Autoclave Design for Microgravity Hydrothermal Synthesis

Microgravity offers an enticing synthetic knob for materials scientists to explore—however, this environment creates major challenges in hardware development that can turn a simple 3-day experiment into a 3-year long nightmare. This paper provides an overview of engineering an autoclave, compatible with NASA’s Solidification Using a Baffle in Sealed Ampoules (SUBSA) furnace, to enable microgravity hydrothermal synthesis—an acceleration-sensitive technique that processes aqueous samples above the boiling point of water. Hydrothermal synthesis is a universal chemical transformation technique that is used to produce a range of advanced materials with applications in alternative energy, healthcare, and the food industry. In this work, we use the synthesis of graphene hydrogel as a case study to verify our hardware design on Earth before launching to the International Space Station for microgravity testing. The design addresses pertinent challenges which include enabling thermal expansion while preventing air bubble formation in solution and implementing a pressure fail-safe above the maximum operating temperature. Our goal in presenting this autoclave design is to provide a step forward towards commercial-of-the-shelf microgravity hardware.