Metal-oxide interactions

Vanadium oxide dispersed on supporting oxides (Si02 Al Oo, Ti02, etc.) are frequently employed as catalysts in reactions like partial oxidation and ammoxidation of hydrocarbons, and NO reduction. The modifications induced on the reactive properties of transition metal oxides like V20 when they are supported on an oxide carrier has been the subject matter of recent study. There is much evidence showing that the properties of a thin layer of a transition metal oxide interacting with the support are strongly modified as compared to the properties of the bulk oxide (1-3). In the recent past, increasing attention has been focussed... 

The basic reaction underlying the combustion of many gasless delay formulations is the Goldschmidt or thermite reaction where a metal powder and a metallic oxide interact in an oxidation-reduction reaction manner with the evolution of a large amount of heat but very little or no gas. Consequently, these formulations are used where no vent or very little vent is provided in the ammunition. Gasless delay formulations tend to burn faster under higher consolidation as the points of contact of fuel and oxidizer increase. This is because the reaction in this case is a solid state reaction by diffusion. 

Surface Science Studies of Strong Metal-Oxide Interactions on Model Catalysts... 

The other consequence of the weak metal-oxide interactions on the nondefective surfaces is that small metal clusters once deposited on the substrate tend to keep the same structure as they have in the gas phase. Of course, the actual structure of the deposited cluster is a delicate balance between the strength of the metal-metal bond within the cluster and the metal-oxide interface bond. Also in this case, however, it is likely that the small clusters will diffuse on the surface until they become stabilized at some specific defect site. 

The present investigation was conducted to identify and determine the degree of Rh-base metal oxide interaction, using unsupported rhodium oxides and bulk aluminum and rare earth metal rhodates. Catalytic activities were determined using monolithic catalysts containing various bulk rhodium species exposed to a simulated stoichiometric auto exhaust composition. The activities were correlated with information obtained from CO chemisorption measurements, temperature-programmed reduction,... 

Electron transfer from metal oxide surfaces to CO can be quite facile, occurring at room temperature. This process can be important as an initial CO activation step in metal oxide catalyzed reduction schemes. We have attempted to clarify what types of metal oxides interact (MO CO MO. . . CO -) with CO in this way, and what surface features these active metal oxides possess. Only MgO, CaO, SrO, BaO, and Th02 were electron transfer active. These oxides have in common the possession of both Lewis basic sites and one electron reducing site. It appears that CO is first adsorbed on Lewis base sites followed by slow migration to electron transfer reducing sites. The studies leading to this conclusion are discussed. 

The metal-oxide interaction also depends upon the rate of the metal deposition. Experimental results show that an increase in the deposition rate affects the structure and composition of the interfacial layer in much the same way as an increase in substrate temperature [6]. The effects of the rate of metal deposition, the substrate temperature, and the layer thickness on the electrical and physical properties of solar cells may be understood in terms of the physical and chemical interactions in Ti-SiO -Si cells [5, 6, 8]. 

Snyder, R.W. Diffuse reflectance FT-IR analysis of rosin flux-metal oxide interactions. Appl. Spectrosc. 1987, 14 (3), 460-463. 

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