Transmission Electron Microscopy Study of Growth of Silica Nanoparticles in the Flame Synthesis Process by Thermophoretic Sampling Technique

The mechanism of evolution of silica nanoparticles is studied by the thermophoretic sampling method and TEM analysis. The formation of flame synthesized silica nanoparticles from primary particles to agglomerated particles was studied in a diffusion flame of hydrogen and air by oxidizing Tetra Ethyl Ortho Silicate (TEOS) vapor at various location of the flame. The average particle diameter was measured at different heights from top surface of the burner by a controlled thermophoretic sampling technique and subsequent imaging of the particles in Transmission Electron Microscopy (TEM). Based on the combustion product characteristics as obtained from TEM, an attempt has been made to understand the nanoparticles formation. It is suggested; initially the primary particle goes to the end of the luminous flame but then level off. The particle residence time, flame temperature, particle aggregations are the key parameters which have been described in this paper.