Insight into pyrolysis of hydrophobic silica aerogels: Kinetics, reaction mechanism and effect on the aerogels

[Display omitted] •The thermal pyrolysis products of silica aerogels were carefully investigated for the first time.•The pyrolysis process was discussed based on TG-FTIR data, and the probable pyrolysis mechanism was proposed.•The excellent properties of hydrophobic silica aerogels were destroyed during pyrolysis.•Thermodynamic parameters indicate hydrophobic silica aerogels possess potential for combustion. Silica aerogels have promising applications in thermal insulation, but their flammability and reaction mechanisms have rarely been investigated. The pyrolysis kinetics and thermodynamics of hydrophobic silica aerogels under N2 environment were studied. The kinetic and thermodynamic parameters were obtained by three model-free methods. Based on the calculated kinetic parameters, the pyrolysis mechanism of silica aerogels was discussed by the master plots method. The results indicate that the reactions of the whole pyrolysis phase can be characterized by a random nuclear model. In addition, FTIR test results show that the volatile products of silica aerogel pyrolysis are mainly hydrocarbons generated by the decomposition of hydrophobic groups (methyl groups) on the surface. Finally, the effects of pyrolysis on the properties of silica aerogels Finally, the effects of pyrolysis on the properties of silica aerogels were investigated based on the analysis results of SEM, specific surface area, pore size distribution, X-ray diffraction, XPS and infrared spectroscopy.