EVALUATION OF NONMETALLIC COATINGS AND FILMS FOR THERMAL CONTROL APPLICATIONS

An evaluation of the thermophysical and tribological properties of nonmetallic coating materials has been conducted in order to determine which materials are most suitable for thermal enhancement applications. These nonmetallic materials consist of oxides, carbon-based coatings, ceramics, and polymer-based coatings. The thermal conductivity, mechanical, electrical, and tribological properties have been summarized for comparison. Among the oxides, beryllia (BeO) was selected as a potential coating because of its high thermal conductivity in comparison to other oxides. Anodic coatings processed at room temperature result in soft coatings which may lead to improved heat transfer. Carbon-based coatings, such as polycrystalline diamond or diamond-like films, offer excellent thermophysical and tribological properties which makes them attractive as coatings. Ceramics generally exhibit excellent structural and thermal capabilities at high temperatures, however, they are extremely hard and prove to be more suitable for thermal isolation applications. Polymer-based coatings have excellent properties for environmental applications and provide good dimensional and structural stability over a wide range of temperatures.