Electrochemical behavior of Ce（III） in LiF-BaF2 melts

The electrochemical behavior of Ce(III) was investigated in the molten LiF-BaF2 (81 mol.%-19 mol.%) on a molybdenum elec-trode in the temperature range of 1098-1188 K using cyclic voltammetry and chronopotentiometry. It was observed that CeF3 could be re-duced into cerium metal in a reversible one-step process exchanging three electrons (Ce(III)+3e-→Ce(0)) at the operating temperatures on a molybdenum cathode. The electrochemical reduction process was controlled by the diffusion of Ce(III) in the solution. The Ce(III) diffusion coefficients were calculated at different temperatures and the values obeyed the Arrhenius law with an activation energy of 87.5 kJ/mol.     

Investigation on Pulverized Coal Combustion Behavior by Non-Isothermic Integral Thermogravimetry Method

 The combustion process of pulverized coal was investigated by non-isothermic integral thermogravimetry. The thermogravimetry curves were fitted by the Coats-Redferm approximation function, and kinetic parameters and characteristic temperatures were obtained. The optimal mixing ratio and particle size can be ascertained. The characteristic temperature of pulverized coal can be obtained from the thermogravimetry curve, and the combustion of coal can be divided into homogeneous and heterogeneous combustion according to the differential thermal analysis curve. The activation energy of a single type of coal ranking from low to high is as follows: bituminous coal, meager-lean coal, and anthracite. In the first mixing method, with more low-price meager-lean coal B replacing high-price anthracite A, the activation energy slightly decreases; with more bituminous coal replacing meager-lean coal, total tendency makes a declining of activation. In the later mixing method, with an increase in particle size, a declining activation energy can be seen in total tendency.     

Study on the adsorption of lanthanum(Ⅲ) from aqueous solution by bamboo charcoal

The adsorption behaviors of La(Ⅲ) ion on bamboo charcoal were investigated with various chemical methods and IR spectrometry. Parameters studied include the effects of pH,average particle size,initial ion concentration,contact time and temperature by batch method. The results showed that bamboo charcoal could remove La(Ⅲ) ions effectively from aqueous solution. The loading of La(Ⅲ) ions was strongly dependent on pH of the medium and the optimal adsorption condition was in HNO3-TEA medium with pH value of 7.20. In the batch system,the modified bamboo charcoal exhibited the highest La(Ⅲ) ion uptake as 120 mg/g at 298 K,at an initial pH value of 7.20. The adsorption kinetics were tested with Lagergren-first-order model and pseudo-second-order model. The adsorption data were conformed to the Langmuir and Freundlich isotherms,and the correlation coefficients had been evaluated. Thermodynamic parameters such as free energy(ΔG) ,which were all negative,indicated that the adsorption of La(Ⅲ) ion onto bamboo charcoal was spontaneous and the positive value of enthalpy(ΔH) showed that the adsorption was endothermic in nature. Thomas model was applied to experimental column data to determine the characteristic parameters of column useful for process design. The characterization of both before and after adsorption of La(Ⅲ) ion on bamboo charcoal was undertaken using IR spectroscopic technique. The results revealed that bamboo charcoal was a good choice as a biosorbent for the recovery of lanthanum from aqueous solution.     

Measurements of Enthalpy Change of Reaction of Formation, Molar Heat Capacity and Constant-Volume Combustion Energy of Solid Complex Yb（Et2dtc）3（phen）

A ternary solid complex Yb(Et2dtc)3(phen) was obtained from the reaction of hydrous ytterbium chloride with sodium diethyldithiocarbamate (NaEt2dtc), and 1, 10-phenanthroline (o-phen·H2O) in absolute ethanol.The bonding characteristics of the complex were characterized by IR.The result shows Yb3 bands with two sulfur atoms in the Na(Et2dtc)3 and two nitrogen atoms in the o-phen.The enthalpy change of liquid-phase reaction of formation of the complex ΔrHθm (l), was determined as being (-24.838±0.114) kJ·mol-1 at 298.15 K, by an RD-496 Ⅲ type heat conduction microcalormeter.The enthalpy change of the solid-phase reaction of formation of the complex ΔrHθm (s), was calculated as being (108.015±0.479) kJ·mol-1 on the basis of an appropriate thermochemistry cycle.The thermodynamics of liquid-phase reaction of formation of the complex was investigated by changing the temperature during the liquid-phase reaction.Fundamental parameters, the activation enthalpy, ΔHθ≠, the activation entropy, ΔSθ≠, the activation free energy, ΔGθ≠, the apparent reaction rate constant k, the apparent activation energy E, the pre-exponential constant A, and the reaction order n, were obtained by a combination of the reaction thermodynamic and kinetic equations with the data from the thermokinetic experiments.At the same time, the molar heat capacity of the complex cm, p, was determined to be (86.34±1.74) J·mol-1·K-1 by the same microcalormeter.The constant-volume combustion energy of the complex, ΔcU, was determined to be (-17954.08±8.11) kJ·mol-1 by an RBC-Ⅱ type rotating-bomb calorimeter at 298.15 K.Its standard enthalpy of combustion, ΔcHθm, and standard enthalpy of formation, ΔfHθm, were calculated to be (-17973.29±8.11) kJ·mol-1 and (-770.36±9.02) kJ·mol-1, respectively.     

Synthesis and Photoluminescence Properties of Rare Earth Complexes with 3-Allyl-2, 4-Pentanedione

In order to combine the merits of rare earth organic complexes with excellent material performances of polymers,a polymerizable chelating agent, 3-allyl-2, 4-pentane dione (APD), was synthesized by phase transfer catalysis and its rare earth complexes were prepared. The compounds were characterized by EA, IR and ^1H NMR. Their UV spectra and fluorescence spectra were investigated. The effects of allyl on the luminescence properties of the complexes were studied.The results show that the sensitization of APD is changed by allyl in comparison with that of acetyl acetone (acac), and it becomes an ideal novel ligand of Eu. In addition, intramolecular energy transfer mechanism in the luminescence process in the complexes was also discussed in detail.     

Enhanced adsorption behavior of Nd（Ⅲ） onto Dll3-Ⅲ resin from aqueous solution

An enhanced adsorption and desorption procedure of Nd(III) onto D113-III resin were prepared with various chemical methods.Batch studies were carried out with various pH,contact time,temperature and initial concentrations,and then column studies were conducted.The results showed that the optimal adsorption condition was at pH value of 6.90.The process was fast initially and arrived equilibriumwithin 60 h.The resin exhibited a high Nd(III) uptake as 232.56 mg/g at 298 K.The adsorption data fitted well with pseudo-second-order kinetic model.Thermodynamic parameters were studied,which indicated that the adsorption process was spontaneous and endothermic.Thomas model was delineated here to predict the breakthrough curves based on the experimental column study data.In the elution test,1 mol/LHCl solution could achieve a satisfactory elution rate,which indicated that D113-III resin could be regenerated and reused.Finally,the IRspectroscopic technique was undertaken,and a novel adsorption mechanism was proposed.     

Column leaching of lanthanides from Abu Tartur phosphate ore with kinetic study

The dynamic leaching of lanthanides from a west desert phosphate ore, Egypt (Abu Tartur) by hydrochloric acid, nitric acid and sulfuric acid solutions was investigated in this study as a function of acid concentration, flow rate and the presence of some additives such as boric acid. Also the kinetics of leaching of lanthanides was investigated as a function of temperature. It was found that the leaching process could be described by a shrinking-core model, with activation energy about 5.9, 13.8 and 21.9 kJ/...     

Synthesis,spectral characterization,thermal and biological studies of lanthanide（III） complexes of oxyphenbutazone

Lanthanide（III） complexes of 4-butyl-1-（4-hydroxyphenyl）-2-phenyl-3,5-pyrazolidinedione （OPB） were prepared by ho-mogeneous precipitation. The solid complexes were characterized by elemental analysis, magnetic susceptibility data, molar conduc-tivity measurements and IR, UV-Vis, mass, 1H NMR and 13C NMR spectral methods. The thermal decomposition of the complexes under static air atmosphere was investigated by simultaneous TG/DTG at a heating rate of 10 °C/min. The final decomposition prod-ucts were found to be metal oxides. The spectroscopic data suggested that OPB acted as a bidentate, mono-ionic ligand coordinating through two carbonyl oxygens of the pyrazolidinedione ring. The kinetic and thermodynamic parameters such as activation energy, pre-exponential factor and entropy of activation for each step of the decomposition reactions were evaluated using Coats-Redfern and MacCallum-Tanner equations. The negative entropy values of the complexes indicated that the activated complexes had a more or-dered structure than the reactant and that the reactions were slower than normal. Investigations of antimicrobial activity of the com-pounds were carried out by the disk diffusion technique.     

Thermogravimetric Analysis of Coal Char Combustion Kinetics

Four chars prepared from pulverized coals were subjected to non-isothermal and isothermal combustion tests in a thermogravimetric analysis(TGA)device.Three different test methods,i.e.,non-isothermal single heating rate(A),non-isothermal multiple heating rate(B),and isothermal test(C),were conducted to calculate the kinetic parameters of combustion of coal char.The results show that the combustion characteristics of bituminous coal char is better than that of anthracite char,and both increase of heating rate and increase of combustion temperature can obviously improve combustion characteristics of coal char.Activation energies of coal char combustion calculated by different methods are different,with activation energies calculated by methods A,B and C in the range of 103.12-153.77,93.87-119.26,and 46.48-76.68kJ/mol,respectively.By using different methods,activation energy of anthracite char is always higher than that of bituminous coal char.In non-isothermal tests,with increase of combustion temperature,the combustion process changed from kinetic control to diffusion control.For isothermal combustion,the combustion process was kinetically controlled at temperature lower than 580℃ for bituminous coal char and at temperature lower than 630℃ for anthracite char.     

Activation Energy of Nitriding Medium Carbon Ferromanganese Alloy

Investigation of some kinetics aspects of the reaction between nitrogen and medium carbon ferromanganese (MC-FeMn) was made. Nitriding process of fine medium carbon ferromanganese was carried out at temperature ranging from 973 to 1 223 K and time up to 480 min. Nitriding was carried out under nitrogen and hydrogen gas pressures. At temperature of 573 K, hydrogen gas was injected with pressure of about 0.2 MPa followed by injection of nitrogen gas up to 1.2 MPa. Sample mass was 35 g, nitrided in cylindrical chamber with 34 mm in inner diameter and 1 200 mm in length. The change in nitrogen pressure was taken as an indication for nitrogen pickup. The mass gain i.e. nitrogen pickup in kilograms per surface area (m2) was determined by time at different temperatures. Nitriding rate constants were calculated and the activation energy of nitriding process was derived from Arrhenius equation. The nitriding rate constant was found to be increased by increasing temperature of the reaction. The activation energy of nitriding process of fine medium carbon ferromanganese at time ranging up to 28 800 s is around 140 kJ/mol. It was found that the rate controlling step of the nitriding process of MC-FeMn is diffusion mechanism.     

Thermochemistry on Coordination Behavior of Neodymium Chloride Hydrate with Diethylammonium Diethyldithiocarbamate

The complex of neodymium chloride lower hydrate with diethylammonium diethyldithiocarbamate (D-DDC) was synthesized conveniently in absolute alcohol and dry N2 atmosphere. The title complex was identified as Et2NH2 [ Nd(S2CNEt2)4] by chemical and elemental analyses and the bonding characteristics of which was characterized by IR. The enthalpies of solution of neodymium chloride hydrate and D-DDC in absolute alcohol at 298.15 K and the enthalpies change of liquid-phase reaction of formation for Et2NH2[ Nd (S2CNEt2)4] at different temperatures were determined by microealorimetry. On the basis of experimental and calculated results, three thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), the rate constant and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of liquid-phase reaction of formation were obtained.The enthalpy change of the solid-phase title reaction at 298.15 K was calculated by a thermochemical cycle.     

Grain Refinement in a Low Carbon Steel Through Multidirectional Forging

 Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique at room temperature. The influence of strain amount and annealing process on the microstructure and mechanical properties of investigated steel was studied. The grain refinement mechanism was studied by the microstructure observation. The results showed that the grain refinement was attained by multidirectional forging technique. The initial coarser grains of average 38 μm size fragmented into very fine ferrite with grain sizes of about 1.2 μm. After MDF, the strength properties improved significantly, although uniform elongation and elongation decreased with increasing strain.     

Enhancing the performance of photovoltaic cells by using down-converting KCaGd（PO_4）_2：Eu~（3＋） phosphors

The goal of this work is aimed to improve the power conversion efficiency of single crystalline silicon-based photovoltaic (PV) cells by using the solar spectral conversion principle, which employed a down-converting phosphor to convert a high-energy ultraviolet photon to the less energetic red-emitting photons to improve the spectral response of Si solar cells. In this study, the surface of silicon solar cells was coated with a red-emitting KCaGd(PO4)2:Eu3+ phosphor by using the screen-printing technique. In addition to the investigation on the microstructure using scanning electron microscopy (SEM), we measured the short circuit current (Isc), open circuit voltage (Voc), and power conversion efficiency (η) of spectral-conversion cells and compared with those of bare solar cells as a reference. Preliminary experimental results revealed that in an optimized PV cell, an enhancement of (0.64+0.01)% (from 16.03% to 16.67%) in Δη of a Si-based PV cell was achieved.     

Synthesis,spectral characterization,thermal and biological studies of lanthanide(Ⅲ) complexes of oxyphenbutazone

Lanthanide(III) complexes of 4-butyl-1-(4-hydroxyphenyl)-2-phenyl-3,5-pyrazolidinedione(OPB) were prepared by homogeneous precipitation. The solid complexes were characterized by elemental analysis, magnetic susceptibility data, molar conductivity measurements and IR, UV-Vis, mass,1H NMR and13C NMR spectral methods. The thermal decomposition of the complexes under static air atmosphere was investigated by simultaneous TG/DTG at a heating rate of 10 °C/min. The final decomposition products were found to be metal oxides. The spectroscopic data suggested that OPB acted as a bidentate, mono-ionic ligand coordinating through two carbonyl oxygens of the pyrazolidinedione ring. The kinetic and thermodynamic parameters such as activation energy, pre-exponential factor and entropy of activation for each step of the decomposition reactions were evaluated using Coats-Redfern and MacCallum-Tanner equations. The negative entropy values of the complexes indicated that the activated complexes had a more ordered structure than the reactant and that the reactions were slower than normal. Investigations of antimicrobial activity of the compounds were carried out by the disk diffusion technique.     

Effects of yttrium on recrystallization and grain growth of Mg-4.9Zn-0.7Zr alloy

Recrystallization and grain growth in Mg-4.9Zn-0.7Zr and Mg-4.9Zn-0.9Y-0.7Zr alloys as a function of temperature on deformation were investigated with regards to hot rolling and annealing. The influence of yttrium addition on the microstructure was examined by X-ray diffraction （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results indicated that yttrium addition promoted nucleation of recrystallization during hot rolling process. The grain size of Mg-4.9Zn-0.7Zr alloy samples grew significantly with annealing temperature （300-400 ℃） and holding time （0-120 min）, while the microstructure of the alloy with yttrium addition remained unchanged and fine. The activation energy of grain boundary migration for Mg-4.9Zn-0.9Y-0.7Zr alloy samples （56.34 kJ/mol） was higher than that for Mg-4.9Zn-0.7Zr （42.66 kJ/mol） owing to the pinning effect of Y-containing particles. The proposed growth models of recrysta/lized grains for the two studied alloys conformed well to E. Robert＇s grain-growth equation. Besides, the ultimate strength and yield strength of the alloys with yttrium addition were improved with good plasticity.     

Oxidation Desulfurization Activity of Phosphotungstic Acid Supported on Yttrium-Modified USY

Y-Modified USY was prepared by ion exchange of USY slurry with 0.01 mol·L-1 Y (NO3)3. Phosphotungstic acid (HPW) catalyst supported on USY and Y-USY was prepared by an impregnation method. The materials were characterized by NH3-TPD, XRD, and N2 adsorption. The activity for the removal of thiophene was examined in a three-necked flask. The sulfur content of model compound was tested on WK-2D microcoulometric detector. The effect of yttrium and HPW content, reaction temperature and catalysts, activation temperature on the activity of catalysts were investigated. It was shown that the oxidation activity of thiophene decreased with the increase of Y content except for the catalyst of Y 5%. HPW content had limit influence on activity of catalysts. The optimal reaction temperature and activation temperature were 40 and 320℃, respectively.     

Reduction kinetics of Fe<Subscript>2</Subscript>MoO<Subscript>4</Subscript> fine powder by hydrogen in a fluidized bed

Iron molybdate (Fe₂MoO₄) powders with an average particle size of 100 μm were reduced by hydrogen using a fluidized-bed batch reactor in the temperature range of 923 to 1173 K. The extent of the reaction was followed as a function of time by gas chromatography. The fluidizing-gas velocity was set at about 1.5 times the minimum fluidization velocity. The ratio of the height of the static bed to its diameter is about 1. Under the prevailing experimental conditions, it was found that the chemical reaction was the rate-controlling factor. The activation energy for this process was 158±17 kJ/mol. The crystal size of the Fe₂Mo powder produced at lower temperatures was in the nanometer range, indicating the possibility of mass production of alloys and intermetallics in the nanorange, using a fluidized bed.     

Electrochemical behavior of cerium（IV） in a RTIL and its mixture with ethanol

A systematic study was carried out to explore the electrochemical behavior of Ce in room temperature ionic liquid（CnmimBr, where n=6, 8, 10） and mixture of C6 mimBr and ethanol by cyclic voltammetry. With increase in the number of carbon atoms on the alkyl substituent on methyl imidazolium cation, the electrochemical window of the ionic liquids was found to extend towards more negative potential value, as a result there was a possibility of reduction of Ce to lower oxidation states. The diffusion coefficient and activation energy for the diffusion were calculated in all the ionic liquids and one of their mixtures with ethanol. With increase in n value, the diffusion coefficient of Ce decreased due to increase in viscosity of the medium while the activation energy for the diffusion followed a reverse trend for C6 mimBr, C8 mimBr and C10 mimBr, respectively. The observations indicated that the nature of species of Ce might be different in room temperature ionic liquids（RTILs） from that present in their mixtures with ethanol.     

Densification and anticorrosion performances of vacuum evaporated aluminium coatings on NdFeB magnets

Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,respectively.The anticorrosive properties were investigated by potentiodynamic polarization curves and neutral salt spray test.The pores in the Al coatings of columnar crystals(Al) induced by the evaporation technique,were apparently filled in the following ball milling process,leading to the densification of Al coatings and the evident improvement of the anticorrosive performances.When treated with ball milling for 30 min,the sample achieves the best anticorrosive performances with the self-corrosion potential of-0.87 V,self-corrosion current density of 1.65 μA/cm~2 and the neutral salt spray(NSS) time of 144 h(red rust).The improvement of the anticorro sive performances of vacuum evaporated Al coating mainly lies in the densification effect of the coating,which depends on different loading conditions of ball milling process.     

Oxidation kinetics of ilmenite concentrate by non-isothermal thermogravimetric analysis

The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of apparent activation energy(Ea)were evaluated by Málek and Starink methods.The results show that under air atmosphere,the oxidation process of ilmenite concentrate is composed of three stages,and the chemical reaction(G(α)=1-(1-α)~2,whereαis the conversion degree)plays an important role in the whole oxidation process.At the first stage(α=0.05-0.30),the oxidation process is controlled gradually by secondary chemical reaction with increasing conversion degree.At the second stage(α=0.30-0.50),the oxidation process is completely controlled by the secondary chemical reaction(G(α)=1-(1-α)~2).At the third stage(α=0.50-0.95),the secondary chemical reaction weakens gradually with increasing conversion degree,and the oxidation process is controlled gradually by a variety of functions;the kinetic equations are G(α)=(1-α)~(-1)(β=10K·min~(-1),whereβis heating rate),G(α)=(1-α)~(-1/2)(β=15-20K·min~(-1)),and G(α)=(1-α)~(-2)(β=25K·min~(-1)),respectively.For the whole oxidation process,the activation energies follow a parabolic law with increasing conversion degree,and the average activation energy is 160.56kJ·mol~(-1).