Imports & Exports Review of Chinese RareEarths(continued)

Since 2001, China kept its position of the largest producing country of rare earth rnagnets in the world and worked on further in the global market. China exported 7,709 tons of rare earth magnets and earned foreign currency ofUSS 214 million in 2004, increasing 37.2% and 33.0% over the same period of 2003 respectivety. In 2005, China exported 8.756 tons of RE magnets and earned foreign currency of USSZ39 million, up 13.9% and 11.4% over 2004 respectively.

Fluorescence and preparation of Sr_2(P_2O_7 ):Ce,Tb phosphate by co-precipitation method

The micron-sized Sr2（P2OT）：Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of （NH4）2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, trans-mission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 ℃ is Sr2（P2O7）：Ce,Tb, which belongs to ortho-rhombic phase. The powder is spherical and the size dis-tribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0：0.4：0.6 shows the best fluores-cence effect annealed at 1,100 ℃ for 3 h. The phosphors produce green fluorescence by being excitated with ultra-violet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr2（P2O7）：Ce,Tb phos-phors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.

Effects of lanthanum on properties of cathode materials and ion implanted spinning rings

The effects of rare earth elements on the structure of cathode materials composed of WC, 663Cu and Ti as well as the performances of spinning rings implanted with this cathode materials were investigated. The results show that rare earth elements can improve the microstructure and compactness of the cathode materials, and elevate the wear resistance and corrosion resistance of spinning rings implanted with these materials. Consequently, the yarn quality is improved significantly.

EFFECTS OF RARE EARTH MIXTURE ON MECHANICAL PROPERTIES OF CuZnAl SHAPE MEMORY ALLOYS

With thehelpofquantitative metallograph ,tensiletest,electron probeandscan electron mi croscope,theinfluencesof mixture rareearth ( RE) on the grain size, dynamics of grain growth and mechanicalpropertiesof CuZnAlshape memoryalloys wereinvestigated . Theex perimentalresultsshowsthat REcanrefinegrainsgreatly,improvethe mechanicalpropertiesremarkably andchangethetensilefracturefrom brittletypebordered grainstoplastictypeinthecondition of maintainingshape memory properties. Moreover microstructuresrevealthatREwhich accumulates on the grain boundariescan restrain grains’growing. In addition, the mechanismsofrefininggrainsizeandimproving mechanicalpropertiesarealsodiscussed.

LASTER SURFACE CLADDING BY Co BASE ALLOY WITH Ce ON 20 # STEEL PERFORMANCE AND MICROSTURCTURE STUDYS

Onthebase of 20 # steel, Co base alloy with Ce and without Ce was obtained with laser heatingtechnology. Theresultshowsthat Cehasobviouslyeffecton alloy microstructureespe ciallyimprovethecorrosion resistancein acid by31 % ,oxygenation resistanceby23 % ,in al kalescent liquid by 23 % . Improve fearlessness 30% and improve hardness by 168 HV.Throughcontrast and analysison the Co base microstructure with Ce and without Ce . The paper discussthetheory of Ce modification Co base alloy from theside of cooling thermody namicsand dynamics

Giant low-field reversible magnetocaloric effect at liquid helium temperature of niobium and iron co-substituted EuTiO_(3) compounds

Giant magnetocaloric effect(MCE)materials in the liquid helium temperature region have attracted a lot of attention in the field of low-temperature magnetic refrigeration(MR).In this study,a series of niobium(Nb)and iron(Fe)co-substituted EuTiO_(3) perovskites with cubic structure(space group pm3m)was successfully fabricated,and their magnetic properties as well as cryogenic magnetocaloric effects were investigated in detail.As expected,the introduction of Nb and Fe can significantly modulate the magnetic phase transition and magnetocaloric effect of the EuTiO_(3) compounds.With increasing Fe concentration,two local minima corresponding to the AFM-FM magnetic phase transition near 5.0 K and FM-PM transition near 10 K with no hysteresis in the thermomagnetic curves are observed,which is attributed to an enhancement of FM coupling.At the same time,the gradually widened-ΔSM-T curves and the two peaks with a broad shoulder lead to considerable refrigeration capacity(RC).With the field change ofΔH=2 T,the calculated values of-ΔS_(M)^(max) for the EuTi_(0.9375-x)Nb_(0.0625)Fe_(x)O_(3)(x=0.075,0.1,0.125,0.15)compounds are 24.2,17.6,14.5 and 14.0 J/(kg·K),respectively.The corresponding RC values were calculated to be 144.6,138.3,151.2 and 159 J/kg,respectively.Especially,the values of-ΔS_(M)^(max) for EuTi_(0.8625)Nb_(0.0625)Fe_(0.075)O_(3) are 8.6 and 15.1 J/(kg·K)under low field changes of 0.5 and 1 T,respectively.The giant low-field reversible magnetocaloric effect makes them attractive candidates for magnetic refrigeration in the liquid helium temperature region.

Direct observation of oxygen vacancy formation and migration over ceria surface by in situ environmental transmission electron microscopy

The extremely high structural tolerance of ceria to oxygen vacancies(Ov)has made it a desirable catalytic material for the hydrocarbon oxidation to chemicals and pharmaceuticals and the reduction of gaseous pollutants.It is proposed that the formation and diffusion of Ov originate from its outstanding reduction property.However,the formation and diffusion process of Ov over the surface of ceria at the atomic level is still unknown.Herein,the structural and valence evolution of CeO_(2)(111)surfaces in reductive,oxidative and vacuum environments from room temperature up to 700℃was studied with in situ aberration-corrected environmental transmission electron microscopy(ETEM)experiments.Ov is found to form under a high vacuum at elevated temperatures;however,the surface can recover to the initial state through the adsorption of oxygen atoms in an oxygen-contained environment.Furthermore,in hydrogen environment,the step-CeO_(2)(111)surface is not stable at elevated temperatures;thus,the steps tend to be eliminated with increasing temperature.Combined with first-principles density function calculations(DFT),it is proposed that O-terminated surfaces would develop in a hypoxic environment due to the dynamic diffusion of Ov from the outer surface to the subsurface.Furthermore,in a reductive environment,H2 facilitates the formation and diffusion of Ov while Ce-terminated surfaces develope.These results reveal dynamic atomic-scale interplay between the nanoceria surface and gas,thereby providing fundamental insights into the Ov-dependent reaction of nano-CeO_(2) during catalytic processes.

Microwave-assisted fast synthesis and red-emitting properties of a borotellurate-based phosphor with excellent thermostability

At present,with the increasing application needs of phosphor-converted white light-emitting diode(wLED),the synthetic efficiency and thermal stability of phosphor become urgent problems.Herein,this research reports a microwave-assisted fast synthesis approach to obtain a Sm^(3+)-activated borotellurate Na_(2)Y_(2)TeO_(4)(BO_(3))_(2)(NYTB)red phosphor with high crystallinity,excellent thermostability,and low chromaticity shift.For the NYTB-based phosphor,in contrast to the conventional solid-state synthesis,the microwave-assisted synthesis method involves lower synthesis temperature and shorter processing time.Additionally,the concentration quenching mechanism was determined.The w-LED device packaged with the studied phosphor exhibits a near-standard white light with proper CCT and high Ra parameters.

Tuning interaction strength between CeO_(2) and iridium to promote CO oxidation over Ir/TiO_(2)

The interaction between support and noble metal plays a crucial role in heterogeneous catalysis design.However,how to tune metal support interactions to optimize the activity still needs further exploration.CeO_(2) was introduced to promote CO oxidation ove r Ir/TiO_(2) by adjusting the interaction strength between iridium(Ir)and CeO_(2).The strong interaction between Ir and CeO_(2) blocks CO adsorption and causes low CO oxidation activity.However,introducing CeO_(2) on Ir/TiO_(2) produces localized interaction between Ir and CeO_(2),which can tune the surface electronic state of Ir,so a"volcano curve"relationship between CO oxidation activity and electronic state is built.Limited amount of CeO_(2) on Ir/TiO_(2)(Ir/Ce_(0.2)Ti)leads to CO complete oxidization at 22℃,and a new pathway for CO oxidation was explored.The study demonstrates that the utilization of tuning interaction strength between active metal and support is a potential method to increase the catalytic activity.

LaMnO_(3)/Co_(3)O_(4) nanocomposite for enhanced triethylamine sensing properties

LaMnO_(3) modified Co_(3)O_(4) nanocomposites were prepared by simple hydrothermal method co mbined with sol-gel method.The gas sensitivity properties of pure Co_(3)O_(4) and LaMnO_(3)/Co_(3)O_(4) with different composite proportions are compared.It is found that 0.6-LMO/Co_(3)O_(4) sensor has higher sensitivity to triethylamine(TEA)than pure Co_(3)O_(4) sensor,which is improved by 9.27 times.And the working temperature is reduced from 150 to 130℃.Besides,it has excellent gas selectivity and repeatability.The improvement of the gas sensitivity of LaMnO_(3)/Co_(3)O_(4) sensor may be due to the fact that LaMnO_(3) is an effective catalyst,and the catalytic performance perhaps is beneficial to improving the sensing performance.In addition,the formation of p-p heterojunctions may be the key factor to improve the gas sensing performance.This work provides a new Co_(3)O_(4)-based gas sensing material for the detection of TEA.

Superior comprehensive properties of LaFe_(11.8)Si_(1.2)/Ce_(60)Co_(40) magnetocaloric composites

LaFe_(11.8)Si_(1.2)/10 wt%Ce_(60)Co_(40) composites were prepared by spark plasma sintering and subsequent diffusion annealing.A novel core-shell structure is observed with the LaFe11.8Si1.2 particles as the core and the(La,Ce)_(2)(Fe,Co,Si)_(17)(2:17)phase as the shell.As diffusion annealing time(t_(a))increases,this core-shell structure is replaced by the formation of the(La,Ce)_(1)(Fe,Co,Si)_(13) phase.Annealing at 1323 K for 12 h results in samples with(-ΔSM)^(max) of 9.30 J/(kg·K)(Δμ0H=2 T),good mechanical properties((σbc)^(max)=402 MPa,ε=4.21%)and thermal conductivity of 8.7 W/(m·K).Thus,bulk composites with excellent comprehensive properties for magnetic refrigeration are obtained in this work.

Effect of different doping elements on performance of Ce-Mn/TiO_(2)catalyst for low temperature denitration

Sm and Ho were doped in Ce-Mn/TiO_(2)catalyst respectively to enhance its denitration performance at low temperature.X-ray diffraction(XRD),N2adsorption-desorption,X-ray photoelectron spectroscopy(XPS),NH3-temperature programmed desorption(NH3-TPD),H2-temperature programmed reduction(H2-TPR)and in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)techniques were used to analyze the structure and performance of catalysts.The results demonstrate that Ho doping increases the amount of acid sites and improves low temperature redox property of Ce-Mn/TiO_(2),which lead to excellent DeNOxperformance of Ho-Ce-Mn/TiO_(2)in the whole reaction temperature range.Sm doping results in decline of redox property,but it is beneficial to increasing the acid sites of Ce-Mn/TiO_(2).The increased surface acid sites and moderate oxidative ability impart Sm-Ce-Mn/TiO_(2)higher denitration activity and N2selectivity at temperature above 150℃.Lewis acid sites and redox property are the main factors affecting the activity of catalysts.Doping of Ho and Sm both improves sulfur resistance performance of Ce-Mn/TiO_(2)by inhibiting the adsorption of SO_(2)and formation of sulfate.Ce-Mn/TiO_(2)modified by Ho shows better sulfur resistance than that doped with Sm because of its more surface acid sites.

A novel blue-light excitable Pr^(3+)doped(Sr,Ba)LaMgTaO6 phosphor for plant growth lighting

In this work,a series of Pr^(3+)ions doped(Sr,Ba)LaMgTaO_(6)phosphors were prepared and applied for plant growth lighting.Under 450 nm excitation,(Sr,Ba)LaMgTaO_(6):Pr^(3+)exhibits intense reddish emission at around 650 nm which is assigned to the3p0→3F2transition of Pr^(3+)ions.The luminescence intensity reaches to the maximum at 2.5 mol%Pr^(3+)doping content both in SrLaMgTaO_(6):Pr^(3+)and BaLaMgTaO_(6):Pr^(3+)systems.Meanwhile,the internal quantum efficiency(IQE)test shows that the IQE of the SrLaMgTaO_(6):0.025Pr^(3+)phosphor is 33.34%upon blue light excitation.The decay curves and temperature-dependent luminescence measurements of the(Sr,Ba)LaMgTaO_(6):Pr^(3+)phosphors were performed and investigated in detail.The red light emitting diodes(LEDs)were packaged using the SrLaMgTaO_(6):Pr^(3+)and BaLaMgTaO_(6):Pr^(3+)phosphors combined with a blue LED chip,which are welloverlapped with the absorption band of photosynthesis.Results indicate that the(Sr,Ba)LaMgTaO_(6):Pr^(3+)can serve as a component of the red light in plant-growth LEDs.

CeO_(2)-clay composites for ultra-long cycle life electrochemical capacitive energy storage application

The lattice expansion caused by the reduction of Ce(Ⅳ)to Ce(Ⅲ)impeded the development of the CeO_(2)as an effective electrode material for electrochemical supercapacitors.Herein,we prepared CeO_(2)-clay composites through a one-step hydrothermal method.The interlayer structures of clays efficiently accommodate volume changes induced by crystal lattice expansion to achieve ultra-long cycle stability.After 60000 charge-discharge cycles,the capacitance retention rate of the assembled asymmetric supercapacitors is as high as~-100%.The key findings of this work reveal the potential application of clays in achieving ultralong cycle stability of the CeO_(2)electrode material,paving the way for further application of the CeO_(2)in electrochemical energy storage.

Enhancement mechanism of maximum energy product in hot-deformed Nd-Fe-B magnets by addition of ferromagnetic substances

It has been proved that the maximum magnetic energy product(BH)maxof hot-deformed Nd-Fe-B magnets can be effectively improved by adding substances with either high melting point or high saturation magnetization.In this work,we selected a ferromagnetic nano Fe_(55)Ni_(28)Co_(17) alloy powders with both high melting point and high saturation magnetization as the dopant to improve the(BH)max.By the addition of 1 wt% FeNiCo,the remanence increases by over 5%(from 1.36 to 1.44 T),resulting in a significant enhancement of(BH)maxfrom 355 to 396 kJ/m^(3)(from 44.6 to 49.7 MGOe).Microstructure observations reveal that the texture of grain alignment is improved,the concentrations of ferro magnetic elements(Fe,Ni,and Co) in the main phase and intergranular phase are increased so that the magnetization behavior of hot-deformed magnet changes(more easily shows reversible magnetization behaviors),which are the reasons why the high maximum energy product of hot-deformed magnet,is obtained.

Agglomeration behavior of rare earth inclusions and alumina inclusions at the interface between argon and molten steel

Nozzle clogging frequently occurs in steel containing rare earth(RE) due to the aggregation of RE inclusions,which seriously interferes with the application of RE in steel.To provide insights into nozzle clogging,the agglomeration be havior of inclusions in RE-containing steel was investigated by laboratory experiments and theoretical calculations.High-temperature confocal laser scanning microscopy(HTCLSM) was applied to observe the behavior of inclusions at molten steel surfaces and their interactive forces.Kralchevsky-Paunov(K-P) model was used to predict the capillary force acting on different inclusions.The results show that the interactive forces that acted on inclusions were investigated as a function of inclusion size,inter-distance,and inclusion composition.It is found that the capillary force acting on the inclusions decreases in the order of Ce_(2)O_(3)> CeAlO_(3)> Al_(2)O_(3).This study verified the applicability of the K-P model in RE-containing steel,which can provide theoretical support to help solve the nozzle clogging problem during rare earth steel production.

Preparation of Eu^(2+),Dy^(3+),Zr^(4+)ions co-doped strontium aluminate/molybdate multi-optical functional hybrid pigments for anti-counterfeiting

Eu^(2+),Dy^(3+)and Zr_(4+)ions co-doped strontium aluminate(i.e.,SrAl_(2)O_(4):Eu^(2+),Dy^(3+),Zr_(4+))/molybdate(i.e.,Ho2MoO6or Nd2MoO6)with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing.The phosphor and hybrid pigments were characterized by X-ray diffraction,scanning electron microscopy with energy dispersive X-ray spectroscopy,ultraviolet-visible spectroscopy,L*a*b*color scale analysis,spectrophotometry and mechanoluminescent measurement.The results show that the optimum luminescent emission intensity of SrAl_(2)O_(4):Eu^(2+),Dy^(3+),Zr_(4+)phosphor can be obtained when 5 mol%Zr_(4+)ions is doped into the lattice.Under the excitation of 365 nm wavelength,the hybrid pigments prepared with the phosphor and molybdate at a mass ratio of 1:1 present a green broad band emission located at 460-650 nm due to 4f65d1→4f7transitions of Eu^(2+)ions.The hybrid pigments have the superior mechanoluminescent property and emit light after being exerted by mechanical stresses.Besides,the hybrid pigments also exhibit an allochroic effect under different illuminants.In addition,the anti-counterfeiting of the hybrid pigments as a promising application was also presented.

Electroextraction of neodymium from LiCl-KCl melt using binary liquid Ga-Al cathode

The electrochemical behaviour of Nd(Ⅲ)ion was investigated on inert W,active Ga and Ga-AI cathodes.It is established that the reduction of Nd(Ⅲ)ion on the inert electrode is a consecutive two-step process while that on the active electrodes is a one-step process.The apparent standard potential of the Nd(Ⅲ)/Nd redox couple at different temperatures was determined by open-circuit chronopotentiometry and semi-differential method,and the relationship between temperature and apparent standard potential was further discussed.The thermodynamic properties of Nd in Ga and Ga-Al electrodes such as activity coefficient and activity were evaluated via intermittent coulomb titration and temperature dependence test,and the effect of temperature on activity coefficient was verified.Finally,Nd was successfully extracted in form of alloy from molten salt by galvanostatic electrolysis,in which the current efficiency of91.7%for the electroextraction indicates that the binary liquid Ga-Al electrode has favorable performance.

Ferroelectricity induced by non-symmetry of A-site cations in hexagonal antiferromagnetic In_(1-x)Yb_(x)FeO_(3)(x=0.1,0.2,0.3) perovskites

A new series of multiferroic In_(1-x)Yb_(x)FeO_(3)(x=0.1,0.2,0.3) compounds were prepared using the traditional synthesis method for the first time.Partially substituting In ions in InFeO3with Yb ions results in the weak ferroelectricity of the compound.A dielectric relaxation peak is found at ~500 K in the temperature dependence of the dielectric properties of the resulted compounds.The dielectric constant of In_(0.8)Yb_(0.2)FeO_(3)displays an anomaly at -500 K,and the ferroelectric hysteresis loop reveals its weak ferroelectric behaviors below this temperature.Similarly to InFeO_(3),the compounds crystallize in space group P63/mmc.The increase in the Yb content leads to an increment in a and a reduction in c parameters.The temperature dependence of magnetization for In_(0.8)Yb_(0.2)FeO_(3)gives a Néel temperature of -150 K.The hysteresis loops at 10 and 100 K indicate its weak ferromagnetic characteristics above room temperature.Thus,In_(1-x)Yb_(x)FeO_(3)(x=0.1,0.2,0.3) compounds show both weak ferroelectricity and weak ferromagnetism.The non-symmetry of Yb cations causes the ferroelectricity of the compounds.

Illuminating the negative thermal expansion mechanism of YFe(CN)_(6)via electronic structure and unusual phonon modes

Understanding the negative thermal expansion(NTE)mechanism remains an important and challenging thing.In this work,we selected the case of YFe(CN)_(6)to investigate the structure-mechanism relation on the base of crystal structure,electro nic structure and lattice dynamics.We expanded the NTE of YFe(CN)_(6)to 150 K,and the temperature dependence of volume and lattice constants was determined by temperature-variable synchrotro n X-ray diffraction measure ments.A large NTE was found in the system.Our theoretical calculations indicate that the Y-N bond exhibits a strong ionic feature through the calculated electron localization function(ELF),which has a strong influence on the anisotropic vibration of the N atom.The detailed lattice dynamics simulations suggest that the NTE of YFe(CN)_(6)may be related to the presence of the unusual low-frequency modes of the YN_(6)triangular prism(tri-prism)units.The optical branches with low frequencies are mainly related to the distortion and twisting modes of the YN_(6)tri-prism units,which contribute most to the NTE effect in the crystal.