Morphological control of zirconia nanoparticles through combustion aerosol synthesis

Ceramic oxide nanoparticles produced by flame-based processes are typically agglomerated, which can limit their use in some applications. In this paper, a novel combustion synthesis method that utilizes the spraying of combustible droplets into a premixed flame to produce nanoscale crystalline particles of agglomerated and unagglomerated morphologies is described. Although the same flame-based experimental setup is used in both cases, variation in peak flame temperatures results in a corresponding variation between fractallike agglomerates and single isolated spherical particles. TEM/ED analysis shows that both classes of particles are the tetragonal crystal phase of zirconia. In the case of the unagglomerated spherical particles, results indicate that each precursor solution droplet, which acts as the feed, produces multiple spherical ceramic nanoparticles with a number mean diameter of 90 nm. The use of an inertial impaction stage in the precursor feed line to eliminate large feed droplets leads to a decrease in the number mean diameter to 60 nm, suggesting that crystalline spherical nanoparticles can be produced in a continuous flame-based process through control of the feed droplet size.