Macroparticle distribution and chemical composition of laser deposited apatite coatings

Abstract

We have studied the effect of pulsed laser ablation conditions on the deposition of biocompatible apatite coatings on Ti and Ti–6Al–4V alloy at room temperature. We have made detailed analyses of the spatial distribution of the macroparticles (MP) and of the Ca/P ratio in the coatings. We find that (i) two types of MP are observed, differing in size, shape, and stoichiometry, and (ii) the size distribution of the MP has a maximum depending on the laser fluence and gas pressure in the deposition chamber. Manipulation of the laser deposition conditions allows fine control over both morphology and stoichiometry of coatings. Experimental results are explained on the basis of a theoretical model which includes the analysis of cluster-type ablation mechanisms due to the high pressures of gas evolved in thermal decomposition of the target material under laser irradiation.