Phase segregation in binary SiO2/TiO2 and SiO2/Fe2O3 nanoparticle aerosols formed in a premixed flame

Binary SiO2/TiO2 and SiO2/Fe2O3 nanoparticle (diameter < 100 nm) aerosols of varying mole ratios of Ti or Fe to Si were generated in a premixed Bunsen-type aerosol flame reactor. The distribution of species within the particles was investigated using transmission electron microscopy, electron energy loss spectrometry, x-ray diffraction, and Fourier transform infrared spectroscopy. Phase segregation was observed to varying degrees in qualitative agreement with segregation expected from binary phase diagrams for the bulk systems. Differences between the SiO2/TiO2 and SiO2/Fe2O3 systems can be explained by considering the variation in the thermodynamically stable liquid-phase solubility and differences in the ability of iron and titanium ions to substitute for silicon ions in the network structure.