Preparation of Water Suspensions of Nanocalcite for Cultural Heritage Applications

Abstract

The consolidation of degraded carbonate stone used in ancient monuments is an important topic for European cultural heritage conservation. The products most frequently used as consolidants are based on tetraalkoxy- or alkylalkoxy-silanes (in particular tetraethyl-orthosilicate, TEOS), resulting in the formation of relatively stable amorphous silica or alkylated (hydrophobic) silica inside the stone pores. However, silica is not chemically compatible with carbonate stones; in this respect, nanocalcite may be a suitable alternative. The present work concerns the preparation of water suspensions of calcite nanoparticles (CCNPs) by controlled carbonation of slaked lime using a pilot-scale reactor. A simplified design of experiment was adopted for product optimization. Calcite nanoparticles of narrow size distribution averaging about 30 nm were successfully obtained, the concentration of the interfacial agent and the size of CaO being the most critical parameters. Primary nanoparticle aggregation causing flocculation could be substantially prevented by the addition of polymeric dispersants. Copolymer-based dispersants were produced in situ by controlled heterophase polymerisation mediated by an amphiphilic macro-RAFT (reversible addition-fragmentation transfer) agent. The stabilized CCNP aqueous dispersions were then applied on carbonate and silicate substrates; Scanning Electron Microscopy (SEM)analysis of cross-sections allowed the evaluation of pore penetration, interfacial binding, and bridging (gap-filling) properties of these novel consolidants.

Preparation of Innovative Skin Compatible Films to Release Polysaccharides for Biobased Beauty Masks

“…To reduce this inconvenient, the addition of micrometric calcium carbonate was attempted at 7% by weight (BM 2AV and BM SMART) ( Table 2). Calcium carbonate was selected because it is a safe and cheap material largely available in different granulometries [27,28] and can be modified by surface treatments. Indeed, it is used in biopolyester formulations without detrimental loss of properties [29].…”

Inspecting adhesion and cohesion of protectives and consolidants in sandstones of architectural heritage by X-ray microscopy methods

“…Upon hydrolysis and condensation of the silane units, the sols give rise to organosilica gel networks, which are able to fix onto the silicatebased matrix of sandstones by virtue of unreacted silanol groups. The organosilica gel imparts water-repellent features to the products [26], while the presence of TiO 2 nanoparticles is expected to add photocatalytic and self-cleaning properties [35] and reduce the shrinkage of the gel [36].…”

“…In the framework of the EU-funded Nano-Cathedral Project (grant agreement No 646178), aimed at synthesizing and testing innovative nano-structured products [26,27] for the preservation of historical architecture [28], the evaluation of the suitability of the products was carried out by integrating different methodologies and laboratory tests [26,27,[29][30][31][32]. The new nanomaterials, that is, protectives and consolidants formulated by companies involved in the project, were previously tested by laboratory routines in order to evaluate their effectiveness over time.…”

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

“…In addition to the nano-composites described in the previous sections, other hybrids based on nano-particles have been proposed for applications on materials of the Cultural Heritage. The most common products are: nano-calcite in acrylic matrices [108,109], chemically more compatible with carbonate stones, as an alternative to silica-based treatments; nano-silver particles [110] or Cu-nano-particles [111] in acrylate/methacrylate polymers, to impart antimicrobial properties; silica-calcium oxalate hybrids as consolidants [112]; nano-hydroxyapatite in silane/siloxane matrices for stone consolidation and protection [87,113]; cellulose nano-crystals in UV-light curable in siloxane-modified methacrylic resin for wood protection [6].…”