Low-cost, free-form optics using silicon carbide additive manufacturing

Silicon carbide (SiC) is an ideal optical substrate material due to its low density, high stiffness and low coefficient of thermal expansion. With SiC, thermal gradients during service are quickly dissipated and thermal expansion is low, thereby maintaining optical performance. However, silicon carbide has been traditionally expensive and difficult to manufacture because it cannot be readily machined and molding processes are expensive and slow. SiC produced via additive manufacturing (AM) has the potential to overcome the technical and commercial challenges to make SiC a more widely adopted material for optics. Additionally, the ability to create increasingly complex structures (both in the substrate support and in the optical surface) can enable the design of more efficient satellites and weapons. This proposal will focus on optimizing the densification process to improve the repeatability and dimensional tolerances of AM SiC for free-form optics. While prior work by the project team has shown the feasibility of using AM SiC for optics for small and microsatellites, the parts still required some amount of machining and grinding before they can be polished. With this funding, the team will develop thermal models and improved densification procedures to produce highly-toleranced SiC that can generate free-form optical surfaces. The initial target markets will be for small satellites that require free-form optical surfaces. As the process is refined, it is expected to be able to be used for larger and more complex optics. Additionally, AM SiC can be used for applications outside of optics, such as heat exchangers and automotive brake systems.