La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ的柠檬酸盐法制备和性能

采用柠檬酸盐法合成了La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF,x=0.05,0.1,0.15和0.2)粉料.TG-DSC分析表明,凝胶在320℃～558℃分解为相应的氧化物.XRD测试表明产物前躯体在800℃下热处理3h就可制备出具有畸变钙钛矿结构的LSCCF粉料.电导率测试表明,随着烧结温度的升高和Sr2+含量的增加,样品电导率变大,其导电活化能变小.在600℃～800℃范围内,LSCCF样品的电导率为102S/cm～103S/cm,能够满足中温固体氧化物燃料电池阴极材料的要求.LSCCF粉料与Ce0.8Sm0.2O2电解质在800℃下烧结10h后没有新相生成,表明LSCCF粉料与Ce0.8Sm0.2O2电解质具有良好的化学相容性.     

草酸共沉淀制备超细Ce0.8Sm0.2O1.9工艺优化

掺杂铈基电解质由于具有高电导率用于中温固体氧化物电解质材料.实验采用草酸盐共沉淀法制备20%(摩尔分数)Sm2O3掺杂CeO2(Ce0.8Sm0.2O1.9)氧化物粉末,采用XRD、SEM分析粉末的相结构和颗粒形貌,500℃～1000℃煅烧草酸沉淀物,得到氧化物粉末.XRD分析结果表明,Ce0.8Sm0.2O1.9为立方萤石结构,表明在低温合成了纯相的Sm2O3掺杂CeO2固溶体.激光粒度分析仪分析沉淀反应过程中草酸盐沉淀物和氧化物粉末的粒度分布.通过优化沉淀反应pH值、溶液浓度、添加表面活化剂及沉淀物水洗和干燥处理等制备工艺条件,实现对沉淀反应过程中草酸沉淀物的团聚控制,得到分散良好的亚微米草酸共沉淀物,进一步选择合适煅烧温度,得到亚微米级超细Ce0.8Sm0.2O1.9粉末.     

Ce_(0.8)Sm_(0.2)O_(1.9)@TiO_2异质结构电解质研究

半导体与离子导体形成的异质结构可以极大地增强材料的离子电导率,其两相界面能为离子传输提供较好的通道。以TiO_2与Ce0.8Sm0.2O1.9 (samarium doped ceria, SDC)为研究对象,分别通过湿化学法和干混法构造了两种不同的异质结构复合材料。研究表明,利用湿化学法制备的SDC@TiO_2异质结构复合材料(简称SDC@TiO_2)作电解质的燃料电池在550℃下最大输出功率密度为761 mW·cm-2,比用干混法制备的SDC-TiO_2异质结构复合材料(简称SDC-TiO_2)作电解质的燃料电池的最大输出功率密度高21%。与SDC-TiO_2相比,SDC@TiO_2具有更丰富的两相界面。电化学阻抗谱显示,以SDC@TiO_2材料作为电解质的电池具有更低的欧姆电阻和极化电阻。     

Al2O3的掺杂浓度对Ce0．8Y0．2O1．9电解质的性能影响研究

利用低温燃烧合成法制备了Al2O3掺杂浓度为0.5%～10%(摩尔分数,以下同)的Al2O3/Ce0.8Y0.2O1.9固体电解质复合材料。研究了Al2O3掺杂浓度对Ce0.8Y0.2O1.9固体电解质烧结及电性能的影响。试验结果表明,添加少量的Al2O3可以改善Ce0.8Y0.2O1.9固体电解质的烧结性能,当Al2O3的添加量为0.5%时,电解质粉体具有最佳的烧结性能,1350℃时的相对密度达到99%以上。当Al2O3的掺杂浓度超过其在Ce0.8Y0.2O1.9中的溶解极限时,随Al2O3掺杂量的继续增加,烧结体的相对密度开始下降。阻抗谱结果表明,在溶解极限范围内,Al2O3使Ce0.8Y0.2O1.9的电导率减小,电导活化能增加。Al2O3的掺杂浓度超过溶解极限时,Ce0.8Y0.2O1.9的晶粒电阻不变,由于Al2O3对晶界的"清洁"作用,晶界电阻减小;当Al2O3的掺杂浓度超过5%时,由于Al2O3颗粒对晶界的"阻塞"作用,晶界电阻增加。     

Ce0.8Sm0.1Gd0.1O1.9电解质的制备及其性能研究

采用共沉淀法合成了Sm、Gd共掺杂CeO2的Ce0.8Sm0.1Gd0.1O1.9（SGC）电解质粉末。研究了工艺条件等对粉末的相组成、结构、颗粒大小的影响。并对SGC烧结体的性能进行了研究。实验结果表明,共沉淀法成功制备出的SGC电解质粉末有良好的烧结性,1 400℃下得到的SGC烧结体的相对密度大于93%。电性能测试表明烧结体在中温范围内具有较高的氧离子电导率。     

Fabrication and Characterization of SOFC Anode, Ni-SDC Cermet

NiO and Ce0.8Sm0.2O1.9 were synthesized by the combination of sol gel and citric acid-nitrate low temperature self-propagating combustion method. Anode precursors which include home-made NiO and Ce0.8Sm0.2O1.9 were prepared by different NiO content and fabrication condition. The anode precursors with pure hydrogen at 820 ℃ for 2.5 h were reduced, The electrical conductivity was tested, and the effect of microstructure on electrical conductivity of Ce0.8Sm0.2O1.9 composite anodes was investigated. The results show that the anode electrical conductivity depends strongly on the anode microstructure that is dramatically affected by Ni content and fabrication condition.     

阴极材料La0.7Sr0.2Ca0.1Co1-yFeyO3-δ的微波烧结法制备及性能

以碳酸盐和氧化物为原料,采用微波固相烧结法制备了La0.7Sr0.2Ca0.1Co1-yFeyO3-δ(简称:LSCCF,y=0.1,0.2,和0.4)粉料.借助差示扫描量热-热重分析 (DSC-TG) 、X 射线衍射分析(XRD) 和扫描电子显微镜( SEM) 对LSCCF 粉料的形成过程、晶体结构和粒度形貌进行了研究.实验结果表明, LSCCF粉料的形成过程分为3个阶段--反应原料的变化阶段、LaCoO3 基氧化物形成阶段和LSCCF固溶体形成阶段;适宜热处理制度为1 200 ℃下保温30 min,且制备出的LSCCF粉料为均一的钙钛矿结构.使用直流四极探针法测定了LSCCF样品在空气气氛下的电导率,发现该体系材料的电导率随着烧结温度的升高和Fe2 含量的减少而变大,在500～800 ℃范围内,大于500 S/cm,高于固相合成法的电导率最大值100 S/cm.LSCCF粉料与Ce0.8Sm0.2O2电解质的混合物在800 ℃下烧结10 h后没有新相生成,表明LSCCF 粉料与Ce0.8Sm0.2O2电解质具有良好的化学相容性.     

稀土对α-K7[SiFe3(OH2)3W9O37]多金属氧酸盐化学扩渗和导电性的影响

用改进方法合成了标题化合物。采用气相法通过固-气反应,研究多组分稀土对所合成多金属氧酸盐的化学热扩渗。经ICP、XPS、IR和XRD分析发现,微量的La、Ce、Sm、Gd等稀土元素可以渗入到多金属氧酸盐的体相。扩渗后化合物的电导率在室温下σ值达到1.59×10-3S·cm-1,比扩渗前多金属氧酸盐的电导率(σ=2.4×10-7S·cm-1)提高了几千倍;且渗后化合物导电性能的稳定温度显著增大,同导电性能最好的多金属氧酸盐H3PM12O40·29H2O(M=W,Mo)相比,其导电热稳定温度增大近200K,成为在523K以上依然保持高电导率的新型固体电解质。     

溶胶凝胶-自燃烧法制备Ce_(0.8)Y_(0.18)Fe_(0.02)O_(1.9)电解质材料及其性能研究

采用溶胶凝胶-自燃烧法合成了Ce0.8Y0.18Fe0.02O1.9纳米粉体,通过热重、X射线衍射、扫描电镜、透射电镜和交流阻抗谱等方法对试样进行研究。研究结果表明,采用溶胶凝胶-自燃烧法可直接合成纯相的具有立方萤石结构的固溶体Ce0.8Y0.18Fe0.02O1.9;合成粉体的平均粒径为10 nm~20 nm,具有高的烧结活性,在1400℃的烧结温度下,陶瓷样品的相对密度可达到97%;Ce0.8Y0.18Fe0.02O1.9电解质的离子导电性能良好,在600℃和800℃测试温度下,其电导率分别达到12.38 mS/cm和46.81 mS/cm。     

Synthesis and characterization of Ce0.8Sm0.2–xPrxO2–δ（x=0.02–0.08）solid electrolyte materials

Solid electrolytes Ce0.8Sm0.2–xPrxO2–δ(x=0.02, 0.04, 0.06, 0.08) were prepared by citric-nitrate method. The microstructure and electrical properties of such materials were examined by X-ray diffraction(XRD), atomic force microscopy(AFM), Raman spectroscopy(Raman), X-ray photoelectron spectroscopy(XPS) and impedance spectroscopy analyses. Specifically, results from XRD analysis showed that samples calcined at 800 oC for 4 h possessed single-phase cubic fluorite structure, and the average grain size was found to be 36–45 nm. Further Raman spectral analysis indicated that oxygen vacancies should be present in the cubic fluorite structure of Ce0.8Sm0.12Pr0.08O2–δ, and Pr-doping seemed to increase their concentration significantly. AFM images showed that the grain size grew with the increase of Pr substitution. XPS analysis confirmed the existence of oxygen vacancies in the lattice of Ce0.8Sm0.12Pr0.08O2–δ in which Pr3+ and Pr4+ co-existed. AC impedance spectra indicated that the conductivity of Ce0.8Sm0.2–xPrxO2–δincreased with the increase of Pr-doping but the conduction activation energy decreased. Notably, it appeared that sample Ce0.8Sm0.12Pr0.08O2–δ(σ600 oC=1.21×10–2 S/cm, Ea=0.77 e V) exhibited conductivity superior to Ce0.8Sm0.2O1.9(σ600 oC=2.22×10–3 S/cm, Ea=1.02 e V) because it possessed higher conductivity and lower activation energy. At 600 oC, the conductivity of Ce0.8Sm0.12Pr0.08O2–δwas 4.45 times higher than that of the un-doped material.     

X射线荧光光谱法测定Dy_2O_3及其杂质Eu_2O_3,Gd_2O_3,Tb_4O_7,Ho_2O_3,Er_2O_3和Y_2O_3

当前稀土应用范围越来越广,尤其Dy2O3和金属Dy其出口量不断增大．Dy2O3中所含杂质总量通常在0．1％～5％之间,该范围内的测定方法以XRFR为合适,快速、准确、无破坏．1实验部分1．l原理本法采用粉末直接压片法制样,在各元素分析线峰位上测量X射线强度,根据待测元素的X射线荧光光谱强度与含量的定量关系,选择相应的数学模型,由计算机自动计算出待测成份含量．1．2仪器和试剂荷兰飞利浦PW—1400顺序式X射线荧光光谱仪;康柏486计算机;电动小型油压机;万分之一精度分析天平．DyZO399．999％;EnD3,GdD3,ThAn,HoAn,ErD3…     

Solid-phase reactions of Ta2O5 with Ga2O3 and In2O3

Conclusions Using the techniques of DTA and x-ray phase analysis, a study was made of the reactions between Ta₂O₅ and M₂O₃ (M = Ga or In), and the phase compositions of the relevant binary systems were determined. The existence was confirmed of stable compounds of composition MTaO₄ and eutectoidally decomposing phases containing 7.5–12.5 mole % M₂O₃. MTaO₄ are dielectrics, whose room-temperature _v is of the order of 10¹⁰ -cm. The temperature dependence of _v of MTaO₄ was investigated in the range 293–873°K and their energies of activation for conductivity were calculated. The melting points, pyknometric densities, dielectric losses, and relative dielectric permeabilities of MTaO₄ were determined.Translated from Poroshkovaya Metallurgiya, No. 2 (110), pp. 69–73, February, 1972.     

Reaction of O6-benzylguanine-resistant mutants of human O6-alkylguanine-DNA alkyltransferase with O6-benzylguanine in oligodeoxyribonucleotides

Inactivation of the human DNA repair protein, O6-alkylguanine-DNA alkyltransferase (AGT), by O6-benzylguanine renders tumor cells susceptible to killing by alkylating agents. AGT mutants resistant to O6-benzylguanine can be made by converting Pro140 to an alanine (P140A) or Gly156 to an alanine (G156A). These mutations had a much smaller effect on the reaction with O6-benzylguanine when it was incorporated into a short single-stranded oligodeoxyribonucleotide. Such oligodeoxyribonucleotides could form the basis for the design of improved AGT inhibitors. AGT and mutants P140A and G156A preferentially reacted with O6-benzylguanine when incubated with a mixture of two 16-mer oligodeoxyribonucleotides, one containing O6-benzylguanine and the other, O6-methylguanine. When the 6 amino acids located in positions 159-164 in AGT were replaced by the equivalent sequence from the Escherichia coli Ada-C protein (mutant AGT/6ada) the preference for benzyl repair was eliminated. Further mutation incorporating the P140A change into AGT/6ada giving mutant P140A/6ada led to a protein that resembled Ada-C in preference for the repair of methyl groups, but P140A/6ada did not differ from P140A in reaction with the free base O6-benzylguanine. Changes in the AGT active site pocket can therefore affect the preference for repair of O6-benzyl or -methyl groups when present in an oligodeoxyribonucleotide without altering the reaction with free O6-benzylguanine.     

CaO-La2O3-B2O3-Eu2O3转光玻璃的合成及荧光性质

X射线衍射研究表明CaO-La2O3-B2O3-Eu2O3体系的玻璃化温度在1025℃附近。荧光光谱和ESR谱研究表明,在CaO-La2O3-B2O3-Eu2O3玻璃体系中存在着Eu2 和Eu3 两种价态离子。316,360,379,394,413,462和532nm锐线激发峰和592,616和650红区发射峰分别对应Eu3 的f-f激发跃迁和5D0-7FJ(J=1,2,3)跃迁发射;351nm和427nm宽带激发峰和蓝区发射分别对应Eu2 的5d-4f激发跃迁和发射。     

Stability of Fluorine-Free CaO-SiO2-Al2O3-B2O3-Na2O Mold Fluxes

Metallurgical and Materials Transactions B - B2O3 and Na2O are key components of fluorine-free mold fluxes for continuous casting, but both are highly volatile, which affects the flux stability....     

Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics. This work involved a study of the wetting of SiC ceramics by two oxide systems, Al₂O₃ /Dy₂O₃ and Al₂O₃ /Yb₂O₃, which have so far not been studied for application in the sintering of SiC ceramics. Five mixtures of each system were prepared, with different compositions close to their respective eutectic ones. Samples of the mixtures were pressed into cylindrical specimens, which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace. The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle, the parameter that measures the degree of wettability. The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading. All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere. The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX). The DRX analysis showed that Al₂O₃ and RE₂O₃ reacted and formed the Dy₃Al₅O₁₂ (DyAg) and Yb₃Al₅O₁₂ (YbAg) phases. The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.     

Al_2O_3La_2O_3Y_2O_3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al2O3La2O3Y2O3/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al2O3/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y2O3、La2O3稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al2O3La2O3Y2O3/Cu材料的抗熔焊性和抗烧损性优于Al2O3/Cu材料的性能.在直流阻性负载条件下Al2O3La2O3Y2O3/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.