High power diode laser modification of the wettability characteristics of an Al2O3/SiO2 based oxide compound for improved enamelling

High power diode laser (HPDL) surface melting of a thin layer of an amalgam ated Al2O3/SiO2 oxide compound (AOC) resulted in significant changes in the wettability characteristics of the material. This behaviour was identified as being primarily due to: (1) the polar component of the AOC surface ener gy increasing after laser melting from 2.0 to 16.2 mJ m(-2), (2) the surfac e roughness (Ra) of the AOC decreasing from 25.9 to 6.3 mu m after laser me lting and (3) the relative surface oxygen content of the AOC increasing by 36% after laser melting. HPDL melting was consequently identified as affect ing a decrease in the enamel contact angle from 118 degrees prior to laser melting to 33 degrees after laser melting, thus allowing the vitreous ename l to wet the AOC surface. The effective melt depth for such modifications w as measured as 50 to 125 mu m. The morphological, microstructural and wetti ng characteristics of the AOC were determined using optical microscopy, sca nning electron microscopy, energy disperse X-ray analysis, X-ray diffractio n techniques and wetting experiments by the sessile drop technique. The wor k has shown that laser radiation can be used to alter the wetting character istics of the AOC only when surface melting occurs. (C) 1999 Published by E lsevier Science S.A. All rights reserved.