Processing and Characterization of Coating and Thin Film Materials

Abstract

Coatings and thin film materials are employed in many different industrial fields for decades, mainly for protective purposes. This large experience provokes that, currently, a wide variety of technologies for preparation and characterization of these materials are available. Particularly, focusing on energy and environmental applications, three main film types can be distinguished: (1) materials with catalytic activity for hydrogen production, (2) membranes for hydrogen separation or CO2 capture, and (3) coatings for some specific fuel cell components. Membranes are especially relevant for hydrogen separation from other gases after the production unit or combining both production and separation steps in a unique equipment, the membrane reactor. The last case represents a significant advance in terms of process intensification, increasing the hydrogen production rate with a high purity and saving costs. In the last years, the relevance of these membrane materials has significantly increased, as can be denoted by the large number of published manuscripts in indexed scientific journals of high impact. In this context, this chapter summarizes the main advances in thin film membranes towards energy and environmental applications, including both preparation strategies and the most common characterization techniques. The production of all these thin films, independently of the particular application, can be carried out by different physical-chemical alternatives such as Sol–Gel methods, Electrodeposition, Electroless Plating, Physical Vapor Deposition, Chemical Vapor Deposition, Atomic Layer Deposition, or Molecular Beam Epitaxy, achieving thicknesses ranged from the nanometer scale to some microns. Each technique presents advantages and disadvantages that have to be taken into account for final applications. Moreover, the structure of the film should also be considered, being possible to distinguish amorphous or crystalline materials. All these films, independently of the composition, structure, or production technique, are usually prepared over a substrate material. Thus, the original coating surface properties can affect in a significant grade to the final properties of the film and many researchers focus their efforts on studying these effects and developing new strategies to improve the final quality of films in terms of homogeneity, thickness reduction, thermal and mechanical resistance, and adherence.