向最小。由于电阻加热，电子温度Te在液滴赤道上方和下方达到最大45°，在那里每个电子的沉积功率最高。虽然液滴平均带负电荷，但液滴上的电荷密度在两极是正的，在赤道是负的，因为电子的运动主要是由于极地的扩散，但由于赤道的漂移。
Interactions at the interface between atmospheric pressure plasmas and liquids are being investigated to address applications ranging from nanoparticle synthesis to decontamination and fertilizer production. Many of these applications involve activation of droplets wherein the droplet is fully immersed in the plasma and synergistically interacts with the plasma. To better understand these interactions, two-dimensional modeling of radio frequency (RF) glow discharges at atmospheric pressure operated in He with an embedded lossy dielectric droplet (tens of microns in size) was performed. The properties of the sheath that forms around the droplet were investigated over the RF cycle. The electric field in the bulk plasma polarizes the dielectric droplet while the electron drift in the external electric field is shadowed by the droplet. The interaction between the bulk and sheath electric fields produces a maximum in E/N (electric field/gas number density) at the equator on one side of the droplet where the bulk and sheath fields are aligned in the same direction and a minimum along the opposite equator. Due to resistive heating, the electron temperature Te is maximum 45° above and below the equator of the droplet where power deposition per electron is the highest. Although the droplet is, on the average, negatively charged, the charge density on the droplet is positive on the poles and negative on the equator, as the electron motion is primarily due to diffusion at the poles but due to drift at the equator.