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

Abstract

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.