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
V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for N...V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.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
Cr_(2)O_(3)-bearing castables bonded with reactive MgO(RM)or calcium aluminate cement(CAC)were studied to evaluate the binder effect on their performance in corrosive environments.The properties of the as-prepared cas...Cr_(2)O_(3)-bearing castables bonded with reactive MgO(RM)or calcium aluminate cement(CAC)were studied to evaluate the binder effect on their performance in corrosive environments.The properties of the as-prepared castables were compared with respect to the differences in phase composition and microstructure.The corrosion behavior of the as-prepared castables by CaO-Al_(2)O_(3)-Fe_(2)O_(3)-SiO_(2)-based slag was systematically compared viarefractory cup testing at 1600℃with respect to the differences in phase composition and microstructure.The analysis indicates that RM bonded castables show higher apparent porosity,lower bulk density and strengths after drying at 110℃and firing at 1300℃,and higher permanent linear change after firing at 1300℃,but better slag corrosion and infiltration resistance compared with CAC bonded castables.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
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
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 (51372137)the National High Technology Research and Development Program of China (863 Program,2015AA034603)~~
文摘V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.
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the Joint Founds of R&D Program of Henan Province (222301420034)National Natural Science Foundation of China (51802287)Collaborative Innovation Major Special Project of Zhengzhou (No. 20XTZX12025) for the financial support
文摘Cr_(2)O_(3)-bearing castables bonded with reactive MgO(RM)or calcium aluminate cement(CAC)were studied to evaluate the binder effect on their performance in corrosive environments.The properties of the as-prepared castables were compared with respect to the differences in phase composition and microstructure.The corrosion behavior of the as-prepared castables by CaO-Al_(2)O_(3)-Fe_(2)O_(3)-SiO_(2)-based slag was systematically compared viarefractory cup testing at 1600℃with respect to the differences in phase composition and microstructure.The analysis indicates that RM bonded castables show higher apparent porosity,lower bulk density and strengths after drying at 110℃and firing at 1300℃,and higher permanent linear change after firing at 1300℃,but better slag corrosion and infiltration resistance compared with CAC bonded castables.
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.
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.
