High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based...High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based ceramics have been investigated.The Bi2O3 ,acting as a sintering additive,can effectively lower the sintering temperature of BaTiO3-based ceramics from 1300 to 1130 °C.The bulk density of BaTiO3-based ceramics increased and reached the maximum value with increasingBi2O3 content.The dielectric constant increased with increasingBi2O3 until it reached the maximum value with 0.8 mol%Bi2O3 additive,and the dielectric loss decreased with increasingBi2O3 content.Optimal dielectric properties of ε=2470,tanδ=0.011 and △ε/ε 25 ≤±9%（-55-150 °C） were obtained for the BaTiO3-based ceramics doped with 0.8 mol%Bi2O3 sintered at 1130 °C for 6 h.展开更多
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
Catalytic activity and hydrothermal stability are both crucial for the application of the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)catalyst in diesel vehicles.In this study,a tin(Sn)-modified Ce-N...Catalytic activity and hydrothermal stability are both crucial for the application of the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)catalyst in diesel vehicles.In this study,a tin(Sn)-modified Ce-Nb mixed-oxide catalyst was synthesized as an NH_(3)-SCR catalyst for NO_(x)emission control.After the intro-duction of Sn,both the NH_(3)-SCR activity and the hydrothermal stability of the catalyst were remarkably promoted.Even after hydrothermal aging at 1000℃,the developed Ce_(1)Sn_(2)Nb_(1)O_(x)catalyst achieved more than 90%NO_(x)conversion at 325-500℃.Various methods,including N2-physisorption,X-ray diffraction,in-situ high-temperature X-ray diffraction,high-resolution transmission electron microscopy,X-ray pho-toelectron spectroscopy,X-ray absorption fine-structure spectroscopy,temperature-programmed reduc-tion of hydrogen,temperature-programmed desorption of ammonia,and density functional theory calculations were used to investigate the promotional effects induced by the Sn species.The characteri-zation results showed that the addition of Sn not only promoted the formation of the Ce-Nb active phase but also improved its thermal stability,contributing to the excellent NH_(3)-SCR performance and hydrothermal stability.This study provides an excellent sintering-resistance catalyst for the application of diesel engine NO_(x)emission control.展开更多
The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Bas...The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.展开更多
To explore high value-added utilization pathways of fly ash,the mesoporous structure of silicon dioxide extracted from fly ash(FA-SiO_(2))was utilized to restrict the dicyandiamide(DCDA)thermal degradation process.Thi...To explore high value-added utilization pathways of fly ash,the mesoporous structure of silicon dioxide extracted from fly ash(FA-SiO_(2))was utilized to restrict the dicyandiamide(DCDA)thermal degradation process.This produced chemically bonded interacting composite photocatalysts of FA-SiO,and graphitic-phase carbon nitride(g-C_(3)N_(4)).Compared with the spherical silicon dioxide prepared using tetraethyl orthosilicate(TEOS-SiO_(2)),the mesoporous structure of FA-SiO_(2),allowed DCDA to react in a smaller space,which facilitated the transformation of DCDA to melamine by the thermal degradation kinetics of FA-C_(3)N_(4)/DCDA.This ultimately boosted the formation of an N-atom-removed triazine ring structure and a multistage structure combining lumps and rods in the composite photocatalysts of g-C_(3)N_(4),and FA-SiO_(2),which led to a higher visible-light utilization efficiency,a suitable valence-band position,and the photocatalytic activity for methylene blue reaching 3.56 times that of g-C_(3)N_(4).The findings indicate that mesoporous FA-SiO,has the potential to improve the structural and photocatalytic properties of g-C_(3)N_(4),-based materials.展开更多
The syntheses of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials have been reported and these materials have been developed as excellent MRI contrast agents.Due to the close interrelation between their morphology and pro...The syntheses of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials have been reported and these materials have been developed as excellent MRI contrast agents.Due to the close interrelation between their morphology and properties,it has resulted in the development of various particle sizes and shapes of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials.This has led to the extension of the uses of the materials to photocatalysis,drug delivery,and CT image contrast agents.Accordingly,these applications have been compiled and discussed in depth in this review.The potential of these materials in the above applications has started to attract significant attention.Moreover,the compilation of in-vitro toxicity studies from the literature was also discussed to facilitate the biocompatibility of the developed Gd(OH)_(3)nanomaterials.However,despite the rapid progress of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials,there are still knowledge gaps in certain areas.Therefore,this review provides insights into the recent development of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials to aid in accelerating novel developments.展开更多
Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning...Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning electron microscopy in combination with energy dispersive spectrometry. Mechanical properties, such as transverse rupture strength, hardness and fracture toughness, were measured. The results show that there are black core-grey rim structure and white core-grey rim structure in the microstructure. The grains become fine due to the VC/Cr3C2, and the grains of cermet added with 0.75VC/0.25Cr3C2 are refined most remarkably. The black core becomes finer with the increase of VC addition and rim phase becomes thicker with the decrease of Cr3C2 addition. The porosity increases with the increase of VC addition in VC/Cr3C2. Compared with the cermet free of VC/Cr3C2, the transverse rupture strength and hardness of cermets with VC/Cr3C2 are both improved, and the maximum values are both found for the cermet with 0.25VC/0.75Cr3C2. The fracture toughness can be effectively promoted by adding VC/Cr3C2 with an appropriate ratio of VC to Cr3C2, and the maximum value is found for the cermet with 0.5VC/0.5Cr3C2.展开更多
Ag3PO4 is found to be a highly efficient photocatalyst and receives great attention. The high activity of the photocatalyst is credited to the intrinsic electronic structure. The morphology control and nano-composite ...Ag3PO4 is found to be a highly efficient photocatalyst and receives great attention. The high activity of the photocatalyst is credited to the intrinsic electronic structure. The morphology control and nano-composite fabrication are used to improve the performance and practicability. This paper reviews the structure, properties and some theoretical aspects of Ag3PO4 single crystal. Also, the major strategies, namely the morphology control and hetero-nanostructure construction, as ways to improve the performance of Ag3PO4-based photocatalysts, are summarized with the aid of some typical instances.展开更多
Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-co...Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels.Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature.Due to the intensive theoretical investigations and experimental demonstrations,significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials.In this review,we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties.On this basis,we studied the effect of material parameters on thermoelectric properties.Then,we analyzed the features of Bi2Te3-based thermoelectric materials,including the lattice defects,anisotropic behavior and the strong bipolar conduction at relatively high temperature.Then we accordingly summarized the strategies for enhancing the thermoelectric performance,including point defect engineering,texture alignment,and band gap enlargement.Moreover,we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method,ball milling,and melt spinning.Lastly,we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3,which will enlighten the enhancement of thermoelectric performance in broader materials展开更多
Advanced high-strength steels (AHSSs) have been gradually applied to modern auto industry, as they have the advantages of improving the steel strength and lightening the car weight, which not only ensures the safety b...Advanced high-strength steels (AHSSs) have been gradually applied to modern auto industry, as they have the advantages of improving the steel strength and lightening the car weight, which not only ensures the safety but also saves the energy. However, the high-aluminum (Al) content in AHSSs may react with SiO2 in conventional CaO-SiO2-based mold flux during the process of continuous casting, which leads to the deterioration of the mold flux properties and a poor slab quality. Then, the non-reactive CaO-Al2O3-based mold flux was proposed and has been developing for the casting process of high-Al steels, but there are some problems of low consumption and insufficient lubrication that need to be solved. Thus, previous researches on the effect of each component on the properties of CaO-Al2O3-based mold flux were systematically summarized, and the situation of plant trials on CaO-Al2O3-based mold flux was evaluated. The results indicated that the proposed CaO-Al2O3-based mold fluxes could avoid the slag-metal reaction problems;however, the problems of lubri-cation, crystallization and heat transfer issues still exist. Therefore, tremendous works still need to be conducted for the development of new generation of CaO-Al2O3-based mold flux system. The review was performed aiming to provide a technical guidance for designing and optimizing CaO-Al2O3-based mold flux system that meets the demand of the continuous casting process of high-Al steels.展开更多
As a new organic conjugated semiconductor,graphitic carbon nitride(g-C_(3)N_(4))is emerging as a fascinating material for various photocatalytic applications due to its adjustable electronic structure,outstanding ther...As a new organic conjugated semiconductor,graphitic carbon nitride(g-C_(3)N_(4))is emerging as a fascinating material for various photocatalytic applications due to its adjustable electronic structure,outstanding thermal endurance,appealing chemical stability,low cost,and environmental friendliness.Nevertheless,unmodified bulk g-C_(3)N_(4) possesses some intrinsic limitations related to poor crystallinity,marginal visible-light harvesting,easy recombination of charge pairs,small surface area,and slow charge migration,which give rise to the low quantum efficiency of photocatalytic reactions.One efficient strategy to overcome these shortcomings is the manipulation of the microstructures of g-C_(3)N_(4).Other than the traditional structure control,mimicking the structures of creatures in nature to design and construct bio-inspired structures is a promising approach to improve the photocatalytic performance of g-C_(3)N_(4) and even g-C_(3)N_(4)-based systems.This review summarizes the recent advances of the traditional structure-control of g-C_(3)N_(4)-based systems,and bio-inspired synthesis of g-C_(3)N_(4)-based systems from two aspects of structural bionics and functional bionics.Furthermore,the fundamentals of bio-inspired design and fabrication of g-C_(3)N_(4)-based systems are introduced in detail.Additionally,the different theoretical calculations,diverse photocatalytic applications and various modification strategies of bio-inspired structured g-C_(3)N_(4)-based systems are recapped.We believe that this work will be a guiding star for future research in the new field of biomimetic photocatalysis.展开更多
Photocatalysis as an emerging "green" energy conversion technology has attracted domestic and international attention.This technology uses semiconductor photocatalysts to convert solar energy into directly u...Photocatalysis as an emerging "green" energy conversion technology has attracted domestic and international attention.This technology uses semiconductor photocatalysts to convert solar energy into directly usable chemical energy,showing great potential for application in environmental pollutant purification and clean energy production,with broad development prospects.Among many semiconductor materials,tungsten trioxide(WO_(3)) is favored by researchers in the field of photocatalysis because of its good visible light response and excellent valence band hole oxidation properties.Currently,a large number of photocatalysts based on WO_(3),in particular W03-based composite photocatalysts,have been reported,and their applications cover a wide range of fields.In order to promote the development of WO_(3)-based photocatalysts and provide a reference for colleagues,we present a systematic summary of the applications and research progress of W03-based composites in the field of photocatalysis in recent years.Starting from the structural properties of WO_(3)itself,this article summarizes the preparation methods and structure-activity relationships of WO_(3)-based composite photocatalysts.Subsequently,it introduces the current application status of existing WO_(3)-based composite photocatalysts in CO_(2) reduction,hydrogen production,nitrogen fixation,and pollutant removal.Finally,the development prospects were analyzed.展开更多
In recent decades,many additives with difierent characteristics have been applied to strengthen and toughen Al_2O_(3)一based ceramic cutting tool materials.Among them,SiC whiskers and SiC nanoparticles showed excellen...In recent decades,many additives with difierent characteristics have been applied to strengthen and toughen Al_2O_(3)一based ceramic cutting tool materials.Among them,SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties.W hile no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening efects of them have not been studied.An Al_2O_(3)一SiCw-SiCno advanced ceramic cutting tool material is fabricated by adding both one--dimensional SiC whiskers and zero--dimensional SiC nanoparticles into the Al_2O_(3)matrix with an efective dispersing and mixing process.The composites with 25 vo1%SiC whiskers and 25 vo1%SiC nanoparticles alone are also investegated for comparison purposes.Results show that the Al_2O_(3)一SiCw-SiCno composite with both 20 vo1%SiC whiskers and 5 vo1%SiC nanoparticles additives have much improved mechanical properties.The flexural strength of Al_2O_(3)-SiCw-SiCⅡD is 730~95 MPa and fracture toughness is 5.6±0.6 MPa’m.The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination.It is indicated that when SiC whiskers and nanoparticles are added together,the grains are further refined and homogenized,so that the microstructure and fracture mode ratio is modified.The SiC nanoparticles are found helpful to enhance the toughening efects of the SiC whiskers.The proposed research helps to enrich the types of ceramic cutting too1 and is benefit to expand the application range of ceramic cutting too1.展开更多
The effects of CaO/Al2O3 ratio on viscosity and structure of the CaO-Al2O3-based fluoride-free mould fluxes were investigated with the CaO/Al2O3 ratio varied from 1 to 4 and the content of SiO2 fixed at 7 wt.%. The in...The effects of CaO/Al2O3 ratio on viscosity and structure of the CaO-Al2O3-based fluoride-free mould fluxes were investigated with the CaO/Al2O3 ratio varied from 1 to 4 and the content of SiO2 fixed at 7 wt.%. The increase in the CaO/Al2O3 ratio from 1 to 2 lowered the viscosity of the flux melts. The viscosity increased slightly with the CaO/Al2O3 ratio from 2 to 3, and this increase became significant with further increasing CaO/Al2O3 ratio to 4. Both break temperature and apparent activation energy were found to be increased with the increase in CaO/Al2O3 ratio from 2 to 4. There was no break temperature available in the flux with CaO/Al2O3 ratio of 1. Changing the CaO/Al2O3 ratio from 1 to 2 decreased the apparent activation energy. Equilibrium phases of the fluxes were calculated using FactSage 7.1 and the major phases were found to be varied with the CaO/Al2O3 ratio. Structures of tested mould fluxes were analysed using Fourier transform infrared spectroscopy. The results showed that the increase in the CaO/Al2O3 ratio from 1 to 2 decreased the complexity of the structure, leading to a reduced viscosity. With the increase in the CaO/Al2O3 ratio from 2 to 4, both solid phase precipitation and melt structure contributed to the variation of viscosity.展开更多
A new technology was developed to recover multiple valuable elements from the spent Al2O3-based catalyst by X-ray phase analysis and exploratory experiments. The experimental results show that in the condition of roas...A new technology was developed to recover multiple valuable elements from the spent Al2O3-based catalyst by X-ray phase analysis and exploratory experiments. The experimental results show that in the condition of roasting temperature of 750℃ and roasting time of 30 min, molar ratio of Na2O to Al2O3 of 1.2, the leaching rates of alumina, vanadium and molybdenum in the spent catalyst are 97.2%, 95.8% and 98.9%, respectively. Vanadium and molybdenum in sodium aluminate solution can be recovered by precipitators A and B, and the precipitation rates of vanadium and molybdenum are 94.8% and 92.6%. Al（OH）3 was prepared from sodium aluminate solution in the carbonation decomposition process, and the purity of Al2O3 is 99.9% after calcination, the recovery of alumina reaches 90.6% in the whole process; the Ni-Co concentrate was leached by sulfuric acid, a nickel recovery of 98.2% and cobalt recovery over 98.5% can be obtained under the experimental condition of 30% H2SO4, 80℃, reaction time 4 h, mass ratio of liquid to solid 8, stirring rate 800r/min.展开更多
The interaction of MgO-MgAl_(2)O_(4)-based and MgO-Cr_(2)O_(3)-based refractories with X70 molten steel was studied by immersion experiments at 1560℃.The effects of immersion time(30 and 60 min)on the contents of tot...The interaction of MgO-MgAl_(2)O_(4)-based and MgO-Cr_(2)O_(3)-based refractories with X70 molten steel was studied by immersion experiments at 1560℃.The effects of immersion time(30 and 60 min)on the contents of total oxygen(TO),Al,Nb,Si,Mn,and Cr as well as the composition,number density,and size distribution of inclusions in the molten steel were investigated.The influence of the penetration and erosion degree of the molten steel to the refractory on the steel-refractory interface layer was analyzed.The results show that,at 1560℃,the MgO-MgAl_(2)O_(4)-based refractory can better control the contents of TO and the composition of molten steel compared with the MgO-Cr_(2)O_(3)-based refractory.The TO content is only 16×10^(-4) wt.%in the molten steel after reacted with the Mg0-MgAl_(2)O_(4)-based refractory at the end point of refining,4 accounting for 11.5%of that reacted with the MgO-Cr_(2)O_(3)-based refractory(139×10^(-4) wt.%).The number density of inclusions is only 14 mm^(-2),and the average size ofinclusions is only 1.31μm,with thelargest proportion of inclusions in 1-2μm(70%).The Al_(2)O_(3)-MnS-CaO complex inclusions in the original steel changed to complex inclusions dominated by Cr-Nb-Mn-S-O and MgO.Al_(2)O_(3),corresponding to the MgO-Cr_(2)O_(3)-based and MgO-MgAl_(2)O_(4)-based refractories,respectively.The MgO.Al_(2)O_(3) layer was formed at the reaction interface between MgO-MgAl_(2)O_(4)-based refractory and molten steel,which is helpful to restrict the erosion of refractories and the pollution of molten steel.The damage mechanism of the MgO-Cr_(2)O_(3)-based refractory is mainly permeation and chemical reaction,while the damage of the MgO-MgAl_(2)O_(4)-based refractory is mainlyscouring erosion.展开更多
The emergence of high performance 3D graphics cards has opened the way to PC clusters for high performance multi- display environment. In order to exploit the rendering ability of PC clusters, we should design appropr...The emergence of high performance 3D graphics cards has opened the way to PC clusters for high performance multi- display environment. In order to exploit the rendering ability of PC clusters, we should design appropriate parallel rendering algorithms and parallel graphics library interfaces. Due to the rapid development of Direct3D, we bring forward DPGL, the Direct3D9-based parallel graphics library in D3DPR parallel rendering system, which implements Direct3D9 interfaces to support existing Direct3D9 application parallelization with no modification. Based on the parallelism analysis of Direct3D9 rendering pipeline, we briefly introduce D3DPR parallel rendering system. DPGL is the fundamental component of D3DPR. After presenting DPGL three layers architecture, we discuss the rendering resource interception and management. Finally, we describe the design and implementation of DPGL in detail, including rendering command interception layer, rendering command interpretation layer and rendering resource parallelization layer.展开更多
The evolution of lead halide perovskites used for X-ray imaging scintillators has been facilitated by the development of solution-processable semiconductors characterized by large-area,flexible,fast photoresponse.The ...The evolution of lead halide perovskites used for X-ray imaging scintillators has been facilitated by the development of solution-processable semiconductors characterized by large-area,flexible,fast photoresponse.The stability and durability of these new perovskites are insufficient to achieve extended computed tomography scanning times with hard X-rays.In this study,we fabricated a self-assembled CsPbBr_(3)-based scintillator film with a flexible large-area uniform thickness using a new roomtemperature solution-processable method.The sensitivity and responsivity of X-ray photon conversion were quantitatively measured and showed a good linear response relationship suitable for X-ray imaging.We also demonstrated,for the first time,that the self-assembled CsPbBr_(3)-based scintillator has good stability for hard X-ray microtomography.Therefore,such an inexpensive solution-processed semiconductor easily prepared at room temperature can be used as a hard X-ray scintillator and equipped with flexible CsPbBr3-based X-ray detectors.It has great potential in three-dimensional high-resolution phase-contrast X-ray-imaging applications in biomedicine and material science because of its heavy Pb and Br atoms.展开更多
基金supported by the Tianjin Natural Science Foundation, China (Grant No. 06YFJMJC01000)
文摘High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based ceramics have been investigated.The Bi2O3 ,acting as a sintering additive,can effectively lower the sintering temperature of BaTiO3-based ceramics from 1300 to 1130 °C.The bulk density of BaTiO3-based ceramics increased and reached the maximum value with increasingBi2O3 content.The dielectric constant increased with increasingBi2O3 until it reached the maximum value with 0.8 mol%Bi2O3 additive,and the dielectric loss decreased with increasingBi2O3 content.Optimal dielectric properties of ε=2470,tanδ=0.011 and △ε/ε 25 ≤±9%（-55-150 °C） were obtained for the BaTiO3-based ceramics doped with 0.8 mol%Bi2O3 sintered at 1130 °C for 6 h.
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(52225004 and 22276202)the National Key Research and Development Program of China(2022YFC3701804)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2019045).
文摘Catalytic activity and hydrothermal stability are both crucial for the application of the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)catalyst in diesel vehicles.In this study,a tin(Sn)-modified Ce-Nb mixed-oxide catalyst was synthesized as an NH_(3)-SCR catalyst for NO_(x)emission control.After the intro-duction of Sn,both the NH_(3)-SCR activity and the hydrothermal stability of the catalyst were remarkably promoted.Even after hydrothermal aging at 1000℃,the developed Ce_(1)Sn_(2)Nb_(1)O_(x)catalyst achieved more than 90%NO_(x)conversion at 325-500℃.Various methods,including N2-physisorption,X-ray diffraction,in-situ high-temperature X-ray diffraction,high-resolution transmission electron microscopy,X-ray pho-toelectron spectroscopy,X-ray absorption fine-structure spectroscopy,temperature-programmed reduc-tion of hydrogen,temperature-programmed desorption of ammonia,and density functional theory calculations were used to investigate the promotional effects induced by the Sn species.The characteri-zation results showed that the addition of Sn not only promoted the formation of the Ce-Nb active phase but also improved its thermal stability,contributing to the excellent NH_(3)-SCR performance and hydrothermal stability.This study provides an excellent sintering-resistance catalyst for the application of diesel engine NO_(x)emission control.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174321,52274339 and 52074186).
文摘The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.
基金supported by the Medical Special Cultivation Project of Anhui University of Science and Technology(Nos.YZ2023H2B013 and YZ2023H2B012),China.
文摘To explore high value-added utilization pathways of fly ash,the mesoporous structure of silicon dioxide extracted from fly ash(FA-SiO_(2))was utilized to restrict the dicyandiamide(DCDA)thermal degradation process.This produced chemically bonded interacting composite photocatalysts of FA-SiO,and graphitic-phase carbon nitride(g-C_(3)N_(4)).Compared with the spherical silicon dioxide prepared using tetraethyl orthosilicate(TEOS-SiO_(2)),the mesoporous structure of FA-SiO_(2),allowed DCDA to react in a smaller space,which facilitated the transformation of DCDA to melamine by the thermal degradation kinetics of FA-C_(3)N_(4)/DCDA.This ultimately boosted the formation of an N-atom-removed triazine ring structure and a multistage structure combining lumps and rods in the composite photocatalysts of g-C_(3)N_(4),and FA-SiO_(2),which led to a higher visible-light utilization efficiency,a suitable valence-band position,and the photocatalytic activity for methylene blue reaching 3.56 times that of g-C_(3)N_(4).The findings indicate that mesoporous FA-SiO,has the potential to improve the structural and photocatalytic properties of g-C_(3)N_(4),-based materials.
基金the FRC grant(UBD/RSCH/1.4/FICBF(b)/2023/059)received from Universiti Brunei Darussalam,Brunei Darussalam。
文摘The syntheses of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials have been reported and these materials have been developed as excellent MRI contrast agents.Due to the close interrelation between their morphology and properties,it has resulted in the development of various particle sizes and shapes of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials.This has led to the extension of the uses of the materials to photocatalysis,drug delivery,and CT image contrast agents.Accordingly,these applications have been compiled and discussed in depth in this review.The potential of these materials in the above applications has started to attract significant attention.Moreover,the compilation of in-vitro toxicity studies from the literature was also discussed to facilitate the biocompatibility of the developed Gd(OH)_(3)nanomaterials.However,despite the rapid progress of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials,there are still knowledge gaps in certain areas.Therefore,this review provides insights into the recent development of Gd(OH)_(3)and Gd(OH)_(3)-based nanomaterials to aid in accelerating novel developments.
基金Project (090414185) supported by the Natural Science Foundation of Anhui Province, China
文摘Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning electron microscopy in combination with energy dispersive spectrometry. Mechanical properties, such as transverse rupture strength, hardness and fracture toughness, were measured. The results show that there are black core-grey rim structure and white core-grey rim structure in the microstructure. The grains become fine due to the VC/Cr3C2, and the grains of cermet added with 0.75VC/0.25Cr3C2 are refined most remarkably. The black core becomes finer with the increase of VC addition and rim phase becomes thicker with the decrease of Cr3C2 addition. The porosity increases with the increase of VC addition in VC/Cr3C2. Compared with the cermet free of VC/Cr3C2, the transverse rupture strength and hardness of cermets with VC/Cr3C2 are both improved, and the maximum values are both found for the cermet with 0.25VC/0.75Cr3C2. The fracture toughness can be effectively promoted by adding VC/Cr3C2 with an appropriate ratio of VC to Cr3C2, and the maximum value is found for the cermet with 0.5VC/0.5Cr3C2.
文摘Ag3PO4 is found to be a highly efficient photocatalyst and receives great attention. The high activity of the photocatalyst is credited to the intrinsic electronic structure. The morphology control and nano-composite fabrication are used to improve the performance and practicability. This paper reviews the structure, properties and some theoretical aspects of Ag3PO4 single crystal. Also, the major strategies, namely the morphology control and hetero-nanostructure construction, as ways to improve the performance of Ag3PO4-based photocatalysts, are summarized with the aid of some typical instances.
基金Project supported by the Australian Research CouncilZhi-Gang Chen thanks the USQ start-up grantstrategic research grant
文摘Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels.Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature.Due to the intensive theoretical investigations and experimental demonstrations,significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials.In this review,we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties.On this basis,we studied the effect of material parameters on thermoelectric properties.Then,we analyzed the features of Bi2Te3-based thermoelectric materials,including the lattice defects,anisotropic behavior and the strong bipolar conduction at relatively high temperature.Then we accordingly summarized the strategies for enhancing the thermoelectric performance,including point defect engineering,texture alignment,and band gap enlargement.Moreover,we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method,ball milling,and melt spinning.Lastly,we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3,which will enlighten the enhancement of thermoelectric performance in broader materials
基金National Natural Science Foundation of China(U1760202,51661130154)the Newton Advanced fellowship(NA 150320)is greatly acknowledged.
文摘Advanced high-strength steels (AHSSs) have been gradually applied to modern auto industry, as they have the advantages of improving the steel strength and lightening the car weight, which not only ensures the safety but also saves the energy. However, the high-aluminum (Al) content in AHSSs may react with SiO2 in conventional CaO-SiO2-based mold flux during the process of continuous casting, which leads to the deterioration of the mold flux properties and a poor slab quality. Then, the non-reactive CaO-Al2O3-based mold flux was proposed and has been developing for the casting process of high-Al steels, but there are some problems of low consumption and insufficient lubrication that need to be solved. Thus, previous researches on the effect of each component on the properties of CaO-Al2O3-based mold flux were systematically summarized, and the situation of plant trials on CaO-Al2O3-based mold flux was evaluated. The results indicated that the proposed CaO-Al2O3-based mold fluxes could avoid the slag-metal reaction problems;however, the problems of lubri-cation, crystallization and heat transfer issues still exist. Therefore, tremendous works still need to be conducted for the development of new generation of CaO-Al2O3-based mold flux system. The review was performed aiming to provide a technical guidance for designing and optimizing CaO-Al2O3-based mold flux system that meets the demand of the continuous casting process of high-Al steels.
文摘As a new organic conjugated semiconductor,graphitic carbon nitride(g-C_(3)N_(4))is emerging as a fascinating material for various photocatalytic applications due to its adjustable electronic structure,outstanding thermal endurance,appealing chemical stability,low cost,and environmental friendliness.Nevertheless,unmodified bulk g-C_(3)N_(4) possesses some intrinsic limitations related to poor crystallinity,marginal visible-light harvesting,easy recombination of charge pairs,small surface area,and slow charge migration,which give rise to the low quantum efficiency of photocatalytic reactions.One efficient strategy to overcome these shortcomings is the manipulation of the microstructures of g-C_(3)N_(4).Other than the traditional structure control,mimicking the structures of creatures in nature to design and construct bio-inspired structures is a promising approach to improve the photocatalytic performance of g-C_(3)N_(4) and even g-C_(3)N_(4)-based systems.This review summarizes the recent advances of the traditional structure-control of g-C_(3)N_(4)-based systems,and bio-inspired synthesis of g-C_(3)N_(4)-based systems from two aspects of structural bionics and functional bionics.Furthermore,the fundamentals of bio-inspired design and fabrication of g-C_(3)N_(4)-based systems are introduced in detail.Additionally,the different theoretical calculations,diverse photocatalytic applications and various modification strategies of bio-inspired structured g-C_(3)N_(4)-based systems are recapped.We believe that this work will be a guiding star for future research in the new field of biomimetic photocatalysis.
基金financially supported by the National Natural Science Foundation of China (No.22376051)the China Postdoctoral Science Foundation (Nos.2021T140512 and 2020M680869)the Natural Science Foundation of Hebei Province (No.B2021202001)。
文摘Photocatalysis as an emerging "green" energy conversion technology has attracted domestic and international attention.This technology uses semiconductor photocatalysts to convert solar energy into directly usable chemical energy,showing great potential for application in environmental pollutant purification and clean energy production,with broad development prospects.Among many semiconductor materials,tungsten trioxide(WO_(3)) is favored by researchers in the field of photocatalysis because of its good visible light response and excellent valence band hole oxidation properties.Currently,a large number of photocatalysts based on WO_(3),in particular W03-based composite photocatalysts,have been reported,and their applications cover a wide range of fields.In order to promote the development of WO_(3)-based photocatalysts and provide a reference for colleagues,we present a systematic summary of the applications and research progress of W03-based composites in the field of photocatalysis in recent years.Starting from the structural properties of WO_(3)itself,this article summarizes the preparation methods and structure-activity relationships of WO_(3)-based composite photocatalysts.Subsequently,it introduces the current application status of existing WO_(3)-based composite photocatalysts in CO_(2) reduction,hydrogen production,nitrogen fixation,and pollutant removal.Finally,the development prospects were analyzed.
基金Supported by National Natural Science Foundation of China(Grant No.51175305)
文摘In recent decades,many additives with difierent characteristics have been applied to strengthen and toughen Al_2O_(3)一based ceramic cutting tool materials.Among them,SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties.W hile no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening efects of them have not been studied.An Al_2O_(3)一SiCw-SiCno advanced ceramic cutting tool material is fabricated by adding both one--dimensional SiC whiskers and zero--dimensional SiC nanoparticles into the Al_2O_(3)matrix with an efective dispersing and mixing process.The composites with 25 vo1%SiC whiskers and 25 vo1%SiC nanoparticles alone are also investegated for comparison purposes.Results show that the Al_2O_(3)一SiCw-SiCno composite with both 20 vo1%SiC whiskers and 5 vo1%SiC nanoparticles additives have much improved mechanical properties.The flexural strength of Al_2O_(3)-SiCw-SiCⅡD is 730~95 MPa and fracture toughness is 5.6±0.6 MPa’m.The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination.It is indicated that when SiC whiskers and nanoparticles are added together,the grains are further refined and homogenized,so that the microstructure and fracture mode ratio is modified.The SiC nanoparticles are found helpful to enhance the toughening efects of the SiC whiskers.The proposed research helps to enrich the types of ceramic cutting too1 and is benefit to expand the application range of ceramic cutting too1.
文摘The effects of CaO/Al2O3 ratio on viscosity and structure of the CaO-Al2O3-based fluoride-free mould fluxes were investigated with the CaO/Al2O3 ratio varied from 1 to 4 and the content of SiO2 fixed at 7 wt.%. The increase in the CaO/Al2O3 ratio from 1 to 2 lowered the viscosity of the flux melts. The viscosity increased slightly with the CaO/Al2O3 ratio from 2 to 3, and this increase became significant with further increasing CaO/Al2O3 ratio to 4. Both break temperature and apparent activation energy were found to be increased with the increase in CaO/Al2O3 ratio from 2 to 4. There was no break temperature available in the flux with CaO/Al2O3 ratio of 1. Changing the CaO/Al2O3 ratio from 1 to 2 decreased the apparent activation energy. Equilibrium phases of the fluxes were calculated using FactSage 7.1 and the major phases were found to be varied with the CaO/Al2O3 ratio. Structures of tested mould fluxes were analysed using Fourier transform infrared spectroscopy. The results showed that the increase in the CaO/Al2O3 ratio from 1 to 2 decreased the complexity of the structure, leading to a reduced viscosity. With the increase in the CaO/Al2O3 ratio from 2 to 4, both solid phase precipitation and melt structure contributed to the variation of viscosity.
基金Project(2003 UDBEA00C020) supported by the Collaborative Project of School and Province of Yunnan Province
文摘A new technology was developed to recover multiple valuable elements from the spent Al2O3-based catalyst by X-ray phase analysis and exploratory experiments. The experimental results show that in the condition of roasting temperature of 750℃ and roasting time of 30 min, molar ratio of Na2O to Al2O3 of 1.2, the leaching rates of alumina, vanadium and molybdenum in the spent catalyst are 97.2%, 95.8% and 98.9%, respectively. Vanadium and molybdenum in sodium aluminate solution can be recovered by precipitators A and B, and the precipitation rates of vanadium and molybdenum are 94.8% and 92.6%. Al（OH）3 was prepared from sodium aluminate solution in the carbonation decomposition process, and the purity of Al2O3 is 99.9% after calcination, the recovery of alumina reaches 90.6% in the whole process; the Ni-Co concentrate was leached by sulfuric acid, a nickel recovery of 98.2% and cobalt recovery over 98.5% can be obtained under the experimental condition of 30% H2SO4, 80℃, reaction time 4 h, mass ratio of liquid to solid 8, stirring rate 800r/min.
基金support from the National Natural Science Foundation of China(Grant Nos.U1860205 and 52204352)Youth Project of Hubei Natural Science Foundation(Grant No.2022CFB593)+1 种基金Key R&D Project of Hubei Province(Grant No.2022BAA021)Guiding Project of Scientific Research Plan of Hubei Provincial Department of Education(Grant No.B2022019).
文摘The interaction of MgO-MgAl_(2)O_(4)-based and MgO-Cr_(2)O_(3)-based refractories with X70 molten steel was studied by immersion experiments at 1560℃.The effects of immersion time(30 and 60 min)on the contents of total oxygen(TO),Al,Nb,Si,Mn,and Cr as well as the composition,number density,and size distribution of inclusions in the molten steel were investigated.The influence of the penetration and erosion degree of the molten steel to the refractory on the steel-refractory interface layer was analyzed.The results show that,at 1560℃,the MgO-MgAl_(2)O_(4)-based refractory can better control the contents of TO and the composition of molten steel compared with the MgO-Cr_(2)O_(3)-based refractory.The TO content is only 16×10^(-4) wt.%in the molten steel after reacted with the Mg0-MgAl_(2)O_(4)-based refractory at the end point of refining,4 accounting for 11.5%of that reacted with the MgO-Cr_(2)O_(3)-based refractory(139×10^(-4) wt.%).The number density of inclusions is only 14 mm^(-2),and the average size ofinclusions is only 1.31μm,with thelargest proportion of inclusions in 1-2μm(70%).The Al_(2)O_(3)-MnS-CaO complex inclusions in the original steel changed to complex inclusions dominated by Cr-Nb-Mn-S-O and MgO.Al_(2)O_(3),corresponding to the MgO-Cr_(2)O_(3)-based and MgO-MgAl_(2)O_(4)-based refractories,respectively.The MgO.Al_(2)O_(3) layer was formed at the reaction interface between MgO-MgAl_(2)O_(4)-based refractory and molten steel,which is helpful to restrict the erosion of refractories and the pollution of molten steel.The damage mechanism of the MgO-Cr_(2)O_(3)-based refractory is mainly permeation and chemical reaction,while the damage of the MgO-MgAl_(2)O_(4)-based refractory is mainlyscouring erosion.
基金This work was supported by National Basic Research Program of China (No.2002CB312105)Key National Natural Science Foundation of China Project on Digital Olympic Museum(No.60533080).
文摘The emergence of high performance 3D graphics cards has opened the way to PC clusters for high performance multi- display environment. In order to exploit the rendering ability of PC clusters, we should design appropriate parallel rendering algorithms and parallel graphics library interfaces. Due to the rapid development of Direct3D, we bring forward DPGL, the Direct3D9-based parallel graphics library in D3DPR parallel rendering system, which implements Direct3D9 interfaces to support existing Direct3D9 application parallelization with no modification. Based on the parallelism analysis of Direct3D9 rendering pipeline, we briefly introduce D3DPR parallel rendering system. DPGL is the fundamental component of D3DPR. After presenting DPGL three layers architecture, we discuss the rendering resource interception and management. Finally, we describe the design and implementation of DPGL in detail, including rendering command interception layer, rendering command interpretation layer and rendering resource parallelization layer.
基金supported by National Natural Science Foundation of China (No. 12175127)Natural Science Foundation of Shandong Province,China (No. ZR2020MA088)
文摘The evolution of lead halide perovskites used for X-ray imaging scintillators has been facilitated by the development of solution-processable semiconductors characterized by large-area,flexible,fast photoresponse.The stability and durability of these new perovskites are insufficient to achieve extended computed tomography scanning times with hard X-rays.In this study,we fabricated a self-assembled CsPbBr_(3)-based scintillator film with a flexible large-area uniform thickness using a new roomtemperature solution-processable method.The sensitivity and responsivity of X-ray photon conversion were quantitatively measured and showed a good linear response relationship suitable for X-ray imaging.We also demonstrated,for the first time,that the self-assembled CsPbBr_(3)-based scintillator has good stability for hard X-ray microtomography.Therefore,such an inexpensive solution-processed semiconductor easily prepared at room temperature can be used as a hard X-ray scintillator and equipped with flexible CsPbBr3-based X-ray detectors.It has great potential in three-dimensional high-resolution phase-contrast X-ray-imaging applications in biomedicine and material science because of its heavy Pb and Br atoms.
