冻融循环对膨胀石墨-硼掺杂碳纳米管/水泥复合材料热电性能的影响

Effect of freeze-thaw cycles on thermoelectric properties of expanded graphite-boron-doped carbon nanotubes/cement composites

  • 摘要: 利用温差发电的热电水泥基复合材料可以实现热能与电能的相互转换来降低城市环境温度和资源消耗,但热电转换效率过低及易受环境影响等问题制约了它的大规模应用。针对这个问题,本文提出了在高Seebeck系数的硼掺杂碳纳米管(Boron-doped carbon nanotubes,B-CNTs)基础上,添加高导电的膨胀石墨(Expanded graphite,EG),通过B-CNTs和EG多尺度混杂协同作用,整体提高水泥基复合材料的功率因数,相比于未添加膨胀石墨的水泥基复合材料功率因数提升了10倍,为1.49 μW·m−1·℃−2。冻融循环后的EG-B-CNTs/水泥复合材料导致孔隙率增加和水分的存在,引入了固-固、液-固等高密度缺陷界面,使载流子散射强度增加,出现水泥基复合材料冻融循环Seebeck系数强化现象。当冻融循环15次时,10.0wt%EG-5.0wt%B-CNTs/水泥复合材料功率因数为1.54 μW·m−1·℃−2。本文研究为改善热电水泥基复合材料性能及环境条件对于未来可行性应用提供了理论基础。

     

    Abstract: Thermoelectric cementitious composites using temperature difference power generation can realize the mutual conversion of thermal and electrical energy to reduce urban environmental temperature and resource consumption, but the low efficiency of thermoelectric conversion and vulnerability to environmental impact have restricted its large-scale application. To address this issue, this study proposes the addition of highly conductive expanded graphite (EG) to boron-doped carbon nanotubes (B-CNTs) with high Seebeck coefficients to improve the overall power factor of cementitious composites by the synergistic effect of multi-scale hybridization of B-CNTs and EG. The power factor of the cementitious composites was improved by 10 times to 1.49 μW·m−1·℃−2 compared with that of the cementitious composites without the addition of expanded graphite. The EG-B-CNTs/cement composites after freeze-thaw cycling result in increased porosity and the presence of moisture, which introduce high-density defect interfaces such as solid-solid and liquid-solid, resulting in an increase in carrier scattering intensity and an enhanced Seebeck coefficient for freeze-thaw cycling of cement matrix composites. The power factor of 10.0wt%EG-5.0wt%B-CNTs/cement composite is 1.54 μW·m−1·℃−2 when freeze-thaw cycles are performed 15 times. The research in this paper provides a theoretical basis for improving the performance and environmental conditions of thermoelectric cement matrix composites for future viable applications.

     

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