用于制备纳米粉体的铝丝电爆炸等离子体空间分布及扩散特性

Characteristics of Spatial Distribution and Diffusion of Plasmas Generated by Exploding Aluminum Wires for Nanoparticle Preparation

金属丝在快脉冲电流驱动下发生爆炸,等离子体迅速扩散并与氛围气体相互作用,产生亚微米或纳米尺度的金属粉末。研究电爆炸过程的能量沉积过程及等离子体特性对于认识纳米粉体形成机制及进行参数优化具有重要意义。为此,利用光学–电学联合诊断方法,对微秒脉冲作用下,气压0.1～1.0 MPa,长度2～10 cm,直径0.1～0.4mm铝丝电爆炸现象进行了实验研究。根据电压、电流测量结果,计算并分析了沉积能量随气压、铝丝规格以及初始储能的变化规律。通过分幅成像技术与激光阴影成像等光学观测手段,对电爆炸等离子体的空间形态及扩散过程进行了观测。研究结果表明:增加气压、减小铝丝规格以及提高储能电容器充电电压均可以提高比沉积能量,而比沉积能量是影响等离子体空间分布及扩散特性的重要因素;在沉积能量不足时,等离子体沿轴向分布极不均匀,且扩散较慢;而增大比沉积能量可以有效抑制其空间分布不均匀性,同时提高等离子体扩散速度。

Driven by pulsed current,a metal wire explodes due to joule energy deposition.Plasmas generated by explosion diffuse rapidly into ambient gases and is condensated into nanoparticles.Investigation on characteristics of plasmas is important to understand the mechanism of formation of the nanoparticles.In this paper,experiments of microsecond electrical explosion(2~10 cm in length,0.1~0.4 mm in diameter)in 0.1~1.0 MPa argon gas were carried out with electrical and optical measurements.The influences of experimental parameters,including ambient pressures,wire size,and applied voltage,on the energy deposition were obtained and analyzed.Moreover,using multi-frame photographs and shadowgraphs,the spatial distribution and diffusion characteristics were observed.The energy deposition was found to increase with pressures and applied voltage and to decrease with wire sizes.When the energy deposition was insufficient,the plasma is inhomogeneous along the axial direction and expansion velocity is relative low.Increasein energy deposition will suppress the non-uniformity of spatial distribution and improve the expansion velocities.