多孔 La0.6Sr0.4Co0.2Fe0.8O3-的制备及表征

多孔La0.6Sr0.4Co0.2Fe0.8O3-陶瓷具有一定的强度、良好的透气和电传导性能,可用于中温SOFC阴极支撑体和氧分离膜活性支撑体. 本文用固相反应法制备了多孔La0.6Sr0.4Co0.2Fe0.8O3-陶瓷. 考察了烧结条件、成型压力和有机添加剂量对孔隙率和孔径的影响. 研究发现气体渗透率随孔隙率线性增长,电导率随孔隙率的增大而下降,并满足关系式=0(1-P)3.1.     

钙钛矿复合氧化物La0.6Sr0.4Fe0.8Co0.2O3的合成与电学性能

采用甘氨酸-硝酸盐(GNP)法合成出La0.6Sr0.4Fe0.8Co0.2O3超细粉体,探讨各因素对产物的晶体结构和显微形貌的影响,研究烧成温度对电导率的影响.研究表明,G/Mn+控制在2.0～3.0、热处理温度为750℃是最佳的合成条件,1200℃烧成样品具有最优良的电性能.在室温～900℃温度范围内,样品的电导率在600℃附近出现最大值,低温段的导电行为符合小极化子导电机制.与常规固相法相比,GNP法制备样品具有更好的烧结活性和导电性能.     

(La,Sr)MnO3/YSZ和La0.6Sr0.4Co0.2Fe0.8O3-δ氧电极SOEC性能的比较研究

构建了氧电极材料分别为(La,Sr)MnO3/YSZ(LSM/YSZ)和La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)的固体氧化物电解池(SOEC).在750℃、电流密度为0.25A/cm2的SOEC模式下,分别对两种类型的SOEC进行了约110h的电解实验.结果表明,LSM/YSZ可能是较好的SOEC氧电极材料.依据电化学表现、XRD和微观结构,阐述了两种类型SOEC氧电极性能表现的可能机理.     

La0.6Sr0.4Co0.8Fe0.22O3粉末的合成与性能表征

La0.6Sr0.4Co0.8Fe0.22O3钙钛矿型氧化物具有良好的电子和离子混合导电性能．可作为中温固体氧化物燃料电池（ITSOFC）的阴极材料。本文中采用EDTA-柠檬酸法合成La0.6Sr0.4Co0.8Fe0.22O3（LSCF）粉末，借助差热-热重（DTA／TG）、X射线衍射（XRD）、扫描电镜（SEM）等分析手段．对阴极材料的合成、掺杂机理、与电解质（YSZ）间的高温化学相容性进行了研究和讨论。结果表明：干凝胶的最佳煅烧温度为800℃。所合成的粉末具有单一的钙钛矿结构，平均粒径约为40nm；掺杂后的LSCF仍保持菱方结构；当SOFC的运行温度低于800℃时，LSCF与YSZ具有良好的化学相容性。     

Densification of La0.6Sr0.4Co0.2Fe0.8O3 ceramic by flash sintering at temperature less than 100 °C

The effect of DC electric field on sintering and electrical conductivity of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF), considered as highly promising cathode material for solid oxide fuel cell, is investigated in the present work. It is shown that sintering can be carried out at (furnace) temperature <100 °C under electric field ranging from 7.5 to 12.5 V/cm; such extraordinary effect is associated with the high electrical conductivity of LSCF through a peculiar mechanism. Microstructural analysis suggests similar morphology and enhanced grain growth compared to traditional sintering; with the proper choice of processing parameters (electric field and current density) during flash sintering, homogeneous porous microstructure for cathodic application can be obtained in very short time. The role of electric field and specimen temperature in flash sintering is analyzed for the understanding of observed outstanding event. The conductivity is found to be a coupled response of electric field and temperature; 2–3 V/cm and 15–25 °C are sufficient for dense LSCF specimen to stimulate the electric field effect on sintering. Electric field controls the conductivity in the same way as temperature does suggesting that under flash effect conductivity is increased by usual mechanism. On the same basis, flash sintering is proposed to be accelerated by the “polaron hopping” phenomenon.     

Enhanced electrochemical performance of La0.6Sr0.4Co0.2Fe0.8O3-δcathode via Ba-doping for intermediate-temperature solid oxide fuel cells

La0.6Sr0.4Co0.2Fe08O3-δ(LSCF)is recognized as one of the most promising cathode materials for the highly-desired intermediate-temperature solid oxide fuel cell(...     

LnBaCo2O5+δ(Ln=Gd,Nd,Sm,Pr)-Ba0.5Sr0.5Co0.8Fe0.2O3-δ双相混合导体透氧膜的制备及性能测试

用固相反应法制备了LnBaCo2O5+δ(Ln=Gd,Nd,Sm,Pr)-Ba0.5Sr0.5Co0.8Fe0.2O3-δ(质量比为1:1)4种双相混合导体膜.通过XRD分析可知,除了PrBaCo2O5+δ和Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF)复合时发生明显反应外,其它3种复合膜在复合过程中均显示了良好的化学兼容性.4种双相膜在850℃时透氧率最高的是NdBa-(Co2O5+δ-Ba0.5Sr0.5Co0.8Fe0.2O3-δ膜(约为0.28mL/(cm2·min)).     

基于Pr0.6Sr0.4Co0.2Fe0.8O3-δ对称固体氧化物燃料电池的性能优化研究

采用柠檬酸-硝酸盐自蔓延燃烧法分别合成了Pr_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ(PSCF)和Gd_0.2Ce_0.8O_2-δ(GDC)粉体, 高温固相法合成La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ(LSGM)电解质粉体。以LSGM为电解质, PSCF同时作为阴极和阳极, GDC作为功能层材料, 构建了对称固体氧化物燃料电池PSCF│GDC│LSGM│GDC│PSCF。利用X射线衍射法研究材料的成相以及相互间的化学稳定性, 交流阻抗法记录界面极化行为, 用扫描电子显微镜观察电池的断面微结构, 用自组装的测试系统评价电池输出性能。结果表明, 合成的PSCF粉体呈立方钙钛矿结构, 具有良好的氧化-还原可逆性。使用GDC功能层明显改善了氢气环境下PSCF与LSGM材料间的化学相容性以及电池的输出性能, 800℃时, 电极│电解质界面极化电阻从6.892 Ω·cm²下降到0.314 Ω·cm²; 以加湿H₂(含体积分数3%的水蒸气)为燃料气, 空气为氧化气时, 单电池输出功率密度由269 mW/cm²增大至463 mW/cm²。研究结果显示, PSCF是对称固体氧化物燃料电池良好的候选电极材料, GDC功能层对改善电池长期稳定性能具有潜在的应用价值。     

Ln0.6Sr0.4 FeO3-δ(Ln=La、Nd、Ce)阴极材料的制备与表征

以甘氨酸-硝酸盐水溶液为前驱体合成了Sr掺杂的稀土铁酸盐Ln0.6Sr0.4FeO3-δ(Ln=La、Nd、Ce)粉体.对制备过程的化学键变化、样品的热稳定性、物相形成过程及导电性进行了表征.结果表明,甘氨酸-硝酸盐合成法成相温度低于1000℃.坯体烧结较粉状样品更有利于钙钛矿物相的形成,La0.6Sr0.4FeO3-δ及Nd0.6Sr0.4FeO3-δ坯体1000℃煅烧2h即可形成近乎单一的钙钛矿相(ABO3);Ce0.6 Sr0.4 FeO3-δ是CeO2立方萤石相和产物钙钛矿相共存,两相难分主次.合成样品低温下的导电行为符合小极化子导电机制;1200℃烧结的La0.6Sr0.4FeO3-δ样品在测试全温度范围内(450～800℃)电导率超过100S/cm,Nd0.6Sr0.4FeO3-δ在中温区(600～800℃)电导率＞60S/cm;Ce0.6Sr0.4FeO3-δ样品的电导率不理想.     

La0.6M0.4Fe0.8Cr0.2O3-δ(M=Ca、Sr、Ba)的制备、表征及电性能

采用甘氨酸-硝酸盐法(GNP)制备了纳米尺寸的La0.6M0.4Fe0.8Cr0.2O3-δ(M=Ca、Sr、Ba)系列粉体.BET测试表明,合成粉体的比表面积>20m2·g-1;XRD结果显示,GNP法合成粉体在燃烧阶段物相已初步形成,La0.6Ca0.4Fe0.8Cr0.2O3-δ(LCFC)初粉经850℃热处理2h即转变为简单立方钙钛矿结构的纯相产物,1100℃下烧结体的相对密度即达95%,La0,6Sr0.4Fe0.8Cr0.2O3-δ(LSFC)、La0.6Ba0.4Fe0.8Cr0.2O3-δ(LBFC)初粉为双相结构,两者在低温段的烧结活性较LCFC差,1300℃以上相对密度接近95%.四端子法电导测试表明,掺杂样品的电导率较LaFeO3高2个数量级以上,700℃以下三者的电导率随温度的变化符合小极化子导电机理;800℃下LCFC的电导率>50S·cm-1,预示其可能成为IT-SOFC有实际应用前景的阴极材料.     

复合氧化物Ln0.67Sr0.33MnO3（Ln=La,Pr,Nd,Sm）的制备,结构与电性

本语文通过共沉淀工艺合成了复合氧化物Ｌｎ０．６７Ｓｒ０．３３ＭｎＯ３（Ｌｎ＝Ｌａ、Ｐｒ、Ｎｄ、Ｓｍ）与传统陶瓷制备方法相比，成相温度降低约４５０℃，经Ｘ射线衍射分析表明，所得复合氧化物为立方钙钛矿结构，晶胞参数随稀土离子半径变化而呈规律性变化，样品的四极法电阻率测试结果表明；样品中的稀土离子Ｌｎ的离子半径对其本身的地电性起决定性的作用，应用双交换理论，样品中的稀土离子Ｌｎ的离子半径对其本身的导电性     

(Pr1-xNdx)0.6Sr0.4Co0.8Fe0.2O3-δ体系双稀土阴极材料的氧化学扩散系数及电学性能的研究

采用固相反应法合成了(Pr1-xNdx)0.6Sr0.4Co0.8Fe0.2O3-δ(x=0.2、0.4、0.6、0.8)钙钛矿氧化物系样品,采用XRD分析物相结构,采用XPS分析化学状态,用电导弛豫法研究了(Pr1-xNdx)0.6Sr0.4Co0.8Fe0.2O3-δ系样品的氧化学扩散性能.实验结果表明,(Pr1-...     

Oxygen vacancy concentration variation, diffusivity and thermo-chemical stability of La0.2Ba0.8Co0.2Fe0.8O3−δ membranes

Perovskite type La_0.2Ba_0.8Co_0.2Fe_0.8O_3– (LBCF) powders were synthesized by modified citrate pyrolysis and LBCF membranes were prepared by isostatic pressing. The oxygen vacancy concentration variation of the LBCF powders becomes substantial above 973 K due to order-disorder transition. The unsteady-steady oxygen permeation flux of the LBCF membrane decreases with time and it takes about 40 min to get the steady state. In the temperature range of 1073–1223 K, the oxygen vacancy diffusivity of the LBCF membrane increases almost a magnitude and the increasing of oxygen permeation flux is mainly attributed to the increasing of oxygen vacancy diffusivity. An in-situ high-temperature X-ray diffraction was used to study the stability of the LBCF membrane, indicating that it has good thermochemical stability at elevated temperatures and low oxygen partial pressures.     

聚合物协助燃烧法合成La0.8Sr0.2Co0.5Fe0.5O3-δ纳米粉体

为开发新型高性能中温固体氧化物燃料电池阴极材料,以La、Sr、Co和Fe的硝酸盐、葡萄糖和丙烯酰胺为原料,在pH=8-10的碱性条件,通过聚合物协助燃烧法制备了La0.8 Sr0.2 Co0.5 Fe0.5 O3-δ(LSCF)钙钛矿相纳米粉体.用XRD、SEM和TEM表征了LSCF粉体的相结构和微观形貌,结果显示,在...     

Synthesis and properties of LnBaFeCoO5 + δ (Ln = Nd, Sm, Gd)

LnBaFeCoO_{5 + δ} (Ln = Nd, Sm, Gd) layered oxides have been synthesized and their crystal structure, thermal stability, thermal expansion, electrical conductivity, thermoelectric power, and magnetic susceptibility have been studied. The oxides have a tetragonal structure (sp. gr. P4/mmm) with unit-cell parameters a = 0.3909(2) nm and c = 0.7695(6) nm for Ln = Nd (δ = 0.65), a = 0.3908(3) nm and c = 0.7662(6) nm for Ln = Sm (δ = 0.37), and a = 0.3908(2) nm and c = 0.7613(6) nm for Ln = Gd (δ = 0.37). The LnBaFeCoO_{5 + δ} compounds are antiferromagnetic p-type semiconductors. With decreasing Ln³⁺ ionic radius, their electrical conductivity and linear thermal expansion coefficient decrease and their thermoelectric power and antiferromagnetic ordering temperature increase. Near 518–653 K, the linear thermal expansion coefficient of the LnBaFeCoO_{5 + δ} oxides increases from (12.9–16.6) × 10^?6 to (19.3–26.5) × 10^?6 K^?1, which is due to the release of weakly bound oxygen from the oxides. We have determined parameters of charge transport in the [Fe(Co)O₂] layers in the crystal structure of the LnBaFeCoO_{5 + δ} phases.     

Sol–gel synthesis,characterization and microwave absorbing properties of nano sized spherical particles of La0.8Sr0.2Mn0.8Fe0.2O3

LSMFO (La_0.8Sr_0.2Mn_0.8Fe_0.2O₃) nano sized powders were synthesized by modified EDTA assisted sol–gel synthesis using EDTA:metal ion = 0.5. Another new synthesis method, sol–gel self combustion using PVA, was also devised for the synthesis of LSMFO and the effects of the PVA mole ratio was investigated. The characterization techniques, XRD, FE-SEM, TG/DTA and ICP, confirmed the formation of the pure phase LSMFO by both the methods. The material attained spherical morphology instead of previously reported rod like structure. Sizes of synthesized powders vary from 14.5 nm to 23 nm. TG/DTA results suggest that LSMFO can be synthesized by the self combustion at temperatures as low as 200 °C. Synthesized LSMFO has excellent microwave absorbing properties in the range of 0.05–18 GHz and appreciable effective bandwidth, 2 GHz, with microwave absorption in excess of 10 dB and peak reflection loss of 25 dB which suggests that the materials can be used as effective microwave absorbers.     

K_2Ln(NO_3)_5·2H_2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长和热重-差热分析研究

本文生长出了K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd；Sm）的单晶，并对其进行了晶体结构及差热-热重分析研究．结果表明，K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd）的晶体属正交晶系，Fdd2空间群．首次生长出KPrN单晶并用直接法解出其晶体结构．解得KPrN的晶胞参数为：a=11．2210（10）,b=21．411（3），c=12．208（2）,Z=6；R=0．0240．对KLnN加热，则依次出现脱水、熔化、不可逆相变和NO的分解过程（K2Ce（NO3）5·2H2O除外）K2Ln（NO3）5·2H2O（Ln＝La；Nd；Sm）的NO分三步分解，K2Ln（NO3）5·2H。O（Ln=Ce；Pr）的NO分两步分解·KNO3和Ln（NO3）3·nH2O的混合物在225℃左右生成K2Ln（NO3）5     

Synthesis and Study of Uranates of Rare-Earth Elements of Compositions LnU3O10.5·6H2O (Ln = La,Ce, Pr,Nd, Sm), LnU6O19.5·10H2O (Ln = Nd,Sm, Eu,Gd, Tb,Dy), and LnU2O7.5 (Ln = Dy,Ho, Er,Tm, Yb,Lu)

Radiochemistry - The interaction of synthetic skupite UO3·2.25H2O with aqueous solutions of La, Ce, Pr, Nd, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu nitrates under hydrothermal conditions at a...