CeO2在氧化催化反应中的作用

从CeO2 所属的萤石型氧化物结构特点出发 ,对CeO2 内部的电子缺陷、氧离子及其空穴等在催化氧化中的作用进行分析 ,指出CeO2 在氧化催化剂中所起的修饰作用与它的价态变化———Ce4 /Ce3 间的转换 ,以及CeO2 与Cu等过渡金属之间的相互作用密切相关。更重要的是 ,此类催化体系 (如Cu CeO2 )是具有较高的电子 离子混合导电能力的混合型导体 ,且CeO2 易于存储、传输氧 ,可以协助O2 -从电解质向阳极传递 ,将阳极氧化反应面扩大至TPB面以外 ,减小界面阻力 ,加快氧化反应速率。此特性使其在以甲烷为燃料的固体电解质燃料电池阳极开发领域成为一种值得关注的备选材料。     

放射性固体废物玻璃固化技术综述

阐述了放射性固体废物玻璃固化技术的原理与优势,综合分析了国外玻璃固化装置,包括燃料式熔炉、焦耳加热熔炉、感应加热熔炉、等离子体炬和电弧(等离子体弧)熔炉等反应器的结构、工作原理及其优缺点。提出等离子体熔炉较冷坩埚感应熔炉更适合于核电厂处理低、中放射性固体废物。     

Mixed Electronic-Ionic Conductivity of Cobalt Doped Cerium Gadolinium Oxide

The effect of small amounts (<5 mol %) of cobalt oxide on the electrical properties of cerium oxide solid solutions has been evaluated. Ce_0.8Gd_0.2O_2-x (CGO) powder with an average crystallite size of 20 nm served as a model substance for the electrolyte material with a high oxygen ion conductivity and low electronic conductivity in its densified state. Doping the CGO powder by transition metal oxides (MeO) with concentrations below 2 mol % did not change the ionic conductivity nor the electrolytic domain boundary. After long sintering times (2 h) at temperatures above 900°C, MeO and CeO₂ form solid solutions. However, short sintering times or high dopant concentrations lead to an electronic conducting grain boundary phase short circuiting the ionic conductivity of the CGO grains. Choosing proper doping levels, sintering time and temperature allows one to tailor mixed conducting oxides based on CGO. These materials have potential use as electrolytes and/or anodes in solid oxide fuel cells and ion separation membranes.     

LaGaO3基固体电解质的研究进展

综述了具有较高氧离子电导率的掺杂钙钛矿型LaGaO3基固体电解质近年来的研究进展.总结了通过掺杂和制备工艺改进,提高电解质在离子导电性、机械性能和稳定性方面的新成果.     

Ion dynamics in solid electrolytes for lithium batteries

All-solid-state batteries with ceramic electrolytes and lithium metal anodes represent an attractive alternative to conventional ion battery systems. Conventional batteries still rely on flammable liquids as electronic insulators. Despite the great efforts reported over the last years, the optimum solid electrolyte has, however, not been found yet. One of the most important properties which decides whether a ceramic is useful to work as electrolyte is ionic transport. The various time-domain nuclear magnetic resonance (NMR) techniques might help characterize and select the most suitable candidates. Together with conductivity measurements it is possible to analyze ion dynamics on different length-scales, i.e., to differentiate between local, within-site hopping processes from long-range ion transport. The latter needs to be sufficiently fast in the ceramic, in the best case competing with that of liquid electrolytes. In addition to conductivity spectroscopy, NMR can help understand the relationship between local structure and dynamic parameters. Besides information on activation energies and jump rates the data also contain suggestions about the relevant elementary steps of ion hopping and, thus, diffusion pathways through the crystal lattice. Recent progress in characterizing ion dynamics in ceramic electrolytes by NMR relaxometry will be briefly reviewed. Focus is put on presently discussed solid electrolytes such as garnets, phosphates and sulfides, which have so far been studied in our lab.     

Electrodiffusion Model Simulation of Ionic Channels: 1D Simulations

The drift-diffusion (Poisson-Nernst-Planck) model is applied to ionic channels in biological membranes plus surrounding solution baths. Simulations of the K channel in KCl solutions using the TRBDF2 method are presented which show significant boundary layers at the ends of the channel. The computed current-voltage curve for the K channel shows excellent agreement with experimental measurements.     

Silicon nanopores as bioelectronic devices: a simulation study

Solid-state aqueous pores of nanoscale dimensions are now a reality, thanks to the advancing fabrication techniques. The interest in such devices has been high in the last decade, due to their potential as molecular sensing elements (Kirby and Hasselbrink in Electrophoresis 25(2):187–202, 2004) and in fast DNA sequencing (Smeets et al. in Nano Lett. 6(1), 2006). This work focuses on the theoretical characterization and numerical modeling of the role of oxidated surface electric charge in the ionic conduction process through man-made silicon nanopores. We have extended the model presented in (Behrens and Grier in J. Chem. Phys. 115(14), 2001) by including potassium adsorption on the oxidated silicon (silica) surface, as well as taking the cylindrical curvature of the surface into account. Being able to calculate the surface charge density, we have used a particle-based Brownian dynamics simulation tool to characterize the ionic population in nanopores and simulate conduction through nanopores at various bulk electrolyte concentrations.     

中低温SOFC电解质材料研究新进展

综述了近年来国内外用于中低温固体氧化物燃料电池的CeO2基、Bi2O3基、钙钛矿类和磷灰石类电解质材料的研究进展和发展趋势,分析了对电解质性能产生影响的因素,指出了今后研究中亟待解决的问题,讨论了颇受关注的低温下具有低活化能和高氧离子电导率的磷灰石类新型电解质材料。     

Experimental31p nmr study of the influence of ionic strength on the apparent dissociation constant of mgatp

The classical method for³¹P NMR determination of intracellular free magnesium concentration ([Mg _free ²⁺ ]) requires an accurate knowledge of the apparent dissociation constant (K _D ) of MgATP. There is a large difference between the previously determined values ofK _D . Although the value of 50 µM, determined by a³¹P NMR method, is now largely accepted, a value of 86 µM has more recently been measured with a fitting method derived from the original one, and with a different ionic strength. The purpose of our study was to assess if the cause of the difference between these two previously reportedK _D values was due to the measuring method or to the ionic strength value used.Working at pH=7.2,T=37°C, and [KCl]=0.25 M, we performedK _D measurements with the original³¹P NMR method and with the fitting method. The results (67±13 µM and 61±20 µM, respectively) were not significantly different. Then, with the first method, we measured K_D at [KCl]=0.12 M and found a value of 19±5 µM. We conclude that the main cause of difference between theK _D values measured by³¹P NMR reside in the disparity of ionic strength values used for their measurement. OurK _D measurements at [KCl]=0.25 and 0.12 M demonstrate the importance of the ionic strength value used for imitating the intracellular medium on the absolute value of ([Mg _free ²⁺ ]) measured by³¹P NMR spectroscopy.Address for correspondence: Université Catholique de Louvain, Unité CPMC, Bâtiment Lavoisier, Place Louis Pasteur n°1, B-1348 Louvain-la-Neuve, Belgium. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Penn Plaza, New York, NY 10119.     

Ti1.0Mn0.9V1.1基合金的微观结构和电化学性能

“与Laves相相关的BCC固溶体”是一个新概念,由此发展起来的新型钛基BCC合金贮氢能力已经达到了2.2%(质量分数)。Akiba等用TEM(透射电子显微镜)方法观测TiMnV合金的BCC相和C14相的交界面,发现存在一个厚度为10 nm的薄层。通过EDX(电子探针X射线显微分析)方法观测,这个薄层物质的组成为Ti1.0Mn0.9V1.1,但是Ti1.0Mn0.9V1.1却不具备电化学活性。在此基础上,从Ti1.0Mn0.9V1.1出发,通过组成元素的部分取代,使储氢性能优良的Ti1.0Mn0.9V1.1具有电催化活性,对Ti1.0Mn0.9V1.1系合金的结构和电化学性能进行研究,Ti1.0Mn0.9V1.1系合金有可能成为MH-Ni蓄电池潜在的高温负极材料。     

La_(1-x)Na_xMnO_3室温巨磁电阻增强效应

采用固相反应法制备了一系Ｌａ_(１－ｘ)Ｎａ_ｘＭｎＯ_３多晶样品。研究了样品的微结构、磁电阻、磁化强度以及居里温度等性质。发现随着Ａ位平均离子半径＜ｒ_Ａ＞的减小,样品的居里温度下降,磁电阻增大。另外,实验还发现了磁电阻与磁化强度之间有着密切的联系。     

硫化物固态电解质的研究进展及产业应用

全固态电池具有较高的能量密度和安全性能,是解决电动汽车、便携电子产品的安全和续航的重要手段。作为全固态电池中的关键组分,固态电解质的电化学性能和稳定性影响整个固态锂离子电池的发展。本文以硫化物固态电解质的室温电导率为切入点,系统分析目前研究较为广泛的LGPS、LPS体系硫化物固态电解质的结构、制备方法及材料的稳定性,并对硫化物固态电解质在全固态电池设计和应用做了一点思考,指出未来的发展方向。     

The contribution of field-induced morphological change to the electrical aging and breakdown of polyethylene

A brief review of the early literature is given which provides evidence that electrically-induced mechanical stresses make an important contribution to the electrical breakdown of solid dielectrics. Special attention is given to polyethylene and the manner in which this semi-crystalline polymer yields under mechanical stress by microvoid, crack and craze development in the amorphous phase between the lamellar crystallites. The nature of the forces induced by an electrical field is considered and it is shown that a significant component of tensile stress is generated in a direction orthogonal to the field and can become large as breakdown is approached. This suggests a correlation between the responses of the polymer to mechanical and electrical stresses and consequently the importance of morphology in determining the latter. The likely effect of field-induced morphological change on charge transport and electrode processes is described and its underlying contribution to possible aging markers for polyethylene, such as high field conduction, electroluminescence, space charge and charge packets is considered.     

固体氧化物燃料电池电解质材料的研究进展

介绍了固体氧化物燃料电池(SOFC)用萤石型、钙钛矿型及磷灰石型电解质材料的结构、导电机理、性能及研究进展。存在的离子电导率较低、化学组成及相组成不稳定等问题,主要通过氧化物共掺杂及不同材料之间的复合等方法来改善。材料的复合与电解质层结构的设计,将成为电解质研究的主要方向。     

P-Type Electronic Transport in Ce0.8Gd0.2O2 − δ: The Effect of Transition Metal Oxide Sintering Aids

Small (2 mol%) additions of cobalt, iron and copper oxides into Ce_0.8Gd_0.2O_{2 –} considerably improve sinterability of ceria-gadolinia (CGO) solid electrolyte, making it possible to obtain ceramics with 95–99% density and sub-micron grain sizes at 1170–1370 K. The minor dopant additions have no essential effect on the total and ionic conductivity, whilst the p-type conduction in the transition metal-containing materials at 900–1200 K is 8–30 times higher than that in pure CGO. The oxygen ion transference numbers of the Co-, Fe- and Cu-doped ceramics, determined by the modified e.m.f. technique under oxygen/air gradient, are in the range 0.89–0.99. The electron-hole contribution to the total conductivity increases with temperature, as the activation energy for ionic conduction, 78 to 82 kJ/mol, is significantly lower than that for the p-type electronic transport (139–146 kJ/mol). The results show that CGO sintered with such additions can still be used as solid electrolytes for intermediate-temperature electrochemical applications, including solid oxide fuel cells (SOFCs) operating at 770–970 K, but that increasing operation temperature is undesirable due to performance loss.     

Charge Compensation Mechanisms in La-Doped BaTiO3

The mechanism of doping BaTiO₃ with La has been investigated by a combination of X-ray diffraction, electron probe microanalysis, scanning and transmission electron microscopy and impedance measurements. Phase diagram results confirm that the principal doping mechanism involves ionic compensation through the creation of titanium vacancies. All samples heated in oxygen at 1350–1400°C are electrical insulators, consistent with an ionic compensation mechanism. Samples heated in air or atmospheres of low oxygen partial pressure, at similar temperatures, lose a small amount of oxygen and this gives rise to a second, electronic compensation mechanism in addition to the main, ionic compensation mechanism; as a result, samples are dark-coloured and semiconducting. The change from insulating to semiconducting behaviour is reversible, by changing the atmosphere on heating at 1350–1400°C. We find no evidence for any changes in cationic composition of the BaTiO₃ solid solutions arising from changes in oxygen content.     

Defect-Property Correlations in Garnet Crystals. *VII: The Electrical Conductivity and Defect Structure of Yttrium Aluminum and Yttrium Iron Garnet Solid Solutions

The conduction mechanisms in yttrium aluminum and yttrium iron garnet solid solutions have been studied as a function of temperature, iron concentration and partial pressure of oxygen. At low concentrations of iron, ac conductivity and ionic transference measurements show the solid solution to be a mixed ionic-electronic conductor with an ionic mobility characterized by an activation energy of 2.6–2.8eV and a p-type electronic conductivity with activation energy of 3.0–3.3eV. High concentrations of iron cause a dramatic increase in the electrical conductivity connected with the formation of an Fe impurity band found to lie 1.9eV below the conduction band. Transport through this band is via an activated hopping process with an activation energy of 0.7eV for 6 fraction percent Fe. A defect model is presented which is consistent with our experimental observations including the conductivity maxima obtained at high PO₂'s for high Fe levels.     

垃圾处置发电新技术及其应用

陈述了传统的垃圾处置三种方法,特别是直接焚烧所存在的问题,介绍了垃圾处置的厌氧分级快速发酵和等离子气化技术的原理和应用,以达到垃圾的无害化、减量化和资源化处理目标。对利用垃圾进行发电的热力循环形式进行了讨论,为垃圾的清洁利用提供有效的途径。     

Electron-Ion Transport in ZrO2-Y2O3-CeO2 Ceramics

Simultaneous conduction of oxide ions and electrons in solid ceramic systems provides the capability for oxygen transport under a concentration gradient without the need for an externally applied electric field. In the present study, ionic transference numbers have been measured in the ZrO₂-5.8%Y₂O₃-10%CeO₂ system by open circuit Emf measurements involving different metal/metal oxide electrodes. In order to correlate the ionic transference number with grain size, high-density ceramic discs of different grain sizes (50 nm–5 m) were prepared by sintering pressed powders at various temperatures and times. Hydrothermal synthesis was used to prepare nanocrystalline powders of the above material with uniform crystallite size (10 nm) and chemistry. Emf measurements on the samples suggested both ionic and electronic transport, the ionic transference number decreasing with increase in the grain size. This observation was attributed to an increase in the amount of continuous crystalline grain boundary phase in the ceramics as the grain size increased. The presence of crystalline silicate and zirconate phases in the grain boundary region was confirmed by electron microscopic imaging combined with microanalysis. In the large grain (5 m) ceramics, the ionic transference number decreased linearly with temperature. As the grain size decreased, a maximum occurred in the ionic transference number vs. temperature curve. This maximum became more pronounced at smaller grain sizes. Better grain-grain contact and the doping effect of trivalent Ce in the grain boundary core are proposed to explain this observation.     

Lagrangian particle‐based simulation of fluid–solid coupling on graphics processing units

Lagrangian particle method has been widely used in computer physics and graphics; however, numerically solving the partial differential physical equation on a great number of particles is a computationally complex task. In this paper, a unified particle method on graphics processing units is proposed to simulate fluid–solid interaction with large density ratio interactively. Motivated by microscopic molecular dynamics, we consider the solid object as a particular fluid limited to solid motions; therefore, fluid–solid interaction as well as solid–solid interaction could be solved directly using multiphase weakly compressible smoothed particle hydrodynamics solvers. And then, we present a momentum‐conserving particle collision handling scheme to prevent fluid penetrating into solid objects. In the simulation, a measure of particle densities is used to handle density discontinuities at fluid–solid interfaces, and consequently, new formulations for density‐weighted inter‐particle pressure and viscous forces are derived. Moreover, to realistically simulate various small‐scale interaction phenomena such as water droplets flowing on solids’ surfaces, a surface tension model that uses density‐weighted color gradient and can obtain a stable and accurate surface curvature is employed to capture the interfacial fluid–solid tensions. Because all of the computation is carried out on graphics processing unit and no CPU processing is needed, the proposed algorithm can exploit the massive computational power of graphics processing unit for interactive simulation with a higher particle resolution. The experiment results show that our method can simulate realistic fluid–solid couplings at interactive frame‐rates even for up to 126 k particles. Copyright © 2014 John Wiley & Sons, Ltd.