Electrodeposition gradient

Figure 1.18 SEM images of regions of macroporous gold films grown with a thickness gradient by electrochemical deposition through templates assembled from either 750-nm-diameter polystyrene spheres [204]. The electrodeposition was performed at a potential of -0.90 Vsce- t> is the diameter of the sphere on top layer. The three dotted circle lines represent the spheres beneath. Reproduced by kind permission from the publisher.

Each of these combinations of materials can be considered composites on a microscale. Ceramic composites, which can be considered composites on a macroscopic scale, include laminated structures and composites that have been termed functionally gradient materials (FGMs). FGMs, which are designed to have smooth gradients in composition, have been fabricated by vapor deposition, plasma sputtering, and electrodeposition techniques. Lamination techniques are used for FGM applications in which more abrupt compositional changes are acceptable. 

The polymer-metal interface shown in Fig. was derived from an electron micrograph obtained by Mazur and Reich.They electrodeposited silver from a silver ion solution diffusing through a polyimide film. Particles not connected to the diffusion source were removed by computer analysis. The deposited silver particles essentially "decorate the concentration profile and permit the diffusion front to be observed. A 1000-A thin slice was used to aproximate two dimensional diffusion. The fractal dimension of this interface was determined by computer analysis to be approximately 1.7. Similar ramified interface fronts are created by vapor deposition of metal atoms on polymers and by certain ion bombardment treatments of polymer surfaces. The fractal front is fairly insensitive to the details of the concentration profile. However, strong chemical potential gradients in asymmetric interfaces may promote a more planar, less ramified structure. The fractal characteristics of polymer interfaces... 

Continuous gradients of electrocatalyst compositions have also been prepared as an alternative to the spot or line arrays described earlier. Methods of prodncing continnons gradients have inclnded electrodeposition across a resistive element by changing the composition of a thin-layer film (e.g., agar) by controlled solution treatment, or by spnttermg. - ... 

---