Next generation thermal insulators for operation in high-temperature and humid environments through aerogel carbonization

Abstract

We generated a carbon aerogel with high thermal stability and a wider operational range by carbonizing resorcinol–formaldehyde (RF) aerogels. The carbonization process was conducted using a gas mixture that consists of 95% nitrogen and 5% hydrogen at a temperature of 800 °C. The presence of hydrogen led to the modification of the RF aerogels’ composition through the extraction of oxygen and transformation of the aerogels into two basic elements (carbon and hydrogen). When the oxygen was removed, a new carbon aerogel was produced that superseded the RF aerogel. The aerogel had a high surface area of 779.22 m² g⁻¹. This was due to the expansion in the micropore volume during the process. The carbon aerogel had higher thermal stability than the RF aerogel, with an operational range that exceeded 450 °C. The samples exhibited fire retardancy capabilities, as the time for the carbon aerogel to burn has doubled compared to that for the RF aerogel. The samples could resist moisture without compromising their structure. This was mainly due to the reduction of the samples’ hydrophilic groups. The carbon aerogels’ strength had increased, and they became more brittle than RF samples. Finally, the carbon aerogels had a thermal conductivity of 53 mW m⁻¹ K⁻¹.