The synthesis of metal oxide-based xerogels via the epoxide addition and sacrificial template method

Abstract

This study describes a new sol-gel synthesis method to produce nano-structured, porous metal oxides. The purpose of this hybrid method is to reduce the total production time needed for most sol-gel syntheses. A typical sol-gel synthesis requires fours steps: selection of precursor solution, formation of sol-gel, aging of sol-gel, and drying of the sol-gel network. The last two processing steps are time-consuming and can take up to two weeks to complete. The new sol-gel method combines the epoxide addition method and the sacrificial template method. The epoxide addition method consists of adding an epoxide to a metal salt precursor solution to produce a sol-gel. The sacrificial template method consists of impregnating a template with a precursor solution to form a paste, and then annealing the paste to remove the template. The combination method places a sacrificial template inside of a metal salt precursor solution and an epoxide is added to form a sol-gel. All undesired products, hydrocarbons and template, are removed in one simple annealing step. The total process time is reduced from 1-2 weeks to 1 day. It was discovered that nano-structured, high surface area metal oxides could be successfully produced. The addition of the template to the sol-gel increased the stability and strength, or robustness, of the final product. The solubility of the sacrificial template in the metal salt precursor solution and the dwell time of the annealing heat cycle were key factors that ensured the success of the hybrid method. The hybrid method provides shorter process time period relative to most sol-gel synthesis processes.