Infrared-Transparent, Electrically Conductive Coating

The ability to function in a broad range of operational conditions drives the IR windows and domes on Advanced Aircraft and Missiles. In addition to transparency, these windows and domes have to provide additional functionality such as EMI shielding, anti/de-fogging, and anti/deicing. Each of these functions requires that, in addition to being transparent, the window or dome has to be at least partially conductive. In most cases, the conductivity is added through the use of coatings or patterned metallic grids. For visible applications, transparent conductive coatings like indium tin oxide (ITO) are available. However, these coatings become highly absorbing at longer wavelengths. For MWIR and LWIR applications conductivity are generally provided by patterned metal grids, which are not transparent and produce scattering and reflections. Grids are made to work when there is no alternative; however, a suitable transparent conductive coating is clearly preferable for advanced applications like the targeting system of the F-35 Joint Strike Fighter (JSF). In this effort, Surmet proposes to use a layered coating approach for sensor windows with high transparency in the MWIR and sheet resistances lower than 10 ohms/sq. Coated samples will also be tested for sand and rain erosion using in-house equipment.