Sol-gel synthesis and characterization of yttria stabilized zirconia membranes

Mesoporous yttria stabilized zirconia (YSZ) membranes can be used as supports for ultrathin dense ceramic or metallic membranes, and for ultrafiltration (UF) applications in harsh environments. This paper reports synthesis and characterization of sol-gel derived UF YSZ membranes. 0.25 M zirconia sol was prepared by hydrolysis and condensation of zirconium n-propoxide. A solution-sol mixing method was used to dope 8 mol% yttria in zirconia. Supported YSZ membranes were prepared by dip-coating the yttrium doped zirconia sol on the porous α-alumina substrate, followed by drying and calcining under controlled conditions. The membranes prepared in this study are of cubic fluorite phase. Helium permeation experiments show that the supported membranes are pin-hole (or crack) free. The 5 time dip-coated membrane determined by SEM micrograph is about 3.5 μm in thickness, with an average pore diameter of 3 nm.     

PCVD法制备ZrO~2和YSZ薄膜

以金属β-二酮类有机螯合物Zr(DPM)~4和Y(DPM)~3为挥发性源物质, 采用微波等离子体化学气相淀积法于较低的温度下(420～560℃)成功地在多孔α-Al~2O~3陶瓷,非晶玻璃等衬底上制备出致密的ZrO~2和YSZ薄膜材料.XRD分析结果表明,纯ZrO~2薄膜中除了单斜相外还存在着亚稳态的四方相.当掺入的Y~2O~3 摩尔百分含量大于或等于7%时,ZrO~2完全被稳定成立方相.SEM观察表明, 在等离子体内的不同区域中生成的薄膜形貌有所不同.XPS检测了YSZ薄膜中Zr3d~5~/~2和Zr3d~3~/~2 的电子结合能,发现较ZrO~2的标准值低0.7eV.由TEM观察和由XRD衍射峰半宽度计算, 所制备的ZrO~2和YSZ薄膜中微晶粒径在10nm左右     

Preparation and characterization of three-dimensionally ordered macroporous yttria-stabilized zirconia by aqueous organic gel route

Three-dimensionally ordered macroporous (3-DOM) yttria-stabilized zirconia (YSZ) was prepared by aqueous organic gel method through the interstitial spaces between polystyrene spheres assembled on glass substrates. The morphologies and pore size of the porous YSZ were characterized by scanning electron microscope (SEM) and nitrogen adsorption. The thermal behavior, the phase and chemical composition of PS/YSZ composite were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that porous YSZ has been formed with the pores arranged in an ordered close-packed three-dimensional structure. Ni/YSZ cermet was also prepared by immersing the 3-DOM YSZ into the solution of nickel nitrate and urea. The electrical conductivity of Ni/YSZ was about 400 S cm⁻¹ between 600 and 800 °C.     

乙醇在Ni-ZnO-ZrO_2-YSZ阳极SOFC上的发电性能

为考察乙醇用于固体氧化物燃料电池的可行性,用柠檬酸溶胶-凝胶制备阳极催化材料Ni-ZnO-ZrO2,利用机械混合法制备Ni-ZnO-ZrO2-YSZ(Y2O3稳定的ZrO2)阳极。用涂覆法,在YSZ电解质上,制备了Ni-ZnO-ZrO2-YSZ/YSZ/LSM(La0.85Sr0.15MnO3)与Ni-YSZ/YSZ/LSM的单体电池。在不同蒸发器操作温度、电池操作温度和乙醇蒸气流量下,以乙醇为燃料进行发电实验,对两种阳极的电池发电性能进行比较。实验结束后,用SEM检测了两种电池阳极的表面。结果表明,Ni-ZnO-ZrO2-YSZ阳极SOFC的电池输出性能明显高于Ni-YSZ阳极,且Ni-ZnO-ZrO2-YSZ阳极具有较好的抗积炭能力。     

掺钇锆醇盐水解Sol-Gel的物化过程及其机理

醇盐水解法广泛用于金属氧化物溶胶-凝胶的制备．一般，醇盐水解有二种方式，一是通过金属醇盐的完全水解、生成沉淀、继而胶溶形成溶胶；另一种是通过控制水解直接制得溶胶或凝胶．其中，由于醇盐控制水解法成胶容易，胶凝时间可以通过控制参数进行调节，所得胶粒细小均匀，因     

Remarkable Enhancement of O2 Activation on Yttrium‐Stabilized Zirconia Surface in a Dual Catalyst Bed

Yttrium‐stabilized zirconia (YSZ) has been extensively studied as an electrolyte material for solid oxide fuel cells (SOFC) but its performance in heterogeneous catalysis is also the object of a growing number of publications. In both applications, oxygen activation on the YSZ surface remains the step that hinders utilization at moderate temperature. It was demonstrated by oxygen isotope exchange that a dual catalyst bed system consisting of two successive LaMnO₃ and YSZ beds without intimate contact drastically enhances oxygen activation on the YSZ surface at 698 K. It can be concluded that LaMnO₃ activates the triplet ground‐state of molecular oxygen into a low‐lying singlet state, thereby facilitating the activation of the O₂ molecule on the YSZ oxygen vacancy sites. This phenomenon is shown to improve the catalytic activity of the LaMnO₃‐Pd/YSZ system for the partial oxidation of methane.     

Lanthanide transport in stabilized zirconias: interrelation between ionic radius and diffusion coefficient

The diffusion of all stable lanthanides was measured both in calcia stabilized zirconia (CSZ) and in yttria stabilized zirconia (YSZ) in the temperature range between 1,286 and 1,600 degrees C. The lanthanide diffusion coefficients obtained increase with increasing ionic radius. The experimental activation enthalpy of diffusion is near 6 eV for CSZ and between 4 and 5 eV for YSZ and is not strongly affected by the type of lanthanide. The results were correlated with defect energy calculations of the lanthanide diffusion enthalpy using the Mott-Littleton approach. An association enthalpy of cation vacancies with oxygen vacancies of about 1 eV (96 kJ/mol) was deduced in the case of CSZ, while there is no association in the case of YSZ. Furthermore, the change in diffusion coefficients can be correlated to the interaction parameter for the interaction between the lanthanide oxide with zirconia: The higher the interaction parameter, the higher the lanthanide diffusion coefficient.     

Two-Layer Fuel Cell Electrolyte Structure by Sol-Gel Processing

Thin layers of yttria-stabilized zirconia (YSZ) at 11 mol% Y₂O₃ doping level was deposited on a sintered disk of Y₂O₃ doped ceria electrolyte by spin-coating from an alkoxide solution. Dense sintered films were obtained by heat-treatment at 600°C. Open circuit voltage (OCV) was measured across the disk in a fuel cell mode with hydrogen fuel on the ceria side and pure oxygen on the YSZ side. Marked improvement of OCV was obtained on the two-layer electrolyte structure with the sol-gel YSZ film.     

TiO2修饰La0.6Sr0.4Co0.2Fe0.8O3-δ用于中温固体氧化物燃料电池的阴极

纳米TiO2修饰的La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)阴极被直接应用于YSZ电解质电池上. TiO2可阻止LSCF和YSZ间的化学反应,抑制SrZrO3的形成. LSCF-0.25 wt% TiO2阴极电池在0.7 V和600°C下的电流密度是LSCF阴极电池的1.6倍.电化学阻抗谱结果表明, TiO2修饰显著加快了氧离子注入电解质的过程,这可能与TiO2抑制了阴极/电解质界面处高电阻SrZrO3层的形成有关.本文为在ZrO2基电解质上使用高性能的(La,Sr)(Co,Fe)O3阴极材料提供了一种简单有效的方法.     

Nanostructured oxide-based powders: investigation of the growth mode of the CeO2 clusters on the YSZ surface

CeO(2)/YSZ nanocomposite powders, characterized by increasing Ce/Zr atomic ratio, were obtained by depositing, by wet impregnation, different amounts of CeO(2) on the yttria-stabilized zirconia (YSZ) surface. These powders were characterized by means of X-ray photoelectron spectroscopy, transmission electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Experimental results allow us to obtain interesting information concerning the growth mode, the morphology, and the dimensions of the CeO(2) clusters on the YSZ supporting surface. A 3-D growing mechanism was observed for the CeO(2) nanoparticles. With increasing Ce/Zr atomic ratio the CeO(2) clusters become more and more spherical. Moreover, XPS data also show the presence of Ce(III) and Ce(IV) ions at the interface supported/supporting oxides.     

On the influence of strain on ion transport: microstructure and ionic conductivity of nanoscale YSZ|Sc2O3 multilayers

Multilayer samples of the type (YSZ|Sc2O3) × n with layer thicknesses between 8 nm (n=100) and 250 nm (n=5) were prepared on (0001) sapphire substrates by pulsed laser deposition (PLD). The samples were characterised using X-ray diffraction (XRD), scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM/HRTEM, SAED (selected-area electron diffraction) and quantitative EELS (electron energy-loss spectroscopy)). The polycrystalline layers show a columnar microstructure, which is typical for the used preparation technique. The layers are highly textured and only one axial orientation relation is found between yttria-stabilised zirconia (YSZ), scandium oxide and the substrate: (0001) Al2O3‖(111) Sc2O3‖(111) YSZ. A preferred orientation relationship also exists for the azimuthal rotation of the crystallites, which was demonstrated by SAED, XRD pole figure measurements and fast Fourier transformation (FFT) of HRTEM micrographs. The interfaces between YSZ, Sc2O3 and the substrate are sharp and do not contain diffuse transition regions. Dislocations appear not to be arranged in regular arrays. With increasing interface density (thinner individual layers in the multilayer), the conductivity of the multilayers decreases. We relate this to the negative nominal misfit present at the YSZ|Sc2O3 interfaces (compressive stress in YSZ at the phase boundaries). This observation agrees well with the previously investigated case of YSZ|Y2O3 (A. Peters et al., Phys. Chem. Chem. Phys., 2008, 10, 4623), where tensile misfit strain was present in YSZ at the phase boundaries, leading to a conductivity increase.     

Synthesis and Characterization of Yttria-Stabilized Zirconia (YSZ) Nano-Clusters for Thermal Barrier Coatings (TBCs) Applications

Yttria-stabilized zirconia (YSZ) nano-clusters were synthesized by a sol–gel process. The aim was to produce YSZ powders in order to prepare thick coatings for thermal barrier to be applied on gas turbine engine components. Yttrium nitrate hexahydrate and zirconium oxy-chloride octahydrate were used as a source of zirconium, citric acid was taken as a chelating agent, and ethylene glycol was used as a polysterification agent. The synthesized powders were characterized by X-ray diffraction, transmission electron microscopy, thermo-gravimetric analysis and differential scanning calorimetry, and Raman spectroscopy. Furthermore, parameters were critically analyzed in order to synthesize non-transformable (t′) tetragonal crystal structure, which is the best zirconia phase for high temperature thermal barrier coatings applications. In this regard, tetragonal YSZ nano-clusters were heated in an alumina crucible at a temperature of 1200 °C for 100 h.     

In situ analytical electron microscopy studies of redox reactions at a YSZ/Pt interface

Redox reactions were studied at a single yttria-stabilized zirconia (YSZ)/Pt electrode interface, in parallel with pure YSZ with no catalyst electrode, by in situ analytical electron microscopy at elevated temperatures and in an oxygen atmosphere. In situ electron holography showed that the oxide underwent reduction at elevated temperatures in a vacuum and was consequently reoxidized upon exposure to an oxygen flux at the same temperature. In situ energy loss spectroscopy measurements were in agreement with in situ electron holography observations and indicated that the oxidation state of the host cation zirconium was altered in the reduced state of the YSZ to the metastable state Zr(3+).     

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.     

Influence of cathode functional layer composition on electrochemical performance of solid oxide fuel cells

Journal of Solid State Electrochemistry - In this work, anode-supported solid oxide fuel cells (SOFC) were tested with a yttria-stabilized zirconia (YSZ) (8 mol%...     

A Study of the Electrochemical Characteristics of Single-Chamber Solid Oxide Fuel Cells Based on Platinum and Strontium-Doped Lanthanum Manganite Electrodes and Fed with a Methane–Air Mixture

Kinetics and Catalysis - The properties of single-chamber solid oxide fuel cells (SC SOFCs) composed of an electrolyte based on yttria-stabilized zirconia (YSZ), a platinum anode, and a...     

Surface changes of yttria‐stabilized zirconia in water and Hanks solution characterized using XPS

Adhesion of soft and hard tissues to yttria‐stabilized zirconia (YSZ) has been reported, despite its chemical inertness. To investigate the underlying mechanism of adhesion of hard and soft tissues to YSZ in dental implants, YSZ disks with (100), (110), and (111) crystalline planes were immersed in water for 60 days and in Hanks solution for 7 days, and the changes in the surface chemical states were characterized using X‐ray photoelectron spectroscopy. After immersion in water for 60 days, the concentration of hydroxyl groups on the YSZ surface increased. Therefore, the surface of YSZ was hydrated during immersion in water. In addition, phosphate groups were formed on the surface of YSZ immersed in Hanks solution. We conclude that the formation of phosphate on the YSZ surface in physiological conditions can promote reaction with the surrounding tissues.     

薄膜型中温固体氧化物燃料电池 (SOFC)研制及性能考察

用一种廉价的湿化学方法 ,在Ni_YSZ阳极基膜上制备出致密的YttriaStabilizedZirconia(YSZ)薄膜 .薄膜的厚度约为 10 μm ,致密均匀 ,无裂纹等缺陷 .以Ni_YSZ阳极基膜 ,YSZ薄膜和锶掺杂锰酸镧阴极 (LSM )组装的SOFC单电池 ,在 80 0℃下功率密度达 0 1W /cm2 .研究分析表明 ,YSZ薄膜的IR降 (包括电极 /YSZ薄膜的接触电阻 )较小 ,不是影响电池性能的主要因素 ,大的阳极过电位是影响电池性能的主要因素 .     

高温水溶液pH值原位测量系统与机理

研制了以氧化钇稳定氧化锆(YSZ)陶瓷薄膜电极为pH电极、外置压力平衡式Ag/AgCl电极为参比电极的高温高压水溶液pH值原位测量系统,测量了H₃BO₃\LiOH水溶液在473.15~573.15 K范围内的pH值,并与热力学计算得到的pH值比较。 结果表明,当温度高于548.15 K时,测量系统可以实现pH值的准确测量;而低于此温度时,由于YSZ陶瓷膜内阻过大,测得的pH值与理论计算值存在偏差,且随温度的降低,测量偏差增大。 讨论了该系统的pH值测量机理。     

Experimental investigation on the supercooling and heat conduction of sodium acetate trihydrate/copper foam/YSZ composite phase change material

Journal of Thermal Analysis and Calorimetry - In this study, yttrium-stabilized zirconia (YSZ) was firstly used as a nucleating agent and copper foam as the matrix to simultaneously reduce the...