Lai Chen, Wang Jinshu, Zhou Fan, Liu Wei, Zhang Quan, Luo Deng, Guo Gencai, Hao Yaowu
College of Materials Science and Engineering, Beijing University of Technology, Chaoyang District, Beijing, 100124, P. R. China.
Department of Materials Science and Engineering, University of Texas at Arlington, Arlington 76019, United States.
J Nanosci Nanotechnol. 2018 Jun 1;18(6):4236-4242. doi: 10.1166/jnn.2018.15186.
In this study, rhenium-tungsten mixed particles with different content of rhenium have been prepared by spray-drying method followed by hydrogen reduction. Using such particles, the cathodes have been prepared by powder metallurgy followed by impregnating BaO, CaO, and Al2O3 with 4:1:1 molar ratio. After proper activation, electron emission test is performed in standard parallel-plate diode configuration. The emission results reveal that the Re-W matrix cathode containing 75% rhenium has the highest direct current emission density of 11.67 A/cm2 at 1000 °C. The work function of Re-W matrices has been investigated by density functional theory method in the frame of the generalized gradient approximation (GGA). The theoretical calculation results indicate that the work function of the matrix has limited contribution to the emission current density of Re-W matrix dispenser cathode. The in situ AES, SEM, and XRD were applied and the results reveal that the superior emission property of the 75Re cathode is owing to a plenty of nanoparticles and higher free barium concentration on the cathode surface, which is attributed to the Re3W single phase in 75Re matrix.
在本研究中，通过喷雾干燥法然后进行氢气还原制备了具有不同铼含量的铼 - 钨混合颗粒。使用这些颗粒，通过粉末冶金法制备阴极，然后用摩尔比为4:1:1的BaO、CaO和Al₂O₃进行浸渍。经过适当活化后，在标准平行板二极管配置下进行电子发射测试。发射结果表明，含75%铼的Re - W基阴极在1000℃时具有最高的直流发射密度，为11.67 A/cm²。在广义梯度近似（GGA）框架下，采用密度泛函理论方法研究了Re - W基体的功函数。理论计算结果表明，基体的功函数对Re - W基浸渍型阴极的发射电流密度贡献有限。应用原位俄歇电子能谱（AES）、扫描电子显微镜（SEM）和X射线衍射（XRD），结果表明75%铼阴极优异的发射性能归因于阴极表面大量的纳米颗粒和较高的游离钡浓度，这是由于75%铼基体中的Re₃W单相所致。
