Preparation of aluminosilicate fiber-SiBOC composite foams for thermal protection applications

In this study, aluminosilicate fiber-embedded SiBOC matrix composite foams are realised by a simple, cost-effective and easily scalable method. Aluminosilicate wool is transformed into a compressible preform using polyvinyl alcohol as a binder. The preforms are impregnated with methylvinylborosiloxane (MVBS), followed by heat treatment at 1400°C in an inert atmosphere. The composite foam's density, compressive strength and thermal conductivity are modulated in the ranges 0.71–0.46 g/cc, 0.79–0.39 MPa and 0.21–0.13 Wm⁻¹K⁻¹, respectively, by varying MVBS concentration from 29 to 54 wt.%. While the incorporation of aluminosilicate fibers was observed to lower the thermal conductivity of the composite foams, it did not contribute to their compressive strength. Exposure of the foams to air at 1300°C for 90 min didn't change their density, while it increased the compressive strength by up to 46% due to improved fiber-matrix adhesion and rounding of cracks.