Aerosol processing is a well established method to produce submicron particles for technologies like pigments and sinterable ceramics. Although the particle size distribution often controls the quality of the final product, this parameter cannot currently be measured on-line because of the dense particle streams. In addition, the number density and temperature of the particles in the reactor are also unknown. This proposal is a combined research effort by Advanced Fuel Research, Inc. and the University of Maine to develop a sensor for particle analysis of high-temperature gas reaction mixtures. The sensor will be on-line and in-situ and will deconvolute the Fourier Transform Infrared spectra to yield the particle size distribution. The Phase I research will demonstrate the technology by deconvoluting the measured infrared spectra of known TiO2 particles to yield an accurate size distribution. A simple laboratory scale flame will show that in-situ measurements are feasible. Phase II research will include extensive research on a TiO2 flame in an industrial laboratory. The final step of Phase II will be a field test on a commercial TiO2 reactor.