The effects of high-power diode laser radiation on the wettability, adhesion and bonding characteristics of an alumina/silica-based oxide and vitreous enamel

An amalgamated alumina/silica-based oxide compound (AOC) was surface treated using a 60 W high-power diode laser (HPDL). The effects of the HPDL radiation treatment of the AOC on its wettability and adhesion characteristics to a subsequently deposited vitreous enamel have been determined. The basic process phenomena are investigated and the effects of laser irradiation in terms of composition and microstructure are presented. Without laser treatment of the AOC surface it was not possible to fire the enamel onto the AOC. However, wetting experiments using a number of control liquids, by the sessile drop technique, revealed that laser treatment of the AOC surface resulted in the polar component of the surface energy increasing after laser treatment from 2.00 mJ m^-2 to 16.15 mJ m^-2. Additionally, surface roughness measurements revealed that, after laser treatment, the surface roughness had decreased from an R(a) value of 25.85 μm to 6.27 μm, whilst an energy-dispersive X-ray analysis (EDX) revealed that the relative surface oxygen content of the AOC had increased by 36.29% after laser treatment. Thus, laser treatment was identified as effecting a decrease in the enamel contact angle from 118°to 33°; consequently allowing the vitreous enamel to wet the surface. The bonding mechanisms were identified as being principally due to van der Waals' forces; however, some evidence of chemical bonding was observed. The work has shown clearly that laser radiation can be used to alter the wetting characteristics of the AOC.