Low-cost porous thermal insulation materials with tunable pore structures derived from fly ash by foam-gelcasting

Abstract

In order to adjust the pore structures and improve the thermal insulation property and mechanical strength of fly ash-based insulation materials prepared by a foaming gel-casting technique, the rheological behaviors of foaming slurries were adjusted. Furthermore, the effects of heating temperatures on the properties and microstructure of the insulation materials were investigated. The results showed that as the content of the dispersant increased, the viscosity of slurries increased first and then decreased. When the content of the dispersant reached 0.2 wt.%, the slurries showed excellent flow ability, which caused a lot of big pores to generate in the matrix. Moreover, the thickening agent, binder and solid content had a great influence on the thixotropy of the slurries. As the content of the thickening agent and binder were 0.25 wt % and 5.0 wt.%, respectively, the slurries with 45 wt.% solid content exhibited outstanding thixotropy, which was beneficial to improve the stability of generated closed pores. After treating at 1300°C for 2 h, the bulk density, compressive strengths, and thermal conductivity of the insulation materials prepared using the optimized slurries were 0.44 g cm−3, 3.27 MPa, and 0.13 W·m−1·K−1, respectively.