Synthesis of a ZrO2/carbon aerogel composite with tetragonal ZrO2 structures assisted by the formation of phenol formaldehyde resin

Abstract

In this study, monoclinic ZrO₂ nanoparticles were successfully prepared using a hydrothermal process. When phenol was added to the resulting solution for the hydrothermal reaction, ZrO₂/phenol formaldehyde (PF) resins with tetragonal ZrO₂ crystalline phases were synthesized. Tetragonal ZrO₂ crystalline phases favor growth in solutions with high pH values and high OH⁻ concentrations, which result from the formation of PF via the reaction of phenol and formaldehyde. Consequently, the transition of monoclinic ZrO₂ to tetragonal ZrO₂ is assisted by PF formation. Furthermore, tetragonal ZrO₂/CA structures with a high specific surface area of approximately 275.7 m² g⁻¹ were successfully prepared through carbonization of the resulting ZrO₂/PF structures, which greatly improved the aggregation phenomenon of ZrO₂ nanoparticles with a specific surface area of ca. 16.1 m² g⁻¹. This study is the first report of the fabrication of tetragonal ZrO₂ crystallites with the assistance of the formation of phenol formaldehyde resins during hydrothermal reactions. This method could be applied to other metal oxide crystallite systems in the future.