Magnesium phosphate cement-based composites with selective significantly enhanced thermoelectric potential

Thermoelectrics give building materials the ability to utilize waste heat directly and other additional functionalities, which reduce the whole life cycle energy consumption of the building industry. Magnesium phosphate cement can provide more ionic environment due to their neutralization and reaction properties, comparing with Portland cement. We further improved the thermoelectric properties of MPC composites, especially the Seebeck coefficient, cooperating with silica or in-situ polymerized polyacrylamide. Specifically, SiC adheres to the surface of the MPC-hardened matrix, forming electron/hole transport sites and enlarging the ionic concentration difference within the pores, while polyacrylamide provides exclusive anion transport channels, which provides a unique N-type thermoelectric mechanism. The results show that 10% doping of acrylamide achieves the best N-type MPC with a Seebeck coefficient of −3.85 mV/K, while 5% doping of SiC achieves the best P-type MPC with a Seebeck coefficient of +7.10 mV/K, and the sum of absolute values of the two is 2.5 times higher than the Seebeck coefficient of the cementitious materials reported so far. Moreover, acrylamide and SiC also have the potential to improve the thermoelectric properties of MPC along with the potential to improve the mechanical properties, toughness and wear resistance of MPC.