Evolution and deformability of inclusions in Al-killed steel with rare earth-alkali metals (Ca or Mg) combined treatment

The quality of stainless steel is closely related to the deformability of inclusions,which is significantly affected by their compositions.The present study first inve stigated the evolution of inclusion compositions in AI-killed steel with rare earth-alkali metals(Ca or Mg) combined treatme nt through four laboratory-scale experiments.The Ce contents in the final steel are 0.0080 wt%,0.015 wt%,0.016 wt% and 0.010 wt%,respectively.The Mg content is 0.0014 wt% in Ce-Mg combined treated steel,and ...     

氟化物体系电解制取混合稀土金属的研究

以氟化物体系制取混合稀土金属时,金属的组成与电解质的组成有关,确定合适的电解质组成,控制适当的电解温度,可以生产组成稳定、碳含量低的混合稀土金属,产品可作为生产Ni/NH电池的原料。     

Hydrothermal synthesis of ultrafine zirconia powders

The effect of precursors (zirconyl chloride, zirconyl nitrate, and zirconyl acetate) on the properties (phase composition, kinetics of particle growth, agglomerate characteristics, etc.) of ultrafine M-ZrO₂ powder is studied. Zirconyl chloride is shown to be the optimum precursor for the preparation of ultrafine ZrO₂ powder with higher activity. Institute of Materials Science, National Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 74–80, July–August, 1997.     

Hydrothermal synthesis of dy-doped BaTiO3 powders

Submicron-sized (∼200 nm), monodisperse, and spherical powders of pure and dysprosium (Dy)-doped (0.8 at. pct) BaTiO₃ have been prepared by “hydrothermal synthesis” at 90 °C in an air atmosphere. The powder preparation procedure developed in this work did not necessitate the use of strict and expensive processes, which were commonly required for the removal of free CO₂ present in the atmosphere. The prepared powders were found to be crystalline, pure, and contained no BaCO₃ as an impurity phase. Pure and Dy-doped BaTiO₃ powders synthesized at 90 °C had the pseudocubic (space group: Pm-3m) crystal structure. Grain growth characteristics of pure and Dy-doped BaTiO₃ pellets were compared during sintering in air over the temperature range from 1200 °C to 1500 °C. The Dy doping was found to be significantly effective in inhibiting the anomalous grain growth in BaTiO₃ samples heated at or above 1200 °C.     

Hydrothermal synthesis of 3D porous architectures

A novel porous lanthanide-organic coordination polymer, [Nd(H2O)(HnicO)(TP)]·2H2O (1) (H2nicO=2-hydroxynieotinic acid, TP= terephthalate), was prepared under hydrothermai condition and characterized by single-crystal X-ray diffraction, thermogravimetrie analysis and infrared spectroscopy. Compound 1 exhibited a flexible coordination geometry of lanthanide ions, which possessed a three-dimensional (3D) open framework with one-dimensional (1D) channels containing lattice water molecules. This framework structure exhibited a high stability up to 330 ℃ after removing free water molecules. A homometallic supramolecular framework (Zn(HnicO)2(H2O)2 (2)) was obtained due to the competitive reaction between organic ligands, Nd3+ and Zn2+ ions. The results showed that on the basis of the soft-hard/acid-base principle the coordination selection between metal ions and organic ligands played an essential role in the smart construc-tion of lanthanide architectures.     

Kinetics and Sulfur fixation in the reduction or oxidation of metal Sulfides mixed with lime

A number of metallurgical processes involve roasting of metal sulfides with oxygen or reduction of metal sulfides with hydrogen. In each case sulfur-bearing gases are emitted. Lime can be used to capture these sulfur-bearing gases. A model of this reaction occurring in a pellet made up of grains of metal sulfide and lime is presented. Specifically, a pellet made up of a mixture of metal sulfide and lime surrounded by a lime layer is considered. The computational investigation shows the distribution of lime necessary to achieve the maximum fixation of sulfur-bearing gases in the shortest time.     

铈稳定钪掺杂氧化锆的水热合成与结构表征

采用水热法制备铈稳定钪掺杂氧化锆的超细纳米晶。利用X射线衍射仪、傅里叶红外光谱仪分别研究水热产物的物相和结构,结合热重-差热分析仪分析水热反应过程物相与能量的变化,通过透射电子显微镜研究pH值对水热产物颗粒大小与聚集状态的影响。结果表明,在200℃、pH=8、反应时间为3 h时,得到的水热产物为立方单相,粒径约为4nm。当pH值升高到10时,立方相的颗粒出现长大和团聚现象,平均粒径约为6nm。     

特殊形貌微米铜粉的水热制备

具有特殊形貌的微米粉末材料是现代材料研究的一个重要领域。本试验以CuSO4.5H2O和NaOH为主要原料,通过添加适量的D-山梨(糖)醇,利用简单的水热反应制备了结构各异的微米级铜粉。X射线衍射(XRD)和扫描电镜(SEM)表征表明:在180℃下保温18h,当CuSO4.5H2O和NaOH的摩尔比为1∶3且CuSO4.5H2O和D-山梨糖醇的摩尔比为2∶3时,所得均一的微米级铜粉具有六向等同电子云形貌,有别于其他比例条件下铜粉的形貌。研究结果为制备具有特殊结构和形貌的金属粉体提供了一种新方法。     

Thermodynamics of rare earth metal interaction with copper

The change in thermal and thermodynamic properties along the isoformula series of rare earth metals (R) compounds with copper is analyzed. It is shown that in binary R-Cu systems the maximum thermal effects of formation are observed for the most refractory and congruently melting intermetallic compounds. In the liquid state they are observed at concentrations that are close to the composition of these compounds. It is noted that in contrast to other R scandium on reaction with copper behaves as a d-metal. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 36–43, March–April, 2006.     

Hydrothermal synthesis of Ce: LuzSiO5 scintillator powders

The synthesis of cerium-doped lutetium oxyorthosilicate (LSO) polycrystalline powders was investigated by a hydrothermal proc-ess. The precursor was obtained by the hydrothermal reaction of Lu(NO3)3 with Na2SiO3 at 200 ℃ for 10 h by using urea as precipitator, fol-lowed by a calcination uader proper temperatures. The results of XRD indicated that the precursor was crystallized into A-type LSO phase at 1000 ℃, and transfetrred to B-type LSO phase when temperature was raised above 1050 ℃. After being heated at 1250 ℃ for 2 h, single phase of B-type LSO powder was synthesized with homogeneous distribution of particle size ranging from 200 to 300 nm. The photolumi-nescence spectrum of as-synthesized LSO: Ce powders showed a typical broad emission peak centered at 404 nm, corresponding to the 5d1-4f transition of Ce3+.     

Leaching hydrodynamics of weathered elution-deposited rare earth ore with ammonium salts solution

In order to reveal the permeability rule of leaching agent solution and the effects of anions in the leaching process of weathered crust elution-deposited rare earth(RE) ores, the effects of ammonium concentration, temperature, particle size and porosity on the permeability were discussed in detail with(NH_4)2_SO_4, NH_4Cl and NH_4NO_3 as the leaching agent. It was found that the permeation velocity of ammonium salts increased linearly with the increase of hydraulic gradient. The seepage of ammonium salts solution in the RE ores followed Darcy's law and displayed a laminar flow. The properties of the leaching agent solution and RE ores were the main factors that affect the permeability of RE ores. With the decrease of ammonium concentration and increase of temperature, the viscosity of solution decreased and the permeability coefficients of RE ores increased. And the effects of temperature on the viscosity and permeability were larger than ammonium concentration. The permeability of RE ores became worse with the decrease of particle size and porosity, and the particle size played a more important role compared with porosity. The permeability coefficient of RE ores increased and the viscosity of ammonium salts solution decreased in the order of(NH_4)_2SO_4, NH_4Cl and NH_4NO_3, implying that the penetrating power of anions increased in the order of SO_4~(2-), Cl~- and NO_3~-. The results may play a vital role in improving the permeability of weathered crust elution-deposited RE ores.     

pH-metric and thermodynamic studies of rare earth metal chelates

Proton ligand stability constants of hydroxybenzoic acid containing nitro group (2-Hydroxy-4-nitrobenzoic acid and 3-Hydroxy-4-nitrobenzoic acid) were determined through Irving-Rossoti pH titration technique. The stability constants of rare earth metal chelates con-taining 2-Hydroxy-4-nitrobenzoic acid and 3-Hydroxy-4-nitrobenzoic acid as ligands were studied in aqueous medium at different ionic strength (μ=0.01, 0.05 and 0.1 mol/L) and temperatures (298, 308 and 318±0.1 K). The values of stability constant were evaluated through different computational methods like successive approximation, least square treatment, correction term method, and convergence method. The observed value of thermodynamic parameters (△G°, △H° and △S°) favors the complex formation between metal and ligands. The order of stability constant was found to be Pr(Ⅲ)相似文献   

Luminescence enhancement of rare earth ions by metal nanostructures

Well-ordered metal structures, i.e. arrays of nanosized tips on silver surface for studies of the luminescence enhancement of absorbed media with rare earth ions were used. These arrays were prepared by the metal evaporation on track membranes. Calculations of resonance frequencies of tips regarded as semispheroids were done taking into account the interaction between dipoles of tips. They were used to discuss experimental results for media with Eu(NO₃)₃·6H₂O salt basing on data for bulk silver dielectric function.     

Preparation of mixed rare earths modified chitosan for fluoride adsorption

This paper described the fluoride removal from water using a new adsorbent namely mixed rare earths modified chitosan (CR). Mixed rare earths mainly contained La followed by Ce which was analyzed by in...     

Decomposition of the mixed rare earth concentrate by microwave-assisted method

A novel process was proposed to strengthen the decomposition of the mixed rare earth concentrate by utilizing the microwave radiation.Mineralogical information on the mechanisms by which microwave heating improved the leaching behavior of rare earth elements(REEs),and an interpretation of the interrelationship between mineralogy,decomposition process,and leaching process were provided in this study.The influences of the temperature,time of microwave heating and contents of NaO H(mass ratio of NaO H to mixed rare earth concentrate)on the decomposition of mixed rare earth concentrate were investigated.The results revealed that the temperature was the main factor affecting the decomposition process.The recovery of REEs by hydrochloric acid leaching reached 93.28% under the microwave heating conditions:140 oC,30 min and 35.35% NaO H.The BET specific surface area and SEM analysis indicated that the particles of mixed rare earth concentrate were non-hole,while the particles presented a porous structure after heating the concentrate by microwave radiation.For the microwave treated sample after water leaching,the BET specific surface area was 11.04 m~2/g,which was higher than the corresponding values(6.94 m~2/g)for the mixed rare earth concentrate.This result could be attributed to the phase changes of bastnaesite and monazite,and a number of cracks induced by thermal stress.The increase of BET specific surface area resulted in an increase of the recovery of REEs by promoting interaction within the system of acid leaching.     

Process optimization of rare earth and aluminum leaching from weathered crust elution-deposited rare earth ore with compound ammonium salts

In order to intensify the leaching process of rare earth(RE) and reduce the impurities in the leachate, ammonium chloride(NH4Cl) and ammonium nitrate(NH4NO3) were mixed as a compound leaching agent to treat the weathered crust elution-deposited RE ore. Effects of molar ratio of NH~+_4Cl and NH_4NO_3, ammonium(NH_4) concentration, leaching agent pH and flow rate on the leaching process of RE were studied and evaluated by the chromatographic plate theory. Leaching process of the main impurity aluminium(Al) was also discussed in detail. Results showed that a higher initial ammonium concentration in a certain range could enhance the mass transfer process of RE and Al by providing a driving force to overcome the resistance of diffusion. pH almost had no effects on the mass transfer efficiency of RE and Al in the range of 4 to 8. The relationship between the flow rate and height equivalent to a theoretical plate(HETP) could fit well with the Van Deemter equation, and the flow rate at the lowest HETP was determined. The optimum conditions of column leaching for RE and Al were 1:1(molar ratio) of NH_4Cl and NH_4NO_3, 0.2 mol/L of ammonium concentration, pH 4–8 of leaching agent and 0.5 mL /min of flow rate. Under this condition, the mass transfer efficiency of RE was improved, but no change was observed for Al compared with the most widely used ammonium sulfate. Moreover, the significant difference value(around 20 mL) of retention volume at the peak concentration between RE and Al provided a possibility for their separation. It suggested the potential application of the novel compound leaching agent(NH_4Cl/NH_4NO_3). It was found that the relative concentration of RE in the leachate could be easily obtained by monitoring the pH of leachate.