Abstract: In this paper, silica aerogel with different amounts of CTAB surfactant were prepared by acid base two-step method using tetraethyl orthosilicate as silicon source and hexadecyl trimethyl ammonium bromide as surfactant. The effects of surfactant on the microscopic morphology, lattice structure, thermal insulation and fire resistance of aerogel were studied. The results show that the SiO₂ aerogel prepared by the acid base two-step method is a typical amorphous silica. The aerogel is formed by the accumulation of nanoparticles, and the particle size is between 30~80 nm. The addition of CTAB reduces the particle size of the SiO₂ aerogel, and the skeleton is condensed. The compression strength of the aerogel is improved. The compression strength of the SiO2 aerogel with 0.1 mol of CTAB reaches the maximum value of 1.216 MPa. At 800 ℃, the maximum carbon residue of SiO₂ aerogel with 0.1 mol CTAB content is 81.4%, the minimum thermal conductivity is 0.019 W/（m·K）, and the thermal insulation performance is the best. The shortest vertical combustion time of SiO₂ aerogel with 0.1 mol CTAB was 8.1 s, the maximum LOI value was 34.8%, and the vertical combustion grade reached V1. The combustion rate of aerogel in the combustion process weakened, and the flame retardancy was significantly improved.

Key words: SiO₂ aerogel, CTAB, mechanical properties, micromorphology, flame retardancy, thermal stability