Study of the influence of discharge loop parameters on anode side on generation characteristics of metal plasma jet in a pulsed vacuum discharge

In a pulsed vacuum discharge,the ejection performance of a metal plasma jet can be effectively improved by preventing charged particles from moving to the anode.In this paper,the effects of resistance and capacitance on the anode side on the discharge characteristics and the generation characteristics of plasma jet are investigated.Results show that the existence of a resistor on the anode side can increase the anode potential,thereby preventing charged particles from entering the anode and promoting the ejection of charged particles along the axis of the insulating sleeve nozzle.The application of a capacitor on the anode side can not only absorb electrons at the initial stage of discharge,increasing the peak value of the cathode hump potential,but also prevent charged particles from moving to the anode,thereby improving the ejection performance of the plasma jet.In addition,the use of a larger resistance and a smaller capacitance can improve the blocking effect on charged particles and further improve the ejection performance of the plasma jet.Results of this study will provide a reference for the improvement of the ejection performance of plasma jets and their applications.

Generation characteristics of a metal ion plasma jet in vacuum discharge

To improve the performance of a metal ion plasma jet in vacuum discharge, an anode-insulated cone-cylinder electrode with insulating sleeve is proposed in this paper. Discharge characteristics and generation characteristics of plasma of the electrode are investigated, effects of diameter of insulating sleeve, variety of cathode material and length of the insulating sleeve on characteristics of metal ion plasma jet are discussed. Results indicate that a directional and steady plasma jet is formed by using the novel electrode with insulating sleeve under high vacuum conditions. Moreover, the properties of metal ion plasma jet are improved by using the aluminum cathode and thin and long insulating sleeve. The study provides strong support for research of vacuum metal ion plasma thruster and ion implantation technology.

新型大气长层流等离子体喷涂方法和研究进展

介绍了一种新型大气等离子喷涂方法,该方法采用特殊内通道结构的直流非转移电弧等离子发生器,可以直接在大气条件下获得长度100~1000 mm之间变化的等离子射流。在大气条件下,等离子射流的流动特性具有"长、直、准"的层流或类层流状态,工作时噪音小于80 dB。在工作参数范围内,等离子射流的长度在固定总气流量条件下可以随输出功率的增加而增长;射流的长度在固定输出功率的条件下随总气流量的增加而减小。当使用在大气等离子喷涂技术中时,会为飞行粉末颗粒带来超长的加热和加速过程。文中详细介绍了大气层流等离子喷涂技术的研究历史和研究现状,以及研究团队利用该新型技术制备的6种涂层的显微结构、颗粒的飞行和加热特点,并对比了目前其他大气等离子喷涂技术的结果。结果表明,文中介绍的方法在最低的输出功率和气流量条件下,为金属和陶瓷颗粒提供了超长的飞行和加热条件,表现为较低的颗粒飞行速度和超高的颗粒表面温度。可以在不同的射流长度或喷涂距离下,获得不同的颗粒熔化状态或涂层结构,并发现可以直接在大气条件下获得大规模气液共沉积的涂层。

具有内外分段阳极结构的金属离子等离子体推进器的放电特性

金属离子等离子体推进器是一种通过烧蚀阴极金属材料,产生电离度高的金属离子等离子体,在Hump峰加速作用下从而定向喷射形成推力的推进器类型。文中提出了一种带有分段阳极结构的金属离子等离子体推进器(SA-MIPT),该结构由圆锥状阴极、圆筒状绝缘套桶以及圆环状分段阳极组成。基于该金属离子等离子体推进器,探究了峰值电压维持时间t1以及阳极吸收电子对金属等离子体的生成及喷射性能的影响。研究结果表明,当t1从0.4μs增大到1.2μs时,单脉冲放电中生成的等离子体的定向传播速度、离子电流幅值以及离子电流与阴极电流的比值Gr分别提高了1.7倍、18倍、15倍。此外,研究发现采用减小阳极裸露面积或者阳极侧串联电阻的方法,能够有效提高从推进器喷口喷射出去的等离子体射流的喷射性能。当内阳极宽度W从2 mm减小到0.1 mm时,放电生成的离子电流峰值以及对应的Gr值分别提高了2.41倍、2.66倍。当阳极宽度W=2mm不变,在内阳极侧串联1 MΩ电阻后,放电生成的离子电流峰值以及对应的Gr值分别提高了2.24倍、2.52倍。

等离子喷注Cr粉制备Al-Cr合金的组织研究

采用等离子喷注技术将不同粒径的Cr粉喷注到铝液中制备Al-Cr合金,并对试样显微组织进行分析。结果表明：等离子喷注技术能将Cr粉充分注入铝液,且经等离子弧活化的Cr粉能更好地与铝液反应;粒径为45～50μm的Cr粉注入可制得组织细小、分布均匀的Al-Cr合金,经650℃热处理8 h能大幅提高合金的组织均匀性,且细化和球化了晶粒。