Effect of laser induced rapid solidification structures on adhesion and bonding characteristics of alumina/silica based oxide to vitreous enamel

<p>The present work is concerned with investigating the effects of high power diode laser (HPDL) radiation on themicrostructure of an amalgamated alumina/silica based oxide compound (AOC). The main rapid solidificationtheories, namely constitutional supercooling and the theory of morphological stability, are used to explain theobserved microstructural changes in the AOC resulting from HPDL interaction. Without laser treatment of theAOC surface it was impossible to fire the enamel onto the AOC. However, wetting experiments, using a number ofcontrol liquids and the sessile drop technique, revealed that laser treatment of the AOC surface significantly alteredthe wetting characteristics of the AOC and allowed the enamel to bond to the AOC. Accordingly, HPDL treatmentwas identified as allowing the vitreous enamel to wet the surface by causing a decrease in the enamel contact anglefrom 118° to 33°. Moreover, no discernible difference was seen in the change in contact angle across the range ofrapid solidification microstructures obtained. The actual incidence of rapid surface resolidification, and not thedegree of rapid surface resolidification, was therefore identified as being the primary factor governing changes incontact 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 usedto alter the wetting characteristics of the AOC.</p>