Structure and high-temperature electrochemical properties of La_（0.60）Nd_（0.15）Mg_（0.25）Ni_（3.3）Si_（0.10） hydrogen storage alloys

The structure and high-temperature electrochemical properties of the as-cast and annealed (940 °C, 8 h) La0.60Nd0.15Mg0.25Ni3.3Si0.10 hydrogen storage alloys were investigated. The X-ray diffraction revealed that the multiphase structure of the as-cast alloy with LaNi5 phase as the main phase was converted into a double-phase structure with La2Ni7 phase as the main phase after annealing. The surface morphology studied by scanning electronic microscope (SEM) showed that the annealed alloy had a much higher anti-corrosion ability than the as-cast alloy. Both alloys presented excellent activation characteristics at all test temperatures. The maximum discharge capacity of the as-cast alloy decreased when the test temperature increased, while the temperature almost had no effect on the annealed alloy. As the test temperature increased, the cyclic stability and charge retention of both alloys decreased, and these properties were improved significantly by annealing.     

Investigation of the crystal structure and magnetic properties of Nd_（3-x）GdxCo_（11）B_4 borides

Polycrystalline samples of pseudo-ternary intermetallic Nd3-xGdxCo11B4 (x=0,1,2,3) borides prepared by standard arc-melting were characterized by X-ray powder diffraction (XRPD),magnetization and differential scanning calorimetry (DSC) measurements. The X-ray diffraction patterns indicated the hexagonal Ce3Co11B4-type structure with P6/mmm space group for each composition. The substitution of Gd for Nd led to a decrease of the unit-cell parameters a and the unit-cell volume V,while the unit-cell parameter c increased linearly. Magnetic measurements indicated that all samples were ordered magnetically below the Curie temperature. The Curie temperatures increased as Nd was substituted by Gd. The saturation magnetization at 4 K decreased upon the Gd substitution up to x=1,and then increased.     

Magnetocaloric effect and magnetic properties of La_（0.9）Ce_（0.1）（Fe_（0.99）Mn_（0.01））_（11.6）Si_（1.4）H_（1.6） compound

Magnetocaloric effect and magnetic properties of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 and its hydride La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 were investigated. The Curie temperature of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 was increased by hydrogen absorption. XRD patterns showed that the structure of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 remained NaZn13-type. The Curie temperature (TC) of the sample was increased from 174 K to 331 K. The homogeneity of the hydrogen absorption for La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 was proven very well by the random measurement of DSC. The magnetic entropy △SM of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 had peak at 326 K. The peak value of-△SM-was 12.3 and 7.8 J/(kg.K) under magnetic field change of 0-2 T and 0-1 T,respectively,which was comparable with Gd5Si2Ge2. The negative slope and inflection point of the Arrott curve indicated that the first-order magnetic transition of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 was reserved after hydrogen absorption.     

Effects of magnetic annealing on crystallization and magnetic properties of Nd2Fe14B/α-Fe nanocomposite magnets

Crystallization and magnetic properties of Nd2Fe14B/α-Fe nanocomposite magnets have been investigated by annealing the as-spun ribbons with magnetic field.The crystallization process was accelerated by field annealing.The hysteresis loop became to be fat by magnetic annealing at 645 oC for 4 min,which was 690 oC for ribbons annealing without magnetic field.The relative content of α-Fe phase was increased from the results of XRD.The strength of the magnetic field had no obvious influence on the remanence and coercivity,but modified the squareness of hysteresis loop.     

Physico-chemical properties of 3-methoxy-2-nitrobenzoates of some rare earth elements（Ⅲ）

The complexes of 3-methoxy-2-nitrobenzoates of Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Er(III) and Tm(III) with the formula: Ln(C8H6NO5)3·2H2O, where Ln=lanthanides(III), were synthesized and characterized by elemental analysis, Forier transform irtrared (FTIR) spectroscopy, magnetic and thermogravimetric studies and also by X-ray diffraction (XRD) measurements. The complexes had col- ours typical for Ln(III) ions. The carboxylate groups bound as bidentate chelating. On heating to 1173 K in air they decomposed in the same way, at first, dehydrated in one step to anhydrous salts, and then decomposed to the oxides of respective metals with intermediate formation of the oxycarbonates. The enthalpy values of the dehydration process changed from 133.72 to 44.50 kJ/mol. Their solubility in water at 293 K was of the order of 10-4 mol/dm3. The magnetic moments of analysed complexes were determined by Gouy’s method in the range of 76-303 K.     

Preparation and characterization of La0.9Sr0.1Ga0.8Mg0.2O3–δ thin film deposited by radio frequency magnetic sputtering

La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte materials were synthesized by the solid state reaction method.The conductivity of LSGM materials was detected by four probe method,and it was 0.08 S/cm at 850 ℃.Dense and uniform films of LSGM materials were deposited by the magnetic sputtering on substrates of Si and La0.7Sr0.3Cr0.5Mn0.5O3-δ (LSCM).The experimental results showed that the deposition rates dropped and the average grain sizes of the films enlarged with increase in the substrate temperatures.In the sputtering process,the LSGM film was deposited with preferred growth direction.After annealing,the preferred growth direction disappeared and the film surface became smoother and denser.Through observing the deposition process,deposition mechanism was proposed,which was consistent with a model of island growth.     

Effects of manganese doping on magnetocaloric effect in Ge-rich Gd_5Ge_（2.05）Si_（1.95） alloy

The structure, magnetic and magnetocaloric properties of the Ge-rich Gd5Ge2.05-xSi1.95-xMn2x (x=0.01 and 0.03) alloys were investigated by scanning electron microscopy, X-ray powder diffraction, differential scanning calorimeter (DSC) and magnetization measurements. The results of energy dispersive X-ray analysis (EDX) and X-ray diffraction analyses showed that the composition and crystal structure of the alloys were desired. DSC measurements were performed to determine the transformation temperatures for each alloy. Both alloys exhibited the first order phase transition around room temperature. The alloys showed an anti-ferromagnetic transition around 60 K. The isothermal magnetic entropy changes of the alloys were determined from the isothermal magnetization measurements by using the Maxwell relation. The maximum values of isothermal magnetic entropy change of the Gd5Ge2.05-xSi1.95-xMn2x alloy with x=0.01 was found to be -12.1 and -19.8 J/(kg·K) using Maxwell equation around 268 K in applied fields of 2 and 5 T, respectively.     

Effect of a magnetic field on magnetic entropy change in LaFe_（11.7）Si_（1.3） compound

The magnetocaloric effect of LaFe11.7Si1.3 compound was investigated under an external magnetic field up to 9 T.The magnetization changed drastically at the Curie temperature TC under different fields and TC increased with the applied fields.The magnetic entropy change |?SM| vs temperature peak consisted of a spike and a plateau.The spike was a spurious result,while the plateau part resulted from the field-induced itinerant-electron metamagnetic(IEM) transition above TC,which went up with magnetic fields increasing.The width of the magnetic entropy change increased with magnetic fields at a rate of dL?S /dT~4 K/T.     

Influence of iron on phase and magnetic property of the LaFe_（11.6）Si_（1.4） compound

The phase relation, microstructure, Curie temperatures, hysteresis, and magnetocaloric effects of LaFex*11.6Si1.4 (x=0.96, 0.98, 1.0, and 1.02) compounds prepared by arc-melting and then annealed at 1423 K (1.5 h)+1523 K (4.5 h) were investigated. The main phase was NaZn13-type phase, the impurity phases included a small amount of α-Fe and LaFeSi phase in four samples. The crystal cell parameters of 1:13 phase increased from 1.1433(5) to 1.1454(4) nm with x increasing from 0.96 to 1.02, respectively. All samples kept the typical first-order magnetic transition. The increase of Fe strengthened IEM behavior, and led to the remarkable enhancement of MCE effect and negative slopes in Arrott plots around TC. The maximum ΔSM (T, H) under a low magnetic field (0-2 T) was 15.3, 16.8, 17.9, and 24.7 J/kg K with increasing of Fe content from x=0.96 to 1.02, respectively.     

A study on hydrogen storage and electrochemical properties of La_（0.55）Pr_（0.05）Nd_（0.15）Mg_（0.25）Ni_（3.5） （Co_（0.5）Al_（0.5））_x （x=0.0, 0.1, 0.3, 0.5） alloys

The La0.55Pr0.05Nd0.15Mg0.25Ni3.5(Co0.5Al0.5)x(x=0.0, 0.1, 0.3, 0.5) alloys were prepared by magnetic levitation melting under an Ar atmosphere, and the effects of Co and Al on the hydrogen storage and electrochemical properties were systematically investigated by pressure composition isotherms, cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy testing. The results showed that the alloy phases were mainly consisted of (La,Pr)(Ni,Co)5, LaMg2Ni9, (La,Nd)2Ni7 and LaNi3 phases, and the cell volumes of (La,Pr)(Ni,Co)5, LaMg2Ni9, (La,Nd)2Ni7 and LaNi3 phases expanded with Co and Al element added. The hydrogen storage capacity initially increased from 1.36 (x=0) to 1.47 wt.% (x=0.3) and then decreased to 1.22 wt.% (x=0.5). The discharge capacity retention and cycle stability of the alloy electrodes were improved with the increase of Co and Al contents. The La0.55Pr0.05Nd0.15Mg0.25Ni3.5(Co0.5Al0.5)0.3 alloy electrode possessed better electrochemical kinetic characteristic.     

Hydrothermal synthesis, crystal structure and magnetic properties of a Dy~Ⅲ-Fe~Ⅲ heteronuclear complex

A new 3d-4f heteronuclear complex [Fe(phen)3]2[FeDy(H2O)(tiron)3]·6H2O (1,Na2H2tiron=disodium 4,5-dihydro-xybenzene-1,3disulfonate) was synthesized by the hydrothermal reaction. The complex crystallized in the cubic system, space group P213 with the cell parameters:a=2.18786(14)nm, V=10.4727(12)nm3 , Z=4, F(000)=4720, R1=0.0493, wR2 =0.1165, S=1.05. In each [FeDy(H2O)(tiron)3]6-unit, it was revealed that the Fe3+ ion was in a FeO6 distorted trigonal anti-prism coordination polyhedron completed by six phenolate O atoms from three tiron 4- ligands, while Dy3+ in a DyO7 distorted monocapped trigonal anti-prism coordination polyhedron completed by three phenolate μ2-O atoms and three O atoms from sulfonate groups of three ligands and one O atom from water. The magnetic properties of the complex was determined in the range of 2-300K, indicating the antiferromagnetic interaction between the central DyIII-FeIII ions.     

Spectroscopic properties of ytterbium doped KLu（WO_4）_2

Monoclinic Yb3+-doped KLu(WO4)2 (Yb:KLuW) crystal with large sizes was grown by top-seeded solution growth (TSSG) method. Room-temperature absorption and fluorescence spectra were measured. The ground-state energy-level splitting was 562 cm-1. The absorption cross section, peak emission cross section as well as the minimum inversion fraction ?min and the minimum absorbed pump intensity Imin were calculated. The measured emission lifetime was 0.676 ms and the emission spectral bandwidth (FWHM) was up to 55 nm. In comparison with established laser crystals the results suggested that this crystal has potential application in efficient tunable and femtosecond laser operation.     

Investigation of Pt-Dy co-doping effects on isothermal oxidation behavior of （Co,Ni）-based alloy

A Co32Ni21Cr8Al0.6Y (wt.%) alloy with and without doping 3 wt.% platinum, or co-doping 3 wt.% platinum and 0.1 wt.% dysprosium was produced by arc melting. The hardness of both base alloy and composition-modified alloy was measured by using a Vickers hardness tester. Isothermal oxidation tests at 1000 ℃ in static air atmosphere were conducted to assess the isothermal oxidation behavior of the alloys. The microstructure and composition of the tested alloys before and after oxidation were investigated by means of X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) equipped with energy dispersive spectroscopy (EDS) and back scatter detector. Results showed that platinum had significant influence on microstructure of the tested alloy by the formation of β-(Ni,Pt)Al phase. Addition of 3 wt.% platinum could slightly increase the hardness of the tested alloy. Platinum accelerated phase transformation of alumina from metastable θ-Al 2 O 3 to stable α-Al 2 O 3 and suppressed the consumption of β-phase. Co-doping both 3 wt.% platinum and 0.1 wt.% dysprosium induced the fastest transformation of θto αalumina and the formation of a fine-grained oxide scales. The most effective reduction of oxidation rate was achieved by the Pt-Dy co-doping effects.     

Nucleation undercooling,solidification structures and magnetic properties of Nd_9Fe_(85–x)Ti_4C_2B_x (x=10–15) magnetic alloys

Nd_9Fe_(85–x)Ti_4C_2B_x(x=10–15) magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, the liquidus temperatures TL of the alloys decreased from 1498.5 to 1472.5 K; the solidus temperatures TS of them increased from 1353.2 to 1358.3 K; and the nucleation undercooling of the alloy melts cooled at the rate of 40 K/min decreased from 122.8 to 95.9 K, resulting in the solidification structures consisting of Nd_2Fe_(14)B, Fe_3B, α-Fe, Nd1.1Fe4B4 and TiC nanocrystallines. Furthermore, the Nd_9Fe_(85–x)Ti_4C_2B_x(x=11, 13, 15) bulk alloys in sheet form with the thickness of 0.7 mm were prepared by copper mold suction casting and their solidification characteristics and solidification structures under sub-rapidly cooling rate were investigated. The results showed that partially amorphous structures were obtained in the as-cast bulk alloys and the amount of amorphous decreased with the increase of the B content. By annealing the as-cast bulk alloys at 923 K for 10 min, the nanocomposite microstructures composed with Nd_2Fe_(14)B, Fe_3B and α-Fe nanocrystallines, which showed a single-phase hard magnetic behavior and enhanced magnetic properties, were achieved.     

Luminescent properties of dysprosium（Ⅲ） ions in LaAlO3 nanocrystallites

The absorption and emission spectra as well as decay time profile of Dy3+ ions in LaAlO3 nanocrystals were analyzed.The crystal structure of LaAlO3 was confirmed from XRD measurement.The emission peaks from blue to red came from main emitting level of dyspro-sium 4F9/2 to the ground and other excited levels of Dy3+ ions.Cross relaxation process led to non-radiative quenching of luminescence,so that the lifetime of the 4F9/2 energy level ions decreased with increasing amount of doped Dy3+ ions.The cross relaxation transfer rates were ex-perimentally determined as a function of Dy3+ concentration.     

Effect of copper ion implantation on corrosion morphology and corrosion behavior of LaFe_（11.6）Si_（1.4） alloy

The morphology analysis and electrochemical method were used to study the corrosion behavior of LaFe11.6Si1.4 alloy of copper ion implantation. X-ray photoelectron spectroscopy (XPS) and atomic emission spectroscopy (AES) research results showed that a 15 nm-thick oxide film was formed on the surface of sample, and the copper content reached the highest value at 60 nm with a normal distribution. Immersion experiments indicated that the corrosion happened in the copper-poor zone firstly and a galvanic connection was formed among different zones on the surface due to the inhomogeneous distribution of copper. Electrochemical experiment results showed that the corrosion was serious when the ion acceleration voltage increased, and the high acceleration could reduce the thermodynamic performance of corrosion of LaFe11.6Si1.4 alloy.     

Studies on electrical properties and CO-sensing characteristics of La_（0.9） _（0.1）FeO_3

Semiconducting sensors offer an inexpensive and simple method for monitoring gases. Sensors based on the ABO3-type composite oxides materials have an advantage of high stability. The perovskite structures of these compounds are preserved, when an A-site deficiency of some perovskite structure compounds was formed. However, they exhibit particular physical properties. In this paper, La0.9 0.1FeO3 powder with an orthorhombic perovskite phase was prepared by sol-gel method. The electrical properties and CO-sensing characteristics of the La0.9 0.1FeO3 were also investigated. The results demonstrated that the La0.9 0.1FeO3 was a p-type semiconductor material. Compared with LaFeO3, the conductance of La0.9 0.1FeO3 was better than that of LaFeO3. The sensor based on La0.9 0.1FeO3 showed excellent CO gas-sensing characteristics.     

Luminescent properties of Eu（OA）3（TTA）/NBR composites prepared by in-situ reaction

Eu(OA)3(TTA) (OA=cis-9-octadecenoic acid, TTA=4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione) complexes (Eu- complexes) containing the ligand OA with long molecular chains were synthesized. The Eu(OA)3(TTA) complexes and peroxide were added into nitrile-butadiene rubber (NBR) by mechanical shearing to get the uncured composites. The cured composites were obtained by vulcanizing the uncured composites at high temperature. The in-situ reaction including polymerization and grafting of Eu-complex took place at the curing process, which was verified by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations showed the fine dispersion of Eu(OA)3(TTA) complex (Eu-complex) in the cured composites compared with the uncured ones. Fluorescent spectra and Judd-Ofelt parameters analysis revealed that the fluorescent intensity increased approximate linearly with the content of Eu- complex increasing due to the in-situ reaction and long molecular chains of OA. The fluorescent lifetime of composites was longer than that of original Eu-complexes.     

Reversible control of magnetic and transport properties of NdNiO3-δepitaxial films

Rare-earth nickelates possess intrinsic charge order,orbital order,and electron-lattice coupling,which make them very interesting for applications in oxide-based electronic devices.In this study,we grew NdNiO_3-δ(NNO) films with oxygen pressures changing from 27 to 10^-5 Pa.With decreasing oxygen pressure,the antiferromagnetic state of the NNO film becomes a ferromagnetic state,and the resistance increases significantly.According to combined X-ray absorption spectro scopy and X-ray linear dichroism measurements,the ratio of Ni²⁺-ions increases with decreasing oxygen-pressure,and the preferred orbital occupation changes from x²-y² to 3 z²-r².In addition,using the ionic-liquid gating method to control the migration of oxygen vacancies,both the magnetic properties and resistance of NNO films can be modulated reversibly.The oxygen vacancy induces a valence in the Ni ions and the orbital occupation changes,which alters the magnetic properties and the electronic transport in these NNO films.This study describes a novel tunable method for electronic devices that use NdNiO_3-δ films,and opens new doors for future improvements and functionalities.     

Luminescent properties of Eu~（3＋） doped Gd_2WO_6 and Gd_2（WO_4）_3 nanophosphors prepared via co-precipitation method

Eu3+ doped Gd2WO6 and Gd2(WO4)3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated, and the concentration quenching of Eu3+ luminescence in different matrixes were studied. The results indicated that effective Eu3+:5D0-7F2 red luminescence could be achieved while excited by 395 nm near-UV light and 465 nm blue light in Gd2WO6 host, which was similar to the familiar Gd2(WO4)3:Eu. Therefore, the Gd2WO6:Eu red phosphors might have a potential application for white LED.