A study on the properties of Zr-doped γ-Al₂O₃ xerogels hybridized with α-Al₂O₃ whiskers synthesized by solvothermal drying

Hydrophobic zirconium doped alumina xerogels and zirconium doped alumina xerogels hybridized with α-Al₂O₃ whisker were fabricated by Si(CH₃)₃ (trimethylsilyl substituent) modification of alcogels via ambient pressure solvothermal drying procedure. One-step solvent exchange and surface modification were simultaneously progressed by immersing alumina alcogels in hexamethyldisilazane/hexane solution. The synthesized Zr doped Al₂O₃ xerogels have shown increased phase transition temperature from γ-phase to α-phase over 200°C. Although phase transition temperature was increased, the porous structure of Zr-doped Al₂O₃ xerogel was collapsed over 1200°C losing its specific surface area. To maintain their porous structures at the elevated temperatures, the Zr-doped Al₂O₃ xerogels were hybridized with α-Al₂O₃ whiskers. The α-Al₂O₃ whiskers were grown at 1400°C and thus sustained its phase and structure over 1400°C. The α-Al₂O₃ whiskers in xerogels act as a pillar at elevated temperatures. As a result, Zr doped Al₂O₃ xerogels hybridized with α-Al₂O₃ whiskers maintained their porous structure over 1400°C even though there was a phase transition from γ-Al₂O₃ to α-Al₂O₃.