稀土Nd超细纳米晶块体的制备及其物理性能

PREPARATION OF Nd BULK WITH ULTRAFINE NANOCRYSTALLINE STRUCTURE AND ITS PHYSICAL PROPERTY

利用放电等离子烧结技术,制备了稀土金属Nd非晶、非晶与纳米晶双相结构和超细纳米晶的块体材料．利用高分辨透射电镜表征了制备材料的显微结构．通过热力学分析,得出Nd超细纳米晶块体材料由hcp相向bcc相转变的温度约为650℃,相对于传统的粗晶材料降低了约200℃,对传统粗品和超细纳米晶的Nd块体材料分别测定了电阻率、热导率和热膨胀系数及其随温度的变化规律,表明超细纳米晶Nd的电阻率较传统粗晶结构明显升高,而热导率则降低约3倍．

By applying the spark plasma sintering technology, the Nd bulks with amorphous, amorphous and nanocrystalline mixed, and ultrafine nanocrystalline structures were prepared. The microstructures of the Nd bulks are characterized by HRTEM. The physical properties of the ultrafine nanocrystalline Nd bulk, such as the phase transformation features, the electrical resistivity, the thermal conductivity, and the coefficient of thermal expansion, as well as their evolution rules with the temperature, were measured and compared with those of the raw polycrystalline bulk. It was found that the temperature of transformation from hcp to bcc is 650℃, which is reduced by 200℃ in comparison with the raw polycrystalline material. The electrical resistivity is obviously increased as compared with that of the polycrystalline bulk, while the thermal conductivity is remarkably decreased by about 3 times.