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.
Highlights
Nowadays, one of the main difficulties in preserving objects and heritage monuments is to select the most adequate treatment methods for stone protection, able to preserve their original appearance, without any detrimental effect on their aesthetic properties [1]
The aim of this paper is to synthesize and to test some consolidants based on carbonated hydroxyapatite (CHAp), which is quite similar with hydroxyapatite [17,18,19]
The results show that insertion of the metals into Carbonated hydroxyapatite derivatives (CHAp) lattice led to a higher SBET that is correlated with smaller crystallite sizes of these samples [37]
Summary
One of the main difficulties in preserving objects and heritage monuments is to select the most adequate treatment methods for stone protection, able to preserve their original appearance, without any detrimental effect on their aesthetic properties [1]. The main challenges in stone protection are related to the creation of a barrier against water penetration and protection of the stone surface against pollutants and the deposition of organic/inorganic particles, while ensuring aesthetic compatibility with the substrate (i.e., color changes at acceptable intervals), a minimal change in water vapor permeability and reversibility of the treatment [3]. In this perspective, hydrophobic coatings [4], antifouling treatments [5] and nanoparticle self-cleaning bands [6] are currently at the center of research on stone conservation [7,8]
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