Nanoscale size dependence on pulsed laser sintering of hydroxyapatite/titanium particles on metal implants

Nanoscale size effects on pulsed laser coating of hydroxyapatite/titanium nanoparticles (nanoTi) on metal substrate is discussed in this article. Laser coating method has recently been developed to coat bioceramics material on Ti-6Al-4V substrate. Laser-coated bioceramics implants have several advantages due to the use of nanosized materials: strong interfacial bonding strength, good biocompatibility and potentially longer lifetime cycle. These advantages benefit from intrinsic properties of nanoparticles. Size effects on melting point, heat capacity, thermal, and electrical conductivities have been discussed. Multiphysics model is built to reveal the mechanism of laser coating process. Two submodules are included in the model: electromagnetic module to represent the laser-nanoparticle interactions and heat transfer module to simulate the heat conduction. Both simulation and experimental results showed that nanoTi, functioning as nanoheaters, effectively enhances the laser coating sinterability. For large nanoTi ( > 100 nm ) , sinterability enhancement mainly attributes to the stronger laser-particle interactions due to higher plasmon resonance; for small nanoparticles ( < 100 nm ) , not only stronger laser-nanoparticle interactions, reduction on melting point also contributes to sinterability enhancement.