Sorption Properties of Aerogel in Liquid Nitrogen

Aerogel products are now available as insulation materials of the future. The Cryogenics Test Laboratory at the NASA Kennedy Space Center is developing aerogel-based thermal insulation systems for space launch applications. Aerogel beads (Cabot Nanogel ) and aerogel blankets (Aspen Aerogels Spaceloft ) have outstanding ambient pressure thermal performance that makes them useful for applications where sealing is not possible. Aerogel beads are open-celled silicone dioxide and have tiny pores that run throughout the body of the bead. It has also recently been discovered that aerogel beads can be used as a filtering device for aqueous compounds at room temperature. With their hydrophobic covering, the beads absorb any non-polar substance and they can be chemically altered to absorb hot gases. The combination of the absorption and cryogenic insulating properties of aerogel beads have never been studied together. For future cryogenic insulation applications, it is crucial to know how the beads react while immersed in cryogenic liquids, most notably liquid nitrogen. Aerogel beads in loose-fill situation and aerogel blankets with composite fiber structure have been tested for absorption properties. Depending on the type of aerogel used and the preparation, preliminary results show the material can absorb up to seven times its own weight of liquid nitrogen, corresponding to a volumetric ratio of 0.70 (unit volume nitrogen per unit volume aerogel). These tests allow for an estimate on how much insulation is needed in certain situations. The theory behind the different processes of sorption is necessary for a better understanding of the preparation of the beads before they are used in an insulation system.