| Thermoelectric cement-based composites have wide application space in the road field because of their unique thermoelectric properties.They can convert low-grade heat energy in the road surface into electric energy,and have the advantages of strong mechanical properties,no pollution and low cost.However,there are still the following problems when it is applied to the road:（1）the concrete practical structure in the road is insufficient;（2）the efficiency of thermoelectric conversion is low.In view of the above problems,Carbon Nanotubes（CNTs）cement-based composites and Expanded Graphite（EG）-CNTs cement-based composites were prepared in this paper,and the thermoelectric properties such as microstructure,electrical conductivity,Seebeck coefficient and power factor were investigated.A cement-based thermoelectric conversion module and a cement-based thermoelectric material combined road energy collection system were prepared,and their energy collection properties such as output voltage and output power were studied.The main work contents are as follows:EG-CNTs/cement composites were prepared by semi-dry pressing process,and the effects of different contents of CNTs（5.0wt%,10.0wt%,15.0wt%）and EG（3.0wt%,5.0wt%,7.0wt%）on their thermoelectric properties were studied.The results showed that the electrical conductivity of cement-based CNTs composites increased with the increase of CNTs content,while the Seebeck coefficient first increased and then decreased with the increase of CNTs content,which was mainly due to the high carrier concentration caused by excessive CNTs content.Cement-based composites with CNTs content of10.0wt%have excellent thermoelectric properties,with the highest conductivity of 0.45S/cm,the highest absolute value of Seebeck coefficient of 14.19μV/K,and the highest power factor of 5.6×10-3μWm-1K-2.The content of CNTs was fixed at 10.0wt%,and the thermoelectric properties of cement-based composites with EG-CNTs were studied.The thermoelectric properties increased with the increase of EG content.The maximum conductivity,absolute value of Seebeck coefficient and power factor of the cement-based composite of 7.0wt%EG-CNTs were 0.6 S/cm,29.89μV/K and 4.6×10-2μWm-1K-2,respectively.The multi-scale hybrid of one-dimensional nanoscale CNTs and micron scale EG enables the establishment of a good conductive network and strengthens the thermoelectric properties of cement-based composites.Cement-based single thermoelectric conversion module and cement-based combined thermoelectric conversion module were prepared by cement-based composite materials with EG-CNTs.The influence of distribution array of single thermoelectric conversion modules（3×1,2×1×2,3×3×3）on the performance of combined thermoelectric conversion module was studied,and the longitudinal temperature gradient inside the asphalt and cement concrete road structures simulated under indoor and outdoor environmental conditions was studied The results showed that the output voltage and output power of cement-based composite thermoelectric conversion module increase with the increase of the number of single thermoelectric conversion modules in series.The cement-based composite thermoelectric conversion module with 3×3×3 distribution array has excellent thermoelectric performance,and the absolute value of Seebeck coefficient is up to 96.95μV/K,which is 2.2 times of that of 3×1 distribution array,2.3 times of2×1×2 distributed array;the maximum output power is 4.7×10-4μW,which is 4.4 times that of 3×1 distributed array and 2.9 times that of 2×1×2 distributed array;the maximum output voltage is 153.25μV,which is 2.61 times of that of 3×1 distribution array and 1.58times of that of 2×1×2 distribution array.The power factor is up to 9.1×10-5μWm-1K-2.The overall heating rate of simulated asphalt concrete roads under indoor and outdoor environmental conditions is relatively fast,and the temperature gradient in the deep structure of the road is large.A road energy collection system based on cement-based thermoelectric conversion module-TEG（Thermoelectric Generator）was prepared,and its energy collection performance such as output voltage and output power was studied.The results show that the performance of cement-based thermoelectric conversion module-TEG combined road energy collection system is significantly improved compared with cement-based thermoelectric conversion module,and its output power is up to 0.002 W.The Seebeck coefficient absolute value,output power,output voltage and power factor of cement-based thermoelectric conversion module are up to 182.16μV/K,6.1×10-4μW,156.1μV,8.3×10-4μWm-1K-2,respectively.The output voltage of TEG system increases first and then decreases with the increase of time,and the maximum voltage reaches 0.226 V at 2h.The cement-based thermoelectric conversion module-TEG combined road energy collection system was simulated and applied to the road environment of 10 m width and1000 m length,and about 8.8×106 J of electricity was collected within 24 h,equivalent to2.5 k Wh. |
PDF Full Text Request