纳米Mg_2Si材料的制备及热电性能研究

Research on preparation and thermoelectric properties of nano-size Mg_2Si

以高纯Mg,Si粉合成得到的Mg_2Si微米粉体为原料,采用机械球磨方法制备纳米Mg_2Si粉体。对球磨过程中球磨介质、球料比、转速及球磨时间进行分析,发现:通过机械球磨微米Mg_2Si的方法,以正己烷为球磨介质,选取WC球和罐,在球料比为20:1、转速为370r/min、球磨70h时即可获得平均晶粒尺寸约为十几纳米的Mg_2Si纳米粉体。采用放电等离子体烧结(SPS)烧结纳米Mg_2Si粉体,块体晶粒长大,但仍在100nm左右;由于晶界散射作用,纳米块体Mg_2Si热导率明显降低,电导率、Seebeck系数一定程度下降,综合热电三因素,纳米Mg_2Si块材在800K时获得最大ZT值,为0.36,明显优于微米块体材料。

Nano-sized Mg_2Si powder was prepared by mechanical milling micro-sized Mg_2Si which was obtained from Mg and Si powder. The analysis about milling mediator,ratio of grinding media to material,rotational speed and time indicated that nano-size Mg_2Si powder can be successfully obtained by mechanical milling method with the ration of grinding media to material was 20： 1,rotation of 370 r / min,and 70 h. According to the lattice scattering,Nano-sized Mg_2Si own lower thermal and electrical conductivity but higher Seebeck coefficient. Taken all of the three factors into consideration,nano-sized Mg_2Si obtained higher ZT of 0. 36 at 800 K,which was much higher than that of micro-sized Mg_2Si material.