高纯多晶LaB_6纳米块体阴极材料的制备及表征

Fabrication and Characterization of High-purity Nanostructured Bulk LaB_6 Polycrystal Cathode Material

采用放电等离子烧结技术,以氢直流电弧法制备的La-LaH_2纳米粉末为原料,制备了高纯LaB_6多晶纳米块体热阴极材料.系统研究了LaH_2的脱氢反应、SPS合成LaB_6的烧结反应式,并用XRD、SEM、TEM和AFM对LaB_6烧结块体的相与结构进行了表征.实验结果表明,LaH_2在796.4℃时发生脱氢反应;SPS制备得到了单相LaB_6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.

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.