Novel three-dimensional halloysite nanotubes/silica composite aerogels with enhanced mechanical strength and low thermal conductivity prepared at ambient pressure

Abstract

Novel three-dimensional halloysite nanotubes (HNTs)/silica composite aerogels were fabricated to strengthen the nanostructure and overcome inherent fragility of silica aerogel by a sol–gel method using tetraethyl orthosilicate (TEOS) and 1,4-Phenylene diisocyanate (PPDI)-modified HNTs (p-HNTs) as the main materials, followed by an environmentally friendly ambient pressure drying (APD). The modification and dispersion of HNTs were investigated by using FTIR, SEM, TEM. Meanwhile, the morphology, mechanical properties, and thermal conductivity of aerogels were also studied. The results showed that the p-HNTs were uniformly dispersed in the silica aerogel. This resulted in composites with unique interpenetrating network microstructure that could give an enhanced mechanical properties to aerogels. The compressive strength was found to vary from 400 kPa to 1.45 MPa and thermal conductivity from 0.025 to 0.038 W/m K. In addition, randomly oriented p-HNTs can obviously reduce both the linear shrinkage and density of composite aerogels. The composites with outstanding properties prepared by APD are potential for building applications.