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
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
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 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
Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions.We proposed a novel strategy to improve the purification performance of Al_(2)O_(3)-based ceramic fi...Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions.We proposed a novel strategy to improve the purification performance of Al_(2)O_(3)-based ceramic filters by using microporous corundum-spinel raw materials to replace dense raw materials.Three kinds of Al_(2)O_(3)-based ceramic filters fabricated from dense α-Al_(2)O_(3) micro-powder or microporous corundum-spinel powder were selected to carry out the immersion tests with molten steel.On the one hand,the higher surface roughness of the filter skeleton prepared from microporous raw materials increased the adsorption capacity of skeleton surface on inclusions in molten steel.On the other hand,the higher apparent porosity and larger pore size of the filter skeleton were more beneficial to the penetration of molten steel in the micropores of skeleton.The reaction process at the solid-liquid interface also improved the wettability of the interface between skeleton and molten steel,resulting in a larger penetration depth and a better adsorption effect on the inclusions.In summary,the novel Al_(2)O_(3)-based ceramic filter prepared with microporous corundum-spinel powder and addition of 5 wt.% nano-Al_(2)O_(3) powder reduced the total oxygen content of the steel from 40.2×10^(-4) to 12.7×10^(-4) wt.% by 68.4% and the Al content from 0.46 to 0.18 wt.% by 60.9% after immersion test,presenting the most excellent purification performance on molten steel.展开更多
This paper reports the formation and some properties of a new class of chalcohalide glasses in the As2Tef iodide systems. The As2Te3-Pb12, As2Te3-HgI2, As2Te3-CitI and As2Te3-AgI systems can form stable bulk glasses i...This paper reports the formation and some properties of a new class of chalcohalide glasses in the As2Tef iodide systems. The As2Te3-Pb12, As2Te3-HgI2, As2Te3-CitI and As2Te3-AgI systems can form stable bulk glasses in wide composition regions ?and no bulk glass formation was found in the As2Te3-TH sys-tem. As2Te3-based glasses have glass transition tempera-展开更多
Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by dire...Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by direct Sb doping method.It can be found that doping Sb into Bi_(2)Te_(3) lattice array for Bi-site replacement facilitates the generation of Sb′Te anti-site defects.This anti-site defects can increase the hole concentration and optimize electrical transport properties of Bi_(2−x)Sb_(x)Te_(3) alloys.In addition,the point defects induced by mass and stress fluctuations and the Sb impurities produced during the sintering process can enhance the multi-scale phonon scattering and reduce the lattice thermal conductivity.As a result,the Bi_(0.47)Sb_(1.63)Te_(3) sample has a maximum thermoelectric figure of merit ZT of 1.04 at 350 K.It is worth noting that the bipolar effect of Bi_(2)Te_(3)-based alloys can be weakened with the increase of Sb content.The Bi_(0.44)Sb_(1.66)Te_(3) sample has a maximum average ZT value(0.93)in the temperature range of 300–500 K,indicating that direct doping of Sb can broaden the temperature range corresponding to the optimal ZT value.This work provides an idea for developing high-performance near room temperature thermoelectric materials with a wide temperature range.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
In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent ...In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. 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 effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.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
Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric...Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric（TE）measurements indicate that optimal thickness and thickness ratio improve the TE performance of Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices, respectively. High TE performances with figure-of-merit（ZT） values as high as 1.32 and 1.56 are achieved at 443 K for 30 nm and 50 nm Bi_2Te_3 thin films, respectively. These ZT values are higher than those of p-type Bi_2Te_3 alloys as reported. Relatively high ZT of the GeTe/B_2Te_3 superlattices at 300-380 K were 0.62-0.76. The achieved high ZT value may be attributed to the unique nano-and microstructures of the films,which increase phonon scattering and reduce thermal conductivity. The results indicate that Bi_2Te_3-based thin films can serve as high-performance materials for applications in TE devices.展开更多
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
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
We develop a tractable theoretical model to investigate the thermoelectric （TE） transport properties of surface states in topological insulator thin films （TITFs） of Bi2Sea at room temperature. The hybridization b...We develop a tractable theoretical model to investigate the thermoelectric （TE） transport properties of surface states in topological insulator thin films （TITFs） of Bi2Sea at room temperature. The hybridization between top and bottom surface states in the TITF plays a significant role. With the increasing hybridization-induced surface gap, the electrical conductivity and electron thermal conductivity decrease while the Seebeck coefficient increases. This is due to the metal-semiconductor transition induced by the surface-state hybridization. Based on these TE transport coefficients, the TE figure-of-merit ZT is evaluated. It is shown that ZT can be greatly improved by the surface-state hybridization. Our theoretical results are pertinent to the exploration of the TE transport properties of surface states in TITFs and to the potential application of Bi2Sea-based TITFs as high-performance TE materials and devices.展开更多
Solid ceramic electrolyte materials (Bi_2O_3)_(0.75)(Y_2O_3)_(0.25) and(Bi_2O_3)_(0.65)(Gd_2O_3 )_(0.35)were synthesized.Their crystal structure, XPS spectra and the change of ionic conductivity versus temperature wer...Solid ceramic electrolyte materials (Bi_2O_3)_(0.75)(Y_2O_3)_(0.25) and(Bi_2O_3)_(0.65)(Gd_2O_3 )_(0.35)were synthesized.Their crystal structure, XPS spectra and the change of ionic conductivity versus temperature were measured.A Bi_2O_3-based rare earth solid electrolyte fuel cell with ZrO_2-Y_2O_3 protection film was made.展开更多
Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)...Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)Te_(3)focus on band and microstructure engineering.However,a clear understanding of the modulation of band structure and scattering through such engineering remains still challenging,because the minority carriers compensate partially the overall transport properties for the narrow-gap Bi_(2)Te_(3)at room temperature(known as the bipolar effect).The purpose of this work is to model the transport properties near and far away from the bipolar effect region for Bi_(2)Te_(3)-based thermoelectric material by a two-band model taking contributions of both majority and minority carriers into account.This is endowed by shifting the Fermi level from the conduction band to the valence band during the modeling.A large amount of data of Bi_(2)Te_(3)-based materials is collected from various studies for the comparison between experimental and predicted properties.The fundamental parameters,such as the density of states effective masses and deformation potential coefficients,of Bi_(2)Te_(3)-based materials are quantified.The analysis can help find out the impact factors(e.g.the mobility ratio between conduction and valence bands)for the improvement of thermoelectric properties for Bi_(2)Te_(3)-based alloys.This work provides a convenient tool for analyzing and predicting the transport performance even in the presence of bipolar effect,which can facilitate the development of the narrow-gap thermoelectric semiconductors.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
基金financially supported by the National Natural Science Foundation of China(No.52171046)National Natural Science Foundation of China-key programme(No.52234010)the Fundamental Research Funds for the Central Universities and Shaanxi Provincial Key Science and Technology Innovation Team(No.2023-CX-TD-14).
文摘Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.
基金supported by the National Natural Science Foundation of China(Grant 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financially supported by the National Natural Science Foundation of China(Grant No.51974214).
文摘Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions.We proposed a novel strategy to improve the purification performance of Al_(2)O_(3)-based ceramic filters by using microporous corundum-spinel raw materials to replace dense raw materials.Three kinds of Al_(2)O_(3)-based ceramic filters fabricated from dense α-Al_(2)O_(3) micro-powder or microporous corundum-spinel powder were selected to carry out the immersion tests with molten steel.On the one hand,the higher surface roughness of the filter skeleton prepared from microporous raw materials increased the adsorption capacity of skeleton surface on inclusions in molten steel.On the other hand,the higher apparent porosity and larger pore size of the filter skeleton were more beneficial to the penetration of molten steel in the micropores of skeleton.The reaction process at the solid-liquid interface also improved the wettability of the interface between skeleton and molten steel,resulting in a larger penetration depth and a better adsorption effect on the inclusions.In summary,the novel Al_(2)O_(3)-based ceramic filter prepared with microporous corundum-spinel powder and addition of 5 wt.% nano-Al_(2)O_(3) powder reduced the total oxygen content of the steel from 40.2×10^(-4) to 12.7×10^(-4) wt.% by 68.4% and the Al content from 0.46 to 0.18 wt.% by 60.9% after immersion test,presenting the most excellent purification performance on molten steel.
文摘This paper reports the formation and some properties of a new class of chalcohalide glasses in the As2Tef iodide systems. The As2Te3-Pb12, As2Te3-HgI2, As2Te3-CitI and As2Te3-AgI systems can form stable bulk glasses in wide composition regions ?and no bulk glass formation was found in the As2Te3-TH sys-tem. As2Te3-based glasses have glass transition tempera-
基金supported by the Anhui Province Natural Science Foundation for Excellent Youth Scholars(2208085Y17)the University Synergy Innovation Program of Anhui Province(GXXT-2022-008+1 种基金GXXT-2021-022)the Anhui Key Lab of Metal Material and Processing Open Project.
文摘Doping modification is one of the most effective ways to optimize the thermoelectric properties of Bi_(2)Te_(3)-based alloys.P-type Bi_(2−x)Sb_(x)Te_(3) thermoelectric materials have been successfully prepared by direct Sb doping method.It can be found that doping Sb into Bi_(2)Te_(3) lattice array for Bi-site replacement facilitates the generation of Sb′Te anti-site defects.This anti-site defects can increase the hole concentration and optimize electrical transport properties of Bi_(2−x)Sb_(x)Te_(3) alloys.In addition,the point defects induced by mass and stress fluctuations and the Sb impurities produced during the sintering process can enhance the multi-scale phonon scattering and reduce the lattice thermal conductivity.As a result,the Bi_(0.47)Sb_(1.63)Te_(3) sample has a maximum thermoelectric figure of merit ZT of 1.04 at 350 K.It is worth noting that the bipolar effect of Bi_(2)Te_(3)-based alloys can be weakened with the increase of Sb content.The Bi_(0.44)Sb_(1.66)Te_(3) sample has a maximum average ZT value(0.93)in the temperature range of 300–500 K,indicating that direct doping of Sb can broaden the temperature range corresponding to the optimal ZT value.This work provides an idea for developing high-performance near room temperature thermoelectric materials with a wide temperature range.
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.
基金Supported by National Natural Science Foundation of China(Grant No.51175305)
文摘In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. 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 effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.
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.
文摘Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric（TE）measurements indicate that optimal thickness and thickness ratio improve the TE performance of Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices, respectively. High TE performances with figure-of-merit（ZT） values as high as 1.32 and 1.56 are achieved at 443 K for 30 nm and 50 nm Bi_2Te_3 thin films, respectively. These ZT values are higher than those of p-type Bi_2Te_3 alloys as reported. Relatively high ZT of the GeTe/B_2Te_3 superlattices at 300-380 K were 0.62-0.76. The achieved high ZT value may be attributed to the unique nano-and microstructures of the films,which increase phonon scattering and reduce thermal conductivity. The results indicate that Bi_2Te_3-based thin films can serve as high-performance materials for applications in TE devices.
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.
基金Supported by the National Natural Science Foundation of China under Grant No 11304316the Ministry of Science and Technology of China under Grant No 2011YQ130018the Department of Science and Technology of Yunnan Province,and the Chinese Academy of Sciences
文摘We develop a tractable theoretical model to investigate the thermoelectric （TE） transport properties of surface states in topological insulator thin films （TITFs） of Bi2Sea at room temperature. The hybridization between top and bottom surface states in the TITF plays a significant role. With the increasing hybridization-induced surface gap, the electrical conductivity and electron thermal conductivity decrease while the Seebeck coefficient increases. This is due to the metal-semiconductor transition induced by the surface-state hybridization. Based on these TE transport coefficients, the TE figure-of-merit ZT is evaluated. It is shown that ZT can be greatly improved by the surface-state hybridization. Our theoretical results are pertinent to the exploration of the TE transport properties of surface states in TITFs and to the potential application of Bi2Sea-based TITFs as high-performance TE materials and devices.
文摘Solid ceramic electrolyte materials (Bi_2O_3)_(0.75)(Y_2O_3)_(0.25) and(Bi_2O_3)_(0.65)(Gd_2O_3 )_(0.35)were synthesized.Their crystal structure, XPS spectra and the change of ionic conductivity versus temperature were measured.A Bi_2O_3-based rare earth solid electrolyte fuel cell with ZrO_2-Y_2O_3 protection film was made.
基金National Natural Science Foundation of China(T2125008,92263108,92163203,52102292,52003198)Shanghai Rising-Star Program(23QA1409300)Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-07-E00096)。
文摘Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)Te_(3)focus on band and microstructure engineering.However,a clear understanding of the modulation of band structure and scattering through such engineering remains still challenging,because the minority carriers compensate partially the overall transport properties for the narrow-gap Bi_(2)Te_(3)at room temperature(known as the bipolar effect).The purpose of this work is to model the transport properties near and far away from the bipolar effect region for Bi_(2)Te_(3)-based thermoelectric material by a two-band model taking contributions of both majority and minority carriers into account.This is endowed by shifting the Fermi level from the conduction band to the valence band during the modeling.A large amount of data of Bi_(2)Te_(3)-based materials is collected from various studies for the comparison between experimental and predicted properties.The fundamental parameters,such as the density of states effective masses and deformation potential coefficients,of Bi_(2)Te_(3)-based materials are quantified.The analysis can help find out the impact factors(e.g.the mobility ratio between conduction and valence bands)for the improvement of thermoelectric properties for Bi_(2)Te_(3)-based alloys.This work provides a convenient tool for analyzing and predicting the transport performance even in the presence of bipolar effect,which can facilitate the development of the narrow-gap thermoelectric semiconductors.
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.
