Synergistic optimization of thermoelectric performance in cementitious composites by lithium carbonate and carbon nanotubes

Abstract

Summary Thermoelectric cement‐based composite materials can convert the temperature difference between indoor and outdoor into electrical energy in summer. And the energy can be reversed to remove ice and snow on the pavement in winter. However, how to improve its thermoelectric conversion efficiency is the primary technical problem currently facing. Carbon nanotubes are often used as a container for their unique tubular structure. In this study, lithium acetate was filled in carbon nanotubes to obtain lithium carbonate modified carbon nanotubes (after heat treatment) by utilizing its capillary force. XRD, SEM, and TEM were used to characterize the morphology and crystal structure of lithium carbonate‐modified carbon nanotubes. ST2722‐SZ semiconductor powder resistivity tester was used to characterize the change of electrical conductivity before and after modification of carbon nanotubes (48.22 S/cm reduced to 3.43 S/cm, ∅11.28 mm, 30 MPa). The thermoelectric power factor of lithium carbonate modified carbon nanotubes reinforced cement‐based composites reaches 0.039 μW m−1 k−2. The Fermi level calculated by the Mott formula fluctuates between 0.116 and 0.256 eV. And the order of magnitude of the carrier concentration is stable at 1020 cm−3.The composite material not only exhibits superior thermoelectric properties but also reduces the carbon nanotube content to achieve a more cost‐effective purpose.

Thermoelectric Power Factor of Boron‐Doped Carbon Nanotubes Reinforced Cementitious Composites

“…The samples prepared with borondoped carbon nanotubes have the highest ZT value, 3.3 times the 5.0 wt% content of the samples prepared by the original CNTs. The higher ZT values of boron-doped CNTs cement matrix composites when the content of CNTs, [13,14,29] EG, [15,83] and reduced graphene oxide (RGO) [19] are 5.0 wt%. It is attributed to the enhanced Seebeck effect of samples when CNTs are doped with boron, while the thermal conductivity of expanded graphite and graphene is above that of CNTs, resulting in enhanced thermoelectric properties.…”

“…[10,11] Chung et al showed that the Seebeck coefficient of cement paste with the addition of 1.0 wt% steel fibers increased from 2.0-67.9 μV K À1 . [12] After 2011, nanoscale materials, as well as nanometal oxides, were added to cement-based materials such as CNTs, [13,14] expanded graphite(EG), [15,16] graphene nanosheets (GNP), [17][18][19][20][21] and metal oxides (e.g., Fe 2 O 3 , [22] ZnO) [2] to increase the thermoelectric properties.…”

“…It was shown that the Seebeck coefficient of the modified cement specimens increased, while the conductivity decreased. [ 14 ] In 2022, Wei's group proposed the pretreatment of CNTs with acid, which increased the Seebeck coefficient of cement specimens from 35–67 μV K −1 compared to pristine carbon nanotubes. The power factor increased by a factor of 2 after pretreatment.…”

Recent advances in thermoelectric technology to harvest energy from the pavement

“…In the literature reviewed above, most of the reports are centered on experiments and tests conducted on TEG because of TEG's excellent thermoelectric properties and low cost. Thermoelectric cementitious composites have even shown good thermoelectric properties as reported in recent years 104,105 . In particular, researchers in reducing the carbon content still maintain excellent thermoelectric properties for improving the mechanical properties of thermoelectric cement matrix 106,107 .…”

“…Thermoelectric cementitious composites have even shown good thermoelectric properties as reported in recent years. 104,105 In particular, researchers in reducing the carbon content still maintain excellent thermoelectric properties for improving the mechanical properties of thermoelectric cement matrix. 106,107 However, the practical application of thermoelectric cementitious composites is still in the exploratory stage.…”