Preparing High-Quality Monolithic Carbon Nanotubes Reinforced Silica Aerogel Composites Based on a Vacuum Freeze-Drying Method
Abstract
In this study, using tert-butanol/water co-solvent as the freeze-drying solvent, we successfully prepared high-quality monolithic carbon nanotubes (CNTs) reinforced silica aerogel composites. The effects of CNTs on the pore structures, thermal performance and mechanical properties of the CNTs/silica aerogel composites were investigated. Generally, when the CNTs content is below 4 wt.%, the CNTs are uniformly distributed in the silica aerogel matrix due to the effective ultrasonic dispersion process. In addition, the CNTs form a good interface combination with the aerogel skeleton through the condensation of hydroxyl groups. Correspondingly, the pore structures and thermal conductivity of the composites were only slightly influenced, while the mechanical properties were greatly improved from 401.4 kPa to 658.6 kPa. However, due to the agglomeration and sedimentation of CNTs, the pore structure and the thermal insulation properties of the composite began to deteriorate when its content reached 6 wt.%, and its enhancing effect on mechanical properties also deteriorates significantly when the CNTs content reached 8 wt.%. This study provides a cost-effective process for preparing high-quality bulk CNTs/silica aerogel composites, which is beneficial for their future practical applications and commercialization.