Drying of Inorganic Particulate Compounds

ABSTRACT

Inorganic particulates are usually dried in a fixed bed, fluidized bed, or spray dryers. These compounds are easy to dry, once their physical structure, with high porosity, allows moisture content removal with low resistances. For fluidized bed of alumina particle evaluations, a laboratory-scale drying unit was built. The drying experiments were carried out with alumina particles with different diameters to evaluate temperature and air flow rate effects on drying kinetics and bed height. In another case, the dehydration of a mixture of rare-earth chlorides in a fluidized bed was studied, aiming at the production of anhydrous rare-earth chlorides, used to obtain mischmetal by electrolytic and metallothermic processes. The spray drying experiments were carried out in a pilot plant. Spray drying is a technique largely applied in industrial processes to dry solutions or suspensions, converting their solid parts into a dried powder. A set of rare-earth drying experiments was carried out, aiming at the development of techniques to obtain a powder that could satisfy international morphological requirements. The results allowed evaluating the effects of air flow rate, feed concentration, atomizer model, rotation velocity, and atomization pressure on powder density and particle size distribution.     

铝镁合金压铸用高性能稀土模具新材料 RE528的开发

本文从铝镁合金压铸用模具材料的性能要求入手,分析了常规模具材料的问题与不足,并以4Cr5W2VSi钢为基础,通过加入稀土元素和优化成分设计,成功研发一种具备优异冶金质量和组织性能、高附加值的稀土RE528热作模具新材料,其性能大大优于一般模具材料,具有良好应用前景。     

硬质合金类烟机配件的性能改善

硬质合金由于其很高的硬度和光洁度而具有很好的耐磨性,但硬度越高,其脆性就大,不利于零件后期的加工。我们通过在硬质合金混合料中添加稀土氧化物Y2O3、CeO2、La2O3,可提高其加工性并改善硬质合金的耐磨性。     

叶片式空气动力机定子材料与加工工艺优化

以叶片式空气动力机定子常用的40CrMnMo等中碳合金钢加整体淬火的选材与加工工艺制作对照样本,优选稀土镁球墨铸铁加调质或正火处理为定子新的选材与加工工艺并制作被试样本,进行耐磨性能对比试验。试验数据表明,被试样本的耐磨性能与对照样本相当。以该新的选材与加工工艺制作叶片式空气动力机定子,能够显著改善叶片式空气动力机定子的加工难度,提高产品合格率,节省成本。该技术经工业性试验后获工程应用,效果良好。     

Electrical and dielectric properties of lithium manganate nanomaterials doped with rare-earth elements

Substituted LiR_xMn_2 − xO₄ (R = La³⁺, Ce³⁺_, Pr³⁺ and x = 0.00 − 0.20) nanoparticles are prepared by the sol–gel method and the consequent changes in their lattice structure, dielectric and electrical parameters are determined by XRD, ED-XRF, SEM, LCR meter bridge and dc electrical resistivity measurements. Diffraction data show that the samples are single-phase spinel materials with crystallites sizes between 21 and 38 nm. The lattice parameter, cell volume and X-ray density are found to be affected by doping the Li-manganate with the rare-earth elements. The ED-XRF analysis confirms the stoichiometric composition of the synthesized samples and SEM reveals their morphology. Calculated values of the dielectric constant (?) and the dielectric loss (tan δ) decrease with the frequency of the applied field. This is attributed to Maxwell–Wagner polarization. Replacement of manganese by the rare-earth elements results in an improvement in the structural stability of the material, which is considered to be useful for enhancement of the cycleability of the compounds when used in lithium rechargeable batteries, and increases significantly the values of ? and tan δ (except for Ce). Lithium manganate nanomaterials with high ? and low tan δ may be attractive for application in memory storage devices.     

Phase stability and electronic structures of YbAl3−xMx (M = Mg, Cu, Zn, In and Sn) studied by first-principles calculations

YbAl₃ is a potential thermoelectric (TE) material to be used in TE power generator utilizing waste heat sources. This work systematically investigated the alloying behavior of M in YbAl_3−xM_x (M = Mg, Cu, Zn, In and Sn) and their electronic structures by first-principles calculations. The solubility of alloying elements M and phase stability of YbAl_3−xM_x were studied by analyzing the elastic constants, formation and cohesive energies. The results show that Mg, In and Sn are the effective alloying elements for preparing YbAl_3−xM_x solid solutions, which are helpful for improving TE properties of YbAl₃.     

First-principles calculations of LaNi_(5-x)Sn_xH_y intermetallics and intermediate phase

The crystal and electronic structures of LaNi4.75Sn0.25 intermetallics and LaNi4.5Sn0.5Hy (y=2.0, 2.5) intermediate phase have been investigated by the full-potential linearized augmented plane wave (FP-LAPW) method. Hydrogen occupation sites in LaNi4.5Sn0.5Hy have been determined based on Westlake s criterions: (1) the minimum hole radius is 0.04 nm; (2) the minimum H-H distance is 0.21 nm; as well as geometry optimizations and internal coordinates optimizations. We find that hydrogen atoms prefer to occup...     

稀土固体超强酸SO4^2—／TiO2／La^3＋催化合成丁酸丁酯

研究了以稀土固体超强酸ＳＯ４＾２－／ＴｉＯ２／Ｌａ＾３＋为催化剂,丁酸和正丁醇为原料合成丁酸丁酯,并考察了影响反应４ 因素。结果表明,醇酸物质的量比为１．８：１,催化剂用量为０．５ｇ（本酸为０．２ｍｏｌ的情况下）,带水剂甲苯为１５ｍＬ,反应时间为２．０ｈ是合成丁酸丁酯的较适宜的反应条件,酯化率达９８．６％。     

On the crystal structure of new series of compounds, RPt2+xSb2−y (x = 0.125, y = 0.25; R = La, Ce, Pr)

A new compound CePt_2+xSb_2−y (x = 0.125, y = 0.25) was synthesized by arc-melting of the elements. The chemical and structural characterizations were carried out at room temperature on as-cast samples using X-ray diffractometry, metallographic analysis and EDS-microanalysis. According to the results of X-ray single crystal diffraction this antimonide crystallizes in I4cm space group (no. 108), Z = 32, ρ = 12.19 Mg/m³, μ = 89.05 mm⁻¹ (a = 12.5386(3) Å, c = 21.4692(6) Å (crystal I) and a = 12.5455(2) Å, c = 21.4791(5) Å (crystal II)). The structure and composition were confirmed by powder X-ray diffraction (a = 12.4901(2) Å, c = 21.3620(4) Å) and EDS-microanalysis respectively. Isotypic compounds were observed with La and Pr from X-ray powder diffraction of as-cast alloys at room temperature (a = 12.6266(4) Å, c = 21.4589(6) Å for LaPt_2+xSb_2−y and a = 12.5184(5) Å, c = 21.4178(7) Å for PrPt_2+xSb_2−y). The CePt_2+xSb_2−y structure is derived from CaBe₂Ge₂ (a = 2a₀ − 2b₀, b = 2a₀ + 2b₀, c = 2c₀) and comprises a new atomic arrangement with both vacancy on 4(b) pyramidal site and substitution of antimony atoms (X) by platinum (B) in the B–XX–B layers (referring to the subcell structure) forming two B––1/2B1/2XX–3/4B and two X–BB–X layers per cell. The structure of CePt_2+xSb_2−y is compared with those reported before for URh_1.6As_1.9 and CeNi_1.91As_1.94.