Effects of RE and Vanadium on Microalloyed Steel

The effects of RE were studied by TEM, SEM, ICP and thermal simulation methods in vanadium microalloyed steel. The content.of RE in the solid solution can reach the order of 10^-5 --10^-4 in steel. The solid solution of RE was found to reduce the stability of precipitated V (C, N ), impede the precipitation of V (C, N ) in austenite, and accelerate and refine the precipitation of V (C, N) in ferrite. The combined effect of RE and V is to delay the dynamic recrystaUization, refine the grains and second phase particles, and to promote the precipitation of V (C, N) obviously. Thus the microalloying with RE and V leads to raising the strength and toughness of steel.     

Thermochemical Properties of the Complexes RE(HSal)3·2H2O (RE=La, Ce, Pr, Nd, Sm)

Five solid rare earth salicylate complexes were synthesized by low hydrated lathanide chloride and salicylic acid. The complexes in this experiment were identified as the general formula RE(Hsal)3·2H2O(RE=La, Ce, Pr, Nd, Sm) by elemental analysis and EDTA volumetric analysis. IR spectra of the complexes show that carboxyl of salicylic acid coordinates to RE3 ions. Electrochemical behaviors of the complexes on the glass-carbon electrode were researched with cyclic voltammetry (CV). It is indicated that the electrochemical process of the complexes is a one-electron redox process and the electrochemical reversibility of complexes is less than that of the lanthanide chlorides. The constant-volume combustion energies of complexes, ΔcU, were determined with a precise rotating-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, ΔcHθm, and standard molar enthalpies of formation, ΔfHθm, were calculated.     

RARE EARTH DISSOLVED IN SOLID SOLUTION OF STEEL AND ITS EFFECT ON MICROSTRUCTURE

The amounts of rare earth in the solid solution in steel 16Mn were determined by means of inductivecoupling plasma(ICP)spectroscopy.While the RE/S ratio was less than 1.9,the amounts of rare earth insolid solution were not more than 8 ppm,which rised slightly with the increase of the rare earth content in thesteel.While the RE/S was more than 1.9,MnS disappeared completely in the steel and the amounts of rareearth in solid solution increased rapidly with the increasing of the rare earth content.The solubility of ceriumin steel 16 Mn(St 52)is less than 0.011 wt% at room temperature.The results also indicate that rare earth insolid solution can reduce the amount of pearlite and increase that of ferrite and its mierohardness.The rela-tionship between microhardness(Hv)and the amount of rare earth in solid solution can be expressed by theequation of Hv=117 7 RE(ppm).     

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.     

Analysis of Valence Electron Structure of RE in Solid Solution in Medium and Low Carbon Steel

According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and recrystallization of martensite was explained by the valence electron structure data of phases. Calculating results indicate that C element is favorite to enhance the number of RE in the solid solution. RE in the solute solution shortens the incubation period of proeutectoid ferrite, increases its quantity and carbon content, decreases the quantity of pearlite and thickness of its lamellas and lamellar spacing, then the strength and hardness of pearlite are improved and granular pearlite can be obtained. RE dissolved in martensite intensifies martensite, enhances tempering stability of martensite, increases its recrystallization temperature and prolongs the holding time needed during tempering.     

Standard Molar Enthalpy of Formation of RE（ C5H8NS2 ）3 （C12H8N2）

Four solid ternary complexes of RE (C5H8NS2)3(C12H8N2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamate (APDC) and 1, 10-phenanthroline*H2O (o-phen*H2O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes show that the RE3 coordinated with six sulfur atoms of three PDC- and two nitrogen atoms of o-phen*H2O. It was assumed that the coordination number of RE3 is eight. The constant-volume combustion energies of the complexes, ΔcU, were determined as (-16937.88±9.79 ), (-17588.79±8.62 ), (-17747.14±8.25 ) and (-17840.37±8.87 ) kJ*mol-1, by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, ΔcHθm, and standard molar enthalpies of formation, ΔfHθm, were calculated as (-16953.37±9.79), (-17604.28±8.62), (-17762.63±8.25), (-17855.86±8.87) kJ*mol-1 and (-857.04±10.52), (-282.43±9.58), (-130.08±9.13), (-55.75±9.83) kJ*mol-1.     

Novel Approach to Characterization of Rare Earth Complexation with 1, 5-Bis（2-Hydroxy-5-Chlorphenyl）-3-Cyanoformazan in Presence of Cetyltrimethylammonium Bromide

The ternary interaction of 1, 5-bis ( 2-hydroxy-5-chlorphenyl )-3-cyanoformazan (HCPCF) with cetyhrimethylammonium bromide (CTAB) and rare earths (RE: Yb, Dy, Er and Eu) was investigated at pH 9.84 by the microsurface adsorption - spectral correction technique (MSASC). The aggregation of HCPCF on CTAB obeys the Langmuir isothermal adsorption and the interaction of RE with the HCPCF-CTAB aggregate was first found to accord with the monolayer binding. The effects of temperature and ionic strength of solution on the aggregations were made. The binary aggregate and the ternary complex were characterized.     

Study on Rare Earth Electrolyte of Ce0.9 RE0.102－δ （RE=Pr, Nd, Sm,Gd, Dy）

The solid solutions Ce0.9RE0.102-δ(RE=Pr,Nd,Sm,Gd,Dy) were prepared by sol-gel method, The XRD measurement shows that the solid solution is crystallized in cubic fluorite-type structure and the cell volume of Ce0.9RE0.1O2-δ decreases with the increase of atomic number of RE. The ionic conduction for Ce0.9RE0.1O2-δ was measured by impedance spectroscopy and Ce0.9Pr0.1O2-δ has better conductivity. The linear thermal expansion of Ce0.9RE0.1O2-δ decreases with the increase of atomic number of RE.     

Effects of Rare Earth Oxide on Viscosity of Mold Fluxes for Continuous Casting

The effects of RE (rare earth) oxide on viscosity of mold fluxes were investigated with a rotary viscometer. The results show that : (1) The viscositv of mold fluxes is remarkably inereased by RE oxide addition, especially when the mass fraction of RE oxide is more than 10%. (2) By addition of RE oxide, precipitation of the insohlble particles with high melting point from the molten slag with the decreasing of the temperature leads to the inerease of viscosity. Viscosity curve shows that RE oxide is soluble in some extent in mold fluxes. When RE oxide is in a state of supersaturation, the existence of insoluble particles also makes the viscosity of mold fluxes increase. (3) Not only the viscositv of nlold fluxes can be reduced, but also the capacity to dissolve and absorb RE oxide can be increased by Li2O, B2O3 and BaO. However, the contents of Li2O, B2O3, and BaO should be controlled to suitable levels. (4) The solidification temperature of mold fluxes can be increased by the addition of RE oxide, which is unfavorable to heat transfer and luhrication of mold fluxes between steel shell and mold.     

Precipitation transformation of rare earth sulfate into chloride with p-dodecylphenoxy carboxylic acids

Methods for transforming rare earth(RE) sulfate into chloride mainly include extraction process with organophosphonic mono-acids or aliphatic acids and precipitation process with ammonium bicarbonate(NH_4 HCO_3).In this paper,alkylphenoxy carboxylic acids(HAs) ofp-dodecylphenoxy acetic acid(HA-Ⅰ),pdodecylphenoxypropanoic acid(HA-Ⅱ) and p-dodecylphenoxybutyric acid(HA-Ⅲ),which were liquid at room temperature were synthesized and characterized.The precipitation mechanisms of RE elements with the HAs were investigated and the HA/RE molar ratios of the solid complexes were determined as3:1 by equi-molar series method which accord with the principle of charge balance.Applicability of HAs for the transformation of RE sulfate from concentrated sulfuric acid roasted RE concentrate into chloride via precipitation method was discussed.100% HA-Ⅱ was selected as the liquid organic precipitant without dilution of volatile solvent soracceleration of phase separation by phase-modifiers.The RE sulfate solution can be precipitated by HA-Ⅱ after neutralization with liquid NaOH and stripped with concentrated HCl at room temperature.High concentration of RE chloride of 218.1 g/L with low residue of sulfate radical of 0.536 g/L was obtained.The residual organic precipitant in the raffinate solution was tested to be lower than 8 mg/L at 25℃and the chemical oxygen demand(COD) in wastewater was less than 50 mg/L.     

Synthesis and fluorescence properties of Eu（Ⅲ）, Tb（Ⅲ） and Sm（Ⅲ） with β-diketone and 2,2＇- bipyridine

Three new rare earth ternary complexes,RE(PPP)3bpy(RE=Sm 3+ ,Eu 3+ ,Tb 3+ ),were synthesized by the reaction of 1-phenyl-3-(p-phenylethynylphenyl)-1,3-propanedione(HPPP)and 2,2′-bipyridine(bpy)with rare earth chloride RECl3,respectively,in alcohol solution. The compositions were characterized by means of infrared(IR)spectra,chemical analysis,elemental analysis,and thermodynamic analysis.Luminescent properties of the three complexes were studied.At room temperature,under UV light excitation,the Sm 3+ ,Eu 3+ and Tb 3+ complexes exhibited characteristic emission of the central ions.The fluorescence spectra showed that the fluorescence emission intensity of Eu 3+ complex was the strongest.The narrow strongest emission band of Eu 3+ complex was considered to be a valuable material with bright red fluorescence.     

Separation of Eu（III） with supported dispersion liquid membrane system containing D2EHPA as carrier and HNO3 solution as stripping solution

The Eu(III) separation in supported dispersion liquid membrane (SDLM),with polyvinylidene fluoride membrane (PVDF) as the support and dispersion solution containing HNO3 solution as the stripping solution and Di(2-ethylhexyl) phosphoric acid (D2EHPA) dis-solved in kerosene as the membrane solution,was studied.The effects of pH value,initial concentration of Eu(III) and different ionic strengths in the feed phase,volume ratio of membrane solution and stripping solution,concentration of HNO3 solution,concentration of carrier,different stripping agents in the dispersion phase on the separation of Eu(III) were also investigated,respectively.As a result,the optimum separation conditions of Eu(III) were obtained as the concentration of HNO3 solution was 4.00 mol/L,concentration of D2EHPA was 0.160 mol/L,and volume ratio of membrane solution to stripping solution was 30:30 in the dispersion phase,and pH value was 5.00 in the feed phase.Ionic strength had no obvious effect on the separation of Eu(III).Under the optimum conditions studied,when initial concentration of Eu(III) was 1.00×10–4 mol/L,the separation rate of Eu(III) was up to 94.2% during the separation period of 35 min.The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry.The results were in good agreement with the literature data.     

Effect of Rare Earth Elements on Quantity Growth of Ctrps

The effects of rare earth on the growth of rice,rape and soybean in three kinds of soils were studied with the method supposed by Economic Co-operation and Development organization(OECD),and the EC50(median growth concenrtation)values were obtained,The inhibition of RE on the growth of rice and rape in red soil and on the growth of soybeanin yellow fouvo-aquic soil is higher with stronger poison effects.Compared with other heavy metals such as Hg,Cd,Pb,As,the poison of RE on crops in weaker.     

Effect of rare earth addition on microstructure and corrosion behavior of plasma nitrocarburized M50NiL steel

M50NiL steel was plasma nitrocarburized at 480 °C with and without rare earth(RE) addition. The microstructures of the surface layer were characterized by optical microscopy, X-ray diffraction and scanning electron microscopy. The mechanical properties and corrosion resistances of the surface layer were studied by Vickers microhardness measurements and polarization tests in 3.5% NaC l solution. The results showed that RE atoms could diffuse into the surface layer of the steel and inhabit the formation of ε-Fe_(2–3)(N,C) phase. As compared to the treatment without RE addition, RE addition further increased the surface hardness by 143 HV0.1, and further increased the thickness of the nitrocarburized layer by 39 μm. Compared with the quenched bearing steel, the corrosion resistance of the samples nitrocarburized with and without RE addition could be significantly improved. Especially, the sample plasma nitrocarburized with RE addition exhibited the highest corrosion resistance.     

Study on transport of Dy(Ⅲ) by dispersion supported liquid membrane

The transport of Dy(Ⅲ) through a dispersion supported liquid membrane (DSLM) consisting of polyvinylidene fluoride mem-brane (PVDF) as the liquid membrane support and dispersion solution including HC1 solution as the stripping solution and 2-ethyl hexyl phosphonic aeid-mono-2-ethyl hexyl ester (PC-88A) dissolved in kerosene as the membrane solution, was studied. The effects of pH value, initial concentration of Dy(Ⅲ) and different ionic strength in the feed phase, volume ratio of membrane solution and stripping solution, con-centration of HC1 solution, concentration of carder, different stripping agents in the dispersion phase on transport of Dy(Ⅲ) were also inves-tigated, respectively. As a result, when the concentration of HCI solution was 4.0 mol/L, concentration of PC-88A was 0.10 mol/L, and vol-ume ratio of membrane solution and stripping solution was 40:20 in the dispersion phase, and pH value was 5.0 in the feed phase, the trans-port effect of Dy(Ⅲ) was the best. Ionic strength had no obvious effect on transport of Dy(Ⅲ). Under the optimum condition studied, when initial concentration of Dy(Ⅲ) was 0.8×10-4 mol/L, the transport rate of Dy(Ⅲ) was up to 96.2% during the transport time of 95 min. The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry. The diffusion coefficient of Dy(Ⅲ) in the membrane and the thickness of diffusion layer between feed phase and membrane phase were obtained and the values were 1.99×10-7 m2/s and 15.97 μm, respectively. The results were in good agreement with experimental results.     

Calorimetric Studies of the Synergistic Effect: The Reaction of RE(TTA)_3 with N503 in Toluene

Titration calorimetry has been used to study the thermodynamics of reaction in toluene solution of2-thenoyltriflueroacetone(TTA)complexes of rare earths(RE=Y,Nd,Eu,Yb)with N,Ndimethylheptyl-acetamide(N503)at 298.15 K.The heat of the reaction was determined with a TRONACModel 1250 automatic isoperibol calorimeter.The data and figures of titration curve were recorded by the com-puter automatically.An iterative technique of least-square analysis was used to calculate the equilibrium con-stants and the thermodynamic functions including the entropy and free energy changes,minimizing the errorsquare sum by a computer program.     

Stabilities,mechanical and thermodynamic properties of Al-RE intermetallics:A first-principles study

Stabilities,mechanical and thermodynamic properties of 87 intermetallics in Al-RE binary system were studied by first-principles based on density functional theory(DFT).The results show that the calculated stabilities at T=0 K are in good agreement with experimental values.Al2 RE intermetallics exhibit the best stability in Al-RE binary compounds;and the stabilities in descending order are Al2 RE,Al3 RE,AlRE,Al11RE₃,AlRE2 and AlRE₃.The calculated Al-RE intermetallics possess mechanical stabilities.The hardness and strength of the most Al-RE intermetallics are greater than pure aluminum except AlCe,AlPr,AlEu and AlYb.The hardness and strength in descending order are Al11RE₃,Al3 RE,Al2 RE and AIRE.Part of AlRE intermetallics exhibit ductility;the others are brittle.The heat capacities of Al-RE intermetallics in ascending order are Al-Sc,Al-Y,Al-lanthanides.On the contrary,the coefficient of thermal expansion(CTE)in ascending order is Al-lanthanides,Al-Y and Al-Sc.     

Stabilities,mechanical and thermodynamic properties of Al-RE intermetallics:A first-principles study

Stabilities,mechanical and thermodynamic properties of 87 intermetallics in Al-RE binary system were studied by first-principles based on density functional theory(DFT).The results show that the calculated stabilities at T=0 K are in good agreement with experimental values.Al2 RE intermetallics exhibit the best stability in Al-RE binary compounds;and the stabilities in descending order are Al2 RE,Al3 RE,AlRE,Al11RE₃,AlRE2 and AlRE₃.The calculated Al-RE intermetallics possess mechanical stabilities.The hardness and strength of the most Al-RE intermetallics are greater than pure aluminum except AlCe,AlPr,AlEu and AlYb.The hardness and strength in descending order are Al11RE₃,Al3 RE,Al2 RE and AIRE.Part of AlRE intermetallics exhibit ductility;the others are brittle.The heat capacities of Al-RE intermetallics in ascending order are Al-Sc,Al-Y,Al-lanthanides.On the contrary,the coefficient of thermal expansion(CTE)in ascending order is Al-lanthanides,Al-Y and Al-Sc.     

Magnetic susceptibility of Al2RE compounds in crystal and liquid states

Magnetic susceptibility of Al2RE (RE=Y, Ce, Sm, Gd, Dy, Ho, Yb) compounds was studied experimentally in wide temperature (T=290-2000 K) and field (B=0.3-1.3 T) intervals. The abnormal increase in susceptibility beginning above the melting point was fixed for all the compositions. The values for the effective magnetic moments per RE atoms in these compounds were found to be smaller than the values typical for free ions RE3+. The results were discussed in supposition of the directed bonds between aluminum and rare-earth atoms.     

Effect of rare earth oxides on the morphology of carbides in hardfacing metal of high chromium cast iron

The flux cored wires with different amounts of rare earth (RE) oxides additions for hardfacing (harden-face-welding) the workpieces of high chromium cast iron were studied in this work.The morphology of carbides in hardfacing metal was observed,and the type of the carbides was determined by optical microscopy,scanning electron microscopy (SEM),energy dispersive spectrometer (EDS) and X-ray diffraction (XRD).Based on the data of effect of RE on carbides morphology,the refined reason for carbide by RE oxide was discussed with the misfit theory.The results showed that,the microstructure of hardfacing metal was composed of martensite,residual austenite and M7C3 carbides.With the increasing amount of RE oxide additions,the volume fraction and roundness of the carbides were increased,however,the area and perimeter of carbides were decreased.It indicated that carbides in hardfacing metal could be refined and spheroidized by adding RE oxides in flux cored wires.