Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sinter...Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the SmzO3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900℃. The results indicated that the ionic conductivities of Srno.2oCe0.8Ol.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the An＇henius equation. Then the SmzO3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.展开更多
Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A...Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33 Mn0.33Ti0.6703（A = Ca or Sr and Ln = rare earth） were found to have orthorhombic symmetry with the space group Pnrna, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Cao.67Ln0.33Mn0.33Ti0.6703 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.展开更多
Among complex oxides containing rare earth and manganese BaLn_2Mn_2O_7 (Ln=rare earth) with the layered perovskite type and Ln_2(Mn, M)O_7 with pyrochlore-related structure were studied since these compounds show many...Among complex oxides containing rare earth and manganese BaLn_2Mn_2O_7 (Ln=rare earth) with the layered perovskite type and Ln_2(Mn, M)O_7 with pyrochlore-related structure were studied since these compounds show many kinds of phases and unique phase transitions. In BaLn_2Mn_2O_7 there appear many phases, depending on the synthetic conditions for each rare earth. The tetragonal phase of so-called Ruddlesden-Popper type is the fundamental structure and many kinds of deformed modification of this structure are obtained. For BaEu_2Mn_2O_7 at least five phases have been identified from the results of X-ray diffraction analysis with the space group P4_2/mnm, Fmmm, Immm and A2/m in addition to the fundamental tetragonal I4/mmm phase. In the pyrochlore-related type compounds, Ln_2Mn_(2-x)M_xO_7 (M=Ta, Nb, W etc), there also appear several phases with different crystal structures. With regard to every rare earth, Ln_2MnTaO_7 phase is stable only for excess Ta and can be obtained under high oxygen partial pressure process. This group has trigonal structure with zirkelite type (P3_121 space group). On the other hand Ln_2Mn_(2/3)Nb_(4/3)O_7 phase has monoclinic (C2/c space group) and zirconolite type structure. All of these structural models have the fundamental structure based on HTB (hexagonal tungsten bronze) layers formed by the arrangement of oxygen octahedra.展开更多
It can be known from a large number of research results that improving the dispersibility of CNTs can effectively optimize the mechanical properties of the corresponding metal matrix composites.However,the crucial iss...It can be known from a large number of research results that improving the dispersibility of CNTs can effectively optimize the mechanical properties of the corresponding metal matrix composites.However,the crucial issue of increasing the bonding of CNTs and the matrix is still unsolved.In this paper,a novel method was developed to increase interfacial bonding strength by coating titanium oxide(TiO2)on the surface of CNTs.The rare earth Pr and TiO2@CNTs-reinforced AZ91matrix composites were successfully fabricated by powder metallurgy.Hot press sintering and hot extrusion of the milled powder was performed.After hot extrusion,the influence of TiO2@CNTs on the microstruc-ture and mechanical properties of the composites were investigated.The results showed that the coating process can improve the distribution of CNTs in Mg alloy.The CNTs refined the grains of the matrix,and the CNTs were presented throughout the extrusion direction.When the TiO2@CNTs content was 1.0 wt.%,the yield strength(YS),ultimate ten-sile strength(UTS),and elongation of the alloy attained maximum values.The values were improved by 23.5%,82.1%,and 40.0%,respectively,when compared with the AZ91 alloy.Good interfacial bonding was achieved,which resulted in an effective tensile loading transfer at the interface.CNTs carried the tensile stress and were observed on the tensile fracture.展开更多
Many phases appear in BaLn 2Mn 2O 7 family (Ln=rare earth) belonging to one of the Ruddlesden-Popper type compounds, depending upon the experimental conditions such as heating conditions when prepared and compositi...Many phases appear in BaLn 2Mn 2O 7 family (Ln=rare earth) belonging to one of the Ruddlesden-Popper type compounds, depending upon the experimental conditions such as heating conditions when prepared and composition. Some of these phases were characterized by powder X-ray diffraction method using Rietveld analysis. These phases have only a little difference in crystal structure which has fundamentally K 2NiF 4 type structure, although the X-ray diffraction patterns are clearly different: a little deformation or tilting of the oxygen octahedron surrounding a central manganese ion composing the main frame of this structure induce these different diffraction patterns. Phase behavior of these compounds, mainly the detailed relation between various phases in BaTb 2Mn 2O 7, was refined including the data of high temperature X-ray diffractometry.展开更多
Rare earth-based AB(5)-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the m...Rare earth-based AB(5)-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the metahydride hydrogen-diffusion electrodes could be charged by hydrogen gas and electrochemically discharged, at the same time to retain a stable oxidation potential for a long period. The catalytic activities and stability are almost comparable with a Pt catalyst on the active carbon. Further improvement of performances is expected via reduction of catalyst size into nanometers.展开更多
The catalytic performance of oxidative coupling of methane(OCM) over Eu 2O 3 catalysts promoted by alkaline earth fluorides was studied The results showed that C 2 hydrocarbon selectivity and yield over the fluor...The catalytic performance of oxidative coupling of methane(OCM) over Eu 2O 3 catalysts promoted by alkaline earth fluorides was studied The results showed that C 2 hydrocarbon selectivity and yield over the fluoride promoted Eu 2O 3 catalysts were apparently higher than those over pure Eu 2O 3; the OCM performance increased according to the sequence of CaF 2 Eu 2O 3≈BaF 2 Eu 2O 3<SrF 2 Eu 2O 3 under the same conditions XRD experiment indicated that rhombohedral EuOF phase formed in the fresh BaF 2 Eu 2O 3 catalyst, while the exchange of F - and O 2- did not apparently happen in the fresh CaF 2 Eu 2O 3 and SrF 2 Eu 2O 3 catalysts Pyridine TPD and CO 2 TPD measurements found that, after adding SrF 2 to Eu 2O 3, the catalyst surface acidity decreased, whereas the surface basic strength increased slightly, resulting in an improvement in C 2 selectivity and yield展开更多
Rare earth-doped copper-manganese mixed oxide catalysts were prepared by coprecipitation and mechanical mixing using copper sulfate, manganese sulfate, and rare-earth oxides REO （REO indicates La2O3, CeO2, Y2O3, or P...Rare earth-doped copper-manganese mixed oxide catalysts were prepared by coprecipitation and mechanical mixing using copper sulfate, manganese sulfate, and rare-earth oxides REO （REO indicates La2O3, CeO2, Y2O3, or Pr6O11） as raw materials. The samples were characterized by X-ray diffraction （XRD）, temperature-programmed reduction （TPR）, temperature-programmed reduc-tion of oxidized surfaces （s-TPR）, and temperature-programmed desorption （TPD）. Catalytic activities were tested for a water-gas shift reaction. Doping rare earth oxides did not alter the crystal structure of the original copper-manganese mixed oxides but changed the interplanar spacing, adsorption performance and reaction performance. Doping with La2O3 enhanced the activity and stability of Cu-Mn mixed oxides because of high copper distribution and fine reduction. Doping with CeO2 and Y2O3 also decreased the reduc-tion temperatures of the samples to different degrees while improving the dispersion of Cu on the surface, thus, catalytic activity was better than that of undoped Cu-Mn sample. The Pr6O11-doped sample was difficult to reduce, the dispersion of surface coppers was lowered, resulting in poor activity.展开更多
Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides (La2O3, Nd2O3 and Y2O3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing p...Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides (La2O3, Nd2O3 and Y2O3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing process. The viscosity of the molten ma-terials, bio-solubility and crystallization behavior of the fiber were investigated. The results indicated that the fiber drawing tempera-ture range could be broadened since the slope of the temperature-viscosity curve decreased with adding rare earth oxide. The addition of rare earth oxide was beneficial to the increase of crystallization temperature by strengthening the network structure of the fiber. The existence of rare earth oxide in the fibers would reduce the solubility of the fibers, which still belonged to bio-soluble fibers.展开更多
Mesoporous TiO2-CeO2 mixed oxide(m-TiO2-CeO2) were synthesized using n-cetylpyridinium chloride (C16PyCl) as a structure-directing agent under the neutral conditions and room temperature. The synthesized mesoporous sa...Mesoporous TiO2-CeO2 mixed oxide(m-TiO2-CeO2) were synthesized using n-cetylpyridinium chloride (C16PyCl) as a structure-directing agent under the neutral conditions and room temperature. The synthesized mesoporous samples were characterized by FT-IR, XRD, and N2 adsorption BET methods. The incorporation of Ce3+ ions into the channel wall improves the stability of the mesoporous structure obviously. After ruthenium being loaded by the impregnating method, the Ru particle strongly interacts with the mesoporous mixed supports. Although a part of the particles are possible to block the support pores, the catalytic activity of ruthenium supported on the m-TiO2-CeO2 for methanol decomposition to carbon monoxide and hydrogen is significantly higher than that of ruthenium supported on m-TiO2. A synergistic effect between CeO2 and TiO2 was observed for promoting the catalytic properties of Ru.展开更多
Spinel lithium manganese oxides doped with rare earth elements in forms of LiM 0.02 Mn 1.98 O 4 (M=La, Pr and Sm) were prepared and their electrochemical properties for lithium ion intercalation reaction were investig...Spinel lithium manganese oxides doped with rare earth elements in forms of LiM 0.02 Mn 1.98 O 4 (M=La, Pr and Sm) were prepared and their electrochemical properties for lithium ion intercalation reaction were investigated. The materials were prepared by solid state reaction using electrolytic MnO 2, Li 2CO 3 with Pr 2O 3, Sm 2O 3 or La(NO 3) 3·H 2O. From the voltammetry test it was found that the reversibility of lithium intercalation reaction could be improved by doping with Sm or Pr into spinel lithium manganese oxides. Although the first discharge capacity was decreased by about 10% for LiPr 0.02 Mn 1.98 O 4 and LiSm 0.02 Mn 1.98 O 4 compounds compared with undoped LiMn 2O 4, but their cycling properties were improved, obviously.展开更多
文摘Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the SmzO3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900℃. The results indicated that the ionic conductivities of Srno.2oCe0.8Ol.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the An＇henius equation. Then the SmzO3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.
基金Foundation ite ms:Project supported bythe Grant-in-Aidfor Scientific Research (C) (18560662) bythe Japan Societyfor the Promotion of Science
文摘Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33 Mn0.33Ti0.6703（A = Ca or Sr and Ln = rare earth） were found to have orthorhombic symmetry with the space group Pnrna, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Cao.67Ln0.33Mn0.33Ti0.6703 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.
文摘Among complex oxides containing rare earth and manganese BaLn_2Mn_2O_7 (Ln=rare earth) with the layered perovskite type and Ln_2(Mn, M)O_7 with pyrochlore-related structure were studied since these compounds show many kinds of phases and unique phase transitions. In BaLn_2Mn_2O_7 there appear many phases, depending on the synthetic conditions for each rare earth. The tetragonal phase of so-called Ruddlesden-Popper type is the fundamental structure and many kinds of deformed modification of this structure are obtained. For BaEu_2Mn_2O_7 at least five phases have been identified from the results of X-ray diffraction analysis with the space group P4_2/mnm, Fmmm, Immm and A2/m in addition to the fundamental tetragonal I4/mmm phase. In the pyrochlore-related type compounds, Ln_2Mn_(2-x)M_xO_7 (M=Ta, Nb, W etc), there also appear several phases with different crystal structures. With regard to every rare earth, Ln_2MnTaO_7 phase is stable only for excess Ta and can be obtained under high oxygen partial pressure process. This group has trigonal structure with zirkelite type (P3_121 space group). On the other hand Ln_2Mn_(2/3)Nb_(4/3)O_7 phase has monoclinic (C2/c space group) and zirconolite type structure. All of these structural models have the fundamental structure based on HTB (hexagonal tungsten bronze) layers formed by the arrangement of oxygen octahedra.
基金Supported by National Natural Science Foundation of China(Grant No.51965040)Loading Program of Science and Technology of College of Jiangxi Province(Grant No.KJLD14003).
文摘It can be known from a large number of research results that improving the dispersibility of CNTs can effectively optimize the mechanical properties of the corresponding metal matrix composites.However,the crucial issue of increasing the bonding of CNTs and the matrix is still unsolved.In this paper,a novel method was developed to increase interfacial bonding strength by coating titanium oxide(TiO2)on the surface of CNTs.The rare earth Pr and TiO2@CNTs-reinforced AZ91matrix composites were successfully fabricated by powder metallurgy.Hot press sintering and hot extrusion of the milled powder was performed.After hot extrusion,the influence of TiO2@CNTs on the microstruc-ture and mechanical properties of the composites were investigated.The results showed that the coating process can improve the distribution of CNTs in Mg alloy.The CNTs refined the grains of the matrix,and the CNTs were presented throughout the extrusion direction.When the TiO2@CNTs content was 1.0 wt.%,the yield strength(YS),ultimate ten-sile strength(UTS),and elongation of the alloy attained maximum values.The values were improved by 23.5%,82.1%,and 40.0%,respectively,when compared with the AZ91 alloy.Good interfacial bonding was achieved,which resulted in an effective tensile loading transfer at the interface.CNTs carried the tensile stress and were observed on the tensile fracture.
文摘Many phases appear in BaLn 2Mn 2O 7 family (Ln=rare earth) belonging to one of the Ruddlesden-Popper type compounds, depending upon the experimental conditions such as heating conditions when prepared and composition. Some of these phases were characterized by powder X-ray diffraction method using Rietveld analysis. These phases have only a little difference in crystal structure which has fundamentally K 2NiF 4 type structure, although the X-ray diffraction patterns are clearly different: a little deformation or tilting of the oxygen octahedron surrounding a central manganese ion composing the main frame of this structure induce these different diffraction patterns. Phase behavior of these compounds, mainly the detailed relation between various phases in BaTb 2Mn 2O 7, was refined including the data of high temperature X-ray diffractometry.
文摘Rare earth-based AB(5)-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the metahydride hydrogen-diffusion electrodes could be charged by hydrogen gas and electrochemically discharged, at the same time to retain a stable oxidation potential for a long period. The catalytic activities and stability are almost comparable with a Pt catalyst on the active carbon. Further improvement of performances is expected via reduction of catalyst size into nanometers.
文摘The catalytic performance of oxidative coupling of methane(OCM) over Eu 2O 3 catalysts promoted by alkaline earth fluorides was studied The results showed that C 2 hydrocarbon selectivity and yield over the fluoride promoted Eu 2O 3 catalysts were apparently higher than those over pure Eu 2O 3; the OCM performance increased according to the sequence of CaF 2 Eu 2O 3≈BaF 2 Eu 2O 3<SrF 2 Eu 2O 3 under the same conditions XRD experiment indicated that rhombohedral EuOF phase formed in the fresh BaF 2 Eu 2O 3 catalyst, while the exchange of F - and O 2- did not apparently happen in the fresh CaF 2 Eu 2O 3 and SrF 2 Eu 2O 3 catalysts Pyridine TPD and CO 2 TPD measurements found that, after adding SrF 2 to Eu 2O 3, the catalyst surface acidity decreased, whereas the surface basic strength increased slightly, resulting in an improvement in C 2 selectivity and yield
基金Project supported by National Natural Science Foundation of China(21066008,21266017)Inner Mongolia Science and Technology Plan Project(20101502)
文摘Rare earth-doped copper-manganese mixed oxide catalysts were prepared by coprecipitation and mechanical mixing using copper sulfate, manganese sulfate, and rare-earth oxides REO （REO indicates La2O3, CeO2, Y2O3, or Pr6O11） as raw materials. The samples were characterized by X-ray diffraction （XRD）, temperature-programmed reduction （TPR）, temperature-programmed reduc-tion of oxidized surfaces （s-TPR）, and temperature-programmed desorption （TPD）. Catalytic activities were tested for a water-gas shift reaction. Doping rare earth oxides did not alter the crystal structure of the original copper-manganese mixed oxides but changed the interplanar spacing, adsorption performance and reaction performance. Doping with La2O3 enhanced the activity and stability of Cu-Mn mixed oxides because of high copper distribution and fine reduction. Doping with CeO2 and Y2O3 also decreased the reduc-tion temperatures of the samples to different degrees while improving the dispersion of Cu on the surface, thus, catalytic activity was better than that of undoped Cu-Mn sample. The Pr6O11-doped sample was difficult to reduce, the dispersion of surface coppers was lowered, resulting in poor activity.
基金supported by the National Basic Research Program of China(973 Program)(2014CB660802)the National Natural Science Foundation of China(51474166)Natural Science Foundation of Hubei Province(2012FFA102)
文摘Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides (La2O3, Nd2O3 and Y2O3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing process. The viscosity of the molten ma-terials, bio-solubility and crystallization behavior of the fiber were investigated. The results indicated that the fiber drawing tempera-ture range could be broadened since the slope of the temperature-viscosity curve decreased with adding rare earth oxide. The addition of rare earth oxide was beneficial to the increase of crystallization temperature by strengthening the network structure of the fiber. The existence of rare earth oxide in the fibers would reduce the solubility of the fibers, which still belonged to bio-soluble fibers.
文摘Mesoporous TiO2-CeO2 mixed oxide(m-TiO2-CeO2) were synthesized using n-cetylpyridinium chloride (C16PyCl) as a structure-directing agent under the neutral conditions and room temperature. The synthesized mesoporous samples were characterized by FT-IR, XRD, and N2 adsorption BET methods. The incorporation of Ce3+ ions into the channel wall improves the stability of the mesoporous structure obviously. After ruthenium being loaded by the impregnating method, the Ru particle strongly interacts with the mesoporous mixed supports. Although a part of the particles are possible to block the support pores, the catalytic activity of ruthenium supported on the m-TiO2-CeO2 for methanol decomposition to carbon monoxide and hydrogen is significantly higher than that of ruthenium supported on m-TiO2. A synergistic effect between CeO2 and TiO2 was observed for promoting the catalytic properties of Ru.
文摘Spinel lithium manganese oxides doped with rare earth elements in forms of LiM 0.02 Mn 1.98 O 4 (M=La, Pr and Sm) were prepared and their electrochemical properties for lithium ion intercalation reaction were investigated. The materials were prepared by solid state reaction using electrolytic MnO 2, Li 2CO 3 with Pr 2O 3, Sm 2O 3 or La(NO 3) 3·H 2O. From the voltammetry test it was found that the reversibility of lithium intercalation reaction could be improved by doping with Sm or Pr into spinel lithium manganese oxides. Although the first discharge capacity was decreased by about 10% for LiPr 0.02 Mn 1.98 O 4 and LiSm 0.02 Mn 1.98 O 4 compounds compared with undoped LiMn 2O 4, but their cycling properties were improved, obviously.
