Internal dynamics of the LaI3 molecule. II. Thermal average structure of the molecule and mean square vibration amplitudes

The structural parameters of the effective r _g configuration of the LaI₃ molecule were calculated using the DFT/B3LYP method. The difference between the calculated values of r _e (La-I) and r _g (La-I) is mostly due to the anharmonicity of the ν₁ and ν₂ vibrations and does not exceed the error in determining the distance r _g (La-I) in the electron diffraction experiment. Inclusion of the anharmonicity of the ν₂ and ν₄ deformation vibrations in calculations leads to decreased amplitudes l(I…I) and shrinking effect δ(I…I) compared to the respective values obtained in the harmonic approximation. The LaI₃ molecule proved to be more rigid than predicted by B3LYP calculations.     

Electrophysical characteristics and stability of solid apatite-like electrolytes La x Si6O12 + 1.5x and La x Ge6O12 + 1.5x

Oxygen-ion conduction in apatite-like compounds based on silicates and germanates of lanthanum La _x A₆O_{12 + 1.5x} (A = Si, Ge; x = 9.11–10.22) is studied. The compounds are shown to be purely ionic conductors at 600–900°C and partial oxygen pressures 10^?16 to 10⁵ Pa. The electroconductivity of the best conducting specimens of La _x A₆O_{12 + 1.5x} (A = Si, Ge; x = 9.77–10) exceeds that of electrolyte YSZ at moderate temperatures. The electroconductivity of lanthanum germanate is substantially greater than that of lanthanum silicate, specifically, 7.85 × 10^?2 and 2.35 × 10^?2 S cm^?1, respectively, at 800°C. An inflection is discovered at ～750°C in the temperature dependences of electroconductivity of La _x Ge₆O_{12 + 1.5x} (x = 9.77–10.22). A dilatometric examination points to a second-kind phase transition that may be due to the oxygen sublattice disordering. The behavior of apatite-like electrolytes La _x A₆O_{12 + 1.5x} (A = Si, Ge) during long exploitation periods in the interval of working temperatures of electrochemical devices is studied for the first time ever. The electrolytes’ aging at 800°C in air for 1000 h was investigated by the electroconductivity method. The electroconductivity of lanthanum germanates decayed with time by 5% and that of lanthanum silicates, by 9.5%. The steady-state values of electroconductivity of all compounds studied is reached after 600–700 h. The compounds studied form a class of materials that hold some promise as solid electrolytes for medium-temperature fuel cells and other electrochemical devices.     

镧、铈及重金属元素铬、锌对竹叶眼子菜的毒害作用

研究了镧、铈及重金属元素铬、锌对高等沉水植物竹叶眼子菜(Potamogeton malaianus Miq.)的毒害作用. 结果表明, La3 , Ce3 , Zn2 在低浓度范围内, 均能诱导叶绿素、蛋白质合成, 但浓度过高时却对叶绿素、蛋白质起破坏作用;而Cr6 处理却使上述两指标随其浓度的升高逐渐降低. 4种离子对竹叶眼子菜的保护酶系统存在不同的影响, 低浓度条件下, 诱导过氧化氢酶(CAT)、过氧化物酶(POD)活性升高, 当污染加重时, 这两种酶的活性却随处理浓度的升高逐渐下降; 超氧化物歧化酶(SOD)活性变化与CAT、 POD相反, 它在低处理浓度情况下酶活下降, 随处理浓度的加大酶活诱导上升, 其活性变化趋势与·O-2 产生速率正好相反. 随4种离子处理浓度增高, MDA含量呈升高趋势, 并与4种离子的处理浓度之间皆呈极显著正相关. 4种离子的毒性强度依次为Cr6 >Ce3 >Zn2 >La3 . Cr6 对竹叶眼子菜的致死浓度为0.5～1 mg·L-1, Ce3 , Zn2 为3～5 mg·L-1 , La3 为7～10 mg·L-1. 镧、铈同重金属元素铬、锌对竹叶眼子菜的毒害机制相似.     

超细Ni-Cu-Co-La的制备及其催化乙腈加氢性能

以水合肼和硼氢化钾为共还原剂制备了四元合金催化剂Ni-Cu-Co-La,并将其应用于乙腈催化加氢反应.采用X射线衍射、X射线光电子能谱、透射电镜和H2程序升温脱附对催化剂进行了表征,考察了催化剂组分对乙腈选择性加氢制乙胺催化性能的影响.结果表明,Cu,Co和La的加入均不同程度地提高了催化剂的活性和选择性,在反应压力1.8 MPa,反应温度120℃,反应时间1 h的条件下,乙腈转化率和乙胺选择性分别为100%和98.24%,优于使用Raney Ni、非晶态Ni-B和Co-B合金催化剂时的结果.     

Nickel-cermet anode for fuel cells with the LSGM electrolyte

The effect of some technological parameters (firing temperature, thickness of an interphase layer made of solid electrolyte Ce_0.82Gd_0.18O_1.91 (GDC), the GDC electrolyte amount in nickel-cermet) on the electrochemical and electric properties of a nickel-cermet (Ni-GDC) anode intended for fuel cells with the La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 (LSGM) electrolyte is studied. The polarization resistance of such an electrode is shown to hardly depend on the thickness of the interphase layer (4.5–23.5 μm) and the GDC electrolyte amount in nickel-cermet and to increase with the anode firing temperature. It is established that the contact resistance is concentrated in cells with the developed nickel-cermet electrode at the GDC/LSGM interface. At a temperature of 700°C the developed anodes may ensure a current density of 1 A cm^?2 at an overvoltage of less than 100 mV when using both moist hydrogen and a methane-oxygen mixture as the fuel.     

熔盐电解合成希土六硼化物的研究——REBO3、LiBO2和LiF体系熔盐电解合成RER6

本文在800℃和空气中电解REBO₃-LiBO₂-LiF熔盐体系合成了单相的REB₆.石墨川埚兼作容器和阳极.耐火金属棒如Cu和Mo等被悬吊在电解质中作为阴极.根据似二元体系LiBO₂-LiF和LiBO₂-LaBO₃的低熔点组成以La₂O₃、B₂O₃、Li₂CO₃和LiF为原料找到了具有较低熔点的熔盐体系.根据X射线粉末衍射,该熔体是由REBO₃、LiBO₂和LiF三个物相组成.     

微乳液法制备超细K2Ln2Ti3O10及其光催化活性研究

以钛酸四丁酯、氢氧化钾和镧系金属氧化物为原料。采用微乳液法制备了系列超细K2Ln2Ti3O10（Ln=La．Ce,Pr．Nd，Sm，Eu，Gd）光催化剂。并考察了其光催化活性。通过X射线衍射（XRD）、透射电镜（TEM）和紫外可见吸收光谱（UV—Vis）对其进行了表征。结果表明：用微乳液法制备催化剂可以在较低的温度下（900℃），用较短的烧结时间（3h）合成结晶度高、粒径较小（200Mm）的K2Ln2Ti3O10钙钛矿型层状结构化合物。催化剂在紫外光和可见光条件下均具有光催化降解甲基橙的活性。紫外光条件下可以明显提高光催化降解活性，降解率达到60％。     

Complete Oxidation of Methane over Palladium Supported on Alumina Modified with Calcium,Lanthanum,and Cerium Ions

The activity and thermal stability of Pd/Al_2O_3 and Pd/(Al_2O_3 MO_x)(M=Ca,La,Ce) palladium catalysts in the reaction of complete oxidation of methane are presented in this study.The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide.Then they were impregnated with palladium nitrate solution.The catalysts with unmodified alumina had a high surface area.The activity and thermal stability of the alumina- supported catalyst was also very high.The introduction of calcium,lanthanum,or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method.These modifiers decreased the activity of palladium catalysts,and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al_2O_3.The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.     

介孔混合氧化物催化剂La-Co-Zr-O的制备与表征

 采用柠檬酸络合-有机模板剂分解法制备了(La+Co)/(La+Co+Zr)原子比为0.5的La-Co-Zr-O催化剂,并与传统的共沉淀法制备的La-Co-Zr-O催化剂进行比较. N2物理吸附结果表明,采用模板剂法制备的催化剂样品具有较大的比表面积(96.6～117.6 m2/g)和十分均匀的孔径(3.5～4.3 nm); X射线衍射、X射线光电子能谱和X射线吸收精细结构表征结果一致表明,催化剂中活性组分主要为高分散的Co3O4微晶(粒径为23～33 nm), 模板剂法制备的催化剂中所有组分的分散性均优于共沉淀法制备的催化剂. 程序升温还原实验结果表明,采用聚乙二醇辛基苯基醚与十六烷基三甲基溴化铵为混合模板剂制备的催化剂中Co3O4更容易被还原. Co-O 键的活动度与催化剂催化氧化反应的活性密切相关.