Geochemistry of Rare Earth Elements in Hydrothermal Ore Deposit in Heishan Area,Shaanxi Province

The study on rare earth elements in hydrothermal ore deposit in Heishan area indicates that the REE concentration in rock with very weak negative Ce and Eu anomaly is far higher than those in ore. The REE pattern in ore is characterized by very low REE concentration, typical enrichment in LRE and distinctive negative Eu and Ce anomaly. δ Eu and δ Ce values vary from 0 51～0 6 to 0 71～0 77 and 0 84～0 88 to 0 60～0 78, respectively, as shown in samples from Fe Cu ore to Au ore. Different δ Eu and δ Ce values reveal that temperature gradually decreases and oxygen fugacity gradually increases when ore bearing hydrothermal solution evolves from early to late stage. It is likely that REE in solution is mainly transported in the forms of(RE(CO 3) 3F) 4- , (RE(CO 3)F 2) -, (RE(F,Cl) 2) + , (RE(CO 3) 3) 3- and (RE(CO 3) 4) 5- complexes.

Electrodeposition of Rare Earth Metals and Their Alloys in Organic Electrolytes

The electrodeposition of rare earth metals and their alloys in organic electrolytes are reviewed. The solvents, electrolytes and operetating conditions are discussed. It is concluded that exploring the rare earth salt, which can be highly soluble in organic solvents and easily dehydrated, is the key to the pracitical utilization of electrodeposition of rare earth metals and their alloys in organic electrolytes.

Rare Earth-Boronizing and Its Applications

The thickness, brittleness, boron content and morphology of RE boronized layer were investigated. The results show that the service life of the boronized layer in molten zinc can be increased by adding RE element. The thermocouple and sink roll sleeve made of this material can be used for more than half a year.

Complex behaviour of trivalent rare earth elements by humic acids

The complexation behaviours of trivalent rare earth elements (La, Ce, Ho and Yb) by two types of humic acids were investigated under a specified set of conditions. Humic acids show quite different complexation capacities an conditional formation constants with the REEs. Apparently there are two types of binding sites in the functional groups of humic acid, in which the first binding sites have stronger ability than the second. Cerium shows the largest complexation capacities and highest formation constants among the four REEs with two humic acids, this anomaly may be relative to the distribution pattern of the REEs in seawater. The experimental results were comparable to the values of other metals reported and provided the basic data for environmental geochemistry of rare earth elements.

Extraction of Rare Earth from Black Weathering Mud

A black weathering mud containing rare earth in Southwest China contains about 3%～7% RE 2O 3. RE in the weathering mud mainly exists on the amorphous Mn Fe oxide, which can not be enriched by physical beneficiation methods such as floatation, magnetic and electrostatic separation or gravity concentration etc , and can not also be exchanged by salts. Chlorinating roasting is selected to treat the black weathering mud based on the thermodynamic analysis and the properties of mud in the paper. The chlorinating roasting treatment is divided two stages. The first step is to heat the mud mixed NH 4Cl and carbon with (1.5～2.5)∶10 of NH 4Cl/mud ratio at 200℃ for 1 h. NH 4Cl directly chlorinates the RE 2O 3 in the weathering mud, but do not destroy Mn Fe amorphous structure. The secondary stage is to heat the mixture to above 350℃, NH 4Cl decomposes to NH 3 and HCl, and carbon in the mixture also takes part in chlorinating of RE. Recovery of RE reaches to 91.6% under the conditions of temperature 450℃ and roasting for 2 h, and Pb and Mn can be further recovered at the same time.

Effect of Rare Earth Elements on Growth Dynamics of Austenite in 60CrMnMo Steel

The growth dynamics of austenite grains was investigated in 60CrMnMo steel with different RE elements. The results show that austenite grains of 60CrMnMo steel can be refined and their growth can be restrained by adding a certain amount of RE. From the experimental results, the values of n and Q were evaluated.

Effect of Rare Earth Elements on Carbide Morphology and Phase Transformation Dynamics of High Ni-Cr Alloy Cast Iron

The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.

RARE EARTH PARTITIONING OF GRANITOID WEATHERING CRUST IN SOUTHERN CHINA

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Comparison of Economical and Technical Indices on Rare Earth Separation Processes of Bastnasite by Solvent Extraction

According to the composition of rare earth ores and the market, several feasible separation processes of bastnasite in Baotou of Inner Mongolia and Mianning of Sichuan by solvent extraction in HEH(EHP) HCl system were presented. The parameters of the processes such as stage numbers, volume of mixer settler, fixed investment of extractant and rare earths, consumption of chemical reagents including HCl and NH 3 were calculated and compared. The results show that the novel scheme can save cost more than 20% compared with those of others. By the economical analysis, the optimized separation process of bastnasite was obtained, which can be applied to the treatment of monazite too.

Thermal Stability of Rare Earth-Rich Phase in High Temperature Titanium Alloy

The thermal stability of the rare earth rich phase particles in α, α+β and β phase regions of Ti 5Al 4Sn 2Zr 1Mo 0 25Si 1Nd(Ti 55) high temperature titanium alloy heat treated was studied. Under conditions of 600～980 ℃/1～100 h and 1050～1500 ℃/1～10 h, the average particle size ranges from 3 34 to 4 20 μm, the circularity shape factor from 0 619 to 0 759, and the volume fraction from 1 4% to 1 8%. The results show that nearly no change is found for the size, shape, and volume fraction of the particles in the alloy, and the rare earth rich phase particles exhibit thermal stability.

Accelerating Effect of Rare Earth in Steel on Its Surface-Carburizing Process

The carburization of steel type 20 with and without RE addition was investigated. The results show that RE in steel can accelerate carburizing process at 850 and 910 ℃. The optimum RE content in steel is about 0 032%. The mechanism of enhancing effect of RE on carburizing process was discussed.

Effect of Rare Earths on the Wear Resistance and High Temperature Oxidation Resistance of H13 Steel Surface-Treated with S-N-C Co-diffusion

Steel H13 was put in non toxic salt bath with addition of CeO 2 for co diffusion of sulfur, nitrogen and carbon and followed by oxidation treatment. The effect of rare earths on the improvement of wear resistance and high temperature oxidation resistance of steel H13 was studied using scanning electron microscope, energy dispersive spectrometry and X ray diffraction. The results show that compared to the surface treatment without rare earth addition, the treatment with addition of rare earths improves the wear resistance and high temperature resistance to oxidation of steel H13. Under the conditions of 30 N and 2 h, the wear weight loss was decreased by 40%, and the friction coefficient was reduced from 0 25 to 0 22; whereas for 150 N and 0 2 h, the wear weight loss was decreased by 24%, and the friction coefficient was reduced from 0 35 to 0 32. For the oxidation at 700 ℃ and 4 h, the rate of weight gain decreased to only about 1/30 of that without rare earths.

Geochemical characteristics of rare earth elements in Wuhan section of the Yangtze River

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Distribution and Behaviour of Rare Earths in Laser Coating

The behaviour of RE added into steel surface by laser rapid solidification processing(LRSP) and their effects on surface properties were studied. Experimental results show that RE can be added into steel surface layer by LRSP of RE containing coating. The RE in the steel surface can react with oxygen and sulphur, then be dissolved in the grains or grain boundaries, and form intermetallic compounds RE 2Fe 17 . The addition of RE by LRSP has very strong effects on the properties of steel surface.

TUNGSTEN ELECTRODES CONTAINING THREE TYPES OF RARE EARTH OXIDES

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Study on Roast Reaction Kinetics of Baotou Concentrate of Rare Earth with 15% Na_2CO_3 Additions

The research on the mechanism of the roast reaction of Baotou concentrate of rare earth with 15% Na 2CO 3 additions was carried out through thermal, X ray diffraction and chemical analysis. Bastnaesite(RECO 3F) was first decomposed into REOF at 623～741 K, then Monazite(REPO 4) reacted with Na 2CO 3 was decomposed into RE 2O 3 and produced Ca 8Nd 2(PO 4) 6O 2 at 853～928 K. The kinetics parameters of the roast reaction were calculated. The results of the calculation were as follows: at 623～741 K, E =152 kJ·mol -1 , n =0 77, A =1 11×10 12 s -1 ·mol -1 , k =1 102( T =705 K), and at 853～928 K, E =232 kJ·mol -1 , n =1 16, A =1 11×10 9 s -1 ·mol -1 , k =1 07×10 -4 ( T =915 K). The equation of the mechanism of the roast reaction is F 1=-ln(1- α ) at 623～741 K and 853～928 K according to TG curves.

Photophysical Properties of Rare Earth Complexes with 3,4-Furandicarboxylic Acid and 1,10-Phenanthroline

Synthesis, IR spectra, UV vis spectra and photophysical properties of Gd 3+ , Eu 3+ , Tb 3+ complexes with 3,4 furandicarboxylic acid and 1,10 phenanthroline are reported. Intramolecular energy transfer process for these complexes is discussed in detail. It is found that the intramolecular energy transfer efficiency depends on the relative positions between the resonance energy levels of the central rare earth ions and the lowest triplet state energies of ligands.

Preparation and Structural Chemistry of a Series of Rare Earth Compounds REPS_4

The thiophosphates of the rare earths REPS 4(RE=Y, La～Lu) were prepared by solid state reaction. Their unit cell parameters and the structures of HoPS 4, ErPS 4 and TmPS 4 were determined by X ray powder diffraction. All REPS 4(RE=Y, La～Yb) crystallize in the tetragonal space group I4 1/acd , a ≈1 1 nm, c ≈1 9 nm, Z =16 . Each RE 3+ is surrounded by eight sulfurs and thus forms a distorted tetragonal antiprism. This kind of structures has significant Van Der Waals′ vacant space with a diameter of about 0 625 nm along c axis and of 0 35 nm along a and b axis. But LuPS 4 crystallizes in a monoclinic structure which is most probably layered. The influence of lanthanide contraction on the stability of the tetragonal REAX 4 structure was studied and a criterion for the existence of the tetragonal structure in the REAX 4 series compounds is proposed. There is 2 4 d A X / r 1 9.

Phenomena of Periodic Precipitaion in Rare Earth-Cholate Diffusion Systems

The precipitate patterns were studied in rare earthcholate diffusion systems. The corresponding precipitates were characterized by Forie Transformed Infrared(FTIR) and Extended XRay Absorption Fine Structure(EXAFS) spectroscopy. The experimental results indicate that rare earth ions tend to produce periodic precipitation, and the pattern precipitates are just the corresponding rare earth cholate complexes.

Geochemical Characteristics of Rare Earth Elements in Different Types of Soils in China

The contents, distribution patterns, and specification of rare earth elements(REEs) in latosol(tropical zone), red earth(middle subtropical earth), yellow brown soil(northern subtropical earth), cinnamon soil(warm temperate zone), leached chernozem(temperate zone) and albic bleached soil(temperate zone) in China were determined with instrumental neutron activation analysis(NAA) and systematically studied. The results indicate that yellow brown soil, cinnamon soil, leached chernozem and albic bleached soil are characterized by light REEs(LREEs) enrichment and Eudepletion, while latosol and red earth are characterized by LREEs enrichment and Cedepletion. REEs exist mainly in a stable residual form in the six soils, and with increasing atomic number, the intermediate REEs(IREEs) of residual form have lower proportion than light and heavy REEs. For the six unstable forms, the proportions of watersoluble, exchangeable, specific absorption, and carbonate forms are lower. Appearent zonal distribution patterns of REEs were found in the form of FeMn oxides in different types of soils, and the general trend gradually decreases from southern to northern China. Proportions of REEs in bound organic matters are higher and follow the order: albic bleached soil>leached chernozem>red earth>latosol>yellow brown soil>cinnamon soil. Higher proportion of REEs exists in soils with higher proportion of organic matters. But their activation differs greatly with difference in relative proportions of loosely bound organic matter form and tightly bound organic matter form.