Oxides binary crystalline

The binary oxides and hydroxides of Ga, In and T1 have been much less extensively studied. The Ga system is somewhat similar to the Al system and a diagram summarizing the transformations in the systems is in Fig. 7.13. In general the a- and y-series have the same structure as their Al counterparts. )3-Ga203 is the most stable crystalline modification (mp 1740°) it has a unique crystal structure with the oxide ions in distorted ccp and Ga " in distorted tetrahedral and octahedral sites. The structure appears to owe its stability to these distortions and, because of the lower coordination of half the Ga ", the density is 10% less than for the a-(corundum-type) form. This preference of Ga "... 

M. (2008) One-minute synthesis of crystalline binary and ternary metal oxide nanoparticles. Chemical Communications, (7), 886-888. 

There are several ways to prepare thin films for use as model catalyst supports.30-31 For the purposes of this review, we will point the reader toward other sources that discuss two of these methods direct oxidation of a parent metal and selective oxidation of one component of a binary alloy. 32 34 The remaining method consists of the deposition and oxidation of a metal on a refractory metal substrate. This method has been used extensively in our group323131 11 and by others33-52-68 and will be the focus of the discussion here. The choice of the metal substrate is important, as lattice mismatch between the film and the substrate will determine the level of crystallinity achieved during film growth. 

Much research has been devoted to the insertion of different kinds of crystalline and non crystalline material into the hollow interior of carbon nanotubes. The encapsulated species include fullerenes, clusters, one-dimensional (ID) metal nanowires, binary metal halides, metal oxides, and organic molecules. 

Fig. 8. (a) Transmission electron micrograph of a Cu/ZnO = 30/70 binary catalyst (40) 60 A copper spheres are placed on crystalline zinc oxide network, (b) Dark field image of the copper crystallites in the area shown in the bright field image (a) obtained using the [111] reflection of copper. [Adapted with permission from J. Catal. 57, 339 (1979). Copyright (1979) Academic Press, New York.]... 

The highest oxidation states for Ir are VI and V, stabilized by ligands such as F. IrFg (a yellow crystalline sohd, /Xeff = 2.9 /xb at 300 K) is formed by the direct fluorination of Ir metal. Molecules of IrFe are octahedral, and the stmcture has been studied in the gas phase by electron diffraction and in the sohd phase by EXAFS. IrFe is hydrolyzed by water, and reactions (1-4) illustrate its general reactivity. Reaction four represents the formation of the first binary, tripositive metal carbonyl complex. ... 

Lead forms binary halides in both oxidation states, although the tetrahalides, PbX4, are generally much less stable than their bivalent analogs, PbX2. Lead(TV) fluoride is the only halide of lead which is stable under ordinary conditions. It is a crystalline solid with a melting point >600 °C and obviously... 

The most commonly used methods for the preparation of ultrathin oxide films are (1) direct oxidation of the parent metal surface, (2) preferential oxidation of one metal of choice from a suitable binary alloy, and (3) simultaneous deposition and oxidation of a metal on a refractory metal substrate. The detailed procedures for (1) and (2) are discussed elsewhere [7,56,57] procedure (3) is discussed here in detail. Preparation of a model thin-film oxide on a refractory metal substrate (such as Mo, Re, or Ta) is usually carried out by vapor-depositing the parent metal in an oxygen environment. These substrate refractory metals are typically cleaned by repeated cycles of Ar sputtering followed by high-temperature annealing and oxygen treatment. The choice of substrate is critical because film stoichiometry and crystallinity depend on lattice mismatch and other interfacial properties. Thin films of several oxides have been prepared in our laboratories and are discussed below. 

The first report was by Komameni and coworkers [179] using a microwave-hydrothermal process to catalyze the synthesis of crystalline oxides such as Ti02, Zr02 and Fc203, and binary oxides such as KNbOs and BaTiOs. The importance of this work was that this technique led to fine powders of these materials. The effect of different parameters, such as concentration of chemical species, time and temperature, on the crystallization kinetics of the above phases has been investigated under microwave-hydrothermal conditions using microwaves of 2.45 GHz frequency. 

Whereas the development of crystalline, open-frameworks based upon silicates, phosphates and related materials has progressed at an ever increasing pace, the synthesis of simple binary oxides with periodic open stmctures has been less sue-... 

---