Carbon-fiber felt reinforced carbon/alumina aerogel composite fabricated with high strength and low thermal conductivity

The objective of this research was to develop a high-strength carbon-fiber felt reinforced carbon/alumina aerogel (CF-C/Al₂O₃) with low thermal conductivity. The carbon-fiber felt reinforced resorcinol formaldehyde/alumina aerogel (CF-RF/Al₂O₃) was initially prepared using sol­gel technique followed by ambient pressure drying technique. The CF-C/Al₂O₃ was obtained after the thermal treatment at 1600 °C under flowing argon atmosphere. Both CF-RF/Al₂O₃ and CF-C/Al₂O₃ displayed extremely little linear shrinkages due to the high structural strength of carbon fiber felt. The compression strength of CF-C/Al₂O₃ were 0.50, 0.78, 1.30 and 2.35 MPa, the corresponding compressive stress at the strains of Ɛ _20%, Ɛ _30%, Ɛ _40% and Ɛ _50%, respectively. The thermal conductivity of CF-C/Al₂O₃ is as low as 0.284 W/(m·K) at a ultrahigh temperature 1600 °C under argon, which is only about one half of the value of carbon fiber felt (0.538 W/(m·K)). The as-synthesized CF-C/Al₂O₃ possessed greatly controllable and stable structure, which would be fabricated and machined to a large-scale composites and be used as high temperature thermal insulators.