Abstract

The present work is concerned with investigating the effects of high power diode laser (HPDL) radiation on the
microstructure of an amalgamated alumina/silica based oxide compound (AOC). The main rapid solidification
theories, namely constitutional supercooling and the theory of morphological stability, are used to explain the
observed microstructural changes in the AOC resulting from HPDL interaction. Without laser treatment of the
AOC surface it was impossible to fire the enamel onto the AOC. However, wetting experiments, using a number of
control liquids and the sessile drop technique, revealed that laser treatment of the AOC surface significantly altered
the wetting characteristics of the AOC and allowed the enamel to bond to the AOC. Accordingly, HPDL treatment
was identified as allowing the vitreous enamel to wet the surface by causing a decrease in the enamel contact angle
from 118° to 33°. Moreover, no discernible difference was seen in the change in contact angle across the range of
rapid solidification microstructures obtained. The actual incidence of rapid surface resolidification, and not the
degree of rapid surface resolidification, was therefore identified as being the primary factor governing changes in
contact angle. The bonding mechanisms were identified as being principally owing to van derWaals forces, however,
some evidence of chemical bonding was also observed. The work has clearly shown that laser radiation can be used
to alter the wetting characteristics of the AOC.