Preparation and Formation Mechanism of Alumina Hollow Nanospheres via High-Speed Jet Flame Combustion

Abstract

A simple and effective method for the preparation of hollow alumina nanospheres was established via a high-speed jet flame combustion process. The morphology and structure of the hollow nanospheres were investigated using TEM, HRTEM, SEM, FTIR, XRD, BET, etc. A vapors mixture of C2H5OH and AlCl3 was exhausted at high speed into a flame reactor at 150 m/s and condensed into mesoscale droplets due to the Joule-Thomson cooling effect and the entrainment of cool gases into the expanding high-speed jet. The hollow alumina nanospheres were formed after the hydrolysis of AlCl3 in the H2/air flame at about 1200 °C. The hollow alumina nanosphere was composed of nanocrystallites about 5 nm and the shell thickness was 10−30 nm. The formation mechanism of the hollow alumina nanospheres was investigated, conforming to the one-droplet-to-one-particle theory.