Anisotropic grain growth in diphasic-gel-derived vanadium pentoxide doped mullite

The anisotropic grain growth in diphasic-gel-derived and vanadium pentoxide-doped mullite is studied to show that vanadium pentoxide can decrease the crystallization temperature and promote the anisotropic grain growth of mullite. As the aspect ratio of elongated mullite grains strongly depends on the vanadium pentoxide concentration and sintering conditions, in this paper, the crystallization temperature of vanadium pentoxide-doped diphasic-gel is lowered to 1200 °C. The kinetic studies demonstrate that anisotropic grain growth follows the empirical equation Gn−G0n=kt, with the growth exponents 4 and 6 for the length and thickness directions respectively as 3 wt% of vanadium pentoxide is added. The grain growth is a thermal activation expressed in the Arrhenius form where the activation energies for grain growth is 501 kJ/mol for the length and 554.3 kJ/mol for the thickness directions and the growth rate constants at 1600 °C are 6.8 and 0.1 for the length and thickness directions, respectively.

► Vanadium pentoxide could decrease the mullitization temperature. ► Anisotropic grain growth followed the empirical equation Gn−G0n=kt. ► Activation energy of grain growth was 501 kJ/mol for the length. ► Activation energy of grain growth was 554.3 kJ/mol for the thickness.