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在热电材料里引入纳孔能有效降低材料的热导率从而提高其热电性能,但纳米孔洞的引入也可能影响材料的力学性能。以圆柱孔理想单晶Mg_2Si块体热电材料为研究对象,建立不同孔径、孔隙率以及分布形式的纳孔Mg_2Si材料的原子模型,采用分子动力学模拟方法研究不同模型下材料的拉伸力学性能。结果表明:①纳孔的引入造成Mg_2Si热电材料的极限应力和弹性模量的降低,而纳孔孔隙率、分布形式都会影响到材料的极限应力,而材料的弹性模量主要与孔隙率有关,孔隙率越大,材料的弹性模量越低;②纳孔的引入不仅减小材料的有效荷载面积,更重要的是造成材料内部应力分布不均匀,而材料所能承受的拉伸方向的应力极限是一定的,因而当纳孔Mg_2Si热电材料平均应力远小于完整块体的极限应力时,材料内部最薄弱的地方的应力就已达到其极限应力,造成材料的破坏。
The introduction of nano-pores into the thermoelectric material can effectively reduce the thermal conductivity of the material to improve its thermoelectric properties, but the introduction of nanoholes may also affect the mechanical properties of the material. In this paper, cylindrical Mg_2Si bulk single crystal Mg_2Si bulk thermoelectric material was taken as the research object to establish the atomic model of nano-pores Mg_2Si with different pore sizes, porosity and distribution. The molecular dynamics simulation was used to study the tensile mechanical properties of the materials. The results show that: (1) The introduction of nano-pores leads to the decrease of ultimate stress and elastic modulus of Mg_2Si thermoelectric materials, while the porosity and distribution of nano-pores affect the ultimate stress of the material. The elastic modulus of the material is mainly related to the porosity, The larger the porosity, the lower the modulus of elasticity of the material; (2) The introduction of nano-pores not only reduces the effective load area of the material, but more importantly, the stress distribution in the material is not uniform and the tensile stress When the average stress of nanocrystalline Mg_2Si thermoelectric material is far less than the ultimate stress of the intact block, the stress in the weakest part of the material has reached its ultimate stress, resulting in the destruction of the material.