Oxide amorphous

Calcined alumina, a-Al202, and naturally occurring comndum are practically insoluble in acids and bases, but partially calcined and low temperature amorphous oxide, such as that which forms on nacent commercial aluminum surfaces, is soluble... 

Balabanov et al. [499] found an endothermic effect in the thermographic pattern of the decomposition of niobium hydroxide at 435°C that corresponds to complete removal of water. At the above temperature, amorphous niobium hydroxide also converts into amorphous niobium oxide. Ciystallization of the amorphous oxide occurs at a higher temperature with the release of energy [28]. Researchers [499] reported on another exothermal effect at 549°C that was attributed to the crystallization temperature of amorphous niobium oxide. Decomposition of tantalum hydroxide and its conversion into crystalline tantalum oxide occurs at about 710°C [502] or at 670-700°C according to another source [132]. 

The hydroamination of alkenes has been performed in the presence of heterogeneous acidic catalysts such as zeolites, amorphous aluminosilicates, phosphates, mesoporous oxides, pillared interlayered clays (PILCs), amorphous oxides, acid-treated sheet silicates or NafioN-H resins. They can be used either under batch conditions or in continuous operation at high temperature (above 200°C) under high pressure (above 100 bar). 

Idota Y., Kubota T., Matsufuji A., Maekawa Y., Miyasaka T. Tin-Based Amorphous Oxide A High-Capacity Lithium-Ion-Storage Material. Science 1997 276 1395-97. 

General Aspects and Heat Treatment Effects. After him formation, for most of the hlms aimed at electronic applications (other than amorphous oxides, such as Si02), the hlms are subjected to a heat treatment process for removal of residual organic species (entrapped solvent as well as the organic constituents associated with the precursor species), densihcation (elimination of residual porosity and structural free volume in the him), and crystallization. 

Lee, D-H. Chang, Y-J. Herman, G. S. Chang, C-H. 2007. A general route to printable high-mobility transparent amorphous oxide semiconductors. Adv. Mater. 19 843-847. 

Nomura, K. Ohta, H. Takagi, A. Kamiya, T. Hirano, M. Hosono, H. 2004. Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors. Nature 432 488-492. 

Hosono, H. 2006. Ionic amorphous oxide semiconductors Material design, carrier transport, and device application. J. Non-Cryst. Solids 352 851-858. 

Delhi soils by studying its speciation in the soil profile and to assess if there was any spatial variability. Soils representing the Aravali Ridge and the alluvial floodplains of river Yamuna were collected as a single, undisturbed core up to a depth of lm and the profile differentiated into four layers- 0-17 cm, 17-37 cm, 37-57 cm, and 57-86 cm. Pseudo total Aluminum and Iron in the soils were speciated into the operationally defined species (weakly exchangeable, organic matter complexes, amorphous oxides and hydroxides, and crystalline or free oxides) by widely recommended selective extraction procedures. Both A1 and Fe in these soils are bound predominantly as Fe oxides and silicates and have only very low percentages in the easily mobilizable pools. 

The acid component of a hydrocracking catalyst can be an amorphous oxide, e.g., a silica-alumina ora zeolite, eg., USY. This component usually serves as a support for the metal compound responsible for the hydrogenation function. The metal compound can be a noble metal, e.g., Pt or Pd, or a mixture of sulfides, e.g., of Ni/Mo, NiAV, or Co/Mo. The relative amounts of the respective compounds have to be thoroughly balanced to achieve an optimum performance. 

Figure 24. Schematic illustrations of the conditions of surface lattice structure (a) amorphous-like surface with no identity of orientation, (b) surface with kinks, steps and terraces characteristic of certain crystalline orientation and (c) surface with no identity of the lattice structure of the crystal due to the coverage of an amorphous oxide film. 

Recently, however, considerable doubt has been cast on these conclusions. In the case of the putative Mg/Al/Sn - CO3, Mg/Al/Zr - CO3 and Co/Al/Sn - CO3 materials it has been unambiguously shown by X-ray absorption spectroscopy (XAS) and Mossbauer spectroscopy that the tetravalent cations are segregated from the LDH structure and form amorphous oxide-hke particles [69]. It was further demonstrated that the increased values of Uo previously attributed to the introduction of the large cations... 

Little is known concerning the chemistry of nickel in the atmosphere. The probable species present in the atmosphere include soil minerals, nickel oxide, and nickel sulfate (Schmidt and Andren 1980). In aerobic waters at environmental pHs, the predominant form of nickel is the hexahydrate Ni(H20)g ion (Richter and Theis 1980). Complexes with naturally occurring anions, such as OH, SO/, and Cf, are formed to a small degree. Complexes with hydroxyl radicals are more stable than those with sulfate, which in turn are more stable than those with chloride. Ni(OH)2° becomes the dominant species above pH 9.5. In anaerobic systems, nickel sulfide forms if sulfur is present, and this limits the solubility of nickel. In soil, the most important sinks for nickel, other than soil minerals, are amorphous oxides of iron and manganese. The mobility of nickel in soil is site specific pH is the primary factor affecting leachability. Mobility increases at low pH. At one well-studied site, the sulfate concentration and the... 

The fdm thickness was 35 nm. Various analytical techniques were used to confirm that the deposit was amorphous Y(OH)C03. Annealing at 600°C was necessary to convert the film to crystalline Y2O3 (amorphous oxide was formed between 300 and 400°C), with a film thickness of 25 nm and crystal size of ca. 20 nm. 

An alternative method for the preparation of crystalline vanadium pentoxide consists in heating a mixture of the amorphous oxide and calcium fluoride to red heat in an open crucible over which is suspended another crucible, inverted, to act as a receiver. The inside of the latter becomes coated with shining, needle-shaped, yellow crystals, which also become reddish-brown on being heated.4... 

Evaporation of the hydrochloric acid solution of the red, amorphous oxide may also give rise to crystals.5... 

This is prepared by the interaction of the foregoing oxide and an excess of bromine. It separates from alcohol as silvery prisms darkening and decomposing at 253° C. From its alkaline solution dilute acetic acid precipitates the amorphous oxide, which yields 5-chloro-3-bromo-o-cresol on treatment with chlorine water. 

Br0nsted acid sites depends on the structure of the amine. Chemisorption data for amorphous oxides (54) show that 2,6-dimethylpyridine (which contains methyl groups that hinder coordination of the nitrogen atom with Lewis acids) is a more selective reagent for the determination of Br0nsted acidity than an unhindered amine such as pyridine. Jacobs and Heylen (44) arrived at a similar conclusion on the basis of an infrared study of amines chemisorbed on Y zeolite. They also found that the poisoning effectiveness of 2,6-dimethylpyridine is much greater than that of pyridine for the catalytic titration of Y zeolite. 

---