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BIO-inspired NAcre-like materials FOR the next generation of conservation treatments in stone ART works

Periodic Reporting for period 2 - BIONA4ART (BIO-inspired NAcre-like materials FOR the next generation of conservation treatments in stone ART works)

Período documentado: 2021-07-01 hasta 2022-06-30

Cultural heritage is an incalculable and essential legacy for our future. Its loss would have catastrophic effects for both culture (identity loss) and the economy (considering cultural heritage-related tourism and activities). As a result, the need to conserve and give access to it has become a critical challenge for society. Stone is used in some of the most well-known pieces of our cultural heritage. This stone legacy is constantly subjected to weathering processes as a result of its connection with the environment, an issue that has become critical as natural decay has increased as a result of climate change and the impact of atmospheric pollution. The inherent dilemma with this conservation problem is that no long-term treatments for stone preservation in aggressive environments are now accessible. As a result, there is a rising priority connected with the development of innovative conservation-restoration treatments capable of overcoming the constraints of existing treatments in terms of efficacy, compatibility, and/or durability. The purpose of this MSCA fellowship was to design and develop a novel multilayered coating for the protection of stone heritage inspired by the unique structure of mother-of-pearl (nacre), which provides exceptional mechanical qualities with high fracture toughness to shells. The general goal was to develop and test a sequential layer-by-layer deposition of continuous mineralized layers and a quick assembly between them, with the goal of creating a unique combination of low density, strength, and exceptional resistance to fracture in stone materials.
Overall, the BIONA4ART project achieved its overall goal and particular objectives, which included the creation of a unique nacre-like organic-inorganic multilayered coating for stone heritage preservation. An extensive characterization of the organic substrate's role in templating the structure of mineralized layers, as well as the use of soluble additives (including small inorganic ions and large organic molecules such as proteins and polymers), has been carried out in order to obtain structural control of the layers, including their orientation, morphology, and hierarchical structure. Furthermore, the use of these nacre-like coatings as a novel surface treatment has been investigated on different stone substrates (marble and limestone) with varying porosity and mineralogical composition. The mechanical properties of the coatings, as well as the topological structures, local physical properties, and processes occurring at mineral surfaces, were investigated using advanced scanning force microscopy (SFM) methods. This approach resulted in a better understanding of the structures, local physical properties, and processes that occur at the mineral surfaces of the coating, as well as their relationship with the obtained mechanical properties. By adjusting the hierarchical architecture from the nanoscale to the microscale level while taking into account the characteristics of the material to be protected, the mechanical performance of the nacre-like coating was modulated. This had a direct effect on the effectiveness of the developed coatings in terms of their durability as protective coatings for stone materials. It is envisaged that the replication of biomineralization in natural systems by using polycarboxylate-induced calcite mineralization can provide long-term protection for stone materials used in cultural heritage.

In addition to research, the fellow participated in a number of carefully selected and focused training programs directed at boosting her expertise and giving new and transferrable skills. Several dissemination, communication, and exploitation actions were carried out to maximize the effect of the BIONA4ART project.
BIONA4ART advances beyond the state of the art by creating optimal nacre-like multilayered coatings with adjustable composition, structure, characteristics, and tunable wettability for stone material protection. A multilayer hybrid coating with a composition very close to nacre can be created by adjusting the reaction conditions, particularly the presence of polycarboxylates. Furthermore, the level of control over mineralization site locations can be exploited to generate more complicated patterns in hybrid layers. As a result, the knowledge gathered in this research effort will have a significant impact on the development of new multi-layered nacre-like coatings with highly targeted final qualities. This bio-inspired mineralization strategy is also interesting for a wide range of materials that could be used in fields other than cultural heritage, such as environmental technologies, biomedical engineering, and the building industries.

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