Effect of Manganese Dioxide Nanorods on the Thermoelectric Properties of Cement Composites

The Seebeck coefficient of plain cement paste is usually less than 1 μV/°C. To enhance the thermoelectric performance of cement composites, a kind of MnO2 powder was synthesized and used as a thermoelectric component in this work. The synthesized MnO2 powder was proven to be a kind of effective thermoelectric component in cement paste. The synthesized MnO2 powder possesses a nanorod structure with a diameter of about 50 nm and a length up to 1.4 μm. The measured Seebeck coefficient of the compacted MnO2 powders was about −5,490 μV/°C. The nanorod structured design was proven to be an effective method to increase the Seebeck coefficient of the thermoelectric component in this research. Then the MnO2 nanorods were incorporated into the cement matrix to enhance the thermoelectric effect of cement composites. A relatively high Seebeck coefficient of about −3,085 μV/°C could be obtained when the content of MnO2 powder was 5.0% by weight of cement, which is more than 1,000 times higher than that of the cement paste without MnO2 powder. And at this content, the electrical conductivity, thermal conductivity, and ZT of cement composites were 1.88×10−4 S/m, 0.72 W/mK, and 7.596×10−7, respectively. The thermoelectric effect of the cement composites is enhanced mainly due to the enhanced Seebeck coefficient, while the influence of electrical conductivity and thermal conductivity caused by MnO2 powders is not as obvious as Seebeck coefficient.