Metal-containing Amorphous Hydrocarbon

An essential problem to be solved before introducing coatings to practice is a good and reliable adhesion. The very promising properties of a-C H films for a long time could not be utilized because of their high compressive stress. For thickness of more than 1-2 pm the adhesion, especially on steel, was insufficient. This problem is still more pronounced for ta-C films. Today there are possibilities to improve the adhesion markedly, for example by interlayer systems (for more details see Section 3.5). 

Concerning the mechanism of MeC H sputter deposition two components must be considered [35, 37]. 

Today MeC H coatings are widely used in industrial practice, for example for machine parts improved with wear resistant surfaces exhibiting low friction. On the other hand the wear resistance of MeC H has still not reached the level of a-C H. Therefore a further improvement of the MeC H quality as well as a higher productivity and reliability of a-C H and ta-C coatings will be necessary. 

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Cobalt(III) fluoride is a light brown powder that appears to be amorphous upon examination. In moist air it undergoes hydrolysis with formation of hydrogen fluoride and turns dark brown. It reacts violently with water and with hydrocarbons. When stored in an airtight metal container it is quite stable and may be kept for extended periods of time. Its density is 3.89 g./ml. at 18°. 

A high degree of hydrophobic character is an almost unique characteristic of silicon-rich or pure-silica-type microporous crystals. In contrast to the surface of crystalline or amorphous oxides decorated with coordinatively unsaturated atoms (in activated form), the silicon-rich zeolites offer a well-defined, coordinatively saturated sur ce. Such surfrces, based on the strong covalent character of the silicon-oxygen bond and the absence of hydrophilic centers, display a strong hydrophobic character unmatched by the coordinativeiy unsaturated, imperfect surfaces. Also, hydrophobic zeolite crystals have been reported to suppress the water affinity of transition metal cations contained in the zeolite pores. This property permits the adsorption of reactants such as carbon monoxide or hydrocarbons in the presence of water. 

Ni based amorphous alloy containing Pd in low concentration seems to be a good candidate for hydrocarbon oxidation as both metals are active in oxidation reactions [8]. In the present work from the possible Ni-based metal alloys the Ni5oNb50 composition has been selected as we have good deal of experience in its preparation. We replaced part of Nb by Pd and used Pd2Ni5oNb4g amorphous alloy ribbons as starting material for the oxidation of xylene. The latter reaction has been selected as a model reaction for the oxidation of unbumt hydrocarbons in automobile exlraust gases. 

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