Evaluation of Sintering of Nanometer-Sized Titania Using Aerosol Method

The sintering of titania agglomerates consisting of nanometer primary particles in a heated gas flow is investigated under gas temperatures from room temperature to 1673 K. The test titania agglomerates are produced by thermal decomposition or hydrolysis of TTIP (titanium tetraisopropoxide) vapor. The size changes of the agglomerates of 30-100 nm in diameter are measured using a TDMA (Tandem Differential Mobility Analyzer) system. At a temperature lower than about 1000 K, the agglomerates do not change in size with increasing heating temperature, but a sudden decrease in size is detected at 1000 to 1500 K. From TEM observation, densification of agglomerates accompanying primary particle growth is observed. These experimental results for the rate of reduction in surface area are explained quantitatively by solving the basic equation of sintering under the calculated temperature profile.