Advances in Nanostructured Materials for Multifunctional Applications: Synthesis, Characterization and Properties

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Authors: Silvia Germinario, Federica Fernandez, Giovanni Baldi, Valentina Dami, Andrea Cioni
Abstract: Nowadays the use of multifunctional nanomaterials has significantly increased with interesting applications for the cultural heritage conservation sector, leading to the definition and use of products with innovative properties. Therefore, a preliminary validation of the performances and behavior over time of these treatments becomes an unavoidable key point for a correct use of these products before being applied to historical materials, in order to avoid irreparable damage over time. In this direction, the aim of this study was to evaluate the effectiveness of the treatment with multifunctional nanostructured products on Apuan marble. The focus of the work was to test methods to accelerate aging, in order to simulate different environmental agents of degradation to which marble in historical buildings can be exposed. Stone samples were examined after exposition to high temperature cycles in a muffle furnace, treatments in saline solution, cycles of thermal shock and aging by SO2 action in presence of humidity. After each artificial aging cycle, changes in appearance were noted and chemical-physical properties were measured in order to compare differences between fresh and treated samples. The protective qualities of the coatings were evaluated using the following tests: contact angle; photocatalytic properties by methylene blue degradation tests; photodegradation kinetics of pollutants under UVA irradiation. Before and after the treatments, scanning electron microscopy equipped by microanalysis detector (SEM-EDS) was also used to evaluate changes in the surface morphology of the samples. The results showed effects of degradation in the rock samples due to aging after each test and all the products applied to the sample surface seemed to be very efficient in relation to their functions.
Authors: Eirini Chrysanthi Tsardaka, Eleni Pavlidou, Maria Stefanidou
Abstract: The present research study is an effort to evaluate the effect of different nanoparticles in lime-pozzolan system, in time. nanosilica, nanoalumina and nanocalcium oxide were used in different combinations in this traditional binding system. The paper aims to record the durability of the traditional binding system in time, up to 365 days. For that purpose, the samples were subjected to ageing tests, such as wetting-drying cycles, sea water cycles and salt cycles. Up to 90 days, nanosilica benefits the most of the physic-mechanical properties, as well as the microstructure. Though, by studying the systems in time, the behavior of the other nanoparticles seems to favor certain properties more than nanosilica, especially at later ages. The addition of nanocalcium oxide combined with nanoalumina aids the improvement of the microstructure and the system presented great compressive after 40 cycles in ageing tests.
Authors: Evangelia Tsampali, Eirini Chrysanthi Tsardaka, Eleni Pavlidou, Konstantinos M. Paraskevopoulos, Maria Stefanidou
Abstract: This paper presents the effect of adding nanoparticles SiO2 and Al2O3 in the cement with respect to mechanical, physical and structural properties. Nanoparticles were chosen for the development of nanocomposite building materials with high mechanical strength, durability and low permeability. Correspondingly, the cement used is Portland Cement CEMI42.5N. Five compositions have been prepared, a reference sample (OPC) and pastes with different nanoparticles. Nanoparticles of SiO2 and Al2O3 were added in 1.5% and 3% by weight of cement and the produced samples were tested after 7, 28, 90 and 120 days of curing. All the samples, in every hydration period, were tested for compressive strength, while their open porosity was measured and their microstructure was examined by means of infrared spectroscopy. Furthermore, for certain hydration periods, the chemical and elemental composition of the samples was evaluated by means of X-ray diffraction and scanning electron microscopy. The samples were also evaluated for capillary water absorption and shrinkage, while thermal analysis was performed for specific samples. The comprehensive analysis revealed a positive effect, in terms of structural properties, of nanoparticle admixture in cementitious systems. The addition of nanoparticles influence the workability of the composites and contributes to the formation of crystallization nuclei, which in turn enhance the durability of the material. Interestingly, it was found that high concentration of nanoAl2O3 in the admixure, results in high mechanical properties. Highlights: Different analytical techniques were combined in order to holistically test nanomodified cement pastes. nanoalumina is systematically tested as additive in cement pastes.
Authors: Aspasia Karozou, Eleni Pavlidou, Maria Stefanidou
Abstract: Earthen materials have been used in construction for centuries. Nowadays, a certain appeal towards natural materials rose again due to the various benefits they hold. Besides being inexpensive and approachable, earthen construction offers a clear sustainable method of modern manufacturing. Since earthen materials present high absorption and relatively low compressive strength, the main purpose of this study was to enhance these abilities of clay-based mortars using nanoadditives. To achieve the mechanical and physical invigoration of the clay matrix two different compositions were fabricated by the use of nanoclay, nanosilica and nanoalumina. The addition of nanoclay (NC) at 5%w/w of binder, indicated a lower water absorption and an increase in mechanical properties, while the use of nanosilica and nanoalumina combined at 1.5% and 1% w/w of binder respectively, outline a less stable and compact structure.

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