Design and optimization of new nanomaterials for the conservation of cultural heritage
- Autores: Aránzazu Sierra Fernández
- Directores de la Tesis: Luz Stella Gómez Villalba (dir. tes.), Rafael Fort González (codir. tes.), María Eugenia Rabanal Jiménez (codir. tes.)
- Lectura: En la Universidad Carlos III de Madrid ( España ) en 2017
- Idioma: inglés
- Tribunal Calificador de la Tesis: Mauro Francesco, La Russa (presid.), María Asunción de los Ríos Murillo (secret.), Dušan K Božanić (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia e Ingeniería de Materiales por la Universidad Carlos III de Madrid
- Materias:
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- Resumen
The degradation of the stone cultural heritage represents an irreversible loss; an issue that has become urgent since the increase of natural decay caused by climate change, the impact of atmospheric pollution and/or the current use of inappropriate treatments against stone weathering. Among different degradation processes, the loss of stone cohesion and the biodeterioration produced due to the biological colonization of stone heritage, are two of the most common issues that affect stone substrates.
The present research work uses the application of nanotechnology to develop innovative strategies for improving these specific issues of crucial importance for the stone preservation. In this way, the research work consists of three main contributions:
Firstly, the design, optimization and development of new nanomaterials based on brucite (Mg(OH)2) and portlandite (Ca(OH)2) nanoparticles (NPs) for the consolidation of carbonatic stones were treated. Pure Mg(OH)2, Ca(OH)2, and mixed formulations of Mg(OH)2 and Ca(OH)2 NPs were synthesized by hydrothermal method and sol-gel method. The changes in experimental parameters such as synthesis temperature, time reaction and/or precursor reactivity can determine the viability of a particular synthesis design. This is why firstly; studies of the optimal synthesis method and the influence of experimental parameters on the physico-chemical properties of the nanomaterials were carried out. After this, the application of these nanoparticles on carbonatic stones (dolostone, a sedimentary rock that contains high percentage of calcium and magnesium carbonate), widely used in the cultural heritage of Spain, was investigated. The selection of the type of nanoparticles according to the petrophysical properties and chemical composition of the stone substrate was achieved. In this sense, the designed inorganic nanomaterials based on brucite and portlandite NPs constituted stable products with enhanced chemical-physical affinities for natural stone.
In the second part, the combination of the strong antimicrobial activity of ZnO, with the safe-to-use antimicrobial effectiveness and good compatibility of MgO with dolostone was taken as the starting point to develop new antifungal coatings highly compatible with the built-stone heritage. Thus, the photocatalytic and antifungal properties of Zn-doped MgO (Mg1-xZnxO) NPs obtained by sol-gel method, and their application as antifungal coatings for stone cultural heritage have been explored. The photocatalytic activity of the Zn-doped MgO NPs was comparatively studied with pure MgO and ZnO NPs. The antifungal activity was assessed against representative fungal species (Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans), which are especially active in the deterioration of stone heritage. The results showed that the development of a high surface defects content detected in the Zn-doped MgO nanoparticles changed its surface morphology, structural properties and defect density producing thus increased photocatalytic and antifungal effectiveness in comparison with pristine MgO and ZnO nanoparticles. The development of Zn doped MgO nanoparticles by sol-gel synthesis method, with promising multifunctional photocatalytic and antifungal properties for carbonatic stone heritage was achieved.
Finally, an additional research field was explored in the present research work with the use of different strategies to modify the cellulose surfaces and improve the interaction of adjacent fibers. The main results showed that Mg(OH)2 nanoparticles synthesized via hydrothermal method were successfully deposited onto pine cellulose fibers with different refining degrees and chemical compositions. These findings also showed for the first time that the physical and mechanical properties of the pine pulp fibers can be modified by the joint action of the presence of residual lignin and heteropolysaccharides in the pulp, the low consistency refining process and the application of brucite nanoparticles.
