阳极负载型SOFC阳极基底厚度对性能的影响

制备不同厚度阳极负载型YSZ薄膜固体氧化物燃料电池 ,并对电池的极化、放电性能进行了测试 .结果表明 ,电池的性能明显受阳极性能的影响 ,阳极过电位大的原因之一是受多孔阳极气体扩散的影响 .降低阳极基底的厚度 ,阳极过电位明显减小 ,电池性能明显提高 .当阳极基底厚度为 0 .5mm时 ,在 80 0℃工作温度下 ,电池的功率密度达到 0 .1 9W·cm- 2 ,较之阳极厚度为 1 .0mm的电池性能提高近 1 .5倍 (0 .1 3W·cm- 2 ) .     

Microstructure of yttric calcium phosphate bioceramic coatings synthesized by laser cladding

The yttric calcium phosphate (CaP) coatings were in situ prepared on pure titanium substrate by laser cladding. The morphologies and phases constitution of CaP coatings were studied by electron probe microanalysis, X-ray diffraction and so on. The bonding state between the coating and the substrate is fine metallurgical combination, and the addition of yttria can fine the structure and increase the tensile strength of the coatings. The X-ray result shows that the coating is composed of the phases of HA, α-Ca₂P₂O₇, β-Ca₂P₂O₇ and CaTiO₃.     

Characterization of laser sealed coatings of yttria partially stabilized zirconia

The present paper reports an experimental investigation based on X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and wavelength dispersive spectroscopy (WDS) analyses of phases formed after laser sealing of plasma sprayed coatings of 8.5 wt% yttria partially stabilized zirconia (YPSZ). X-ray diffraction and X-ray step-scanning analyses showed that the plasma sprayed and sealed coatings consisted mainly of t′ phase with a very small amount of monoclinic phase (m phase) in the plasma sprayed coatings. It was also found that the small amounts of m and cubic phases (c phase) present in the sealed coatings were dependent on laser processing specific energies (specific energy is equal to laser power/traverse speed x beam diameter). It was also found that rhombohedral (r) phase formed after laser sealing of coatings at higher specific energies. A direct relationship between c/a ratio of transformable tetragonal phase (t phase) produced by thermal treatment of sealed coatings and nontransformable tetragonal phase (t′ phase) and the amount of Yttria was obtained. A new equation was derived, which describes the relationship between Yttria concentration and the c/a ratio of tetragonal phases (t or t′).     

Polysiloxane coatings on microspheres based on Multiphase Flow with Interface Exchange-Discrete Element Modelling

Polysiloxane coatings on yttria stabilized zirconia (YSZ) microspheres of 500 μm were simulated in a spout fluidized bed coater using Multiphase Flow with Interface Exchange-Discrete Element Modelling (MFiX-DEM). Two different coater configurations were developed to study the influence of gas velocity and its distribution on particle dynamics. The presence of the Wurster tube not only enhances the distribution but also increases the overall residence time of the particles. Investigations were also carried out with different Wurster tube positions (normal, 10% and 20% lowered from its initial position). Among these, 20% lowered Wurster tube position demonstrated the most effective coating process. The effects of gas inlet pressure on the average gas velocity and the distribution of particles were analyzed. More than 97% of the particles can be retained. The derived results, including average gas velocity, particle retention percentage, and distribution of particles with gas velocity, are being used to guide the experimental work in obtaining defect-free coatings for YSZ microspheres.     

Performance of double layer electrolyte cells Part I: Model behavior

The present work reports on the estimated performance of double layer electrolyte based cells, including one yttria stabilized zirconia (YSZ) electron blocking layer. In order to evaluate the impact of the relative magnitude of the materials properties on the cell performance, a range of electrical properties has been considered, taking YSZ as reference. At constant temperature, the open circuit voltage, the oxygen permeability and the oxygen partial pressure profiles in such two layer electrolyte cells are related to the materials ionic and electronic transport properties, layers thickness and overall cell oxygen partial pressure boundary conditions. The effectiveness of the electron blocking characteristics of YSZ layers is demonstrated for a variety of materials, but consideration of the exact electrical properties (the n-type but also the p-type and ionic conductivities) of the second electrolyte layer is shown to be a fundamental requirement for proper design of such cells.     

Cavitation-assisted decontamination of yttria from graphite of different densities

Yttria coated graphite crucibles are widely used to handle molten refractory and radioactive metals like uranium and plutonium. However, the coated layer suffers damages like cracking and peeling off owing to thermal cycles. As a result, removal of the yttria layer from the graphite surface is essential to ensure reuse of the crucible and minimization of radioactive waste. The present work investigates intensified dissolution of yttria from the coated graphite samples using ultrasound as a non-destructive decontamination technique to recycle the graphite substrate. The optimum conditions established for maximum dissolution were 8 M as acid strength, frequency of 30 kHz, temperature of 45 °C and power density of 8 W cm⁻² that resulted in maximum dissolution of 52% in 30 min. Use of an oxidant H₂O₂ to the acid, did not yield any improvement in the dissolution kinetics, instead, increased oxidation of the graphite substrate was observed, leading to the anomalous weight gain of the graphite substrate despite surface erosion. Effect of ultrasound on the dissolution was pronounced, with almost a threefold increase compared to dissolution performed under silent conditions. Rates of dissolution of yttria from the substrate of different densities and pore size distribution were also studied. The dissolution was slowest from graphite of density 1.82 g cm⁻³ as the pore size distribution was conducive to accommodate the yttria particles. The dissolution in nitric acid followed ash layer diffusion controlled kinetics. The study has demonstrated the efficacy of application of ultrasound for accelerated decontamination of graphite substrates.     

Short-time reactor neutron irradiation of YSZ prepared using reactive calcination method

The present work is devoted to study the short-time reactor neutron irradiation of yttria stabilised zirconia (YSZ) at 315 K. The samples were prepared by the reactive calcination method and characterised by X-ray diffraction (XRD) analysis and scanning electronic microscope. The prepared samples were irradiated by reactor neutrons at different exposure times and investigated by XRD analysis. The results obtained show good radiation resistance of YSZ to reactor neutron irradiation.     

Theoretical Aspects on Doped-Zirconia for Solid Oxide Fuel Cells: from Structure to Conductivity

Solid oxide fuel cells (SOFCs) are regarded to be a key clean energy system to convert chemical energy (e.g. H₂ and O₂) into electrical energy with high efficiency, low carbon footprint, and fuel flexibility. The electrolyte, typically doped zirconia, is the "state of the heart" of the fuel cell technologies, determining the performance and the operating temperature of the overall cells. Yttria stabilized zirconia (YSZ) have been widely used in SOFC due to its excellent oxide ion conductivity at high temperature. The composition and temperature dependence of the conductivity has been hotly studied in experiment and, more recently, by theoretical simulations. The characterization of the atomic structure for the mixed oxide system with different compositions is the key for elucidating the conductivity behavior, which, however, is of great challenge to both experiment and theory. This review presents recent theoretical progress on the structure and conductivity of YSZ electrolyte. We compare different theoretical methods and their results, outlining the merits and deficiencies of the methods. We highlight the recent results achieved by using stochastic surface walking global optimization with global neural network potential (SSW-NN) method, which appear to agree with available experimental data. The advent of machine-learning atomic simulation provides an affordable, efficient and accurate way to understand the complex material phenomena as encountered in solid electrolyte. The future research directions for design better electrolytes are also discussed.     

Oxygen detection using yttria-stabilized zirconia thin films doped with platinum

Yttria stabilized zirconia (YSZ) thin films are obtained using both spray-pyrolysis and dip-coating. The ability of YSZ films incorporated with platinum nanospecies (Pt-YSZ) to detect oxygen is compared with that of pure YSZ thin films using a new experimental setup. With this system, the surface electrical resistance of the films as a function the oxygen content is measured at a fixed temperature. In addition, the effects of thermal annealing on the oxygen sensitivity of the films are observed. Platinum doped samples, Pt-YSZ, show different kinetics of carrier diffusion as compared to pure YSZ samples.     

电化学方法在钛表面制备Co-YSZ/HAp纳米复合涂层

采用复合电沉积和电泳沉积两步法在钛基体上制备了Co-YSZ/HAp纳米复合涂层, 与只采用电泳沉积法在钛基体上制备纳米HAp单一涂层进行了比较研究.采用场发射扫描电镜、X 射线衍射和能量散射谱对复合涂层的微观形貌, 纳米HAp外层表面形貌, 晶相, 复合涂层的断面形貌及元素组成分布进行分析研究. 通过粘结-拉伸实验测定了涂层与基体的结合强度, 结果表明, Co-YSZ/HAp 纳米复合涂层与钛基体的结合强度明显高于纳米HAp 单一涂层与钛基体的结合强度, 说明复合涂层具有更好的力学性能.