Aluminum deposition metal substrates

Starting with a ceramic and depositing an aluminum oxide coating. The aluminum oxide makes the ceramic, which is fairly smooth, have a number of bumps. On those bumps a noble metal catalyst, such as platinum, palladium, or rubidium, is deposited. The active site, wherever the noble metal is deposited, is where the conversion will actually take place. An alternate to the ceramic substrate is a metallic substrate. In this process, the aluminum oxide is deposited on the metallic substrate to give the wavy contour. The precious metal is then deposited onto the aluminum oxide. Both forms of catalyst are called monoliths. 

Consider the polymer-on-metal interface, which might be prepared by coating a thin metal film with polymer in a polymer-based LED. The case of the counter electrode, formed by vapor-deposition, is discussed subsequently. First, assume that the substrates have clean surfaces hydrocarbon and oxide free, or naturally oxidized but still hydrocarbon free (pointed out as necessary). Typically, in connection with polymer-based LEDs, the metallic substrate could be gold, ITO (indium tin oxide) coated glass, the clean natural oxide of aluminum ( 20 A in thickness), the natural oxide which forms upon freshly etched Si( 110) wafers ( 10 A), or possibly even a polyaniline film. Dirt , which may be either a problem or an advantage, will not be taken up here. Discussions will alternate between coated polymer films and condensed model molecular solid films, as necessary to illustrate points. 

In view of the above applications and of the fact that extensive literature is actually available on the CVD of aluminum, copper, and tungsten, processing of nickel films has been chosen in this chapter as an introduction to the actual challenges in the CVD of metals. This field is large, especially if it is considered to include deposition on substrates such as preforms, membranes or, particles. Because of space limitations no attempt has been made to provide a comprehensive overview. Although the choice of materials to be discussed was of necessity subjective, it is expected that the present approach will be useful for the investigation of different cases of metal CVD. 

Fig. 5.6 The aluminum deposit on the different metal substrates with different electrolysis time (a) electrodeposition on Cu substrate for 4 h, (b) electrodeposition on nuld steel substrate for 4 h, (c) electrodeposition on mild steel substrate for 6 h, and (d) electrodeposition on stainless steel substrate for 6 h...

It is known that deposition on substrates where nonconductive metal oxide layers are formed at positive potentials is difficult. This includes electrodes made of stainless steel, tantalum, and aluminum. However, the rate of oxide formation is important because we have shown that stainless steel is an ideal substrate for deposition of some PPy s. The rate of oxide formation depends on the solution and the electrochemical conditions employed. If the polymer can deposit before the onset of metal oxide formation, then consistent films of excellent quality can be deposited. This is aptly demonstrated with the successful electrocoating of aluminum when the electrocatalyst Tiron 4 is used. 

Obviously, the rate of deposition of copper is the slowest on the aluminum surface followed by iron and zinc, respectively. The rate of copper deposition is a consequence of the rate of the dissolution of metallic substrates on which the reaction takes place. Similarly, as above, dependencies of the rate of the dissolution of aluminum, iron, and zinc on time are schematically given in Fig. 9.8. 

Fvmctionalized CNTs are attached to metal substrate (nickel, copper, aluminum, gold, or platinum) by electrophoretic deposition after dispersion and charging in a high concentration colloidal suspension take place. The composite is baked onto metal substrate at 500°C in H2. 

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