Various ceramic oxides

An idea to use polybasic hydroxy carboxylic acids in syntheses of oxides goes back to Pechini [3], Evaporating solutions of metal salts in citric acid at presence of ethylene glycol he obtained a polymeric resin as a precursor of target oxides. Then this process was extensively used to manufacture various ceramic oxide powders in several publications [4-8],... 

Recently, Takenaka et studied a series of base metal catalysts supported on various ceramic oxides for catalytic cracking of kerosene fuel. Yields of H2 and methane from a model kerosene fuel (52 wt% n-Ci2, 27 wt% diethylbenzene and 21 wt% t-butylcyclohexane) over various base metals at 600°C are shown in Figure 33. Ni/Ti02 showed the highest catalytic activity for the cracking reaction of kerosene fuel, and also maintained a better performance for the kerosene feed that contained benzothiophene. However, the catalytic performance of the... 

Various ceramic oxides are used for making ceramic fibers, among them pure alumina fibers and alumina-silica fibers are the most common. The former were commercialized by ICl Ltd. under the trade name SaffW extensively used in high temperature insulation to replace asbestos and glass fiber felts that pose occupational safety issues, while alumina-silica fibers were commercialized by 3M under the trade name Nextel . Various processing routes can be used to manufacture ceramic oxide fibers, the most common being ... 

Calcination is performed in crucibles made of platinum or related metals. Tantalum or niobium oxide can be successfully used in the manufacturing of such crucibles. Frolov et al. [505, 506] developed a method for coating various ceramic materials with tantalum or niobium oxide using an optical furnace. 

The two most common substrates for thin film electrodes are various types of glass—soda-lime, Pyrex, and various forms of quartz or fused silica—and silicon wafers that have been treated to produce an insulating surface layer (typically a thermally grown oxide or nitride). Other possible substrates include mica, which can be readily cleaved to produce an ordered surface, and various ceramic materials. All of these materials can be produced in very flat, smooth... 

The use of various methods (coprecipitation, impregnation and deposition-precipitation) confirmed the superiority of the transition metal oxides as supports,69 these being more easily reducible than the ceramic oxides that gave low activities (Table 6.6). With mixed Fe2C>3-MgO supports activity increased with iron content, not withstanding a growth in gold particles size.69... 

For most oxides, as the pH is increased, the adsorption of potential determining ions, H" and OH, changes in correspondence with the concentration of these species in solution. For each surface, therefore, a point is reached at which the concentration of positive ions and negative ions just balance, the point of zero charge. The pH where the zeta potential, is 0, is called the isoelectric point. The isoelectric point for various ceramic materials is given in Table 9.11. 

Figure 4.23 Relative comparison of acidic and basic resistances of various metal oxides and ceramics [Lay, 1979]...

Thermal shock resistance. Temperature swing as part of the normal cycles of operation or regeneration of the membranes or membrane reactors can lead to deleterious thermal shock. The materials for the various components in a membrane reactor should be carefully selected to impart good thermal sh k resistance. This is particularly important for high temperature reactions. Also listed in Table 9.5 is a summary of various membrane materials along with qualitative description of their resistance to thermal shock. Again, the available data apply to dense materials. While various metal oxides have been made into commercial inorganic membranes, they tend to be affected by thermal shock much more than other ceramic materials. 

In addition to emitting various types of radiation, nuclear waste materials are commonly mixtures of different compounds and even different phases. Energy transfer between phases and interfacial chemistry will affect the yields and types of products formed in these systems. Interfacial effects in radiation chemistry have long been observed, but the detailed mechanisms involved are not understood [3-5], Recent studies of water adsorbed on ceramic oxides clearly show that energy can migrate from the solid oxide phase to the water phase and lead to excess production of H2 [6, 7], This process complicates dosimetry because energy... 

As heated alkalies readily attack stainless steel, it was found necessary to use liners or crucibles in the above bombs. Borosilicate glass was found satisfactory up to about 450 °C. for short periods of time, but it could not be used above this temperature. Various ceramic materials were tried for possible use as containers for the sodium peroxide-superoxide mixtures. Sintered aluminum oxide and magnesium oxide were satisfactory up to 450 °C., but above this temperature the sodium oxides penetrated the sintered material and corroded the stainless steel bomb. Commercial ceramic coatings containing (as the principal components) alumina, magnesia, and titania were also tried without success at a temperature above 450 C. 

Typically, electroplating metals and metal alloys is less sophisticated than the corresponding metal oxide or chalcogenide electrodeposition. Further, dense and highly stable deposits are usually obtained. The two-step synthesis approach is more versatile, in a sense that after identifying a synthesis route to a nanostructured metal, various ceramics can be produced by thermal oxidation under an appropriate atmosphere. In fact more porous and sophisticated structures, such as hollow nano-spheres, nanotubes, and nano-peapods, can be synthesized based on the nanoscale Kirkendall effect (NKE) occurring during thermal oxidation [2-5]. 

Chapter 200, by Peter M. Allenspach and M. Brian Maple, reviews some aspects of the low-temperature heat capacity of the ceramic oxide superconductors. These measurements yield valuable information about the electronic, lattice, magnetic, crystalline electric field and hyperfine nature of the various rare-earth cuprate materials, and in that respect compliment other physical property studies, such as neutron diffraction, inelastic neutron scattering, and various spectroscopic measurements. The authors review the heat-capacity properties of the stoichiometric RBaCu307 compoimds and oxygen-deficient materials, and show that there are significant differences. The heat capacities of other lanthanide cuprates, such as RBa2Cu40g and R2B4CU7O14+X, are also discussed. 

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