单一稀土Ce, La和混合稀土在工业纯铝中的作用

通过对比实验的方法，研究了稀土Ce，La和混合稀土对工业纯铝组织、电性能和机械性能的影响。结果表明：单一稀土La，Ce可降低工业纯铝的电阻率，提高工业纯铝的导电性，其中La的效果优于Ce．而混合稀土对电阻率几乎无影响；La，Ce和混合稀土均能减小工业纯铝的晶粒度，在其加入量为0．1％后细化效果明显，当其含量大于0．5％后细化效果趋于平缓，其中Ce的效果最佳，La次之，混合稀土最弱；单一稀土La，Ce在一定含量时可提高工业纯铝的σb6和δ，Ce的作用强于La，混合稀土对σb和δ的影响不明显。     

镧增加铝合金熔体氢含量的实验分析

采用第一滴气泡法和减压凝固法分析测量了一定量的稀土镧加入前后的铝硅合金熔体氢含量和铝硅合金凝固试样剖面的针孔和气孔的变化，发现镧的加入量超过一定量(0．3％)时，铝合金熔体中的氢含量增加，铝合金凝固试样的针孔和气孔增多。可以认为：一定量的稀土镧引起铝合金增氢现象的原因是镧中含有氢。同时，讨论了镧中氢的来源和含量对铝合金中氢的影响。     

铝,镁轻合金中的稀土

综述了稀土－镁和稀土－铝合金的晶体化学、热力学和相图数据，根据其前景特别注意了富镁，富铝稀土合金及添加稀土对合金性能的影响，报道了若干稀土－鲜、稀土－铝及含两个没稀土的镁、铝合金的研究结果。对富镁、富铝的二元和三元合金相的结晶及形成规律进行了总结和讨论，并对有确定结构的合金精细设计和可能的应用提出了建议。     

稀土化合物的铝热法还原研究

目前,稀土铝合金的制备方法有混熔法(又称对掺法)、以铝为液态阴极的熔盐电解法和铝热还原法等三种。从能源和经济效益考虑,铝热还原法工艺简单,操作方便,在适当条件下可获得较高的稀土收率,是一种较有发展前途的稀土铝合金制备方法。鲁化一等曾采用铝热还原法成功地制取了RE-ZL104合金,并已投入了工业生产。通常在铝合金中应用较多的是混合稀土,对单一稀土化合物的铝热还原法制备稀土铝合金的报道很少。本     

用电化学测氢法研究稀土对变形铝及Al-Zn-Mg合金氢含量的影响

铝及铝合金有强烈的吸氢特性,这一直是铝合金冶金中的一大难题。近年来不少冶金工作者证实,在熔融状态下的工业纯铝、Al-Si、Al-Cu合金中添加稀土对氢含量有影响。但至今未见有关室温下稀土对变形铝合金中氢含量影响的报道。本文采用电化学测氢法,准确测定了室温下金属中氢含量和氢行为的特点,研究了室温下工业纯铝和     

稀土在纯铝及铝合金中的固氢作用

采用二次离子质谱对纯铝及铝-锰合金中某些球状稀土相进行面分布测定。结果表明,稀土相中存在铈、铁、硅与氢的成分偏聚,证实了铝及铝合金中富氢稀土化合物的存在,提出稀土具有“固氢”作用的观点。     

用XPS,SIMS对稀土—6063铝合金表面状态的研究

用X射线光电子能谱(XPS)和二次离子质谱仪(SIMS)等表面分析方法对稀土-6063铝合金进行了研究,发现稀土铝合金的表面为金属铝和铝的氧化物两种形态。稀土及镁两者的协同作用,可以缓和铝合金的氧化程度。SIMS结果表明,加入适量稀土,可以抑制镁在稀土-6063铝合金的表面偏析作用。     

钇对Al—Cu—Mg三元系α相区及硬铝性能的影响

许多研究工作表明,在铝基合金中加入少量稀土元素,在一定程度上能改善其性能。由于固溶度的变化,析出的二次相S和θ是硬铝合金的主要强化途径,因此研究稀土钇对Al-Cu-Mg三元系α相区的影响,对改善硬铝合金性能是有益的。文献报道了该三元系在430℃的等温截而。为便于比较,本文研究了加入0.2wt％Y的Al-Cu-Mg三元系在430℃的等温截面以及α相区的变化。     

混合稀土对热浸镀55％Al－Zn合金涂层抗氧化性能的影响

研究了混合稀土对热浸镀５５ｗｔ％Ａｌ－４３．４ｗｔ％Ｚｎ－１．６ｗｔ％Ｓｉ合金涂层的高温抗氧化性能的影响。结果表明，在８００℃×１００ｈ和１０００℃×５０ｈ的氧化试验中，加入０．１ｗｔ％的稀土对涂层抗氧化效果最佳。用电子探针仪（ＥＰＭＡ），扫描电子显微镜（ＳＥＭ）和Ｘ射线衍射仪（ＸＲＤ）等观察分析了涂层氧化膜的形貌结构和涂层断面成分分布，认为稀土改善了氧化膜的抗剥落能力，并对涂层中铝的扩散退化起到抑制作用，使涂层中的铝含量在高温氧化中保持较高水平。     

稀土元素在铁铬铝合金中的作用

本文对稀土在铁铬铝合金中的作用机理从热力学和动力学两方面进行了研究,证实了稀土在合金中以稀土夹杂、金属间化合物和固溶稀土三种形式存在。稀土在不同工艺冶炼的铁铬铝合金中的物相分配不同。讨论了稀土的脱氧、脱硫、抑制晶粒长大、净化晶界和基体,以及对氧化铝夹杂的变质作用。通过动力学试验和氧化膜分析得到,稀土改变了氧化膜的组成和结构,增加了氧化膜的粘附性、提高了合金的抗氧化性和高温寿命。提出了几种主要的铁铬铝合金冶炼工艺的稀土最佳加入量。     

稀土Invar合金热力学性质研究

制备了稀土Invar（因瓦）合金YFe_(12-x)V_x（x＝1.6，2.0；2.4，2.8，3.2）和SmFe_(12－x_V_x（x=2.4, 2.8）采用电动势法以CaF_2单晶作为固体电解质，测定了钇和钐在相应合金中的活度．计算了偏摩尔自由能等热力学性质．测定温度对两类合金分别为920－1020 K和900－1000 K．     

负载型La0.8Sr0.2MnO3燃烧催化剂的载体效应

Combustion catalysts La0.8Sr0.2MnO3 supported on γ-Al2O3, α-Al2O3, cordierite (2MgO•2Al2O3•5SiO2) and ZrO2 were compared. Further investigation was focused on LSM/ γ-Al2O3 catalyst. It was observed that LSM/γ－Al2O3 catalyst loaded with 20% (mass fraction) LSM (La0.8Sr0.2MnO3 or corresponding oxides), heated at 750℃ or above, perovskite-type oxides were found by XRD examination, whereas, the same catalyst loaded with 10% or less LSM, perovskite oxides were absent, calcination temperature about 750℃ is necessary for the formation of perovskite structure in LSM/γ-Al2O3 catalysts. High activity of complete oxidation of xylen will be obtained when perovskite-type oxides.
Investigation of TPR showed that neat LSM or LSM/γ-Al2O3(20%) was reduced by H2-N2 mixed gas. Two degradation processes took place. In the first, reduced temperature peak was about 350 - 450℃. If reduction ended at 400℃, perovskite structure was retained, which may be due to the reduction of Mn3+to Mn2+ on the surface of LSM only. In the second process, perovskite structure was destroied, and La2O3, Mn2O3, Mn - Sr - O oxides could be obtained, which took place in the temperature range 685 - 750℃ and ended at 800℃. This was proved by TPR experiments (Fig. 3, 5) and XRD patterns (Fig. 4)
Catalysts LSM/γ-Al2O3(10% or 20%) heated at 500℃ have only one TPR peak, i. e. lower temperature peak. This is due to the absence of perovskite-type oxides in the catalysts. However, neat LSM or LSM/γ-Al2O3(20%) heated 750℃ or above, not only the first low temperature TPR peak but also the second peak, which is contributed by the perovskite-type oxides in these catalysts appeared. Therefore, the second TPR peak, i. e. the higher temperatue peak is a characteristic peak for perovskite-type oxides in the reduced process. When LSM/ γ-Al2O3 (10%) catalys is heated at 750℃, no perovskite-type oxides were detected by XRD, and the second reduction peak was absent also in TPR process. \
The order of the second reduction peak temperature(characteristic peak of perovskite - type ox- ides) is: neat LSM(750℃）> LSM/γ-Al2O3 20% (685-698℃) -deposited LSM/γ-Al2O3 (698℃) > LSM/γ-Al2O3 15% (677 - 680℃) >(LSM/γ-AL2O3 10% 620 - 630℃, for Mn - Al - O medium oxides on surface). It is correleted with the increasing of the effect of support sequentially.
When LSM/γ-Al2O3 catalysts were heated at 900℃, more stable phase, spinel MnAl2O4 appeared, which could be proved by TPR of model catalyst MnAl2O4/γ-Al2O3.     

多晶Sr0.69La0.31F2.31固体电解质材料的制备

采用共沉淀法直接合成了Ｓｒ０．。６９Ｌａ０．３１Ｆ２．３１固溶体粉末。Ｘ射线衍射分析表明该固溶体为ＳｒＦ２的立方结构,Ｌａ进入ＳｒＦ２晶格,晶格常数σ＝０．５８４３ｎｍ,比纯ＳｒＦ２立方结构的晶格常数略大。电子探针扫描分析表明,该共沉淀Ｓｒ０．６９Ｌａ０．３１Ｆ２．３１固溶体成分均匀,Ｓｒ,Ｌａ元素均匀分布。     

电解液组成对尖晶石LiMn_2O_4中锂离子嵌脱过程的影响

运用电化学阻抗谱(EIS)研究了尖晶石LiMn2O4正极在1mol·L-1LiPF6-EC(碳酸乙烯酯)∶DEC(碳酸二乙酯)∶DMC(碳酸二甲酯),1mol·L-1LiPF6-EC∶DEC∶EMC(碳酸甲乙酯)和1mol·L-1LiPF6-EC∶DMC三种不同电解液中,-20-20℃范围内的阻抗谱特征随温度的变化.研究结果表明,温度强烈影响尖晶石LiMn2O4正极的阻抗谱特征,而电解液组成对尖晶石LiMn2O4正极阻抗谱特征的影响较小,但电解液组成对锂离子在尖晶石LiMn2O4正极中嵌入脱出过程相关动力学参数影响较大.测得尖晶石LiMn2O4正极在上述三种电解液中,锂离子迁移通过固体电解质相界面(SEI)膜的离子跳跃能垒平均值分别为7.60、16.40和18.40kJ·mol-1;电子电导率的热激活化能平均值分别为44.77、35.47和68.06kJ·mol-1;嵌入反应活化能平均值分别为52.19、46.19和69.86kJ·mol-1.     

熔盐法制备Ca0.9La0.2/3Cu3Ti4O12陶瓷粉体及其介电性能研究

以CaCO3,CuO,TiO2,La2O3为反应物,NaCl,KCl为熔盐,通过熔盐法分别在700、750、800、850℃条件下合成Ca0.9La0.2/3Cu3Ti4O12陶瓷粉体。利用XRD和SEM分别对陶瓷粉体的物相结构和微观形貌进行了分析,并对其介电性能进行了测试。实验结果表明,随着合成温度的升高,陶瓷粉体的钙钛矿相含量逐渐增大,与传统固相法相比,熔盐法制备的粉体无团聚现象,耗时少。Ca0.9La0.2/3Cu3Ti4O12粉体制备的陶瓷在1 000℃烧结、测试频率在100 Hz~10 kHz时,获得优良的介电性能:介电常数大大超过104,介电损耗在0.1~0.47之间。     

天然气和甲烷固体氧化物燃料电池中的Ni-LCCM-GDC阳极性能研究

采用溶胶-凝胶法合成了纳米粉体La_1-xCe_xCr_0.5Mn_0.5O_3-δ(x=0.05,0.10,0.15,0.20)(LCCM),并采用共压-共烧结法制备了以复合阳极Ni-La_0.9Ce_0.1Cr_0.5Mn_0.5O_3-δ-Ce_0.8Gd_0.2O_2-δ(GDC)为支撑、GDC为电解质、La_0.8Sr_0.2Co_0.8Fe_0.2O_3-δ(LSCF)-GDC为复合阴极的单电池。利用XRD和SEM等方法对阳极材料进行了晶相结构、化学相容性、微观形貌分析。在500~750 ℃范围内,分别以湿天然气(3% H₂O)和甲烷为燃料气,氧气为氧化气测试了单电池的电化学性能,同时检测了以甲烷为燃料气的阳极尾气组成。结果表明：复合阳极材料具有良好的化学相容性;阳极和阴极具有较好的孔隙结构。以天然气和甲烷为燃料气的单电池在700 ℃时最大电流密度分别为131.96 mA·cm^-2,162.36 mA·cm^-2; 最大比功率分别为28.61 mW·cm^-2,31.03 mW·cm^-2。在500~750 ℃范围内阳极尾气中均检测出CO,CO₂,在700 ℃时CO,CO₂含量达到最大值,分别为2.39254%,6.20891%。     

The thermodynamics of the transformation of graphite to multiwalled carbon nanotubes

The thermodynamic quantities associated to the transformation from graphite to multiwalled carbon nanotubes (MWCNTs) were determined by electromotive force (emf) and differential scanning calorimetry (DSC) measurements. From the emf versus T data of galvanic cell Mo|Cr(3)C(2), CrF2, MWCNTs|CaF2 s.c.|Cr(3)C(2), CrF2, graphite|Mo with CaF2 as solid electrolyte, Delta(r)H(T) degrees= 8.25 +/- 0.09 kJ mol(-1) and Delta(r)S(T) degrees= 11.72 +/- 0.09 JK(-1) mol(-1) were found at average temperature T = 874 K. The transformation enthalpy was also measured by DSC of the Mn(7)C(3) formation starting from graphite or MWCNTs. Thermodynamic values at 298 K were calculated to be: Delta(r)H(298) degrees = 9.0 +/- 0.8 kJ mol(-1) as averaged value from both techniques and Delta(r)S(298) degrees approximately Delta(r)S(T) degrees. At absolute zero, the residual entropy of MWCNTs was estimated 11.63 +/- 0.09 JK(-1) mol(-1), and transformation enthalpy Delta(r)H(0) degrees approximately Delta(r)H(298) degrees. The latter agrees satisfactorily with the theoretical calculations for the graphite-MWCNTs transformation. On thermodynamic basis, the transformation becomes spontaneous above 704 +/- 13 K.     

Impedance of the Ag|Nd0.95Sr0.05F2.95 Crystal|Ag System

Electrochemical studies of the Ag|Nd_0.95Sr_0.05F_2.95 crystal|Ag system at 94 to 1072 K are carried out using impedance measurements over the 10⁻¹ to 10⁷ Hz frequency range. Contributions of conduction and bulk and electrode polarization are distinguished in the impedance spectra of the Ag| Nd_0.95Sr_0.05F_2.95|Ag cell. Anionic conductivity of the Nd_0.95Sr_0.05F_2.95 crystal varies from 3 × 10⁻¹³ to 0.4 S/cm. The mechanism of anionic conduction and models for the electrode and bulk polarization are discussed.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 1005–1009.Original Russian Text Copyright © 2005 by Sorokin.     

Analysis of chemical interactions between stabilized zirconia and perovskites

LaMnO(3)-based perovskites are used as cathode materials in solid oxide fuel cells (SOFC). A major aspect for their applicability is their chemical inertness in connection with the electrolyte material YSZ (Zr(0.85)Y(0.15)O(1.93)) against zirconate formations. Perovskites with the composition La(y-x)(Sr, Ca)(x)Mn(1-u)Co(u)O(3) (y = 1.0 and 0.95; x = 0- 0.2 and 1; u = 0 and 0.2) were investigated with regard to their reactivity with YSZ at different reaction times and temperatures. Powder mixtures and double-layer reaction couples were used for the investigations. XRD phase analyses, SEM/EDX and EPMA were applied for the characterization of the annealed samples. La-deficient perovskites (y = 0.95) partially substituted by Sr and Ca improve the chemical compatibility of perovskite compositions towards YSZ. Sr-containing perovskites were found to have a higher reactivity than Ca perovskites for La(2)Zr(2)O(7) formation. On the other hand enhanced Ca diffusion into YSZ was observed. Co substitution on Mn lattice sites decreased the chemical compatibility, especially for Sr containing perovskites.     

Ba0.95Ce0.9Y0.1O3-α固体氧化物燃料电池性能

以Ba0.95Ce0.9Y0.1O3-α为固体电解质,Pt为电极,组成氢-空气燃料电池,测定了该电池600～1000℃下电流-电压特性、电极极化特性和电解质中各电荷载流子(质子、氧离子、电子空穴)迁移数及其电导率。实验表明,该电池放电性能良好,能稳定地输出电能,1000℃时的最大输出电流密度为680mA.cm^-^2。正、负Pt电极极化特性很小,放电时的电压耗损主要由电解质电阻产生。在氢-空气燃料电池条件下,Ba0.95Ce0.9Y0.1O3-α显示混合离子(质子+氧离子)导电性。随着温度升高,质子迁移数减小而氧离子迁移数增大,当温度为780℃时,质子和氧离子迁移数相同(0.46),在低于780℃时,质子电导占优势,而在高于780℃时,氧离子电导占优势。