Date of Award
University or Center
Clark Atlanta University(CAU)
Sol-gel processing methods were used to prepare mullite ceramic powder form high purity aluminum tri-sec butoxide and tetraethylorthosilicate solutions under different processing conditions. the effects of the processing conditions on the sol to gel transition were examined by varying the water ratios, pH and temperature. Prehydrolysis of the silicon alkoxide was used since the aluminum alkoxide reacts faster than the silicon alkoxide. It was observed that the variation in temperature has the greatest effect on the time to gelation for the precursors. The rheological properties during the aging process indicated an increase in viscosity with age time, which is consistent with change in structure. Measurements of the viscoelastic properties during the sol to gel period showed a predominance of the loss (viscous) modulus over the storage (elastic)modulus in the initial stages of stages of aging. With increased aging of the sols and gels, large elastic components were observed which is consistent with structure build-up. The changes in structural evolution were followed by Fourier Transform Infra-red spectroscopy and correlated well to changes in the rheological properties of the sol. TG/DTA and X-ray analyses were used to correlate the starting chemistry and reaction condition to the microstructure of the final mullite powder. In all experimental cases fine grain mullite powder were obtained indicating no apparent differences of the synthesis conditions on the final mullite powder microstructure.
Oluwa, Omoyele A., "A study of the sol-gel system for the preparation of mullite" (1996). ETD Collection for AUC Robert W. Woodruff Library. 3255.