Development Status and Research Progress in Rare Earth Hydrometallurgy in China

Characteristic and hydrometallurgy processes for Baotou mixed-type rare earth concentrate, bastnasite, and ionic adsorption deposit in China were reviewed. The R ＆ D circumstance and new progresses in extraction and separation of RE element in China were introduced. Moreover, the development trend of RE hydrometallurgy was predicted. The direction and emphasised fields of research and development are also brought forward as： to R ＆ D high efficient green progresses in hydrometallurgy and separation of RE ore, resolve the waste pollution problem of water, slagand gas, reduce the chemical material consumption and improve comprehensive efficiency of resources; to R ＆ D preparation technology for RE compounds with ultra high-purity and special physical property for extending application fields of RE.

Development of Rare Earth Hydrometallurgy Technology in China

In this paper, the recent advance of processes for treating Baotou mixed-type rare earths concentrate, bastnasite, and ionic adsorption deposit in China was reviewed. The R & D circumstance and new progresses in separation and purification of individual and high purity RE compounds in China were introduced. Moreover, the development of RE hydrometallurgy was also predicted. So we suggest to enhance the research and development of products applying RE, especially Ce, Y, Gd, Sm etc., for keeping RE consumption equilibrium and extending applications, to increase enterprise's automatic control level for improving the stability and the consistency of the products, and to pay more attention to protection of environment.

Hydrogen storage properties of Zr_(1-x)Ti_xCo intermetallic compound

The intermetallic compound Zr1-xTixCo was prepared and its suitability for hydrogen storage was investigated. The alloys obtained by magnetic levitation melting with the composition of Zr1-xTixCo (x=0, 0.1, 0.2 and 0.3, at.%) show single cubic phase by X-ray diffraction. A single sloping plateau was observed on each isothermal, and pressure-composition-temperature (PCT) measurement results show that the equilibrium hydrogen desorption pressure of Zr1-xTixCo alloy increases with increasing Ti content. The desorption temperatures for supplying 100 kPa hydrogen are about 665, 642, 621 and 614 K for ZrCo, Zr0.9Ti0.1Co, Zr0.8Ti0.2Co and Zr0.7Ti0.3Co alloy, respectively. Repeated hydrogen absorption and desorption cycles do not generate separated ZrCo, TiCo and ZrH2 phases, indicating that alloys have good thermal and hydrogen stabilization.

Influence of Metal Additives on the Electrical Conductivities of the Oxide Ceramics as an Electrode Material

The electrical conductivities are reported for various oxide ceramics and cermets at 1000°C.Adding metal can greatly enhance the electrical condnctivities of the oxide materials.The conductivity of the ceramic added with metal depends on:(1)the conductivity σ_o of the oxides;(2)the content of metal additives;(3)the dispersion of the metal phase among oxide phase.The conductivity of the metal added does not affect the con- ductivity of the metal-containing ceramic.Although the metal-containing ceramic has much higher conductivi- ty than oxide ceramic,the change rate of their conductivities with temperature is similar and is controlled by E_g of the oxide.

Research on flow stress of spray formed 70Si30Al alloy under hot compression deformation

The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble- 1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation temperature. The flow stress increases with an increase in strain rate at a given deformation temperature. The flow stress decreases with the deformation temperature increasing at a given strain rate. The relational expression among the flow stress, the swain rate, and the deformation temperature satisfies the Arrhenius equation. The deformation activation energy of 70Si30Al alloy during hot deformation is 866.27 kJ/mol from the Arrhenius equation.

Research on Development of Dolomite-Ferrosilicon Thermal Reduction Process of Magnesium Production

Up to now, the Pedgion magnesium reduction process is the dominating magnesium production process. In 2004, about 98% of raw magnesium is produced by Pedgion magnesium reduction process in China which equals to 60% of the global output. It shows that the dolomite-ferrosilicon thermal reduction process is the most important method to produce magnesium in the world. Limited by the disadvantage of dolomite-ferrosilicon thermal reduction process, the magnesium producing process always followed by relatively severe pollution, while the resource utilizing efficiency keeps very low. With the rapid development of dolomite-ferrosilicon thermal reduction process in China, many research works have been done aiming at the process technology and the reduction theory, and the magnesium producing process has got great evolution. The history of dolomite-ferrosilicon thermal reduction process was introduced; the process character, the merits and which defects were also discussed. Defects in dolomite-ferrosilicon thermal reduction process were expatiated, and feasible method and idea to upgrade the process was put forward. The main problems and the potential troubles hindering the development of magnesium industry were analyzed. Finally, the probability to further improve the thermal reduction process and the effective approaches to develop Chinese magnesium industry were discussed.

Effect of Adding Extruded Mg-Mischmetal Intermediate Alloy on Microstructure and Properties of Die-Casting Magnesium Alloy AZ91D

The preparation techniques of Mg-mischmetal intermediate alloy and the effects of the mischmetal addition ranging from 0.45% to 1.04% on the microstructure and properties of AZ91D alloy prepared by die casting were investigated. The Mg-MM intermediate alloy was prepared by permanent mold casting and then was extruded into the bars. The microstructure and analytical studies were carried out using optical microscopy and differential scanning calorimetry (DSC). Testing results shows the Mg-MM intermediate alloy could melt easily down at die casting temperature of 680 ℃ that was lower than the melting point of lanthanum (918 ℃) and that of cerium (798 ℃). This was propitious to protection the alloy from the oxidation at high temperatures. Then magnesium alloy test bars were produced under conventional cold chamber die casting condition with addition of different weight of the Mg-MM intermediate alloy. Observation and analysis indicated that the microstructures of the alloy were refined and RE containing Al phase was formed with increasing RE addition. The data obtained by tensile tests showed that alloying with mischmetal improved the tensile property of the AZ91D magnesium die casting alloy at ambient temperature.

Preparation of Giant Mangetostrictive Sintered Compacts by Powder Metallurgy

Powder metallurgy technique was applied to prepare rare earth giant magnetostrictive materials. This preparation process consists of casted Tb0.30Dy0.70 Fe1.80 alloy, in magnetic atmosphere. which is pulverized by ball mill, aligned field, compacted and sintered in inertial The experimental results indicate that when the magnetic field is 240 kA ·m^-1, the sample with particle size less than 0. 147 mm being compacted in magnetic field exhibits 1613 × 10^-3 magnetostriction under a compressive pre-stress 8.0 MPa after being sintered at 1200 ℃ for 2 h and annealed at 950 ℃ for 24 h.

Site occupations and ordering behaviour of O phase in Ti_2AlNb-based intermetallics

The site occupations of the alloying elements of O phase in Ti 2AlNb based intermetallics are clarified. The ordering behaviours of the O phase in Ti y Al z Nb( y ≥ 25%, mole fraction) orthorhombic alloys are also investigated with a Bragg Williams model. In the temperature range where the O phases exist, the order parameters change with the alloy composition and temperature continuously, and the first order transition character is very "

Investigation of Interfaces in Remelted A356-SiC Particulate Duralcan Metal Matrix Composite

For the manufacture of Al-based metalmatrix composites, the foundry productionroute can provide less expensive products witha greater flexibility in meeting designer’s needsamong a vaviety of fablication routes. Recent-ly, a commercially produced foundry ingot,the Duralcan composite of A356 Al alloy +20

Break-up Process of Perturbed Molten Metal Jet and Preparation of Lead-Free Solder Balls

Solder balls, which are used in advanced electronics packages such as BGA (Ball Grid Array) and CSP (Chip Scale Package) to substitute the leads and realize the electrical and mechanical connections between substrate and chip,have severe specifications in diameter tolerance, roundness and surface quality, and therefore challenge the traditional technologies for fabrication of metallic particles and powders. The present work made a survey of perturbed molten metal jet break-up process, observed the formation and growth of capillary wave of tin-lead melt jet by way of rapid solidification, and on the basis of the above research, successfully obtained tin-lead eutectic and Sn-4.0Ag-0.5Cu lead free solder balls with tight distribution and good sphericity of particles through optimization of processing parameters, forming a solid base for cost effectively producing solder balls.

Research on fabricating technique of Ba-Al-S:Eu sputtering target

Ba-Al-S-Eu sputtering target for blue emitting phosphors was prepared by powder sintering method. XRD patterns showed that the main components of the target were barium tetra aluminum sulfide （BaAl4S7）, bariutm sulfide （BaS）, and europium sulfide （EuS）. In the samples, part of the barium and aluminum are formed into barium aluminum oxide （BaAl2O4） with the impurity element of oxygen. The PL characteristic spectra of the target showed the 470 nm blue emission obviously, and the Ba-Al-S thin films also transmitted a purple-blue emission at the position of 440 nm.The results indicated that this method was suitable for the fabrication of the Ba-Al-S：Eu sputtering target.

Research on purification and modification of I/S bentonite

Analyzing raw material＇s structure and performance of bentonite from Panzhihua in Sichuan, the authors think that it is adequate for agglomerant of iron smelting. According to its composition and property we have researched the purification and modification of I/S bentonite under conditions of different dispersants and sodium agent. XRD test result reveals that the essential minerals of Panzhihua bentonite are I/S mixed-layer ones, and FTIR analysis shows that when adding 1.5% sodium pyrophosphate to the bentonite slurry during purification, the composition of quartz in bentonite decreases to less than 4% and I/S is more than 90%. The optimized modification technic conditions are Na2CO3 （4%） and CMC-Na （3%） as modified agents, the clay and water are 10 vs. 1, and the temperature is 75℃. It is 40 min for stirring time and reacting time is 4 h. Under the conditions we can get the modified I/S bentonite with colloid index more than 500 nd/15 g.

A new type of rare earth elements deposit in weathering crust of Permian basalt in western Guizhou, NW China

A new type of rare earth elements （REEs） deposit was discovered from the gaolinite mudstone in the weathering crust of Permian basalt, Bijie region, western Guizhou, China. It contained ∑RE2O3 0.065%-1.086%. This type of REEs deposit was widely distributed with steady horizon and thickness of 3-4 m. The ore-bearing weathering crust （kaolinite） of the three discovered REEs deposits belonged to the third episode of the Emeishan basalt eruption. The new type of REEs deposit was suggested that basalt （tuff） weathering could lead to the enrichment of the rare earth elements. Therefore, it is of important economic significance to explore REEs deposits in the weathering crust of basalt （tuffs） in Yunnan, Guizhou, and Sichuan Provinces.

Microstructure evolution of 7050 aluminum alloy during hot deformation

Hot compression of 7050 aluminum alloy was performed on Gleeble 1500D thermo-mechanical simulator at 350 ℃ and 450 ℃ with a constant strain rate of 0.1 s-1 to different nominal strains of 0.1, 0.3 and 0.7. Microstructures of 7050 alloy under various compression conditions were observed by TEM to investigate the microstructure evolution process of the alloy deformed at various temperatures. The microstructure evolves from dislocation tangles to cell structure and subgrain structure when being deformed at 350 ℃, of which dynamic recovery is the softening mechanism. However, continuous dynamic recrystallization (DRX) occurs during hot deformation at 450 ℃, in which the main nucleation mechanisms of DRX are subgrain growth and subgrain coalescence rather than particle-simulated nucleation (PSN).

Study on Multiple Electromagnetic Continuous Casting of Aluminum Alloy

To obtain semi-solid Al alloy billet with high quality, an investigation was carried out by imposing a multiple magnetic field from the outside of a copper mold in the continuous casting. AISi6Mg2 alloy designed for semi-solid metal （SSM） processing was continuously cast through a submerged entry nozzle under various conditions. Effects of multiple magnetic field on meniscus motion, temperature distribution and billet quality were examined. The experimental results showed that meniscus disturbance caused by electromagnetic stirring could be controlled effectively and the surface quality of semi-solid AI alloy billet was improved greatly, and an uniformly fine, globular microstructure across the transverse section of the billet was achieved by optimizing the distribution of multiple magnetic field.

Interfacial microstructure and properties of diamond/Cu-xCr composites for electronic packaging applications

Diamond/Cu-xCr composites were fabricated by pressure infiltration process.The thermal conductivities of diamond/Cu-xCr（x = 0.1,0.5,0.8） composites were above 650 W/mK,higher than that of diamond/Cu composites.The tensile strengths ranged from 186 to 225 MPa,and the bonding strengths ranged from 400 to 525 MPa.Influences of Cr element on the thermo-physical properties and interface structures were analyzed.The intermediate layer was confirmed as Cr3C2 and the amount of Cr3C2 increased with the increase of Cr concentration in Cu-xCr alloys.When the Cr concentration was up to 0.5 wt.%,the content of the Cr3C2 layer was constant.As the thickness of the Cr3C2 layer became larger,the composites showed a lower thermal conductivity but higher mechanical properties.The coefficients of thermal expansion（CTE） of diamond/Cu-xCr（x = 0.1,0.5,0.8） composites were in good agreement with the predictions of the Kerner＇ model.

Effect of electrolysis voltage on electrochemical reduction of titanium oxide to titanium in molten calcium chloride

The electrochemical reduction of solid TiO2 directly to solid metal is a promising alternative to the current Kroll process. The present work is aimed at studying the effect of electrolysis voltage on the rate of electrochemical reduction. The products of electrochemical reduction of TiO2 and Ti2O were examined using the scanning electron microscopy （SEM） and X-ray diffraction （XRD） techniques. The results show that Ti2O was reduced to low valent titanium oxide at 1.5 -1.7 V, which was the result of ionization of oxygen. TiO2 and Ti20 were reduced to titanium metal at 2.1-3.1 V, which was the co-action of ionization of oxygen and calciothermic reduction. The oxygen content decreased rapidly with voltage increasing from 2.1 to 2.6 V, while it changed little from 2.6 to 3.1 V. The optimized cell voltage was 2.6-3.1 V.

Annulus electromagnetic stirring for preparing semisolid A357 aluminum alloy slurry

The effects of pouring temperature and annulus gap width on the microstructure of the semi-solid A357 aluminum alloy slurry prepared by annulus electromagnetic stirring(AEMS)technology were investigated.The results show that low pouring temperature and narrow annulus gap are advantageous to obtaining the small spherical primaryα(Al)phase.The lower the pouring temperature is and the smaller the annulus gap width is,the more uniform,the smaller and the more spherical the microstructure is. The microstructures obtained by the ordinary electromagnetic stirring and AEMS were compared.The results indicate that the primaryα(Al)particles are globular,small and distribute homogeneously in the slurry obtained by AEMS.But in the slurry obtained by the ordinary electromagnetic stirring,the primaryα(Al)particles are small dendrites in the edge of the slurry and they are large and rosette-like or dendritic in the inner of the slurry.

New Technique of Casting-rolling Strips for Semi-solid Magnesium Alloys

The conjugation of semi-solid process technique and casting-rolling technique applied to produce the magnesium strips was studied. The semi-solid slurry has been prepared continuously by the mechanical method and its temperature was controlled strictly at the same time. AZ91D and AZ31 casting magnesium alloys were applied to the experiment. The casting-rolling strips with non-dendritic structure were obtained and its main mechanical property is better. The process ability of the casting-rolling strips was studied. It is significative to link the semi-solid process techniques and casting-rolling techniques, through which we can get high quality magnesium alloy strips with non-dendritic structure and improve the overall properties of the products.