| Thermoelectric cement based composite material is an intelligent building material that can convert thermal energy into electrical energy.It can realize the reuse of urban waste heat and waste heat and reduce the heat island effect of the city.Thermoelectric cement materials in normal service environment are bound to be affected by environmental loads,affect the thermoelectric properties of materials,and the influence of environmental loads on the thermoelectric properties of cement-based materials is of great significance for promoting the development and application of thermoelectric cement-based materials.In this paper,Expanded Graphite/Carbom Fiber Reinforced Cement-based Composites?EGCFRC?was prepared firstly,and the influence law for stress,fatigue loading,freeze-thaw cycling load and low temperature cycling load on EGCFRC conductivity???,Seebeck coefficient?S?,power factor?PF?and thermoelectric value?ZT?were studied,and clarify the environmental factors on the thermoelectric performance of the mechanism,studied the law of influence of freeze-thaw cycles on[Bmim]Br-EGCFRC thermoelectric properties.The main contents are as follows:?1?The thermoelectric properties of EGCFRC under different stress?0,1.0,2.0,3.0,4.0 MPa?were studied.The results show that the electrical conductivity of EGCFRC gradually increases and the absolute value of Seebeck coefficient decreases as the stress increases.At 30?,the stress-free EGCFRC has the lowest conductivity,about 1.06×10-3 S/cm,and the Seebeck absolute value is 79.98?V/?.At a stress of 4.0MPa,the density of the material increases,With the decrease of the solid interface and the increase of the carrier mobility,the electrical conductivity increased to 5.48 S/cm,and the Seebeck system's absolute value decreased to 4.87?V/?.In addition,with the increase of stress,the overall value of its thermoelectric properties shows an overall decrease,then increases and then decreases.When the stress is 4.0 MPa,the thermoelectric value of the sample reaches the minimum,which is about 1.72×10-10,which is reduced by 3 orders of magnitude compared with no stress.?2?The effects of different fatigue times?0,2500,5000,7500 and 10000 times?on their thermoelectric performance at different fatigue loading levels?1.0,1.5 and 1.8 kN?were studied.The results show that with the increase of fatigue times,the porosity of the material increases,the compressive strength decreases,and the microcracks increase.In terms of electrical conductivity,fatigue load will reduce the electrical conductivity of the material.The greater the fatigue load,the more fatigue times are performed and the more obvious the electrical conductivity of the material decreases.When the fatigue load was 1.5 kN,the electrical conductivity of the sample decreased from 2.06×10-3S/cm to 0.73×10-3 S/cm after 10,000 fatigue loads at 30?.In terms of the influence on the Seebeck coefficient,when the fatigue load is fixed,the absolute value of the Seebeck coefficient of the EGCFRC increases first and then decreases with the increase of the fatigue times.When the number of fatigue is 2,500,the absolute value of the Seebeck coefficient of the material is the largest.About 43.88?V/?.?3?The influence of freeze-thaw cycles from-30 to 95??cycles of 0,10,20,30,40 and 50 times respectively?on the thermoelectric properties of EGCFRC and[Bmim]Br-EGCFRC was studied.The results show that the freeze-thaw cycle load will reduce the thermoelectric effect of EGCFRC.With the increase of freeze-thaw cycles,the absolute value of the conductivity,Seebeck coefficient,and thermoelectric value of the material decrease.At 80?,the thermoelectric value of EGCFEC after 50freeze-thaw cycles decreased from 8.40×10-8 to 7.40×10-11,which was reduced by about3 orders of magnitude.The absolute value of the Seebeck coefficient of[Bmim]Br-EGCFRC increases first and then decreases with the increase of the number of freeze-thaw cycle loads.The absolute value of Seebeck coefficient of[Bmim]Br-EGCFRC is maximized after 10 freeze-thaw cycles.Value?745.69?V/??.The conductivity of[Bmim]Br-EGCFRC gradually decreased as the number of freeze-thaw cycles gradually increased.After 50 freeze-thaw cycles,the conductivity decreased from 3.15×10-3 S/cm to 2.47×10-3 S/cm.?4?The initial process of low-temperature cyclic loading?-30?to room temperature,cycle times 0-4 times?was studied to investigate the effect of EGCFRC on thermoelectric properties.The results show that the effect of low temperature cyclic loading will increase the number of micro-cracks inside the material,increase its activation energy and carrier concentration,reduce the mobility of carriers,and decrease the absolute value of the conductivity and Seebeck coefficient of the material[1].At30?,the electrical conductivity of EGCFRC decreased from 2.16×10-3 S/cm to1.11×10-3 S/cm after four cycles of low temperature cycling,and the absolute value of Seebeck coefficient decreased from 33.30?V/?to 10.87?V/?;At the same time,the role of low-temperature cyclic load also makes the material's thermoelectric value continuously decreases.After four times of low-temperature cyclic loading,the thermoelectric value of EGCFRC decreases from 7.51×10-8 to 0.40×10-8. |
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