Materials Containing Zirconia

Properties 12 mol % CeO2, specific surface area Tfl average particle size 400 nm [2393], 

Properties ZrO + HfO2 87 mol%, CeOi 13 mol%, specific density 6200 kg/m particle size 400 nm, BET specific surface area 21.4 mVg [444], 

Type Composition Electrolyte T Method Instrument pHo Reference 

Powder used for membrane manufacturing/powder scraped from membrane. 

Zr-Y mixed oxides are often referred to as zirconia in scientific publications. Their PZCs are reviewed in [284], 

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Supports effects do not drastically modify Pd this is shown by XPS and by IR spectroscopy of adsorbed CO Nevertheless, the catalytic performances of the materials have been significantly improved with the supports containing zirconia. For instance, the activity of Pd/Al203-Ba0-Zr02 nearly reaches the activity of the Pt-Rh/Al203 reference. 

FICs are useful as electrochemical sensors, electrolytes and electrodes in batteries and in solid state displays (Farrington Briant, 1979 Ingram Vincent, 1984). If a FIC material containing mobile M ions separates two compositions with different activities of M, a potential is set up across the FIC that can be related to the difference in the chemical activities of M. By fixing the activity on one side, the unknown activity on the other can be determined. This principle forms the basis of a number of ion-selective electrodes LaFj doped with 5% SrF2 is used for monitoring fluoride ion concentration in drinking water. Similarly, calcia-stabilized-zirconia is used in cells of the type... 

T24.1 One of the most popular lambda sensors contains zirconia (ZrO ) as a solid electrolyte. This material has a high conductivity for 0 ions at elevated temperatures. The cell responds to the changes in O2 partial pressure in exhaust gas. The reduction potential for 02(g) + 4e" — 20 (s) is proportional to p(02, reference)/p(02, exhaust gas), with partial pressure of O2 in the air as the reference. (See Section 24.49(b) Solid anionic electrolytes and refer to Fig. 24.9). 

Chemical composition silica-based and silica-alumina-based materials, chrome, magnesia, chrome-magnesia, spinel, SiC, materials containing carbon (more than 1% carbon or graphite), and special materials (containing other oxides or materials such as zircon, zirconia, Si3N4, etc.)... 

Monolithic zirconia networks can also be formed using a similar procedure giving porous 2xQ>2 structures [9]. As the titania and zirconia precursors are miscible, binary inorganic networks of various Ti Zr ratios could be produced [9]. The crystallinity and photocatalytic properties of the mixed material were studied X-ray amorphous materials were produced for Ti Zr ratios of 2 8 to 7 3, and the binary material containing 10% zirconia (the presence of which inhibited crystal transformation to the rutile phase) showed the highest photocatalytic activity for the photodecomposition of sahcylic acid and 2-chlorophenol [9]. 

In order to improve the performance (physicochemical characteristics in general as well as reactivity for catalysis or mechanical properties for ceramics) of prepared materials containing zirconium oxide, the most important characteristics requested are high surface area and phase stability of zirconia nanoparticles. 

Compared to the reference alloy, the Zr-containing material revealed up to breakaway no broccoli effect and only minor macroscopically visible spallation at the specimen corners and edges (Fig. 7.3), in agreement with the mass change data in Fig. 7.1. The suppression of the broccoli effect by Zr has previously been related to tying up the carbon impurity into more stable carbide [12]. It should be noted that no Cr carbide formation was detected in the alloy -l-Zr . The microstructures of the scales after 1000 h oxidation are shown in Fig. 7.8. Compared to alloy MRef the alumina scale on alloy -FZr is thicker and contains zirconia inclusions and porosity in the outer part. Studies of the scale grain structure were performed using electron back-scattered diffraction (EBSD). The studies revealed (Fig. 7.9) that the alumina... 

Mesoporous zirconia (zirconium oxide) materials containing mainly mesopores have been synthesized via sol-gel reactions from zirconinm propoxide nsing urea as a template. The solid was dried, extracted with water to remove urea, calcined at different temperatures and impregnated with trifluoromethanesulfonic acid. The samples thus obtained were extracted with a tnixmre of dichloromethane and diethyl ether using a Soxhlet apparatus in order to remove the loosely adsorbed acid. The solids were characterized by FT-IR, XRD, DTA-TGA, and N2 adsorption-desorption measnrements. The mean pore diameter of the support was higher than 3.7 mn, which increased with the increment of the thermal treatment temperature. At the same time, the specific surface area and the amount of triflic acid attached on the support decreased. The potentiometric titration with n-butylamine indicated that the catalysts present very strong acid sites. The catalytic activity of the prepared catalysts in the esterification of 4-hydroxybenzoic acid w ith propyl alcohol was evaluated. 

Conceptually elegant, the SOFC nonetheless contains inherently expensive materials, such as an electrolyte made from zirconium dioxide stabilized with yttrium oxide, a strontium-doped lanthanum man-gaiiite cathode, and a nickel-doped stabilized zirconia anode. Moreover, no low-cost fabrication methods have yet been devised. 

The stability of ceramic materials at high temperatures has made them useful as furnace liners and has led to interest in ceramic automobile engines, which could endure overheating. Currently, a typical automobile contains about 35 kg of ceramic materials such as spark plugs, pressure and vibration sensors, brake linings, catalytic converters, and thermal and electrical insulation. Some fuel cells make use of a porous solid electrolyte such as zirconia, Zr02, that contains a small amount of calcium oxide. It is an electronic insulator, and so electrons do not flow through it, but oxide ions do. 

The perovskite oxides used for SOFC cathodes can react with other fuel cell components especially with yttria-zirconia electrolyte and chromium-containing interconnect materials at high temperatures. However, the relative reactivity of the cathodes at a particular temperature and the formation of different phases in the fuel cell atmosphere... 

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