Nathaniel Olson
University of Illinois at Urbana-Champaign
The extreme environments of space exploration have pushed scientists to create revolutionary materials that have filtered back to terrestrial life. A key challenge is lightweight insulation to replace dense ceramics for aerospace applications, where every pound is worth $10,000. A promising new form of insulation is aerogels because they are highly porous, with randomly cross-linked chains which form air-filled pores, creating solid structures that are up to 99% air. The main issue preventing use of aerogels in high temperature applications is lack of stability at elevated temperatures. Silica aerogels densify and lose their favorable porous structure at 700 degrees C. Alumina aerogels densify to form to alpha-alumina at 1300 degrees C; however, with addition of silica, phase transformation to transitional aluminas is slowed, allowing them to maintain a mesoporous structure at 1100 degrees C for times of greater than 96 hours, and at 1200 degrees C for greater than 24 hours. Although a porous structure is maintained, these aluminosilicate aerogels undergo successive phase transformations that degrade their favorable thermal properties. Yttria-stabilized zirconia (YSZ) aerogels are a candidate for a highly porous, lightweight material that can withstand temperatures to 1200 degrees C without phase transformation. YSZ is a high temperature ceramic that currently is used in thermal barrier coatings. In this study, YSZ aerogels will be synthesized and characterized for use in high temperature applications for spacecraft. Several sol-gel synthesis routes to monolithic YSZ aerogels will be investigated. The aerogels will be characterized extensively to reveal effects of composition and synthesis conditions on phase transitions, morphology, and surface area. This study provides information on the structural and thermal properties of YSZ aerogels and how these properties can be tuned by modifying synthesis conditions and composition for high temperature aerospace applications such as re-entry vehicles, space probes, and rovers.