Novel Nano-Filled Coatings for the Protection of Built Heritage Stone Surfaces

An experimental nano-filled coating, based on a fluorine resin containing SiO2 nano-particles, was applied on calcareous stones, representative of materials used in buildings and monuments of the Mediterranean basin; for comparison purposes, two commercial products were applied on the same substrates. The efficacy of the protective treatments was assessed by analyzing different characteristics of the three experimental/commercial products, i.e., color changes and permeability to water vapor to evaluate the treatments' harmlessness; capillary water absorption and water stone contact angle to evaluate the protection against water ingress; oleophobicity of the treated surfaces and the behavior under staining by acrylic blue-colored spray paint and felt-tip marker to verify the anti-graffiti action. Finally, the properties of the treated stone surfaces were analyzed also after the application of pancreatin, used to simulate bird excreta (guano). The protective coatings were found to promote graffiti removal, reducing also the detrimental effects due to simulated guano. The experimental nano-filled product, in addition, was able to provide outstanding performance but using smaller amounts of product in comparison to commercial systems

Eco-friendly protective coating to extend the life of art-works and structures made in porous stone materials

none5noopenM. Lettieri, M. Masieri, M. Aquaro, D. Dilorenzo, M. FrigioneLettieri, M.; Masieri, M.; Aquaro, M.; Dilorenzo, D.; Frigione, M

Thermal performance of mortars based on different binders and containing a novel sustainable Phase Change Material (PCM)

Increasing concerns about climate change and global warming bring about technical steps for the development of several energy-efficient technologies. Since the building sector is one of the largest energy users for cooling and heating necessities, the incorporation of a proper energy-efficient material into the building envelopes could be an interesting solution for saving energy. Phase change material (PCM)-based thermal energy storage (TES) seems suitable to provide efficient energy redistribution. This is possible because the PCM is able to store and release its latent heat during the phase change processes that occurs according to the environmental temperature. The purpose of this paper was the characterization of the thermal properties of a composite PCM (i.e., Lecce stone/poly-ethylene glycol, previously developed) incorporated into mortar compositions based on different binders (i.e., hydraulic lime and cement). The study was carried out using an experimental set up through which it was possible to simulate the different seasons of the years. It was observed that the addition of PCM in mortars leads to a decrease of the maximum temperatures and increase of the minimum temperatures. Furthermore, the results shown a reduction of the heating and cooling needs, thus confirming the capability of this material to save energy

Polydopamine-Coated Poly-Lactic Acid Aerogels as Scaffolds for Tissue Engineering Applications

Poly-L-lactic acid (PLLA) aerogel-based scaffolds were obtained from physical PLLA gels containing cyclopentanone (CPO) or methyl benzoate (BzOMe) molecules. An innovative single step method of solvent extraction, using supercritical CO2, was used to achieve cylindrical monolithic aerogels. The pore distribution and size, analyzed by SEM microscopy, were found to be related to the crystalline forms present in the physical nodes that hold the gels together, the stable alpha'-form and the metastable co-crystalline epsilon-form, detected in the PLLA/BzOMe and PLLA/CPO aerogels, respectively. A higher mechanical compressive strength was found for the PLLA/CPO aerogels, which exhibit a more homogenous porosity. In vitro biocompatibility tests also indicated that monolithic PLLA/CPO aerogels exhibited greater cell viability than PLLA/BzOMe aerogels. An improved biocompatibility of PLLA/CPO monolithic aerogels was finally observed by coating the surface of the aerogels with polydopamine (PDA) obtained by the in situ polymerization of dopamine (DA). The synergistic effect of biodegradable polyester (PLLA) and the biomimetic interface (PDA) makes this new 3D porous scaffold, with porosity and mechanical properties that are tunable based on the solvent used in the preparation process, attractive for tissue engineering applications

Interplay of ferromagnetism and spin-orbit coupling in Sr4Ru3O10

Funding: IB acknowledges funding through the International Max Planck Research School for Chemistry and Physics of Quantum Materials, MN, CT and PW through EP/R031924/1 and EP/T031441/1 and LCR from the Royal Commission of the Exhibition of 1851. TEM measurements were supported through grants EP/R023751/1, EP/L017008/1 and EP/T019298/1. YN acknowledges support through the ERC grant ERC-714193-QUESTDO held by Phil King.The ground state of metamagnetic materials can be controlled by magnetic field, promising new functionalities for spintronics applications. Yet, a microscopic understanding of the interplay of the electronic structure with the susceptibility to emergent orders is often missing, but would greatly facilitate optimization of the properties of metamagnetic materials. Here, we use low temperature scanning tunneling microscopy (STM) and spectroscopy to study the metamagnetism in the trilayer ruthenate Sr4Ru3O10, combining STM-based magnetostriction measurements with quasiparticle-interference imaging (QPI) to elucidate the role of the microscopic electronic structure in the macroscopic metamagnetic properties. Our results highlight the importance of the orthorhombicity of the material for its metamagnetic properties, confirmed by magnetization measurements. Our QPI results show clear signatures of the minority spin bands crossing the Fermi energy, and provide a link between the ferromagnetic properties, spin-orbit coupling and the orthorhombicity of the crystal structure.PostprintPeer reviewe

Spin-orbit coupling induced Van Hove singularity in proximity to a Lifshitz transition in Sr4Ru3O10

Funding: CAM, MN and PW gratefully acknowledge funding from the Engineering and Physical Sciences Research Council through EP/R031924/1 and EP/S005005/1, IB through the International Max Planck Research School for Chemistry and Physics of Quantum Materials and LCR from a fellowship from the Royal Commission of the Exhibition of 1851. RA, RF and AV thank the EU’s Horizon 2020 research and innovation program under Grant Agreement No. 964398 (SUPERGATE).Van Hove singularities (VHss) in the vicinity of the Fermi energy often play a dramatic role in the physics of strongly correlated electron materials. The divergence of the density of states generated by VHss can trigger the emergence of new phases such as superconductivity, ferromagnetism, metamagnetism, and density wave orders. A detailed understanding of the electronic structure of these VHss is therefore essential for an accurate description of such instabilities. Here, we study the low-energy electronic structure of the trilayer strontium ruthenate Sr4Ru3O10, identifying a rich hierarchy of VHss using angle-resolved photoemission spectroscopy and millikelvin scanning tunneling microscopy. Comparison of k-resolved electron spectroscopy and quasiparticle interference allows us to determine the structure of the VHss and demonstrate the crucial role of spin-orbit coupling in shaping them. We use this to develop a minimal model from which we identify a new mechanism for driving a field-induced Lifshitz transition in ferromagnetic metals.Peer reviewe

Performances and Coating Morphology of a Siloxane-Based Hydrophobic Product Applied in Different Concentrations on a Highly Porous Stone

Many polymers, able to confer a hydrophobicity to treated surfaces, have been proposed for the restoration and conservation of civil and monumental buildings. Polysiloxanes, and their precursors, the silanes, have been frequently employed for stone protection. To avoid decay of the treated surfaces, the effectiveness and harmlessness of the treatment need to be carefully evaluated before application in the field. In this study, a commercial alkyl-siloxane was tested as a protective treatment on a highly porous stone, starting from water solutions with different contents of the product. The treatments have been devised to try to balance the requirements and the sustainability of the conservative actions. Sustainability, in terms of costs and environmental impact, is regarded as a key factor in the 21st century. Morphological observations of the stone surface, static contact angle and colour measurements, water vapour transmission test, and tests of water absorption were carried out to characterize the untreated and treated stones. A concentration below the minimum level suggested by the manufacturer was still able to act as a good barrier against water. More concentrated solutions produced polymer accumulation and coatings with extended cracks. The properties of the treated stone were affected by the presence of cracks in the coating

Eco-Friendly Protective Coating to Extend the Life of Art-Works and Structures Made in Porous Stone Materials

The application of hydrophobic treatments to stone surfaces is the most common proven method to prevent, or at least limit, the degradation of stone-made constructions and artworks brought about by the ingress and action of water, in particular in the case of very porous stone materials. To avoid the use of protective products containing harmful solvents, new green products have been proposed. In this paper, an eco-friendly hydrophobic coating, based on a fluorine polymer dispersed in water, was deeply analyzed to evaluate its protective properties, especially for very porous stone substrates. To this aim, a wide characterization of treated and untreated Lecce stone elements, i.e., a stone typical of the Apulia region, was carried out to assess the optimum required amount, the effectiveness and the protective capability, even against graffiti staining, of the green hydrophobic treatment, still allowing the stone to retain adequate vapor permeability. The efficacy of the eco-friendly product was analyzed also after a short time (four weeks) of outdoor exposure. Suitable performance and short-term durability of the green hydrophobic coating were found, comparable or even greater than those reported in the current literature for other widespread commercial products, confirming the capability of the product to preserve porous stone surfaces even in absence of solvents in its formulation. The study also allowed to experiment with the “contact sponge” test as an appropriate method for evaluating the water absorption properties of the stone

Novel attribute of organic-inorganic hybrid coatings for protection and preservation of materials (stone and wood) belonging to cultural heritage

In order to protect a material belonging to Cultural Heritage (i.e., stone, wood) from weathering, and in turn to preserve its beauty and historical value for the future generations, the contact with external harmful agents, particularly water, must be avoided, or at least limited. This task can be successfully obtained with the use of a protective organic coating. The use of nano-metric reinforcing agents in conventional polymeric coatings demonstrated to be a successful route in achieving better protective performance of the films and improved physical properties, even in extreme environments. The present paper would, therefore, review the more recent findings in this field. Generally speaking, when a hydrophobic product is applied on its surface, the stone material will absorb less water and consequently, less substances which may be harmful to it. An efficient organic coating should also supply wear and abrasion resistance, resistance to aggressive chemicals, excellent bond to the substrate; finally, it should be also able to guarantee vapor exchange between the environment and the material interior, i.e., the material should keep the same water vapor permeability as if it was un-protected. To regard to the conservation of wood artifacts, protective treatments for wood will preserve the material from environmental agents and biological attack. Hence, potential advantages of hybrid (organic–inorganic) nano-composite coatings for stone/wood have been found to be: Enhanced mechanical properties in comparison to the pure polymeric matrix, due to the reinforcing effect of the nano-filler; superior barrier properties (the presence of the nano-filler hinders the ingress of water and/or potentially harmful chemicals); optical clarity and transparency. It has been found that the efficacy of a nano-filled coating strongly depends on the effectiveness of the method used to uniformly disperse the nano-filler in the polymeric matrix. Furthermore, the presence of nano-particles should not impair the viscosity of the organic matrix, in order to employ the conventional techniques of application for coatings

Influence of the Distribution of a Spray Paint on the Efficacy of Anti-Graffiti Coatings on a Highly Porous Natural Stone Material

Graffiti on facades often has a heavy impact in social and economic terms, particularly when historical and artistic artefacts are affected. To limit the damages to the surfaces, preventive plans are implemented and anti-graffiti coatings are used as a protective measure. In this study, the distribution of a spray paint inside a highly porous stone, with and without anti-graffiti protection, was investigated. Two commercial sacrificial anti-graffiti systems were used and an acrylic-based paint was applied as staining agent. Environmental scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) microanalysis were performed to characterise, from the morphological and chemical point of view, the anti-graffiti coatings and the paint. Maps of the main elements were acquired to locate the different products inside the stone. Chemical removers were used to clean the stained surfaces, then the effectiveness of the cleaning was assessed by visual observations and colour measurements, as well as on the basis of percentage of residual stain. The obtained results highlighted that the anti-graffiti efficacy strongly depended on the characteristics of the applied coating. This latter usually acted as a barrier, but good results were obtained only where the stain did not remain as a separate layer, but penetrated the protective coating. Microcracks in the anti-graffiti coating were able to nullify the protective action