Robust monolithic polymer(resorcinol-formaldehyde) reinforced alumina aerogel composites with mutually interpenetrating networks

Abstract

Monolithic polymer(resorcinol-formaldehyde) reinforced alumina (RF/Al₂O₃) aerogel composites were prepared using a sol–gel method and supercritical fluid CO₂ drying. The formation mechanism, chemical compositions, pore structures, morphologies, thermal and mechanical performances of RF/Al₂O₃ aerogel composites with different RF/Al molar ratios were investigated. The results show that the two networks of organic resorcinol-formaldehyde and inorganic alumina are completely independent of one another. The as-synthesized RF/Al₂O₃ aerogels consist of spherical organic carbon particles and fibrous alumina, which possess low bulk density (0.077–0.112 g cm⁻³), low shrinkage (1.55–2.76%), low thermal conductivity (0.024–0.028 W m⁻¹ K⁻¹), and high specific surface area (453.26–722.75 m² g⁻¹). Especially, the sample prepared with molar ratio RF/Al = 1 shows the best network structure with the higher compressive strength (1.83 MPa) and Young's modulus (122.57 MPa). The resulting robust RF/Al₂O₃ aerogel composites could be potentially used as thermal insulators, catalysts and adsorbents.