Ion-Substituted Carbonated Hydroxyapatite Coatings for Model Stone Samples

Abstract

Carbonated hydroxyapatite derivatives (CHAp) and its metallic derivatives (Ag, Sr, Ba, K, Zn) have been prepared and characterized in this paper and their coating capacity on some model stone samples have been evaluated and discussed. These compounds were characterized by using several analytical tools, including X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), to determine the purity of the CHAp sample. The XRD and FTIR results confirmed the presence of AB-carbonated type CHAp. The thermal analysis (TGA) established two stages of weight loss that occured during the heating process: The first weight loss between 30–225 °C corresponding to the partial carbonate release from OH-channel and the second one between 226–700 °C, corresponding to some thermal reactions, possibly to the generation of calcium phosphate. The efficiency and suitability of these products on model stone samples were evaluated by monitoring the resistance to artificial weather (freeze–thaw), and pore structure changes (surface area, pore volume, pore diameter). Meanwhile, optical microscopy (OM) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM–EDS) techniques showed the particles size and surface morphology of the samples, as well as information on its chemical composition. Also, the compressive strength of these new compounds as coatings revealed a homogeneity and strengthen of these model stone samples.