Design, synthesis and characterization of hybrid coatings suitable for geopolymeric-based supports for the restoration of cultural heritage

Abstract

Geopolymers are inorganic materials that form long-range, covalently bonded, networks; they are materials similar to ceramics, whose components are mainly aluminium and silicates. Any inorganic source of silica and alumina, dissolved in the alkaline solution, acts as a precursor of geopolymers. The type of clays most commonly used in the synthesis of geopolymers is based on kaolinite. The present work concerns the modification of the geopolymer at the chemical and nanostructural level, through the design and development of hybrid coating sol-gel formulations to improve characteristics such as mechanical strength, chemical inertness, heat resistance and porosity for possible use in the restoration and conservation of cultural heritage. The methods of functionalization of the geopolymers here shown are: (i) the treatment of the geopolymeric surface, post-drying, through the application of the sol-gel directly on the monolith, for a modification of the surface properties; (ii) the pretreatment of the geopolymeric mixture, through the addition of the alkoxysilane which can induce a homogeneous consolidation of the molecular structure, implementing the properties of the entire monolith. The employed alkoxysilanes differ according to the length of the hydrocarbon chain and the presence of halogen atoms. Hydrophobicity tests were performed on these formulations.

Nanostructured Surface Finishing and Coatings: Functional Properties and Applications

“…Silica–based nanostructured coatings are, indeed, one of the most advanced techniques employed in nanotechnologies [ 157 ]. This type of method, which leads to the formation of organic–inorganic hybrid coatings with a nanocomposite structure, can modify some properties of the materials under study, such as the resistance to abrasion, wettability, impart antibacterial characteristics and resistance to UV radiation, in order to release bioactive substances [ 158 ]. Over time, the advantages of organic-inorganic hybrid materials were proved by several researchers, which established that these compounds are obtained from the structural incorporation of organic groups, such as, vinyl, acrylic, epoxy, amine etc., in the sol–gel precursors through Si–C bonds [ 158 , 159 ].…”

“…This type of method, which leads to the formation of organic–inorganic hybrid coatings with a nanocomposite structure, can modify some properties of the materials under study, such as the resistance to abrasion, wettability, impart antibacterial characteristics and resistance to UV radiation, in order to release bioactive substances [ 158 ]. Over time, the advantages of organic-inorganic hybrid materials were proved by several researchers, which established that these compounds are obtained from the structural incorporation of organic groups, such as, vinyl, acrylic, epoxy, amine etc., in the sol–gel precursors through Si–C bonds [ 158 , 159 ]. In detail, the inorganic part is formed by alkoxides of silicon or other transition metals through a hydrolysis reaction, whilst the organic one is constituted by molecules, which can differ in their structure from the length and branching of the alkyl chains [ 160 , 161 ].…”

Nanostructured Surface Finishing and Coatings: Functional Properties and Applications

“…Silica -based nanostructured coatings are, indeed, one of the most advanced techniques employed in nanotechnologies [153]. This type of method, which leads to the formation of organic -inorganic hybrid coatings with a nanocomposite structure, can modify some properties of the materials under study, such as the resistance to abrasion, wettability, impart antibacterial characteristics and resistance features to UV radiation, in order to release bioactive substances [154]. Over time, the advantages of organic-inorganic hybrid materials were proved by several researchers, which established that these compounds are obtained from the structural incorporation of organic groups, such as, vinyl, acrylic, epoxy, amine etc., in the sol-gel precursors through Si -C bonds [154] [155].…”

“…This type of method, which leads to the formation of organic -inorganic hybrid coatings with a nanocomposite structure, can modify some properties of the materials under study, such as the resistance to abrasion, wettability, impart antibacterial characteristics and resistance features to UV radiation, in order to release bioactive substances [154]. Over time, the advantages of organic-inorganic hybrid materials were proved by several researchers, which established that these compounds are obtained from the structural incorporation of organic groups, such as, vinyl, acrylic, epoxy, amine etc., in the sol-gel precursors through Si -C bonds [154] [155]. More in detail, the inorganic part is formed by alkoxides of silicon or other transition metals through a hydrolysis reaction, whilst the organic one is constituted by molecules, which can differ in their structure from the length and branching of the alkyl chains [156][157].…”

Multifunctional Dyeing of Wool Fabrics Using Selenium Nanoparticles

“…Nanotechnologies and nanomaterials offer a wider application potential for preparing functional textiles, such as flame retardant, self-cleaning, wrinkle-resistant, antistatic, antimicrobial, and UV-protective, etc. [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ] In recent years, several approaches to metal and metal oxide NP fabrication and application have been developed to impart functionalities to different types of textile substrates [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. In addition, nanomaterials, such as gold and silver nanoparticles, stabilized by opportune functional capping agents, have been used as a novel class of functionalizing nanofillers either themselves [ 24 , 25 , 26 , 27 , 28 , 29 ] or for the functionalization of different types of materials (such as concrete, glass, geopolymer and also embedded in coloring or antibacterial coatings), especially for textile fabrics [ 30 ].…”