Preparation of a Graphene-Enhanced Hydroxyapatite Film on Dolomitic Marble by the Sol-Gel Method

Abstract

The preparation of continuous hydroxyapatite film on stone is a promising method of protecting marble from erosion. However, many methods negatively affect the calcium in the substrate and forming of struvite on the dolomite surface, leading to a heterogeneous coating and low efficiency. In this study, a continuous hydroxyapatite coating on dolomitic marble was achieved from graphene enhanced Ca(OH)2 nanoparticles as the calcium precursor using the sol-gel method. The morphology and the structure of the film was evaluated by a field emission scanning electron microscope coupled with energy dispersive spectroscopy (FESEM-EDS), an optical microscope, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and analytical techniques. Moreover, the color and the contact angle measurements, as well as the simulated acid rain test and freeze–thaw treatment, were performed to assess the chromatic aberration, hydrophilicity, reliability, and durability of the coating. A suppositional combination model among hydroxyapatite, graphene quantum dots, and dolomite were suggested based on structural similarities between the support material and components of the functional coating. The integrality and efficiency of the hydroxyapatite film was improved by compositing with graphene quantum dots.