Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several chall...Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.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
This study designs and synthesizes highly dense Li2 Mg_(6)ZnTi_(6)O_(20)microwave dielectric ceramics based on a high-entropy strategy,focusing on achieving stable structures,low sintering temperatures,and excellent c...This study designs and synthesizes highly dense Li2 Mg_(6)ZnTi_(6)O_(20)microwave dielectric ceramics based on a high-entropy strategy,focusing on achieving stable structures,low sintering temperatures,and excellent comprehensive performance.The ceramics exhibit a predominant face-centered cubic disordered phase(Fd-3 m)sintered at 1200-1280℃,alongside an increased presence of the second phase MgTiO_(3) at higher temperatures.Remarkably,these ceramics demonstrate excellent microwave dielectric properties(ε_(r)=16.69,Q×f=88,230 GHz,and τ_(f)=−36.5 ppm/℃).Additionally,we have explored the addition of x wt%LiF(1≤x≤5)to the Li2 Mg_(6)ZnTi_(6)O_(20)ceramics to enhance their applicability.The ceramics feature a spinel structure for LiF contents up to 3 wt%,while higher LiF concentrations induce the formation of a secondary phase,LiTiO2,characterized by a rock salt structure.Notably,the lattice distortion induced by LiF leads to a constant decrease in ε_(r).A moderate degree of lattice distortion serves to enhance the lattice stability of ceramics,which is reflected in increased lattice energy.Excellent microwave dielectric properties(ε_(r)=16.23,Q×f=89,728 GHz,τ_(f)=−43.5 ppm/℃)were obtained for x=3 ceramic sintered at 1140℃.Even at x=5,the ceramic retains excellent microwave dielectric properties(ε_(r)=16.02,Q×f=63,079 GHz,τ_(f)=−26 ppm/°C)at a low sintering temperature of 900°C.This work realizes the multiple effects of LiF and confirms good chemical compatibility with silver for LTCC(low-temperature co-fired ceramics)applications.展开更多
FeCoCrMnNiN_(x)high entropy nitride ceramics thin films were prepared using the magnetron sputtering method,and the effects of nitrogen content on the thin films’properties were later examined.The addition of N_(2)af...FeCoCrMnNiN_(x)high entropy nitride ceramics thin films were prepared using the magnetron sputtering method,and the effects of nitrogen content on the thin films’properties were later examined.The addition of N_(2)affected the microstructures of the thin films and their mechanical and corrosion properties.Compared with the FeCoCrMnNi thin films with 1-sccm N_(2),the addition of 2 and 3 sccm of N_(2)by as much as 5.45at%and 6.34at%changed the solid solution’s crystalline structure into an amorphous structure.The addition of nitro-gen caused drastic changes to the surface morphology,creating a smoother and more uniform surface without cauliflower units.The atomic force microscopy image analysis indicated that the addition of nitrogen reduced the surface roughness from 5.58 to 1.82 nm.Adding N_(2)to the CoCrFeMnNi thin film helped increase its mechanical properties,such as hardness and strength,while the Young’s modulus decreased.The hardness of(8.75±0.5)GPa and the reduced Young’s modulus of(257.37±11.4)GPa of the FeCoCrMnNi thin film reached(12.67±1.2)and(194.39±12.4)GPa,respectively,with 1 sccm N_(2).The applied coating of the CoCrFeMnNi thin film on 304SUS increased the corrosion resistance,whereas the addition of nitrogen to the CoCrFeMnNi thin film also improved its corrosion res-istance compared with that of the CoCrFeMnNi thin film without nitrogen.展开更多
This study described the structural, dielectric, and piezoelectric behavior of Pb1-xSrx[（Zr0.52Ti0.48）0.95（Mn1/3Nb2/3）0.05]O3 ceramics （PSZT-PMN, x=0, 0.025, 0.050, and 0.075）, prepared by a semi-wet route. X-ra...This study described the structural, dielectric, and piezoelectric behavior of Pb1-xSrx[（Zr0.52Ti0.48）0.95（Mn1/3Nb2/3）0.05]O3 ceramics （PSZT-PMN, x=0, 0.025, 0.050, and 0.075）, prepared by a semi-wet route. X-ray diffraction, dielectric, and piezoelectric investigations were carried out to analyze the crystal structure. The relative dielectric constant and dielectric loss were both calculated as the functions of temperature. The room-temperature dielectric constant reaches a maximum for a Sr2＋-modified PZT-PMN ceramic with an x value of 0.050, which corresponds to the morphotropic phase boundary （MPB）. Raman spectroscopy studies also confirm the existence of this MPB for x=0.050. The piezoelectric strain coefficients （d33） value shows a maximum response for this composition. In addition, the phase transition temperature decreases significantly when the Sr2＋concentration increases in the PZT-PMN ceramics.展开更多
The use of zirconia-based ceramic materials as smpport materidls for superconducting magnets and in cryopenic engineeriny generally has been considered. The relationship between compsition and mechanical properties at...The use of zirconia-based ceramic materials as smpport materidls for superconducting magnets and in cryopenic engineeriny generally has been considered. The relationship between compsition and mechanical properties at cryogenic temperature has also been investigated.展开更多
Structural and dielectric properties of polycrystalline samples of lead-free （l-x）（Nal/2Bil/2）TiO3-xZnO, prepared using a high-temperature solid-state reaction method, were investigated in the composition range o...Structural and dielectric properties of polycrystalline samples of lead-free （l-x）（Nal/2Bil/2）TiO3-xZnO, prepared using a high-temperature solid-state reaction method, were investigated in the composition range of 0≤x≤0.10. Rietveld analyses of X-ray diffraction data indicated the formation of a single-phase hexagonal structure with R3c symmetry. Williamson-Hall approach was applied to estimate the apparent particle size and lattice strain of the compounds. Temperature dependence of dielectric constant showed that the addition of ZnO to （Na1/2Bi1/2）TiO3 shifted the phase transition temperature towards higher side, a property favourable for practical applications of these ceramics. Further, temperature dependent permittivity data provided low temperature coefficient of capacitance （TCC〈8%） up to 100℃. Furthermore, a decrease in the value of dielectric loss with an increase in ZnO content was observed.展开更多
Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In t...Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye temperature.Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–C.However,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds form.When the pressure reaches 20 GPa,the covalent bonds change to metallic bonds.The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at most.Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics.At 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ductility.However,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure.In addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.展开更多
In this study, the relationship between the maximum impact force and velocity of partjcle has been derived on the basis of elastic theory and energy principle. Critical impact force and critical speed which cause init...In this study, the relationship between the maximum impact force and velocity of partjcle has been derived on the basis of elastic theory and energy principle. Critical impact force and critical speed which cause initial damage is anaIVsed and its analytical expression is presented. The impact force for six dlfferent materials was measu red at the same condition to investigate the v8riation of impact pararneter with material properties. The authors provide a simple test method and experimental de vice to imitate the impact of moving particle, A series of experiments on ceramics and gIass were car ried out to study the dependence of residual strength on the impulse.展开更多
Additive manufacturing(AM)has become a versatile and diverse technology that has a significant impact on manufacturing processes.Therefore,ceramic materials have been developed rapidly for use in AM processes.Vat phot...Additive manufacturing(AM)has become a versatile and diverse technology that has a significant impact on manufacturing processes.Therefore,ceramic materials have been developed rapidly for use in AM processes.Vat photopolymerization(VPP)is an AM method that enables the production of dense ceramic components with increased dimensional accuracy.In particular,it facilitates the fabrication of small and intricately shaped parts.This review summarizes the research advancements in ceramics prepared via VPP.Special attention is paid to the current status of relevant areas,such as slurry preparation and process optimization,as well as the form-ing mechanisms,debinding,sintering,performance characterization,and use of VPP-based ceramics.Moreover,earlier studies performed by our research group on numerous VPP-based ceramic aspects are considered.In ad-dition,a concise overview of the differences in forming principles,mechanical performance,advantages,and disadvantages between VPP-based ceramics and conventional colloidal-forming ceramics is presented.Finally,the challenges and prospects of VPP-based ceramics are discussed.展开更多
The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstru...The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstructure of ceramic are characterized by means of XRD, SEM, etc., and the physical and mechanical properties are also tested. The results show that besides the phase of corundum, a little mullite, Mg-Al spinel and hyalophane phases also exist in the product. These phases are produced via reaction in-situ, which can inhibit the overgrowth of Al2O3 grain in grain boundary, and improve the integral property of the material.展开更多
The up-conversion luminescent property of the oxyfluoride glass ceramics 30SiO2·15Al2O3· （50-x）PbF2·xCdF2 doped with 4ErF3·1YbF3 has been investigated. Up-conversion luminescent intensity of Er^3...The up-conversion luminescent property of the oxyfluoride glass ceramics 30SiO2·15Al2O3· （50-x）PbF2·xCdF2 doped with 4ErF3·1YbF3 has been investigated. Up-conversion luminescent intensity of Er^3＋ ions increased obviously after heat-treatment due to co-doping with CdF2. The structure model of nanocrystals PbxCdl-xF2 was determined and the effect of CdF2 in oxyfluoride glass ceramics was explained by the analysis of x-ray diffraction data. Different nucleation temperatures of samples with different compositions were obtained by differential thermal analysis curves and the results showed the growth process of different nanocrystals in glass ceramics.展开更多
Augite-based glass ceramics were synthesised using ZnO,FeO,and Fe_(2)O_(3)as additives,and the spinel formation,matrix structure,crystallisation thermodynamics,and physicochemical properties were investigated.The resu...Augite-based glass ceramics were synthesised using ZnO,FeO,and Fe_(2)O_(3)as additives,and the spinel formation,matrix structure,crystallisation thermodynamics,and physicochemical properties were investigated.The results showed that oxides resulted in numerous preliminary spinels in the glass matrix.FeO,ZnO,and Fe_(2)O_(3)influenced the formation of spinel,while FeO simplified the glass network.FeO and ZnO promoted bulk crystallisation of the parent glass.After adding oxides,the grains of augite phase were refined,and the relative quantities of augite crystal planes were also influenced.All samples displayed good mechanical properties and chemical stability.The 2wt%ZnO-doping sample displayed the maximum flexural strength(170.3 MPa).Chromium leaching amount values of all the samples were less than the national standard(1.5 mg/L),confirming the safety of the materials.In conclusion,an appropriate amount of zinc-containing raw material is beneficial for the preparation of augite-based glass ceramics.展开更多
Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and proper...Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of （K0.5Na0.5）NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the （K0.5Na0.5）1-xLixNbO3 ceramics.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
A new type of long periodic structure has been found in ZrO2-Y2O3 ceramics in annealed states. High resolution electron microscopy (HREM), selected area electron diffraction, and computer simulation have been used to ...A new type of long periodic structure has been found in ZrO2-Y2O3 ceramics in annealed states. High resolution electron microscopy (HREM), selected area electron diffraction, and computer simulation have been used to reveal the presence of the long periodic structure. The unit cell of the long periodic structure consists of a cubic ZrO2 unit cell and L10- like phase one.展开更多
A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 c...A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 ceramics prepared via this method reached 79.6%-86.9% while these ceramics maintained high compressive strengths of 2.2-5.5 MPa. More importantly, porous A1203 ceramic with a pore size gra- dient was also readily fabricated by casting serial layers of foams that were set for different time periods. The potential applications of porous Al2O3 and HA ceramics fabricated by this green foaming method in- cluding scaffolds for oil cleaning and cell culture, respectively, were also demonstrated.展开更多
（1 - x）PbZr0.54Tio.4603-xKNbO3 （0 〈 x 〈 25mo1%） （abbreviated as PZT-xKN） piezoelectric ceramics were successfully fabricated by a traditional sintering technique at 1225℃ for 30 min. The influence of KNbO3 co...（1 - x）PbZr0.54Tio.4603-xKNbO3 （0 〈 x 〈 25mo1%） （abbreviated as PZT-xKN） piezoelectric ceramics were successfully fabricated by a traditional sintering technique at 1225℃ for 30 min. The influence of KNbO3 content on the crystal structure and electrical properties of the PZT-xKN piezoelectric ceramics was studied. Samples with 0 〈 x 0.20 show a pure peroskite structure, indicating that ul KNbOdiffused ito the crystal lattice of PZT to form a single solid solution in this compositional range. A second Pb3Nb4013 phase is observed in the PZT-0.25KN sample, showing that the maximum solid solubility of KNbO3 in PZT matrix ceramic is less than 25mo1%. Compared with pure PZT piezoelectric ceramics, samples containing KNbO3 have smaller crystal grains. PZT-0.15KN exhibits excellent piezoelectric properties with d33 ： 209 pC/N.展开更多
In this paper,the effect of Ba^(2+)ions A-site doping LaFeO_(3)on structure,magnetic properties and microwave absorption properties was investigated by the sol-gel method.According to the TEM and FullProf refinement r...In this paper,the effect of Ba^(2+)ions A-site doping LaFeO_(3)on structure,magnetic properties and microwave absorption properties was investigated by the sol-gel method.According to the TEM and FullProf refinement results,the structure of LaFeO_(3)changes from orthogonal(SG:Pnma)to cubic(SG:Pm-3 m)when the Ba doping amount is x=0.4.The SEM image shows that the particles size tends to decrease with the increase of Ba content.The production of weak ferromagnetism indicates that Ba doping has a significant effect on the magnetic properties of LaFeO_(3).The Neel temperature(TN)decreases significantly with the increase of Ba doping amount.An appropriate amount of Ba doping can effectively increase the dielectric and magnetic loss of LaFeO_(3)ceramics powders.The increase permittivity(ε’andε″)may be attributed to the hopping of the electrons between the Fe^(3+)and Fe^(4+)ions with the Ba^(2+)ions doping.The minimum reflection loss(RL_(min))of La_(0.9)Ba_(0.1)FeO_(3)at 6.72 GHz reaches-30.04 dB,its effective bandwidth(RL≤-10 dB)is 2.1 GHz,and the matching thickness is only 3.2 mm.These results indicate that Ba doping can effectively control the microwave absorption properties of LaFeO_(3),especially in the Cband.展开更多
The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was ...The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was proposed, i.e. the 1/（nAnB） increases with increasing the ionic conductivity when x or y〈20% （in molar fraction）.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52171046)National Natural Science Foundation of China-key programme(No.52234010)the Fundamental Research Funds for the Central Universities and Shaanxi Provincial Key Science and Technology Innovation Team(No.2023-CX-TD-14).
文摘Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.
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supported by the National Natural Science Foundation of China(No.52102129)the Hunan Provincial Natural Science Foundation of China(No.2023JJ30138)the Science and Technology Innovation Program of Hunan Province(No.2023RC3094).
文摘This study designs and synthesizes highly dense Li2 Mg_(6)ZnTi_(6)O_(20)microwave dielectric ceramics based on a high-entropy strategy,focusing on achieving stable structures,low sintering temperatures,and excellent comprehensive performance.The ceramics exhibit a predominant face-centered cubic disordered phase(Fd-3 m)sintered at 1200-1280℃,alongside an increased presence of the second phase MgTiO_(3) at higher temperatures.Remarkably,these ceramics demonstrate excellent microwave dielectric properties(ε_(r)=16.69,Q×f=88,230 GHz,and τ_(f)=−36.5 ppm/℃).Additionally,we have explored the addition of x wt%LiF(1≤x≤5)to the Li2 Mg_(6)ZnTi_(6)O_(20)ceramics to enhance their applicability.The ceramics feature a spinel structure for LiF contents up to 3 wt%,while higher LiF concentrations induce the formation of a secondary phase,LiTiO2,characterized by a rock salt structure.Notably,the lattice distortion induced by LiF leads to a constant decrease in ε_(r).A moderate degree of lattice distortion serves to enhance the lattice stability of ceramics,which is reflected in increased lattice energy.Excellent microwave dielectric properties(ε_(r)=16.23,Q×f=89,728 GHz,τ_(f)=−43.5 ppm/℃)were obtained for x=3 ceramic sintered at 1140℃.Even at x=5,the ceramic retains excellent microwave dielectric properties(ε_(r)=16.02,Q×f=63,079 GHz,τ_(f)=−26 ppm/°C)at a low sintering temperature of 900°C.This work realizes the multiple effects of LiF and confirms good chemical compatibility with silver for LTCC(low-temperature co-fired ceramics)applications.
基金the Ahvaz Branch, Islamic Azad University for the financial support
文摘FeCoCrMnNiN_(x)high entropy nitride ceramics thin films were prepared using the magnetron sputtering method,and the effects of nitrogen content on the thin films’properties were later examined.The addition of N_(2)affected the microstructures of the thin films and their mechanical and corrosion properties.Compared with the FeCoCrMnNi thin films with 1-sccm N_(2),the addition of 2 and 3 sccm of N_(2)by as much as 5.45at%and 6.34at%changed the solid solution’s crystalline structure into an amorphous structure.The addition of nitro-gen caused drastic changes to the surface morphology,creating a smoother and more uniform surface without cauliflower units.The atomic force microscopy image analysis indicated that the addition of nitrogen reduced the surface roughness from 5.58 to 1.82 nm.Adding N_(2)to the CoCrFeMnNi thin film helped increase its mechanical properties,such as hardness and strength,while the Young’s modulus decreased.The hardness of(8.75±0.5)GPa and the reduced Young’s modulus of(257.37±11.4)GPa of the FeCoCrMnNi thin film reached(12.67±1.2)and(194.39±12.4)GPa,respectively,with 1 sccm N_(2).The applied coating of the CoCrFeMnNi thin film on 304SUS increased the corrosion resistance,whereas the addition of nitrogen to the CoCrFeMnNi thin film also improved its corrosion res-istance compared with that of the CoCrFeMnNi thin film without nitrogen.
基金the financial support by Defence Research and Development Organisation(DRDO),Government of India(No.ERIP/ER/0903830/M/01/1235)
文摘This study described the structural, dielectric, and piezoelectric behavior of Pb1-xSrx[（Zr0.52Ti0.48）0.95（Mn1/3Nb2/3）0.05]O3 ceramics （PSZT-PMN, x=0, 0.025, 0.050, and 0.075）, prepared by a semi-wet route. X-ray diffraction, dielectric, and piezoelectric investigations were carried out to analyze the crystal structure. The relative dielectric constant and dielectric loss were both calculated as the functions of temperature. The room-temperature dielectric constant reaches a maximum for a Sr2＋-modified PZT-PMN ceramic with an x value of 0.050, which corresponds to the morphotropic phase boundary （MPB）. Raman spectroscopy studies also confirm the existence of this MPB for x=0.050. The piezoelectric strain coefficients （d33） value shows a maximum response for this composition. In addition, the phase transition temperature decreases significantly when the Sr2＋concentration increases in the PZT-PMN ceramics.
文摘The use of zirconia-based ceramic materials as smpport materidls for superconducting magnets and in cryopenic engineeriny generally has been considered. The relationship between compsition and mechanical properties at cryogenic temperature has also been investigated.
基金The financial support,by the Department of Science and Technology,New Delhi (Grant No. SR/S2/CMP-17/2008)
文摘Structural and dielectric properties of polycrystalline samples of lead-free （l-x）（Nal/2Bil/2）TiO3-xZnO, prepared using a high-temperature solid-state reaction method, were investigated in the composition range of 0≤x≤0.10. Rietveld analyses of X-ray diffraction data indicated the formation of a single-phase hexagonal structure with R3c symmetry. Williamson-Hall approach was applied to estimate the apparent particle size and lattice strain of the compounds. Temperature dependence of dielectric constant showed that the addition of ZnO to （Na1/2Bi1/2）TiO3 shifted the phase transition temperature towards higher side, a property favourable for practical applications of these ceramics. Further, temperature dependent permittivity data provided low temperature coefficient of capacitance （TCC〈8%） up to 100℃. Furthermore, a decrease in the value of dielectric loss with an increase in ZnO content was observed.
基金Project supported by Fujian Science&Technology Innovation Laboratory for Energy Devices of China(21C-LAB)(Grant No.21C-OP-202013)the National Natural Science Foundation of China(Grant No.12064027)+1 种基金the International Science and Technology Cooperation Program of China(Grant No.2015DFA61800)the Scientific Research Fund of Jiangxi Provincial Education Department,China(Grant No.GJJ180973).
文摘Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye temperature.Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–C.However,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds form.When the pressure reaches 20 GPa,the covalent bonds change to metallic bonds.The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at most.Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics.At 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ductility.However,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure.In addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.
文摘In this study, the relationship between the maximum impact force and velocity of partjcle has been derived on the basis of elastic theory and energy principle. Critical impact force and critical speed which cause initial damage is anaIVsed and its analytical expression is presented. The impact force for six dlfferent materials was measu red at the same condition to investigate the v8riation of impact pararneter with material properties. The authors provide a simple test method and experimental de vice to imitate the impact of moving particle, A series of experiments on ceramics and gIass were car ried out to study the dependence of residual strength on the impulse.
基金supported by Key-Area Research and Devel-opment Program of Guangdong Province of China(Grant No.2020B090923002)Guangdong Basic and Applied Basic Research Foun-dation of China(Grant No.2019B1515130005)+1 种基金Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program of China(Grant No.2017BT01C169)Foshan Science and Technology Innovation Team Project of China(Grant No.FS0AA-KJ919-4402-0023).
文摘Additive manufacturing(AM)has become a versatile and diverse technology that has a significant impact on manufacturing processes.Therefore,ceramic materials have been developed rapidly for use in AM processes.Vat photopolymerization(VPP)is an AM method that enables the production of dense ceramic components with increased dimensional accuracy.In particular,it facilitates the fabrication of small and intricately shaped parts.This review summarizes the research advancements in ceramics prepared via VPP.Special attention is paid to the current status of relevant areas,such as slurry preparation and process optimization,as well as the form-ing mechanisms,debinding,sintering,performance characterization,and use of VPP-based ceramics.Moreover,earlier studies performed by our research group on numerous VPP-based ceramic aspects are considered.In ad-dition,a concise overview of the differences in forming principles,mechanical performance,advantages,and disadvantages between VPP-based ceramics and conventional colloidal-forming ceramics is presented.Finally,the challenges and prospects of VPP-based ceramics are discussed.
基金This project was sponsored by "863" Project (No. 2003AA322020)
文摘The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstructure of ceramic are characterized by means of XRD, SEM, etc., and the physical and mechanical properties are also tested. The results show that besides the phase of corundum, a little mullite, Mg-Al spinel and hyalophane phases also exist in the product. These phases are produced via reaction in-situ, which can inhibit the overgrowth of Al2O3 grain in grain boundary, and improve the integral property of the material.
文摘The up-conversion luminescent property of the oxyfluoride glass ceramics 30SiO2·15Al2O3· （50-x）PbF2·xCdF2 doped with 4ErF3·1YbF3 has been investigated. Up-conversion luminescent intensity of Er^3＋ ions increased obviously after heat-treatment due to co-doping with CdF2. The structure model of nanocrystals PbxCdl-xF2 was determined and the effect of CdF2 in oxyfluoride glass ceramics was explained by the analysis of x-ray diffraction data. Different nucleation temperatures of samples with different compositions were obtained by differential thermal analysis curves and the results showed the growth process of different nanocrystals in glass ceramics.
基金supported by the National Key R&D Program of China(No.2019YFC1905701)the National Natural Science Foundation of China(Nos.U1960201 and 52204336)the China Postdoctoral Science Foundation(No.2022M710359).
文摘Augite-based glass ceramics were synthesised using ZnO,FeO,and Fe_(2)O_(3)as additives,and the spinel formation,matrix structure,crystallisation thermodynamics,and physicochemical properties were investigated.The results showed that oxides resulted in numerous preliminary spinels in the glass matrix.FeO,ZnO,and Fe_(2)O_(3)influenced the formation of spinel,while FeO simplified the glass network.FeO and ZnO promoted bulk crystallisation of the parent glass.After adding oxides,the grains of augite phase were refined,and the relative quantities of augite crystal planes were also influenced.All samples displayed good mechanical properties and chemical stability.The 2wt%ZnO-doping sample displayed the maximum flexural strength(170.3 MPa).Chromium leaching amount values of all the samples were less than the national standard(1.5 mg/L),confirming the safety of the materials.In conclusion,an appropriate amount of zinc-containing raw material is beneficial for the preparation of augite-based glass ceramics.
文摘Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of （K0.5Na0.5）NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the （K0.5Na0.5）1-xLixNbO3 ceramics.
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A new type of long periodic structure has been found in ZrO2-Y2O3 ceramics in annealed states. High resolution electron microscopy (HREM), selected area electron diffraction, and computer simulation have been used to reveal the presence of the long periodic structure. The unit cell of the long periodic structure consists of a cubic ZrO2 unit cell and L10- like phase one.
基金Jiangsu Innovation and Entrepreneurship ProgramJiangsu Provincial Special Program of Medical Science (BL2012004)+3 种基金Jiangsu R&D Innovation Program (BY2014059-07)the Priority Academic Program Development of Jiangsu High Education Institutionsthe National Natural Science Foundation of China (No. 51472279)the Jiangsu Six Peak of Talents Program (2013-WSW-056) for financial supports
文摘A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 ceramics prepared via this method reached 79.6%-86.9% while these ceramics maintained high compressive strengths of 2.2-5.5 MPa. More importantly, porous A1203 ceramic with a pore size gra- dient was also readily fabricated by casting serial layers of foams that were set for different time periods. The potential applications of porous Al2O3 and HA ceramics fabricated by this green foaming method in- cluding scaffolds for oil cleaning and cell culture, respectively, were also demonstrated.
基金financially supported by the Program of University-Industry Cooperation supported by the Ministry of Education and Guangdong Province of China (No.2008B090500262)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No. 20090006110010)
文摘（1 - x）PbZr0.54Tio.4603-xKNbO3 （0 〈 x 〈 25mo1%） （abbreviated as PZT-xKN） piezoelectric ceramics were successfully fabricated by a traditional sintering technique at 1225℃ for 30 min. The influence of KNbO3 content on the crystal structure and electrical properties of the PZT-xKN piezoelectric ceramics was studied. Samples with 0 〈 x 0.20 show a pure peroskite structure, indicating that ul KNbOdiffused ito the crystal lattice of PZT to form a single solid solution in this compositional range. A second Pb3Nb4013 phase is observed in the PZT-0.25KN sample, showing that the maximum solid solubility of KNbO3 in PZT matrix ceramic is less than 25mo1%. Compared with pure PZT piezoelectric ceramics, samples containing KNbO3 have smaller crystal grains. PZT-0.15KN exhibits excellent piezoelectric properties with d33 ： 209 pC/N.
基金Project supported by the National Natural Science Foundation of China(51871066)Innovation Project of GUET Graduate Education(2020YCXS115)+1 种基金Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing(GXKL06170107)Talents Project of Guilin University of Electronic Technology and Guangxi Key Laboratory of Information Materials(201024-Z,191016-K,191010-Z)。
文摘In this paper,the effect of Ba^(2+)ions A-site doping LaFeO_(3)on structure,magnetic properties and microwave absorption properties was investigated by the sol-gel method.According to the TEM and FullProf refinement results,the structure of LaFeO_(3)changes from orthogonal(SG:Pnma)to cubic(SG:Pm-3 m)when the Ba doping amount is x=0.4.The SEM image shows that the particles size tends to decrease with the increase of Ba content.The production of weak ferromagnetism indicates that Ba doping has a significant effect on the magnetic properties of LaFeO_(3).The Neel temperature(TN)decreases significantly with the increase of Ba doping amount.An appropriate amount of Ba doping can effectively increase the dielectric and magnetic loss of LaFeO_(3)ceramics powders.The increase permittivity(ε’andε″)may be attributed to the hopping of the electrons between the Fe^(3+)and Fe^(4+)ions with the Ba^(2+)ions doping.The minimum reflection loss(RL_(min))of La_(0.9)Ba_(0.1)FeO_(3)at 6.72 GHz reaches-30.04 dB,its effective bandwidth(RL≤-10 dB)is 2.1 GHz,and the matching thickness is only 3.2 mm.These results indicate that Ba doping can effectively control the microwave absorption properties of LaFeO_(3),especially in the Cband.
文摘The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was proposed, i.e. the 1/（nAnB） increases with increasing the ionic conductivity when x or y〈20% （in molar fraction）.
