Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the mo...Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the modification treatment,the room-temperature tensile strength of the alloy remains nearly unchanged,the elongation at break slightly increases from 1.82%to 3.34%,and the electrical conductivity significantly increases from 40.1%international annealed copper standard(IACS)to 42.0%IACS.After the modification,the alloy was subjected to solid solution treatment at 515℃for 8 h,followed by aging treatment at 180,200,220 and 240℃for 6 h.With increasing aging temperature,the electrical conductivity increases monotonously from 41.4%IACS to 45.5%IACS,while the room-temperature tensile strength initially increases and then decreases.At 200℃,the alloy achieves an optimal balance between electrical conductivity and room-temperature tensile strength:the electrical conductivity is 42.5%IACS,and the room-temperature tensile strength is 282.9 MPa.When the aging temperature continues to rise,the alloy undergoes overaging.Although the conductivity continues to increase,the room-temperature tensile strength drops sharply,and it is only 177.1 MPa at 240℃.展开更多
Compared with Cu/Al_(2)O_(3)composites,high-strength Cu/Al_(2)O_(3)composites usually exhibit obviously deteriorated electrical conductivity.A chemical and mechanical alloying-based strategy was adopted to fabricate u...Compared with Cu/Al_(2)O_(3)composites,high-strength Cu/Al_(2)O_(3)composites usually exhibit obviously deteriorated electrical conductivity.A chemical and mechanical alloying-based strategy was adopted to fabricate ultrafine composite powders with lowcontent reinforcement and constructed a combined structure of Cu ultrafine powders covered with in-situ Al_(2)O_(3)nanoparticles.After consolidation at a relatively lower sintering temperature of 550℃,high-volume-fraction ultrafine grains were introduced into the Cu/Al_(2)O_(3)composite,and many in-situ Al_(2)O_(3)nanoparticles with an average size of 11.7±7.5 nm were dispersed homogeneously in the Cu grain.Results show that the composite demonstrates an excellent balance of high tensile strength(654±1 MPa)and high electrical conductivity(84.5±0.1%IACS),which is ascribed to the synergistic strengthening effect of ultrafine grains,dislocations,and in-situ Al_(2)O_(3)nanoparticles.This approach,which utilizes ultrafine composite powder with low-content reinforcement as a precursor and employs low-temperature and high-pressure sintering subsequently,may hold promising potential for large-scale industrial production of high-performance oxide dispersion strengthened alloys.展开更多
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
The effects of forward extrusion as well as extrusion combined with reversible torsion(KoBo extrusion),followed by additional deformation via the MaxStrain module of the Gleeble thermomechanical simulator,on the micro...The effects of forward extrusion as well as extrusion combined with reversible torsion(KoBo extrusion),followed by additional deformation via the MaxStrain module of the Gleeble thermomechanical simulator,on the microstructure,mechanical properties,and electrical conductivity of a Cu−0.7Mg(wt.%)alloy,were investigated.The simulation results highlighted the critical influence of processing history on determining the equivalent strain distribution.The sample subjected to forward extrusion at 400℃and subsequent MaxStrain processing(FM sample),possessed 76%lower grain size compared to the sample processed solely with MaxStrain(AM sample).Likewise,the KoBo-extruded and MaxStrain-processed sample(KM sample)exhibited 66%smaller grain size compared to the AM sample.Tensile test results revealed that the AM,FM,and KM samples,respectively,possessed 251%,288%,and 360%higher yield strength,and 95%,121%,and 169%higher tensile strength compared to the initial annealed alloy,as a result of grain refinement as well as deformation strengthening.Finally,the electrical conductivity measurements revealed that AM,FM,and KM samples,respectively,possessed electrical conductivity values of 37.9,35.6,and 32.0 MS/m,which,by considering their mechanical properties,makes them eligible to be categorized as high-strength and high-conductivity copper alloys.展开更多
The effects of drawing strain during intermediate annealing on the microstructure and properties of Cu-20 wt%Fe alloy wires while maintaining constant total deformation were investigated.Intermediate annealing effecti...The effects of drawing strain during intermediate annealing on the microstructure and properties of Cu-20 wt%Fe alloy wires while maintaining constant total deformation were investigated.Intermediate annealing effectively removes work hardening in both the Cu matrix and Fe fibers,restoring their plastic deformation capacity and preserving fiber continuity during subsequent redrawing.The process also refines the Fe phase,leading to a more uniform size distribution and straighter,better-aligned Cu/Fe phase interfaces,thereby enhancing the comprehensive properties of the alloy.The magnitude of drawing strain during intermediate annealing plays a critical role in balancing the mechanical strength and electrical conductivity of redrawn wires.A lower initial drawing strain requires greater redrawing strain,leading to excessive hardening of the Fe fibers,which negatively impacts the electrical conductivity and tensile plasticity.Conversely,a higher initial drawing strain can result in insufficient work hardening during the redrawing deformation process,yielding minimal strength improvements.Among the tested alloys,H/3.5 wires show a slight reduction in strength and hardness compared to W and H/4.5 wires but exhibit a significant increase in tensile elongation and electrical conductivity.The tensile strength was 755 MPa,and the electrical conductivity was 47%international-annealed copper standard(IACS).The optimal performance is attributed to the formation of a high-density,ultrafine Fe fiber structure-aligned parallel to the drawing direction,which is achieved through a suitable combination of the drawing process and intermediate annealing.展开更多
Magnesium(Mg)alloys offer significant potential for conductive applications,thanks to their distinctive attributes,including high specific strength,excellent electrical conductivity(EC),low density,electromagnetic int...Magnesium(Mg)alloys offer significant potential for conductive applications,thanks to their distinctive attributes,including high specific strength,excellent electrical conductivity(EC),low density,electromagnetic interference shielding effectiveness(EMI SE),and recyclability.However,a major challenge in Mg alloy research is balancing high strength with good EC,as strengthening these alloys often compromises their EC.This paper offers an in-depth analysis of the mechanisms,strategies,and applications aimed at improving the EC of Mg alloys.A bibliometric study is performed to uncover the main research trends and emerging hotspots within the field.The review then examines various strategies to improve EC focusing on factors such as solute elements,second phases,grain boundaries,textures,and vacancies.By carefully controlling alloy composition and optimizing heat treatment processes,significant advancements have been achieved by researchers in developing Mg alloys that possess both high strength and high EC,especially in Mg-Al,Mg-Zn,Mg-RE alloy systems and composites.Finally,the paper outlines future research directions,stressing the importance of further exploration into alloying element selection,heat treatment optimization,and other advanced strategies.These efforts are crucial for overcoming current challenges and expanding the application of Mg alloys in EC fields.展开更多
Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electric...Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electrical conductivity and mechanical properties of Al-Mg-Si alloy simultaneously,the rare earth La was introduced to modify the Al-Mg-Si alloy.The effect of La addition on the microstructure,tensile properties and electrical conductivity of cast Al-Mg-Si alloy was investigated systematically.Results indicate that the appropriate La content is helpful to improve the strength and electrical conductivity of Al-Mg-Si alloys.When the addition of La is 0.2wt.%,theα-Al grains are refined apparently,Mg and Si solute atoms in the Al matrix are reduced by the formation of Mg_(2)Si phase;the distribution of Al_(11)La_(3)phases is uniform,and the morphology of AlFeSi phase transforms from continuous state to discontinuous state.The Al-Mg-Si-0.2La alloy exhibits the optimal tensile properties and electrical conductivity,with an ultimate tensile strength of 170 MPa,a yield strength of 88 MPa,an elongation of 18.9%,and an electrical conductivity of 44.0%IACS.These values represent improvements of 9.0%,15.8%,70.3%,and 17.3%,respectively,compared to the Al-Mg-Si alloy without La addition.However,excessive La deteriorates the properties of Al-Mg-Si-xLa alloys.展开更多
Immiscible bimetal systems,of which tungsten–copper(W–Cu)is a typical representative,have crucial applications in fields requiring both mechanical and physical properties.Nevertheless,it is a major challenge to dete...Immiscible bimetal systems,of which tungsten–copper(W–Cu)is a typical representative,have crucial applications in fields requiring both mechanical and physical properties.Nevertheless,it is a major challenge to determine how to give full play to the advantages of the two phases of the bimetal and achieve outstanding comprehensive properties.In this study,an ultrafine-grained W–Cu bimetal with spatially connected Cu and specific Wislands was fabricated through a designed powder-mixing process and subsequent rapid low-temperature sintering.The prepared bimetal concurrently has a high yield strength,large plastic strain,and high electrical conductivity.The stress distribution and strain response of individual phases in different types of W–Cu bimetals under loading were quantified by means of a simulation.The high yield strength of the reported bimetal results from the microstructure refinement and high contiguity of the grains in the W islands,which enhance the contribution of W to the total plastic deformation of the bimetal.The high electrical conductivity is attributed to the increased mean free path of the Cu and the reduced proportion of phase boundaries due to the specific phase combination of W islands and Cu.This work provides new insight into modulating phase configuration in immiscible metallic composites to achieve high-level multi-objective properties.展开更多
The deformation of Cu–20 wt.%Fe alloy wires leads to a significant improvement in mechanical properties and a decrease in electrical conductivity.Simultaneous improvements in strength and conductivity were achieved b...The deformation of Cu–20 wt.%Fe alloy wires leads to a significant improvement in mechanical properties and a decrease in electrical conductivity.Simultaneous improvements in strength and conductivity were achieved by intermediate annealing of drawn Cu–20 wt.%Fe wires.As the annealing temperature increased,the strength of Cu–20 wt.%Fe alloy wire decreased monotonically,but the electrical conductivity first increased and then decreased,reaching its peak value after annealing at 500℃.The decrease in strength is related to dislocation recovery and static recrystallization of Cu and Fe phases,and the increase in electrical conductivity mainly results from the aging precipitation of solid solution Fe.After annealing at 500℃,there was no obvious recrystallization of Cu phase,and many of the nano-Fe particles precipitated from Cu matrix.An annealing temperature of 600℃ induced the recrystallization of Cu matrix and an increase in Fe solid solubility,resulting in a decrease in strength and electrical conductivity.Subsequently,the wires annealed at 500℃ were drawn to 2 mm.Compared with those of the continuously drawn Cu–20 wt.%Fe alloy wires,the deformation ability,strength,and electrical conductivity of Cu–20 wt.%Fe alloy wires subjected to intermediate annealing treatment are significantly greater.This is mainly related to the sufficient precipitation of Fe in Cu matrix and the strengthening of refined Fe fibers parallel to the drawing direction.展开更多
High-performance Ti_(3)C_(2)T_(x)fibers have garnered significant potential for smart fibers enabled fabrics.Nonetheless,a major challenge hindering their widespread use is the lack of strong interlayer interactions b...High-performance Ti_(3)C_(2)T_(x)fibers have garnered significant potential for smart fibers enabled fabrics.Nonetheless,a major challenge hindering their widespread use is the lack of strong interlayer interactions between Ti_(3)C_(2)T_(x)nanosheets within fibers,which restricts their properties.Herein,a versatile strategy is proposed to construct wet-spun Ti_(3)C_(2)T_(x)fibers,in which trace amounts of borate form strong interlayer crosslinking between Ti_(3)C_(2)T_(x)nanosheets to significantly enhance interactions as supported by density functional theory calculations,thereby reducing interlayer spacing,diminishing microscopic voids and promoting orientation of the nanosheets.The resultant Ti_(3)C_(2)T_(x)fibers exhibit exceptional electrical conductivity of 7781 S cm^(-1)and mechanical properties,including tensile strength of 188.72 MPa and Young's modulus of 52.42 GPa.Notably,employing equilibrium molecular dynamics simulations,finite element analysis,and cross-wire geometry method,it is revealed that such crosslinking also effectively lowers interfacial thermal resistance and ultimately elevates thermal conductivity of Ti_(3)C_(2)T_(x)fibers to 13 W m^(-1)K^(-1),marking the first systematic study on thermal conductivity of Ti_(3)C_(2)T_(x)fibers.The simple and efficient interlayer crosslinking enhancement strategy not only enables the construction of thermal conductivity Ti_(3)C_(2)T_(x)fibers with high electrical conductivity for smart textiles,but also offers a scalable approach for assembling other nanomaterials into multifunctional fibers.展开更多
The mechanism of seeded precipitation of sodium aluminate solution was studied by measuring the seeded-precipitation rate and electrical conductivity online, as well as calculating the activity and fraction of ion pai...The mechanism of seeded precipitation of sodium aluminate solution was studied by measuring the seeded-precipitation rate and electrical conductivity online, as well as calculating the activity and fraction of ion pair. The results show that the electrical conductivity of sodium aluminate slurry linearly decreases with increasing aluminum hydroxide addition. Moreover, both the electrical conductivity of slurry and the difference in electrical conductivity between sodium aluminate solution and slurry remarkably decline in the first 60 min before gradually increasing in the preliminary 10 h and finally reaching almost the same level after 10 h. In low Na2 O concentration solution the activities of Na OH and Na Al（OH）4 in seeded precipitation are high, which can enlarge the difference in conductivity between slurry and solution. Additionally, more ion pairs exist in solution in preliminary seeded precipitation, and the adsorption of Na＋Al（OH）4- on seed surface is likely to break the equilibrium of ion pair formation and to decrease the difference in conductivity in preliminary seeded precipitation.展开更多
The electrical conductivity of NaF-AlF3-CaF2-Al2O3-ZrO2 system was studied by a tube-type cell with fixed cell constant. The results show that the electrical conductivity of NaF-AlF3-3%Al2O3-3%CaF2-ZrO2 molten salt sy...The electrical conductivity of NaF-AlF3-CaF2-Al2O3-ZrO2 system was studied by a tube-type cell with fixed cell constant. The results show that the electrical conductivity of NaF-AlF3-3%Al2O3-3%CaF2-ZrO2 molten salt system decreases with increase of ZrO2 content in an interval of 0-5%. The increase of 1%ZrO2 results in a corresponding electrical conductivity decrease of 0.02 S/cm, and the equivalent conductivity increases with the increase of molar ratio of NaF to AlF3. When the temperature increases by 1 °C, the electrical conductivity increases by 0.004 S/cm. At last, the regression equations of electrical conductivity relative to temperature and ZrO2 are obtained by quadratic regression analysis.展开更多
CuCrZr alloys were treated with the thermal stretch process at various temperatures from 100 to 300℃.The results reveal that the thermal stretch process is successfully developed to manufacture the precipitation hard...CuCrZr alloys were treated with the thermal stretch process at various temperatures from 100 to 300℃.The results reveal that the thermal stretch process is successfully developed to manufacture the precipitation hardening CuCrZr alloys with a good combination of microhardness and electrical conductivity.By increasing the tensile elongations at each temperature from 100 to 300℃,the microhardness increases whereas the electrical conductivity decreases slightly.Cr-containing precipitate phases with a Nishiyama-Wasserman orientation relationship to the copper matrix were observed by TEM.The achievement of high micro-hardness and acceptable electrical conductivity in the thermal stretch treated alloys is ascribed to the interactions of the heteroatom solution,dislocation increment,grain refinement and dispersive precipitation effect.展开更多
The ambient electrical conductivity (AEC) of carbon cathode materials was investigated in respect to their open porosity, crystal structure and graphite content using hydrostatic method, four-probe technique and X-ray...The ambient electrical conductivity (AEC) of carbon cathode materials was investigated in respect to their open porosity, crystal structure and graphite content using hydrostatic method, four-probe technique and X-ray diffraction (XRD), respectively. The AEC is proportional to the specific conductivity (σ0) and the exponential of (1?ε) (ε is porosity) by a quasi-uniform formula based on the percolation theory. Theσ0 can reflect the intrinsic conductivity of the carbon cathodes free of pores, and it depends on the mean crystallite size parallel to the layer (002). The exponentn is dependent on the materials nature of the cathode aggregates, while an averaged value, 4.65, can practically work well with 5 types of cathode materials. The calculation ofσ0 can be extended to the graphitic cathodes containing different aggregates using the simple rule of mixture.展开更多
As a fundamental study on recovery of valuable metals from nonferrous metallurgical slags,electrical conductivity values of MO（MO=FeO,NiO）-containing CaO-MgO-SiO2-Al2O3 slag with a low basicity were measured at diff...As a fundamental study on recovery of valuable metals from nonferrous metallurgical slags,electrical conductivity values of MO（MO=FeO,NiO）-containing CaO-MgO-SiO2-Al2O3 slag with a low basicity were measured at different temperatures using AC impedance spectroscopy.The result shows that the electrical conductivity increased from 1.4 S/m to 14.4 S/m with the increase of the temperature from 1 573 to 1 773 K and the content of MO which is less than 12% under the constant mass ratio of （CaO＋MgO） to （SiO2＋Al2O3） of 0.47.Moreover,the increase magnitude of the electrical conductivity was also promoted with the increase of the content of MO.The electrical conductivity of FeO-containing slags was close to that of NiO-containing slags when the content was less than 8%;however,it was obviously larger than that of NiO-containing slags when the content was 12%.The activation energy of the electrical conductivity decreased with the increase of MO content.展开更多
The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electri...The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.展开更多
Electrical conductivity of molten binary and ternary mixtures based on the system NaF-AlF3-SiO2 was investigated by means of a tube–cell （made of pyrolytic boron nitride） with stationary electrodes. Viscosity of th...Electrical conductivity of molten binary and ternary mixtures based on the system NaF-AlF3-SiO2 was investigated by means of a tube–cell （made of pyrolytic boron nitride） with stationary electrodes. Viscosity of the binary system Na3AlF6-SiO2 was measured by computerized torsion pendulum method. It was found that conductivity and viscosity varied linearly with temperature in all investigated mixtures. Obtained content dependence of electrical conductivity （isotherms） was divided into two parts. First, one represented the content region up to 10%（mole fraction） of SiO2;second, the region was with a higher content of SiO2 （from 10%up to 40%）. While the conductivity considerably decreased with content of SiO2 in the second part; it surprisingly rose in the low content range. A small addition of SiO2 to the molten cryolite （up to 10%） could slightly increase viscosity, but had no influence on the slope of this dependence since it is responsible for a glassy-networks formation in the melt. Further addition of SiO2 to the molten cryolite had a huge effect on the viscosity.展开更多
The electrical conductivity （EC） of 1：5 soil-water extract （EC1：5） was studied utilizing path coefficient analysis. The study focused on revealing the main chemical factors contributing to EC of soil extracts an...The electrical conductivity （EC） of 1：5 soil-water extract （EC1：5） was studied utilizing path coefficient analysis. The study focused on revealing the main chemical factors contributing to EC of soil extracts and their relative importance. Results showed that the most important factors influencing the EC1：5 of coastal salt-affected soils were the concentration of salt in 1：5 soil-water extract （So）, Cl^-, and the sodium adsorption ratio （SAR）, while effects of pH, CO3^2-, HCO3^, soluble sodium percentage （SSP）, and sodium dianion ratio （SDR） were very weak. Though the direct path coefficients between EC1：5 and SO4^2- , Ca^2＋, Mg^2＋, K^＋, or Na^＋ were not high, influence of other chemical factors caused the coefficients to increase, making the summation of their direct and indirect path coefficients relatively high. Evidences showed that multiple regression relations between EC1：5 and most of the primary factors （So, Cl^-, and SAR） had sound reliability and very good accuracy.展开更多
The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,th...The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,the precipitation of Cr at nanometer scale provided further strengthening and brought substantial recovery of electrical conductivity.The aged nanostructured CuCrZr alloy exhibited a high tensile strength of 832MPa and a high electrical conductivity of 71.2%IACS.The details of precipitation tuned by nanotwin boundaries were demonstrated in this work.The combined strengthening of nanostructures and nanoprecipitates was discussed.展开更多
The effect of rare earth element Ce on mechanical performance and electrical conductivity of aluminum rod for electrical purpose were studied under industrial production condition. Using optical microscope, SEM, TEM, ...The effect of rare earth element Ce on mechanical performance and electrical conductivity of aluminum rod for electrical purpose were studied under industrial production condition. Using optical microscope, SEM, TEM, EDS and X-ray diffractometer, the microstructure and phase composition of aluminum rod were measured and analyzed. The results indicate that the content of rare earth element Ce is between 0.05% -0.16% in the aluminum rod for electrical purpose. Its tensile strength is enhanced to some extent. The research also discovers that the tensile strength is enhanced remarkably with impurity element Si content increases. Because influence of Si is big to the conductivity, the Si content should be controlled continuously strictly in the aluminum for electrical purpose. Adding rare earth element Ce reduces the solid solubility of Si in the aluminum matrix, and the negative effect of Si on the aluminum conductor reduces effectively. So the limit of in Si content in aluminum rod for electrical purpose can be relaxed moderately.展开更多
基金Applied Basic Research Program of Liaoning Province(CN)(2022JH2/101300078)。
文摘Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the modification treatment,the room-temperature tensile strength of the alloy remains nearly unchanged,the elongation at break slightly increases from 1.82%to 3.34%,and the electrical conductivity significantly increases from 40.1%international annealed copper standard(IACS)to 42.0%IACS.After the modification,the alloy was subjected to solid solution treatment at 515℃for 8 h,followed by aging treatment at 180,200,220 and 240℃for 6 h.With increasing aging temperature,the electrical conductivity increases monotonously from 41.4%IACS to 45.5%IACS,while the room-temperature tensile strength initially increases and then decreases.At 200℃,the alloy achieves an optimal balance between electrical conductivity and room-temperature tensile strength:the electrical conductivity is 42.5%IACS,and the room-temperature tensile strength is 282.9 MPa.When the aging temperature continues to rise,the alloy undergoes overaging.Although the conductivity continues to increase,the room-temperature tensile strength drops sharply,and it is only 177.1 MPa at 240℃.
基金Foundation of Northwest Institute for Non-ferrous Metal Research(YK2020-9,ZZXJ2203)Capital Projects of Financial Department of Shaanxi Province(YK22C-12)+4 种基金National Natural Science Foundation of China(62204207)Innovation Capability Support Plan in Shaanxi Province of China(2022KJXX-82,2023KJXX-083)Natural Science Foundation of Shaanxi Province(2022JQ-332)Shaanxi Innovative Research Team for Key Science and Technology(2023-CX-TD-46)Key Research and Development Projects of Shaanxi Province(2024GX-YBXM-351)。
文摘Compared with Cu/Al_(2)O_(3)composites,high-strength Cu/Al_(2)O_(3)composites usually exhibit obviously deteriorated electrical conductivity.A chemical and mechanical alloying-based strategy was adopted to fabricate ultrafine composite powders with lowcontent reinforcement and constructed a combined structure of Cu ultrafine powders covered with in-situ Al_(2)O_(3)nanoparticles.After consolidation at a relatively lower sintering temperature of 550℃,high-volume-fraction ultrafine grains were introduced into the Cu/Al_(2)O_(3)composite,and many in-situ Al_(2)O_(3)nanoparticles with an average size of 11.7±7.5 nm were dispersed homogeneously in the Cu grain.Results show that the composite demonstrates an excellent balance of high tensile strength(654±1 MPa)and high electrical conductivity(84.5±0.1%IACS),which is ascribed to the synergistic strengthening effect of ultrafine grains,dislocations,and in-situ Al_(2)O_(3)nanoparticles.This approach,which utilizes ultrafine composite powder with low-content reinforcement as a precursor and employs low-temperature and high-pressure sintering subsequently,may hold promising potential for large-scale industrial production of high-performance oxide dispersion strengthened alloys.
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financially supported by Silesian University of Technology,Poland(No.11/030/BK_23/1127)V?B–Technical University of Ostrava Czech Republic(No.CZ.02.1.01/0.0/0.0/17_049/0008399)。
文摘The effects of forward extrusion as well as extrusion combined with reversible torsion(KoBo extrusion),followed by additional deformation via the MaxStrain module of the Gleeble thermomechanical simulator,on the microstructure,mechanical properties,and electrical conductivity of a Cu−0.7Mg(wt.%)alloy,were investigated.The simulation results highlighted the critical influence of processing history on determining the equivalent strain distribution.The sample subjected to forward extrusion at 400℃and subsequent MaxStrain processing(FM sample),possessed 76%lower grain size compared to the sample processed solely with MaxStrain(AM sample).Likewise,the KoBo-extruded and MaxStrain-processed sample(KM sample)exhibited 66%smaller grain size compared to the AM sample.Tensile test results revealed that the AM,FM,and KM samples,respectively,possessed 251%,288%,and 360%higher yield strength,and 95%,121%,and 169%higher tensile strength compared to the initial annealed alloy,as a result of grain refinement as well as deformation strengthening.Finally,the electrical conductivity measurements revealed that AM,FM,and KM samples,respectively,possessed electrical conductivity values of 37.9,35.6,and 32.0 MS/m,which,by considering their mechanical properties,makes them eligible to be categorized as high-strength and high-conductivity copper alloys.
基金support provided by the National Natural Science Foundation of China(Nos.52405364,and 52171110)the Jiangsu Funding Program for Excellent Postdoctoral Talent.W.Huo acknowledges the support from the European Union Horizon 2020 Research and Innovation Program(No.857470)+1 种基金from the European Regional Development Fund via the Foundation for Polish Science International Research Agenda PLUS Program(No.MAB PLUS/2018/8)The publication was partly created within the framework of the project of the Minister of Science and Higher Education"Support for the activities of Centers of Excellence established in Poland under Horizon 2020"(No.MEiN/2023/DIR/3795).
文摘The effects of drawing strain during intermediate annealing on the microstructure and properties of Cu-20 wt%Fe alloy wires while maintaining constant total deformation were investigated.Intermediate annealing effectively removes work hardening in both the Cu matrix and Fe fibers,restoring their plastic deformation capacity and preserving fiber continuity during subsequent redrawing.The process also refines the Fe phase,leading to a more uniform size distribution and straighter,better-aligned Cu/Fe phase interfaces,thereby enhancing the comprehensive properties of the alloy.The magnitude of drawing strain during intermediate annealing plays a critical role in balancing the mechanical strength and electrical conductivity of redrawn wires.A lower initial drawing strain requires greater redrawing strain,leading to excessive hardening of the Fe fibers,which negatively impacts the electrical conductivity and tensile plasticity.Conversely,a higher initial drawing strain can result in insufficient work hardening during the redrawing deformation process,yielding minimal strength improvements.Among the tested alloys,H/3.5 wires show a slight reduction in strength and hardness compared to W and H/4.5 wires but exhibit a significant increase in tensile elongation and electrical conductivity.The tensile strength was 755 MPa,and the electrical conductivity was 47%international-annealed copper standard(IACS).The optimal performance is attributed to the formation of a high-density,ultrafine Fe fiber structure-aligned parallel to the drawing direction,which is achieved through a suitable combination of the drawing process and intermediate annealing.
基金supported by the National Natural Science Foundation of China(52225101)the Jinhua Science and Technology Program of China(2024A221787)+1 种基金the Sichuan Science and Technology Program of China(2025ZNSFSC0388)the Chongqing Special Project for Science and Technology Innovation of China(CSTB2023YSZX-JCX0006).
文摘Magnesium(Mg)alloys offer significant potential for conductive applications,thanks to their distinctive attributes,including high specific strength,excellent electrical conductivity(EC),low density,electromagnetic interference shielding effectiveness(EMI SE),and recyclability.However,a major challenge in Mg alloy research is balancing high strength with good EC,as strengthening these alloys often compromises their EC.This paper offers an in-depth analysis of the mechanisms,strategies,and applications aimed at improving the EC of Mg alloys.A bibliometric study is performed to uncover the main research trends and emerging hotspots within the field.The review then examines various strategies to improve EC focusing on factors such as solute elements,second phases,grain boundaries,textures,and vacancies.By carefully controlling alloy composition and optimizing heat treatment processes,significant advancements have been achieved by researchers in developing Mg alloys that possess both high strength and high EC,especially in Mg-Al,Mg-Zn,Mg-RE alloy systems and composites.Finally,the paper outlines future research directions,stressing the importance of further exploration into alloying element selection,heat treatment optimization,and other advanced strategies.These efforts are crucial for overcoming current challenges and expanding the application of Mg alloys in EC fields.
基金supported by the National Natural Science Foundation of China(No.51704087)the Natural Science Foundation of Heilongjiang Province(No.LH2020E083).
文摘Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electrical conductivity and mechanical properties of Al-Mg-Si alloy simultaneously,the rare earth La was introduced to modify the Al-Mg-Si alloy.The effect of La addition on the microstructure,tensile properties and electrical conductivity of cast Al-Mg-Si alloy was investigated systematically.Results indicate that the appropriate La content is helpful to improve the strength and electrical conductivity of Al-Mg-Si alloys.When the addition of La is 0.2wt.%,theα-Al grains are refined apparently,Mg and Si solute atoms in the Al matrix are reduced by the formation of Mg_(2)Si phase;the distribution of Al_(11)La_(3)phases is uniform,and the morphology of AlFeSi phase transforms from continuous state to discontinuous state.The Al-Mg-Si-0.2La alloy exhibits the optimal tensile properties and electrical conductivity,with an ultimate tensile strength of 170 MPa,a yield strength of 88 MPa,an elongation of 18.9%,and an electrical conductivity of 44.0%IACS.These values represent improvements of 9.0%,15.8%,70.3%,and 17.3%,respectively,compared to the Al-Mg-Si alloy without La addition.However,excessive La deteriorates the properties of Al-Mg-Si-xLa alloys.
基金supported by the National Natural Science Foundation of China(92163107,52171061,and 52371128)the National Key Research and Development Program of China(2022YFB3708800 and 2021YFB3501502).
文摘Immiscible bimetal systems,of which tungsten–copper(W–Cu)is a typical representative,have crucial applications in fields requiring both mechanical and physical properties.Nevertheless,it is a major challenge to determine how to give full play to the advantages of the two phases of the bimetal and achieve outstanding comprehensive properties.In this study,an ultrafine-grained W–Cu bimetal with spatially connected Cu and specific Wislands was fabricated through a designed powder-mixing process and subsequent rapid low-temperature sintering.The prepared bimetal concurrently has a high yield strength,large plastic strain,and high electrical conductivity.The stress distribution and strain response of individual phases in different types of W–Cu bimetals under loading were quantified by means of a simulation.The high yield strength of the reported bimetal results from the microstructure refinement and high contiguity of the grains in the W islands,which enhance the contribution of W to the total plastic deformation of the bimetal.The high electrical conductivity is attributed to the increased mean free path of the Cu and the reduced proportion of phase boundaries due to the specific phase combination of W islands and Cu.This work provides new insight into modulating phase configuration in immiscible metallic composites to achieve high-level multi-objective properties.
基金support provided by National Natural Science Foundation of China(Nos.52405364 and 52171110)Jiangsu Funding Program for Excellent Postdoctoral Talent+3 种基金JITRI Advanced Materials R&D Co.Ltdsupport by European Union Horizon 2020 Research and Innovation Program(857470)European Regional Development Fund via the Foundation for Polish Science International Research Agenda PLUS program(MAB PLUS/2018/8)The publication was created within the framework of the project of the Minister of Science and Higher Education,Support for the Activities of Centres of Excellence established in Poland under Horizon 2020,under contract No.MEiN/2023/DIR/3795.
文摘The deformation of Cu–20 wt.%Fe alloy wires leads to a significant improvement in mechanical properties and a decrease in electrical conductivity.Simultaneous improvements in strength and conductivity were achieved by intermediate annealing of drawn Cu–20 wt.%Fe wires.As the annealing temperature increased,the strength of Cu–20 wt.%Fe alloy wire decreased monotonically,but the electrical conductivity first increased and then decreased,reaching its peak value after annealing at 500℃.The decrease in strength is related to dislocation recovery and static recrystallization of Cu and Fe phases,and the increase in electrical conductivity mainly results from the aging precipitation of solid solution Fe.After annealing at 500℃,there was no obvious recrystallization of Cu phase,and many of the nano-Fe particles precipitated from Cu matrix.An annealing temperature of 600℃ induced the recrystallization of Cu matrix and an increase in Fe solid solubility,resulting in a decrease in strength and electrical conductivity.Subsequently,the wires annealed at 500℃ were drawn to 2 mm.Compared with those of the continuously drawn Cu–20 wt.%Fe alloy wires,the deformation ability,strength,and electrical conductivity of Cu–20 wt.%Fe alloy wires subjected to intermediate annealing treatment are significantly greater.This is mainly related to the sufficient precipitation of Fe in Cu matrix and the strengthening of refined Fe fibers parallel to the drawing direction.
基金the support from the National Natural Science Foundation of China(52403112,52473083)Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+2 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Fundamental Research Funds for the Central Universities(D5000240062,D5000240077)Undergraduate Innovation&Business Program in Northwestern Polytechnical University(202410699041)。
文摘High-performance Ti_(3)C_(2)T_(x)fibers have garnered significant potential for smart fibers enabled fabrics.Nonetheless,a major challenge hindering their widespread use is the lack of strong interlayer interactions between Ti_(3)C_(2)T_(x)nanosheets within fibers,which restricts their properties.Herein,a versatile strategy is proposed to construct wet-spun Ti_(3)C_(2)T_(x)fibers,in which trace amounts of borate form strong interlayer crosslinking between Ti_(3)C_(2)T_(x)nanosheets to significantly enhance interactions as supported by density functional theory calculations,thereby reducing interlayer spacing,diminishing microscopic voids and promoting orientation of the nanosheets.The resultant Ti_(3)C_(2)T_(x)fibers exhibit exceptional electrical conductivity of 7781 S cm^(-1)and mechanical properties,including tensile strength of 188.72 MPa and Young's modulus of 52.42 GPa.Notably,employing equilibrium molecular dynamics simulations,finite element analysis,and cross-wire geometry method,it is revealed that such crosslinking also effectively lowers interfacial thermal resistance and ultimately elevates thermal conductivity of Ti_(3)C_(2)T_(x)fibers to 13 W m^(-1)K^(-1),marking the first systematic study on thermal conductivity of Ti_(3)C_(2)T_(x)fibers.The simple and efficient interlayer crosslinking enhancement strategy not only enables the construction of thermal conductivity Ti_(3)C_(2)T_(x)fibers with high electrical conductivity for smart textiles,but also offers a scalable approach for assembling other nanomaterials into multifunctional fibers.
基金Project(51274242)supported by the National Natural Science Foundation of China
文摘The mechanism of seeded precipitation of sodium aluminate solution was studied by measuring the seeded-precipitation rate and electrical conductivity online, as well as calculating the activity and fraction of ion pair. The results show that the electrical conductivity of sodium aluminate slurry linearly decreases with increasing aluminum hydroxide addition. Moreover, both the electrical conductivity of slurry and the difference in electrical conductivity between sodium aluminate solution and slurry remarkably decline in the first 60 min before gradually increasing in the preliminary 10 h and finally reaching almost the same level after 10 h. In low Na2 O concentration solution the activities of Na OH and Na Al（OH）4 in seeded precipitation are high, which can enlarge the difference in conductivity between slurry and solution. Additionally, more ion pairs exist in solution in preliminary seeded precipitation, and the adsorption of Na＋Al（OH）4- on seed surface is likely to break the equilibrium of ion pair formation and to decrease the difference in conductivity in preliminary seeded precipitation.
基金Project (2007CB210305) supported by the National Basic Research Program of ChinaProject (51074045) supported by the National Natural Science Foundation of China
文摘The electrical conductivity of NaF-AlF3-CaF2-Al2O3-ZrO2 system was studied by a tube-type cell with fixed cell constant. The results show that the electrical conductivity of NaF-AlF3-3%Al2O3-3%CaF2-ZrO2 molten salt system decreases with increase of ZrO2 content in an interval of 0-5%. The increase of 1%ZrO2 results in a corresponding electrical conductivity decrease of 0.02 S/cm, and the equivalent conductivity increases with the increase of molar ratio of NaF to AlF3. When the temperature increases by 1 °C, the electrical conductivity increases by 0.004 S/cm. At last, the regression equations of electrical conductivity relative to temperature and ZrO2 are obtained by quadratic regression analysis.
基金Project(U1034002)supported by the National Natural Science Foundation of China(NSFC)-Guangdong Natural Science Mutual Funds
文摘CuCrZr alloys were treated with the thermal stretch process at various temperatures from 100 to 300℃.The results reveal that the thermal stretch process is successfully developed to manufacture the precipitation hardening CuCrZr alloys with a good combination of microhardness and electrical conductivity.By increasing the tensile elongations at each temperature from 100 to 300℃,the microhardness increases whereas the electrical conductivity decreases slightly.Cr-containing precipitate phases with a Nishiyama-Wasserman orientation relationship to the copper matrix were observed by TEM.The achievement of high micro-hardness and acceptable electrical conductivity in the thermal stretch treated alloys is ascribed to the interactions of the heteroatom solution,dislocation increment,grain refinement and dispersive precipitation effect.
基金Project(20110006110003)supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProject(51434005)supported by the National Natural Science Foundation of China
文摘The ambient electrical conductivity (AEC) of carbon cathode materials was investigated in respect to their open porosity, crystal structure and graphite content using hydrostatic method, four-probe technique and X-ray diffraction (XRD), respectively. The AEC is proportional to the specific conductivity (σ0) and the exponential of (1?ε) (ε is porosity) by a quasi-uniform formula based on the percolation theory. Theσ0 can reflect the intrinsic conductivity of the carbon cathodes free of pores, and it depends on the mean crystallite size parallel to the layer (002). The exponentn is dependent on the materials nature of the cathode aggregates, while an averaged value, 4.65, can practically work well with 5 types of cathode materials. The calculation ofσ0 can be extended to the graphitic cathodes containing different aggregates using the simple rule of mixture.
基金Project(50574011) supported by the National Natural Science Foundation of China
文摘As a fundamental study on recovery of valuable metals from nonferrous metallurgical slags,electrical conductivity values of MO（MO=FeO,NiO）-containing CaO-MgO-SiO2-Al2O3 slag with a low basicity were measured at different temperatures using AC impedance spectroscopy.The result shows that the electrical conductivity increased from 1.4 S/m to 14.4 S/m with the increase of the temperature from 1 573 to 1 773 K and the content of MO which is less than 12% under the constant mass ratio of （CaO＋MgO） to （SiO2＋Al2O3） of 0.47.Moreover,the increase magnitude of the electrical conductivity was also promoted with the increase of the content of MO.The electrical conductivity of FeO-containing slags was close to that of NiO-containing slags when the content was less than 8%;however,it was obviously larger than that of NiO-containing slags when the content was 12%.The activation energy of the electrical conductivity decreased with the increase of MO content.
基金The National Natural Science Foundation of China(No.50906073,31070517)China Postdoctoral Science Foundation(No.20110491332)+1 种基金Jiangsu Planned Projects for Postdoctoral Research Funds(No.1101009B)the Science and Technology Development Plan of North Jiangsu(No.BC2012444)
文摘The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.
基金supported by the Science and Technology Assistance Agency (APVV-0460-10 and SK-CN-0029-12)Slovak Grant Agency (VEGA 2/0116/14 and VEGA 2/0095/12)+2 种基金the National Natural Science Foundation of China (51322406)the Program for New Century Excellent Talents (NCET-13-0107)Ministry of Education of China
文摘Electrical conductivity of molten binary and ternary mixtures based on the system NaF-AlF3-SiO2 was investigated by means of a tube–cell （made of pyrolytic boron nitride） with stationary electrodes. Viscosity of the binary system Na3AlF6-SiO2 was measured by computerized torsion pendulum method. It was found that conductivity and viscosity varied linearly with temperature in all investigated mixtures. Obtained content dependence of electrical conductivity （isotherms） was divided into two parts. First, one represented the content region up to 10%（mole fraction） of SiO2;second, the region was with a higher content of SiO2 （from 10%up to 40%）. While the conductivity considerably decreased with content of SiO2 in the second part; it surprisingly rose in the low content range. A small addition of SiO2 to the molten cryolite （up to 10%） could slightly increase viscosity, but had no influence on the slope of this dependence since it is responsible for a glassy-networks formation in the melt. Further addition of SiO2 to the molten cryolite had a huge effect on the viscosity.
基金Project supported by the National Basic Research Program of China (No. 2005CB121108)the National Natural Science Foundation of China (No. 40371058)the National High Technology Research and Development Program of China (863 Program) (No. 2002AA2Z4061).
文摘The electrical conductivity （EC） of 1：5 soil-water extract （EC1：5） was studied utilizing path coefficient analysis. The study focused on revealing the main chemical factors contributing to EC of soil extracts and their relative importance. Results showed that the most important factors influencing the EC1：5 of coastal salt-affected soils were the concentration of salt in 1：5 soil-water extract （So）, Cl^-, and the sodium adsorption ratio （SAR）, while effects of pH, CO3^2-, HCO3^, soluble sodium percentage （SSP）, and sodium dianion ratio （SDR） were very weak. Though the direct path coefficients between EC1：5 and SO4^2- , Ca^2＋, Mg^2＋, K^＋, or Na^＋ were not high, influence of other chemical factors caused the coefficients to increase, making the summation of their direct and indirect path coefficients relatively high. Evidences showed that multiple regression relations between EC1：5 and most of the primary factors （So, Cl^-, and SAR） had sound reliability and very good accuracy.
基金supported by the Ministry of Science&Technology of China(No.2017YFA0204401)the Chinese Academy of Sciences(No.zdyz201701)+3 种基金the Liaoning Revitalization Talents Program(No.XLYC1808008)the National Natural Science Foundation of China(Nos.51501192 and 51771196)the Fundamental Research Funds for the Central Universities(No.3072019CF1017)the Key Research Program of Frontier Science,Chinese Academy of Sciences.
文摘The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,the precipitation of Cr at nanometer scale provided further strengthening and brought substantial recovery of electrical conductivity.The aged nanostructured CuCrZr alloy exhibited a high tensile strength of 832MPa and a high electrical conductivity of 71.2%IACS.The details of precipitation tuned by nanotwin boundaries were demonstrated in this work.The combined strengthening of nanostructures and nanoprecipitates was discussed.
基金Project supported by the Baotou Aluminum Co. Ltd.
文摘The effect of rare earth element Ce on mechanical performance and electrical conductivity of aluminum rod for electrical purpose were studied under industrial production condition. Using optical microscope, SEM, TEM, EDS and X-ray diffractometer, the microstructure and phase composition of aluminum rod were measured and analyzed. The results indicate that the content of rare earth element Ce is between 0.05% -0.16% in the aluminum rod for electrical purpose. Its tensile strength is enhanced to some extent. The research also discovers that the tensile strength is enhanced remarkably with impurity element Si content increases. Because influence of Si is big to the conductivity, the Si content should be controlled continuously strictly in the aluminum for electrical purpose. Adding rare earth element Ce reduces the solid solubility of Si in the aluminum matrix, and the negative effect of Si on the aluminum conductor reduces effectively. So the limit of in Si content in aluminum rod for electrical purpose can be relaxed moderately.
