Thermal stability and pyrolysis characteristics of MTMS aerogels prepared in pure water

Silica aerogel (SA) is a nanoporous material and has attracted increasing attention in the field of thermal insulation in recent years. In this work, the thermal stability and pyrolysis characteristics of the methyltrimethoxysilane (MTMS) silica aerogel (MSA) prepared in pure water were investigated experimentally. The MSA shows a high thermal stability with the onset and peak temperature (T_onset and T_peak) about 417 °C and 476 °C, respectively, in the pyrolysis process. The oxidation kinetics reveals that the pyrolysis of MSA can be divided into three stages with the average apparent activation energy (E) of each stage being 382.8 kJ/mol, 364.4 kJ/mol, and 328.9 kJ/mol, respectively. The pre-exponential factor (A) has the same tendency with the E. The TG-FTIR analysis demonstrates that the CO₂ and H₂O are the main volatiles during the pyrolysis process and all of them increase against the temperature. It is further observed that the production of CO₂ presents a linear increase, and the H₂O shows an obvious two-stage form along with the temperature. Compared with other hydrophobic SAs, the MSA has a larger T_onset and T_peak and much larger E, indicating better thermal safety. The research outcomes provide a technical guide to analyze the thermal pyrolysis of hydrophobic SA and put a new insight to reduce their thermal hazards, which is beneficial to the development of higher-performance nanoporous silica aerogels for the thermal insulation field.