Ultrashort Pulsed Laser Processing of Zirconia-based Ceramics for Implant Applications

Promovendus/a: Jide Han

Promotor(en): Prof. dr. Sylvie Castagne, Prof. dr. Annabel Braem

Zirconia-based ceramics stand out as excellent materials for implant applications due to their biocompatibility, high toughness, strength, and aesthetic appeal. Laser surface texturing offers a promising technique for tailoring implant material surfaces to achieve specific functions. The study began by investigating how zirconia-alumina nanocomposites responded to ultrashort laser pulses. Surprisingly, despite zirconia having a higher melting point than alumina, when exposed to a single laser pulse, the zirconia phase melted while the alumina remained in a solid state. Through theoretical modeling, we determined that the absorption of laser energy was significantly influenced by the material's band gap. Zirconia's smaller band gap allowed it to absorb much more laser energy than alumina. This explains why zirconia could reach much higher temperatures than alumina when subjected to ultrashort pulsed laser irradiation. Consequently, we were able to selectively remove the zirconia phase from the composite's surface without causing harm to the alumina phase. In this research, we also investigated how various laser parameters and material compositions would affect laser machining performance. Additionally, the parametric study underscored the vulnerability of zirconia-alumina nanocomposites to thermal cracks. Finally, the study assessed the impact of laser surface texturing on the mechanical strength of the composite material. It was observed that after laser texturing, the flexural strength decreased due to thermal cracks. Fortunately, laser texturing of pre-sintered materials followed by sintering significantly improved the material's flexural strength.