高纯多晶LaB6纳米块体阴极材料的制备及表征

采用放电等离子烧结技术, 以氢直流电弧法制备的La-LaH₂纳米粉末为原料, 制备了高纯LaB₆多晶纳米块体热阴极材料. 系统研究了LaH₂的脱氢反应、SPS合成LaB₆的烧结反应式, 并用XRD、SEM、TEM和AFM对LaB₆烧结块体的相与结构进行了表征. 实验结果表明, LaH2在796.4℃时发生脱氢反应; SPS制备得到了单相LaB₆纳米多晶块体, 纯度达到99.867%, 相对密度达到99.2%, 和其他烧结方法相比, 样品显微硬度及抗弯强度等性能显著提高. 晶体为大小均匀, 形态规则完整的等轴晶, 50MPa, 烧结温度1250～1350℃范围内平均晶粒尺寸为120nm, 随烧结温度的升高, 晶粒尺寸逐渐增大.

Fabrication and Characterization of High-purity Nanostructured Bulk LaB6 Polycrystal Cathode Material

La-LaH₂ nanopowders were prepared by hydrogen arc plasma method, and then the mixed nanopowders of La-LaH₂ and B were in situ sintered by Sparkle Plasma Sintering (SPS) method in oxygen free system. High-purity LaB₆ polycrystal nanostructured bulk was successfully synthesized by SPS. The dehydrogenation of LaH₂ nanopowders and the reaction equation of sintering LaB₆ were studied. The phase and microstructure of LaB₆ bulks were characterized by using XRD, SEM, TEM and AFM techniques. The results show that the dehydrogenation temperature of LaH₂ nanopowders is 796.4℃. The sintered body is single-phase LaB₆, which has a high purity of 99.867%, and its relative densities is up to 99.2%. The hardness and bend strength of the sintered LaB₆ are much better than those of LaB₆ prepared by other sintering methods. The crystals of LaB₆ bulk are equiaxed crystals, the average grain size of the bulks sintered at 50MPa and 1250-1350℃ is about 120nm. The grains are homogeneous and integrated, and the grain size increases with the raising of sintering temperature.