Synthesis and application of hydroxyapatite nanorods for improving properties of stone consolidants

This study aims at preparing novel composite materials for the consolidation of damaged stone in built heritage from tetraethoxysilane(TEOS)based sols with nano-sized hydroxyapatite (HAp) with high crystallinity and high aspect ratio. Synthesis of nanostructures of hydroxyapatite (HAp) was carried out using hydrothermal precipitation methods at different reaction temperatures and periods. Rod-like HAp nanostructures with a diameter around 5–20 nm and length up to 125 nm were obtained. The samples of nano-HAp were characterised using powder X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and μ-Raman spectroscopy. The derived nanostructures were used to modify TEOS-based formulations after tuning their colloidal stability period to the needs of their application as stone consolidants. The chemical structure (μ-Raman), viscosity, macroscopic and microscopic morphologies – Scanning Electron Microscopy (SEM) and EDS – and Shore Hardness of the composite materials were studied. The potential of the composite materials containing nano-HAp-rods as stone consolidants revealed to be superior to the potential of reference materials.