Iron-doped alumina

The investigation of the stability of P -alumina in ZEBRA cells, which always contain some iron, showed an increase of resistance under certain extreme conditions of temperature (370 °C) and of voltage. This is related to the interaction of the P alumina with iron and it was shown that iron enters / -alumina in the presence of an electric field when current is passing, if the cell is deliberately overheated. However, it was found that only the P -phase but not the P"-phase was modified by the incursion of iron. The resistance of the iron-doped regions was high. It was shown that the addition of NaF inhibits access of the iron to the / " -alumina ceramic. By doping practical cells these difficulties have now been overcome and lifetime experiments show that the stability of / "-alumina electrolytes are excellent in ZEBRA cells. 

The CVD method used in this experiment to grow nanotubes was accomplished using the pyrolysis of methane, catalyzed by iron-doped alumina catalyst (Eq. 1). 

Three of the recently introduced arsenic adsorbents, iron-doped alumina, iron-oxide coated sand, and granular ferric hydroxide, merit a brief discussion here because of their demonstrated effectiveness in removing arsenic. Because ferric hydroxide has a higher capacity for arsenic than does an equivalent surface area of aluminum hydroxide, iron-doped aluminas have been designed for the purpose of improving their arsenic capacity. One such adsorbent is Alcan AAFS-50, a brown-colored promoted alumina that is advertised to have five times the arsenic capacity and less pH sensitivity than conventional activated aluminas (6). Unlike conventional aluminas, AAFS-50 cannot be regenerated, but it reportedly can be landfilled without special treatment. Our recent research (7) showed... 

There is some interest in iron-doped beta alumina for use as an ionic cathode in conjunction with a beta alumina electrolyte. The obvious attraction of this system is that interfacial problems are largely eliminated and the ionic diffusivity in the cathode should approximate to that in the electrolyte. The a g j tages of an all-ceramic battery were recognised some while ago, but the observed power density was too low for practical battery applications, although it was suggested that the device might find application as a capacitor. 

Pol] Poliak, T.M., High Temperature Electrical Conductivity and Defect Chemistry of Iron-Doped Alumina , Thesis, Massachusets Inst. Technology, 81pp. (1976) (Electr. Prop., Experimental, 29)... 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

Thus far, we have only considered the colors responsible for doping a crystal with one type of metal ion. However, crystals such as blue sapphire contain two metal dopants that yield the desirable deep blue color due to charge-transfer effects. If two adjacent Al sites in alumina are replaced with Fe " " and Ti " ", an internal redox reaction may occur, where the iron is oxidized and the titanium is reduced (Eq. 14). 

Transparent anatase Ti02-based multilayered photocatalytic films synthesized via a sol-gel process on porous alumina and glass substrates showed a sponge-like microstructure and a mean crystallite dimension of ca. 8 nm [152]. Doping such films with iron(III) impeded the photocatalytic activity. 

The process of ethane oxidative chlorination imposes heavy demands on the catalysts. The conventional salt supported catalysts are composed of Cu, K, Ca, Mn, Co, Fe, Mg, and other metal chlorides containing various additives these salts are precipitated on alumina, zeolites, silica gel, and other supports. Catalytic systems that represent solid solutions of iron cations in the lattice of the a-A Oa and a-Ct203 phases doped with cations, such as K, Ba, Ce, and Ag are also known [7]. 

P. Tartaj and J. Tartaj, Microstructural evolution of iron-oxide-doped alumina nanoparticles syn-... 

The key property required of the inorganic species is ability to build up (polymerize) around the template molecules into a stable framework. As is already evident in this article, the most commonly used inorganic species are silicate ions, which yield a silica framework. The silica can be doped with a wide variety of other elements (heteroatoms), which are able to occupy positions within the framework. For example, addition of an aluminium source to the synthesis gel provides aluminosilicate ions and ultimately an aluminosilicate mesoporous molecular sieve. Other nonsilica metal oxides can also be used to construct stable mesoporous materials. These include alumina, zirconia, and titania. Metal oxide mesophases, of varying stability, have also been obtained from metals such as antimony (Sb), iron (Fe), zinc (Zn), lead (Pb), tungsten (W), molybdenum (M), niobium (Nb), tantalum (Ta), and manganese (Mn). The thermal stability, after template removal, and structural ordering of these mesostructured metal oxides, is far lower, however, than that of mesoporous silica. Other compositions that are possible include mesostructured metal sulfides (though these are unstable to template removal) and mesoporous metals (e.g., platinum, Pt). 

Sapphires, large, single crystals of alumina doped with iron and titanium impurities... 

Basic copper(ll) carbonate Cobalt(ll) stannate Cobalt(ll)-doped alumina glass Calcium copper(ll) silicate Sulfur radical anions in a sodium aluminosilicate matrix Barium manganate(VII) sulfete Copper(ll) phthalocyanine Basic oopper(ll) sulfete Iron(lll) hexacyanoferrate(ll) Cobalt(ll) silicate Basic copper(ll)... 

Nitrogen-doped CNTs have also been reported recently by Pham-Huu and coworkers as an efficient metal-free catalyst in the partial oxidation of H2S into elemental sulfur [139]. Such reaction is mostly catalyzed by iron-based catalysts supported on different carriers such as silica, alumina, or silicon carbide [140,141]. The optimization process was further conducted... 

A rapid microwave oxidation protocol for the oxidation of alcohol to carbonyl compound has been reported by Varma (2001). Different types of oxidizing reagents have been used with microwave irradiations. Alcohols were converted into corresponding carbonyl compounds in the presence of montmorillonite KIO clay-sup-ported iron (111) nitrate (Clayfen), Oxone-alumina, IBD-alumina, 35% MnO doped silica, CrO,-alumina or CuSO-alumina under microwave irradiation and solvent-free conditions in few minutes (0.25-3.5 min). 

Esp] Espinosa-Medina, M.A., Casales, M., Martinez-Villafane, A., Porcayo-Calderon, J., Martinez, L., Gonzalez-Rodriguez, J.G., Hot Corrosion of Atomized Iron Aluminides Doped Wifli Boron and Reinforced With Alumina , Mater. Sci. Eng. A, A300(l-2), 183-189 (2001) (Experimental, Meehan. Prop., Morphology, 18)... 

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