A series of high-entropy ceramics with the nominal composition(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)(0≤x≤0.4)has been successfully synthesized using the conventional solid-phase method.T...A series of high-entropy ceramics with the nominal composition(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)(0≤x≤0.4)has been successfully synthesized using the conventional solid-phase method.The(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics are confirmed to be composed of the main phase(Zn,Mg,Li)TiO_(3)and the secondary phase Ca_(0.5)Sr_(0.5)TiO_(3)by X-ray diffractometer,Rietveld refinement,and X-ray spectroscopy analysis.The quality factor(Q×f)of the samples is inversely proportional to the content of the Ca_(0.5)Sr_(0.5)TiO_(3)phase,and it is influenced by the density.The secondary phase and molecular polarizability(α_(T))have a significant impact on the dielectric constant(ε_(r))of the samples.Moreover,the temperature coefficient of resonant frequency(τ_(f))of the samples is determined by the distortion of[TiO_(6)]octahedra and the secondary phase.The results indicate tha(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics achieve ideal microwave dielectric properties(ε_(r)=17.6,Q×f=40900 GHz,τ_(f)=-8.6 ppm/℃)when x=0.35.(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics possess the potential for application in wireless communication,and a new approach has been provided to enhance the perform-ance of microwave dielectric ceramics.展开更多
Over the past several decades,much research effort has been dedicated to the study of optical windows,with two primary themes emerging as key focuses.The first of these centers on investigating the optical properties ...Over the past several decades,much research effort has been dedicated to the study of optical windows,with two primary themes emerging as key focuses.The first of these centers on investigating the optical properties of typical transparent single crystals under shock or ramp compression,which helps in the selection of appropriate optical windows for high-pressure experiments.The second involves the exploration of novel optical windows,particularly transparent polycrystalline ceramics,which not only match the shock impedance of the samples,but also preserve transparency under dynamic compression.In this study,we first integrate existing research on the evolution of optical properties in transparent single crystals and polycrystalline ceramics subjected to shock or ramp loading,proposing a mechanism that links mesoscopic damage to macroscopic optical transparency.Subsequently,through a systematic integration of experiments and computational analyses on polycrystalline transparent ceramics,we demonstrate that shock transparency can be enhanced by optimizing grain size and that shock impedance can be designed via compositional tuning.Notably,our results reveal that nano-grained MgAl_(2)O_(4) ceramics exhibit outstanding optical transparency under high shock pressures,highlighting a promising strategy for designing optical windows that retain transparency under extreme dynamic loading conditions.展开更多
Combined pulsed laser(CPL),introduced in 1975 for target damage,integrates different lasers to achieve high peak power and pulse energy.However,despite decades of research,CPL remains unused for long-range target dama...Combined pulsed laser(CPL),introduced in 1975 for target damage,integrates different lasers to achieve high peak power and pulse energy.However,despite decades of research,CPL remains unused for long-range target damage due to the challenge of maintaining high peak power density over long distances.We note that a potential solution lies in leveraging the air filament generated by femtosecond laser,which can transmit peak power densities higher than 1014 W/cm^(2)under the power clamping effect.To address this,a concept of a femtosecond laser induced air filament-CW CPL for surface damage of ceramics was introduced.We found no surface changes in ceramic targets when irradiated with a CW laser alone.By way of contrast,the target can be penetrated in a very short time(20 ms)with the assistance of the femtosecond laser induced air filament.In this context,we employ high-speed shadow imaging,cross-timescale simulation models and macro-microscopic characterization,to elucidate the CPL damage mechanism.The optimal CPL,combining a 1 mJ femtosecond laser and a 500 W CW laser,yields a damage rate of 1.51×10^(7)μm^(3)/J,representing an improvement of approximately 175%compared to single femtosecond laser ablation and around 59%enhancement compared to coating-assisted CW laser ablation.Furthermore,the efficacy of the proposed femtosecond-CW CPL method is demonstrated in causing penetration damage of ceramic/metal composite material or direct damage of sapphire,showcasing its versatility in damaging applications.Consequently,the femtosecond-CW CPL ablation method presented in this paper holds great promise as a new type of damage method for transparent hard and brittle materials.展开更多
Piezoelectric ceramic materials are important components of piezoelectric buzzers,where the parameter of inverse piezoelectric coefficient(d_(33)^(*))plays a decisive role in the performance of the buzzer.Here,we repo...Piezoelectric ceramic materials are important components of piezoelectric buzzers,where the parameter of inverse piezoelectric coefficient(d_(33)^(*))plays a decisive role in the performance of the buzzer.Here,we report the manufacture and performance of a lead-free ceramic-based(0.96(K_(0.5)Na_(0.5))(Nb_(0.96)Sb_(0.04))O_(3)-0.04(Bi_(0.5)Na_(0.5))ZrO_(3)-1 mol%Al_(2)O_(3),abbreviated as KNNS-BNZ-1 mol%Al_(2)O_(3))piezoelectric buzzer and compare it with commercial(PbZr_(0.5)Ti_(0.5)O_(3),abbreviated as PZT)ceramics.Briefly,KNN-based ceramics have a typical perovskite structure and piezoelectric properties of d_(33)=480 pC/N,k_(p)=0.62 and d_(33)^(*)=830 pm/V,compared to d_(33)=500 pC/N,k_(p)=0.6 and d_(33)^(*)=918 pm/V of the commercial PZT-4 ceramics.Our results show that the KNNS-BNZ-1 mol%Al_(2)O_(3)ceramics have a similar sound pressure level performance over the testing frequency range to commercial PZT ceramics(which is even better in the 3-4 kHz range).These findings highlight the great application potential of KNN-based piezoelectric ceramics.展开更多
Thermal and mechanical properties of yttrium tantalate(YTaO_(4)),a top coat ceramic of thermal barrier coatings(TBCs)for aeroengines,are enhanced by synthesizing Y_(1-x)Ta_(1-x)M_(2x)O_(4)(M=Ti,Zr,Hf;x=0.06,0.12,0.18,...Thermal and mechanical properties of yttrium tantalate(YTaO_(4)),a top coat ceramic of thermal barrier coatings(TBCs)for aeroengines,are enhanced by synthesizing Y_(1-x)Ta_(1-x)M_(2x)O_(4)(M=Ti,Zr,Hf;x=0.06,0.12,0.18,0.24)medium-entropy ceramics(MECs)using a two-step sintering method.In addition,the thermal conductivity,thermal expansion coefficients(TECs),and fracture toughness of MECs were investigated.An X-ray diffraction study revealed that the Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs were monoclinic,and the Ti,Zr,and Hf doping elements replaced Y and Ta.The variations in atomic weights and ionic radii led to disturbed atomic arrangements and severe lattice distortions,resulting in improving the phonon scattering and reduced thermal conductivity,with Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)exhibiting the lowest thermal conductivity of 1.23 W·m^(-1)·K^(-1)at 900℃.The introduction of MO_(2) increased the configurational entropy and weakened the ionic bonding energy,obtaining high TECs(10.4×10^(-6)K^(-1)at 1400℃).The reduction in the monoclinic angle β lowered the ferroelastic domain inversion energy barrier.Moreover,microcracks and crack extension toughening endowed Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)with the highest fracture toughness of(4.1±0.5)MPa·m~(1/2).The simultaneous improvement of the thermal and mechanical properties of the MO_(2)(M=Ti,Zr,Hf)co-doped YTaO_(4) MECs can be extended to other materials.展开更多
With rapid advancements in physics and particle medicine,the domestic accelerator industry has grown rapidly.During the 12th Five-Year Plan period,the Institute of Modern Physics of the Chinese Academy of Sciences too...With rapid advancements in physics and particle medicine,the domestic accelerator industry has grown rapidly.During the 12th Five-Year Plan period,the Institute of Modern Physics of the Chinese Academy of Sciences took on a plurality of accelerator projects.Nevertheless,the stability of the coupler,a crucial system within the cavities of accelerators,has encountered certain difficulties.The alumina ceramics,which constitute the core component of the coupler,are increasingly prone to breakage and solder joint failures due to their inferior environmental adaptability,inadequate mechanical properties,and high gas emissions.Conversely,with the advancements in medical technology and materials science,zirconia ceramics have emerged as a prospective remedy for these problems.This type of ceramic is highly esteemed for its outstanding environmental adaptability,remarkable mechanical properties,and excellent high-temperature resistance,exhibiting extraordinary value in dental applications.This study investigates the use of zirconia ceramics in a 162.5 MHz 3-1/8"standard ceramic window,combining experimental data with finite element RF simulations and multi-physics analysis.A new coupler featuring a zirconia ceramic window was tested on a Quarter-Wave Resonator,demonstrating excellent alignment between electromagnetic simulations and measurement results.This reveals the substantial application potential and practical worth of the zirconia ceramic material in the context of accelerators.展开更多
The structural phase transitions and ferroelectric dynamics of lead-free AgNbO_(3)have attracted consid-erable attention owing to their potential in energy-storage device applications.Here,we examine the impact of Li+...The structural phase transitions and ferroelectric dynamics of lead-free AgNbO_(3)have attracted consid-erable attention owing to their potential in energy-storage device applications.Here,we examine the impact of Li+doping on the phase transitions and polarization behavior of(Ag_(1-x)Li_(x))NbO_(3)(x=0-7%)ceramics through comprehensive dielectric and ferroelectric analyses.Rietveld refinement reveals a Li+-induced phase transition from Pbcm to R3c,with x=5%and x=6%compositions near the morphotropic phase boundary(MPB).Dielectric anomalies identify key characteristic temperatures,supporting the con-struction of a low-field phase diagram.High-field studies uncover a direct relationship between phase structure and polarization behavior,culminating in a high-field phase diagram.Near-MPB compositions exhibit distinct structural states,elucidating the mechanisms of reversible and irreversible phase transi-tions.This work provides a comprehensive explanation of the evolution of hysteresis loop profiles,capturing their progression from double hysteresis loops to square loops and their subsequent reversion to double loops under varying electric field and temperature conditions.These temperature-composition(T-x)and temperature-electric field(T-E)phase diagrams provide a robust framework for understanding phase evolution,offering critical insights into optimizing AgNbO_(3)-based ceramics for advanced functional applications.展开更多
Zirconia(ZrO_(2))ceramic material has been widely applied to various fields due to its unique properties of high strength,high hardness,and excessive temperature resistance.However,the high-quality micro-hole machinin...Zirconia(ZrO_(2))ceramic material has been widely applied to various fields due to its unique properties of high strength,high hardness,and excessive temperature resistance.However,the high-quality micro-hole machining of zirconia ceramic material remains a significant challenge at present.In this study,experiments on peck drilling of 0.2 mm and 0.5 mm micro-holes in zirconia ceramics using diamond-coated drills are conducted.The characteristics of the force signal during the drilling process,the influence of drilling parameters on the drlling force and the chipping size at the hole exit,and features of the tool wear stages of the diamond coated drill are analyzed.Experimental results suggest that when machining micro-holes in zirconia ceramics,there is a positive correlation between the axial force and the size of the chipping at the exit.The axial force increases with the increase of the feed rate and the step distance,and it shows a trend of first increasing and next decreasing with the increase of the spindle speed.The wear of the drll bit has a significant impact on the quality of the hole exit.It is found that with the continuous drilling of seven holes,the axial force increases by 144.2%,and the size of edge chipping at the exit increases from about 20μm to more than 130μm.This study can provide some valuable references for improving the micro-hole processing quality of material.展开更多
High-entropy carbide ceramics(HECCs)exhibit superior properties compared to their constituent bi-nary compounds.However,high synthesis and sintering temperature are main obstacles that limit their widespread applicati...High-entropy carbide ceramics(HECCs)exhibit superior properties compared to their constituent bi-nary compounds.However,high synthesis and sintering temperature are main obstacles that limit their widespread applications.To address this issue,compositional and particle size controllable high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb02Ta_(0.2))C_(x) powders were successfully prepared by a sugar hydrogel combined with the carbothermal reduction method.Owing to the introduction of carbon vacancy,the temperature for the formation of single-phase solid solution of the high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(x) powders was decreased,and the addition of nitrogen decreased the densification temperature of the high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(0.95) ceramic by 200℃.In addition,the flexural strength and fracture toughness of the high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(0.95) ceramic were improved by 29%and 30%,respectively,compared with those without nitrogen doping.Atomic-resolution high angle annular dark field scanning transmission electron microscopy(HAADF-STEM)and energy dispersive spectroscopy(EDS)mapping re-veal that the segregation of N and small cation Ti as well as large lattice strains are responsible for the enhanced mechanical properties.Furthermore,with the introduction of nitrogen,the onset oxidation tem-perature(OOT)was increased,while the parabolic oxidation rate constant was decreased,revealing the beneficial effect of nitrogen doping on oxidation resistance.These results demonstrate that nitrogen dop-ing can not only improve the mechanical properties of HECCs but also enhance the oxidation resistance,which paves the way for the wide application of HECCs.展开更多
Outstanding electric performance can be achieved in the textured ceramics.Therefore,the Ba_(0.85)Ca_(0.15)Zr_(0.09)Ti_(0.91)O_(3)(BCZT)lead-free piezoceramics with high texture degree(f)in<001>direction were suc...Outstanding electric performance can be achieved in the textured ceramics.Therefore,the Ba_(0.85)Ca_(0.15)Zr_(0.09)Ti_(0.91)O_(3)(BCZT)lead-free piezoceramics with high texture degree(f)in<001>direction were successfully prepared using template grain growth method.On account of the perfect sheet BaTiO3(BT)templates,a texture degree as high as 97.9%for BCZT-3.0 wt%BT ceramics was obtained.The ceramics system exhibited excellent comprehensive electrical properties(d_(33)~575 pCN^(-1),k_(p)~0.61,T_(C)~89℃ε_(r)(20℃)~3002,tanδ~4.18%,P_(r)~10.91μC cm^(-2),E_(C)~2.20 kV cm^(-1)).The superior performance originated from the coexistence of rhombohedralorthorhombic-tetragonal phases(R-O-T),as well as high textured degree.The multiphase coexistence was attributed to the composition design.This work provides a theoretical basis for designing lead-free piezoceramics with excellent properties in the future.展开更多
In this work,the rare-earth doped ternary lead zirconate titanate ceramics with chemical formula of[0.3 Pb(Zn_(1/3)Nb_(2/3))O_(3)-0.7Pb(Zr_(0.52)Ti_(0.48))O_(3)]+x wt%CeO_(2)(x=0-0.5,abbreviated as 0.3PZN-0.7PZT-xCe)w...In this work,the rare-earth doped ternary lead zirconate titanate ceramics with chemical formula of[0.3 Pb(Zn_(1/3)Nb_(2/3))O_(3)-0.7Pb(Zr_(0.52)Ti_(0.48))O_(3)]+x wt%CeO_(2)(x=0-0.5,abbreviated as 0.3PZN-0.7PZT-xCe)were synthesized by a conventional solid-state reaction route,specific attentions was focused on the effects of CeO_(2)dopants on the structures and electrical properties of the 0.3PZN-0.7PZT ceramics,revealing the role conve rsion of CeO_(2)dopants with its doping amount(x).When less CeO_(2)(x≤0.2)is introduced into 0.3PZN-0.7PZT,the prepared ceramics are identified as the coexistence of rhombohedral and tetragonal phases,also involved with an increased grain size and a reduced atomic ratio of Pb/(Zr+Ti+Zn+Nb).The increased remanent polarization(Pr)and deceased coercive filed(Ec),as well as improved dielectric permittivity(er)and piezoelectric coefficient(d_(33))de monstrate the donor substitution of Ce^(3+)for Pb^(2+)at the A-site of perovskite lattice.Conversely,the introduction of excessive CeO_(2)(x>0.2)causes a reversal evolution in the electrical properties of ceramics,suggesting that some of the introduced cerium element tends to become Ce4+,which equivalently substitutes for Zr^(4+)at the B-site.Additionally,the diffused phase transition(DPT)behaviors of the 0.3PZN-0.7PZT-xCe ceramics were investigated by the modified Curie-Weiss Law.The sample with x=0.2 shows reduced DPT character and optimized electrical properties,including TC=297℃,εr=1400,d_(33)=480 pC/N,tanδ=1.6%,kp=65%,d_(33)·g_(33)=16.32×10^(-12)m^(2)/N,Pr=38.3μC/cm^(2)and Ec=1.02 kV/mm.These enhanced electrical properties not only are contributed by the donor substitution effect of Ce^(3+),but also benefit from the optimized morphotropic phase boundary that is close to the tetragonal-rich side.展开更多
In the background of carbon neutrality,monolithic ceramic catalysts are universally used in energy conversion and chemical catalysis due to the high heat and mass transfer efficiencies,low bed pressures,and scalabilit...In the background of carbon neutrality,monolithic ceramic catalysts are universally used in energy conversion and chemical catalysis due to the high heat and mass transfer efficiencies,low bed pressures,and scalability through modular design.However,traditional manufacturing processes are limited by mold dependence,organic solvent toxicity,and insufficient molding capability for complex structures,resulting in difficulty achieving precise regulation of cross-scale pores.Additive manufacturing(AM)technology employs a digital layered molding strategy to achieve the cross-scale structural regulation of catalysts from macroscopic flow channels to mesopores and micropores.This paper summarizes recent advances in the structural design of monolithic catalysts enabled by AM technologies and highlights their emerging applications in catalytic processes.Structurally,AM-fabricated monoliths have been effectively employed in key chemical reactions such as fuel reforming,CO_(2)conversion,biofuel synthesis.Strategies such as geometrical topology optimization,multi-scale pore synergy,biomimetic structural design,and functional gradient integration have been utilized to enhance heat and mass transport,reduce pressure drops,and improve overall catalytic performance.By overcoming the limitations of traditional catalysts,AM technologies create a new paradigm for addressing the longstanding challenge of coupling mass transfer with reaction kinetics.This approach provides a feasible pathway for driving both theoretical innovation and practical implementation of high-efficiency catalytic systems.展开更多
A series of single-phase high-entropy perovskite ceramics(HEPCs)(La_(0.25)Nd_(0.25)Sm_(0.25)Gd_(0.25))_(1-x)Yb_(x)MnO_(3)(x=0.25,0.3,0.35 and 0.4)was synthesized using solid-state reactions.The effect of Yb on the str...A series of single-phase high-entropy perovskite ceramics(HEPCs)(La_(0.25)Nd_(0.25)Sm_(0.25)Gd_(0.25))_(1-x)Yb_(x)MnO_(3)(x=0.25,0.3,0.35 and 0.4)was synthesized using solid-state reactions.The effect of Yb on the structure and magnetic properties was systematically investigated.The results show that all samples are in orthorhombic perovskite structures with a space group of Pbnm and exhibit a strong crystallization trend sintered at 1300℃for 16 h.All HEPCs have a smooth surface morphology with distinct grain boundaries and exhibit significant hysteresis effects at T=5 K.With the increase of Yb,high lattice distortion and weak double exchange lead to the decrease of T_(C).The presence of Jahn-Teller(JT)distortion and the enhancement of MnO_(6)octahedral distortion result in different magnetic interactions.Moreover,the sample has the best magnetic properties at x=0.35 among the four HEPCs,which is attributed to the large content of Mn^(3+),remnant ratio(Mr/Ms)and lattice distortion(σ^(2)).This work provides a valuable reference for regulating the magnetism of high-entropy ceramics based on rare-earth perovskite manganese oxides.展开更多
Silicon carbide(SiC)ceramics are extensively utilized in aerospace,national defense,and petrochemical industries due to their superior physical and chemical properties.The processing of bulk SiC ceramics necessitates ...Silicon carbide(SiC)ceramics are extensively utilized in aerospace,national defense,and petrochemical industries due to their superior physical and chemical properties.The processing of bulk SiC ceramics necessitates precise and efficient grinding techniques to produce components with satisfactory functionality.However,the inherent high hardness and brittleness of SiC ceramics present significant challenges during grinding,leading to severe brittle fracture and tool wear that compromise both surface integrity and production efficiency.Although ductile-regime grinding of SiC ceramics can be achieved by enhancing machine tool accuracy and stiffness while optimizing wheel performance alongside appropriate selection of process parameters,a comprehensive summary of the mechanisms underlying damage evolution during grinding is lacking,and a mature grinding process for SiC ceramics has yet to be developed.To bridge this gap,the sintering technologies,mechanical properties,and microstructures of SiC ceramics were briefly covered.The grinding-induced damage mechanism and low-damage grinding technologies of SiC ceramics were summarized.The fundamental science underlying the ductile deformation and removal mechanisms of brittle solids was emphasized.Additionally,attention was directed towards the critical role of hybrid energy field grinding in minimizing brittle damages and promoting removal efficiency.This review not only elucidates the intrinsic interactions between the work material and abrasives,but also offers valuable insights for optimizing the grinding processes of brittle solids.展开更多
Dielectric materials are essential in modern electronics,serving as the backbone of numerous components across a wide array of electronic devices[1,2].As technology advances,the demand for materials with high permitti...Dielectric materials are essential in modern electronics,serving as the backbone of numerous components across a wide array of electronic devices[1,2].As technology advances,the demand for materials with high permittivity,low dielectric loss,and thermal stability continues to rise.Traditional strategies to enhance permittivity often involve mechanisms such as phase transitions in ferroelectrics or interfacial polarization in boundary layer capacitor(IBLC)systems.However,each comes with trade-offs.展开更多
The hardening mechanism of multi-component carbide ceramic has been investigated in detail through a combination of experiments,first-principles calculations,and ab initio molecular dynamics(AIMD).Eight dense carbide ...The hardening mechanism of multi-component carbide ceramic has been investigated in detail through a combination of experiments,first-principles calculations,and ab initio molecular dynamics(AIMD).Eight dense carbide ceramics were prepared by spark plasma sintering.Compulsorily,all the multi-component carbide samples have similar carbon content,grain size,and uniform compositional distribution by optimizing the sintering process and adjusting the initial raw materials.Hence the interference of other factors on the hardness of multi-component carbide ceramics is minimized.The effects of changes in the elemental species on the lattice distortion,bond strength,bonding properties,and electronic structure of multi-component carbide ceramics were thoroughly analyzed.These results show that the hardening of multi-component carbide ceramic can be attributed to the coupling of solid solution strengthening caused by lattice distortion and covalent bond strengthening.Besides,the“host lattice”of multi-component carbide ceramics is defined based on the concept of supporting lattice.The present work is of great significance for a deeper understanding of the hardening mechanism of multi-component carbide ceramics and the design of superhard multi-component carbides.展开更多
In order to utilize coal gangue and steel slag with high added value,foamed ceramics were prepared by using coal gangue as the main raw material,and steel slag as the auxiliary raw material,adding appropriate amount o...In order to utilize coal gangue and steel slag with high added value,foamed ceramics were prepared by using coal gangue as the main raw material,and steel slag as the auxiliary raw material,adding appropriate amount of flux(talc and potassium feldspar)and foaming agent silicon carbide(SiC).The effects of the steel slag addition(equivalent replacement of coal gangue,5%,10%,15%,20%,25%,30%,and 35%,by mass)and flux addition(fixing the total addition of talc and potassium feldspar at 20 mass%,replacing potassium feldspar with talc in equal amount of 0,5%,10%,15%,and 20%,by mass)on the physical properties,microstructure and phase composition of the foamed ceramics were studied.The results show that:(1)with the increase of steel slag additions,the addition of SiO_(2) in the skeleton structure decreases,the addition of CaO,MgO and other oxides increases,and the viscosity decreases;excessive steel slag addition is not conducive to the formation of moderate-size and uniform distributed pores due to the low addition of SiO_(2);the steel slag addition shall not exceed 30%;(2)the influence of talc and potassium feldspar flux on the foamed ceramics is mainly to change the contents of alkali metal oxides,as well as Al_(2)O_(3) and SiO_(2) which constitute the ceramic skeleton;(3)the optimum foamed ceramic formulation is m(coal gangue):m(steel slag):m(potassium feldspar):m(talc)=50:30:10:10,extra-adding 0.1 mass%SiC.展开更多
The incompatibility between large electro-strain and low-strain hysteresis,in addition to the poor tem-perature stability of piezoelectric ceramics,limits the development of high-precision piezoelectric actu-ators.In ...The incompatibility between large electro-strain and low-strain hysteresis,in addition to the poor tem-perature stability of piezoelectric ceramics,limits the development of high-precision piezoelectric actu-ators.In this work,Bi_(0.465)Na_(0.465)Ba_(0.07)Ti_(1−2 x)Ga_(x)Sb_(x)O_(3)(abbreviated as BNBT7-x GS,x=0,0.01,0.02,0.03,0.04,and 0.06)ceramics were designed.Specifically,when x=0.02,the ceramics exhibit a critical state in the relaxor ferroelectric system with a typical relaxor P−E loop and an I−E curve of four peaks.At this composition,the room temperature strain is 0.40%,which is capable of enhancing the electro-strain and reducing the hysteresis simultaneously.Furthermore,over the wide temperature range from 30 to 180℃,the minimum strain hysteresis(H_(ys))is 7.13%,and the maximum strain variation is only 16.8%,demonstrating ultra-high temperature stability.This work introduces a model for addressing the dilemma between good electro-strain properties and insufficient temperature stability in lead-free piezoelectric ceramics,crucial for the development of modern high-precision actuators.展开更多
Pyroelectric sensors based on pyroelectric effect have a wide range of applications.However,the use of lead-containing materials limits their development.In this paper,Na_(0.5)Bi_(0.5)TiO_(3)-Na_(0.5)Bi_(4.5)TiO_(15)-...Pyroelectric sensors based on pyroelectric effect have a wide range of applications.However,the use of lead-containing materials limits their development.In this paper,Na_(0.5)Bi_(0.5)TiO_(3)-Na_(0.5)Bi_(4.5)TiO_(15)-Mn lead-free pyroelectric ceramics are used as sensitive materials to prepare pyroelectric sensors.Na_(0.5)Bi_(0.5)TiO_(3)-Na_(0.5)Bi_(4.5)TiO_(15)-Mn ceramics can achieve 7.58×10^(-4)C·m^(-2)·K^(-1)high-roomtemperature pyroelectric coefficient and depolarization temperature of 151℃.Due to the low dielectric constant and loss caused by Mn doping,the high detection rate value of 24.382μPa^(-1/2)is obtained.The voltage response rate and specific detection rate of the sensor prepared on this basis can attain the JC-T 2397-2017(ε_(r)>200,tanδ<5%,T_(c)>200,p>3.50×10^(-4)C·m^(-2)·K^(-1))application standard of pyroelectric infrared detectors.Thermoelectric cooler is proposed to adjust the temperature of the sensor,and its voltage response to human radiation is measured.Harnessing the superior pyroelectric attributes of advanced materials and connectable devices,the nascentthermoelectric-pyroelectric detection method is poised to be a subject of intensive investigation and development.展开更多
The growing demand for the miniaturization and multifunctionality of optoelectronic devices has promoted the development of transparent ferroelectrics.However,it is difficult for the superior multiple optical properti...The growing demand for the miniaturization and multifunctionality of optoelectronic devices has promoted the development of transparent ferroelectrics.However,it is difficult for the superior multiple optical properties of these materials to be compatible with the excellent ferroelectricity and piezoelectricity in transparent ceramics.Here,we successfully synthesized Bi/Eu codoped eco-friendly K0.5Na0.5NbO3transparent-ferroelectric ceramics with photo luminescence(PL)behavior,photochromic(PC)reactions and temperature-responsive PL.Based on the distinct optical properties of ceramics at different temperature ranges(room temperature and ultralow temperature),high utilization of multiple optical functions was realized.At room temperature,the PC behavior induced PL modulation contrast reaches 75.2%(at 592 nm),which can be applied in the optical information storage field.In the ultralow temperature range,the ceramics exhibit excellent sensitivity(with a maximum relative sensitivity of26.32%/K)via fluorescence intensity ratio technology and exhibit great application potential in noncontact optical temperature measurements.Additionally,the change in the PL intensity at different wavelengths(I_(614)/I_(592))can serve as a reliable indicator for detecting the occurrence of the phase transition from rhombohedral to orthorhombic at low temperature.This work provides a feasible paradigm for realizing the integration of ferroelectricity and multifarious optical properties in a single optoelectronic material.展开更多
基金supported by the Sichuan Science and Technology Program,China(No.2023YFQ0082)the Guangdong Provincial Key Laboratory of Electronic Functional Materials and Device,China(No.EFMD2022005Z)the State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals,China(No.SKL-SPM-202021).
文摘A series of high-entropy ceramics with the nominal composition(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)(0≤x≤0.4)has been successfully synthesized using the conventional solid-phase method.The(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics are confirmed to be composed of the main phase(Zn,Mg,Li)TiO_(3)and the secondary phase Ca_(0.5)Sr_(0.5)TiO_(3)by X-ray diffractometer,Rietveld refinement,and X-ray spectroscopy analysis.The quality factor(Q×f)of the samples is inversely proportional to the content of the Ca_(0.5)Sr_(0.5)TiO_(3)phase,and it is influenced by the density.The secondary phase and molecular polarizability(α_(T))have a significant impact on the dielectric constant(ε_(r))of the samples.Moreover,the temperature coefficient of resonant frequency(τ_(f))of the samples is determined by the distortion of[TiO_(6)]octahedra and the secondary phase.The results indicate tha(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics achieve ideal microwave dielectric properties(ε_(r)=17.6,Q×f=40900 GHz,τ_(f)=-8.6 ppm/℃)when x=0.35.(Mg_(0.5)Zn_(0.5))_(0.4+x)Li_(0.4)(Ca_(0.5)Sr_(0.5))_(0.4−x)TiO_(3)ceramics possess the potential for application in wireless communication,and a new approach has been provided to enhance the perform-ance of microwave dielectric ceramics.
基金financially supported by the National Natural Science Foundation of China(Grant No.11872344)the Innovatory Development Foundation of the China Academy of Engineering Physics(Grant No.CX20210026).
文摘Over the past several decades,much research effort has been dedicated to the study of optical windows,with two primary themes emerging as key focuses.The first of these centers on investigating the optical properties of typical transparent single crystals under shock or ramp compression,which helps in the selection of appropriate optical windows for high-pressure experiments.The second involves the exploration of novel optical windows,particularly transparent polycrystalline ceramics,which not only match the shock impedance of the samples,but also preserve transparency under dynamic compression.In this study,we first integrate existing research on the evolution of optical properties in transparent single crystals and polycrystalline ceramics subjected to shock or ramp loading,proposing a mechanism that links mesoscopic damage to macroscopic optical transparency.Subsequently,through a systematic integration of experiments and computational analyses on polycrystalline transparent ceramics,we demonstrate that shock transparency can be enhanced by optimizing grain size and that shock impedance can be designed via compositional tuning.Notably,our results reveal that nano-grained MgAl_(2)O_(4) ceramics exhibit outstanding optical transparency under high shock pressures,highlighting a promising strategy for designing optical windows that retain transparency under extreme dynamic loading conditions.
基金supports from National Natural Science Foundation of China(Grant No.52105498)The science and technology innovation Program of Hunan Province(Grant No.2021RC3074)+2 种基金Advanced Laser Technology Laboratory of Anhui Province(AHL2022KF04)National Key R&D Program of China(Grant No.2023YFB14605500)Changsha Natural Science Foundation(kq2402089).
文摘Combined pulsed laser(CPL),introduced in 1975 for target damage,integrates different lasers to achieve high peak power and pulse energy.However,despite decades of research,CPL remains unused for long-range target damage due to the challenge of maintaining high peak power density over long distances.We note that a potential solution lies in leveraging the air filament generated by femtosecond laser,which can transmit peak power densities higher than 1014 W/cm^(2)under the power clamping effect.To address this,a concept of a femtosecond laser induced air filament-CW CPL for surface damage of ceramics was introduced.We found no surface changes in ceramic targets when irradiated with a CW laser alone.By way of contrast,the target can be penetrated in a very short time(20 ms)with the assistance of the femtosecond laser induced air filament.In this context,we employ high-speed shadow imaging,cross-timescale simulation models and macro-microscopic characterization,to elucidate the CPL damage mechanism.The optimal CPL,combining a 1 mJ femtosecond laser and a 500 W CW laser,yields a damage rate of 1.51×10^(7)μm^(3)/J,representing an improvement of approximately 175%compared to single femtosecond laser ablation and around 59%enhancement compared to coating-assisted CW laser ablation.Furthermore,the efficacy of the proposed femtosecond-CW CPL method is demonstrated in causing penetration damage of ceramic/metal composite material or direct damage of sapphire,showcasing its versatility in damaging applications.Consequently,the femtosecond-CW CPL ablation method presented in this paper holds great promise as a new type of damage method for transparent hard and brittle materials.
基金Project supported by the Key Research and Develop Projects in Gansu Province(Grant No.23YFGA0002)the project funding of Audiowell Electronics(Guangdong)Co.,Ltd.
文摘Piezoelectric ceramic materials are important components of piezoelectric buzzers,where the parameter of inverse piezoelectric coefficient(d_(33)^(*))plays a decisive role in the performance of the buzzer.Here,we report the manufacture and performance of a lead-free ceramic-based(0.96(K_(0.5)Na_(0.5))(Nb_(0.96)Sb_(0.04))O_(3)-0.04(Bi_(0.5)Na_(0.5))ZrO_(3)-1 mol%Al_(2)O_(3),abbreviated as KNNS-BNZ-1 mol%Al_(2)O_(3))piezoelectric buzzer and compare it with commercial(PbZr_(0.5)Ti_(0.5)O_(3),abbreviated as PZT)ceramics.Briefly,KNN-based ceramics have a typical perovskite structure and piezoelectric properties of d_(33)=480 pC/N,k_(p)=0.62 and d_(33)^(*)=830 pm/V,compared to d_(33)=500 pC/N,k_(p)=0.6 and d_(33)^(*)=918 pm/V of the commercial PZT-4 ceramics.Our results show that the KNNS-BNZ-1 mol%Al_(2)O_(3)ceramics have a similar sound pressure level performance over the testing frequency range to commercial PZT ceramics(which is even better in the 3-4 kHz range).These findings highlight the great application potential of KNN-based piezoelectric ceramics.
文摘Thermal and mechanical properties of yttrium tantalate(YTaO_(4)),a top coat ceramic of thermal barrier coatings(TBCs)for aeroengines,are enhanced by synthesizing Y_(1-x)Ta_(1-x)M_(2x)O_(4)(M=Ti,Zr,Hf;x=0.06,0.12,0.18,0.24)medium-entropy ceramics(MECs)using a two-step sintering method.In addition,the thermal conductivity,thermal expansion coefficients(TECs),and fracture toughness of MECs were investigated.An X-ray diffraction study revealed that the Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs were monoclinic,and the Ti,Zr,and Hf doping elements replaced Y and Ta.The variations in atomic weights and ionic radii led to disturbed atomic arrangements and severe lattice distortions,resulting in improving the phonon scattering and reduced thermal conductivity,with Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)exhibiting the lowest thermal conductivity of 1.23 W·m^(-1)·K^(-1)at 900℃.The introduction of MO_(2) increased the configurational entropy and weakened the ionic bonding energy,obtaining high TECs(10.4×10^(-6)K^(-1)at 1400℃).The reduction in the monoclinic angle β lowered the ferroelastic domain inversion energy barrier.Moreover,microcracks and crack extension toughening endowed Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)with the highest fracture toughness of(4.1±0.5)MPa·m~(1/2).The simultaneous improvement of the thermal and mechanical properties of the MO_(2)(M=Ti,Zr,Hf)co-doped YTaO_(4) MECs can be extended to other materials.
文摘With rapid advancements in physics and particle medicine,the domestic accelerator industry has grown rapidly.During the 12th Five-Year Plan period,the Institute of Modern Physics of the Chinese Academy of Sciences took on a plurality of accelerator projects.Nevertheless,the stability of the coupler,a crucial system within the cavities of accelerators,has encountered certain difficulties.The alumina ceramics,which constitute the core component of the coupler,are increasingly prone to breakage and solder joint failures due to their inferior environmental adaptability,inadequate mechanical properties,and high gas emissions.Conversely,with the advancements in medical technology and materials science,zirconia ceramics have emerged as a prospective remedy for these problems.This type of ceramic is highly esteemed for its outstanding environmental adaptability,remarkable mechanical properties,and excellent high-temperature resistance,exhibiting extraordinary value in dental applications.This study investigates the use of zirconia ceramics in a 162.5 MHz 3-1/8"standard ceramic window,combining experimental data with finite element RF simulations and multi-physics analysis.A new coupler featuring a zirconia ceramic window was tested on a Quarter-Wave Resonator,demonstrating excellent alignment between electromagnetic simulations and measurement results.This reveals the substantial application potential and practical worth of the zirconia ceramic material in the context of accelerators.
基金finically supported by the National Natural Science Foundation of China(Nos.52261135548,52302153,and 52402155)the China Postdoctoral Science Foundation(Nos.GZC20232075 and 2023M742767)+2 种基金The research was made possible by Russian Science Foundation(Project No 23-42-00116)The equipment of the Ural Center for Shared Use“Modern nanotech-nology”Ural Federal University(Reg.No2968)whichis supported by the Ministry of Science and Higher Education RF(Project No 075-15-2021-677)was usedThe SEM work was done at International Center for Dielectric Research(ICDR),Xi’an Jiaotong University,Xi’an,China.
文摘The structural phase transitions and ferroelectric dynamics of lead-free AgNbO_(3)have attracted consid-erable attention owing to their potential in energy-storage device applications.Here,we examine the impact of Li+doping on the phase transitions and polarization behavior of(Ag_(1-x)Li_(x))NbO_(3)(x=0-7%)ceramics through comprehensive dielectric and ferroelectric analyses.Rietveld refinement reveals a Li+-induced phase transition from Pbcm to R3c,with x=5%and x=6%compositions near the morphotropic phase boundary(MPB).Dielectric anomalies identify key characteristic temperatures,supporting the con-struction of a low-field phase diagram.High-field studies uncover a direct relationship between phase structure and polarization behavior,culminating in a high-field phase diagram.Near-MPB compositions exhibit distinct structural states,elucidating the mechanisms of reversible and irreversible phase transi-tions.This work provides a comprehensive explanation of the evolution of hysteresis loop profiles,capturing their progression from double hysteresis loops to square loops and their subsequent reversion to double loops under varying electric field and temperature conditions.These temperature-composition(T-x)and temperature-electric field(T-E)phase diagrams provide a robust framework for understanding phase evolution,offering critical insights into optimizing AgNbO_(3)-based ceramics for advanced functional applications.
基金supported by the National Natural Science Foundation of China(Nos.51805242,52475463).
文摘Zirconia(ZrO_(2))ceramic material has been widely applied to various fields due to its unique properties of high strength,high hardness,and excessive temperature resistance.However,the high-quality micro-hole machining of zirconia ceramic material remains a significant challenge at present.In this study,experiments on peck drilling of 0.2 mm and 0.5 mm micro-holes in zirconia ceramics using diamond-coated drills are conducted.The characteristics of the force signal during the drilling process,the influence of drilling parameters on the drlling force and the chipping size at the hole exit,and features of the tool wear stages of the diamond coated drill are analyzed.Experimental results suggest that when machining micro-holes in zirconia ceramics,there is a positive correlation between the axial force and the size of the chipping at the exit.The axial force increases with the increase of the feed rate and the step distance,and it shows a trend of first increasing and next decreasing with the increase of the spindle speed.The wear of the drll bit has a significant impact on the quality of the hole exit.It is found that with the continuous drilling of seven holes,the axial force increases by 144.2%,and the size of edge chipping at the exit increases from about 20μm to more than 130μm.This study can provide some valuable references for improving the micro-hole processing quality of material.
基金supported by the National Natural Science Foundation of China(Nos.52272060,51902067,51872066 and 52002001)the Key Program of National Natural Science Foundation of China(No.52032003)+6 种基金the China Postdoctoral Sci-ence Foundation(Nos.2019M651282 and 2022T150157)the Hei-longjiang Provincial Postdoctoral Science Foundation(Nos.LBH-Z19022 and LBH-TZ2207)Heilongjiang Touyan Innovation Team Program,the Shanghai Aerospace Science and Technology Innova-tion Fund(No.SAST2019-012)the Fundamental Research Funds for the Central Universities(No.FRFCU5710051022)the Science Foundation of National Key Laboratory of Science and Tech-nology on Advanced Composites in Special Environments(No.JCKYS2022603C011)the Domestic Visiting and Studying Project for Outstanding Young Key Talents in Universities of Anhui Province(No.gxgnfx2021131)Young and Middle-aged Top Talent Project of Anhui Polytechnic University.
文摘High-entropy carbide ceramics(HECCs)exhibit superior properties compared to their constituent bi-nary compounds.However,high synthesis and sintering temperature are main obstacles that limit their widespread applications.To address this issue,compositional and particle size controllable high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb02Ta_(0.2))C_(x) powders were successfully prepared by a sugar hydrogel combined with the carbothermal reduction method.Owing to the introduction of carbon vacancy,the temperature for the formation of single-phase solid solution of the high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(x) powders was decreased,and the addition of nitrogen decreased the densification temperature of the high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(0.95) ceramic by 200℃.In addition,the flexural strength and fracture toughness of the high-entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(0.95) ceramic were improved by 29%and 30%,respectively,compared with those without nitrogen doping.Atomic-resolution high angle annular dark field scanning transmission electron microscopy(HAADF-STEM)and energy dispersive spectroscopy(EDS)mapping re-veal that the segregation of N and small cation Ti as well as large lattice strains are responsible for the enhanced mechanical properties.Furthermore,with the introduction of nitrogen,the onset oxidation tem-perature(OOT)was increased,while the parabolic oxidation rate constant was decreased,revealing the beneficial effect of nitrogen doping on oxidation resistance.These results demonstrate that nitrogen dop-ing can not only improve the mechanical properties of HECCs but also enhance the oxidation resistance,which paves the way for the wide application of HECCs.
基金financially supported by the National Natural Science Foundation of China(NSFC Nos.51862003,52472122)Guizhou Provincial Basic Research Program(Natural Science)(No.QKHJC-ZK-2023-266)+1 种基金Natural Science Project of Education Department of Guizhou Province(No.[2022]045)Guizhou University Natural Science Special(special post)Research Fund(No.(2023)17)
文摘Outstanding electric performance can be achieved in the textured ceramics.Therefore,the Ba_(0.85)Ca_(0.15)Zr_(0.09)Ti_(0.91)O_(3)(BCZT)lead-free piezoceramics with high texture degree(f)in<001>direction were successfully prepared using template grain growth method.On account of the perfect sheet BaTiO3(BT)templates,a texture degree as high as 97.9%for BCZT-3.0 wt%BT ceramics was obtained.The ceramics system exhibited excellent comprehensive electrical properties(d_(33)~575 pCN^(-1),k_(p)~0.61,T_(C)~89℃ε_(r)(20℃)~3002,tanδ~4.18%,P_(r)~10.91μC cm^(-2),E_(C)~2.20 kV cm^(-1)).The superior performance originated from the coexistence of rhombohedralorthorhombic-tetragonal phases(R-O-T),as well as high textured degree.The multiphase coexistence was attributed to the composition design.This work provides a theoretical basis for designing lead-free piezoceramics with excellent properties in the future.
基金Project supported by the Natural Science Foundation of Sichuan Province(2024NSFSC0219)。
文摘In this work,the rare-earth doped ternary lead zirconate titanate ceramics with chemical formula of[0.3 Pb(Zn_(1/3)Nb_(2/3))O_(3)-0.7Pb(Zr_(0.52)Ti_(0.48))O_(3)]+x wt%CeO_(2)(x=0-0.5,abbreviated as 0.3PZN-0.7PZT-xCe)were synthesized by a conventional solid-state reaction route,specific attentions was focused on the effects of CeO_(2)dopants on the structures and electrical properties of the 0.3PZN-0.7PZT ceramics,revealing the role conve rsion of CeO_(2)dopants with its doping amount(x).When less CeO_(2)(x≤0.2)is introduced into 0.3PZN-0.7PZT,the prepared ceramics are identified as the coexistence of rhombohedral and tetragonal phases,also involved with an increased grain size and a reduced atomic ratio of Pb/(Zr+Ti+Zn+Nb).The increased remanent polarization(Pr)and deceased coercive filed(Ec),as well as improved dielectric permittivity(er)and piezoelectric coefficient(d_(33))de monstrate the donor substitution of Ce^(3+)for Pb^(2+)at the A-site of perovskite lattice.Conversely,the introduction of excessive CeO_(2)(x>0.2)causes a reversal evolution in the electrical properties of ceramics,suggesting that some of the introduced cerium element tends to become Ce4+,which equivalently substitutes for Zr^(4+)at the B-site.Additionally,the diffused phase transition(DPT)behaviors of the 0.3PZN-0.7PZT-xCe ceramics were investigated by the modified Curie-Weiss Law.The sample with x=0.2 shows reduced DPT character and optimized electrical properties,including TC=297℃,εr=1400,d_(33)=480 pC/N,tanδ=1.6%,kp=65%,d_(33)·g_(33)=16.32×10^(-12)m^(2)/N,Pr=38.3μC/cm^(2)and Ec=1.02 kV/mm.These enhanced electrical properties not only are contributed by the donor substitution effect of Ce^(3+),but also benefit from the optimized morphotropic phase boundary that is close to the tetragonal-rich side.
基金supported by the National Natural Science Foundation of China(Grant No.52405414)the China Postdoctoral Science Foundation(Grant No.2024M762580)+1 种基金Young Talent Fund of Xi'an Association for Science and Technology(Grant No.0959202513033)the Youth Innovation Team of Shaanxi Universities,and the Fundamental Research Funds for Central Universities.The authors gratefully acknowledge the support by the Instrumental Analysis Center of Xi’an Jiaotong University for sample characterization.
文摘In the background of carbon neutrality,monolithic ceramic catalysts are universally used in energy conversion and chemical catalysis due to the high heat and mass transfer efficiencies,low bed pressures,and scalability through modular design.However,traditional manufacturing processes are limited by mold dependence,organic solvent toxicity,and insufficient molding capability for complex structures,resulting in difficulty achieving precise regulation of cross-scale pores.Additive manufacturing(AM)technology employs a digital layered molding strategy to achieve the cross-scale structural regulation of catalysts from macroscopic flow channels to mesopores and micropores.This paper summarizes recent advances in the structural design of monolithic catalysts enabled by AM technologies and highlights their emerging applications in catalytic processes.Structurally,AM-fabricated monoliths have been effectively employed in key chemical reactions such as fuel reforming,CO_(2)conversion,biofuel synthesis.Strategies such as geometrical topology optimization,multi-scale pore synergy,biomimetic structural design,and functional gradient integration have been utilized to enhance heat and mass transport,reduce pressure drops,and improve overall catalytic performance.By overcoming the limitations of traditional catalysts,AM technologies create a new paradigm for addressing the longstanding challenge of coupling mass transfer with reaction kinetics.This approach provides a feasible pathway for driving both theoretical innovation and practical implementation of high-efficiency catalytic systems.
基金Project supported by the Guangxi Natural Science Foundation,China(2024GXNSFAA010415)the Opening Fund of the Key Laboratory of New Processing Technology for Nonferrous Metals&Materials of the Ministry of Education(22AA-9)。
文摘A series of single-phase high-entropy perovskite ceramics(HEPCs)(La_(0.25)Nd_(0.25)Sm_(0.25)Gd_(0.25))_(1-x)Yb_(x)MnO_(3)(x=0.25,0.3,0.35 and 0.4)was synthesized using solid-state reactions.The effect of Yb on the structure and magnetic properties was systematically investigated.The results show that all samples are in orthorhombic perovskite structures with a space group of Pbnm and exhibit a strong crystallization trend sintered at 1300℃for 16 h.All HEPCs have a smooth surface morphology with distinct grain boundaries and exhibit significant hysteresis effects at T=5 K.With the increase of Yb,high lattice distortion and weak double exchange lead to the decrease of T_(C).The presence of Jahn-Teller(JT)distortion and the enhancement of MnO_(6)octahedral distortion result in different magnetic interactions.Moreover,the sample has the best magnetic properties at x=0.35 among the four HEPCs,which is attributed to the large content of Mn^(3+),remnant ratio(Mr/Ms)and lattice distortion(σ^(2)).This work provides a valuable reference for regulating the magnetism of high-entropy ceramics based on rare-earth perovskite manganese oxides.
基金supported by the National Natural Science Foundation of China(Grant Nos.52375420,52322510)Natural Science Foundation of Heilongjiang Province of China(Grant No.YQ2023E014)+6 种基金National Key Research and Development Program of China(Grant No.2021YFB3400403)Shenzhen Science and Technology Program(Grant No.GNCWSSJH20240032)Self-Planned Task(Grant No.SKLRS202214B)of State Key Laboratory of Robotics and System(HIT),China Postdoctoral Science Foundation(Grant No.2022T150163)Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20220463)Open Fund of Key Laboratory of Microsystems and Microstructures Manufacturing(HIT)(Grant No.2022KM004)Open Foundation of Hunan Provincial Key Laboratory of High Efficiency and Precision Machining of Difficult-to-Cut Material(Grant No.E22445)Fundamental Research Funds for the Central Universities(Grant Nos.HIT.OCEF.2022024,FRFCU5710051122)。
文摘Silicon carbide(SiC)ceramics are extensively utilized in aerospace,national defense,and petrochemical industries due to their superior physical and chemical properties.The processing of bulk SiC ceramics necessitates precise and efficient grinding techniques to produce components with satisfactory functionality.However,the inherent high hardness and brittleness of SiC ceramics present significant challenges during grinding,leading to severe brittle fracture and tool wear that compromise both surface integrity and production efficiency.Although ductile-regime grinding of SiC ceramics can be achieved by enhancing machine tool accuracy and stiffness while optimizing wheel performance alongside appropriate selection of process parameters,a comprehensive summary of the mechanisms underlying damage evolution during grinding is lacking,and a mature grinding process for SiC ceramics has yet to be developed.To bridge this gap,the sintering technologies,mechanical properties,and microstructures of SiC ceramics were briefly covered.The grinding-induced damage mechanism and low-damage grinding technologies of SiC ceramics were summarized.The fundamental science underlying the ductile deformation and removal mechanisms of brittle solids was emphasized.Additionally,attention was directed towards the critical role of hybrid energy field grinding in minimizing brittle damages and promoting removal efficiency.This review not only elucidates the intrinsic interactions between the work material and abrasives,but also offers valuable insights for optimizing the grinding processes of brittle solids.
文摘Dielectric materials are essential in modern electronics,serving as the backbone of numerous components across a wide array of electronic devices[1,2].As technology advances,the demand for materials with high permittivity,low dielectric loss,and thermal stability continues to rise.Traditional strategies to enhance permittivity often involve mechanisms such as phase transitions in ferroelectrics or interfacial polarization in boundary layer capacitor(IBLC)systems.However,each comes with trade-offs.
基金financially supported by the National Natural Science Foundation of China(Nos.52032002,52372060,51972081,and U22A20128)the National Safety Academic Foundation(No.U2130103)+1 种基金the National Key Laboratory of Precision Hot Processing of Metals(No.61429092300305)Heilongjiang Touyan Team Program are gratefully acknowledged.
文摘The hardening mechanism of multi-component carbide ceramic has been investigated in detail through a combination of experiments,first-principles calculations,and ab initio molecular dynamics(AIMD).Eight dense carbide ceramics were prepared by spark plasma sintering.Compulsorily,all the multi-component carbide samples have similar carbon content,grain size,and uniform compositional distribution by optimizing the sintering process and adjusting the initial raw materials.Hence the interference of other factors on the hardness of multi-component carbide ceramics is minimized.The effects of changes in the elemental species on the lattice distortion,bond strength,bonding properties,and electronic structure of multi-component carbide ceramics were thoroughly analyzed.These results show that the hardening of multi-component carbide ceramic can be attributed to the coupling of solid solution strengthening caused by lattice distortion and covalent bond strengthening.Besides,the“host lattice”of multi-component carbide ceramics is defined based on the concept of supporting lattice.The present work is of great significance for a deeper understanding of the hardening mechanism of multi-component carbide ceramics and the design of superhard multi-component carbides.
文摘In order to utilize coal gangue and steel slag with high added value,foamed ceramics were prepared by using coal gangue as the main raw material,and steel slag as the auxiliary raw material,adding appropriate amount of flux(talc and potassium feldspar)and foaming agent silicon carbide(SiC).The effects of the steel slag addition(equivalent replacement of coal gangue,5%,10%,15%,20%,25%,30%,and 35%,by mass)and flux addition(fixing the total addition of talc and potassium feldspar at 20 mass%,replacing potassium feldspar with talc in equal amount of 0,5%,10%,15%,and 20%,by mass)on the physical properties,microstructure and phase composition of the foamed ceramics were studied.The results show that:(1)with the increase of steel slag additions,the addition of SiO_(2) in the skeleton structure decreases,the addition of CaO,MgO and other oxides increases,and the viscosity decreases;excessive steel slag addition is not conducive to the formation of moderate-size and uniform distributed pores due to the low addition of SiO_(2);the steel slag addition shall not exceed 30%;(2)the influence of talc and potassium feldspar flux on the foamed ceramics is mainly to change the contents of alkali metal oxides,as well as Al_(2)O_(3) and SiO_(2) which constitute the ceramic skeleton;(3)the optimum foamed ceramic formulation is m(coal gangue):m(steel slag):m(potassium feldspar):m(talc)=50:30:10:10,extra-adding 0.1 mass%SiC.
基金financially supported by the National Natural Science Foundation of China(No.U2006218)the Project of“20 Items of University”of Jinan(No.T202009)the Taishan Scholars Program(No.tstp20221130).
文摘The incompatibility between large electro-strain and low-strain hysteresis,in addition to the poor tem-perature stability of piezoelectric ceramics,limits the development of high-precision piezoelectric actu-ators.In this work,Bi_(0.465)Na_(0.465)Ba_(0.07)Ti_(1−2 x)Ga_(x)Sb_(x)O_(3)(abbreviated as BNBT7-x GS,x=0,0.01,0.02,0.03,0.04,and 0.06)ceramics were designed.Specifically,when x=0.02,the ceramics exhibit a critical state in the relaxor ferroelectric system with a typical relaxor P−E loop and an I−E curve of four peaks.At this composition,the room temperature strain is 0.40%,which is capable of enhancing the electro-strain and reducing the hysteresis simultaneously.Furthermore,over the wide temperature range from 30 to 180℃,the minimum strain hysteresis(H_(ys))is 7.13%,and the maximum strain variation is only 16.8%,demonstrating ultra-high temperature stability.This work introduces a model for addressing the dilemma between good electro-strain properties and insufficient temperature stability in lead-free piezoelectric ceramics,crucial for the development of modern high-precision actuators.
基金financially supported by the National Key Research and Development Program of China(No.2023YFB4603800)
文摘Pyroelectric sensors based on pyroelectric effect have a wide range of applications.However,the use of lead-containing materials limits their development.In this paper,Na_(0.5)Bi_(0.5)TiO_(3)-Na_(0.5)Bi_(4.5)TiO_(15)-Mn lead-free pyroelectric ceramics are used as sensitive materials to prepare pyroelectric sensors.Na_(0.5)Bi_(0.5)TiO_(3)-Na_(0.5)Bi_(4.5)TiO_(15)-Mn ceramics can achieve 7.58×10^(-4)C·m^(-2)·K^(-1)high-roomtemperature pyroelectric coefficient and depolarization temperature of 151℃.Due to the low dielectric constant and loss caused by Mn doping,the high detection rate value of 24.382μPa^(-1/2)is obtained.The voltage response rate and specific detection rate of the sensor prepared on this basis can attain the JC-T 2397-2017(ε_(r)>200,tanδ<5%,T_(c)>200,p>3.50×10^(-4)C·m^(-2)·K^(-1))application standard of pyroelectric infrared detectors.Thermoelectric cooler is proposed to adjust the temperature of the sensor,and its voltage response to human radiation is measured.Harnessing the superior pyroelectric attributes of advanced materials and connectable devices,the nascentthermoelectric-pyroelectric detection method is poised to be a subject of intensive investigation and development.
基金Project supported by the National Natural Science Foundation of China(52072075,52102126,12104093)the Natural Science Foundation of Fujian Province(2021J05122,2021J05123,2022J01087,2022J01552,2023J01259)。
文摘The growing demand for the miniaturization and multifunctionality of optoelectronic devices has promoted the development of transparent ferroelectrics.However,it is difficult for the superior multiple optical properties of these materials to be compatible with the excellent ferroelectricity and piezoelectricity in transparent ceramics.Here,we successfully synthesized Bi/Eu codoped eco-friendly K0.5Na0.5NbO3transparent-ferroelectric ceramics with photo luminescence(PL)behavior,photochromic(PC)reactions and temperature-responsive PL.Based on the distinct optical properties of ceramics at different temperature ranges(room temperature and ultralow temperature),high utilization of multiple optical functions was realized.At room temperature,the PC behavior induced PL modulation contrast reaches 75.2%(at 592 nm),which can be applied in the optical information storage field.In the ultralow temperature range,the ceramics exhibit excellent sensitivity(with a maximum relative sensitivity of26.32%/K)via fluorescence intensity ratio technology and exhibit great application potential in noncontact optical temperature measurements.Additionally,the change in the PL intensity at different wavelengths(I_(614)/I_(592))can serve as a reliable indicator for detecting the occurrence of the phase transition from rhombohedral to orthorhombic at low temperature.This work provides a feasible paradigm for realizing the integration of ferroelectricity and multifarious optical properties in a single optoelectronic material.
