Surface oxygen content

Figure 9. Effect of burnoff on surface oxygen content natural graphite NG7 [391.

Fe203-Sb204 has been shown to be an excellent catalyst for the allylic oxidation of olefins. The surface oxygen content and the ratio of Fe/Sb are believed to be important for catalysis (Aso et al 1980). The active surface is shown to be an Sb-enriched surface layer, as found in the Sb-Sn oxide systems. 

In an investigation of a-Ala- V Oa solid solutions Pomonis and Vickerman38 showed that the surface V/Al ratio increased linearly with x, but that the surface oxygen content increased strongly beyond x = 0.01, which seems to be connected with easier charge transfer. 

Oxygen and ethylene adsorb on a supported silver catalyst. A Rideal-Eley mechanism is favored for the adsorption. Chloride is a promoter/modifier for the catalyst and reduces the surface oxygen content. Silver on the surface tends to increase ethylene adsorption, which explains why small levels of chloride increase the rate of reaction. 

The surface oxygen content also affects the resistivity of the carbon particles. Thus active carbon oxidation, as in other powdered carbon materials, enhances, whereas heat treatment in an oxygen-free atmosphere diminishes electrical resis-... 

Pendleton and coworkers [46] showed (Fig. 25.5) that the adsorption of dodecanoic acid on different activated carbons linearly decreased when the oxygen content of the carbonaceous adsorbent increased and that the adsorption was not related to the micropore volume of the adsorbent. They concluded that the surface chemistry more accurately predicted the adsorption of dodecanoic acid in aqueous phase compared with the surface area or micropore volume. In addition, carbon surface chemistry also had a significant influence on dodecanoic acid adsorption kinetics. Thus, the adsorption rate was reduced by the high surface oxygen content of the carbon adsorbent, whereas its pore volume made a smaller contribution [47],... 

For low percent styrene block copolymers surface energies approach their highest levels and surface oxygen content the lowest levels upon exposure to ozone. This mechanism appears to be different than the previous mechanisms and occurs only when styrene blocks are present in low concentrations compared to butadiene and also appear to reside preferentially at the surface. Infrared spectroscopy and gravimetric studies are currently being considered as further work in an attempt to answer some questions posed by this work. 

An essential feature of these films is that they are prone to oxidation. The surface oxygen content, with a few exceptions, varies between 10 and 20 at%. This surface oxide contamination could be removed completely (to a trace level of 1-2 at % of O) by applying a short (10 min) IkeV Ar+ ion etch. As calculated by the TRIM 95 program [21] the penetration of Ar+ ions into Ni and Ni-C (Ni/C=l 1) alloy is ranging from 1.2 to 2 nm only. On this basis we consider that Ar+ bombardment would not alter significantly neither the bulk composition of the layers, nor the chemical states of the constituent elements. 

XPS is primarily a surface technique, as the escape depth of the photoelectrons ranges from 2 to 5 nm, and it would therefore primarily yield information on the composition of the most external surface of the carbon nanofibers. For this reason should it be possible to obtain the surface oxygen content from XPS [28]. In this regard, it was suggested that 80-90 % peak area... 

Figure 14. Effect of surface oxygen content on interfadal shear strength measured on single fiber AU and HMU indcate no commercial surface treatment AS and HMS indicate commercial surface treatment. Temperatures indicate heat treatment for removal of oxygen. (Reprinted with permission from Ref. 94. Copyright 1982 Gordon and Breach Sdence Publications.)...

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