Design and Performance of Sioc Foam-Silica Aerogel Composites for Hot and Cold Thermal Management Applications

Abstract

This study focuses on the fabrication of monolithic preceramic polymer-derived ceramic (SiOC) foam-silica aerogel composites by filling the open cells of ceramic foam with a silica aerogel solution using the sol-gel technique. The effects of different drying techniques (ambient pressure vs CO2 supercritical drying) and surface modification agents, including trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ), are comprehensively investigated. These factors are analyzed for their influence on the composites' morphology, porosity, chemical structure, and thermal insulation performance. The drying technique and surface modification agents are found to play a critical role in achieving a high filling ratio of silica aerogel within the composites. Pure silica aerogels exhibit specific surface areas (SSAs) reaching ∼1120 m2.g-1, while the SiOC foam-silica aerogel composites demonstrate SSAs of 385–440 m2.g-1. Nearly all samples achieve a total porosity of ∼93 vol%. Surface modification effectively tailors the surface properties, imparting hydrophobicity with a water contact angle of 133°. Thermal conductivity at room temperature ranges between 38 and 43 mW·m-1·K-1. The potential applications of these SiOC foam-silica aerogel composites as thermal insulators are assessed under extreme thermal conditions. For instance, a 14 mm thick composite has a temperature of -27 °C when subjected to a cold source at -78 °C. Instead, when exposed directly to a butane flame (∼1200 °C), the backside of the composite recorded only ∼57 °C. © 2025 Elsevier Ltd and Techna Group S.r.l.