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微尺度下场致发射对电晕放电的影响机理

Mechanism of the Influence of Field Emission on Corona Discharge at Microscale

  • 摘要: 场致离子化微电晕器件基于一维纳米材料的电场增强效应,可产生大气压非平衡微等离子体,适用于气体检测以及生物医疗等领域,具有响应快、低功耗等特点。但微尺度下的电晕放电属于局部自持的低能放电,其场致发射的作用及影响机制尚不清晰。因此文章基于流体-化学混合模型框架,融合F-N发射模型,建立了常温常压N2-O2混合气体的二维微电晕放电模型。通过与无场致发射放电模型对比,探索不同间距下场致发射对放电动态过程的影响,发现针-板间距减至15 μm时,两种模型放电过程差异很小,表明放电以二次电子发射机制为主导,当间距减至10 μm时,两种模型的放电强度相差近1倍,场致发射的作用及影响不可忽略;通过进一步对电子密度分布、空间电场分布、电流密度等参量进行动态分析,发现场致发射、空间碰撞电离反应和离子轰击二次电子发射之间存在链锁影响规律。

     

    Abstract: Based on the electric field enhancement effect of one-dimensional nanomaterials, field-ionized micro-corona devices can generate atmospheric pressure non-equilibrium micro-plasma, which is suitable for gas detection and biomedical fields with fast response and low power consumption. However, the corona discharge at the microscale is a local self-sustaining low-energy discharge, and the role and influence mechanism of its field emission are still unclear. Therefore, in this paper, based on the fluid-chemical mixing model, the F-N emission model is introduced and coupled to establish a two-dimensional microcorona discharge model for the N2-O2 gas mixture at room temperature and pressure. By comparing with the discharge model without field emission, the effect of field emission on the dynamic process of discharge under different spacing is explored. It is found that when the pin-plate spacing is reduced to 15 μm, the difference in the discharge process between the two models is very small, indicating that the discharge is dominated by the secondary electron emission mechanism, and when the spacing is reduced to 10 μm, the difference in the discharge intensity between the two models is nearly a factor of one, and the role and influence of field emission cannot be neglected; And through further dynamic analysis of electron density distribution, space electric field distribution, current density and other parameters, it is found that there is a chain influence law between field-induced emission, space collision ionization reaction and ion bombardment secondary electron emission.

     

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