The Electrocatalytic Performance of Rare Earth Ion Doped Co_(0.2)Ni_(0.8)-MOF-74 Catalyst for Nitrogen Reduction

We took Co_(0.2)Ni_(0.8)-MOF-74 with bimetallic synergistic effect as the basic material,and selected rare earth ions Ho,Gd,and Er with ion radii close to Co and Ni as the research objects for doping.The influence of rare earth ion doping amount and doping type on the eNRR performance of the catalyst was explored.The experimental results show that the ammonia yield rate and Faraday efficiency doped with Co_(0.2)Ni_(0.8)-MOF-0.5Ho are the highest,reaching 1.28×10^(-10)mol·s^(-1)·cm^(-2)/39.8%,which is higher than the1.12×10^(-10)mol·s^(-1)·cm^(-2)/32.2%of Co_(0.2)Ni_(0.8)-MOF-74,and is about 14.3%/23.7%higher than that without doping,respectively.And the stability of Co_(0.2)Ni_(0.8)-MOF-0.5 Ho is good(after 80 hours of continuous testing,the current density did not significantly decrease).This is mainly due to doping,which gives Co_(0.2)Ni_(0.8)-MOF-74 a larger specific surface area and catalytic active sites.The catalyst doped at the same time has more metal cation centers,which increases the electron density of the metal centers and enhances the corresponding eNRR performance.

Magnetic Behavior of Some Rare-Earth Transition-Metal Perovskite Oxide Systems

Magnetic properties were investigated for the rare-earth 3d-transition metal oxides with the perovskite structure. Intriguing magnetic phenomena were reviewed for a few systems:magnetization peak effect in the titanates, magnetization reversal in the chromites and metallic ferromagnetism in the cobaltites. The results suggest an important role of the rare-earth ions for the magnetic properties of such complex oxides.

Rare Earth Elements-Doped LiCoO_2 Cathode Material for Lithium-Ion Batteries

Some compounds of LiCo 1- x RE x O 2 (RE=rare earth elements and x =0.01～0.03) were prepared by doping rare earth elements to LiCoO 2 via solid state synthesis. The microstructure characteristics of the LiCo 1- x RE x O 2 were investigated by XRD. It was found that the lattice parameters c are increased and the lattice volumes are enlarged compared to that of LiCoO 2. Moreover, the performance of LiCo 1- x RE x O 2 as the cathode material in lithium ion battery is improved, especially LiCo 1- x Y x O 2 and LiCo 1- x La x O 2. The initial charge/discharge capacities of LiCo 0.99 Y 0.01 O 2 and LiCo 0.99 La 0.01 O 2 are 174/154 (mAh·g -1 ) and 159/149 (mAh·g -1 ) respectively, while those for LiCoO 2 working in the same way are only 139/131 (mAh·g -1 ).

Synthesis and Structures of A Series of Novel Rare Earth Transition Metal Sulfates

Seven new rare earth transition metal sulfates were synthesized by hydrothermal reactions under conditions slightly above the critical point of water. Their crystal structures were determined from single crystal X-ray data. The compositions of the new compounds can be represented by two general formulae ： REM （OH） 3 （SO4） and RE2M （OH） 3 （SO4） 2F （H2O） with RE = Gd, Tb, Dy ; M = Ni, Cu. Three different crystal structure types were found for the formula REM （OH） 3 （SO4）. The structures of the new compounds all feature infinite chains of REOn coordination polyhedra, which are connected to chains of CuO6 or NiO6 octabedra. The limited size range of the rare earth cations observed in these compounds is most likely because of interactions between the octabedral chains and the chains of REOn polyhedra. The new compounds are closely related to the known yttrium transition metal sulfates.

Influence of rare-earth metal doping on the catalytic performance of CuO-CeO_2 for the preferential oxidation of CO in excess hydrogen

Doping of different rare-earth metals （Pr, Nd, Y and La） had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation （PROX） of CO in excess hydrogen. As for Pr, the doping enhanced the catalytic activity of CuO-CeO2 for PROX. For example, the CO conversion over the above catalyst for PROX was higher than 99% at 120 °C. Especially, the doping of Pr widened the temperature window by 20 °C over CuO-CeO2 with 99% CO conversion. For Nd, Y, and La, the doping depressed the catalytic activity of CuO-CeO2 for PROX. However, the doping of transition metals markedly improved the selectivity of CuO-CeO2 for PROX.

Electron Donating Property and Catalytic Activity ofPerovskite-type Mixed Oxides (ABO_3) Consisting of Rare Earth and 3d Transition Metals

The catalytic activity of Perovskite-type mixed oxides (LaCoO3, PrCoO3 and SmCoO3) for the reduction of cyclohexanone to cyclohexanol with 2-propanol (Meerwein-PonndorfVerley reduction) has been studied. The data have been correlated with the surface electron donor properties of these mixed oxides

Infrared Polarizabilities of 3d-Transition and Rare-Earth Metals

A transition or rare-earth metal is modeled as the atom immersed in a jellium at intermediate electron gas densities specified by? rs=4.0. The ground states of the spherical jellium atom are constructed based on the Hohenberg-Kohn-Sham density-functional formalism with the inclusion of electron-electron self-interaction corrections of Perdew and Zunger. Static and dynamic polarizabilities of the jellium atom are deduced using time-dependent linear response theory in a local density approximation as formulated by Stott and Zaremba. The calculation is extended to include the intervening elements In, Xe, Cs, and Ba. The calculation demonstrates how the Lindhard dielectric function can be modified to apply to non-simple metals treated in the jellium model.

Kinetics of Glass Transition and Crystallization in Carbon Nanotube Reinforced Mg-Cu-Gd Bulk Metallic Glass

Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter （DSC） was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.

Influence of Doping Rare Earth on Performance of Lithium Manganese Oxide Spinels as Cathode Materials for Lithium-Ion Batteries

Some rare earth doping spinel LiMn_(2-x)RE_xO_4 (RE=La, Ce, Nd) cathode materials for lithium ion batteries were synthesized by the solid-state reaction method. The structure characteristics of these produced samples were investigated by XRD, SEM, and particle size distribution analysis. According to the microstructure and charge-discharge testing, the effect of doping rare earth on stabilizing the spinel structure was analyzed. Through a series of doping experiments, it is shown that when the doping content x within the range of 0.01～0.02 the cycle performance of the materials is greatly improved. The discharge capacity of the sample LiMn_(1.98)La_(0.02)O_4, LiMn_(1.98)Ce_(0.02)O_4 and LiMn_(1.98)Nd_(0.02)O_4 remain 119.1, 114.2 and 117.5 mAh·g^(-1) after 50 cycles.

Experimental and numerical investigation of mid-infrared laser in Pr^(3+)-doped chalcogenide fiber

We report on a chalcogenide glass fiber doped with Pr^(3+) that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm–5.5 μm fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89-μm wavelength, with a pump power of 5 W, excitation wavelength at 2.04 μm, Pr^(3+) ion concentration at 4.22 × 10^(25) ions/m^3,fiber length at 0.94 m, and fiber background loss at 3 dB/m.

Specific mode output from multimode fiber oscillators by designing rare earth doping profiles

Based on rate equations, a theoretical model of a fiber oscillator with a multimode gain fiber was built. We studied the effect of the rare earth doping profile in the core on the output characteristics of the multimode fiber oscillator. The results indicated that a pure fundamental mode can be obtained by partly doping the core of the large mode area （LMA） ytterbium doped fiber （YDF） in the fiber laser. Furthermore, a sole specific high-order mode can also be implemented by tailoring the rare earth doping profile according to the simulations. The mode coupling effect was also taken into account in the model. In spite of the mode coupling effect, the specific mode was able to dominate in the output of the fiber laser by utilizing the designed LMA YDF.

Transport Properties of Rare Earth Manganese Oxide La_(0.67)Ca_(0.33)Mn_(1-x)Fe_xO_3

The transport properties were studied for rare earth manganese oxide La_(0.67)Ca_(0.33)Mn_(1-x)Fe_xO_3 (x=0～0.3) systems. It is found that with increasing Fe^(3+)-doping content x, the resistance increases and the insulator-metal transition temperature (T_(IM)) shifts to lower temperature. If the doping content is small, the transport properties manifest metallic characteristics in the temperature range of T<T_(IM), while they will obey a thermal activation model in the temperature range of T>T_(IM). Such a behavior may be attributed to the Fe^(3+)-doping and possible Mn ions scattering to electrons. The Fe^(3+) doping may lead to the formation of Fe^(3+)-O^(2-)-Mn^(4+) channels, which could terminate the double exchange Mn^(3+)-O^(2-)-Mn^(4+) channels. The antiferromagnetic clusters of Fe ions may induce the Mn ions to scetter to the electrons.

Synthesis and Characterization of Titania and Rare Earth Doped Titania Nanoparticles by Sol-gel Process

Titania sol has been prepared by the sol-gel process with Ti（OC4H9）4, as precursor. TiO2 gel was obtained through hydrolysis and condensation process. Rare earth such as La2O3, CeO2 and Gd2O3 were introduced into the nanostructure TiO2. After TiO2 and rare earth doped TiO2 powders were calcined at 400℃, 500℃, 600℃, 700℃ and 800℃ respectively, the characteristic analyses of the TiO2 samples were studied by UV-VIS, XRD and TEM etc. It was found that there are some stringer absorption peaks at 200 - 325 nm. The rare earth doping can increase the phase transition temperature convertin8 anatase phase into rutile phase, can decrease the grain size of TiO2particles and can improve the ann-UV capacity of the coating fabrics.

Using Atomic Microstates and Atomic Number Parity in Support of Lutetium and Lawrencium Classification as Transition Metals

Unlike other groups of elements, Group 3 constituency remains unsettled. This article argues that ground level microstates and atomic number parity suggest Sc-Y-Lu-Lr Group 3 membership.

Spontaneous Magnetic Transitions and Corresponding Magnetoelastic Properties of Intermetallic Compounds RMn_2Ge_2(R=Gd, Tb and Dy)

The spontaneous magnetic transitions and corresponding magnetoelastic properties of intermetallic compounds RMn2Ge2（R=Gd, Tb and Dy） were investigated by using the X-ray diffraction method and magnetic measurement. The results showed that the compounds experience two magnetic transitions, namely the second-order paramagnetic to antiferromagnetic transition at temperature TN（TN=368, 423 and 443 K for Gd Mn2 Ge2, Tb Mn2 Ge2 and Dy Mn2 Ge2, respectively） and the first-order antiferromagnetic-ferrimagnetic transition at temperature Tt（Tt=96, 80 and 40 K for Gd Mn2 Ge2, Tb Mn2 Ge2 and Dy Mn2 Ge2, respectively） as the temperature decreases. The temperature dependence of the lattice constant a（T） displays a negative magnetoelastic anomaly at the second-order transition point TN and, at the first-order transition Tt, a increases abruptly for Gd Mn2 Ge2 and Tb Mn2 Ge2, Da/a about 10^（-3）. Nevertheless, the lattice constant c almost does not change at these transition points indicating that such magnetoelastic anomalies are mainly contributed by the Mn-sublattice. The transitions of the magnetoelastic properties are also evidenced on the temperature dependence of magnetic susceptibility χ. The first-order transition behavior at Tt is explained by the Kittel mode of exchange inversion.

Solidification Behavior of Laser Melting Layer of Nd_(15)Fe_(77)B_8 Sintered Magnets and Its Microstructures Evolution

To research the solidification behavior and microstructures of a laser remelting/solidification layer on anisotropic Nd_(15)Fe_(77)B_(8 )sintered magnets with their magnetization direction parallel to X, Y, Z-axis respectively, their surfaces (parallel to XOY plane) were scanned by 5 kW Roffin-Sinar 850 type of CO_(2) laser along Y axis. The rapid solidification of the molten alloy in the layer results in three distinct zones. The transition zone close to the unmolten portion of a magnet (substrate), consists of the columnar Nd_(2)Fe_(14)B phase (matrix), the 10.0%~15.1% dendrite primary iron phase dispersing in the matrix, and the Nd-rich phase along Nd_(2)Fe_(14)B grain boundaries. The columnar crystal zone in the middle of the layer consists of the long columnar Nd_(2)Fe_(14)B grains and their grain boundary Nd-rich phase. And the dendrite crystal zone near the free surface of the layer consists of dendrite Nd_(2)Fe_(14)B grains and their grain boundary Nd-rich phase. When the laser scanning velocity is lower, the growing direction of the microstructures in the layer tends to the laser scanning direction step by step. When the velocity is not lower than 25 mm·s^(-1), the laser remelting/solidification layer thins and the columnar crystal zone comprises almost the whole layer. Under this condition, on the substrate with its magnetization direction along X or Y-axis respectively, the columnar Nd_(2)Fe_(14)B grains in the layer grow in the direction of Z-axis (that is their long-axis along Z-axis), their alignment of the easy magnetization axis [001] is parallel to the magnetization direction of the substrate correspondingly; but on the substrate with its magnetization direction along Z-axis, the columnar Nd_(2)Fe_(14)B grains in the transition zone grow at an angle of 30°~50° between Z-axis and their long-axis. And the columnar Nd_(2)Fe_(14)B grains in the columnar crystal zone gradually tend to the Z-axis,and their easy magnetization axis [001] arrange in the range of 0°~360° of the plane perpendicular to their long-axis.

Upconversion Luminescence of Ce^(3+) Doped BK7 Glass by Femtosecond Laser Irradiation

Near-infrared to visible upconversion luminescence was observed in a multicomponent silicate （BK7） glass containing Ce^3 ＋ ions under focused infrared femtosecond laser irradiation. The emission spectra show that the upconversion luminescence comes from the 4f-5d transition of the Ce^3 ＋ ions. The relationship between the intensity of the Ce^3 ＋ emission and the pump power reveals that a three-photon absorption predominates in the conversion process from the near-infrared into the blue luminescence. The analysis of the upconversion mechanism suggests that the upconversion luminescence may come from a three-photon simultaneous absorption that leads to a population of the 5d level in which the characteristic luminescence occurs.

Magnetic Properties and Colossal Magnetoresistance of La_(0.7)Sr_(0.3)MnO_3 Materials Doped with Fe

La 0.7 Sr 0.3 Fe x Mn 1- x O 3 compounds (0 05≤ x ≤0 18) were prepared by the sol gel technique. The effects of Fe doping on the magnetic properties, conductivity and magnetoresistance for La 0.7 Sr 0.3 MnO 3 was investigated. Experimental results indicate that the Fe doping leads to a decrease in the ferromagnetic ordering temperature, an increase in the resistance and magnetoresistance effect. For samples of x =0 05 and x =0 08 two peaks are observed in their ρ T curve. Magnetic resistivity ( MR ) of La 0.7 Sr 0.3 Fe 0.08 Mn 0.92 O 3 sample is capable of reaching 18%(8×10 5A·m -1 , 293 K). At x ≥0 1, metal insulator (M I) transition temperature ( T p) is lower than ferromagnetic Curie temperature ( T C) by about 50～80 K.

Neodymium-doped Yttrium Aluminum Garnet Transparent Laser Ceramics Prepared by Co-precipitation Method

Transparent polycrystaUine neodymiumdoped yttrium aluminum garnet ceramics （Nd：YAG） with better chemical stability, excellent optical and high temperature mechanical property is becoming a new laser host material. The Nd：YAG precursor powders with loosely dispersed, slightly agglomerated and YAG cubic crystal phase were synthesized at 1100 ℃ by the co-precipitation method combined with the reverse strike,

Magnetocrystalline anisotropy and spin reorientation transition of DyMn_6Sn_6 compound

The spin-reorientation transition of intermetallic compound DyMn6Sn6 was investigated by applying the molecular field theory. The temperature dependence of easy magnetization direction of compound and the magnetic moment directions of Dy and Mn ions were theoretically calculated and they have good agreement with the experimental data. In the framework of single ion model, the temperature dependence of magnetocrystalline anisotropic constants K1R and K2R of Dy ion were also calculated. The results show that the fourth-order crystal field parameter, B 40, and the corresponding second-order magnetocrystalline anisotropic constant, K2R, of Dy ion must be taken into account in order to explain the spin-reorientation transition satisfactorily. The competition between K2R and K1R plays a key role in the spin-reorientation transition of DyMn6Sn6.