Tannin Based Foams Utilizing 10B-Al-N Atomic Layer Deposition

Researchers at JPL have redesigned a typical standalone ALD chamber in a way that is fully compatible with automated semiconductor processing systems, yet maintains the benefits of a conventional ALD chamber—a small-volume reaction chamber, heated sample holders, and laminar gas flow. The unique three-part ALD chamber incorporates the heater, sample transfer mechanism, and laminar gas injectors into a collapsing pancake design, which enables self-assembly within the reaction chamber. The design utilizes a facedown sample arrangement, which reduces particulate contamination compared to standard faceup ALD systems. Integration with the MBE system also ensures that the ALD chamber remains clean and contaminant-free compared with conventional shared-use, standalone ALD systems. Further, the chamber is engineered to use the fewest number of actuators and provide the greatest design flexibility for all types of host systems and ALD processes. Because no automated system currently exists that incorporates both MBE and ALD processes in one unbroken vacuum system, atmosphere exposure is unavoidable when transferring components for processing. Encapsulating ALD and MBE processing chambers offers a significant process improvement and reduces the cost of producing components with precise MBE films. This innovation is anticipated to add great value to advanced image detector processing at JPL, as well as to the semiconductor industry. Originally developed for specific use with a JPL-developed MBE system, this innovation would be useful for any semiconductor industry customer seeking to prevent atmosphere exposure to MBE films prior to ALD processing in an automated system.

High atomic number materials, such as tantalum, do not bond well to oxygen- and hydroxyl-rich surfaces, such as glass fibers. These metals often form surface oxides when layered on glass fabric, resulting in flaking of the high atomic number material off the fabric during cutting, folding, and/or handling. To improve coating durability, this invention applies a lower atomic number metal as a tie down layer first before applying the high atomic number metal layer. The tie down layer reduces oxide formation between the substrate and the high atomic number material, promoting adhesion. Titanium has shown strong adhesion with different metals and is effective at reducing oxide formation when diffusion bonded to itself or other materials. It has been shown to be effective at improving durability when thermally sprayed onto a glass fiber fabric as a tie down layer for a subsequent tantalum layer (also applied via RF plasma spray). The titanium layer is only approximately 1 mil thick but results in strong adhesion of the tantalum layer by inter-metallic or diffusion bonding. A thermal spray process may be used, as well. This innovation enables the delivery of high atomic metal coating on glass fiber fabrics and other polymeric substrates that are lower cost, lighter weight, and durable to form a flexible cloth material with Z-graded radiation shielding. Coated samples have been produced and the technology is currently at a technology readiness level (TRL) of 4 (prototype).

The ALD-Enhanced Far-to-Mid IR Camera Coating is fabricated by first applying a conductively loaded epoxy binder ~500 microns thick onto a conductive metal substrate (e.g., Cu, Al). This serves to provide high absorptance and low reflectance at the longest wavelength of interest, as well as to provide a mechanical buffer layer to reduce coating stress. Borosilicate glass microspheres are coated with a thin film metal via ALD, essentially turning the microspheres into resonators. That film is optically thin in the far infrared and approximates a resistive (~200 ohms per square) coating. Light trapped in the borosilicate glass microspheres is reflected back and forth within the glass–at each contact point, the light is attenuated by 50%. A monolayer of thin metal film-coated borosilicate glass microspheres is applied to the epoxy binder and cured, forming a robust mechanical structure that can be grounded to prevent deep dielectric charging by ionizing radiation in space. Once cured, the far-to-mid IR absorber structure can be coated with a traditional ~20-to-50 microns “black” absorptive paint to enhance the absorption band at short wavelengths, or a “white” diffusive paint to reject optical radiation. At this thickness and broad tolerance, the longwave response of the coating is preserved. Tailoring the electromagnetic properties of the coating layers and geometry enables realization of a broad band absorption response where the mass required per unit area has been minimized. While NASA originally developed the ALD-Enhanced Far-to-Mid IR Camera Coating for the Stratospheric Observatory for Infrared Astronomy mission, its robustness, absorptive qualities, and optical performance make it a significant addition to IR and terahertz imaging systems. The IR camera coating is at Technology Readiness Level (TRL) 3 (experimental proof-of-concept) and is available for patent licensing.

MAC is a zeolite based coating that captures and traps molecules in its microscopically porous structure. This microscopic nano-textured structure, consisting of large open pores or cavities, within a crystal- like structure, provides a large surface area to mass ratio that maximizes available trapping efficiency. MAC is a durable coating that is applied through spray application. These sprayable coatings eliminate the major drawbacks of puck type adsorbers (weight, size, and mounting hardware requirements), resulting in cost savings, mass savings, easier utilization, greater adsorber surface area, more flexibility, and higher efficiency. This coating works in air, as well as vacuum systems, depending on the application. There is potential for ground based spin-off applications of this coating, particularly in areas where contaminants and volatile compounds need to be collected and contained. Example industries include: pharmaceutical production, the food industry, electronics manufacturing (circuit boards and wafers), laser manufacturing, vacuum systems, chemical processing, paint booths, and general gas and water adsorption.

Oxide coatings have been used in thermal and environmental barrier layers for coatings for hot section turbine applications, among other uses. With the PS-PVD method, Glenn researchers observed the formation of a minority phase of a metastable oxide (zirconium oxide) that is usually found only in a vapor state. They found that the high temperatures and fast deposition process of the PS-PVD system incorporated nonequilibrium phases in the coating and retained them at room temperature as well as at high temperature in the absence of oxygen. The material is vaporized and condensed on the surface via a rapid quenching, essentially &#34trapping&#34 this phase in the deposited coating. The coating microstructure and composition can also be manipulated by changing the processing parameters, allowing the thickness of the coating to be tailored to a given application. Since this metastable phase is conductive, this coating can be used as (for example) an extremely sensitive (thermal or temperature) sensor. It also has very good durability and erosion resistance, making it useful as a protective and conductive coating for electronics and microelectronics. This is an early-stage technology requiring additional development, and Glenn welcomes co-development opportunities.