含镧ZA12和ZA27合金相变过程的DSC分析

用差示扫描量热分析（ＤＳＣ）研究了Ｌａ对ＺＡ１２和ＺＡ２７铸态合金加热及冷却相变的影响。结果表明，ＺＡ１２中含０．４％Ｌａ，使合金的凝固温度区间减小，共析转变温度降低，共析转变热增大，表明Ｌａ抑制其共析相变。ＺＡ２７中含０．４％Ｌａ，使合金的凝固温度区间增宽和凝固潜热增加，并使冷却过程中的共晶转变出现双峰，这可能是因为ε相提前析出的缘故。     

Biosorption of lanthanum and cerium from aqueous solutions by Platanus orientalis leaf powder

The biosorption of lanthanum and cerium by leaves powder of Platanus orientalis was separately determined at varying experimental conditions using a batch technique. The effects of initial pH, contact time, initial metal ion concentration and temperature were investigated. The Langmuir and Freundlich isotherms were applied to represent the adsorption process. Langmuir isotherm fits the experimental data quite well. The Langmuir monolayer capacity of the sorbent is 28.65mg g^− 1 and 32.05mg g^− 1 for La and Ce(III), respectively. Thermodynamic parameters such as standard enthalpy (ΔH°), entropy (ΔS°) and free energy (ΔG°) were calculated from the slope and intercept of the plots of lnK_d versus 1/T. The results indicated that sorption was endothermic and spontaneous in nature. The work reveals that powdered leaf of Platanus orientalis is a good choice as a biosorbent for the recovery of lanthanum and cerium from aqueous solution.     

Influence of lanthanum on enhancement of mechanical and electrical properties of Cu-Al_2O_3 composites

Two kinds of Cu-Al_2O_3 composites(with and without La) were prepared via mechanical alloying-spark plasma sintering(MA-SPS) method. Microstructure, mechanical properties and electrical resistivity were investigated systematically using metallography, scanning electron microscopy, transmission electron microscopy, mechanical and electrical properties testing. The results indicate that an appropriate amount of La can homogenize the distribution of Al_2O_3. As such, yield strength, ultimate tensile strength and elongation of Cu-Al_2O_3-La are greatly increased. Some semi-coherent interface between Cu and Al_2O_3 is found, which means a low interface energy. The grain shape of Cu changes to irregular band with the addition of La. This change results in a density decrease of grain boundary and reduces electrical resistance. Lanthanum may exist in the form of La_2O_3.     

Study on Monoxide Emission Spectrometry of Rare Earth Elements Ⅰ. Determination of Sm in Rare Earth Concentrate by Dual Wavelength Method

ＳｔｕｄｙｏｎＭｏｎｏｘｉｄｅＥｍｉｓｉｏｎＳｐｅｃｔｒｏｍｅｔｒｙｏｆＲａｒｅＥａｒｔｈＥｌｅｍｅｎｔｓⅠ．ＤｅｔｅｒｍｉｎａｔｉｏｎｏｆＳｍｉｎＲａｒｅＥａｒｔｈＣｏｎｃｅｎｔｒａｔｅｂｙＤｕａｌＷａｖｅｌｅｎｇｔｈＭｅｔｈｏｄＺｈａｎｇＺａｉｚ...     

Effects of La and Nd on the Fermentation of Alginic Acid Produced from the Strain 342 of Azotobacter Vinelandii

It is reported that fermentative liquids with various concentrations of La and Nd affect the fer-mentation of alginic acid from the strain 342 of Azotobacter vinelandii.The results are as follows:When theconcentration of La or Nd was up to 100 ppm,the cell growth is stimulated and the production of alginic acidis promoted.The La or Nd in concentration higher than 200 ppm or 150 ppm inhibits the fermentation,respectively.As the concentration range of La is 0～100 ppm or that of Nd is 0～150 ppm,the yield of fixednitrogen increases,and the ratio of c_M to c_G(c_M/c_G)decreases with the raise of the concentration of La orNd.When the concentration range of La is 100～400 ppm and that of Nd is 150～400 ppm,the conclusion iscontrary to the above mentioned result.     

Interplay of plasma etch, strip and wet clean in patterning La2O3/HfO2-containing high-κ/metal gate stacks

The removal process of the La₂O₃/HfO₂ dielectric and of the residues after metal gate etch are discussed. The challenges are presented and related to the specific physico-chemical properties of La-containing compounds. Solutions based on optimization of plasma etch, strip and wet clean are demonstrated for both an integrated and delayed etch-clean process. Both processes meet the stringent requirements of complete removal of the high-κ layers and metal-containing sidewall residues without inducing silicon recess or undercut.     

镓酸镧基固体电解质制备方法的研究进展

综述了镓酸镧基固体电解质的制备方法:包括固相反应法和Pechini法、溶胶凝胶法、甘氨酸-硝酸盐燃烧法、硝酸盐分解法等湿化学方法.简要阐述了各种方法的工艺流程,制备粉体的特性及优缺点.最后展望了今后镓酸镧粉体制备方法的研究发展方向.     

LaMgAl11O19-La2Ce2O7 复合陶瓷的高温相稳定性

La2Ce2O7(LC) 和 LaMgAl11O19(LMA) 是两种新型热障涂层材料。 LC 具有优良的热物理及抗腐蚀性能, 但其断裂韧性差。 LMA 具有良好的综合性能, 特别是力学性能优良。 基于复合材料设计理念, 为充分利用 LC 和LMA 的优势, 本文探究了制备 LMA-LC 双相复合陶瓷的可行性。 采用高温固相法合成了 LMA 和 LC 粉末, 重点研究了 LMA 和 LC 的高温稳定性, 初步研究了 LMA-LC 复合陶瓷块材的力学性能。 结果表明： LMA 和 LC 在高温下发生了化学反应, 反应程度随温度升高而加剧, 主要反应产物为 LaAlO3, 其在低温下的铁弹性可能是复合陶瓷在室温下具有良好力学性能的原因。     

改性天然丝光沸石催化剂对 C_8芳烃转化的催化活性

国产天然丝光沸石先经 NH_4Cl 溶液处理后,分别用离子交换法载上 La~(+++),Ce~(+++),Cr~(+++)或 Ag~(+++)等,可制成载阳离子氢型丝光沸石(MeHNM)。研究表明,这类改性天然丝光沸石催化剂对二甲苯的异构化和乙苯的转化均有良好的催化活性,其中 LaHNM 型催化剂最好。本文研究了 La(+++)交换度对乙苯转化率的影响,结果表明在 La(+++)交换度为18%时,乙苯转化率有最低点,然后随交换度增加而增加。此外,对 LaHNM 型催化剂进行了152小时的稳定性试验,结果尚好。