Improved mechanical and thermal insulation properties of monolithic attapulgite nanofiber/silica aerogel composites dried at ambient pressure

Abstract

To overcome the brittleness and the dry shrinkage of silica aerogels, natural attapulgite nanofiber is successfully used as reinforcement for monolithic silica aerogel composites possessing ultralow density and excellent thermal insulation properties. The attapulgite/silica aerogel composites are obtained by dispersing the acid-treated attapulgite fibers in silica sol, followed by aging and ambient pressure drying. The acid treatment of attapulgite fibers obviously improved the adhesion between silica aerogel and attapulgite fibers surface. The microstructure analysis showed that silica particles firmly adhered to the surface of the rod shaped crystal of attapulgite fibers, which played a supporting role as structure skeleton and substantially improved the integrity and mechanical strength of the aerogel composites. No obvious variation of the mesoporous silica structure was observed since the nanosized attapulgite fibers are effectively incorporated into the network, instead of separated into small fragments as pure aerogel shown. As the fiber content increased, the density decreased to 0.163 cm3/g first and then increased, while the thermal conductivity increased slightly with ranging between 0.0198 and 0.0228 W m−1 K−1. The aerogel samples with compression strength varying from 0.8 to 2.5 MPa were obtained. All these promising characteristics indicated that ATP/silica aerogel composites have diverse applications, especially in heat preservation field.