Thermoelectric properties of topological insulators have traditionally been examined in the context of their metallic surface states.However,recent studies have begun to unveil intriguing thermoelectric effects emergi...Thermoelectric properties of topological insulators have traditionally been examined in the context of their metallic surface states.However,recent studies have begun to unveil intriguing thermoelectric effects emerging from the bulk electronic states of topological insulators,which have largely been overlooked in the past.Charge transport phenomena through the bulk are especially important under typical operating conditions of thermoelectric devices,necessitating a comprehensive review of both surface and bulk transport in topological insulators.Here,we review thermoelectric properties that are uniquely observed in topological insulators,placing special emphasis on unconventional phenomena emerging from bulk states.We demonstrate that unusual thermoelectric effects arising from bulk states,such as band inversion-driven warping,can be discerned in experiments through a simple analysis of the weighted mobility.We believe that there is still plenty to uncover within the bulk of topological insulators,yet our current understanding can already inspire new strategies for designing and discovering new materials for next-generation thermoelectrics.展开更多
Residual stress is inevitable in epoxy insulators,which easily leads to small cracks and even insulation breakdown during the operation of gas-insulated transmission line(GIL)/gas-insulated switchgear(GIS).This study ...Residual stress is inevitable in epoxy insulators,which easily leads to small cracks and even insulation breakdown during the operation of gas-insulated transmission line(GIL)/gas-insulated switchgear(GIS).This study proposes a nondestructive method to measure the residual stress on epoxy insulators using thermoelastic effects.First,the laser-induced temperature rise of the epoxy/Al_(2)O_(3) composite was measured under different mechanical stresses to establish a relationship between the relative temperature rise and mechanical stress.Then,the residual stress distributions on full-sized insulators were reconstructed based on the stress-temperature relationship by scanning and measuring the relative temperature rise values at distributed points.The results show that the temperature rise of the epoxy/Al_(2)O_(3) composite is promoted by tensile stress but inhibited by compressive stress,reflecting the impacts of mechanical stress on the thermal properties of epoxy insulators.Compressive stress is present on the outer side,whereas tensile stress is concentrated on the inner side of both basin-type and tri-post insulators,with maximum values around 30 MPa.During curing,a higher temperature on the outer side of the mould leads to a faster curing rate of the insulator than on the inner side.This,combined with the mismatch of thermal expansion coefficients between epoxy and aluminium,contributes to the generation of residual stress.The measurement results of residual stress are consistent with the theoretical analysis results,verifying the effectiveness of the proposed method and offering new insights into the measurement of residual stress.展开更多
基金funded by the US Department of Energy through the Computational Science Graduate Fellowship(DOE CSGF)under grant number DE-SC0020347.M.Y.Tsupport from the Johannes and Julia Randall Weertman Graduate Fellowshipsupport of award 70NANB19H005 from the US Department of Commerce,National Institute of Standards and Technology,as part of the Center for Hierarchical Materials Design(CHiMaD).
文摘Thermoelectric properties of topological insulators have traditionally been examined in the context of their metallic surface states.However,recent studies have begun to unveil intriguing thermoelectric effects emerging from the bulk electronic states of topological insulators,which have largely been overlooked in the past.Charge transport phenomena through the bulk are especially important under typical operating conditions of thermoelectric devices,necessitating a comprehensive review of both surface and bulk transport in topological insulators.Here,we review thermoelectric properties that are uniquely observed in topological insulators,placing special emphasis on unconventional phenomena emerging from bulk states.We demonstrate that unusual thermoelectric effects arising from bulk states,such as band inversion-driven warping,can be discerned in experiments through a simple analysis of the weighted mobility.We believe that there is still plenty to uncover within the bulk of topological insulators,yet our current understanding can already inspire new strategies for designing and discovering new materials for next-generation thermoelectrics.
基金supported by the National Natural Science Foundation of China(Grant Nos.52220105002 and 52307181)the Smart Gird-National Science and Technology Major Project(Grant No.2024ZD0802403).
文摘Residual stress is inevitable in epoxy insulators,which easily leads to small cracks and even insulation breakdown during the operation of gas-insulated transmission line(GIL)/gas-insulated switchgear(GIS).This study proposes a nondestructive method to measure the residual stress on epoxy insulators using thermoelastic effects.First,the laser-induced temperature rise of the epoxy/Al_(2)O_(3) composite was measured under different mechanical stresses to establish a relationship between the relative temperature rise and mechanical stress.Then,the residual stress distributions on full-sized insulators were reconstructed based on the stress-temperature relationship by scanning and measuring the relative temperature rise values at distributed points.The results show that the temperature rise of the epoxy/Al_(2)O_(3) composite is promoted by tensile stress but inhibited by compressive stress,reflecting the impacts of mechanical stress on the thermal properties of epoxy insulators.Compressive stress is present on the outer side,whereas tensile stress is concentrated on the inner side of both basin-type and tri-post insulators,with maximum values around 30 MPa.During curing,a higher temperature on the outer side of the mould leads to a faster curing rate of the insulator than on the inner side.This,combined with the mismatch of thermal expansion coefficients between epoxy and aluminium,contributes to the generation of residual stress.The measurement results of residual stress are consistent with the theoretical analysis results,verifying the effectiveness of the proposed method and offering new insights into the measurement of residual stress.
