Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal s...Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into the clad powder mixture to investigate the effects of RE2O3 on the in-situ carbide particle formation in Fe-based composite coatings.Through the analysis using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS) and transmission electron microscope(TEM),it was revealed that:(1) Adding RE2O3 to the Fe-based powder mixture could effectively reduce cracks and porosities and the coating surface was more smooth;(2) The solubility of carbon could be improved which increased the eutectic degree of the microstructure;(3) RE2O3 could promote the nucleation of the reinforcement particles as heterogeneous nuclei.During the precipitating process of the carbide particles,some RE2O3 powders still existed while others react with carbon in the melt to form rare earth carbides.Both of them acted as heterogeneous nuclei for the formation of particles.展开更多
Isothermal and cyclic oxidation behaviors of Co 40Cr alloy at 1000 ℃ in air were studied. Scanning electron microscopy (SEM) was used to examine the oxide scale formed on the surface of the alloy. By comparing the ox...Isothermal and cyclic oxidation behaviors of Co 40Cr alloy at 1000 ℃ in air were studied. Scanning electron microscopy (SEM) was used to examine the oxide scale formed on the surface of the alloy. By comparing the oxidation behaviors of Co 40Cr alloy and its 3×10 16 and 3×10 17 Y +/cm 2 implanted specimens, it was found that the resistant to oxidation property of Co 40Cr was greatly improved due to the implantation of yttrium. Acoustic emission was used to study the distribution of defects at the interface between the scale and alloy. Raman spectrum was also used to study the stress status in chromic scale formed on the surface of Co 40Cr with and without yttrium. The main reason for the improvement of resistant to oxidation property of Y doped Co 40Cr probably is that yttrium can segregate to Cr 2O 3 grain boundaries and change the scale′s growing mechanism and mechanical property. Most importantly, Y implantation decreases the size and number of interfacial defects and the residual stress in the scale, and remarkably enhances the adhesion of chromia scale with Co 40Cr substrate.展开更多
The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive...The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth oxides or CaCO3.展开更多
The granule shape and crystal structure of the the ceria-based rare earth oxide which were roasted at 600～1050 ℃ for 2～6 h and then cooled in furnace, cooled out of furnace or cooled in water were studied by means ...The granule shape and crystal structure of the the ceria-based rare earth oxide which were roasted at 600～1050 ℃ for 2～6 h and then cooled in furnace, cooled out of furnace or cooled in water were studied by means of XRD and SEM. The results revealed that the rich cerium rare earth carbonate could be changed into the rare earth oxide which was a kind of sandwich made of globose granule whose diameter was between 0.5～3.0 μm after being roasted in 900 ℃ for 2 h. This kind of crystal lattice in rare earth oxide belonged to face-centered cubic lattice and its space between crystal surface {111} and {200} (viz. L111 and L200) would enlarge as the roasting temperature increasing. With increasing roasting temperature, L111 would rise straightly upward, and L200 would rise straightly upward when roasting time was 2～4 h but changed little when roasting time was 4～6 h. The glass-polishing experiments found that the polishing ability of the ceria-based rare earth oxide was the best as L111 was 43～53 nm and the L200 was 43～56 nm.展开更多
This article describes a new method for the simultaneous determination of trace rare earth elements (REEs) and non rare earth elements (NREEs) in high purity terbium oxide by ICP-AES after HPLC separation using P507 r...This article describes a new method for the simultaneous determination of trace rare earth elements (REEs) and non rare earth elements (NREEs) in high purity terbium oxide by ICP-AES after HPLC separation using P507 resin. The chromatographic separation of the analytes from the matrix using dilute nitric acid as mobile phase was studied. The experimental results showed that a favorable separation of trace metals (Cu and Gd) from the matrix (Tb) can easily be achieved by elution with dilute nitric acid within 25 min. The proposed method was applied to the determination of trace metals (Ca, Cu, Mg, Mn, Ni, Si, La, Ce, Pr, Nd, Sm, Eu and Gd) in high purity terbium oxide. The detection limits (DLs) for the analytes ranged from 0.4-4.0 μg\5g -1, and the recoveries are from 78%-105%.展开更多
Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached...Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached 96% at 60 oC for electrodes with 1 at.% flaky rare earth oxides.The high rate discharge performance for electrodes with flaky rare earth oxides were improved significantly,for example,discharge efficiency at 5C improved from 50% to 70%.The results showed that the end charging potential of the nickel electrodes with flaky rare earth oxides were higher than that without rare earth oxide additives,but lower than that with normal rare earth oxide additives.The CVs experimental results suggested that flaky rare earth oxides increased the oxygen evolution potential and improved the reversibility of nickel electrodes.展开更多
A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope (TEM) images indicate that th...A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope (TEM) images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared (FTIR) spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.展开更多
With the rapid development of society and economy, the excessive consumption of fossil energy has led to the global energy and environment crisis. In order to explore the sustainable development of new energy, researc...With the rapid development of society and economy, the excessive consumption of fossil energy has led to the global energy and environment crisis. In order to explore the sustainable development of new energy, research based on electrocatalysis has attracted extensive attention in the academic circle. The main challenge in this field is to develop nano-catalysts with excellent electrocatalytic activity and selectivity for target products. The state of the active site in catalyst plays a decisive role in the activity and selectivity of the reaction. In order to design efficient and excellent catalysts, it is an effective means to adjust the electronic structure of catalysts. Electronic effects are also called ligand effects. By alloying with rare earth(RE) elements, electrons can be redistributed between RE elements and transition metal elements, achieving accurate design of the electronic structure of the active site in the alloy. Because of the unique electronic structure of RE, it has been paid attention in the field of catalysis. The outermost shell structure of RE elements is basically the same as that of the lower shell, except that the number of electrons in the 4f orbital is different, but the energy level is similar, so their properties are very similar. When RE elements form compounds, both the f electrons in the outermost shell and the d electrons in the lower outer shell can participate in bonding. In addition, part of the 4f electrons in the third outer shell can also participate in bonding.In order to improve the performance of metal catalysts, alloying provides an effective method to design advanced functional materials. RE alloys can integrate the unique electronic structure and catalytic behavior of RE elements into metal materials, which not only provides an opportunity to adjust the electronic structure and catalytic activity of the active component, but also enhances the structural stability of the alloy and is expected to significantly improve the catalytic performance of the catalyst. From the perspective of electronic and catalytic activity, RE elements have unique electronic configuration and lanthanide shrinkage effect. Alloying with RE elements will make the alloy have more abundant electronic structure, activity, and spatial arrangement, effectively adjusting the reaction kinetics of the electrochemical process of the catalyst. In this paper, the composition,structure, synthesis of RE alloys and their applications in the field of electrocatalysis are summarized, including the hydrogen evolution reaction, the oxygen evolution reaction, the oxygen reduction reaction, the methanol oxidation reaction, the ethanol oxidation reaction, and other catalytic reactions. At the same time, the present challenges of RE alloy electrocatalytic materials are summarized and their future development direction is pointed out. In the field of electrocatalysis, the cost of catalyst is too high and the stability is not strong. Therefore, the testing process should be related to the actual application, and the test method should be standardized, so as to carry forward the field of electrocatalysis.展开更多
A novel inductively coupled plasma mass spectrometry method for direct determination of trace rare earth impurities in high purity europium oxide （Eu2O3） was developed. The spectral interference,matrix effect,instru...A novel inductively coupled plasma mass spectrometry method for direct determination of trace rare earth impurities in high purity europium oxide （Eu2O3） was developed. The spectral interference,matrix effect,instrument parameters fluctuation were investigated and the optimized experimental conditions were established. Under the selected conditions,the detection limits of the method are 3～7 ng·L （-1）,the RSD is varied between 2.1%～8.4%,and the percentage recovery is ranged from 90% to 113% for the analytes. The solid detection limit for gross amount of 13 rare earth impurities is 0.19 μg·g （-1） when the matrix （Eu） concentration of 0.1 mg·ml （-1） was chosen. Compared with the reported methods in the literature,this method has several attractive features: simple,small sample amount required,no internal standard and matrix matching requirements.展开更多
A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. T...A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.展开更多
The performance of LiNi/γ-Al2O3 catalysts modified by rare earth metal oxide(La2O3 or CeO2 ) packed on BCFNO membrane reactor was discussed for the partial oxidation of methane(POM) in coke oven gas(COG) at 875 C. Th...The performance of LiNi/γ-Al2O3 catalysts modified by rare earth metal oxide(La2O3 or CeO2 ) packed on BCFNO membrane reactor was discussed for the partial oxidation of methane(POM) in coke oven gas(COG) at 875 C. The NiO/γ-Al2O3 catalysts with different amounts of La2O3 and CeO2 were prepared with the same preparation method and under the same condition in order to compare the reaction performance(oxygen permeation,CH 4 conversion,H 2 and CO selectivity) on the membrane reactor. The results show that the oxygen permeation flux increased significantly with LiNiREO x /γ-Al2O3(RE = La or Ce) catalysts by adding the element of rare earth especially the Ce during the POM in COG. Such as,the Li15wt%CeO2 9wt%NiO/γ-Al2O3 catalyst with an oxygen permeation flux of 24.71 ml cm 2 min 1 and a high CH 4 conversion was obtained in 875 C. The resulted high oxygen permeation flux may be due to the added Ce that inhibited the strong interaction between Ni and Al2O3 to form the NiAl2O4 phase. In addition,the introduction of Ce leads up to an important property of storing and releasing oxygen.展开更多
Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were charact...Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were characterized by XRD and TEM, respectively. Gas sensing properties were tested at static state. The results show that homogeneous indium oxide nanopowder with main grain size of 20 nm can be obtained from microemulsion after sintered at 600 ℃ for 1 h. Pure indium oxide gas sensor has higher sensitivity to gasoline than that to ethanol, HCHO, C6H6, NH3, C4H 10, but the selectivity is not as well as sensitivity. The sensors response （Ra/Rg） is greatly promoted by doping Y2O3 and Nd2O3 doping. The doped sample shows satisfying sensitivity and selectivity to gasoline at 3.0 V working voltage, and the sensor response for 5.0% Y2O3 doped sample is found to reach a maximum as large as 285.1 and the power consumption is only around 200 mW.展开更多
The modifying effect of rare earth (RE) oxide on inclusions in hardfacing metals of medium-high carbon steel was investigated by means of thermodynamics. The thermodynamic analysis for inclusion formation shows that R...The modifying effect of rare earth (RE) oxide on inclusions in hardfacing metals of medium-high carbon steel was investigated by means of thermodynamics. The thermodynamic analysis for inclusion formation shows that RE oxide can be reduced to RE element by carbon, then the RE element can react with oxygen and sulfur to form the RE oxide, RE sulfide and RE oxide-sulfide in hardfacing molten pool. The deoxidization and the desulphurization can be carried out and the liquid metal can be purified. In addition, RE oxide can also react with sulfur to form RE oxide-sulfide directly. Therefore, the harmful effect of sulfur can be decreased.展开更多
Diesel oxide catalysts and soot combustion catalysts were reported in this paper.The former was manufactured in mass last year, and enhanced performance is under development now.The later is screened out and further r...Diesel oxide catalysts and soot combustion catalysts were reported in this paper.The former was manufactured in mass last year, and enhanced performance is under development now.The later is screened out and further research is under way.The best soot combustion catalyst could ignite soot combustion even at 350 ℃, which is within the range of temperatures reached in diesel exhaust, and shows the catalytic combustion velocity nearly one time faster compared with non-catalytic combustion of soot, which is of benefit to rapid regeneration of diesel particulate filter, thus it might be an excellent practicable catalyst.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 A 0.67 Ln 0.33 Mn 0.33 Ti 0.67 O3 （A=Ca or Sr and Ln=rare earth） were found to have orthorhombic symmetry with the space group Pnma, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Ca 0.67 Ln 0.33 Mn 0.33 Ti 0.67 O3 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
Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3·2H2O with distilled ...Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3·2H2O with distilled water under ultrasonic wave agitation and centrifuging repeatedly, and the specific surface area tended to increase gradually with washing and centrifuging. The sample of centrifuged 7 h has more than 2 times highs specific surface area and more high photocatalytic activity . The mechanisms are also discussed.展开更多
The cracking morphology of the hardfacing specimens taken from steel 5CrNiMo was observed. Meanwhile, the residual stress fields were measured and simulated. Based on experiment mentioned above, the improved structure...The cracking morphology of the hardfacing specimens taken from steel 5CrNiMo was observed. Meanwhile, the residual stress fields were measured and simulated. Based on experiment mentioned above, the improved structure and modified inclusion in hardfacing metal with rare earth (RE) oxide were analyzed. The results show that, the hardfacing crack is initiated from the coarse dendritic crystal grain boundary, inclusions and coarse austenite grain boundary in the HAZ and propagated by the residual stress existing in the center of the hardfacing metal and HAZ. The primary columnar grain structure can be refined by adding RE oxide in the coating of the electrode. The inclusion in the hardfacing metal can be modified as well. Meanwhile, if the martensite transformation temperature is decreased, the largest value of the residual tensile stress in the dangerous region can be reduced.展开更多
文摘Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into the clad powder mixture to investigate the effects of RE2O3 on the in-situ carbide particle formation in Fe-based composite coatings.Through the analysis using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS) and transmission electron microscope(TEM),it was revealed that:(1) Adding RE2O3 to the Fe-based powder mixture could effectively reduce cracks and porosities and the coating surface was more smooth;(2) The solubility of carbon could be improved which increased the eutectic degree of the microstructure;(3) RE2O3 could promote the nucleation of the reinforcement particles as heterogeneous nuclei.During the precipitating process of the carbide particles,some RE2O3 powders still existed while others react with carbon in the melt to form rare earth carbides.Both of them acted as heterogeneous nuclei for the formation of particles.
文摘Isothermal and cyclic oxidation behaviors of Co 40Cr alloy at 1000 ℃ in air were studied. Scanning electron microscopy (SEM) was used to examine the oxide scale formed on the surface of the alloy. By comparing the oxidation behaviors of Co 40Cr alloy and its 3×10 16 and 3×10 17 Y +/cm 2 implanted specimens, it was found that the resistant to oxidation property of Co 40Cr was greatly improved due to the implantation of yttrium. Acoustic emission was used to study the distribution of defects at the interface between the scale and alloy. Raman spectrum was also used to study the stress status in chromic scale formed on the surface of Co 40Cr with and without yttrium. The main reason for the improvement of resistant to oxidation property of Y doped Co 40Cr probably is that yttrium can segregate to Cr 2O 3 grain boundaries and change the scale′s growing mechanism and mechanical property. Most importantly, Y implantation decreases the size and number of interfacial defects and the residual stress in the scale, and remarkably enhances the adhesion of chromia scale with Co 40Cr substrate.
基金the Natural Science Foundation of Jiangxi Province (No. 0650047)the Science and Technology Program of the Education Department of Jiangxi Province,China(No.GJJ08268).
文摘The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth oxides or CaCO3.
文摘The granule shape and crystal structure of the the ceria-based rare earth oxide which were roasted at 600～1050 ℃ for 2～6 h and then cooled in furnace, cooled out of furnace or cooled in water were studied by means of XRD and SEM. The results revealed that the rich cerium rare earth carbonate could be changed into the rare earth oxide which was a kind of sandwich made of globose granule whose diameter was between 0.5～3.0 μm after being roasted in 900 ℃ for 2 h. This kind of crystal lattice in rare earth oxide belonged to face-centered cubic lattice and its space between crystal surface {111} and {200} (viz. L111 and L200) would enlarge as the roasting temperature increasing. With increasing roasting temperature, L111 would rise straightly upward, and L200 would rise straightly upward when roasting time was 2～4 h but changed little when roasting time was 4～6 h. The glass-polishing experiments found that the polishing ability of the ceria-based rare earth oxide was the best as L111 was 43～53 nm and the L200 was 43～56 nm.
基金SupportedbytheNationalScienceFoundationofChina (No .2 0 0 0 70 10 10 8)andWuhanMunicipalScience&TechnologyCommission (No .995 0 0 40 80 )
文摘This article describes a new method for the simultaneous determination of trace rare earth elements (REEs) and non rare earth elements (NREEs) in high purity terbium oxide by ICP-AES after HPLC separation using P507 resin. The chromatographic separation of the analytes from the matrix using dilute nitric acid as mobile phase was studied. The experimental results showed that a favorable separation of trace metals (Cu and Gd) from the matrix (Tb) can easily be achieved by elution with dilute nitric acid within 25 min. The proposed method was applied to the determination of trace metals (Ca, Cu, Mg, Mn, Ni, Si, La, Ce, Pr, Nd, Sm, Eu and Gd) in high purity terbium oxide. The detection limits (DLs) for the analytes ranged from 0.4-4.0 μg\5g -1, and the recoveries are from 78%-105%.
基金supported by the 863 National Research and Development Project Foundation of China (2006AA11A151)
文摘Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached 96% at 60 oC for electrodes with 1 at.% flaky rare earth oxides.The high rate discharge performance for electrodes with flaky rare earth oxides were improved significantly,for example,discharge efficiency at 5C improved from 50% to 70%.The results showed that the end charging potential of the nickel electrodes with flaky rare earth oxides were higher than that without rare earth oxide additives,but lower than that with normal rare earth oxide additives.The CVs experimental results suggested that flaky rare earth oxides increased the oxygen evolution potential and improved the reversibility of nickel electrodes.
文摘A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope (TEM) images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared (FTIR) spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.
基金financial support from the National Key R&D Program of China (2022YFB3506200)the National Nature Science Foundation of China (22122113)。
文摘With the rapid development of society and economy, the excessive consumption of fossil energy has led to the global energy and environment crisis. In order to explore the sustainable development of new energy, research based on electrocatalysis has attracted extensive attention in the academic circle. The main challenge in this field is to develop nano-catalysts with excellent electrocatalytic activity and selectivity for target products. The state of the active site in catalyst plays a decisive role in the activity and selectivity of the reaction. In order to design efficient and excellent catalysts, it is an effective means to adjust the electronic structure of catalysts. Electronic effects are also called ligand effects. By alloying with rare earth(RE) elements, electrons can be redistributed between RE elements and transition metal elements, achieving accurate design of the electronic structure of the active site in the alloy. Because of the unique electronic structure of RE, it has been paid attention in the field of catalysis. The outermost shell structure of RE elements is basically the same as that of the lower shell, except that the number of electrons in the 4f orbital is different, but the energy level is similar, so their properties are very similar. When RE elements form compounds, both the f electrons in the outermost shell and the d electrons in the lower outer shell can participate in bonding. In addition, part of the 4f electrons in the third outer shell can also participate in bonding.In order to improve the performance of metal catalysts, alloying provides an effective method to design advanced functional materials. RE alloys can integrate the unique electronic structure and catalytic behavior of RE elements into metal materials, which not only provides an opportunity to adjust the electronic structure and catalytic activity of the active component, but also enhances the structural stability of the alloy and is expected to significantly improve the catalytic performance of the catalyst. From the perspective of electronic and catalytic activity, RE elements have unique electronic configuration and lanthanide shrinkage effect. Alloying with RE elements will make the alloy have more abundant electronic structure, activity, and spatial arrangement, effectively adjusting the reaction kinetics of the electrochemical process of the catalyst. In this paper, the composition,structure, synthesis of RE alloys and their applications in the field of electrocatalysis are summarized, including the hydrogen evolution reaction, the oxygen evolution reaction, the oxygen reduction reaction, the methanol oxidation reaction, the ethanol oxidation reaction, and other catalytic reactions. At the same time, the present challenges of RE alloy electrocatalytic materials are summarized and their future development direction is pointed out. In the field of electrocatalysis, the cost of catalyst is too high and the stability is not strong. Therefore, the testing process should be related to the actual application, and the test method should be standardized, so as to carry forward the field of electrocatalysis.
文摘A novel inductively coupled plasma mass spectrometry method for direct determination of trace rare earth impurities in high purity europium oxide （Eu2O3） was developed. The spectral interference,matrix effect,instrument parameters fluctuation were investigated and the optimized experimental conditions were established. Under the selected conditions,the detection limits of the method are 3～7 ng·L （-1）,the RSD is varied between 2.1%～8.4%,and the percentage recovery is ranged from 90% to 113% for the analytes. The solid detection limit for gross amount of 13 rare earth impurities is 0.19 μg·g （-1） when the matrix （Eu） concentration of 0.1 mg·ml （-1） was chosen. Compared with the reported methods in the literature,this method has several attractive features: simple,small sample amount required,no internal standard and matrix matching requirements.
基金Supported by the 985 Foundation of Central University for Nationalities（CUN985-3-3） the National Natural Science Foundation of China（90305011）
文摘A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.
基金supported by the National High Technology Research and Development Program of China (No. 2006AA11A189)Science and Technology Commission of Shanghai Municipality (No. 06DZ12212)+1 种基金National Engineering Research Center of Advanced Steel Technology (NERCAST) (No. 050209)the Innovation Fund for Graduate Studentof Shanghai University (SHUCX0910003)
文摘The performance of LiNi/γ-Al2O3 catalysts modified by rare earth metal oxide(La2O3 or CeO2 ) packed on BCFNO membrane reactor was discussed for the partial oxidation of methane(POM) in coke oven gas(COG) at 875 C. The NiO/γ-Al2O3 catalysts with different amounts of La2O3 and CeO2 were prepared with the same preparation method and under the same condition in order to compare the reaction performance(oxygen permeation,CH 4 conversion,H 2 and CO selectivity) on the membrane reactor. The results show that the oxygen permeation flux increased significantly with LiNiREO x /γ-Al2O3(RE = La or Ce) catalysts by adding the element of rare earth especially the Ce during the POM in COG. Such as,the Li15wt%CeO2 9wt%NiO/γ-Al2O3 catalyst with an oxygen permeation flux of 24.71 ml cm 2 min 1 and a high CH 4 conversion was obtained in 875 C. The resulted high oxygen permeation flux may be due to the added Ce that inhibited the strong interaction between Ni and Al2O3 to form the NiAl2O4 phase. In addition,the introduction of Ce leads up to an important property of storing and releasing oxygen.
文摘Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were characterized by XRD and TEM, respectively. Gas sensing properties were tested at static state. The results show that homogeneous indium oxide nanopowder with main grain size of 20 nm can be obtained from microemulsion after sintered at 600 ℃ for 1 h. Pure indium oxide gas sensor has higher sensitivity to gasoline than that to ethanol, HCHO, C6H6, NH3, C4H 10, but the selectivity is not as well as sensitivity. The sensors response （Ra/Rg） is greatly promoted by doping Y2O3 and Nd2O3 doping. The doped sample shows satisfying sensitivity and selectivity to gasoline at 3.0 V working voltage, and the sensor response for 5.0% Y2O3 doped sample is found to reach a maximum as large as 285.1 and the power consumption is only around 200 mW.
文摘The modifying effect of rare earth (RE) oxide on inclusions in hardfacing metals of medium-high carbon steel was investigated by means of thermodynamics. The thermodynamic analysis for inclusion formation shows that RE oxide can be reduced to RE element by carbon, then the RE element can react with oxygen and sulfur to form the RE oxide, RE sulfide and RE oxide-sulfide in hardfacing molten pool. The deoxidization and the desulphurization can be carried out and the liquid metal can be purified. In addition, RE oxide can also react with sulfur to form RE oxide-sulfide directly. Therefore, the harmful effect of sulfur can be decreased.
文摘Diesel oxide catalysts and soot combustion catalysts were reported in this paper.The former was manufactured in mass last year, and enhanced performance is under development now.The later is screened out and further research is under way.The best soot combustion catalyst could ignite soot combustion even at 350 ℃, which is within the range of temperatures reached in diesel exhaust, and shows the catalytic combustion velocity nearly one time faster compared with non-catalytic combustion of soot, which is of benefit to rapid regeneration of diesel particulate filter, thus it might be an excellent practicable catalyst.
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 A 0.67 Ln 0.33 Mn 0.33 Ti 0.67 O3 （A=Ca or Sr and Ln=rare earth） were found to have orthorhombic symmetry with the space group Pnma, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Ca 0.67 Ln 0.33 Mn 0.33 Ti 0.67 O3 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Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3·2H2O with distilled water under ultrasonic wave agitation and centrifuging repeatedly, and the specific surface area tended to increase gradually with washing and centrifuging. The sample of centrifuged 7 h has more than 2 times highs specific surface area and more high photocatalytic activity . The mechanisms are also discussed.
基金Project supported by Key Project of Science and Technology of Hebei Province (04212201D) and Research Foundationfor theReturned Overseas Chinese Scholars of State Education Ministry
文摘The cracking morphology of the hardfacing specimens taken from steel 5CrNiMo was observed. Meanwhile, the residual stress fields were measured and simulated. Based on experiment mentioned above, the improved structure and modified inclusion in hardfacing metal with rare earth (RE) oxide were analyzed. The results show that, the hardfacing crack is initiated from the coarse dendritic crystal grain boundary, inclusions and coarse austenite grain boundary in the HAZ and propagated by the residual stress existing in the center of the hardfacing metal and HAZ. The primary columnar grain structure can be refined by adding RE oxide in the coating of the electrode. The inclusion in the hardfacing metal can be modified as well. Meanwhile, if the martensite transformation temperature is decreased, the largest value of the residual tensile stress in the dangerous region can be reduced.
