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This innovative NASA process begins with the deposition of an Al layer onto an optically smooth glass substrate using a high-vacuum PVD system. Unlike conventional methods where the Al surface is immediately exposed to air or coated with LiF, this new technique entails an initial exposure of the fresh Al film to XeF2 gas. This step chemically passivates the Al surface, forming a thin (~2.5-3.2 nm) protective layer of aluminum fluoride (AlF3). This barrier prevents oxidation and contamination of the aluminum before the LiF layer is applied, preserving its reflectivity. Following the XeF2 treatment, a flash-evaporated LiF overcoat is deposited onto the Al surface using a conventional PVD process. Deposition is performed at a high rate to increase the density of the LiF layer, enhancing its environmental stability and optical performance. Immediately after the LiF deposition, the mirror undergoes a second XeF2 exposure, further passivating the surface. This dual XeF2 treatment is key to the improved durability of the mirrors, as it effectively seals the interfaces and prevents degradation over time. One of the most significant advantages of this process is that it is performed entirely at room temperature, eliminating the need for high-temperature deposition techniques conventionally used for such coatings. Extensive testing of these new mirrors has demonstrated their performance and durability. Testing of prototypes optimized for 121.6 nm demonstrated 92.6% reflectivity, surpassing all previously reported values for Al/LiF coatings. Long-term environmental testing has shown that these mirrors maintain their high reflectance even after months of storage in moderate humidity conditions. Further stress testing in environments with 50-60% humidity for three weeks resulted in a reflectance reduction of about 2%, demonstrating high environmental stability. This NASA invention is available for patent licensing to industry.

NASA’s PLED thermal inspection system consists of an array of high- powered LED chips configured to deliver controlled pulses of visible light. The system includes 8 LED chip arrays, mounted on an aluminum heat sink and housed in a hood configuration. The inspection hood is specially designed with filters to prevent internal reflections. The LEDs are powered by regulated power supplies and controlled via a computer interface that synchronizes heat pulses with an infrared camera. An acrylic filter is placed over the LEDs to block residual infrared radiation, ensuring that only visible light reaches the target surface. The system’s infrared camera, operating in the mid-wave infrared (MWIR) range does not detect the visible light and captures the transient thermal response of the material, allowing for precise defect detection. By eliminating the need for high-intensity broadband infrared sources, the PLED system provides a cleaner and more accurate thermal response, particularly for unpainted metals and additively manufactured (AM) components. Performance validation of the PLED system has demonstrated significant advantages over traditional flash thermography. In tests on aluminum samples with material loss and AM Ti-6Al-4V metal specimens, the PLED system successfully detected defects with superior contrast and no heat source reflections. Principal Component Analysis (PCA) applied to PLED inspection data revealed clearer defect indications compared to flash-based methods, which introduced unwanted artifacts due to transient reflections. Additionally, the PLED system enabled quantitative thermal diffusivity measurements, offering a new approach to single-sided material characterization. NASA's PLED thermal inspection technology is available for patent licensing. Potential applications include corrosion detection in aerospace components, quality control of AM metal parts, structural health monitoring of industrial materials, and more.