Abstract View
Flame Aerosol Synthesis of Mesoporous Silica and Porous Ceramic Nanospheres
Shuo Liu, Satyarit Rao, Mihir Shah, MARK SWIHART, University at Buffalo - SUNY
Abstract Number: 55
Working Group: Nanoparticles and Materials Synthesis
Abstract
Over nearly three decades since Mobil researchers developed the self-assembled template method for synthesis of mesoporous silica, this class of materials has been broadly applied in catalysis, separation and purification, sensors, and biomaterials based upon its high porosity, ordered pore morphology, and tunable surface groups. Later, researchers developed the aerosol-assisted self-assembly method to produce mesoporous silica in a process similar to spray drying. Until now, no such high porosity mesoporous silica has been produced by flame aerosol technology because the high temperature typical of flame synthesis would destroy the organic template and collapse the pores. Moreover, flame synthesis of silica, e.g., production of fumed silica, generally proceeds by a gas-to-particle conversion route that is inherently incompatible with templating. Here, we report the production of nanoparticles of mesoporous silica using a unique flame aerosol reactor configuration that separates the flame chemistry and particle formation process into different regions, which allows a much lower reaction temperature. In this process, a liquid solution of precursor and surfactant is injected into the throat of a converging-diverging nozzle, placed downstream of a hydrogen-oxygen flame. The nozzle accelerates the hot combustion gases, which atomize the precursor solution. Solvent evaporation, surfactant self-assembly and silica formation occur in each droplet, during the ~50 ms residence time in the aerosol reactor downstream of the nozzle. The droplets are much smaller and the residence time is much shorter than in traditional aerosol-assisted self-assembly processes. With this approach, after calcination to remove the surfactant template, we produced mesoporous silica with a BET surface area of more than 1000 m2/g, entirely in the form of submicron spheres. This approach is also generalizable to other materials, and we are preparing other mesoporous metal oxides by the same process.