Synthesis, Mechanical And Chemical, Characterization Of Vanadium- Based Aerogels

Abstract

Monolithic aerogels are highly mesoporous materials that have low density, low thermal conductivity, low dielectric constant as well as high acoustic impendence, a few of the properties that make them attractive for wide range of applications in thermal and acoustic insulation, electronics, separations and catalysis. However, fragility, hydrophilicity, as well as the requirement for drying using supercritical fluid extraction has limited the actual use to only specialized space applications or as Cerenkov radiation detectors in some types of nuclear reactors. Recently, the fragility problem was solved by casting a conformal polymer coating over the skeletal framework of typical silica aerogels prepared via a base-catalyzed sol-gel method (Leventis et al. 2002). That framework consists of a pearl-necklace like three-dimensional assembly of nanoparticles. The applied polymer coating cross-links the nanoparticles by developing covalent bonding with their surface and reinforces the structure without clogging the pores. Thus, the density typically increases by a factor of 3, while the strength at failure increases by a factor of 300 with a remaining porosity at 70% (Leventis et al. 2002; Zhang et al. 2004; Bertino et al. 2004). Cross-linked samples are able to deform by over 77% compressive strain without developing surface cracks, and remain stable when saturated with water.