New Consolidant-Hydrophobic Treatment by Combining SiO2 Composite and Fluorinated Alkoxysilane: Application on Decayed Biocalcareous Stone from an 18th Century Cathedral

Abstract

An effective procedure has been developed to consolidate and hydrophobize decayed monumental stones by a simple sol-gel process. The sol contains silica oligomer, silica nanoparticles and a surfactant, preventing gel cracking. The effectiveness of the process on biocalcareous stone samples from an 18th century cathedral has been evaluated, and it was found that the gel creates effective linking bridges between mineral grains of the stone. Silica nanoparticles produced a significant increase in the mechanical resistance and cohesion of the stone. The application of an additional fluorinated oligomer onto the consolidated stone gave rise to a surface with lasting hydrophobicity, preventing water absorption.

The Antifungal Properties of Super-Hydrophobic Nanoparticles and Essential Oils on Different Material Surfaces

“…For the protection and consolidation of stone materials and inhibition of their capillary absorption, different silica nanoparticles or hybrid nanocomposites were developed and also tested on cultural heritage objects [35][36][37][38]. In our study, the antifungal properties, which were not treated before, were investigated as well.…”

Novel Attribute of Organic–Inorganic Hybrid Coatings for Protection and Preservation of Materials (Stone and Wood) Belonging to Cultural Heritage

“…Silicon dioxide nano-particles (from 0.1% to 8%) have been added to polymer based on silanes/siloxanes [37][38][39], fluoropolymers [40,41], polyurethanes [42,43], polyurethane-acrylate [44], methacrylic resins [45,46], unsaturated polyester resin [47], DGEBA-amine epoxy resins [48,49]. In these hybrids, silica nano-particles usually have dimensions around 7-14 nm in mean diameter [37,38].…”

“…The higher the nanosilica consistency the more the possibilities of agglomeration phenomena, which took place for nanosilica content above 2% [50]; for similar or higher amount of nano-particles, cracks and grooves are observed in some places of the layer [37,50,57] (Figure 8). The stone treated with a hybrid obtained by sol-gel process usually exhibits crack-free mesoporous coating on the surface; furthermore, numerous bridges linking together the grains of minerals in the stone can be observed [41,53,54] (Figure 9). The stone treated with a hybrid obtained by sol-gel process usually exhibits crack-free mesoporous coating on the surface; furthermore, numerous bridges linking together the grains of minerals in the stone can be observed [41,53,54] (Figure 9).…”

Inorganic Nanomaterials for Restoration of Cultural Heritage: Synthesis Approaches towards Nanoconsolidants for Stone and Wall Paintings

“…The sol composed of silica oligomers and NPs polymerizes in situ under outdoor conditions with a surfactant once it is applied to the stone by spraying. The formed crack‐free coating fills the pores of the decayed stone …”

“…The xerogels increase the mechanical resistance of the stone and create a hydrophobic coating without any negative effects on the treated stone. As an alternative, this silica nanocomposite can combine with a fluorinated alkoxysilane hydrophobic layer, which, once applied after polymerization of the xerogel, creates a chemical bond between them …”