Ceramic thin plates were prepared using kaolin,potassium sodium feldspar and quartz powder as the main raw materials and kaolin,α-Al_(2)O_(3),MoO_(3) and AlF_(3)·3H_(2)O as additives.The experiment examined the ...Ceramic thin plates were prepared using kaolin,potassium sodium feldspar and quartz powder as the main raw materials and kaolin,α-Al_(2)O_(3),MoO_(3) and AlF_(3)·3H_(2)O as additives.The experiment examined the effects of different additives on mullite formation,as well as the microstructure and properties of the ceramic thin plates.Additionally,the study explored the toughening and strengthening mechanisms induced by the additives,providing a theoretical foundation for further optimizing the toughness of ceramic thin plates.The results showed that the D4 sample fired at 1220℃(with an addition of 20 wt% α-Al_(2)O_(3))exhibited the best performance,with a water absorption rate of 0.07%,apparent porosity of 0.18%,bulk density of 2.75 g·cm^(-3),firing shrinkage of 12.76%,bending strength reaching 101.93 MPa,and fracture toughness of 2.51 MPa·m^(1/2).As the amount ofα-Al_(2)O_(3) additive increased,the ceramic thin plates exhibited a greater abundance of short rod-like mullite and corundum grains,which were tightly packed together,forming a framework for the ceramic thin plates.This microstructure enhanced pathways for crack propagation,dispersed internal stresses,and increased fracture surface energy,resulting in significant improvements in both strength and fracture toughness of the ceramic thin plates.展开更多
In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of co...In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of copper strips connected to a capacitor at either end,is typically employed as a vacuum chamber to mitigate eddy current effects and beam coupling impedance.Consequently,the ceramic chamber exhibits a thin-walled multilayered complex structure.Previous theoretical studies have suggested that the impedance of such a structure has a negligible impact on the beam.However,recent impedance measurements of the ceramic chamber in the China Spallation Neutron Source(CSNS)RCS revealed a resonance in the low-frequency range,which was confirmed by further theoretical analysis as a source of beam instability in the RCS.Currently,the magnitude of this impedance cannot be accurately assessed using theoretical calculations.In this study,we used the CST Microwave Studio to confirm the impedance of the ceramic chamber.Further simulations covering six different types of ceramic chambers were conducted to develop an impedance model in the RCS.Additionally,this study investigates the resonant characteristics of the ceramic chamber impedance,finding that the resonant frequency is closely related to the capacitance of the capacitors.This finding provides clear directions for further impedance optimization and is crucial for achieving a beam power of 500 kW for the CSNS Phase-Ⅱ project(CSNS-Ⅱ).However,careful attention must be paid to the voltage across the capacitors.展开更多
In this study,the design,analysis,manufacturing,and testing of a 3D-printed conformal microstrip array antenna for high-temperature environments is presented.3D printing technology is used to fabricate a curved cerami...In this study,the design,analysis,manufacturing,and testing of a 3D-printed conformal microstrip array antenna for high-temperature environments is presented.3D printing technology is used to fabricate a curved ceramic substrate,and laser sintering and microdroplet spraying processes are used to add the conductive metal on the curved substrate.The problems of gain loss,bandwidth reduction,and frequency shift caused by high temperatures are addressed by using a proper antenna design,with parasitic patches,slots,and metal resonant cavities.The antenna prototype is characterized by the curved substrates and the conductive metals for the power dividers,the patch,and the ground plane;its performance is examined up to a temperature of 600℃in a muffle furnace and compared with the results from the numerical analysis.The results show that the antenna can effectively function at 600℃and even higher temperatures.展开更多
Protonic ceramic fuel cells(PCFCs)have been recognized as promising power generation devices for future clean energy systems,owing to their relatively low activation energy for proton migration and high energy convers...Protonic ceramic fuel cells(PCFCs)have been recognized as promising power generation devices for future clean energy systems,owing to their relatively low activation energy for proton migration and high energy conversion efficiency.In certain application scenarios,the use of N_(2)O(a potent greenhouse gas),as an alternative oxidant to air,presents a feasible strategy.Herein,we report for the first time the operation of PCFCs employing N_(2)O as the oxidant.A hybrid Pr_(2)Ni_(0.6)Co_(0.4)O_(4-δ)(PNCO-214)catalyst is developed,comprising Ruddlesden-Popper(R-P)structured Pr_(4)Ni_(1.8)Co_(1.2)O_(10-δ)(PNCO-4310)and fluorite structured Pr_(6)O_(11)(PO-611),which synergistically exhibits exceptional catalytic activity toward both N_(2)O decomposition and the oxygen reduction reaction,achieving a conversion over 92% and an area specific resistance of 1.301Ω·cm^(2) at 600℃.Quasi-insitu temperature-dependent Fourier transform infrared(FTIR)and electrochemical impedance spectroscopy analyses reveal that abundant oxygen vacancies in PNCO-214 facilitate rapid adsorption and dissociation of N_(2)O into N_(2) and O_(2),while also promoting the surface exchange kinetics of proton/oxygen during oxygen reduction reaction(ORR).When applied in an anode-supported single cell with PNCO-214 cathode operating under N_(2)O,outstanding power density and low resistance are achieved,delivering 0.801 W·cm^(-2) and 0.245Ω·cm^(2) at 600℃.Satisfactory performance is also maintained even when the temperature is reduced to 500℃.Furthermore,the single cell demonstrates relatively good stability with negligible degradation over 130 h at 600℃ and 0.7 V.These findings underscore the potential of PNCO-214 as a highly effective cathode catalyst for enabling the use of N_(2)O as a viable oxidant in PCFCs for specific industrial applications.展开更多
Ceramic aerogels(CAs)have emerged as a significant research frontier across various applications due to their lightweight,high porosity,and easily tunable structural characteristics.However,the intrinsic weak interact...Ceramic aerogels(CAs)have emerged as a significant research frontier across various applications due to their lightweight,high porosity,and easily tunable structural characteristics.However,the intrinsic weak interactions among the constituent nanoparticles,coupled with the limited toughness of traditional CAs,make them susceptible to structural collapse or even catastrophic failure when exposed to complex mechanical external forces.Unlike 0D building units,1D ceramic nanofibers(CNFs)possess a high aspect ratio and exceptional flexibility simultaneously,which are desirable building blocks for elastic CAs.This review presents the recent progress in electrospun ceramic nanofibrous aerogels(ECNFAs)that are constructed using ECNFs as building blocks,focusing on the various preparation methods and corresponding structural characteristics,strategies for optimizing mechanical performance,and a wide range of applications.The methods for preparing ECNFs and ECNFAs with diverse structures were initially explored,followed by the implementation of optimization strategies for enhancing ECNFAs,emphasizing the improvement of reinforcing the ECNFs,establishing the bonding effects between ECNFs,and designing the aggregate structures of the aerogels.Moreover,the applications of ECNFAs across various fields are also discussed.Finally,it highlights the existing challenges and potential opportunities for ECNFAs to achieve superior properties and realize promising prospects.展开更多
Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,a...Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,and 8 wt.%)on the wettability and interfacial reaction between the alloy and shell were investigated by a sessile-drop experiment.The results show that increasing the Al_(2)O_(3) doping contents(0−8 wt.%)reduces the porosity(21.74%−10.08%)and roughness(3.22−1.34μm)of the shell surface.The increase in Cr_(2)O_(3) dopant content(2−8 wt.%)further exacerbates the interfacial reaction,leading to an increase in the thickness of the reaction layer(2.6−3.1μm)and a decrease in the wetting angle(93.9°−91.0°).The addition of Al_(2)O_(3) and TiO_(2) dopants leads to the formation of Al_(2)TiO_(5) composite oxides in the reaction products,which effectively inhibits the interfacial reaction.The increase in TiO_(2) dopant contents(0−8 wt.%)further promotes the formation of Al_(2)TiO_(5),which decreases the thickness of the interfacial reaction layer(3.9−1.2μm)and increases the wetting angle(95.0°−103.8°).The introduced dopants enhance the packing density of the shell surface,while simultaneously suppress the diffusion of active metal elements from the alloy matrix to the interface.展开更多
(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperatu...(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural 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 feldspar-based microwave dielectric ceramic with low relative permittivity(εr)and excellent mechanical properties has attracted much attention in the fifth-generation wireless communication technology.In this wor...The feldspar-based microwave dielectric ceramic with low relative permittivity(εr)and excellent mechanical properties has attracted much attention in the fifth-generation wireless communication technology.In this work,a series of microwave dielectric ceramic SrAl_(2-x)Ga_(x)Si_(2)O_(8)(0.1≤x≤2.0)was synthesized using the traditional solid-state method.X-ray diffraction pattern indicates that Ga^(3+)can be dissolved into Al^(3+),forming a solid solution.Meanwhile,substitution of Ga^(3+)for Al^(3+)can promote the space group transition from I2/c(0.1≤x≤1.4)to P21/a(1.6≤x≤2.0)with coefficient of thermal expansion(CTE)increasing from 2.9×10^(-6)℃^(-1) to 5.2×10^(-6)℃^(-1).During this substitution,the phase transition can significantly improve the structural symmetry to enhance the dielectric properties and mechanical properties.Rietveld refinement results indicate that Ga^(3+)averagely occupied four Al^(3+)compositions to form solid solution.All ceramics have a dense microstructure and high relative density above 95%.An ultralower of 5.8 was obtained at x=1.6 composition with high quality factor(Q´f)of 50700 GHz and negative temperature coefficients of resonant frequency(tf)of approximately−35×10^(-6)℃^(-1).The densification temperature can be reduced to 940℃by adding 4%(in mass)LiF,resulting in good chemical compatibility with Ag electrode.Meanwhile,negativetf can be tuned to near-zero(+3.7×10^(-6)℃^(-1))by adding CaTiO_(3) ceramic.展开更多
ZnAl_(2)O_(4) and ZnAl_(2)O_(4)-based ceramics have attracted much attention from researchers due to their good microwave dielectric,thermal and mechanical properties.In this work,the influence of 5%(in mass)CuO-TiO_(...ZnAl_(2)O_(4) and ZnAl_(2)O_(4)-based ceramics have attracted much attention from researchers due to their good microwave dielectric,thermal and mechanical properties.In this work,the influence of 5%(in mass)CuO-TiO_(2)-Nb_(2)O_(5)(CTN)ternary composite oxide additives with different composition ratios on sintering behavior and properties of ZnAl_(2)O_(4) microwave dielectric ceramics was investigated.When the molar fraction ranges of Cu,Ti and Nb elements in 5%CTN additives are 0.625-0.875,0-0.250 and 0.125-0.625,respectively,sintering temperature of ZnAl_(2)O_(4) ceramics can be reduced from above 1400℃to below 1000℃.The sintering additives CN(Cu:Nb=1:1,molar ratio)and CTN(Cu:Ti:Nb=4:1:3,molar ratio)can reduce sintering temperature of ZnAl_(2)O_(4) ceramics to 975 and 1000℃,respectively,while maintaining good dielectric properties(dielectric constantε_(r)=11.36,quality factor Q׃=8245 GHz andε_(r)=9.52,Q׃=22249 GHz)and flexural strengths(200 and 161 MPa),which are expected to be applied in preparation of low temperature co-fired ceramic(LTCC)materials with copper electrodes.Low-temperature sintering of the ZnAl_(2)O_(4)+CTN system is characterized as activated sintering.Nanometer-level amorphous interfacial films containing Cu,Ti,and Nb elements are observed at the grain boundaries,which may provide fast diffusion pathways for mass transportation during the sintering process.Valence changes of Ti and Cu ions,along with changes of oxygen vacancies,are confirmed,which provides a potential mechanism for reduced sintering temperature of ZnAl_(2)O_(4) ceramics.In addition,a series of reactions occurring at the grain boundaries can activate these boundaries and further promote the sintering densification process.These results suggest a promising way to design a novel LTCC material with excellent properties based on the low temperature sintering of ceramics with the sintering aid of CuO-TiO_(2)-Nb_(2)O_(5) composite oxide.展开更多
JD Ceramics has been specializing in the field of air interlacing jets,air texturizing jets,and water jets over 29 years.With several years of technical accumulation and continuous equipments upgrades,we have been con...JD Ceramics has been specializing in the field of air interlacing jets,air texturizing jets,and water jets over 29 years.With several years of technical accumulation and continuous equipments upgrades,we have been consistently delivering high-precision,highquality,cost-effective ceramic nozzle solutions to the market.展开更多
1 Fascinated by the beauty of white Chinese porcelain(瓷),Marc Leuthold has spent two months creating contemporary artworks using the local clay and firing methods of Quyang,a county in Hebei Province,with over a thou...1 Fascinated by the beauty of white Chinese porcelain(瓷),Marc Leuthold has spent two months creating contemporary artworks using the local clay and firing methods of Quyang,a county in Hebei Province,with over a thousand years of ceramic⁃making history.2 Leuthold,an elected lifetime member of the International Academy of Ceramics and a retired professor from the State University of New York,has been invited to around 20 Chinese cities to exhibit,lecture and exchange ideas.He also worked full⁃time at an art institute in Shanghai from 2018 to 2023.展开更多
This paper presents a new type of ultra-material microwave pressure sensor designed for extreme environments,and conducts a systematic study on its structural design,manufacturing process,working mechanism,and experim...This paper presents a new type of ultra-material microwave pressure sensor designed for extreme environments,and conducts a systematic study on its structural design,manufacturing process,working mechanism,and experimental performance.The sensor is based on the cross-slot ultra-material resonant structure.Platinum-based conductive patterns are precisely fabricated on a high-purity alumina ceramic substrate through screen printing,and a strong bond between metal and ceramic is achieved through high-temperature sintering.Thanks to the high-temperature stability of the ceramic material and the high precision of the process,this sensor maintains excellent structural integrity and performance consistency in harsh environments.The working mechanism of the sensor is based on the microstructural deformation induced by pressure.When external pressure is applied to the ceramic cavity,the deformation of the cavity will change the equivalent electromagnetic boundary conditions inside,thereby causing perturbations in the resonant modes of the metamaterial,resulting in a continuous measurable shift in the resonant frequency.Based on this mechanism,the change in pressure can be precisely mapped to the frequency change,enabling wireless and passive pressure measurement.By utilizing the intrinsic resonant radiation of the metamaterial to achieve coupled readings,the complexity of sensor integration is significantly reduced and its working reliability in high-pressure,high-temperature,and strong electromagnetic interference environments is improved.During the design stage,the influence laws of the geometric parameters of the metamaterial and other factors on the resonant performance and pressure sensitivity were analyzed through finite element coupling simulation.Experimental verification shows that the sensor exhibits excellent linear pressure response within the range of 0−500 kPa,and maintains good repeatability and frequency stability in the high-pressure zone.The maximum sensitivity reaches 135 kHz/kPa,and the frequency drift is minimal during multiple loading-unloading cycles,fully demonstrating that the structural strength and reliability of the design meet the engineering requirements.The sensor proposed in this study could achieve longterm stable operation in aerospace engine compartments,high-temperature metallurgical furnaces,deep mine pressure monitoring,petrochemical high-corrosion pipelines,and extreme environment equipment.This research not only demonstrated the potential of integrating metamaterials with advanced ceramic processes to construct wireless passive sensors,but also provided new design ideas and process routes for the engineering application of microwave sensing technology in harsh environments.展开更多
Porous ceramic filters are key components in high-temperature metal-melt filtration processes.Mullite ceramics are widely used owing to their good high-temperature resistance,excellent chemical stability,and solid was...Porous ceramic filters are key components in high-temperature metal-melt filtration processes.Mullite ceramics are widely used owing to their good high-temperature resistance,excellent chemical stability,and solid waste green synthesis characteristics.However,traditional manufacturing processes face challenges in pore structure control for mullite ceramics and obtaining desirable mechanical properties,which limits their application.Recently,ceramic 3D-printing technology has emerged as a research hotspot,and its effectiveness for manufacturing complex 3D porous ceramic structures and controlling their mechanical properties has been demonstrated.This paper provides a detailed overview of the precursor system and toughening mechanisms of mullite,3D-printing technology for mullite ceramics,3D porous structure design for filters,and the melt purification mechanisms of these filters.The objective of this study was to use 3D-printing technology to efficiently manufacture mullite ceramic filter elements with customized structures,controllable pore characteristics,and desirable mechanical properties.展开更多
Formation of multicomponent ceramics is one of the most promising strategies for enhancing the ablation resistance of ultra-high-temperature carbide ceramics(UHTCCs),while the effects of the elements are the foundatio...Formation of multicomponent ceramics is one of the most promising strategies for enhancing the ablation resistance of ultra-high-temperature carbide ceramics(UHTCCs),while the effects of the elements are the foundation.Here,we reported an elemental synergistic effect by investigating the ablation behavior of three components,including Zr_(1/2)Hf_(1/3)Ti_(1/6)C(ZHTi),Zr_(1/2)Hf_(1/3)Ta_(1/6)C(ZHTa),and Zr_(1/2)Hf_(1/3)Ti_(1/12)Ta_(1/12)C(ZHTT).Results indicate that the Ti-Ta synergistic effect enables ZHTT to exhibit a low recession rate(3.33μm/s)and linear expansion rate(2.00μm/s)of its oxide layer,attributable to enhanced self-healing capability and durable protection.During ablation,outward diffusion of Ti can heal the oxide layer,but results in severe consumption of UHTCCs.Although the low-volatility oxide formed by Ta can reduce the loss rate of the matrix,the negligible outward diffusion of Ta leads to the formation of a porous outer oxide layer.The co-addition of Ti and Ta simultaneously provides effective self-healing and low matrix recession,enabling enhanced ablation resistance of ZHTT.展开更多
The highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was successfully fabri-cated by the addition of 3 at.%ZrO_(2) and 10 at.%La_(2)O_(3) introduced as sintering additive...The highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was successfully fabri-cated by the addition of 3 at.%ZrO_(2) and 10 at.%La_(2)O_(3) introduced as sintering additives via vacuum sin-tering.A single-phase solid solution cubic structure of the ceramic was obtained with a relative density of 99.95%and an average grain size of 6.91±3.28μm.The grain boundary of the(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was clean with a thickness of only 1.3 nm.Further observations revealed uniform distribu-tion of all elements in the grains,and the presence of La and Zr segregation(1.5 nm thick)at few grain boundaries,but causing very little light scattering.The in-line transmittance of high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic reached 80%at 1100 nm,which was 98.7%of the theoretical value of Er_(2)O_(3) single crystal.Also,there were fluorescence emissions observed in the ultraviolet(311 nm),vis-ible(563,622 nm),and near-infrared(1032,1535 nm)regions.In addition,the intense red emission and weak green emission were detected,and the broad emission with a peak at 1.5μm was attributed to Stark splitting of Er3+ions,so the corresponding mechanism was discussed.Results obtained suggest that the highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic fabricated in this study could have broad application prospects in optical applications such as scintillators,up-conversion luminescent materials,and infrared lasers.展开更多
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
As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancin...As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.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
基金Funded by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2023YFB4204302)。
文摘Ceramic thin plates were prepared using kaolin,potassium sodium feldspar and quartz powder as the main raw materials and kaolin,α-Al_(2)O_(3),MoO_(3) and AlF_(3)·3H_(2)O as additives.The experiment examined the effects of different additives on mullite formation,as well as the microstructure and properties of the ceramic thin plates.Additionally,the study explored the toughening and strengthening mechanisms induced by the additives,providing a theoretical foundation for further optimizing the toughness of ceramic thin plates.The results showed that the D4 sample fired at 1220℃(with an addition of 20 wt% α-Al_(2)O_(3))exhibited the best performance,with a water absorption rate of 0.07%,apparent porosity of 0.18%,bulk density of 2.75 g·cm^(-3),firing shrinkage of 12.76%,bending strength reaching 101.93 MPa,and fracture toughness of 2.51 MPa·m^(1/2).As the amount ofα-Al_(2)O_(3) additive increased,the ceramic thin plates exhibited a greater abundance of short rod-like mullite and corundum grains,which were tightly packed together,forming a framework for the ceramic thin plates.This microstructure enhanced pathways for crack propagation,dispersed internal stresses,and increased fracture surface energy,resulting in significant improvements in both strength and fracture toughness of the ceramic thin plates.
基金supported by the Guangdong Basic and Applied Basic Research Foundation,China(No.2021B1515140007).
文摘In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of copper strips connected to a capacitor at either end,is typically employed as a vacuum chamber to mitigate eddy current effects and beam coupling impedance.Consequently,the ceramic chamber exhibits a thin-walled multilayered complex structure.Previous theoretical studies have suggested that the impedance of such a structure has a negligible impact on the beam.However,recent impedance measurements of the ceramic chamber in the China Spallation Neutron Source(CSNS)RCS revealed a resonance in the low-frequency range,which was confirmed by further theoretical analysis as a source of beam instability in the RCS.Currently,the magnitude of this impedance cannot be accurately assessed using theoretical calculations.In this study,we used the CST Microwave Studio to confirm the impedance of the ceramic chamber.Further simulations covering six different types of ceramic chambers were conducted to develop an impedance model in the RCS.Additionally,this study investigates the resonant characteristics of the ceramic chamber impedance,finding that the resonant frequency is closely related to the capacitance of the capacitors.This finding provides clear directions for further impedance optimization and is crucial for achieving a beam power of 500 kW for the CSNS Phase-Ⅱ project(CSNS-Ⅱ).However,careful attention must be paid to the voltage across the capacitors.
基金National Natural Science Foundation of china(No.U2241205)the Natural Science Basic Research Program of Shaanxi(Nos.2022JC-33,2023-GHZD-35,and 2024JC-ZDXM-25)+1 种基金the Fundamental Research Funds for the Central Universitiesthe National 111 Project to provide fund for conducting experiments。
文摘In this study,the design,analysis,manufacturing,and testing of a 3D-printed conformal microstrip array antenna for high-temperature environments is presented.3D printing technology is used to fabricate a curved ceramic substrate,and laser sintering and microdroplet spraying processes are used to add the conductive metal on the curved substrate.The problems of gain loss,bandwidth reduction,and frequency shift caused by high temperatures are addressed by using a proper antenna design,with parasitic patches,slots,and metal resonant cavities.The antenna prototype is characterized by the curved substrates and the conductive metals for the power dividers,the patch,and the ground plane;its performance is examined up to a temperature of 600℃in a muffle furnace and compared with the results from the numerical analysis.The results show that the antenna can effectively function at 600℃and even higher temperatures.
基金financially supported by the National Key R&D Program of China(No.2024YFF0506300)National Natural Science Foundation of China(No.52336009)+5 种基金Key Research and Development Program of Shaanxi(No.2024CY2-GJHX-66)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515010429)Natural Science Basic Research Plan in Shaanxi Province of China(No.2024JC-YBQN-0475)Xidian University Specially Funded Project for Interdisciplinary Exploration(No.TZJH2024063)the Fundamental Research Funds for the Central Universities(No.QTZX23061)the Innovation Center of Nuclear Power Technology(No.HDLCXZX-2022-ZH-013).
文摘Protonic ceramic fuel cells(PCFCs)have been recognized as promising power generation devices for future clean energy systems,owing to their relatively low activation energy for proton migration and high energy conversion efficiency.In certain application scenarios,the use of N_(2)O(a potent greenhouse gas),as an alternative oxidant to air,presents a feasible strategy.Herein,we report for the first time the operation of PCFCs employing N_(2)O as the oxidant.A hybrid Pr_(2)Ni_(0.6)Co_(0.4)O_(4-δ)(PNCO-214)catalyst is developed,comprising Ruddlesden-Popper(R-P)structured Pr_(4)Ni_(1.8)Co_(1.2)O_(10-δ)(PNCO-4310)and fluorite structured Pr_(6)O_(11)(PO-611),which synergistically exhibits exceptional catalytic activity toward both N_(2)O decomposition and the oxygen reduction reaction,achieving a conversion over 92% and an area specific resistance of 1.301Ω·cm^(2) at 600℃.Quasi-insitu temperature-dependent Fourier transform infrared(FTIR)and electrochemical impedance spectroscopy analyses reveal that abundant oxygen vacancies in PNCO-214 facilitate rapid adsorption and dissociation of N_(2)O into N_(2) and O_(2),while also promoting the surface exchange kinetics of proton/oxygen during oxygen reduction reaction(ORR).When applied in an anode-supported single cell with PNCO-214 cathode operating under N_(2)O,outstanding power density and low resistance are achieved,delivering 0.801 W·cm^(-2) and 0.245Ω·cm^(2) at 600℃.Satisfactory performance is also maintained even when the temperature is reduced to 500℃.Furthermore,the single cell demonstrates relatively good stability with negligible degradation over 130 h at 600℃ and 0.7 V.These findings underscore the potential of PNCO-214 as a highly effective cathode catalyst for enabling the use of N_(2)O as a viable oxidant in PCFCs for specific industrial applications.
基金supported by the National Natural Science Foundation of China(Nos.92371110 and 52373281)Weiqiao Science Foundation(H2872302 and H2872303)the Scientific Research Innovation Capability Support Project for Young Faculty.
文摘Ceramic aerogels(CAs)have emerged as a significant research frontier across various applications due to their lightweight,high porosity,and easily tunable structural characteristics.However,the intrinsic weak interactions among the constituent nanoparticles,coupled with the limited toughness of traditional CAs,make them susceptible to structural collapse or even catastrophic failure when exposed to complex mechanical external forces.Unlike 0D building units,1D ceramic nanofibers(CNFs)possess a high aspect ratio and exceptional flexibility simultaneously,which are desirable building blocks for elastic CAs.This review presents the recent progress in electrospun ceramic nanofibrous aerogels(ECNFAs)that are constructed using ECNFs as building blocks,focusing on the various preparation methods and corresponding structural characteristics,strategies for optimizing mechanical performance,and a wide range of applications.The methods for preparing ECNFs and ECNFAs with diverse structures were initially explored,followed by the implementation of optimization strategies for enhancing ECNFAs,emphasizing the improvement of reinforcing the ECNFs,establishing the bonding effects between ECNFs,and designing the aggregate structures of the aerogels.Moreover,the applications of ECNFAs across various fields are also discussed.Finally,it highlights the existing challenges and potential opportunities for ECNFAs to achieve superior properties and realize promising prospects.
基金supported by the National Natural Science Foundation of China (No. 52374292)China Baowu Low Carbon Metallurgy Innovation Foundation, China (No. BWLCF202309)the Natural Science Foundation of Changsha City, China (No. KQ2208271)。
文摘Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,and 8 wt.%)on the wettability and interfacial reaction between the alloy and shell were investigated by a sessile-drop experiment.The results show that increasing the Al_(2)O_(3) doping contents(0−8 wt.%)reduces the porosity(21.74%−10.08%)and roughness(3.22−1.34μm)of the shell surface.The increase in Cr_(2)O_(3) dopant content(2−8 wt.%)further exacerbates the interfacial reaction,leading to an increase in the thickness of the reaction layer(2.6−3.1μm)and a decrease in the wetting angle(93.9°−91.0°).The addition of Al_(2)O_(3) and TiO_(2) dopants leads to the formation of Al_(2)TiO_(5) composite oxides in the reaction products,which effectively inhibits the interfacial reaction.The increase in TiO_(2) dopant contents(0−8 wt.%)further promotes the formation of Al_(2)TiO_(5),which decreases the thickness of the interfacial reaction layer(3.9−1.2μm)and increases the wetting angle(95.0°−103.8°).The introduced dopants enhance the packing density of the shell surface,while simultaneously suppress the diffusion of active metal elements from the alloy matrix to the interface.
基金supported by the National Natural Science Foundation of China(Nos.92166105 and 52005053)High-Tech Industry Science and Technology Innovation Leading Program of Hunan Province(No.2020GK2085)the Science and Technology Innovation Program of Hunan Province(No.2021RC3096).
文摘(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural 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National Natural Science Foundation of China (52302140)Major Scientific and Technological Innovation Project of Wenzhou (ZG2023040, ZG2023042)Joint Funds of the National Natural Science Foundation of China Key Program (U21B2068)。
文摘The feldspar-based microwave dielectric ceramic with low relative permittivity(εr)and excellent mechanical properties has attracted much attention in the fifth-generation wireless communication technology.In this work,a series of microwave dielectric ceramic SrAl_(2-x)Ga_(x)Si_(2)O_(8)(0.1≤x≤2.0)was synthesized using the traditional solid-state method.X-ray diffraction pattern indicates that Ga^(3+)can be dissolved into Al^(3+),forming a solid solution.Meanwhile,substitution of Ga^(3+)for Al^(3+)can promote the space group transition from I2/c(0.1≤x≤1.4)to P21/a(1.6≤x≤2.0)with coefficient of thermal expansion(CTE)increasing from 2.9×10^(-6)℃^(-1) to 5.2×10^(-6)℃^(-1).During this substitution,the phase transition can significantly improve the structural symmetry to enhance the dielectric properties and mechanical properties.Rietveld refinement results indicate that Ga^(3+)averagely occupied four Al^(3+)compositions to form solid solution.All ceramics have a dense microstructure and high relative density above 95%.An ultralower of 5.8 was obtained at x=1.6 composition with high quality factor(Q´f)of 50700 GHz and negative temperature coefficients of resonant frequency(tf)of approximately−35×10^(-6)℃^(-1).The densification temperature can be reduced to 940℃by adding 4%(in mass)LiF,resulting in good chemical compatibility with Ag electrode.Meanwhile,negativetf can be tuned to near-zero(+3.7×10^(-6)℃^(-1))by adding CaTiO_(3) ceramic.
基金National Natural Science Foundation of China (U24A2052)Shanghai Eastern Talent Plan。
文摘ZnAl_(2)O_(4) and ZnAl_(2)O_(4)-based ceramics have attracted much attention from researchers due to their good microwave dielectric,thermal and mechanical properties.In this work,the influence of 5%(in mass)CuO-TiO_(2)-Nb_(2)O_(5)(CTN)ternary composite oxide additives with different composition ratios on sintering behavior and properties of ZnAl_(2)O_(4) microwave dielectric ceramics was investigated.When the molar fraction ranges of Cu,Ti and Nb elements in 5%CTN additives are 0.625-0.875,0-0.250 and 0.125-0.625,respectively,sintering temperature of ZnAl_(2)O_(4) ceramics can be reduced from above 1400℃to below 1000℃.The sintering additives CN(Cu:Nb=1:1,molar ratio)and CTN(Cu:Ti:Nb=4:1:3,molar ratio)can reduce sintering temperature of ZnAl_(2)O_(4) ceramics to 975 and 1000℃,respectively,while maintaining good dielectric properties(dielectric constantε_(r)=11.36,quality factor Q׃=8245 GHz andε_(r)=9.52,Q׃=22249 GHz)and flexural strengths(200 and 161 MPa),which are expected to be applied in preparation of low temperature co-fired ceramic(LTCC)materials with copper electrodes.Low-temperature sintering of the ZnAl_(2)O_(4)+CTN system is characterized as activated sintering.Nanometer-level amorphous interfacial films containing Cu,Ti,and Nb elements are observed at the grain boundaries,which may provide fast diffusion pathways for mass transportation during the sintering process.Valence changes of Ti and Cu ions,along with changes of oxygen vacancies,are confirmed,which provides a potential mechanism for reduced sintering temperature of ZnAl_(2)O_(4) ceramics.In addition,a series of reactions occurring at the grain boundaries can activate these boundaries and further promote the sintering densification process.These results suggest a promising way to design a novel LTCC material with excellent properties based on the low temperature sintering of ceramics with the sintering aid of CuO-TiO_(2)-Nb_(2)O_(5) composite oxide.
文摘JD Ceramics has been specializing in the field of air interlacing jets,air texturizing jets,and water jets over 29 years.With several years of technical accumulation and continuous equipments upgrades,we have been consistently delivering high-precision,highquality,cost-effective ceramic nozzle solutions to the market.
文摘1 Fascinated by the beauty of white Chinese porcelain(瓷),Marc Leuthold has spent two months creating contemporary artworks using the local clay and firing methods of Quyang,a county in Hebei Province,with over a thousand years of ceramic⁃making history.2 Leuthold,an elected lifetime member of the International Academy of Ceramics and a retired professor from the State University of New York,has been invited to around 20 Chinese cities to exhibit,lecture and exchange ideas.He also worked full⁃time at an art institute in Shanghai from 2018 to 2023.
基金supported by Key Research and Development Plan of Shanxi Province(Nos.202102030201005,202203021222022)National Natural Science Foundation of China(No.62401522)+2 种基金Fundamental Research of Shanxi Province(No.202203021222070)China Postdoctoral Science Foundation(No.2023M743313)Research Project Supported by Shanxi Scholarship Council of China.
文摘This paper presents a new type of ultra-material microwave pressure sensor designed for extreme environments,and conducts a systematic study on its structural design,manufacturing process,working mechanism,and experimental performance.The sensor is based on the cross-slot ultra-material resonant structure.Platinum-based conductive patterns are precisely fabricated on a high-purity alumina ceramic substrate through screen printing,and a strong bond between metal and ceramic is achieved through high-temperature sintering.Thanks to the high-temperature stability of the ceramic material and the high precision of the process,this sensor maintains excellent structural integrity and performance consistency in harsh environments.The working mechanism of the sensor is based on the microstructural deformation induced by pressure.When external pressure is applied to the ceramic cavity,the deformation of the cavity will change the equivalent electromagnetic boundary conditions inside,thereby causing perturbations in the resonant modes of the metamaterial,resulting in a continuous measurable shift in the resonant frequency.Based on this mechanism,the change in pressure can be precisely mapped to the frequency change,enabling wireless and passive pressure measurement.By utilizing the intrinsic resonant radiation of the metamaterial to achieve coupled readings,the complexity of sensor integration is significantly reduced and its working reliability in high-pressure,high-temperature,and strong electromagnetic interference environments is improved.During the design stage,the influence laws of the geometric parameters of the metamaterial and other factors on the resonant performance and pressure sensitivity were analyzed through finite element coupling simulation.Experimental verification shows that the sensor exhibits excellent linear pressure response within the range of 0−500 kPa,and maintains good repeatability and frequency stability in the high-pressure zone.The maximum sensitivity reaches 135 kHz/kPa,and the frequency drift is minimal during multiple loading-unloading cycles,fully demonstrating that the structural strength and reliability of the design meet the engineering requirements.The sensor proposed in this study could achieve longterm stable operation in aerospace engine compartments,high-temperature metallurgical furnaces,deep mine pressure monitoring,petrochemical high-corrosion pipelines,and extreme environment equipment.This research not only demonstrated the potential of integrating metamaterials with advanced ceramic processes to construct wireless passive sensors,but also provided new design ideas and process routes for the engineering application of microwave sensing technology in harsh environments.
基金supported by National Key Research and Development Program of China(Grant No.2022YFB4601400).
文摘Porous ceramic filters are key components in high-temperature metal-melt filtration processes.Mullite ceramics are widely used owing to their good high-temperature resistance,excellent chemical stability,and solid waste green synthesis characteristics.However,traditional manufacturing processes face challenges in pore structure control for mullite ceramics and obtaining desirable mechanical properties,which limits their application.Recently,ceramic 3D-printing technology has emerged as a research hotspot,and its effectiveness for manufacturing complex 3D porous ceramic structures and controlling their mechanical properties has been demonstrated.This paper provides a detailed overview of the precursor system and toughening mechanisms of mullite,3D-printing technology for mullite ceramics,3D porous structure design for filters,and the melt purification mechanisms of these filters.The objective of this study was to use 3D-printing technology to efficiently manufacture mullite ceramic filter elements with customized structures,controllable pore characteristics,and desirable mechanical properties.
基金supported by the National Natural Science Foundation of China grant numbers[52072410].
文摘Formation of multicomponent ceramics is one of the most promising strategies for enhancing the ablation resistance of ultra-high-temperature carbide ceramics(UHTCCs),while the effects of the elements are the foundation.Here,we reported an elemental synergistic effect by investigating the ablation behavior of three components,including Zr_(1/2)Hf_(1/3)Ti_(1/6)C(ZHTi),Zr_(1/2)Hf_(1/3)Ta_(1/6)C(ZHTa),and Zr_(1/2)Hf_(1/3)Ti_(1/12)Ta_(1/12)C(ZHTT).Results indicate that the Ti-Ta synergistic effect enables ZHTT to exhibit a low recession rate(3.33μm/s)and linear expansion rate(2.00μm/s)of its oxide layer,attributable to enhanced self-healing capability and durable protection.During ablation,outward diffusion of Ti can heal the oxide layer,but results in severe consumption of UHTCCs.Although the low-volatility oxide formed by Ta can reduce the loss rate of the matrix,the negligible outward diffusion of Ta leads to the formation of a porous outer oxide layer.The co-addition of Ti and Ta simultaneously provides effective self-healing and low matrix recession,enabling enhanced ablation resistance of ZHTT.
基金supported by the National Natural Science Foundation of China(No.51832002 and 52072077),Instrumental Analysis Center of Guangdong Unversity of Technology,Sinomate Institute of Materials Research(Guang Zhou)Co.,Ltd(SIMR)for assisting the TEM characterization.
文摘The highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was successfully fabri-cated by the addition of 3 at.%ZrO_(2) and 10 at.%La_(2)O_(3) introduced as sintering additives via vacuum sin-tering.A single-phase solid solution cubic structure of the ceramic was obtained with a relative density of 99.95%and an average grain size of 6.91±3.28μm.The grain boundary of the(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was clean with a thickness of only 1.3 nm.Further observations revealed uniform distribu-tion of all elements in the grains,and the presence of La and Zr segregation(1.5 nm thick)at few grain boundaries,but causing very little light scattering.The in-line transmittance of high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic reached 80%at 1100 nm,which was 98.7%of the theoretical value of Er_(2)O_(3) single crystal.Also,there were fluorescence emissions observed in the ultraviolet(311 nm),vis-ible(563,622 nm),and near-infrared(1032,1535 nm)regions.In addition,the intense red emission and weak green emission were detected,and the broad emission with a peak at 1.5μm was attributed to Stark splitting of Er3+ions,so the corresponding mechanism was discussed.Results obtained suggest that the highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic fabricated in this study could have broad application prospects in optical applications such as scintillators,up-conversion luminescent materials,and infrared lasers.
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supported by the National Natural Science Foundation of China(Nos.52130204,52174376,52202070,51822405)Guangdong Basic and Applied Basic Research Foundation(No.2021B1515120028)+6 种基金TQ Innovation Foundation(No.23-TQ09-02-ZT-01-005)Aeronautical Science Foundation of China(No.20220042053001)Science and Technology Innovation Team Plan of Shaanxi Province(No.2021TD-17)Key R&D Project of Shaanxi Province(No.2024GX-YBXM-220)Thousands Person Plan of Jiangxi Province(JXSQ2020102131)Fundamental Research Funds for the Central Universities(Nos.D5000230348,D5000220057)China Scholarship Council(Nos.202206290133,202306290190).
文摘As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.
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.
