The electrical conductivity of anodized aluminum thermal control coating will be enhanced by pyrolytic deposition of an electronically conducting metal oxide within the anodic oxide pores. The electrical charge that might otherwise accumulate on its surface in the ambient space plasma, e.g., under Space Station Freedom grounding conditions, will leak off through the coating. This will prevent erosion of the metal structure by sputtering at coating breaks, and minimize electrical noise. The amount of pyrolytic oxide needed to achieve suitable conductivity is likely to be too small to significantly increase coating absorptivity on structural alloys. The conductive oxide deposition conditions will be compatible with a conventional anodizing line, and with thermal limitations of the anodic oxide and substrate alloy. The project objective is to produce coatings with enhanced conductivity and acceptable absorptivity by selection of conductive oxide type and deposition conditions, in combination with possible modifications to anodizing process steps. In Phase I, the emphasis will be on using one particular pyrolytic oxide, but conductivity and breakdown voltage will be measured of coatings prepared with combinations of two anodic oxides and two pyrolytic oxides.A conductive coating offers a simple and low cost solution to several problems that arise from the insulating properties of the conventional anodic oxide. It provides electrical continuity over an anodized aluminum surface for electromagnetic interference compatibility. It will prevent the buildup of static electrical charge on anodized surfaces exposed to the flow of liquids or gases. An important application may be as the protective coating on aluminum hardware used in semiconductor wafer fabrication plasma chambers. A conductive oxide will reduce sputtering at coating defects that generates microscopic particles that deposit on the silicon wafer and result in "killer" defects in the microelectronic circuits.
Keywords: Phase_I, NASA, Abstract, FY94
