Lin Zi-Zhen, Huang Cong-Liang, Huang Zun
School of Electrical and Power Engineering, China University of Mining and Technology, Xuzhou 221116, China.
J Nanosci Nanotechnol. 2018 May 1;18(5):3413-3418. doi: 10.1166/jnn.2018.14681.
The hot-wire method and the four-probe resistivity method are applied to probe the thermal conductivity (k) and the electric conductivity (σ) of Cu and Ni nanoparticle packed beds (NPBs). A fitting method based on classical physical theory is devised to separate ke (electronic thermal conductivity) and kp (phonon thermal conductivity) from k at room temperature. Results turn out that kp only accounts for a small proportion of k (4-20%); the proportion decreases with increasing porosity or temperature. Most importantly, this fitting method provides a simple way to separate ke and kp from k at room temperature. The Wiedemann-Franz law is checked and is found to be unsuitable for NPBs. The Lorenz number (L) is calculated from measurements of ke, k, and σ. Results turn out that L is found to be 50-60 times that of the bulk. With a Seebeck coefficient (S) measured, the thermoelectric property of NPBs is also calculated. We find that the NPB possess an advantage in thermoelectric property than bulk, the thermoelectric figure of merit (ZT) of Ni (Cu) NPBs can be 20.17 (1.87) times that of bulk Ni (Cu). The effect of porosity on ZT is also discussed, and results show that a NPB with a small porosity is more preferable as a thermoelectric material. With a small porosity, ZT can be even 1.73 times that of a large porosity. Although metals are not good thermoelectric material, the method in this paper supplies a way to improve the thermoelectric property of other thermoelectric materials.
采用热线法和四探针电阻率法来探测铜和镍纳米颗粒填充床（NPBs）的热导率（k）和电导率（σ）。设计了一种基于经典物理理论的拟合方法，以在室温下从k中分离出电子热导率（ke）和声子热导率（kp）。结果表明，kp仅占k的一小部分（4%-20%）；该比例随孔隙率或温度的升高而降低。最重要的是，这种拟合方法提供了一种在室温下从k中分离ke和kp的简单方法。对维德曼-夫兰兹定律进行了检验，发现其不适用于NPBs。根据ke、k和σ的测量值计算了洛伦兹数（L）。结果表明，L是块体材料的50-60倍。通过测量塞贝克系数（S），还计算了NPBs的热电性能。我们发现NPBs在热电性能方面比块体材料具有优势，镍（铜）NPBs的热电优值（ZT）可以是块体镍（铜）的20.17（1.87）倍。还讨论了孔隙率对ZT的影响，结果表明，孔隙率小的NPB作为热电材料更具优势。孔隙率小时，ZT甚至可以是孔隙率大时的1.73倍。虽然金属不是良好的热电材料，但本文中的方法为改善其他热电材料的热电性能提供了一条途径。
