MORPHOLOGY OF SINGLE-COMPONENT PARTICLES PRODUCED BY SPRAY-PYROLYSIS

This work is a review of the experimental results from the literature for single-component metal and simple metal-oxide particles. Criteria for correlating particle morphology, i.e., whether the particles are s olid or hollow, with process parameters and material properties during spray pyrolysis are presented and compared with the data available in the literature. The materials were classified into two categories for which the precursor: (1) melts and (2) does not melt before chemical reaction takes place, and separate criteria were used for each categor y based on the work of Jayanthi et al. (1993) J. Aerosol Sci. 19:478. In systems where the precursor melts before chemical reaction occurs, e.g., decomposition of nitrates of Mg, Al, Fe, Zn, Pb, Ni, Co, Pd, Mn, Cu, Sr, and Ag, the particle morphology is determined primarily by th e densities and formula weights of the reactant and product compounds unless high temperature densification or puffing up of the particles d ue to gases evolved during the chemical reaction alter the morphology. In systems where the precursor undergoes nucleation to form a solid c rust which does not melt before chemical reaction takes place, e.g., B a(C2H3O2)(2), Al-2(SO4)(3), Zr(C2H3O2)(2), and Zn(C2H3O2)(2), solubili ty and density of the precursor as well as the operating temperature a re the main factors that affect the product particle morphology. Overa ll, particle morphologies predicted by the criteria were in agreement with experimental observations reported in the literature. (C) 1997 Am erican Association for Aerosol Research.