等离子体球化处理和放电等离子烧结制备钡钨阴极多孔钨基体

Porous Tungsten Matrix for Ba-W cathode Prepared by Plasma Spheroidization Process and Spark Plasma Sintering

摘要:

采用等离子体球化处理和放电等离子烧结(SPS)相结合的方法制备了钡钨阴极多孔钨基体。研究了等离子体球化处理工艺参数对钨粉的球化率和性能的影响规律,以及SPS制备的多孔钨基体的微观组织和相应钡钨阴极的发射性能。结果表明：当喂粉速率和载气流量分别为2.4 g/min和4.0 L/min时,可得到球化率大于98%,且表面光滑、球形度高的球形钨粉；经球化处理后,钨粉的松装密度和流动性显著提高。与原料钨粉相比,采用球形钨粉制备得到的多孔钨基体的孔隙结构和分布均得到显著改善,且开孔率由18.3%提高至19.7%；相应的钡钨阴极在1050 oC下的饱和脉冲发射电流密度由8.7 A/cm₂提高至11.2 A/cm₂。改善钨粉性能,优化多孔钨基体的微观组织,可大幅度提高钡钨阴极的发射性能。

Abstract:

Porous tungsten matrix for Ba-W cathode was prepared by plasma spheroidization process combined with spark plasma sintering (SPS). The effect of plasma spheroidization process parameters on the spheroidization efficiency and properties of the W powders, microstructure of the porous W matrix sintered by SPS as well as the emission performance of the corresponding Ba-W cathode were investigated. The results show that spherical W powders with smooth surfaces and good sphericity can be obtained when the powder feed rate and carrier gas flow rate is 2.4 g/min and 4.0 L/min, respectively. The spheroidization efficiency is above 98%. The apparent density and flowability of the spherical W powders are enhanced greatly after plasma spheroidization. In contrast to the raw W powders, the structure and distribution of pores within the porous W matrix prepared by the spherical W powders are improved significantly after SPS, and the open porosity increases from 18.3% to 19.7%. The saturation pulse current density of the Ba-W cathode prepared with spherical W powders is 11.2 A/cm₂, which is higher than that of 8.7 A/cm₂ for the Ba-W cathode prepared by the raw W powders. The emission performance of Ba-W cathode can be highly improved by modifying the properties of W powders and microstructure of the porous W matrix.