Cerium oxide stabilizers

Kubsch, J.E., J.S. Rieck and N.D. Spencer, 1991, Cerium oxide stabilization physical property and three-way activity considerations, in Catalysis and Automotive Pollution Control II, ed. A. Crucg (Elsevier, Amsterdam) pp. 125-138. 

In addition to platinum and related metals, the principal active component ia the multiflmctioaal systems is cerium oxide. Each catalytic coaverter coataias 50—100 g of finely divided ceria dispersed within the washcoat. Elucidatioa of the detailed behavior of cerium is difficult and compHcated by the presence of other additives, eg, lanthanum oxide, that perform related functions. Ceria acts as a stabilizer for the high surface area alumina, as a promoter of the water gas shift reaction, as an oxygen storage component, and as an enhancer of the NO reduction capability of rhodium. 

Fillers can also be used to promote or enhance the thermal stability of the silicone adhesive. Normal silicone systems can withstand exposure to temperatures of 200 C for long hours without degradation. However, in some applications the silicone must withstand exposure to temperatures of 280 C. This can be achieved by adding thermal stabilizers to the adhesive formulations. These are mainly composed of metal oxides such as iron oxide and cerium oxide, copper organic complexes, or carbon black. The mechanisms by which the thermal stabilization occurs are discussed in terms of radical chemistry. 

Fu Q, Deng W, Saltsburg H, Flytzani-Stephanopoulos M (2005) Activity and stability of low-content gold-cerium oxide catalysts for the water-gas shift reaction. Appl Catal B 56 57-68... 

Ceresin, in dental waxes, 6 296 Ceresin wax, 26 214 Ceria, 5 592, 675 74 630 Ceria-stabilized alloy, 70 44. See also Cerium oxide... 

Janimak, J. J., and Marteleur, M. (2004), On the stability of cerium oxide glass for terminal radiation sterilization, Rad. Phys. Chem. 71,195-198. 

The promotion ability of cerium is attributed to its capability to form crystalline oxides with lattice defects, which may act as active sites [25]. In addition, the presence of cerium oxide in the catalyst improves its thermal stability and mechanical resistance [26]. Cerium is the most frequent additive used for preparation of the automobile converter catalyst that transforms carbon monoxide, hydrocarbons and nitrogen oxides [27,28]. 

Besides organic polymers, inorganic polymers also are susceptible to thermo-oxidative degradation. Nielsen describes the stabilization of silicone fluids with redox systems of iron and cerium by a free radical mechanism. When stabilized, these fluids show oxidative stability up to 700°F. 

Cerium sulfide pigments are produced from hydrated cerium oxide or oxalate and calcined in an oxygen-free, sulfide environment. They are silica-encapsulated to minimize water-reactivity and to improve heat stability and chemical resistance properties. Because of their low relative value-in-use, they are used primarily in engineering plastics and in particular the polyamides where high-performance organic colorant alternatives and other inorganic pigment alternatives are few. 

The results of porous structure determination of hydrothermally treated samples indicated that there is no visible influence of the presence of cerium oxide on thermal stability. However, in the case of sample calcined at 850 C the tenfold decrease in specific surface area was stated while in the case of sample calcined at 650 "C only fivefold. This observation supports our assumption that the highest temperature of the initial calcination has to be not... 

In comparison to TEOS hydrothermal stabilization efficiency of alumina by cerium oxide is low. 

With the conductivity of an aqueous electrolyte (e.g., IN KCl) serving as a reference, comparable conductivities can be achieved in solid electrolytes under certain conditions. Some of the best solid ionic conductors, commonly referred to as superionic conductors , have resistivities comparable to those of aqueous electrolytes at room temperature (e.g., RbAg4l5 and single crystal MgO-stabilized 6"-alumina). However, they are either in the form of single crystals, which is impractical for most applications, or composed of very expensive and relatively unstable materials. Resistivities comparable to those of aqueous electrolytes can be achieved in solid electrolytes at higher temperatures in both superionic conductors like 6"-alumina (i.e., 300°C) and normal ionic conductors such as stabilized zirconia (800-1000°C), stabilized cerium oxide (>800 C), and stabilized bismuth oxide (>600°C). Sodium ion conducting glasses are much less conductive than polycrystalline 8 -alumina. 

Other oxygen ion conductors that have potential use as solid electrolytes in electrochemical devices are stabilized bismuth and cerium oxides and oxide compounds with the perovskite and pyrochlore crystal structures. The ionic conductivity and related properties of these compounds in comparison with those of the standard yttria-stabilized zirconia (YSZ) electrolyte are briefly described in this section. Many of the powder preparation and ceramic fabrication techniques described above for zirconia-based electrolytes can be adapted to these alternative conductors and are not discussed further. 

Yttria-doped( 20 mol% Y2O3) cerium oxide also has a higher 0 ion conductivity than yttria-stabilized zirconia ( factors of 11-18 at 600°C), which would make it an attractive choice for an electrolyte at lower temperatures (< 800 C) However, doped cerium oxides tend to undergo reduction, with formation of trivalent cerium ions and oxygen ion vacancies, V 6 leading to the onset of electronic conductivity according to ... 

CeOa + 20 mole GdzOg gadolina-stabilized cerium oxide ... 

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