1,720,970 research outputs found
Heritage Conservation and Restoration: Surface Characterization, Cleaning and Treatments
No full textPolydimethylsiloxane (PDMS) /ZrO2-doped ZnO nanocomposites as protective coatings for stone materials
No full textImproving the protective properties of Shellac-based varnishes by functionalized nanoparticles
No full textShellac is a natural varnish still known as one of the most elegant finishes for furniture and musical instruments, and currently used for restoration and refinishing of wooden antiques. However, it displays some limitations such as (i) sensitivity to alcoholic solvents (ii) softness of the coating, and (iii) considerable weathering due to photo-and bio-degradation. Hence, the main aim of this study was to improve the properties of shellac-based finish by introducing functionalized nanoparticles. Two inorganic nano-sized materials were considered: ZnO that was expected to reduce photo-and bio-degradation problems, and ZrO2 that was expected to improve the hardness of the varnish. Nanoparticles were synthesized and treated with a bifunctional silane coupling agent. Both plain and functionalized nanoparticles were extensively characterized using different experimental techniques. Functionalized nanoparticles were grafted on shellac through a reaction involving the epoxy-rings introduced on their surface. The resulting modified varnishes were applied on maple wood specimens according to traditional procedures. Different instrumental techniques and testing methods were used to characterize both nano-sized materials and the corresponding nanocomposites, as well as to evaluate the performance of the new coatings. The investigated composite materials display the same aesthetic appearance as plain shellac, while some other properties were improved. In particular, both nanocomposites are distinctly less soluble in alcohols than plain shellac and display antifungal properties. Moreover, coating containing functionalized ZnO nanoparticles displays photoprotection behavior, while shellac modified with ZrO2 nanoparticles exhibits a higher hardness when compared to the traditional varnish
Improving wood resistance to decay by nanostructured ZnO-based treatments
No full textIn this study, the maple wood surface was coated with nanostructured zinc oxide, grown on the surface by using a hydrothermal process, and furtherly treated with shellac varnish. Samples obtained both after ZnO treatment and after the final varnish application were characterized by different techniques, i.e., X-ray diffraction (XRD), scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS), micro-FTIR with attenuated total reflectance (μ-ATR-FTIR), chromatic variation measurements, and contact angle determinations. Analytical results showed that the wood surface was covered by quite a homogeneous array of inorganic nanoparticles and that the natural resin forms a regular film over the ZnO nanostructures. An accelerated aging test was used to evaluate the protecting effectiveness of the treatments towards UV-induced decay of wood material. After the test, wood treated with ZnO and with the shellac/ZnO combination underwent a considerably lower chromatic change if compared to the untreated wood, suggesting an enhanced resistance of the treated maple to the decay due to light exposition. The presence of nanostructured ZnO protects from decay not only the wood substrate but also the shellac film. A microbiology test showed that growth of fungal species, e.g., common mold, is prevented on the wood surface treated with ZnO or with shellac/ZnO, indicating that the nanostructured zinc oxide also provides an effective protection from biodeterioration. The coating obtained by consecutive application of nanosized ZnO particles and shellac varnish combines the excellent aesthetical features and water repellence of the traditional finish with the protecting effectiveness of the nanostructured inorganic component
Consolidation of bio-calcarenite stone by treatment based on diammonium hydrogenphosphate and calcium hydroxide nanoparticles
No full textIn the past decades, interest in using nanomaterials for preservation of valuable cultural heritage items rapidly increased. In the present study, a method for the consolidation of weathered calcareous stone (i.e. Lecce Stone) by diammonium hydrogenphosphate and calcium hydroxide nanoparticles, which provide hydroxyapatite, is evaluated. Stone specimens were artificially weathered by several wetting-drying and freezing-thawing cycles, then they were treated with Ca(OH)2 nanoparticles in alcoholic dispersion and diammonium hydrogenphosphate (DAP) in water solution. The mineralization process affording hydroxyapatite was carried out in situ at room temperature, by mimicking the growth mechanism of bone. Ca(OH)2 nanoparticles were synthesized and characterized by X-ray powder diffractometry (XRPD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and dynamic light scattering (DLS). The progression of apatite in stone substrate was studied by using XRPD. Treatment efficacy was evaluated by measuring physical-structural properties such as water capillary absorption, permeability to water vapour, chromatic variation, porosity, surface cohesion and the resistance to salt crystallization. Morphological and microstructural features as well as distribution of the deposited phase on the surface and into the stone substrate were examined by SEM-EDS experiments. Experimental measurements suggest that the neoformed hydroxyapatite is highly concentrated on the stone surface with a consequent increase of the surface cohesion, while its diffused presence in depth induces also a moderate enhancement of resistance to salt crystallization. This work confirms that biomimic formation of hydroxyapatite represents a very promising method for the conservation of calcareous materials such as Lecce Stone
Enhanced Gd Doped TiO2 NPs-PDMS Nanocomposites as Protective Coatings for Bio-Calcarenite Stone: Preliminarily Analysis
No full textThe main objectives of this research are the development and characterization of pure and Gd-doped TiO2 nanoparticles (NPs) with low doping amounts (doping ions/Ti ratio varies between 0.1 and 3 mol%) and self-cleaning activity to be used when mixed with binder as protective coatings on monument surfaces. The prime objectives of this study are to synthesize nanopowders with controllable nanosize particles, spherical shape, anatase phase, and enhanced photo-response activity. Different coatings composed of as-synthesized nanoparticles and binder were applied to stone samples (Lecce stone). The developed coatings are intended to induce negligible colourimetric variation on the treated surface, have a good water repellence feature, and have a good distribution on the studied stone. XRD, DLS, SEM, and UV-Vis analyses were performed to analyze TiO2 NPs. The efficiency of the as-prepared NPs was estimated by testing their photocatalytic activity under UV and visible light. Chromatic measurements, static contact angle measurements, optical microscope observations, and SEM-EDS analysis were performed to analyze thin films applied to Lecce stone. The results showed that samples doped with low concentrations (≤1 mol%) of gadolinium in conjunction with PDMS can be considered as good candidates for protecting monument surfaces for this type of stone
Durable Polymer Coatings: A Comparative Study of PDMS-Based Nanocomposites as Protective Coatings for Stone Materials
No full textNowadays, durable protective coatings receive more attention in the field of conservation for several reasons (they are cost effective, time consuming, more resistance, etc.). Hence, this study was focused on producing a multi-functional, durable coating to protect different stone materials, especially, Lecce stone, bricks, and marble. For this purpose, ZrO2-doped-ZnO-PDMS nanocomposites (PDMS, polydimethylsiloxane used as the binder) were synthesized by in situ reaction (doped nanoparticles were inserted into the polymer matrix during the synthesis of PDMS)
and the performances of resulting coatings were examined by handling different experimental analyses. In particular, the study aimed to evaluate the durability properties of the coating along with the self-cleaning effect. As a result, the durability of the nanocomposite coating with respect to the well-known PDMS coating was assessed after exposure to two different ageing cycles: solar ageing (300 W, 1000 h) and humid chamber ageing (RH > 80%, T = 22 3 C, desiccator, 2 years). All the results were in good agreement with each other providing that newly prepared nanocomposite coating can be used as a durable protective coating for different stone materials
Recent Advances in the Application of Metal Oxide Nanomaterials for the Conservation of Stone Artefacts, Ecotoxicological Impact and Preventive Measures
No full textEvaluation of commercial consolidating agents on very porous biocalcarenite
No full textNowadays, the conservation of heritage buildings is an essential and important event. Different kinds of materials are available for restoring both natural and artificial stone substrates, and new commercial products have been proposed in recent years. In the present research work we investigated the effectiveness of an alkylalkoxysilane-based commercial consolidant (named VP5035) with respect to the well known tetraethoxysilane (TEOS, commercially labeled as DN). The two products were evaluated when applied on laboratory specimens of a very porous bio-calcarenite, i.e. Lecce stone (PL). Different experimental techniques were used to investigate the performances of both commercial products. At first, chromatic variation, static contact angle, water capillary absorption, permeability to water vapor were measured in order to evaluate the effects induced by treatments on the stone surface. The properties of treated stone were also investigated by Fourier-Transform InfraRed (FTIR-ATR) and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS). Measurements concerning surface cohesion and resistance to weathering effect induced by salt crystallization were performed in order to evaluate the consolidation performances of the two consolidants. These results suggest that the commercial product VP5035, when applied on Lecce stone displays a promising dual consolidating-protective behaviour
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