Engineered Coatings for Aerospace Thermal Management

The challenging flight conditions experienced by hypersonic vehicles leads to conflicting requirements between maintaining thermal survivability in a high temperature, highly oxidizing environment and ensuring effective radio frequency and infrared sensor functionality. This results in either sub-optimal sensor performance, active cooling with its concomitant issues of added weight, volume, complexity, and reliability, or constraints on vehicle trajectories to protect the sensor. New, high-temperature materials and coating systems, properly designed, engineered, and produced at an affordable price – as demonstrated by the Nanoionix, LLC Nanoionix/Johns Hopkins University Applied Physics Laboratory (JHUAPL) team – could address these critical issues and provide the Department of the Air Force with both improved capabilities and decreased procurement, operating and maintenance costs. The Nanoionix/JHUAPL team have demonstrated exceptional capabilities to design and synthesize multicomponent metal oxides with intricate control of composition, phase, stoichiometry, spectral and electrical properties, and for designing, fabricating, and evaluating the thermal, spectral, and durability attributes of coating systems made from these materials. This includes two families of materials with either broadband high emissivity (>0.9 from 2 to 15 microns) with ~100% RF transparency from 10 – 40 GHz which maintains this transparency to at least 1000°C or controlled spectral emissivity (>0.8 at 1 micron and <0.02 at 3 microns and transparency out to 12 microns). Both can withstand temperatures up to 1500°C in air for at least one hour – a minimum temperature requirement requested by the Air Force Research Laboratory. The team has shown that coatings made from these materials can cool the underlying substrate by over 400o C (from >1400oC to less than 1000oC). During the proposed Phase II effort, the Nanoionix/JHUAPL team will further optimize the performance and thermal stability of these materials and scale their synthesis to more than 1 kilogram per day. Coatings will be deposited using processes already employed by Defense suppliers on key substrate materials and on notional full-scale prototype radio frequency radomes and infrared windows. Testing in relevant environments will ensure that these coatings meet the thermal/oxidative stability and performance requirements established by the Air Force Customer and End User. The goal of the Phase II effort is not to replace existing radio frequency radomes or infrared window materials, but to augment their performance by adding coatings to address their inherent limitations.