چكيده به لاتين
Cement is one of the most widely used construction materials. In recent decades, generating electrical current from cementitious materials has garnered significant attention. Thermoelectric materials can directly convert waste energy and excess heat from the environment into electrical energy. Considering the widespread use of cement-based materials in infrastructures, generating electrical energy from cement-based infrastructures using thermoelectric properties can be considered as one of the methods for energy supply. The low conductivity of cement paste and its minimal charge carriers pose a challenge for harvesting energy through the thermoelectric method. To harvest energy from concrete using the thermoelectric method, its electrical and thermal properties must be altered properly by increasing the Seebeck coefficient and electrical conductivity while reducing thermal conductivity. Several methods have been proposed to enhance the thermoelectric properties of cement paste. However, some of these methods have proven to be ineffective or insufficient, while others, despite improving the thermoelectric properties, are not suitable for use in civil infrastructure due to the reduction in cement strength and high cost. Unlike conductive materials that quickly conduct heat, semiconductor materials transfer heat at a slower rate. In this study, graphene quantum dots and molybdenum disulfide have been used as semiconductor materials to enhance the thermoelectric properties of cement paste. In this study, graphene quantum dots and molybdenum disulfide have been employed as semiconductor materials to enhance the thermoelectric properties of cement paste. Hypotheses such as the improvement of electrical conductivity due to the increase in the number of electric charge carriers resulting from the addition of semiconductor materials to the samples, the enhancement of the Seebeck coefficient due to the occurrence of a more stable temperature difference, and the reduction of thermal conductivity through phonon scattering owing to the small size of the additives have been considered to enhance the thermoelectric performance of cement paste. In addition, merely enhancing the thermoelectric performance of the cement paste is not sufficient, and the presence of these additive particles should not compromise the strength of the cement. In this study, electrical conductivity, Seebeck coefficient, thermal conductivity, and the figure of merit for four different samples were calculated through experimental analyses. By incorporating 0.12% by weight of graphene quantum dots and 0.10% by weight of molybdenum disulfide nanoparticles separately, and finally their combination, the dimensionless figure of merit, indicating thermoelectric performance, increased from 3.29 × 10^-8 in the reference sample to 4.39 × 10^-6, 9.46 × 10^-7, and 2.56 × 10^-6, respectively. Furthermore, the addition of these nanoparticles to the cement matrix resulted in a reduction of thermal conductivity by approximately 12%, which is one of the factors contributing to energy consumption reduction in structures. Simultaneous addition of these two nanomaterials has also increased the compressive strength of the cement paste by approximately 26%.
