Uniform pore structure silica aerogel powders prepared by pore repair method

Nowadays, the rapid preparation of silica aerogel powders by ambient pressure drying (APD) method has been widely studied. However, the internal pore structures of the aerogel powders prepared by the conventional rapid aging method (CM) are difficult to be controlled due to the increase in the particle agglomeration and the macropores structure. In this research, a rapid way was introduced to control the microstructure of the silica aerogel powders through pore repairing (PR) method in the aging process. The bulk gel and gel particles were double aged to enhance the skeleton structure of gel particles. The new silica nanoparticles were formed, and filled in the macropores of gel particles by adhesion or deposition in the networks of gel particles during the late ageing process, the pore structure in the gel particles were uniform within just 2 h of aging. Under optimal ageing conditions, silica aerogel powders with low density (0.089 g/cm 3 ), low thermal conductivity (0.0243 W/m K) and high specific surface (882 m 2 /g) was obtained through the pore repairing method. Pore repairing method in the aging process has certain research significance to control the pore structure of aerogel powders. Graphical Abstract Graphical abstract shows the schematic illustration of the silica aerogel powders preparation process by pore repairing method. In the pore repairing method, the block gel was formed by mixing silica sol and ethanol solution under basic condition. After a short period of preliminary aging in the aging liquid prepared by mixing with ethanol and tetraethoxysilane, the silica network structure with certain strength was formed in the block gel. Then, the preliminary aged block gel was mechanically crushed into a number of gel particles, and the gel particles were put into the aging liquid to further age. The new generated silica nanoparticles in the aging liquid can fill the macropore of gel particles by deposition on the networks of silica aggregates or form new Si–O–Si cross-linking structures via condensation between hydroxyl groups or hydrogen bonding interaction to obtain the repaired gel particles. Highlights The study of controlling the pore size distribution of silica aerogel powder was discussed for the first time. The pore repairing method endows the silica aerogel powder with uniform pore structure. The pore structure in the gel particles were uniform within just 2 h of aging. The thermal conductivities experiences were decreased from 0.0301