Zirconium oxide stabilized

Solid oxide fuel cells use zirconium oxide stabilized with yttrium as an electrolyte and have an OT of 850 to 1000°C. 

Zirconium oxide, stabilized with 3-8% YjO, also has been used in k-probes for determination of the partial pressure of oxygen in car exhaust fumes that makes it possible to optimize the air-fuel mixture to the engine. A similar solid electrolyte is used as a probe for determining oxygen in molten steel. 

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. 

While several types of oxygen sensors have been investigated for automotive use, the most common type in commercial use consists of a galvanic cell with a fully or partially stabilized zirconium oxide electrolyte. 

Stabilized zirconia refers to a solid solution of zirconium oxide with one or more of a number of stabilizing oxides (CaO, MgO, 20, or others) to form a cubic fluorite structure. This... 

The stability of the metallocene complexes is strongly dependent on the nature of the cyclopropene substituents, and the reaction conditions. Thus, when equimolar amounts of 3,3-dimethylcyclopropene and Cp2Ti(PMe3)2 react at 0 °C, a 2 1 mixture of alkylidene and cyclopropene complexes is formed. However, when excess of cyclopropene is used, a dicyclopropyl titanacycle is exclusively formed by oxidative coupling reaction of the intermediate cyclopropene complex (equation 215)77. The analogous zirconium oxidative-coupling product is obtained upon reaction of 3,3-dimethylcyclopropene with Cp2(PMe3)Zr( j2-CH2=CHEt) (Section IV.B.2). 

In all of the discussion of this chapter we have used an aqueous solution as the electrolyte, and electrodes suitable to those aqueous solutions. However, cells are not limited to aqueous solutions. Indeed, other solvents have been used for which liquid ammonia would be an example. Molten salts, such as mixtures of lithium chloride and potassium chloride, have been used for the study of cells at high temperatures. Some studies have been made at higher temperatures, in which solid electrolytes were used. Electrodes compatible with such solvents have also been devised. For example, a zirconium-zirconium oxide electrode stabilized with calcium oxide was used to measure the oxygen potential in nonstoichiometric metal oxides. However, no matter what the electrolytes or the electrodes are, the principles discussed in this chapter such as reversibility and proper measurement must be followed. 

Yttrium Oxide (Y203)-Stabilized Zirconium Oxide (Zr02)... 

Figure 8. SEM surface images of partly crystallized sections of an activated Fe Zr alloy used for ammonia synthesis [23, 24J The main image reveals the formation of a stepped iron metal structure with a porous zirconium oxide spacer structure An almost ideal transport system for gases into the interior of the catalyst is created with a large metal-oxide interface which provides high thermal and chemical stability of this structure The edge contrast in the 200 keV backscatlered raw data image arises from the large difference in emissivity between metal and oxide It is evident that only fusion and segregation-crystallization can create such an interface structure.

This technique is used industrially to produce powders for the fabrication of ceramics [29]. Mainly single-metal oxides arc made in this way, but it is claimed that MnFc204. NiFciOa, NiAl204, dopant-stabilized zirconium oxide and titanates can be obtained. Powders of surface area up to 20 m2g l can be produced. The powder is usually in the form of aggregates of 0.2-... 

Both aluminum oxide and zirconium oxide are catalytically interesting materials. Pure zirconium oxide is a weak acid catalyst and to increase its acid strength and thermal stability it is usually modified with anions such as phosphates. In the context of mesoporous zirconia prepared from zirconium sulfate using the S+X I+ synthesis route it was found that by ion exchanging sulfate counter-anions in the product with phosphates, thermally stable microporous zirconium oxo-phosphates could be obtained [30-32]. Thermally stable mesoporous zirconium phosphate, zirconium oxo-phosphate and sulfate were synthesized in a similar way [33, 34], The often-encountered thermal instability of transition metal oxide mesoporous materials was circumvented in these studies by delayed crystallization caused by the presence of phosphate or sulfate anions. 

Unsatisfactory physicochemical stability of the sorbent. Titanium hydroxide is slightly soluble in seawater (0.1 mg/1 [165]) and also shows some degradation upon aging. Mixed titanium and zirconium oxide-type sorbents, known as thermoxides with much better stability [178, 179] were developed. 

Stabilized zirconium oxide o- 700-1000 Base metal oxides Impure hydrogen Air 10.000 hours life demonstrated in tingle cells. Multikilowatt systems in design. 

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