SCHEDULED MAINTENANCE
Super-hydrophobic hexamethyl-disilazane modified ZrO2–SiO2 aerogels with excellent thermal stability
Abstract
Hexamethyl disilazane modified ZrO2–SiO2 aerogels (HMDS/ZSAs) have been prepared by the addition of HMDS into ZrO2–SiO2 gels during the aging process in order to improve their thermal stability at high temperature. FTIR analysis shows that the methyl siloxy groups ((CH3)3Si–O–) could replace the superficial hydroxy groups (–OH) through the condensation between the (CH3)3Si–OH of HMDS and –OH on the initial ZSA surface. HMDS/ZSAs could maintain their three-dimensional network structure without collapse and exhibit a remarkable thermal stability with retention of most physical characteristics up to a temperature of 1000 °C, such as a high surface area (174.4 m2 g−1), high pore volume (0.7246 cm3 g−1) and high elastic modulus (5.23 MPa). TGA and XRD analyses demonstrate that the phase transition of HMDS/ZSAs from amorphous to crystalline occurs up to 1000 °C, which is 100 °C higher than that of ZSAs. It was demonstrated that the modified inert methyl siloxy groups could form small silicon particles (3 to 5 Å in diameter) to restrict the migration of grain boundaries, which was favorable to suppress the ZrO2 crystallization at elevated temperatures. Furthermore, HMDS/ZSAs exhibit super-hydrophobic properties with a contact angle of 154°. The high performance of HMDS/ZSAs paves the way for their applications in the field of thermal insulation, energy-absorbing services, environmental remediation, etc.
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