Carbon directed metal oxidation

With the analysis embodied in Fig. 12, the formation of carbon fiber reinforced Si3N4 matrix materials by directed metal oxidation of molten silicon can also be described. To avoid fiber degradation during processing, the fiber should, ideally, be thermodynamically stable with respect to... 

The other more electronegative elements are non-metals and form oxides which are entirely covalent and usually acidic. For example, sulphur yields the oxides SO2 and SO3, dissolving in bases to form the ions SO3 and SO4" respectively. A few non-metallic oxides are often described as neutral (for example carbon monoxide and dinitrogen oxide) because no directly related acid anion is known to exist. 

Perchlorates. Historically, perchlorates have been produced by a three-step process (/) electrochemical production of sodium chlorate (2) electrochemical oxidation of sodium chlorate to sodium perchlorate and (4) metathesis of sodium perchlorate to other metal perchlorates. The advent of commercially produced pure perchloric acid directly from hypochlorous acid means that several metal perchlorates can be prepared by the reaction of perchloric acid and a corresponding metal oxide, hydroxide, or carbonate. 

It is known that some spinel-structured 3d-metal oxides are good catalysts for many processes involving electron transfer [12]. However, their low conductivity does not allow for the direct use in the electrode of the battery, and grafting them onto the carbon matrix is also very difficult technical problem. It was found recently that this problem could be solved indirectly, creating the spinel catalytic centers on the surface of carbon by means of adsorption of some 3d-metal complexes on the graphite surface followed by subsequent pyrolysis at certain temperatures [13,14],... 

Calcium carbide can be produced by the direct reaction of carbon with the metal or metal oxide ... 

The SEA approach can be applied to a novel system in three steps (1) measure the PZC of the oxide (or carbon) and choose a metal cation for low-PZC materials and an anion for high-PZC materials, (2) perform an uptake-pH survey to determine the pH of the strongest interaction in the appropriate pH regime (high pH for low PZC and vice versa), and (3) tune the calcination/reduction steps to maintain high dispersion. Highly dispersed Pt materials have been prepared in this way over silica, alumina, and carbon. Other oxides can be employed similarly. For bimetallics, the idea is to first adsorb a well-dispersed metal that forms an oxide intermediate with a PZC very different to the support. In this way the second metal can be directed onto the first metal oxide by SEA. Reduction may then result in relatively homogeneous bimetallic particles. 

In general, there are two possibilities to prepare nanocarbon-supported metal(oxide) catalysts. The in situ approach grows the catalyst nanoparticles directly on the carbon surface. The ex situ strategy utilizes pre-formed catalyst particles, which are deposited on the latter by adsorption [94]. Besides such solution-based methods, there is also the possibility of gas phase metal (oxide) loading, e.g., by sputtering [95], which is used for preparation of highly loaded systems required for electrochemical applications not considered here. 

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