CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive pro...CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive property was characterized by TPR. The results show that MnO2 can be dispersed in solid solution after calcined at 1273 K, when the loading is 12%, while Fe and Cu is easy to separate from samples at this temperature. Samples doped simultaneously by Fe, Mn or Fe, Cu demonstrated high reactive property at low temperature. The starting reduction temperature are 413 and 373 K, respectively. TPR results also show a broad range of reductive temperature exists in these bi-metal doped samples.展开更多
Influences of addition of CaO, CoO and V2O5 on the microstructure and magnetic properties of （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites were investigated. The powders of （Mg0.476Mn0.448Zn0.007） （Fe1.997...Influences of addition of CaO, CoO and V2O5 on the microstructure and magnetic properties of （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites were investigated. The powders of （Mg0.476Mn0.448Zn0.007） （Fe1.997Ti0.002）O4 composition were prepared by using a conventional ceramic powder processing technique. The experimental results showed that the average grain size of the sintered ferrites codoped with 0.03wt% CaO, 0.04wt% CoO and 0.06wt% V2O5 was about 15 μm; the saturation magnetization of ferrites was 68.78 emu/g. The addition of V2O5 in the ferrites can not only increase value of the saturation magnetization, but also decrease the average grain size of （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites. Simultaneous incorporation of CoO, CaO and V2O5 dopants into （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites can not only improve the saturation magnetization of the materials, but also inhibit abnormal grain growth.展开更多
The effects of microalloying elements Ti,Sc,Zr and Er on grain refinement behaviors and hardness properties of wedge-shaped Al-Mg-Mn alloy castings were investigated. The results indicate that alloys containing Sc and...The effects of microalloying elements Ti,Sc,Zr and Er on grain refinement behaviors and hardness properties of wedge-shaped Al-Mg-Mn alloy castings were investigated. The results indicate that alloys containing Sc and Zr can remarkably reduce the grain sizes of Al-Mg-Mn castings. Combination of Sc,Zr and Er can completely eliminate the columnar dendritic grains and further obtain refined grains with nondendritic sub-structure;the whole wedge-shaped cross-section of the casting consequently exhibits more homogeneous cast structures instead of the typical tri-crystal region structures. Large amounts of Al3Sc-based intermetallic compound particles,such as Al3(Sc1-x,Zrx),Al3(Sc1-x,Tix),Al3(Sc1-x-y,Zrx,Tiy) and Al3(Sc1-x-y,Zrx,Ery) are present in the microalloyed alloys,resulting from their numerously forming in high-temperature melt before solidification. These phases have the same L12-type crystal structure to Al3Sc phase as well as smaller misfits with the primary α(Al) grains,which leads to more efficient epitaxial growth for α(Al) grains on all crystal planes of these composite phases. The experimental alloys have been hardened in different levels and,show the low susceptibilities of hardness change with varying cooling rate. The high hardness of the castings are caused by grain-refined strengthening and solid solution strengthening.展开更多
Superparamagnetic monodisperse Mg0.8Mn0.2Fe2O4 nanoparticles have been successfully synthesized in liquid polyol at elevated temperature of 200 °C. Diethylene glycol（DEG） used here plays dual role in synthesis ...Superparamagnetic monodisperse Mg0.8Mn0.2Fe2O4 nanoparticles have been successfully synthesized in liquid polyol at elevated temperature of 200 °C. Diethylene glycol（DEG） used here plays dual role in synthesis as it acts as reducing agent and alternatively coats the surface of nanoparticles while synthesis and thereby maintaining uniform size and dispersibility. Powder X-ray diffraction（XRD） and magnetic measurements showed that the sample is cubic spinel and superparamagnetic at room temperature. Raman spectra confirmed the formation of the Mg0.8Mn0.2Fe2O4 nanoparticles.The nanoparticles exhibit very good stability in water due to in situ coating with DEG molecules.展开更多
The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that Fe...The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.展开更多
A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and character...A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and characterized by X-ray diffraction （XRD）, Raman spectroscopy, Brunauer-Emmett-Teller （BET） and H2-TPR measurements. Potential of the catalysts in the soot oxidation was evaluated in a temperature-programmed oxidation （TPO） apparatus. The results showed that all the Fe3＋ and Zr4＋ were incor- porated into ceria lattice to form a pure Ce-Fe-Zr-O solid solution for the co-precipitation sample, but two kinds of Fe phases ex- isted in the Ce-Fe-Zr-O catalysts prepared by other methods： Fe3＋ incorporated into CeO2 lattice and dispersed Fe2O3 clusters. The free Fe2O3 clusters could improve the activity of catalysts for soot oxidation comparing with the pure Ce-Fe-Zr-O solid solution owing to the synergetic effect between free Fe2O3 and surface oxygen vacancies. In addition, the activity of catalysts strongly relied on the surface reducibility of free Fe2O3 particles. Holding both abundant free Fe2O3 particles and high oxygen vacancy concentration, the hydrothermal Ce0.5Fe0.3Zr0.202 catalyst presented the lowest Ti （251℃, ignition temperature of soot oxidation） and Tm （310 ℃, maximum oxidation rate temperature） for soot combustion （with tight-contact between soot and catalysts） among the five samples. Even after aging at 800 ℃ for 10 h, the Ti and Tm were still relatively low, at 273 and 361 ℃, respectively, indicating high catalytic stability.展开更多
Selective laser melting(SLM)of aluminium alloys for lightweight application is arousing widespread interest,but the available alloy compositions are limited due to unsatisfactory mechanical performances.The rapid soli...Selective laser melting(SLM)of aluminium alloys for lightweight application is arousing widespread interest,but the available alloy compositions are limited due to unsatisfactory mechanical performances.The rapid solidifi cation of SLM provides a pathway to design a novel alloy composition with extended solubility.This strategy is demonstrated by an additively manufactured novel Al–2.51 Mn–2.71 Mg–0.55 Sc–0.29 Cu–0.31 Zn alloy with the supersaturated solid solution in the present study.The microstructure of as-build sample is characterized with multi-modal grains with the fi ne equiaxed grain(FEG,~800 nm)at molten pool boundaries,coarse equiaxed grain(CEG,~2μm)and columnar dendrites(CD,~4μm)inside the molten pool,which relates to the precipitations type and distribution.It is observable that Al 3(Sc,Zr)precipitation particles with the size of~50 nm are dispersed in the FEG zone,while the interior of CEG shows no Al3(Sc,Zr)particle which only exists at the CEG boundaries.Regardless of FEG,CEG or CD,the slender Al6 Mn precipitation with the length of~500 nm is distributed along the grain boundaries.Meanwhile,a lot of vacancies and thickness fringes are detected in the FEG zone,which confi rms the supersaturated solid solution in laser rapid solidifi cation.The ultimate tensile strength and yield strength of the as-printed sample are~380 MPa and~330 MPa,respectively,with elongation~14%,which increase to~440 MPa and~410 MPa with a reduction of elongation to~9%after heat treatment.展开更多
文摘CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive property was characterized by TPR. The results show that MnO2 can be dispersed in solid solution after calcined at 1273 K, when the loading is 12%, while Fe and Cu is easy to separate from samples at this temperature. Samples doped simultaneously by Fe, Mn or Fe, Cu demonstrated high reactive property at low temperature. The starting reduction temperature are 413 and 373 K, respectively. TPR results also show a broad range of reductive temperature exists in these bi-metal doped samples.
文摘Influences of addition of CaO, CoO and V2O5 on the microstructure and magnetic properties of （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites were investigated. The powders of （Mg0.476Mn0.448Zn0.007） （Fe1.997Ti0.002）O4 composition were prepared by using a conventional ceramic powder processing technique. The experimental results showed that the average grain size of the sintered ferrites codoped with 0.03wt% CaO, 0.04wt% CoO and 0.06wt% V2O5 was about 15 μm; the saturation magnetization of ferrites was 68.78 emu/g. The addition of V2O5 in the ferrites can not only increase value of the saturation magnetization, but also decrease the average grain size of （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites. Simultaneous incorporation of CoO, CaO and V2O5 dopants into （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites can not only improve the saturation magnetization of the materials, but also inhibit abnormal grain growth.
文摘The effects of microalloying elements Ti,Sc,Zr and Er on grain refinement behaviors and hardness properties of wedge-shaped Al-Mg-Mn alloy castings were investigated. The results indicate that alloys containing Sc and Zr can remarkably reduce the grain sizes of Al-Mg-Mn castings. Combination of Sc,Zr and Er can completely eliminate the columnar dendritic grains and further obtain refined grains with nondendritic sub-structure;the whole wedge-shaped cross-section of the casting consequently exhibits more homogeneous cast structures instead of the typical tri-crystal region structures. Large amounts of Al3Sc-based intermetallic compound particles,such as Al3(Sc1-x,Zrx),Al3(Sc1-x,Tix),Al3(Sc1-x-y,Zrx,Tiy) and Al3(Sc1-x-y,Zrx,Ery) are present in the microalloyed alloys,resulting from their numerously forming in high-temperature melt before solidification. These phases have the same L12-type crystal structure to Al3Sc phase as well as smaller misfits with the primary α(Al) grains,which leads to more efficient epitaxial growth for α(Al) grains on all crystal planes of these composite phases. The experimental alloys have been hardened in different levels and,show the low susceptibilities of hardness change with varying cooling rate. The high hardness of the castings are caused by grain-refined strengthening and solid solution strengthening.
基金the Council of Scientific and Industrial Research, India for the award of senior research fellowship (File. 09/1077/(0001)/ 2012/EMR-1)
文摘Superparamagnetic monodisperse Mg0.8Mn0.2Fe2O4 nanoparticles have been successfully synthesized in liquid polyol at elevated temperature of 200 °C. Diethylene glycol（DEG） used here plays dual role in synthesis as it acts as reducing agent and alternatively coats the surface of nanoparticles while synthesis and thereby maintaining uniform size and dispersibility. Powder X-ray diffraction（XRD） and magnetic measurements showed that the sample is cubic spinel and superparamagnetic at room temperature. Raman spectra confirmed the formation of the Mg0.8Mn0.2Fe2O4 nanoparticles.The nanoparticles exhibit very good stability in water due to in situ coating with DEG molecules.
基金Item Sponsored by National Natural Science Foundation of China (51090382)
文摘The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.
基金Project supported by National Natural Science Foundation of China(51374004,51204083,51174105,51104074)Natural Science Foundation of Yunnan Province(2010ZC018)
文摘A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and characterized by X-ray diffraction （XRD）, Raman spectroscopy, Brunauer-Emmett-Teller （BET） and H2-TPR measurements. Potential of the catalysts in the soot oxidation was evaluated in a temperature-programmed oxidation （TPO） apparatus. The results showed that all the Fe3＋ and Zr4＋ were incor- porated into ceria lattice to form a pure Ce-Fe-Zr-O solid solution for the co-precipitation sample, but two kinds of Fe phases ex- isted in the Ce-Fe-Zr-O catalysts prepared by other methods： Fe3＋ incorporated into CeO2 lattice and dispersed Fe2O3 clusters. The free Fe2O3 clusters could improve the activity of catalysts for soot oxidation comparing with the pure Ce-Fe-Zr-O solid solution owing to the synergetic effect between free Fe2O3 and surface oxygen vacancies. In addition, the activity of catalysts strongly relied on the surface reducibility of free Fe2O3 particles. Holding both abundant free Fe2O3 particles and high oxygen vacancy concentration, the hydrothermal Ce0.5Fe0.3Zr0.202 catalyst presented the lowest Ti （251℃, ignition temperature of soot oxidation） and Tm （310 ℃, maximum oxidation rate temperature） for soot combustion （with tight-contact between soot and catalysts） among the five samples. Even after aging at 800 ℃ for 10 h, the Ti and Tm were still relatively low, at 273 and 361 ℃, respectively, indicating high catalytic stability.
基金the National Natural Science Foundation of China(51871249)the Guangxi Key Research and Development Programme(Guike AB19050002)+3 种基金the Science and Technology Planning Project of Shenzhen(JCYJ20180508151903646)the Hunan Science Fund for Distinguished Young Scholars(2020JJ2046)Natural Science Foundation of Shandong Province(ZR2020ZD04)the Huxiang Youth Talent Support Programme(2018RS3007)。
文摘Selective laser melting(SLM)of aluminium alloys for lightweight application is arousing widespread interest,but the available alloy compositions are limited due to unsatisfactory mechanical performances.The rapid solidifi cation of SLM provides a pathway to design a novel alloy composition with extended solubility.This strategy is demonstrated by an additively manufactured novel Al–2.51 Mn–2.71 Mg–0.55 Sc–0.29 Cu–0.31 Zn alloy with the supersaturated solid solution in the present study.The microstructure of as-build sample is characterized with multi-modal grains with the fi ne equiaxed grain(FEG,~800 nm)at molten pool boundaries,coarse equiaxed grain(CEG,~2μm)and columnar dendrites(CD,~4μm)inside the molten pool,which relates to the precipitations type and distribution.It is observable that Al 3(Sc,Zr)precipitation particles with the size of~50 nm are dispersed in the FEG zone,while the interior of CEG shows no Al3(Sc,Zr)particle which only exists at the CEG boundaries.Regardless of FEG,CEG or CD,the slender Al6 Mn precipitation with the length of~500 nm is distributed along the grain boundaries.Meanwhile,a lot of vacancies and thickness fringes are detected in the FEG zone,which confi rms the supersaturated solid solution in laser rapid solidifi cation.The ultimate tensile strength and yield strength of the as-printed sample are~380 MPa and~330 MPa,respectively,with elongation~14%,which increase to~440 MPa and~410 MPa with a reduction of elongation to~9%after heat treatment.
