In thermoelectricity,the inherent coupling between electrical conductivity and Seebeck coefficient represents a fundamental challenge in thermoelectric materials development.Herein,we present a unique pressure-tuning ...In thermoelectricity,the inherent coupling between electrical conductivity and Seebeck coefficient represents a fundamental challenge in thermoelectric materials development.Herein,we present a unique pressure-tuning strategy using compressible layered 2H-MoTe2,achieving an effective decoupling between the electrical conductivity and Seebeck coefficient.The applied pressure simultaneously induces two complementary effects:(1)bandgap reduction that moderately enhances carrier concentration to improve the electrical conductivity,and(2)band convergence that dramatically increases density-of-states effective mass to boost the Seebeck coefficient.This dual mechanism yields an extraordinary 18.5-fold enhancement in the average power factor.First-principles calculations and Boltzmann transport modeling precisely reproduce the experimental observations,validating this pressure-induced decoupling mechanism.The pressure-tuning mechanism provides a feasible and effective strategy for breaking through the optimization limits of the power factor,facilitating the design of high-performance thermoelectric materials.展开更多
To investigate the effects of pressure on the hot isostatic pressing(HIP) process of a stainless steel powder,density distribution and deformation of the powder at four different applied pressure levels were predicted...To investigate the effects of pressure on the hot isostatic pressing(HIP) process of a stainless steel powder,density distribution and deformation of the powder at four different applied pressure levels were predicted and compared by using finite element method(FEM).Constitutive relations of porous compacts during HIP process were derived based on the yield criterion of porous metal materials.Thermo-mechanical coupling calculations were carried out by the MSC.Marc.Densification mechanisms were studied through evolutions of relative density,equivalent plastic strain and equivalent viscoplastic strain rate for compacts.The simulation results were also compared with experimental data.The results show that the densification rate and final density of compacts increase dramatically with the increase in the applied pressure level when it is below 100 MPa during HIP process,and the creep for compacts evolves into steady stage with the improvement of density.展开更多
基金supported by the Science and Technology Development Project of Jilin Province(Grant No.SKL202402004)the Program for the Development of Science and Technology of Jilin Province(Grant No.YDZJ202201ZYTS308)+1 种基金the Open Research Fund of State Key Laboratory of Inorganic Synthesis and Preparative Chemistry,Jilin University(Grant Nos.202216 and 2022-23)the National Natural Science Foundation of China(Grant No.12350410372)。
文摘In thermoelectricity,the inherent coupling between electrical conductivity and Seebeck coefficient represents a fundamental challenge in thermoelectric materials development.Herein,we present a unique pressure-tuning strategy using compressible layered 2H-MoTe2,achieving an effective decoupling between the electrical conductivity and Seebeck coefficient.The applied pressure simultaneously induces two complementary effects:(1)bandgap reduction that moderately enhances carrier concentration to improve the electrical conductivity,and(2)band convergence that dramatically increases density-of-states effective mass to boost the Seebeck coefficient.This dual mechanism yields an extraordinary 18.5-fold enhancement in the average power factor.First-principles calculations and Boltzmann transport modeling precisely reproduce the experimental observations,validating this pressure-induced decoupling mechanism.The pressure-tuning mechanism provides a feasible and effective strategy for breaking through the optimization limits of the power factor,facilitating the design of high-performance thermoelectric materials.
基金Project(2007AA03Z115) supported by the National High Technology Research and Development Program of ChinaProject(2009ZX04005-041-03) supported by the National Science and Technology Major Program of ChinaProject(2010MS046) supported by the Independent Fund of Huazhong University of Science and Technology,China
文摘To investigate the effects of pressure on the hot isostatic pressing(HIP) process of a stainless steel powder,density distribution and deformation of the powder at four different applied pressure levels were predicted and compared by using finite element method(FEM).Constitutive relations of porous compacts during HIP process were derived based on the yield criterion of porous metal materials.Thermo-mechanical coupling calculations were carried out by the MSC.Marc.Densification mechanisms were studied through evolutions of relative density,equivalent plastic strain and equivalent viscoplastic strain rate for compacts.The simulation results were also compared with experimental data.The results show that the densification rate and final density of compacts increase dramatically with the increase in the applied pressure level when it is below 100 MPa during HIP process,and the creep for compacts evolves into steady stage with the improvement of density.
