engleski

Mullite ceramics acid corrosion kinetics as a function of gel homogeneity

Using the sol-gel synthesis, premullite gels with different levels of homogeneity, so called monophasic and diphasic gels, were prepared. Gels thermal transformations to mullite ceramics, as well as structural features of ceramic samples were characterized. Gels were processed into mullite ceramics at 1600°C/4h. The occurrence of glassy phase was predominately evidenced in ceramics originating from diphasic gel, while that originating from monophasic gel showed greater porosity. The behaviour of ceramics during corrosion in aqueous nitric acid solutions was evaluated by the amount of eluted ions. Both samples yield low corrosion rates with corrosion kinetics following parabolic function. In comparison with nominal composition the eluates contain higher Si4+/Al3+ ratio as a consequence of the leaching of the glassy phase. However, due to a greater porosity the ceramics derived from monophasic gels show higher corrosion rate.

mullite ; corrosion ; transmission electron microscopy ; inductively coupled plasma-optical emission spectrometry ; kinetics

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