Cerium oxide is an earth-abundant,highly researched multifunctional oxide with great technological importance and wide applications area.Trivalent rare earth(RE^(3+))dopants modify the defects concentration,create ple...Cerium oxide is an earth-abundant,highly researched multifunctional oxide with great technological importance and wide applications area.Trivalent rare earth(RE^(3+))dopants modify the defects concentration,create plenty of Ce^(3+)■Ce^(4+)redox centres and generate numerous oxygen vacancies than the pure ceria.In the present work,CeO_(2)(CE),10 mol%Gd doped ceria(Ce_(0.9)Gd_(0.1)O_(2-δ);CGO),and 10 mol%Sm doped ceria(Ce_(0.9)Sm_(0.1)O_(2-δ);CSO)were synthesized by sol-gel auto-combustion method.The phase formation,particle morphology,and elemental distribution of the synthesized powder samples were studied by X-ray diffraction,Fourier transform infrared spectroscopy,field emission scanning electron microscopy,and energy dispersive X-ray analysis.UV-diffuse reflectance spectroscopy was used to study the optical properties of the material.The band gaps of the CE,CSO and CGO were calculated to be2.81,2.71 and 2.60 eV,respectively.Electrochemical impedance spectroscopy(EIS)at room temperature(RT)investigated the materials'electrical properties.The improved electrical conductivity was registered for the doped variants.CGO reaches the highest one(0.4×10^(-7)S/cm)at RT.Cyclic voltammetry(CV)was performed to study the oxidation-reduction behavior and reversibility of the ion intercalation-deintercalation process of the materials in an electrolyte solution.For the doped ceria,a threefold improved current density is observed for the cathodic part,while a small improvement is reflected in the anodic part.Specific capacitance(C_(sp))was calculated at the Faradaic and non-Faradaic region of the voltammograms.C_(sp)of the materials increases in the order of CE<<CSO<CGO.The highest Csp 345.16 F/g at a scan rate of 5 mV/s is obtained for the CGO.Lastly,a correlation is drawn by analysing cyclic voltammograms to conclude the applicability of the doped ceria material for roomtemperature water-electrolysis in the alkaline medium.展开更多
Cerium oxide(CeO_(2)),or ceria,and its doped derivatives have been extensively studied for several decades and are well-known oxides valued for their unique structural properties and wide range of applications.These m...Cerium oxide(CeO_(2)),or ceria,and its doped derivatives have been extensively studied for several decades and are well-known oxides valued for their unique structural properties and wide range of applications.These materials play a crucial role in sustainable development within society.Structural modification through de fect e ngineering of the highly stable cubic fluorite phase enhances the versatility of this doped ceria to a new level.Among the numerous dopants of the CeO_(2)matrix,ceria doped with gadolinium(Gd),known as Ce_(1-x)Gd_(x)O_(2-■)(CGO),is gaining popularity due to its multifunctionality.The introduction of defect-induced vacancies in the oxygen sublattice(V_(o))and a change in the average valence of cerium(Ce^(3+)/Ce^(4+))are primarily responsible for the improved performance compared to pristine CeO_(2).These materials are currently undergoing intensive research for potential use as electrolytes in intermediate-temperature solid oxide fuel cells(IT-SOFCs)and dense oxygen-permeable membranes(OPMs).Additionally,they are being commercially utilized for power generation and oxygen separation.CGO materials are also attracting significant attention in various fields such as optics,photocatalysis,electrostriction,spintronics,gas sensing,electrocatalysis,and biomedical applications.This review paper aims to compile the latest contributions to CGO materials and comprehensively cover their various application areas.The crystal structure,defect equilibrium in Gd^(3+)-doped CeO_(2),the origin of multifunctionality,and the prospects of these materials are also exclusively discussed.展开更多
Porous Si3N4-SiO2-based ceramics with different porosity were prepared via free sintering of Si3N4 on air with an addition of semolina (5, 10 and 20 wt%) as a pore-forming agent. The semolina content in the starting p...Porous Si3N4-SiO2-based ceramics with different porosity were prepared via free sintering of Si3N4 on air with an addition of semolina (5, 10 and 20 wt%) as a pore-forming agent. The semolina content in the starting powder controlled the volume fraction of pores in the sintered body. Small pores (5 μm) formed a continuous network in the whole volume of the ceramic material, while the large pores (~100 μm), formed from the added semolina were mostly isolated in the ceramic matrix. Mercury porosimetry and strength measurements have shown that specific surface area, volume density and compressive strength decreased with the amount of semolina in the samples. Mechanical properties similar to bone were obtained for the sample with 20 wt% semolina pore forming agent (compressive strength 350 MPa, density 2.17 g.cm-3). The prepared Si3N4-SiO2-based ceramics were evaluated for cytotoxic and genotoxic potential on human fibroblast VH10 and B-HNF-1 cells. Biological tests have shown that both these human fibroblast cell lines were sensitive to the samples with lower porosity and cell growth inhibition was observed in the range 14.9% - 21.3%. The cytotoxicity of the sample with the highest porosity (~40%) was not significant (10%). The microscopic observations have shown that VH10 and B-HNF-1 cells growing around the silicon nitride ceramic discs were homogeneously distributed on the cultivation surface. No significant morphologic changes were found in treated cells, their morphology was very similar to that of the control cells. None of the tested Si3N4-based ceramic samples induced necrotic/apoptotic death of human fibroblasts. Sample S-20 had similar properties to bones and was characterized by very good biocompatibility, slight cytotoxicity and none genotoxicity. Therefore, Si3N4-SiO2-based ceramics prepared by free sintering on air are potential biomaterials for medical applications.展开更多
Surface modification is found to be an effective way to control the initial degradation of Mg based biomedical alloys.The present study focuses on the modulation of in vitro and in vivo degradation behavior of Mg-Ce a...Surface modification is found to be an effective way to control the initial degradation of Mg based biomedical alloys.The present study focuses on the modulation of in vitro and in vivo degradation behavior of Mg-Ce alloy through a stearic acid-treated polypyrrole coating,which developed superhydrophobic surface(contact angle∼153°)that drastically enhanced the corrosion resistance(more than 85%efficacy).Cerium addition to Mg alloy results basal texture strengthening and grain refinement,resulting in improved mechanical properties.All the specimens exhibited excellent antibacterial performance against gram-negative E.Coli(DH5α)and gram positive S.aureus bacteria.The oligodynamic effect of polypyrrole coating leads to complete bacterial mitigation.Non-toxic nature of the specimens was studied by MC3T3-E1 cell proliferation and differentiation in indirect cell culture method.Improved corrosion resistance of the coated specimen leads to enhanced cell proliferation and osteogenic differentiation.Hard tissue histology and micro-CT analysis exhibited higher fraction of newly formed callus tissues and highest bone-implant integration across the coated specimen,when implanted in rabbit femur.Efficacy of the material in fracture healing was evaluated by implanting bone plate and screw in a clinically fractured goat tibia.At 3 months,complete fracture healed with no vital organ toxicity was observed for the coated specimen.The present results suggest that Ce addition and polypyrrole coating are effective ways to modulate the corrosion and biocompatibility behavior making it a potential candidate for fracture fixation applications.展开更多
The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventiona...The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventional powder metallurgy technique. The aluminium powder and the whisker were effectively blended by a semi-powder metallurgy method. The blended powder mixtures were cold compacted and sintered at 600 ℃. The sintered composites were characterized for microstructural features by optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analysis. Porosity in the composites with variation in ABOw contents was determined. The effect of variation in content of ABOw on mechanical properties, viz. hardness, bending strength and compressive strength of the composites was evaluated. The dry sliding wear behaviour was evaluated at varying sliding distance at constant loads. Maximum flexural strength of 172 MPa and compressive strength of 324 MPa with improved hardness around HV 40.2 are obtained in composite with 10 wt.% ABOw. Further increase in ABOw content deteriorates the properties. A substantial increase in wear resistance is also observed with 10 wt.% ABOw. The excellent combination of mechanical properties of Al-10 wt.%ABOw composites is attributed to good interfacial bonds, less porosity and uniformity in the microstructure.展开更多
The weldability of the ZhS6U nickel-based superalloy, which is prone to solidification cracking during electron-beam welding(EBW) repair processes, was investigated. The effects of two different pre-weld heat-treatmen...The weldability of the ZhS6U nickel-based superalloy, which is prone to solidification cracking during electron-beam welding(EBW) repair processes, was investigated. The effects of two different pre-weld heat-treatment cycles on the final microstructure before and after welding were examined. Welds were made on flat coupons using an EBW machine, and the two heat-treatment cycles were designed to reduce γ′ liquation before welding. Microstructural features were also examined by optical and scanning electron microscopy. The results showed that the change in the morphology and size of the γ′ precipitates in the pre-weld heat-treatment cycles changed the ability of the superalloy to release the tensile stresses caused by the matrix phase cooling after EBW. The high hardness in the welded coupons subjected to the first heat-treatment cycle resulted in greater resistance to stress release by the base alloy, and the concentration of stress in the base metal caused liquation cracks in the heat-affected zone and solidification cracks in the weld area.展开更多
In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the fille...In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.展开更多
1 Introduction Kyanite is an important naturally occurring in-dustrial mineral and is used in the manufacture of avariety of industrial ceramic products; notable exam-ples include refractories and porcelains. It is a ...1 Introduction Kyanite is an important naturally occurring in-dustrial mineral and is used in the manufacture of avariety of industrial ceramic products; notable exam-ples include refractories and porcelains. It is a high-pressure polymorph of the aluminosilicates of the ne-sosilicate group, which includes kyanite, sillimanite,and andalusite. These three aluminous or alumina-rich minerals are chemically identical with the compo-sition, Al;SiO;, but have different crystal structuresand physical properties. It is, however, their alumina展开更多
Influences of gap size and cyclic-thermal-shock treatment on the mechanical properties of transient liquid phase（TLP） bonded IN-738 LC superalloy were investigated. For this purpose, TLP bonding of IN-738 LC superal...Influences of gap size and cyclic-thermal-shock treatment on the mechanical properties of transient liquid phase（TLP） bonded IN-738 LC superalloy were investigated. For this purpose, TLP bonding of IN-738 LC superalloy was carried out in a vacuum furnace using powdered AMS 4777 as the filler metal. The results showed that isothermal solidified zone（ISZ） consisted of Ni solid-solution and the distribution of alloying elements was homogeneous. High hardness of HV 409 and high shear strength of 506 MPa were observed in 40 μm gap sample. Alloying elements formed γ′ precipitates and the solid-solution in the ISZ. Hardness and shear strength of bonds were reduced with increasing the gap size（in range of 40-120 μm）. The fractured surfaces of complete isothermal solidified bonds showed dimpled rupture, but athermal solidified bonds showed cleavage fracture surface. 10, 20, 30 and 40 thermal-shock cycles were applied to 80 μm gap samples, respectively. The shear strength of the bond was measured to be 268 MPa after the 40 th thermal-shock cycle. The sample with gap size of 80 μm was failed due to crack nucleation on faying surface at 45 th thermal-shock cycle. The amount of the produced brittleness due to quenching the samples in water bath was attributed to the number of thermal-shock cycles.展开更多
Sodium-ion batteries(SIBs)with advantages of abundant resource and low cost have emerged as promising candidates for the next-generation energy storage systems.However,safety issues existing in electrolytes,anodes,and...Sodium-ion batteries(SIBs)with advantages of abundant resource and low cost have emerged as promising candidates for the next-generation energy storage systems.However,safety issues existing in electrolytes,anodes,and cathodes bring about frequent accidents regarding battery fires and explosions and impede the development of high-performance SIBs.Therefore,safety analysis and high-safety battery design have become prerequisites for the development of advanced energy storage systems.The reported reviews that only focus on a specific issue are difficult to provide overall guidance for building high-safety SIBs.To overcome the limitation,this review summarizes the recent research progress from the perspective of key components of SIBs for the first time and evaluates the characteristics of various improvement strategies.By orderly analyzing the root causes of safety problems associated with different components in SIBs(including electrolytes,anodes,and cathodes),corresponding improvement strategies for each component were discussed systematically.In addition,some noteworthy points and perspectives including the chain reaction between security issues and the selection of improvement strategies tailored to different needs have also been proposed.In brief,this review is designed to deepen our understanding of the SIBs safety issues and provide guidance and assistance for designing high-safety SIBs.展开更多
(Ba, Sr)RuO3 has been paid an attention as a promising electrode for (Ba, Sr)TiO3 dielectric material due to its similarity in structure and chemical composition with BST. In this study, (Ba, Sr)RuO3 conductive oxide ...(Ba, Sr)RuO3 has been paid an attention as a promising electrode for (Ba, Sr)TiO3 dielectric material due to its similarity in structure and chemical composition with BST. In this study, (Ba, Sr)RuO3 conductive oxide film was deposited on a 4 inch p-type Si wafer by metal organic chemical vapor deposition (MOCVD) using single cocktail source for the practical device application. Ba(TMHD)2, Sr(TMHD)2, Ru(TMHD)3 precursors and solvent [1-EtylePiPerdine (C7H15 N) ] as starting materials were mixed together for single cocktail source. A liquid delivery system (LDS) and a vaporization cell were utilized for the delivery and vaporization of single cocktail source, respectively. The source feeding rate was controlled by a liquid mass flow controller (LMFC). Deposition parameters, such as the oxygen flow and the source flow rate,were sensitive to phase formation, resistivity and the composition ratio of (Ba, Sr)RuO3 films. Highly (110)-textured (Ba,Sr)RuO3 film was obtained vhen the Ar/O2 ratio was 200/140 sccm at a source flow rate of 0.05 sccm. The process window of stoichiometric composition of BSR film was observed with varying the source flow rate from 0.05 sccm to 0.1 sccm.展开更多
Ultra-thin hafnium-oxide gate dielectric films deposited by atomic layer deposition technique using HfCl4 and H2O precursor on a hydrogen-terminated Si substrate were investigated. X-ray photoelectron spectroscopy ind...Ultra-thin hafnium-oxide gate dielectric films deposited by atomic layer deposition technique using HfCl4 and H2O precursor on a hydrogen-terminated Si substrate were investigated. X-ray photoelectron spectroscopy indicates that the interface layer is Hf-silicate rather than phase separated Hf-silicide and silicon oxide structure. The Hf-silicate interfacial layer partially changes into SiOx after high temperature annealing, resulting in a complex HfO2-silicate-SiOx dielectric structure. Electrical measurements confirms that HfO2 on Si is stable up to 700 ℃ for 30 s under N2 ambient.展开更多
Immersion of scaffolds in Simulated Body Fluid(10SBF)is a standardized method for evaluating their bioactivity,simulating in vivo conditions where apatite deposits can be formed on the surface of scaffold,facilitating...Immersion of scaffolds in Simulated Body Fluid(10SBF)is a standardized method for evaluating their bioactivity,simulating in vivo conditions where apatite deposits can be formed on the surface of scaffold,facilitating bone integration and ensuring their suitability for bone implant purposes,ultimately contributing to long-term implant success.The effect of apatite deposition on bioactivity and cell behavior of TiO_(2)scaffolds was studied.Scaffolds were soaked in 10SBF for different durations to form HAP layer on their surface.The results proved the development of a hydroxyapatite film resembling the mineral composition of bone Extracellular Matrix(ECM)on the TiO_(2)scaffolds.The XRD test findings showed the presence of hydroxyapatite layer similar to bone at the depth of 10 nm.A decrease in the specific surface area(18.913 m^(2)g^(−1)),the total pore volume(0.045172 cm^(3)g^(−1)(at p/p0=0.990)),and the mean pore diameter(9.5537 nm),were observed by BET analysis which confirmed the formation of the apatite layer.It was found that titania scaffolds with HAP coating promoted human osteosarcoma bone cell(MG63)cell attachment and growth.It seems that immersing the scaffolds in 10SBF to form HAP coating before utilizing them for bone tissue engineering applications might be a good strategy to promote bioactivity,cell attachment,and implant fixation.展开更多
Er-doped Y_(2)O_(3),Bi_(2)O_(3)and Sb_(2)O_(3)nanoparticles are synthesized using pulsed laser ablation in a liquid.Ceramic targets of Y_(2)O_(3):Er^(3+),Bi_(2)O_(3):Er^(3+)and Sb_(2)O_(3):Er^(3+)for ablation process ...Er-doped Y_(2)O_(3),Bi_(2)O_(3)and Sb_(2)O_(3)nanoparticles are synthesized using pulsed laser ablation in a liquid.Ceramic targets of Y_(2)O_(3):Er^(3+),Bi_(2)O_(3):Er^(3+)and Sb_(2)O_(3):Er^(3+)for ablation process are prepared by standard solid-state reaction technique and ablation is carried out in 5-ml distilled water using nanosecond Q-switched Nd:YAG laser.The morphology and size of the fabricated nanoparticles are evaluated by transmission electron microscopy and the luminescence emission properties of the prepared samples are investigated under different excitation wavelengths.展开更多
Semiconductor-based photocatalysts have been extensively studied for oxidative photodestruction of organic pollutants in wastewaters, releasing non-toxic substances such as Azo dyes. Various synthesized catalyst speci...Semiconductor-based photocatalysts have been extensively studied for oxidative photodestruction of organic pollutants in wastewaters, releasing non-toxic substances such as Azo dyes. Various synthesized catalyst specimens were characterized to determine the correlation between preparation conditions (catalyst type, dopant, microstructure, preparation routs, optical and physico-chemical properties) on the photocatalytic activity. Some researchers focused on the process parameters to optimize them to reach higher photoactivity. The specific surface areas, crystalline size, charge and pretreatment of the surface have significant effects on the physical and photocatalytic properties of the semiconductors. The surface sites of catalyst (TiO2) were modified by doping ZnS nanoparticles in the form of Core-Shell structure and the photocatalytic activities were determined by using color degradation and hydrogen production tests. The dye adsorption isotherms of photocatalyst were determined using UV-Vis spectroscopy. The specific surface properties were determined from BET, Zeta meter and Particle size analyzer tests. Photocatalytic decolorization of AR and water splitting test were applied to understand the relation between the surface properties and the photocatalytic activity. The result indicated that core-shell prepared samples had different surface suitable sites to cooperate in photocatalytic reaction.展开更多
The study experimented with using local ceramic raw materials (white clay, kaolin and silica or quartz) found in AssinFosu in the Central Region of Ghana to manufacture crucibles for melting metals and other precious ...The study experimented with using local ceramic raw materials (white clay, kaolin and silica or quartz) found in AssinFosu in the Central Region of Ghana to manufacture crucibles for melting metals and other precious minerals. Various physical tests were conducted on the materials to arrive at the body compositions. The compositions were also investigated for their elemental components by using X-ray fluorescence (XRF). The results revealed that the composition of Cruc containing 70% of white clay, 20% of kaolin, 8% of quartz and 2% of white grog;sintered at 1500˚C was very successful and therefore used to develop the recipe to manufacture the proposed crucibles. The “throwing” technique was employed to fabricate the crucibles. Test for thermal expansion was conducted for the manufactured crucibles at 1000˚C for thermal shock and microcracking tests. It was found out among others, that the recipe developed had very good physical and chemical properties of alumina silicate refractory materials and was fit for use at any high-temperature application. The study also recommended among others, that the researchers and institutions responsible for clay research such as Ghana Geological Survey Authority (GGSA) and Centre for Scientific and Industrial Research (CSIR) collaborate to improve upon this innovative idea.展开更多
Clay is a precious natural resource that is used in practically every aspect of life. It has a wide range of applications, including utilitarian and aesthetic items as well as electrical and electronic gadgets. Vume i...Clay is a precious natural resource that is used in practically every aspect of life. It has a wide range of applications, including utilitarian and aesthetic items as well as electrical and electronic gadgets. Vume is rich in clay types, which may be found in vast concentrations. In Vume, the commonest way of clay winning is the open pit method. Most clay winners usually abandoned the sites after their clay winning activities without any effort to reclaim it. As a result, the study was designed to investigate the causes of such clay over exploitation and its consequences in Vume. The study employed qualitative research method with phenomenological approach to investigate the problem. The convenience sampling as non-probabilty sampling method was adopted to select six (6) clay winners from two (2) sampling sites of clay winning, making a total sampling size of twelve (12) for this research. The justification was that these clay winners were available at the clay sites and also engaging in unsystematic clay winning activities during the visits by the researchers. The main instruments used for data collection were interviews and direct observation of sites. The study showed that if this rapid clay depletion was not addressed, it would have a negative impact on the pottery and ceramic centers in Vume. The study recommended among others that, there could be proper mechanism to organize clay winners into Small Scale Enterprises and become official distributors of clay to potters in Vume and other industries as well as institutions within the catchment area so that government could get tax revenue from the clay winning activities to develop Vume and the country at large.展开更多
文摘Cerium oxide is an earth-abundant,highly researched multifunctional oxide with great technological importance and wide applications area.Trivalent rare earth(RE^(3+))dopants modify the defects concentration,create plenty of Ce^(3+)■Ce^(4+)redox centres and generate numerous oxygen vacancies than the pure ceria.In the present work,CeO_(2)(CE),10 mol%Gd doped ceria(Ce_(0.9)Gd_(0.1)O_(2-δ);CGO),and 10 mol%Sm doped ceria(Ce_(0.9)Sm_(0.1)O_(2-δ);CSO)were synthesized by sol-gel auto-combustion method.The phase formation,particle morphology,and elemental distribution of the synthesized powder samples were studied by X-ray diffraction,Fourier transform infrared spectroscopy,field emission scanning electron microscopy,and energy dispersive X-ray analysis.UV-diffuse reflectance spectroscopy was used to study the optical properties of the material.The band gaps of the CE,CSO and CGO were calculated to be2.81,2.71 and 2.60 eV,respectively.Electrochemical impedance spectroscopy(EIS)at room temperature(RT)investigated the materials'electrical properties.The improved electrical conductivity was registered for the doped variants.CGO reaches the highest one(0.4×10^(-7)S/cm)at RT.Cyclic voltammetry(CV)was performed to study the oxidation-reduction behavior and reversibility of the ion intercalation-deintercalation process of the materials in an electrolyte solution.For the doped ceria,a threefold improved current density is observed for the cathodic part,while a small improvement is reflected in the anodic part.Specific capacitance(C_(sp))was calculated at the Faradaic and non-Faradaic region of the voltammograms.C_(sp)of the materials increases in the order of CE<<CSO<CGO.The highest Csp 345.16 F/g at a scan rate of 5 mV/s is obtained for the CGO.Lastly,a correlation is drawn by analysing cyclic voltammograms to conclude the applicability of the doped ceria material for roomtemperature water-electrolysis in the alkaline medium.
基金Project supported by the Indian Council of Medical Research(#5/3/8/30/ITR-f/2018-ITR)National Research Foundation of Korea(RS-2023-00278268)。
文摘Cerium oxide(CeO_(2)),or ceria,and its doped derivatives have been extensively studied for several decades and are well-known oxides valued for their unique structural properties and wide range of applications.These materials play a crucial role in sustainable development within society.Structural modification through de fect e ngineering of the highly stable cubic fluorite phase enhances the versatility of this doped ceria to a new level.Among the numerous dopants of the CeO_(2)matrix,ceria doped with gadolinium(Gd),known as Ce_(1-x)Gd_(x)O_(2-■)(CGO),is gaining popularity due to its multifunctionality.The introduction of defect-induced vacancies in the oxygen sublattice(V_(o))and a change in the average valence of cerium(Ce^(3+)/Ce^(4+))are primarily responsible for the improved performance compared to pristine CeO_(2).These materials are currently undergoing intensive research for potential use as electrolytes in intermediate-temperature solid oxide fuel cells(IT-SOFCs)and dense oxygen-permeable membranes(OPMs).Additionally,they are being commercially utilized for power generation and oxygen separation.CGO materials are also attracting significant attention in various fields such as optics,photocatalysis,electrostriction,spintronics,gas sensing,electrocatalysis,and biomedical applications.This review paper aims to compile the latest contributions to CGO materials and comprehensively cover their various application areas.The crystal structure,defect equilibrium in Gd^(3+)-doped CeO_(2),the origin of multifunctionality,and the prospects of these materials are also exclusively discussed.
基金This study was supported by the Technology Assistance Agency under the contract no.APVV-0500-10the Slovak State Committee for Scientific Research VEGA,grant 1/0165/10.
文摘Porous Si3N4-SiO2-based ceramics with different porosity were prepared via free sintering of Si3N4 on air with an addition of semolina (5, 10 and 20 wt%) as a pore-forming agent. The semolina content in the starting powder controlled the volume fraction of pores in the sintered body. Small pores (5 μm) formed a continuous network in the whole volume of the ceramic material, while the large pores (~100 μm), formed from the added semolina were mostly isolated in the ceramic matrix. Mercury porosimetry and strength measurements have shown that specific surface area, volume density and compressive strength decreased with the amount of semolina in the samples. Mechanical properties similar to bone were obtained for the sample with 20 wt% semolina pore forming agent (compressive strength 350 MPa, density 2.17 g.cm-3). The prepared Si3N4-SiO2-based ceramics were evaluated for cytotoxic and genotoxic potential on human fibroblast VH10 and B-HNF-1 cells. Biological tests have shown that both these human fibroblast cell lines were sensitive to the samples with lower porosity and cell growth inhibition was observed in the range 14.9% - 21.3%. The cytotoxicity of the sample with the highest porosity (~40%) was not significant (10%). The microscopic observations have shown that VH10 and B-HNF-1 cells growing around the silicon nitride ceramic discs were homogeneously distributed on the cultivation surface. No significant morphologic changes were found in treated cells, their morphology was very similar to that of the control cells. None of the tested Si3N4-based ceramic samples induced necrotic/apoptotic death of human fibroblasts. Sample S-20 had similar properties to bones and was characterized by very good biocompatibility, slight cytotoxicity and none genotoxicity. Therefore, Si3N4-SiO2-based ceramics prepared by free sintering on air are potential biomaterials for medical applications.
基金the financial assistance from Science and Engineering Research Board(SERBCRG/2020/002818/MMM).
文摘Surface modification is found to be an effective way to control the initial degradation of Mg based biomedical alloys.The present study focuses on the modulation of in vitro and in vivo degradation behavior of Mg-Ce alloy through a stearic acid-treated polypyrrole coating,which developed superhydrophobic surface(contact angle∼153°)that drastically enhanced the corrosion resistance(more than 85%efficacy).Cerium addition to Mg alloy results basal texture strengthening and grain refinement,resulting in improved mechanical properties.All the specimens exhibited excellent antibacterial performance against gram-negative E.Coli(DH5α)and gram positive S.aureus bacteria.The oligodynamic effect of polypyrrole coating leads to complete bacterial mitigation.Non-toxic nature of the specimens was studied by MC3T3-E1 cell proliferation and differentiation in indirect cell culture method.Improved corrosion resistance of the coated specimen leads to enhanced cell proliferation and osteogenic differentiation.Hard tissue histology and micro-CT analysis exhibited higher fraction of newly formed callus tissues and highest bone-implant integration across the coated specimen,when implanted in rabbit femur.Efficacy of the material in fracture healing was evaluated by implanting bone plate and screw in a clinically fractured goat tibia.At 3 months,complete fracture healed with no vital organ toxicity was observed for the coated specimen.The present results suggest that Ce addition and polypyrrole coating are effective ways to modulate the corrosion and biocompatibility behavior making it a potential candidate for fracture fixation applications.
基金support provided by the Central Instrument Facility Centre(CIFC)of IIT(BHU)the Department of Ceramic Engineering especially Advance Refractory Lab(ARL)of IIT(BHU)Varanasi。
文摘The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventional powder metallurgy technique. The aluminium powder and the whisker were effectively blended by a semi-powder metallurgy method. The blended powder mixtures were cold compacted and sintered at 600 ℃. The sintered composites were characterized for microstructural features by optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analysis. Porosity in the composites with variation in ABOw contents was determined. The effect of variation in content of ABOw on mechanical properties, viz. hardness, bending strength and compressive strength of the composites was evaluated. The dry sliding wear behaviour was evaluated at varying sliding distance at constant loads. Maximum flexural strength of 172 MPa and compressive strength of 324 MPa with improved hardness around HV 40.2 are obtained in composite with 10 wt.% ABOw. Further increase in ABOw content deteriorates the properties. A substantial increase in wear resistance is also observed with 10 wt.% ABOw. The excellent combination of mechanical properties of Al-10 wt.%ABOw composites is attributed to good interfacial bonds, less porosity and uniformity in the microstructure.
文摘The weldability of the ZhS6U nickel-based superalloy, which is prone to solidification cracking during electron-beam welding(EBW) repair processes, was investigated. The effects of two different pre-weld heat-treatment cycles on the final microstructure before and after welding were examined. Welds were made on flat coupons using an EBW machine, and the two heat-treatment cycles were designed to reduce γ′ liquation before welding. Microstructural features were also examined by optical and scanning electron microscopy. The results showed that the change in the morphology and size of the γ′ precipitates in the pre-weld heat-treatment cycles changed the ability of the superalloy to release the tensile stresses caused by the matrix phase cooling after EBW. The high hardness in the welded coupons subjected to the first heat-treatment cycle resulted in greater resistance to stress release by the base alloy, and the concentration of stress in the base metal caused liquation cracks in the heat-affected zone and solidification cracks in the weld area.
文摘In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.
文摘1 Introduction Kyanite is an important naturally occurring in-dustrial mineral and is used in the manufacture of avariety of industrial ceramic products; notable exam-ples include refractories and porcelains. It is a high-pressure polymorph of the aluminosilicates of the ne-sosilicate group, which includes kyanite, sillimanite,and andalusite. These three aluminous or alumina-rich minerals are chemically identical with the compo-sition, Al;SiO;, but have different crystal structuresand physical properties. It is, however, their alumina
文摘Influences of gap size and cyclic-thermal-shock treatment on the mechanical properties of transient liquid phase（TLP） bonded IN-738 LC superalloy were investigated. For this purpose, TLP bonding of IN-738 LC superalloy was carried out in a vacuum furnace using powdered AMS 4777 as the filler metal. The results showed that isothermal solidified zone（ISZ） consisted of Ni solid-solution and the distribution of alloying elements was homogeneous. High hardness of HV 409 and high shear strength of 506 MPa were observed in 40 μm gap sample. Alloying elements formed γ′ precipitates and the solid-solution in the ISZ. Hardness and shear strength of bonds were reduced with increasing the gap size（in range of 40-120 μm）. The fractured surfaces of complete isothermal solidified bonds showed dimpled rupture, but athermal solidified bonds showed cleavage fracture surface. 10, 20, 30 and 40 thermal-shock cycles were applied to 80 μm gap samples, respectively. The shear strength of the bond was measured to be 268 MPa after the 40 th thermal-shock cycle. The sample with gap size of 80 μm was failed due to crack nucleation on faying surface at 45 th thermal-shock cycle. The amount of the produced brittleness due to quenching the samples in water bath was attributed to the number of thermal-shock cycles.
基金supported by the Natural Science Foundation of China(52272188,U22A20227)the Natural Science Foundation of Beijing(2232025)+2 种基金the Natural Science Foundation of Chongqing(2022NSCQ-MSX2179)the Department of Science and Technology of Henan Province(Z20221343029)the Experimental Center of Advanced Materials in Beijing Institute of Technology。
文摘Sodium-ion batteries(SIBs)with advantages of abundant resource and low cost have emerged as promising candidates for the next-generation energy storage systems.However,safety issues existing in electrolytes,anodes,and cathodes bring about frequent accidents regarding battery fires and explosions and impede the development of high-performance SIBs.Therefore,safety analysis and high-safety battery design have become prerequisites for the development of advanced energy storage systems.The reported reviews that only focus on a specific issue are difficult to provide overall guidance for building high-safety SIBs.To overcome the limitation,this review summarizes the recent research progress from the perspective of key components of SIBs for the first time and evaluates the characteristics of various improvement strategies.By orderly analyzing the root causes of safety problems associated with different components in SIBs(including electrolytes,anodes,and cathodes),corresponding improvement strategies for each component were discussed systematically.In addition,some noteworthy points and perspectives including the chain reaction between security issues and the selection of improvement strategies tailored to different needs have also been proposed.In brief,this review is designed to deepen our understanding of the SIBs safety issues and provide guidance and assistance for designing high-safety SIBs.
文摘(Ba, Sr)RuO3 has been paid an attention as a promising electrode for (Ba, Sr)TiO3 dielectric material due to its similarity in structure and chemical composition with BST. In this study, (Ba, Sr)RuO3 conductive oxide film was deposited on a 4 inch p-type Si wafer by metal organic chemical vapor deposition (MOCVD) using single cocktail source for the practical device application. Ba(TMHD)2, Sr(TMHD)2, Ru(TMHD)3 precursors and solvent [1-EtylePiPerdine (C7H15 N) ] as starting materials were mixed together for single cocktail source. A liquid delivery system (LDS) and a vaporization cell were utilized for the delivery and vaporization of single cocktail source, respectively. The source feeding rate was controlled by a liquid mass flow controller (LMFC). Deposition parameters, such as the oxygen flow and the source flow rate,were sensitive to phase formation, resistivity and the composition ratio of (Ba, Sr)RuO3 films. Highly (110)-textured (Ba,Sr)RuO3 film was obtained vhen the Ar/O2 ratio was 200/140 sccm at a source flow rate of 0.05 sccm. The process window of stoichiometric composition of BSR film was observed with varying the source flow rate from 0.05 sccm to 0.1 sccm.
文摘Ultra-thin hafnium-oxide gate dielectric films deposited by atomic layer deposition technique using HfCl4 and H2O precursor on a hydrogen-terminated Si substrate were investigated. X-ray photoelectron spectroscopy indicates that the interface layer is Hf-silicate rather than phase separated Hf-silicide and silicon oxide structure. The Hf-silicate interfacial layer partially changes into SiOx after high temperature annealing, resulting in a complex HfO2-silicate-SiOx dielectric structure. Electrical measurements confirms that HfO2 on Si is stable up to 700 ℃ for 30 s under N2 ambient.
文摘Immersion of scaffolds in Simulated Body Fluid(10SBF)is a standardized method for evaluating their bioactivity,simulating in vivo conditions where apatite deposits can be formed on the surface of scaffold,facilitating bone integration and ensuring their suitability for bone implant purposes,ultimately contributing to long-term implant success.The effect of apatite deposition on bioactivity and cell behavior of TiO_(2)scaffolds was studied.Scaffolds were soaked in 10SBF for different durations to form HAP layer on their surface.The results proved the development of a hydroxyapatite film resembling the mineral composition of bone Extracellular Matrix(ECM)on the TiO_(2)scaffolds.The XRD test findings showed the presence of hydroxyapatite layer similar to bone at the depth of 10 nm.A decrease in the specific surface area(18.913 m^(2)g^(−1)),the total pore volume(0.045172 cm^(3)g^(−1)(at p/p0=0.990)),and the mean pore diameter(9.5537 nm),were observed by BET analysis which confirmed the formation of the apatite layer.It was found that titania scaffolds with HAP coating promoted human osteosarcoma bone cell(MG63)cell attachment and growth.It seems that immersing the scaffolds in 10SBF to form HAP coating before utilizing them for bone tissue engineering applications might be a good strategy to promote bioactivity,cell attachment,and implant fixation.
基金Supported by University Putra Malaysia and FCT(Fundação para a Ciência e a Tecnologia)for Post-Doctoral Research under Grant No SFRH/BPD/76185/2011the Research University Grant Scheme of Higher Education Malaysia(No 05-01-09-0754RU).
文摘Er-doped Y_(2)O_(3),Bi_(2)O_(3)and Sb_(2)O_(3)nanoparticles are synthesized using pulsed laser ablation in a liquid.Ceramic targets of Y_(2)O_(3):Er^(3+),Bi_(2)O_(3):Er^(3+)and Sb_(2)O_(3):Er^(3+)for ablation process are prepared by standard solid-state reaction technique and ablation is carried out in 5-ml distilled water using nanosecond Q-switched Nd:YAG laser.The morphology and size of the fabricated nanoparticles are evaluated by transmission electron microscopy and the luminescence emission properties of the prepared samples are investigated under different excitation wavelengths.
文摘Semiconductor-based photocatalysts have been extensively studied for oxidative photodestruction of organic pollutants in wastewaters, releasing non-toxic substances such as Azo dyes. Various synthesized catalyst specimens were characterized to determine the correlation between preparation conditions (catalyst type, dopant, microstructure, preparation routs, optical and physico-chemical properties) on the photocatalytic activity. Some researchers focused on the process parameters to optimize them to reach higher photoactivity. The specific surface areas, crystalline size, charge and pretreatment of the surface have significant effects on the physical and photocatalytic properties of the semiconductors. The surface sites of catalyst (TiO2) were modified by doping ZnS nanoparticles in the form of Core-Shell structure and the photocatalytic activities were determined by using color degradation and hydrogen production tests. The dye adsorption isotherms of photocatalyst were determined using UV-Vis spectroscopy. The specific surface properties were determined from BET, Zeta meter and Particle size analyzer tests. Photocatalytic decolorization of AR and water splitting test were applied to understand the relation between the surface properties and the photocatalytic activity. The result indicated that core-shell prepared samples had different surface suitable sites to cooperate in photocatalytic reaction.
文摘The study experimented with using local ceramic raw materials (white clay, kaolin and silica or quartz) found in AssinFosu in the Central Region of Ghana to manufacture crucibles for melting metals and other precious minerals. Various physical tests were conducted on the materials to arrive at the body compositions. The compositions were also investigated for their elemental components by using X-ray fluorescence (XRF). The results revealed that the composition of Cruc containing 70% of white clay, 20% of kaolin, 8% of quartz and 2% of white grog;sintered at 1500˚C was very successful and therefore used to develop the recipe to manufacture the proposed crucibles. The “throwing” technique was employed to fabricate the crucibles. Test for thermal expansion was conducted for the manufactured crucibles at 1000˚C for thermal shock and microcracking tests. It was found out among others, that the recipe developed had very good physical and chemical properties of alumina silicate refractory materials and was fit for use at any high-temperature application. The study also recommended among others, that the researchers and institutions responsible for clay research such as Ghana Geological Survey Authority (GGSA) and Centre for Scientific and Industrial Research (CSIR) collaborate to improve upon this innovative idea.
文摘Clay is a precious natural resource that is used in practically every aspect of life. It has a wide range of applications, including utilitarian and aesthetic items as well as electrical and electronic gadgets. Vume is rich in clay types, which may be found in vast concentrations. In Vume, the commonest way of clay winning is the open pit method. Most clay winners usually abandoned the sites after their clay winning activities without any effort to reclaim it. As a result, the study was designed to investigate the causes of such clay over exploitation and its consequences in Vume. The study employed qualitative research method with phenomenological approach to investigate the problem. The convenience sampling as non-probabilty sampling method was adopted to select six (6) clay winners from two (2) sampling sites of clay winning, making a total sampling size of twelve (12) for this research. The justification was that these clay winners were available at the clay sites and also engaging in unsystematic clay winning activities during the visits by the researchers. The main instruments used for data collection were interviews and direct observation of sites. The study showed that if this rapid clay depletion was not addressed, it would have a negative impact on the pottery and ceramic centers in Vume. The study recommended among others that, there could be proper mechanism to organize clay winners into Small Scale Enterprises and become official distributors of clay to potters in Vume and other industries as well as institutions within the catchment area so that government could get tax revenue from the clay winning activities to develop Vume and the country at large.
