Lin Zi-Zhen, Huang Cong-Liang, Zhen Wen-Kai, Feng Yan-Hui, Zhang Xin-Xin, Wang Ge
School of Electrical and Power Engineering, China University of Mining and Technology, Xuzhou, 221116, China.
School of Mechanical Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
Nanoscale Res Lett. 2017 Dec;12(1):189. doi: 10.1186/s11671-017-1969-0. Epub 2017 Mar 11.
The hot-wire method is applied in this paper to probe the thermal conductivity (TC) of Cu and Ni nanoparticle packed beds (NPBs). A different decrease tendency of TC versus porosity than that currently known is discovered. The relationship between the porosity and nanostructure is investigated to explain this unusual phenomenon. It is found that the porosity dominates the TC of the NPB in large porosities, while the TC depends on the contact area between nanoparticles in small porosities. Meanwhile, the Vickers hardness (HV) of NPBs is also measured. It turns out that the enlarged contact area between nanoparticles is responsible for the rapid increase of HV in large porosity, and the saturated nanoparticle deformation is responsible for the small increase of HV in low porosity. With both TC and HV considered, it can be pointed out that a structure of NPB with a porosity of 0.25 is preferable as a thermoelectric material because of the low TC and the higher hardness. Although Cu and Ni are not good thermoelectric materials, this study is supposed to provide an effective way to optimize thermoelectric figure of merit (ZT) and HV of nanoporous materials prepared by the cold-pressing method.
本文采用热线法探测铜和镍纳米颗粒填充床（NPBs）的热导率（TC）。发现了热导率随孔隙率的下降趋势与目前已知的不同。研究了孔隙率与纳米结构之间的关系以解释这一异常现象。结果发现，在大孔隙率下孔隙率主导着NPB的热导率，而在小孔隙率下热导率取决于纳米颗粒之间的接触面积。同时，还测量了NPBs的维氏硬度（HV）。结果表明，纳米颗粒之间接触面积的增大导致大孔隙率下HV的快速增加，而饱和纳米颗粒变形导致低孔隙率下HV的小幅增加。综合考虑热导率和硬度，可以指出，孔隙率为0.25的NPB结构由于热导率低和硬度较高，作为热电材料是优选的。尽管铜和镍不是良好的热电材料，但本研究旨在为优化通过冷压法制备的纳米多孔材料的热电优值（ZT）和硬度提供一种有效方法。
