Fluorite-structured oxides constitute an important category of oxides with a wide range of high-temperature applications.Following the concept of high entropy,high-entropy fluorite oxides(HEFOs)have showcased intrigui...Fluorite-structured oxides constitute an important category of oxides with a wide range of high-temperature applications.Following the concept of high entropy,high-entropy fluorite oxides(HEFOs)have showcased intriguing high-temperature application potential.However,unlocking this potential necessitates an assessment of their long-term stability under high-temperature conditions.In this study,we conducted a prolonged heat treatment at 1000℃on typical HEFO,specifically(CeHfZrGdLa)O_(x).After 100 h,high-intensity X-ray diffraction(XRD)revealed a transition from a single-phase fluorite to a multi-phase configuration.Further investigation by analytical electron microscoy(AEM)demonstrated that this degradation resulted from facilitated element diffusion and consequent escalating chemical fluctuation at high temperatures,leading to spontaneous segregation and separation of Ce and La elements,forming Ce-rich,La-poor,and La-rich phases.Notably,the La-rich phase spontaneously transformed from a fluorite structure(space group Fm3m)to a bixbyite structure(space group Ia3)at elevated temperatures,resulting in the appearance of superstructure reflection in XRD profiles and electron diffraction patterns.Despite the intricate phase decomposition,the energy band gap showed minimal variation,suggesting potential property stability of(CeHfZrGdLa)O_(x)across a broad range of compositions.These findings offer valuable insights into the future applications of HEFOs.展开更多
In this study,tri-rutile type Mg_(0.5)Ti_(0.5)TaO_(4) ceramics were synthesized,where the structure–property relationship,especially the structural configuration and intrinsic dielectric origin of Mg_(0.5)Ti_(0.5)TaO...In this study,tri-rutile type Mg_(0.5)Ti_(0.5)TaO_(4) ceramics were synthesized,where the structure–property relationship,especially the structural configuration and intrinsic dielectric origin of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,and the low-firing characteristics were studied.It is found that the tri-rutile structural type is unambiguously identified through the Rietveld refinement analysis,the selected area electron diffraction(SAED),and the high-resolution transmission electron microscopy(HRTEM)along the[110]zone axis.With the increase in sintering temperature,the densification and uniformity of crystal growth play important roles in regulating the microwave dielectric properties of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics.Intrinsically,theoretical dielectric properties calculated by the far-infrared reflective spectra approached the experimental values,indicating the importance of structural features to dielectric properties.Furthermore,a glass additive with high matching relevance with ceramics has been developed to decrease the high sintering temperature of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,where 2–4 wt%Li_(2)O–MgO–ZnO–B_(2)O_(3)–SiO_(2)(LMZBS)glass frit was adopted to reduce the suitable temperature from 1275 to 1050℃ without significantly deteriorating the microwave dielectric characteristics.Specifically,Mg_(0.5)Ti_(0.5)TaO_(4) ceramics containing 2 wt% glass addition sintered at 1050℃for 4 h possess excellent microwave dielectric properties:dielectric constant(ε_(r))=44.3,quality factor multiplied by resonant frequency(Q×f)=23,820 GHz(f=6.2 GHz),and the temperature coefficient of resonant frequency(τ_(f))=123.2 ppm/℃.展开更多
Silver vanadates are promising visible-light-responded photocatalysts with suitable bandgap for solar absorption.However,the easy recombination of photogenerated carriers limits their performance.To overcome this obst...Silver vanadates are promising visible-light-responded photocatalysts with suitable bandgap for solar absorption.However,the easy recombination of photogenerated carriers limits their performance.To overcome this obstacle,a novel 2D graphene oxide(GO)modifiedα-AgVO_(3) nanorods(GO/α-AgVO_(3) )photocatalyst was designed herein to improve the separation of photocarriers.The GO/α-AgVO_(3) was fabricated through a facile in-situ coprecipitation method at room temperature.It was found that the as-prepared 0.5 wt%GO/α-AgVO_(3) exhibited the most excellent performance for rhodamine B(RhB)decomposition,with an apparent reaction rate constant 18 times higher than that of pureα-AgVO_(3) under visible-light irradiation.In light of the first-principles calculations and the hetero junction analysis,the mechanism underpinned the enhanced photocatalytic performance was proposed.The enhanced photocatalytic performance was ascribed to the appropriate bandgap ofα-AgVO_(3) nanorods for visible-light response and efficient separation of photocarriers through GO nanosheets.This work demonstrates the feasibility of overcoming the easy recombination of photogenerated carriers and provides a valuable GO/α-AgVO_(3) photocatalyst for pollutant degradation.展开更多
Highly transparent 0.5 and 1.0 at%Pr-doped Y_(2)O_(3)ceramics were fabricated by vacuum sintering plus hot isostatic pressing(HIP)treatment.The selection of suitable pre-sintering temperatures and right microstructure...Highly transparent 0.5 and 1.0 at%Pr-doped Y_(2)O_(3)ceramics were fabricated by vacuum sintering plus hot isostatic pressing(HIP)treatment.The selection of suitable pre-sintering temperatures and right microstructures before HIP was critical to obtain high density of the final sintered bodies.The well-densified ceramics had pore-free microstructures with an average grain size of about 1μm.It was also found that the charge states of the Pr ions could be changed through regulating the annealing atmospheres,resulting in different absorption and emission characteristics in the visible wavelength region.Annealing in reducing atmosphere(5%H_(2)/95%Ar)favored the formation of Pr^(3+),resulting in stronger red emissions,while annealing in oxygen atmosphere led to the rise of lattice constant due to the concentration increase of oxygen interstitials.The H_(2)/Ar-annealed 0.5 at%Pr:Y_(2)O_(3)ceramics exhibited strong red emission at 600–675 nm,which may be a promising gain material for red solid-state lasers.展开更多
The growing demand for high-power-density electric and electronic systems has encouraged the development of energy-storage capacitors with attributes such as high energy density,high capacitance density,high voltage a...The growing demand for high-power-density electric and electronic systems has encouraged the development of energy-storage capacitors with attributes such as high energy density,high capacitance density,high voltage and frequency,low weight,high-temperature operability,and environmental friendliness.Compared with their electrolytic and film counterparts,energy-storage multilayer ceramic capacitors(MLCCs)stand out for their extremely low equivalent series resistance and equivalent series inductance,high current handling capability,and high-temperature stability.These characteristics are important for applications including fast-switching third-generation wide-bandgap semiconductors in electric vehicles,5G base stations,clean energy generation,and smart grids.There have been numerous reports on state-of-the-art MLCC energy-storage solutions.However,lead-free capacitors generally have a low-energy density,and high-energy density capacitors frequently contain lead,which is a key issue that hinders their broad application.In this review,we present perspectives and challenges for lead-free energy-storage MLCCs.Initially,the energy-storage mechanism and device characterization are introduced;then,dielectric ceramics for energy-storage applications with aspects of composition and structural optimization are summarized.Progress on state-of-the-art energy-storage MLCCs is discussed after elaboration of the fabrication process and structural design of the electrode.Emerging applications of energy-storage MLCCs are then discussed in terms of advanced pulsed power sources and high-density power converters from a theoretical and technological point of view.Finally,the challenges and future prospects for industrialization of lab-scale lead-free energy-storage MLCCs are discussed.展开更多
ZrB_(2)-SiBCN ceramics with ZrO_(2) additive are hot-pressed under a constant applied pressure.The densification behavior of the composites is studied in a view of creep deformation by means of the Bernard-Granger and...ZrB_(2)-SiBCN ceramics with ZrO_(2) additive are hot-pressed under a constant applied pressure.The densification behavior of the composites is studied in a view of creep deformation by means of the Bernard-Granger and Guizard model.With determination of the stress exponent(n)and the apparent activation energy(Q_(d)),the specific deformation mechanisms controlling densification are supposed.Within lower temperature ranges of 1300-1400℃,the operative mechanism is considered to be grain boundary sliding accommodated by atom diffusion of the polymer-derived SiBCN(n=1,Q_(d)=123±5 kJ/mol)and by viscous flow of the amorphous SiBCN(n=2,Qd=249±5 kJ/mol).At higher temperatures,the controlling mechanism transforms to lattice or intra-granular diffusion creep(n=3-5)due to gradual consumption of the amorphous phase.It is suggested that diffusion of oxygen ions inside ZrO_(2) into the amorphous SiBCN decreases the viscosity,modifies the fluidity,and contributes to the grain boundary mobility.展开更多
Silicon carbide(SiC) has been widely concerned for its excellent overall mechanical and physical properties, such as low density, good thermal-shock behavior, high temperature oxidation resistance, and radiation resis...Silicon carbide(SiC) has been widely concerned for its excellent overall mechanical and physical properties, such as low density, good thermal-shock behavior, high temperature oxidation resistance, and radiation resistance; as a result, the SiC-based materials have been or are being widely used in most advanced fields involving aerospace, aviation, military, and nuclear power. Joining of SiC-based materials(monolithic SiC and SiCf/SiC composites) can resolve the problems on poor processing performance and difficulty of fabrication of large-sized and complex-shaped components to a certain extent, which are originated from their high inherent brittleness and low impact toughness.Starting from the introduction to SiC-based materials, joining of ceramics, and joint strength characterization, the joining of SiC-based materials is reviewed by classifying the as-received interlayer materials, involving no interlayer, metallic, glass-ceramic, and organic interlayers. In particular, joining processes(involving joining techniques and parameter conditions), joint strength,interfacial microstructures, and/or reaction products are highlighted for understanding interfacial behavior and for supporting development of application-oriented joining techniques.展开更多
The influence of adding Fe_(2)O_(3) at the expense of Na_(2)O in sodium lead borate glasses on the structural,physical and electrical properties have been investigated.Results obtained from Fourier transform infrared(...The influence of adding Fe_(2)O_(3) at the expense of Na_(2)O in sodium lead borate glasses on the structural,physical and electrical properties have been investigated.Results obtained from Fourier transform infrared(FTIR)spectra indicated that Fe_(2)O_(3) plays an important role in converting three coordinated boron atoms[BO_(3)]to four coordinated boron atoms[BO4].The physical properties such as density and molar volume helped to evaluate the compact structure of the prepared glass samples due to presence of[BO4]groups.The increase of Fe_(2)O_(3)/Na_(2)O replacements led to increasing the microhardness values and decreasing the thermal expansion coefficients of the studied glasses.The increase of Fe_(2)O_(3)/Na_(2)O replacements generally decreased the AC conductivity.That decrease might be due to converting of the three coordinated boron atoms[BO_(3)]to four coordinated boron atoms[BO_(4)].Dielectric constants of the samples might be an indication of the distortion in the coordinated boron atoms.The obtained experimental data indicated the internal structure of glass network and the change of the structure of the samples from three[BO_(3)]to four coordinated boron atoms[BO4].展开更多
Lithium titanate(Li_(2)TiO_(3))is one of the most promising candidates among the tritium breeding materials because of its good tritium release capacity.Li concentration has much significance on the diffusivity of tri...Lithium titanate(Li_(2)TiO_(3))is one of the most promising candidates among the tritium breeding materials because of its good tritium release capacity.Li concentration has much significance on the diffusivity of tritium in the material.The nanocrystalline single-phase Li_(2)TiO_(3) with monoclinic structure has been prepared by high energy ball milling followed by calcination at 700℃for 2 h.The field emission scanning electron microscopy(FESEM)studies confirmed uniform distribution of nanocrystalline phase with particle size below 100 nm.The study of the Li^(+)ion diffusion on the sintered sample was investigated by means of electrical conductivity measurements.Electrical properties of the samples were studied in wide temperature(50-500℃)and frequency(100 Hz-1 MHz)ranges.The complex impedance spectroscopy(CIS)studies showed the presence of both bulk and grain boundary effects in nanocrystalline Li_(2)TiO_(3).The bulk resistance of the samples has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance(NTCR)behavior.The low activation energies of the samples suggested the presence of singly ionized oxygen vacancies in the conduction process.The hopping frequency shifted toward higher frequency with increase in temperature.Activation energy of 0.86 eV was calculated from AC conductivity.展开更多
Multilayer ceramic actuator(MLCA)has been widely employed in actuators due to the large cumulative displacement under the low driving voltage.In this work,the MLCA devices consisting of a lead-free MnCO_(3-)and CuO-do...Multilayer ceramic actuator(MLCA)has been widely employed in actuators due to the large cumulative displacement under the low driving voltage.In this work,the MLCA devices consisting of a lead-free MnCO_(3-)and CuO-doped 0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Ta_(0.04))O_(3)-0.04CaZrO_(3) piezoelectric ceramics and a base nickel(Ni)metal inner electrode were well co-fired by the two-step sintering process in a reducing atmosphere.The ceramic layer/electrode interface is well-integrated and clearly continuous without distinct interdiffusion and chemical reaction,which is beneficial to the electrical reliability of the MLCA.As a result,the MLCA laminated with nine active ceramic layers obtains an ultrahigh piezoelectric coefficient d_(33) of 3157 pC/N,about 9 times than bulk ceramics.The 0.5 mm-thick MLCA composed of a series of~50μm-thick ceramic layers and~3μm-thick Ni electrodes reaches a high 1.8μm displacement under the low applied voltage of 200 V(the same displacement requires a voltage as high as 3700 V for~1 mm-thick bulk ceramics).The excellent electrical performance and low-cost base electrode reveal that the(K,Na)NbO_(3)(KNN)-based MLCAs are promising lead-free candidate for actuator application.展开更多
1 Manuscript submissionLegal requirementsSubmission of a manuscript implies:that the work described has not been published before;that it is not underconsideration for publication anywhere else;that its publication ha...1 Manuscript submissionLegal requirementsSubmission of a manuscript implies:that the work described has not been published before;that it is not underconsideration for publication anywhere else;that its publication has been approved by all co-authors,if any,as wellas by the responsible authorities--tacitly or explicitly--at the institute where the work has been carried out.Thepublisher will not be held legally responsible should there be any claims for compensation.展开更多
High-entropy oxides(HEOs)are a new class of emerging materials with fascinating properties(such as structural stability,tensile strength,and corrosion resistance).High-entropy oxide coated Ni-rich cathode materials ha...High-entropy oxides(HEOs)are a new class of emerging materials with fascinating properties(such as structural stability,tensile strength,and corrosion resistance).High-entropy oxide coated Ni-rich cathode materials have great potential to improve the electrochemical performance.Here,we present a facile self-ball milling method to obtain(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Zr_(2)O_(7)(HEO)coated LiNi_(0.8)Co_(_(0.1))Mn_(_(0.1))O_(2)(NCM811).The HEO coating endows NCM811 with a stable surface,reduces the contact with the external environment(air and electrolyte),and inhibits side reactions between cathode and electrolyte.These favorable effects,especially when the coating amount is 5 wt%,result in a significant reduction of the battery polarization and an increase in the capacity retention from 57.3%(NCM811)to 74.2%(5HEO-NCM811)after 300 cycles at 1 C(1 C=200 mA·h·g^(−1)).Moreover,the morphology and spectroscopy analysis after the cycles confirmed the inhibitory effect of the HEO coating on electrolyte decomposition,which is important for the cycle life.Surprisingly,HEO coating reduces the viscosity of slurry by 37%–38%and significantly improves the flowability of the slurry with high solid content.This strategy confirms the feasibility of HEO-modified Ni-rich cathode materials and provides a new idea for the design of high-performance cathode materials for Li-ion batteries.展开更多
In this work,gold nanoparticles(AuNPs)decorated Ti_(3)C_(2)T_(x) nanosheets(MXene/AuNPs composite)are fabricated through a self-reduction reaction of Ti_(3)C_(2)T_(x) nanosheets with HAuCl_(4) aqueous solution.The obt...In this work,gold nanoparticles(AuNPs)decorated Ti_(3)C_(2)T_(x) nanosheets(MXene/AuNPs composite)are fabricated through a self-reduction reaction of Ti_(3)C_(2)T_(x) nanosheets with HAuCl_(4) aqueous solution.The obtained composite is characterized as AuNPs with the diameter of about 23 nm uniformly dispersing on nanosheets without aggregation.The composite(MXene decorated on 4.8 wt% AuNPs)is further employed to construct supercapacitor for the first time with a higher specific capacitance of 278 F·g^(-1) at 5 mV·s^(-1) than that of pure Ti_(3)C_(2)T_(x) and 95% of cyclic stability after 10,000 cycles.Furthermore,MXene/AuNPs composite symmetric supercapacitor with filter paper as separator and H_(2)SO_(4) as electrolyte,is assembled.The supercapacitor exhibits a high volumetric energy density of 8.82 Wh·L^(-1) at a power density of 264.6 W·L^(-1) and ultrafast-charging/discharging performance.It exhibits as a promising candidate applied in integrated and flexible supercapacitors.展开更多
Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes.To address these issues,we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny sili...Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes.To address these issues,we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny silicon particles as the core assisted by small amount of SiC.Skillfully exploiting the high heat from magnesiothermic reduction,SiC can assist the good dispersion of silicon and provide good interface compatibility and chemical stability.The silicon anchored to the carbon shell provides multipoint contact mode,that together with the carbon shell frame,significantly promoting the transfer of dual charge.Besides,the pomegranate-type microcluster structure also improves the tap density of the electrode,reduces the direct contact area between active material and electrolyte,and enhances the electrochemical performance.展开更多
Self-toughening ZrB2–SiC based composites are fabricated by in-situ reactive hot pressing.The effect of sintering additive content on the microstructure and mechanical properties of the composites is investigated.Mic...Self-toughening ZrB2–SiC based composites are fabricated by in-situ reactive hot pressing.The effect of sintering additive content on the microstructure and mechanical properties of the composites is investigated.Microstructure observation found that the in-situ reactive hot pressing could promote the anisotropic growth of ZrB2 grains and the formation of interlocking microstructure.Such microstructure could improve the mechanical properties,especially,for the fracture toughness.The improved mechanical properties could be attributed to the self-toughening structure related to the ZrB2 platelets and the formed interlocking microstructure,which could trigger various toughening mechanisms such as grain pull-out,crack bridging,crack deflection,and crack branching,providing the main contribution to the high fracture toughness.展开更多
To quantify the oxygen content in molten salts, we examined the performance of an yttria-stabilized zirconia solid electrolyte oxygen sensor with a Bi/Bi_2O_3 reference electrode, focusing on its output accuracy. When...To quantify the oxygen content in molten salts, we examined the performance of an yttria-stabilized zirconia solid electrolyte oxygen sensor with a Bi/Bi_2O_3 reference electrode, focusing on its output accuracy. When the above sensor was tested in a flow of gas with known oxygen partial pressure, pO_2, a linear relationship between lgpO_2 and the electromotive force(EMF) was observed, and the correlation slope exhibited a positive deviation from Nernstian behavior. EMF measurements performed in molten NaCl–KCl indicated that the oxygen content of this salt mixture increased with increasing oxygen partial pressure in the covering gas, in agreement with Henry's law. Moreover, the EMF exhibited a linear decrease with increasing melt temperature of molten NaCl–KCl, in agreement with the theoretical model. Finally, a relationship between the structure of molten NaCl–KCl and its oxygen diffusion behavior was established. As a result, the developed sensor was demonstrated to be well suited for determining the oxygen content of molten salts.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.52150610487 and 51850410501).The authors acknowledge the help of Dr.Linlin Ma for UV-Vis spectra from the Instrumental Analytical Center of Shanghai Jiao Tong University.
文摘Fluorite-structured oxides constitute an important category of oxides with a wide range of high-temperature applications.Following the concept of high entropy,high-entropy fluorite oxides(HEFOs)have showcased intriguing high-temperature application potential.However,unlocking this potential necessitates an assessment of their long-term stability under high-temperature conditions.In this study,we conducted a prolonged heat treatment at 1000℃on typical HEFO,specifically(CeHfZrGdLa)O_(x).After 100 h,high-intensity X-ray diffraction(XRD)revealed a transition from a single-phase fluorite to a multi-phase configuration.Further investigation by analytical electron microscoy(AEM)demonstrated that this degradation resulted from facilitated element diffusion and consequent escalating chemical fluctuation at high temperatures,leading to spontaneous segregation and separation of Ce and La elements,forming Ce-rich,La-poor,and La-rich phases.Notably,the La-rich phase spontaneously transformed from a fluorite structure(space group Fm3m)to a bixbyite structure(space group Ia3)at elevated temperatures,resulting in the appearance of superstructure reflection in XRD profiles and electron diffraction patterns.Despite the intricate phase decomposition,the energy band gap showed minimal variation,suggesting potential property stability of(CeHfZrGdLa)O_(x)across a broad range of compositions.These findings offer valuable insights into the future applications of HEFOs.
基金support from the open research fund of Songshan Lake Materials Laboratory (No.2022SLABFN20)the Qinchuangyuan Citing Highlevel Innovation and Entrepreneurship Talent Projects (No.QCYRCXM-2022-40)+3 种基金the Natural Science Basic Research Program of Shaanxi (No.2022JQ-390)the National Natural Science Foundation of China (No.52102123)the National Key R&D Program of China (No.2022YFB2807405)the Natural Science Foundation of Sichuan Province (Nos.22NSFSC1973 and 2022NSFSC1959).
文摘In this study,tri-rutile type Mg_(0.5)Ti_(0.5)TaO_(4) ceramics were synthesized,where the structure–property relationship,especially the structural configuration and intrinsic dielectric origin of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,and the low-firing characteristics were studied.It is found that the tri-rutile structural type is unambiguously identified through the Rietveld refinement analysis,the selected area electron diffraction(SAED),and the high-resolution transmission electron microscopy(HRTEM)along the[110]zone axis.With the increase in sintering temperature,the densification and uniformity of crystal growth play important roles in regulating the microwave dielectric properties of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics.Intrinsically,theoretical dielectric properties calculated by the far-infrared reflective spectra approached the experimental values,indicating the importance of structural features to dielectric properties.Furthermore,a glass additive with high matching relevance with ceramics has been developed to decrease the high sintering temperature of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,where 2–4 wt%Li_(2)O–MgO–ZnO–B_(2)O_(3)–SiO_(2)(LMZBS)glass frit was adopted to reduce the suitable temperature from 1275 to 1050℃ without significantly deteriorating the microwave dielectric characteristics.Specifically,Mg_(0.5)Ti_(0.5)TaO_(4) ceramics containing 2 wt% glass addition sintered at 1050℃for 4 h possess excellent microwave dielectric properties:dielectric constant(ε_(r))=44.3,quality factor multiplied by resonant frequency(Q×f)=23,820 GHz(f=6.2 GHz),and the temperature coefficient of resonant frequency(τ_(f))=123.2 ppm/℃.
基金This work was financially supported by the National Natural Science Foundation of China(No.52102068)the Key Laboratory Foundation of the Science and Technology on Advanced Functional Composite Laboratory(No.6142906200509)+2 种基金the Natural Science Foundation of Jiangsu Province(No.20KJB430017)NUPTSF(No.NY219162)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX20_0789).
文摘Silver vanadates are promising visible-light-responded photocatalysts with suitable bandgap for solar absorption.However,the easy recombination of photogenerated carriers limits their performance.To overcome this obstacle,a novel 2D graphene oxide(GO)modifiedα-AgVO_(3) nanorods(GO/α-AgVO_(3) )photocatalyst was designed herein to improve the separation of photocarriers.The GO/α-AgVO_(3) was fabricated through a facile in-situ coprecipitation method at room temperature.It was found that the as-prepared 0.5 wt%GO/α-AgVO_(3) exhibited the most excellent performance for rhodamine B(RhB)decomposition,with an apparent reaction rate constant 18 times higher than that of pureα-AgVO_(3) under visible-light irradiation.In light of the first-principles calculations and the hetero junction analysis,the mechanism underpinned the enhanced photocatalytic performance was proposed.The enhanced photocatalytic performance was ascribed to the appropriate bandgap ofα-AgVO_(3) nanorods for visible-light response and efficient separation of photocarriers through GO nanosheets.This work demonstrates the feasibility of overcoming the easy recombination of photogenerated carriers and provides a valuable GO/α-AgVO_(3) photocatalyst for pollutant degradation.
基金The research is partially supported by the fund of A*Star of Singapore(Grant No.A1883C0003)the National Natural Science Foundation of China(Grant Nos.62075089,61875078,and 61861136007)+1 种基金Natural Science Foundation of Jiangsu Province(Grant Nos.BK20191002 and BK20190992)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_2339).
文摘Highly transparent 0.5 and 1.0 at%Pr-doped Y_(2)O_(3)ceramics were fabricated by vacuum sintering plus hot isostatic pressing(HIP)treatment.The selection of suitable pre-sintering temperatures and right microstructures before HIP was critical to obtain high density of the final sintered bodies.The well-densified ceramics had pore-free microstructures with an average grain size of about 1μm.It was also found that the charge states of the Pr ions could be changed through regulating the annealing atmospheres,resulting in different absorption and emission characteristics in the visible wavelength region.Annealing in reducing atmosphere(5%H_(2)/95%Ar)favored the formation of Pr^(3+),resulting in stronger red emissions,while annealing in oxygen atmosphere led to the rise of lattice constant due to the concentration increase of oxygen interstitials.The H_(2)/Ar-annealed 0.5 at%Pr:Y_(2)O_(3)ceramics exhibited strong red emission at 600–675 nm,which may be a promising gain material for red solid-state lasers.
基金supported by National Key R&D Program of China(No.2017YFB0406302)Key-Area Research and Development Program of Guangdong Province(No.2019B090912003)+2 种基金the National Natural Science Foundation of China(No.52002253)Sichuan Science and Technology Program(No.2021YFH0181)Shuimu Tsinghua Scholar Program,and State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KFZD202002).
文摘The growing demand for high-power-density electric and electronic systems has encouraged the development of energy-storage capacitors with attributes such as high energy density,high capacitance density,high voltage and frequency,low weight,high-temperature operability,and environmental friendliness.Compared with their electrolytic and film counterparts,energy-storage multilayer ceramic capacitors(MLCCs)stand out for their extremely low equivalent series resistance and equivalent series inductance,high current handling capability,and high-temperature stability.These characteristics are important for applications including fast-switching third-generation wide-bandgap semiconductors in electric vehicles,5G base stations,clean energy generation,and smart grids.There have been numerous reports on state-of-the-art MLCC energy-storage solutions.However,lead-free capacitors generally have a low-energy density,and high-energy density capacitors frequently contain lead,which is a key issue that hinders their broad application.In this review,we present perspectives and challenges for lead-free energy-storage MLCCs.Initially,the energy-storage mechanism and device characterization are introduced;then,dielectric ceramics for energy-storage applications with aspects of composition and structural optimization are summarized.Progress on state-of-the-art energy-storage MLCCs is discussed after elaboration of the fabrication process and structural design of the electrode.Emerging applications of energy-storage MLCCs are then discussed in terms of advanced pulsed power sources and high-density power converters from a theoretical and technological point of view.Finally,the challenges and future prospects for industrialization of lab-scale lead-free energy-storage MLCCs are discussed.
基金Financial support from the National Natural Science Foundation of China(Grant No.51272009)is sincerely acknowledged.
文摘ZrB_(2)-SiBCN ceramics with ZrO_(2) additive are hot-pressed under a constant applied pressure.The densification behavior of the composites is studied in a view of creep deformation by means of the Bernard-Granger and Guizard model.With determination of the stress exponent(n)and the apparent activation energy(Q_(d)),the specific deformation mechanisms controlling densification are supposed.Within lower temperature ranges of 1300-1400℃,the operative mechanism is considered to be grain boundary sliding accommodated by atom diffusion of the polymer-derived SiBCN(n=1,Q_(d)=123±5 kJ/mol)and by viscous flow of the amorphous SiBCN(n=2,Qd=249±5 kJ/mol).At higher temperatures,the controlling mechanism transforms to lattice or intra-granular diffusion creep(n=3-5)due to gradual consumption of the amorphous phase.It is suggested that diffusion of oxygen ions inside ZrO_(2) into the amorphous SiBCN decreases the viscosity,modifies the fluidity,and contributes to the grain boundary mobility.
基金supported by the National Natural Science Foundation of China (No. 51572112)the National Key R&D Program of China (No. 2017YFB0310400)+3 种基金the 333 Talents Project (No. BRA2017387)Six Talent Peaks Project (No. TD-XCL-004)Innovation/Entrepreneurship Program ([2015]26)Qing Lan Project ([2016]15) of Jiangsu Province
文摘Silicon carbide(SiC) has been widely concerned for its excellent overall mechanical and physical properties, such as low density, good thermal-shock behavior, high temperature oxidation resistance, and radiation resistance; as a result, the SiC-based materials have been or are being widely used in most advanced fields involving aerospace, aviation, military, and nuclear power. Joining of SiC-based materials(monolithic SiC and SiCf/SiC composites) can resolve the problems on poor processing performance and difficulty of fabrication of large-sized and complex-shaped components to a certain extent, which are originated from their high inherent brittleness and low impact toughness.Starting from the introduction to SiC-based materials, joining of ceramics, and joint strength characterization, the joining of SiC-based materials is reviewed by classifying the as-received interlayer materials, involving no interlayer, metallic, glass-ceramic, and organic interlayers. In particular, joining processes(involving joining techniques and parameter conditions), joint strength,interfacial microstructures, and/or reaction products are highlighted for understanding interfacial behavior and for supporting development of application-oriented joining techniques.
文摘The influence of adding Fe_(2)O_(3) at the expense of Na_(2)O in sodium lead borate glasses on the structural,physical and electrical properties have been investigated.Results obtained from Fourier transform infrared(FTIR)spectra indicated that Fe_(2)O_(3) plays an important role in converting three coordinated boron atoms[BO_(3)]to four coordinated boron atoms[BO4].The physical properties such as density and molar volume helped to evaluate the compact structure of the prepared glass samples due to presence of[BO4]groups.The increase of Fe_(2)O_(3)/Na_(2)O replacements led to increasing the microhardness values and decreasing the thermal expansion coefficients of the studied glasses.The increase of Fe_(2)O_(3)/Na_(2)O replacements generally decreased the AC conductivity.That decrease might be due to converting of the three coordinated boron atoms[BO_(3)]to four coordinated boron atoms[BO_(4)].Dielectric constants of the samples might be an indication of the distortion in the coordinated boron atoms.The obtained experimental data indicated the internal structure of glass network and the change of the structure of the samples from three[BO_(3)]to four coordinated boron atoms[BO4].
基金We thank the Board of Research in Fusion Science and Technology(BRFST),Institute for Plasma Research Gandhinagar,India for financial support of the research(Grant No.NFP/MAT/F10/01).
文摘Lithium titanate(Li_(2)TiO_(3))is one of the most promising candidates among the tritium breeding materials because of its good tritium release capacity.Li concentration has much significance on the diffusivity of tritium in the material.The nanocrystalline single-phase Li_(2)TiO_(3) with monoclinic structure has been prepared by high energy ball milling followed by calcination at 700℃for 2 h.The field emission scanning electron microscopy(FESEM)studies confirmed uniform distribution of nanocrystalline phase with particle size below 100 nm.The study of the Li^(+)ion diffusion on the sintered sample was investigated by means of electrical conductivity measurements.Electrical properties of the samples were studied in wide temperature(50-500℃)and frequency(100 Hz-1 MHz)ranges.The complex impedance spectroscopy(CIS)studies showed the presence of both bulk and grain boundary effects in nanocrystalline Li_(2)TiO_(3).The bulk resistance of the samples has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance(NTCR)behavior.The low activation energies of the samples suggested the presence of singly ionized oxygen vacancies in the conduction process.The hopping frequency shifted toward higher frequency with increase in temperature.Activation energy of 0.86 eV was calculated from AC conductivity.
基金supported by the National Natural Science Foundation of China(GrantNos.52072150 and 51972146)Shandong Province Key Fundamental Research Program(Grant No.ZR2022ZD39)+1 种基金State Key Laboratory of New Ceramics and Fine Processing,Tsinghua University(Grant No.KF202002)Open Foundation of Guangdong Key Laboratory of Electronic Functional Materials andDevices(Grant No.EFMD2021002Z).
文摘Multilayer ceramic actuator(MLCA)has been widely employed in actuators due to the large cumulative displacement under the low driving voltage.In this work,the MLCA devices consisting of a lead-free MnCO_(3-)and CuO-doped 0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Ta_(0.04))O_(3)-0.04CaZrO_(3) piezoelectric ceramics and a base nickel(Ni)metal inner electrode were well co-fired by the two-step sintering process in a reducing atmosphere.The ceramic layer/electrode interface is well-integrated and clearly continuous without distinct interdiffusion and chemical reaction,which is beneficial to the electrical reliability of the MLCA.As a result,the MLCA laminated with nine active ceramic layers obtains an ultrahigh piezoelectric coefficient d_(33) of 3157 pC/N,about 9 times than bulk ceramics.The 0.5 mm-thick MLCA composed of a series of~50μm-thick ceramic layers and~3μm-thick Ni electrodes reaches a high 1.8μm displacement under the low applied voltage of 200 V(the same displacement requires a voltage as high as 3700 V for~1 mm-thick bulk ceramics).The excellent electrical performance and low-cost base electrode reveal that the(K,Na)NbO_(3)(KNN)-based MLCAs are promising lead-free candidate for actuator application.
文摘1 Manuscript submissionLegal requirementsSubmission of a manuscript implies:that the work described has not been published before;that it is not underconsideration for publication anywhere else;that its publication has been approved by all co-authors,if any,as wellas by the responsible authorities--tacitly or explicitly--at the institute where the work has been carried out.Thepublisher will not be held legally responsible should there be any claims for compensation.
基金The authors acknowledge the financial support provided by the Science,Technology,and Innovation Commission of Shenzhen Municipality(JCYJ20180508151856806)the Key R&D Program of Shaanxi(2019ZDLGY04-05)+1 种基金the National Natural Science Foundation of Shaanxi Province(2019JLZ-01)the Fundamental Research Funds for the Central Universities(19GH020302,3102019JC005,3102021ZD0401,and 3102021TS0406).
文摘High-entropy oxides(HEOs)are a new class of emerging materials with fascinating properties(such as structural stability,tensile strength,and corrosion resistance).High-entropy oxide coated Ni-rich cathode materials have great potential to improve the electrochemical performance.Here,we present a facile self-ball milling method to obtain(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Zr_(2)O_(7)(HEO)coated LiNi_(0.8)Co_(_(0.1))Mn_(_(0.1))O_(2)(NCM811).The HEO coating endows NCM811 with a stable surface,reduces the contact with the external environment(air and electrolyte),and inhibits side reactions between cathode and electrolyte.These favorable effects,especially when the coating amount is 5 wt%,result in a significant reduction of the battery polarization and an increase in the capacity retention from 57.3%(NCM811)to 74.2%(5HEO-NCM811)after 300 cycles at 1 C(1 C=200 mA·h·g^(−1)).Moreover,the morphology and spectroscopy analysis after the cycles confirmed the inhibitory effect of the HEO coating on electrolyte decomposition,which is important for the cycle life.Surprisingly,HEO coating reduces the viscosity of slurry by 37%–38%and significantly improves the flowability of the slurry with high solid content.This strategy confirms the feasibility of HEO-modified Ni-rich cathode materials and provides a new idea for the design of high-performance cathode materials for Li-ion batteries.
基金supported by the National Science Fund for Distinguished Young Scholars(No.52025041)the National Natural Science Foundation of China(Nos.51974021,51902020,and 51904021)+3 种基金the Fundamental Research Funds for the Central Universities(Nos.FRF-TP-18-045Al and FRF-TP-19-004B2Z)the National Postdoctoral Program for Innovative Talents(No.BX20180034)China Postdoctoral Science Foundation(No.2018M641192)the Open Foundation of Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured Materials,Guangxi University(No.2021GXYSOF12).
文摘In this work,gold nanoparticles(AuNPs)decorated Ti_(3)C_(2)T_(x) nanosheets(MXene/AuNPs composite)are fabricated through a self-reduction reaction of Ti_(3)C_(2)T_(x) nanosheets with HAuCl_(4) aqueous solution.The obtained composite is characterized as AuNPs with the diameter of about 23 nm uniformly dispersing on nanosheets without aggregation.The composite(MXene decorated on 4.8 wt% AuNPs)is further employed to construct supercapacitor for the first time with a higher specific capacitance of 278 F·g^(-1) at 5 mV·s^(-1) than that of pure Ti_(3)C_(2)T_(x) and 95% of cyclic stability after 10,000 cycles.Furthermore,MXene/AuNPs composite symmetric supercapacitor with filter paper as separator and H_(2)SO_(4) as electrolyte,is assembled.The supercapacitor exhibits a high volumetric energy density of 8.82 Wh·L^(-1) at a power density of 264.6 W·L^(-1) and ultrafast-charging/discharging performance.It exhibits as a promising candidate applied in integrated and flexible supercapacitors.
基金the Shenzhen Science and Technology Projects(No.JCYJ20180306172957494)National Natural Science Foundation of China(No.5187224)for financial support.
文摘Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes.To address these issues,we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny silicon particles as the core assisted by small amount of SiC.Skillfully exploiting the high heat from magnesiothermic reduction,SiC can assist the good dispersion of silicon and provide good interface compatibility and chemical stability.The silicon anchored to the carbon shell provides multipoint contact mode,that together with the carbon shell frame,significantly promoting the transfer of dual charge.Besides,the pomegranate-type microcluster structure also improves the tap density of the electrode,reduces the direct contact area between active material and electrolyte,and enhances the electrochemical performance.
基金supported by research fund for the China Postdoctoral Science Foundation(2016M600201,2018T110214,2016M601304)National Natural Science Foundation of China(51805069)+1 种基金Natural Science Foundation of Liaoning Province,China(20170540154)Aviation Science Foundation of China(2016ZF63007).
文摘Self-toughening ZrB2–SiC based composites are fabricated by in-situ reactive hot pressing.The effect of sintering additive content on the microstructure and mechanical properties of the composites is investigated.Microstructure observation found that the in-situ reactive hot pressing could promote the anisotropic growth of ZrB2 grains and the formation of interlocking microstructure.Such microstructure could improve the mechanical properties,especially,for the fracture toughness.The improved mechanical properties could be attributed to the self-toughening structure related to the ZrB2 platelets and the formed interlocking microstructure,which could trigger various toughening mechanisms such as grain pull-out,crack bridging,crack deflection,and crack branching,providing the main contribution to the high fracture toughness.
基金the Shanghai Institute of Ceramics and Chinese Academy of Sciences for support
文摘To quantify the oxygen content in molten salts, we examined the performance of an yttria-stabilized zirconia solid electrolyte oxygen sensor with a Bi/Bi_2O_3 reference electrode, focusing on its output accuracy. When the above sensor was tested in a flow of gas with known oxygen partial pressure, pO_2, a linear relationship between lgpO_2 and the electromotive force(EMF) was observed, and the correlation slope exhibited a positive deviation from Nernstian behavior. EMF measurements performed in molten NaCl–KCl indicated that the oxygen content of this salt mixture increased with increasing oxygen partial pressure in the covering gas, in agreement with Henry's law. Moreover, the EMF exhibited a linear decrease with increasing melt temperature of molten NaCl–KCl, in agreement with the theoretical model. Finally, a relationship between the structure of molten NaCl–KCl and its oxygen diffusion behavior was established. As a result, the developed sensor was demonstrated to be well suited for determining the oxygen content of molten salts.
基金Financial supports of the National Natural Science Foundation of China，the Natural Science Foundation of Guangxi (Grant No.2014GXNSFBA118254) are gratefully acknowledged by the authors
