Abstract: To improve the thermal stability and coal spontaneous combustion inhibition effect of gel foam, SiO₂ nanoparticles were used as reinforcing agents in this study. The effects of SiO₂ nanoparticles on gel foam solution were systematically investigated through foam mixture property characterization, foaming performance test, thermal stability experiment and simultaneous thermal analysis experiment. The reinforcement mechanism of SiO₂ nanoparticles on the thermal stability of gel foam was revealed, and the inhibition characteristics of modified gel foam on coal spontaneous combustion were analyzed. The results showed that SiO₂ nanoparticles had a significant regulatory effect on the properties of gel foam solution. With the increase of its concentration, the surface tension of foam solution increased first and then decreased, while the conductivity and viscosity decreased first and then increased. SiO₂ nanoparticles reduced the foaming performance of gel foam, and the higher the concentration, the more obvious the attenuation of foaming performance. When the mass fraction of SiO₂ nanoparticles was 1.5%, the volume attenuation and drainage process of gel foam under thermal action could be effectively delayed, the thermal insulation performance of foam was significantly improved, and thus its thermal stability was enhanced. The gel foam modified by 1.0% SiO₂ nanoparticles could significantly increase the characteristic temperatures of coal samples, effectively weaken the heat release intensity in the coal oxidation process, reduce heat accumulation, and significantly inhibit the low-temperature oxidation and thermal decomposition stages of coal spontaneous combustion through physical inhibition. This study provides experimental basis and theoretical support for the application of nanoparticle-reinforced gel foam in the field of coal spontaneous combustion prevention and control.

Key words: SiO2 nanoparticles, gel foam, foam thermal stability, coal spontaneous combustion, inhibition effect