Studies on Thermoelectric and Compressive Properties of Ni-NiO at Carbon Fiber–Reinforced Cement Composites

Nickel films were electroplated onto carbon fibers in an electrolyte irradiated by 2.45 GHz, referred to as Ni/Cf, and subsequently partly oxidized to form NiO in air. The resulting carbon fibers with oxidized Ni films were incorporated into calcium aluminate cement to create cement-based composites, known as NiO-Ni/CFRC. The impact of oxidation temperatures and fiber mass fractions of the Ni/Cf on the thermoelectric properties of NiO-Ni/CFRC was investigated. The results revealed that the NiO-Ni/CFRC doped with 1.5 wt% prepared at a oxidation temperature of 450°C for 2 h exhibited the most favorable thermoelectric properties. Specifically, the Seebeck coefficient and electric conductivity were found to be 6,651 μV·K−1 and 0.13 S·m−1, respectively, at an ambient temperature of 30°C. The resulting dimensionless constant ZT value of the NiO-Ni/CFRC peaked at 2.7×10−3, marking a 6.7-fold increase compared to Ni/Cf. Moreover, the compressive strength of Ni-NiO/CFRC could maintain 65.1 MPa, representing a 10.9% increase, and the compressive strain could reach 0.43%, marking an 8% improvement, compared to pure cement. These results suggest Ni-NiO could offer new opportunities for the application of sustainable energy technologies and smart materials in the field of buildings and construction in future cities.