8-9th August, 2008 School of Materials Science & Nanotechnology,Jadavpur University
Nanocrystalline Low Temperature Mullite Formation by Sol-Gel Technique.
Biswajoy Bagchi, Dr. Sukhen Das.
Physics Department, Jadavpur University Kolkata 700032
Abstract.
Mullite, or porcelainite, is a rare clay mineral with the chemical composition Al6Si2O13, a form of aluminium silicate. It is produced artificially during various melting and firing processes, and is used as a refractory. Mullite research is gaining importance because of the excellent properties it exhibits such as high thermal and chemical stability, high creep resistance, low thermal coefficient of expansion and good dielectric properties.
Synthesis of mullite by sol-gel technique using suitable precursors is advantageous due to the fact that the reactants are mixed at molecular level ensuring chemical homogeneity.
Transition metals have been shown to have a mineralizing effect on the transformation of Kaolinite to Mullite ceramics with accelerated decrease of surface area and pore volume. These transition metals distort the local ligand symmetry(Jahn-Teller effect) which results in accelerated phase transformation in substrates i.e. at a lower temperature.
Mullite formation by conventional methods require a temperature of over 10000C with reaction completing at around 16000C. In our work we have synthesized nanocrystalline mullite at a temperature as low as 6000C by using sol-gel technique. Particle size have been calculated to be within 13-30 n.m.. This drastic lowering of the mullitization temperature is a direct consequence of a doping agent in the form of a transition metal.This metal actually forms a complex with the reactant and by distorting the local ligand symmetry brings down the temperature of mullitization.
Corresponding author: biswajoy_ju@rediffmail.com
Custom Search
