High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),...High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),particularly the high-pressure torsion method,combined with the CALPHAD(calculation of phase diagram) and first-principles calculations resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials.This article reviews the recent advances in the application of SPD to developing superfunctional high-entropy materials.These superfunctional properties include(ⅰ) ultrahigh hardness levels comparable to the hardness of ceramics in high-entropy alloys,(ⅱ) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys;(ⅲ) high strength,low elastic modulus,and high biocompatibility in high-entropy alloys,(ⅳ) fast and reversible hydrogen storage in high-entropy hydrides,(ⅴ) photovoltaic performance and photocurrent generation on high-entropy semiconductors,(ⅵ) photocatalytic oxygen and hydrogen production from water splitting on high-entropy oxides and oxynitrides,and(ⅶ)CO_(2) photoreduction on high-entropy ceramics.These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to produce novel high-entropy materials with superior properties compared with conventional engineering materials.展开更多
This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepa...This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepared by melt-spinning following vacuum arc-melting.For the as-prepared and annealed samples,the carbon existed in the La_(2)Fe_(2)Si_(2)C and NaZn_(13)-type La(Fe,Si)_(13)(denoted by 1:13)phases,respectively.During the annealing process,the C atoms inhibited the diffusion reaction and depressed the generation of 1:13 phase,reducing mass fraction of the 1:13 phase in annealed La_(1.2)Fe_(11.6)Si_(1.4)Cx compounds.The introduction of carbon resulted in lattice expansion and increased the Curie temperature(T_(C))from 192 K to 273 K with x=0.5.The first-order magnetic transition was gradually transformed into the second-order magnetic transition with increasing carbon content,which induced the significant reduction of thermal and magnetic hysteresis,as well as the maximum magnetic entropy change and adiabatic temperature change vary from 18.92 J/(kg·K)to 4.60 J/(kg·K)and from 4.9 K to 2.2 K under an applied field change of 0-2 T.The results demonstrate that interstitial carbon doping is an effective strategy to improve the magnetocaloric performance of La(Fe,Si)_(13)alloys.展开更多
Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by dire...Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by direct Sb doping method.It can be found that doping Sb into Bi_(2)Te_(3) lattice array for Bi-site replacement facilitates the generation of Sb′Te anti-site defects.This anti-site defects can increase the hole concentration and optimize electrical transport properties of Bi_(2−x)Sb_(x)Te_(3) alloys.In addition,the point defects induced by mass and stress fluctuations and the Sb impurities produced during the sintering process can enhance the multi-scale phonon scattering and reduce the lattice thermal conductivity.As a result,the Bi_(0.47)Sb_(1.63)Te_(3) sample has a maximum thermoelectric figure of merit ZT of 1.04 at 350 K.It is worth noting that the bipolar effect of Bi_(2)Te_(3)-based alloys can be weakened with the increase of Sb content.The Bi_(0.44)Sb_(1.66)Te_(3) sample has a maximum average ZT value(0.93)in the temperature range of 300–500 K,indicating that direct doping of Sb can broaden the temperature range corresponding to the optimal ZT value.This work provides an idea for developing high-performance near room temperature thermoelectric materials with a wide temperature range.展开更多
ZrO_(2)-strengthened porous mullite insulation materials were prepared by foaming technology utilizing ZrSiO_(4) and Al_(2)O_(3) as primary materials and Y_(2)O_(3) as an additive.The effects of Y_(2)O_(3) contents on...ZrO_(2)-strengthened porous mullite insulation materials were prepared by foaming technology utilizing ZrSiO_(4) and Al_(2)O_(3) as primary materials and Y_(2)O_(3) as an additive.The effects of Y_(2)O_(3) contents on the phase composition,microstructure,mechanical properties,and heat conductivity of the porous mullite insulation materials were investigated.A suitable Y_(2)O_(3) content could promote phase transition of monoclinic ZrO_(2)(m-ZrO_(2))to tetragonal ZrO_(2)(t-ZrO_(2)),reduce pore size,and improve the strengths of as-prepared specimens.The cold crushing strength and bending strength of as-prepared specimens with a 119µm spherical pore size using 6 wt.%Y_(2)O_(3) were 35.2 and 13.0 MPa,respectively,with a heat conductivity being only 0.248 W/(m K).展开更多
In this work,novel medium-entropy Ca_(3)(Co_(0.25)Zn_(0.25)Mg_(0.25)Cu_(0.25))_(2)SiV_(2)O_(12)(CZMC)ceramics with garnet structure were designed and synthesized based on the entropy effect.A small average atomic size...In this work,novel medium-entropy Ca_(3)(Co_(0.25)Zn_(0.25)Mg_(0.25)Cu_(0.25))_(2)SiV_(2)O_(12)(CZMC)ceramics with garnet structure were designed and synthesized based on the entropy effect.A small average atomic size difference was proven to be advantageous for the formation of a garnet-structured solid solution,as evidenced via X-ray diffraction(XRD)and Rietveld refinement results.The sintering temperature was effectively reduced due to an increase in the configurational entropy(ΔS_(config)).The dielectric constant(ε_(r))of the CZMC ceramics showed the opposite trend to that of the Raman shift at approximately 838 cm^(−1),whereas the variation in the quality factor(Q×f)was identical to that of the relative density but opposite to that of the full width at half maximum(FWHM)of the Raman spectra.Alternating current(AC)impedance spectroscopy revealed that the conductivity of the CZMC ceramics was affected mainly by the diffusion of thermally activated oxygen vacancies.The high activation energy further indicated that the low defect concentration in the sample contributed to reducing the dielectric loss of the ceramics.The B‒O bond had the strongest contribution to the total bond energy,thus playing an important role in manipulating the temperature coefficient of the resonant frequency(τ_(f))of the ceramics.Moreover,the V‒O bond significantly influenced theε_(r)and the Q×f of the CZMC ceramics.Finally,superior microwave dielectric properties(ε_(r)=10.89,Q×f=59,200 GHz,andτ_(f)=-9.6 ppm/°C)together with a high relative density of 95.4%were achieved at 1010°C.Therefore,extensive applications can be found in the field of millimeter wave communication for CZMC ceramics.展开更多
To investigate the bonding behavior of SiC-free composite ceramics via spark plasma sintering(SPS),this study demonstrated the successful joining of B_(4)C-40 vol%TiB_(2)ceramics with a Ti foil interlayer within the t...To investigate the bonding behavior of SiC-free composite ceramics via spark plasma sintering(SPS),this study demonstrated the successful joining of B_(4)C-40 vol%TiB_(2)ceramics with a Ti foil interlayer within the temperature range of 1000-1400℃.The bonding mechanisms across temperatures were systematically elucidated through integrated approaches,including phase composition analysis,microstructural observation,and thermodynamic and diffusion kinetic calculations.The results revealed that the competitive reactions between active Ti and ceramic phases drive sequential compositional evolution at the joint interface.Starting from pure Ti,the interface transitioned to a mixture of TiB_(2),TiC,TiB,and residual Ti,ultimately forming a stable TiB_(2)-TiC-TiB ceramic assemblage as the temperature increases.Kinetic analysis revealed that between 1000 and 1300℃,the reaction layer thickness followed a diffusion-controlled growth model and was directly correlated with temperature via Arrhenius-type kinetics.At the highest temperature of 1400℃,the complete consumption of Ti yielded a full-ceramic joint.Mechanical characterization indicated that these temperature-dependent microstructural changes significantly affected joint performance.The maximum shear strength of 72 MPa was achieved at 1300℃,accompanied by crack penetration through the ceramic,reaction layer,and residual Ti layer during fracture.展开更多
B_(4)C–TiB_(2)is an advanced electrically conductive ceramic with excellent mechanical and electrical discharge machinable properties.It is challenging and rewarding to achieve highly conductive and hard B_(4)C–TiB_...B_(4)C–TiB_(2)is an advanced electrically conductive ceramic with excellent mechanical and electrical discharge machinable properties.It is challenging and rewarding to achieve highly conductive and hard B_(4)C–TiB_(2)composites at a minimum content of conductive TiB2 that has inferior hardness but double specific gravity of the B_(4)C matrix.A novel strategy was used to construct conductive networks in B_(4)C‒15 vol%TiB2 composite ceramics with B_(4)C,TiC,and amorphous B as raw materials by a two-step spark plasma sintering method.The influences of particle size matching between B_(4)C and TiC on the conducting of the strategy and the microstructure were discussed based on the selective matrix grain growth mechanism.The mechanical and electrical properties were also systematically investigated.The B_(4)C–15 vol%TiB2 composite ceramic prepared from 10.29µm B_(4)C and 0.05µm TiC powders exhibited a perfect three-dimensional interconnected conductive network with a maximum electrical conductivity of 4.25×10^(4)S/m,together with excellent mechanical properties including flexural strength,Vickers hardness,and fracture toughness of 691±58 MPa,30.30±0.61 GPa,and 5.75±0.32 MPa·m^(1/2),respectively,while the composite obtained from 3.12µm B_(4)C and 0.8µm TiC powders had the best mechanical properties including flexural strength,Vickers hardness,and fracture toughness of 827±35 MPa,32.01±0.51 GPa,and 6.45±0.22 MPa·m^(1/2),together with a decent electrical conductivity of 0.65×10^(4)S/m.展开更多
Antiferroelectric(AFE)ceramic materials with excellent temperature stability are critical for meeting ever-increasing demands for practical energy storage applications.However,how to remain high dielectric breakdown s...Antiferroelectric(AFE)ceramic materials with excellent temperature stability are critical for meeting ever-increasing demands for practical energy storage applications.However,how to remain high dielectric breakdown strategy at high temperature,at the same time to keep energy storage density(W_(rec))with high energy storage efficiency(η)is still a major challenge.In this work,polyurethane-Cu(PU-Cu)was introduced into a(Pb_(0.64)Tm_(0.04)La_(0.2))(Zr_(0.55)Sn_(0.44)Ti_(0.01))(PTL2ZST)AFE thick film to enhance the energy storage performance at high temperatures.PTL2ZST dispersed in PU-Cu because PU-Cu functions by introducing carrier traps,reducing conduction and leakage currents at high temperatures.As a result,at a working temperature of 140℃,its W_(rec)andηremain within the range of±5%compared with those of pure PTL2ZST(W_(rec)decreases by 21.7%,ηincreases by 9.4%at 100℃).Furthermore,ultrahigh W_(rec)of 17.01 J/cm^(3)withηof 80.31%in PTL2ZST-90%PU-Cu thick films at 2500 kV/cm at room temperature(RT)was obtained.Moreover,this study has outstanding filtering performance because the high degree of insulation caused by carrier traps weakens the charge carrier transport.In the rectifier circuit,the PTL2ZST-90%PU-Cu films can filter off 90%of the clutter.This study provides a feasible method to produce high-performance dielectric materials because of their high energy storage performance and heat resistance,which also broadens the field of filter application.展开更多
In the present study,graphite/alumina composites are fabricated via reductive sintering of gel-casted green bodies with structurally controlled cross-linked epoxy polymers for the first time.The cross-linking degrees ...In the present study,graphite/alumina composites are fabricated via reductive sintering of gel-casted green bodies with structurally controlled cross-linked epoxy polymers for the first time.The cross-linking degrees of polymers are tuned by the amount ratio of epoxy monomer/polyvinyl alcohol cross-linker utilized in gel-casting process.Superior electrical properties with respect to 5-fold enhanced electrical conductivity and 2-fold higher carrier mobility are successfully achieved in graphite/alumina composite fabricated from cross-linked epoxy polymer,whose phenomenon is attributed to the excellent conductive path in ceramic matrix established by highly uniform network with improved graphitization degree.展开更多
The present work aims to create lattice distortion and optimize the surface oxygen vacancy(OV)concentration in a model spinel(Co_(0.2)Cr_(0.2)Fe_(0.2)Mn_(0.2)Ni_(0.2))_(3)O_(4)high-entropy oxide(HEO)through a heteroat...The present work aims to create lattice distortion and optimize the surface oxygen vacancy(OV)concentration in a model spinel(Co_(0.2)Cr_(0.2)Fe_(0.2)Mn_(0.2)Ni_(0.2))_(3)O_(4)high-entropy oxide(HEO)through a heteroatom La^(3+)doping strategy.As demonstrated,La^(3+)with a large radius can be doped successfully into the spinel lattice of(Co_(0.2)Cr_(0.2)Fe_(0.2)Mn_(0.2)Ni_(0.2))_(3)O_(4),thereby not only causing lattice distortion to increase oxygen vacancies but also refining crystalline grains and improving the specific area.Compared with the(Co_(0.2)Cr_(0.2)Fe_(0.2)Mn_(0.2)Ni_(0.2))_(3)O_(4)anode,the(La_(0.01)CoCrFeMnNi)_(3/5.01)O_(4) anode with moderate doping exhibits excellent cycling performance(1228 mAh·g^(−1)after 400 cycles at 0.2 A·g^(−1))and yields an increase of 75%rate capability at 3 A·g^(−1)(420 mAh·g^(−1)at 3 A·g^(−1)).The desirable kinetic transport of electrons and diffusion of Li+within the moderately La^(3+)-doped anode and the synergistic interfacial pseudocapacitive behavior satisfy the redox reaction at a high rate,thus increasing rate capability.展开更多
基金the Hosokawa Powder Technology Foundation of Japan for a grantsupported by the MEXT, Japan through Grants-in-Aid for Scientific Research on Innovative Areas (Nos. JP19H05176 and JP21H00150)in part by the MEXT, Japan through Grant-in-Aid for Challenging Research Exploratory (No. JP22K18737)。
文摘High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),particularly the high-pressure torsion method,combined with the CALPHAD(calculation of phase diagram) and first-principles calculations resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials.This article reviews the recent advances in the application of SPD to developing superfunctional high-entropy materials.These superfunctional properties include(ⅰ) ultrahigh hardness levels comparable to the hardness of ceramics in high-entropy alloys,(ⅱ) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys;(ⅲ) high strength,low elastic modulus,and high biocompatibility in high-entropy alloys,(ⅳ) fast and reversible hydrogen storage in high-entropy hydrides,(ⅴ) photovoltaic performance and photocurrent generation on high-entropy semiconductors,(ⅵ) photocatalytic oxygen and hydrogen production from water splitting on high-entropy oxides and oxynitrides,and(ⅶ)CO_(2) photoreduction on high-entropy ceramics.These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to produce novel high-entropy materials with superior properties compared with conventional engineering materials.
基金supported by the National Natural Science Foundation of China(Grant No.52272263)the University Synergy Innovation Program of Anhui Province,China(Grant No.GXXT-2022-008)+2 种基金the University Natural Science Research Project of Anhui Province,China(Grant No.2024AH050145)the Youth Foundation of Anhui University of Technology(Grant No.QZ202303)the National Innovation and Entrepreneurship Training Program for College Students(Grant No.202310360018).
文摘This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepared by melt-spinning following vacuum arc-melting.For the as-prepared and annealed samples,the carbon existed in the La_(2)Fe_(2)Si_(2)C and NaZn_(13)-type La(Fe,Si)_(13)(denoted by 1:13)phases,respectively.During the annealing process,the C atoms inhibited the diffusion reaction and depressed the generation of 1:13 phase,reducing mass fraction of the 1:13 phase in annealed La_(1.2)Fe_(11.6)Si_(1.4)Cx compounds.The introduction of carbon resulted in lattice expansion and increased the Curie temperature(T_(C))from 192 K to 273 K with x=0.5.The first-order magnetic transition was gradually transformed into the second-order magnetic transition with increasing carbon content,which induced the significant reduction of thermal and magnetic hysteresis,as well as the maximum magnetic entropy change and adiabatic temperature change vary from 18.92 J/(kg·K)to 4.60 J/(kg·K)and from 4.9 K to 2.2 K under an applied field change of 0-2 T.The results demonstrate that interstitial carbon doping is an effective strategy to improve the magnetocaloric performance of La(Fe,Si)_(13)alloys.
基金supported by the Anhui Province Natural Science Foundation for Excellent Youth Scholars(2208085Y17)the University Synergy Innovation Program of Anhui Province(GXXT-2022-008+1 种基金GXXT-2021-022)the Anhui Key Lab of Metal Material and Processing Open Project.
文摘Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by direct Sb doping method.It can be found that doping Sb into Bi_(2)Te_(3) lattice array for Bi-site replacement facilitates the generation of Sb′Te anti-site defects.This anti-site defects can increase the hole concentration and optimize electrical transport properties of Bi_(2−x)Sb_(x)Te_(3) alloys.In addition,the point defects induced by mass and stress fluctuations and the Sb impurities produced during the sintering process can enhance the multi-scale phonon scattering and reduce the lattice thermal conductivity.As a result,the Bi_(0.47)Sb_(1.63)Te_(3) sample has a maximum thermoelectric figure of merit ZT of 1.04 at 350 K.It is worth noting that the bipolar effect of Bi_(2)Te_(3)-based alloys can be weakened with the increase of Sb content.The Bi_(0.44)Sb_(1.66)Te_(3) sample has a maximum average ZT value(0.93)in the temperature range of 300–500 K,indicating that direct doping of Sb can broaden the temperature range corresponding to the optimal ZT value.This work provides an idea for developing high-performance near room temperature thermoelectric materials with a wide temperature range.
基金supported by the Natural Science Foundation of Anhui Provincial Education Department(2023AH051130 and KJ2021ZD0040)the University Synergy Innovation Program of Anhui Province(GXXT-2019-015)+2 种基金National Natural Science Foundation of China(51972002)the Student Research Training Program(SRTP)of Anhui University of Technology(S202310360191)National Innovation and Entrepreneurship Training Program for College Students(202210360023).
文摘ZrO_(2)-strengthened porous mullite insulation materials were prepared by foaming technology utilizing ZrSiO_(4) and Al_(2)O_(3) as primary materials and Y_(2)O_(3) as an additive.The effects of Y_(2)O_(3) contents on the phase composition,microstructure,mechanical properties,and heat conductivity of the porous mullite insulation materials were investigated.A suitable Y_(2)O_(3) content could promote phase transition of monoclinic ZrO_(2)(m-ZrO_(2))to tetragonal ZrO_(2)(t-ZrO_(2)),reduce pore size,and improve the strengths of as-prepared specimens.The cold crushing strength and bending strength of as-prepared specimens with a 119µm spherical pore size using 6 wt.%Y_(2)O_(3) were 35.2 and 13.0 MPa,respectively,with a heat conductivity being only 0.248 W/(m K).
基金the Natural Science Foundation of Anhui Provincial Education Department(No.KJ2019A0054)the Anhui Provincial Natural Science Foundation(No.1608085ME92).
文摘In this work,novel medium-entropy Ca_(3)(Co_(0.25)Zn_(0.25)Mg_(0.25)Cu_(0.25))_(2)SiV_(2)O_(12)(CZMC)ceramics with garnet structure were designed and synthesized based on the entropy effect.A small average atomic size difference was proven to be advantageous for the formation of a garnet-structured solid solution,as evidenced via X-ray diffraction(XRD)and Rietveld refinement results.The sintering temperature was effectively reduced due to an increase in the configurational entropy(ΔS_(config)).The dielectric constant(ε_(r))of the CZMC ceramics showed the opposite trend to that of the Raman shift at approximately 838 cm^(−1),whereas the variation in the quality factor(Q×f)was identical to that of the relative density but opposite to that of the full width at half maximum(FWHM)of the Raman spectra.Alternating current(AC)impedance spectroscopy revealed that the conductivity of the CZMC ceramics was affected mainly by the diffusion of thermally activated oxygen vacancies.The high activation energy further indicated that the low defect concentration in the sample contributed to reducing the dielectric loss of the ceramics.The B‒O bond had the strongest contribution to the total bond energy,thus playing an important role in manipulating the temperature coefficient of the resonant frequency(τ_(f))of the ceramics.Moreover,the V‒O bond significantly influenced theε_(r)and the Q×f of the CZMC ceramics.Finally,superior microwave dielectric properties(ε_(r)=10.89,Q×f=59,200 GHz,andτ_(f)=-9.6 ppm/°C)together with a high relative density of 95.4%were achieved at 1010°C.Therefore,extensive applications can be found in the field of millimeter wave communication for CZMC ceramics.
基金supported by the National Natural Science Foundation of China(Nos.52472061,52171148,and 52072003)the Natural Science Foundation of Anhui Provincial Education Department(Nos.2024AH040031 and 2023AH052703).
文摘To investigate the bonding behavior of SiC-free composite ceramics via spark plasma sintering(SPS),this study demonstrated the successful joining of B_(4)C-40 vol%TiB_(2)ceramics with a Ti foil interlayer within the temperature range of 1000-1400℃.The bonding mechanisms across temperatures were systematically elucidated through integrated approaches,including phase composition analysis,microstructural observation,and thermodynamic and diffusion kinetic calculations.The results revealed that the competitive reactions between active Ti and ceramic phases drive sequential compositional evolution at the joint interface.Starting from pure Ti,the interface transitioned to a mixture of TiB_(2),TiC,TiB,and residual Ti,ultimately forming a stable TiB_(2)-TiC-TiB ceramic assemblage as the temperature increases.Kinetic analysis revealed that between 1000 and 1300℃,the reaction layer thickness followed a diffusion-controlled growth model and was directly correlated with temperature via Arrhenius-type kinetics.At the highest temperature of 1400℃,the complete consumption of Ti yielded a full-ceramic joint.Mechanical characterization indicated that these temperature-dependent microstructural changes significantly affected joint performance.The maximum shear strength of 72 MPa was achieved at 1300℃,accompanied by crack penetration through the ceramic,reaction layer,and residual Ti layer during fracture.
基金the National Natural Science Foundation of China(Nos.52072003 and 52002003)the Natural Science Foundation of Anhui Provincial Education Department(Nos.2023AH052095 and KJ2021A0405)the Natural Science Foundation of Anhui Province(No.2208085QE146).
文摘B_(4)C–TiB_(2)is an advanced electrically conductive ceramic with excellent mechanical and electrical discharge machinable properties.It is challenging and rewarding to achieve highly conductive and hard B_(4)C–TiB_(2)composites at a minimum content of conductive TiB2 that has inferior hardness but double specific gravity of the B_(4)C matrix.A novel strategy was used to construct conductive networks in B_(4)C‒15 vol%TiB2 composite ceramics with B_(4)C,TiC,and amorphous B as raw materials by a two-step spark plasma sintering method.The influences of particle size matching between B_(4)C and TiC on the conducting of the strategy and the microstructure were discussed based on the selective matrix grain growth mechanism.The mechanical and electrical properties were also systematically investigated.The B_(4)C–15 vol%TiB2 composite ceramic prepared from 10.29µm B_(4)C and 0.05µm TiC powders exhibited a perfect three-dimensional interconnected conductive network with a maximum electrical conductivity of 4.25×10^(4)S/m,together with excellent mechanical properties including flexural strength,Vickers hardness,and fracture toughness of 691±58 MPa,30.30±0.61 GPa,and 5.75±0.32 MPa·m^(1/2),respectively,while the composite obtained from 3.12µm B_(4)C and 0.8µm TiC powders had the best mechanical properties including flexural strength,Vickers hardness,and fracture toughness of 827±35 MPa,32.01±0.51 GPa,and 6.45±0.22 MPa·m^(1/2),together with a decent electrical conductivity of 0.65×10^(4)S/m.
基金supported by the Key Project of the Anhui Provincial Department of Education Fund(No.2023AH051103)the National Innovation and Entrepreneurship Training Program for College Students(Nos.202410360029 and 202310360023)+1 种基金the Anhui Provincial Natural Science Foundation(No.2108085QE193)the Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices(No.EFMD2024013M).
文摘Antiferroelectric(AFE)ceramic materials with excellent temperature stability are critical for meeting ever-increasing demands for practical energy storage applications.However,how to remain high dielectric breakdown strategy at high temperature,at the same time to keep energy storage density(W_(rec))with high energy storage efficiency(η)is still a major challenge.In this work,polyurethane-Cu(PU-Cu)was introduced into a(Pb_(0.64)Tm_(0.04)La_(0.2))(Zr_(0.55)Sn_(0.44)Ti_(0.01))(PTL2ZST)AFE thick film to enhance the energy storage performance at high temperatures.PTL2ZST dispersed in PU-Cu because PU-Cu functions by introducing carrier traps,reducing conduction and leakage currents at high temperatures.As a result,at a working temperature of 140℃,its W_(rec)andηremain within the range of±5%compared with those of pure PTL2ZST(W_(rec)decreases by 21.7%,ηincreases by 9.4%at 100℃).Furthermore,ultrahigh W_(rec)of 17.01 J/cm^(3)withηof 80.31%in PTL2ZST-90%PU-Cu thick films at 2500 kV/cm at room temperature(RT)was obtained.Moreover,this study has outstanding filtering performance because the high degree of insulation caused by carrier traps weakens the charge carrier transport.In the rectifier circuit,the PTL2ZST-90%PU-Cu films can filter off 90%of the clutter.This study provides a feasible method to produce high-performance dielectric materials because of their high energy storage performance and heat resistance,which also broadens the field of filter application.
文摘In the present study,graphite/alumina composites are fabricated via reductive sintering of gel-casted green bodies with structurally controlled cross-linked epoxy polymers for the first time.The cross-linking degrees of polymers are tuned by the amount ratio of epoxy monomer/polyvinyl alcohol cross-linker utilized in gel-casting process.Superior electrical properties with respect to 5-fold enhanced electrical conductivity and 2-fold higher carrier mobility are successfully achieved in graphite/alumina composite fabricated from cross-linked epoxy polymer,whose phenomenon is attributed to the excellent conductive path in ceramic matrix established by highly uniform network with improved graphitization degree.
基金supported by the University Natural Science Research Project of Anhui Province in China(No.2023AH051104)the Director’s Fund of Key Laboratory of Green Fabrication and Surface Technology of Advance Metal Materials,Ministry of Education(No.GFST2022ZR08).
文摘The present work aims to create lattice distortion and optimize the surface oxygen vacancy(OV)concentration in a model spinel(Co_(0.2)Cr_(0.2)Fe_(0.2)Mn_(0.2)Ni_(0.2))_(3)O_(4)high-entropy oxide(HEO)through a heteroatom La^(3+)doping strategy.As demonstrated,La^(3+)with a large radius can be doped successfully into the spinel lattice of(Co_(0.2)Cr_(0.2)Fe_(0.2)Mn_(0.2)Ni_(0.2))_(3)O_(4),thereby not only causing lattice distortion to increase oxygen vacancies but also refining crystalline grains and improving the specific area.Compared with the(Co_(0.2)Cr_(0.2)Fe_(0.2)Mn_(0.2)Ni_(0.2))_(3)O_(4)anode,the(La_(0.01)CoCrFeMnNi)_(3/5.01)O_(4) anode with moderate doping exhibits excellent cycling performance(1228 mAh·g^(−1)after 400 cycles at 0.2 A·g^(−1))and yields an increase of 75%rate capability at 3 A·g^(−1)(420 mAh·g^(−1)at 3 A·g^(−1)).The desirable kinetic transport of electrons and diffusion of Li+within the moderately La^(3+)-doped anode and the synergistic interfacial pseudocapacitive behavior satisfy the redox reaction at a high rate,thus increasing rate capability.
