During the last years, there has been an even increasing interest for natural derived materials and for the study of the biophysical processes involved in their formation. In fact, despite the possibility to fabricate home-made materials in reproducible way to meet specific performance demands, the complexity of biological systems suggested to consider nature as an inspiration for the design and synthesis of new types of materials. In this context, marine biomaterials are a area of research with significant applications. In fact, the marine environment represents a unique resource of natural inorganic and organic materials with peculiar properties such as chemical and structural complexity, multifunctionality and miniaturization that are not possible to obtain in the laboratory. Therefore, the isolation, characterization and processability of marine materials are crucial aspects for the development of the marine biotechnologies industry. The aim of this study was to to isolate and synthesize naturally-derived materials from marine organisms for biomedical use and namely for tissue engineering applications. The study has been divided into two main parts. The first part concerned the isolation and characterization of an important natural biopolymer: collagen. In particular, Acid-solubilized collagen (ASC) and pepsin-solubilized collagen (PSC) were isolated from Loligo Vulgaris squid mantle and comparatively characterized. In the second part of the work a novel method to process cuttlefish bone powders for the production of highly bioactive ceramics formulations has been developed.

Tubular SOFCs were produced by extrusion of the supporting anode composed by GDC10 and Cu oxides. A 10 μm thin GDC10 electrolytic layer and the LSF20:GDC10 cathode were deposited by dip-coating and the complete cell was co-sintered in one step. Thanks to the optimization of the composition and the employment of Li2O as sintering aid, the densification of the electrolyte was accomplished more than 500°C below the sintering temperature of GDC10. The cell had a maximum OCV of 0.54 V and the highest measured power density was 8.98 mW cm-2 with a peak power density projected to be 27.5 mW cm-2.

In the past few years, significant progress in the study of scaffolds for cells grow has taken place. This research has led to the development of a wide variety of metallic, polymeric, ceramic and composite biomaterials. This thesis describes the development of a novel composite system with tunable morphological and mechanical properties, ease of production and capability to guide the biological response. The composite system was composed by polyamide 6 (PA6) and carboxyl-functionalized multi-walled carbon nanotubes (MWCNT), which were used as reinforcement agents in the polymer matrix. Electrospinning was used as the fabrication technique for the production of anisotropic networks. Physical and biological properties of the nets were evaluated focusing on the effect of the filler addition. It was observed that the production technique induced the alignment of MWCNT within the nanofiber axis and the formation of a roughness on the fiber's surface. The biological properties of MG63 and MRC5 cell lines were enhanced if compared with the neat PA6 networks due to surface modification caused by the filler addition.

In the field of Tissue Engineering, a new concept has been developed in the last few years. The formation of new tissue induced by a tissue engineered system needs to be accompanied by the achievement of a complete tissue functionality and scaffold properties have to be designed following the principles of biomimetics, i.e. the complexity of the physiological environment has to be translated and reproduced in the cell-scaffold construct. This approach is especially challenging when the interface between two tissues has to be restored. In this case, the scaffold has not only to sustain the regeneration of two different tissues, but also to ensure the regeneration of a functional interfacial zone between them. Therefore, scaffold properties must reflect the complexity of tissue boundary structures, in terms of controlled gradients in morphological, chemical and mechanical properties. The aim of this research work was the application of these advanced principles to the regeneration of the osteochondral defect, which is a degenerative pathology involving both cartilage and bone tissue, whose current treatments are uneffective in the long term. In this work, a multiphasic scaffold for osteochondral Tissue Engineering was produced and characterized. Silk fibroin-based 3D sponges were employed for the chondral and subchondral components for cartilage and bone regeneration, respectively, to exploit the biocompatibility and versatility of silk fibroin in Tissue Engineering applications. For the restoration of a functional interface, a nanometric net was used to separate the two components, in order to allow a dialogue among cells between the two phases thanks to a physiological solute flow, while preventing cell migration towards the chondral site, especially of blood cells which may cause mineralization of the non-calcified cartilage. For the chondral component, two different strategies were explored. First, pure silk fibroin sponges produced by salt leaching were combined to static or dynamic culture conditions to evaluate the chondrogenic potential of adipose- derived stem cells (ASCs). These cells have indeed many advantages for cartilage Tissue Engineering applications, such as abundance, easy accessibility, ability of self-renewal and stability during in vitro culture. The best differentiation of ASCs towards chondrocytes was achieved after 28 days of culture in a static environment and chondrogenic media, in terms of higher chondrogenic gene expression, new cartilage extracellular matrix deposition and increase of compressive mechanical properties. ASC/scaffold constructs were then implanted in vivo in a rat xiphoid critical size defect for 8 weeks and also in this case, the best outcomes in terms of new tissue volume and quality were obtained when static conditions and chondrogenic medium were employed during pre-culture. The aim of the second strategy presented in this work was to modify silk fibroin (SF) sponges with the addition of hyaluronic acid (HA). Besides hyaluronic acid is a natural component of cartilage and contributes to its biomechanics thanks to its ability to retain a remarkable amount of water, it has been shown to modulate chondrocyte phenotype when employed in scaf- folds for cartilage regeneration. Therefore, we exploited its properties producing silk fibroin/hyaluronic acid scaffolds by salt leaching at different HA concentrations, eventually cross-linked by genipin to improve HA retention. SF/HA sponges were completely characterized in terms of physical, chemical and mechanical properties and then used to culture primary chondrocytes in vitro. Results demonstrated that the scaffolds with the highest amount of hyaluronic acid both with and without cross-linking elicited better responses in cartilage cells with respect to pure silk fibroin sponges, in terms of chondrogenic phenotype enhancement and new cartilage extracellular matrix deposition. The nanometric net of the multicomponent scaffold for osteochondral regeneration was produced by electrospinning of poly-d,l-lactid acid/polyethylene glycol (PdlLA/PEG) blends. PdlLA was employed since it is a well-known biocompatible polymer and it is easy to process with this technique, while PEG was added to avoid fiber shrinkage in an aqueous environment. Nets were characterized in terms of morphology and thermal properties, then assembled to a silk fibroin sponge without any modification to their geometry. To preliminarily evaluate the biological properties of PdlLA/PEG electrospun nets, a system to co-culture chondrocytes on scaffolds with net and osteoblasts was designed and validated, so that the biochemical communications between cells could take place through the net fibers. In the future, this system will be employed to evaluate how osteoblasts can improve chondrocyte response in terms of phenotype maintenance and new cartilage tissue deposition. The results reported in this research work will be the basis for the final design of a multicomponent scaffold which comprises the best outcomes obtained. Hence, SF/HA scaffolds which elicited the best responses on chondrocytes will be used in combination with ASCs, in order to verify their potential to sus- tain chondrogenesis in vitro. Then, they will be assembled to the nanometric net and, before moving to an appropriate in vivo study, the co-culture system will be employed to assess how the cellular dialogue with osteoblasts can have beneficial effects on the chondrogenic differentiation of adipose-derived stem cells.

The present thesis work focuses on the stability of intermediate temperature SOFC technologies and it is divided in two parts: (i)cathode stability in anode-supported cells and (ii)fabrication and operation of tubular metal supported SOFCs. In the first part, the stability of ferritic perovskite cathodes currently implemented at IK4-Ikerlan and SOFCpower (LSF-SDC and LSCF-GDC, respectively) was studied in a specific experimental DoE design. The influence of cathode processing and operation conditions together with intrinsic degradation mechanisms and extrinsic ones related to chromium poisoning and air humidification were analyzed in detail. Moreover, the effectiveness of two interconnect coating materials, MCO spinel and novel LNC perovskite against chromium poisoning of the cathode was studied. With this commitment, anode-supported half-cells manufactured by SOFCpower were used making profit of the verified high reproducibility of these cells. In parallel, work at IK4-Ikerlan in tubular MSC technology demonstrated critical instability related to the operation under high fuel utilization and deficient diffusion barrier layer (DBL) implementation. This allowed element interdiffusion during the manufacturing process between the metal support and the anode. In the second part of this thesis work, a second generation (G2) of tubular MSCs based on an innovative DBL has been developed in all aspects. This includes processing parameters optimization and stability studies. During this work, an intrinsic variable degradation mechanism related to the DBL and manufacturing process of MSC turned out to be critical in G2 cells stability during operation. At this point, understanding such a mechanism and determining its origin became the most fascinating challenge of my investigation. Overall, this thesis work focuses in the study of critical parameters in SOFCs stability. Factors affecting the stability of cell components over a wide range of operation conditions and degradation mechanisms related to the manufacturing process and operation are considered in detail.

Structural defects play a major role in nanotechnology as they influence most properties, thus largely motivating the special interest in studying materials at the nano scale. The present Thesis work contributes to this broad and diversified research field with emphasis on the characterization of nanocrystalline ceramic materials and their lattice defects. In particular, main efforts were addressed to develop new and more comprehensive approaches to the study of nanocrystalline powders, combining different techniques for a better and deeper understanding of materials. The specific applications selected in this work are basically two: nanocrystalline fluorite as a promising ionic conductor and nanocrystalline magnesium hydride for hydrogen storage applications. Chapters II and III were dedicated to investigate nanocrystalline fluorite produced by two different methods: a bottom-up approach based on co-precipitation of Ca and F precursors yielding loosely bound nanocrystals, and a popular top-down approach, high energy ball milling, giving nanocrystals of comparable sizes but strongly agglomerated and densely populated with dislocations. As a major achievement reported in this part of the Thesis work, a new approach was proposed and tested for the simultaneous modelling of X-ray Diffraction (XRD) peak profiles and solid state NMR spin-lattice relaxation data. With the valuable support of Transmission Electron Microscopy (TEM), this work offers a new understanding of the complex defect structure of nanocrystalline fluorite, and is also a demonstration of the power of combining different techniques in a consistent way. One of the most debated aspects of nanotechnology concerns the stability of the nanostructure, and the mechanisms of defect annealing and grain growth with temperature. This topic was the object of chapter V, dedicated to study the influence of lattice defects on the grain growth kinetics of nanocrystalline fluorite. This chapter was preceded by chapter IV, on the furnace recently installed at the MCX beamline for in-situ high temperature fast data collection; besides providing useful details for the in-situ study on nanocrystalline fluorite shown in the following chapter, the activity reported in chapter IV is a tangible sign of the special involvement during the Thesis work in supporting standard operation as well as development of the ELETTRA beamline MCX. The growth kinetics was studied on two samples, among those discussed in Chapter III, with comparable crystalline domain size but drastically different lattice defect content, so to highlight the role lattice defects – dislocations in this case – in the growth process. 14 Last two chapters (chapter VI and VII) were dedicated to nanocrystalline magnesium hydride, and how the performance, in particular the hydrogen desorption kinetics, can be improved by adding a nanocrystalline tin oxide. Besides general aspects on phase composition of the system and hydrogen storage capability, the work also addressed the problem of obtaining activation energy values in the thermal decomposition of magnesium hydride powders, presenting an interesting review of results given by the most known and well-assessed TG-MS coupled measurements, with details on the use of different equations of the literature on thermal analysis. Although research work can rarely be considered as finished, a sound conclusion of this Thesis work is toward the use of different characterization techniques, also within the same data analysis procedure, to support a better, and more reliable investigation of nanomaterial properties.

In the last decade, neutron detection has been attracting the attention of the scientific community for different reasons. On one side, the increase in the price of 3He, employed in the most efficient and the most widely used neutron detectors. On the other side, the harmfulness of traditional xylene based liquid scintillators, used in extremely large volumes for the detection of fast neutrons. Finally, the demand for most compact and rough systems pushed by the increased popularity of neutron imaging, neutron scattering and neutron diffraction techniques. Polysiloxanes could help addressing some of the existing issues regarding neutron detection thanks to their unique properties. For this reason, in this work, polysiloxane scintillators have been developed and characterized, with a special attention to their optical properties and their time response. In particular, this thesis describes the investigation of the scintillation performances of several different polysiloxane liquids. The results have been connected with the optical properties of the material, in turns linked to its molecular structure, allowing to select the most suitable polysiloxane solvent for liquid scintillators. The timing properties of scintillating mixtures employing the best performing polysiloxane solvent were consequently analyzed as a function of the primary dye concentration, with a special focus to the pulse shape discrimination (PSD) capability of the material. PSD is indeed one of the most important characteristic of liquid scintillators, and one of the factors determining their large use. Beside polysiloxane liquids, time response of polysiloxane plastic scintillators was also investigated with the aim of studying their PSD capability. At the moment, indeed, only few examples of plastic scintillators capable of PSD exist, and also in those cases some criticalities emerged connected with stability issues and efficiency. Production of red emitting polysiloxane plastic scintillators is also described in this work, analyzing the energy transfer process between dyes in order to optimize the readout with an avalanche photodiode. This would allow overcoming some issues connected with the use of photomultiplier tubes, in more compact and rugged systems. Finally some preliminary results about the HYDE experiment are presented. This project aims at the development of a hybrid detector for neutrons, combining a 3D silicon diode with a suitable neutron converter, in order to produce a compact efficient neutron detector with good spatial resolution. With this goal different types of converters for fast and thermal neutrons were tested and the performances of 3D and planar devices were compared.

The PhD project was details on the polyolefin nanocomposites compounding, processing and preparation. Two different types of polymer matrix with low melt flow rate for fiber forming polymers have been selected; high density polyethylene (HDPE) and isotactic polypropylene (PP). High density polyethylene was compounded with double layered hydrotalcite (LDH) while in case of polypropylene reinforcement by adding fumed silica and kaolinite was performed. In this way the influence of the nanofiller type on the thermo-mechanical properties of the prepared nanocomposites were studied. In recent years several research efforts have been focused on the preparation of polymer/layered inorganic nanocomposites because of the excellent properties in comparison to the neat polymer. The main reason of this interest lies certainly in the properties of the nanoclay, like high stiffness, and high aspect ratio, that induce enhancement of various polymer properties (thermal stability, mechanical properties, flame resistance and gas barrier) even with small amount of filler. Moreover, nanocomposites can be processed more easily than microcomposite. Recently literature evidences a lot of progress in the nanofilled bulk materials; on the other hand, there are relatively a few publications on fibers made of nanofilled polyolefins. For instance, PP fibers were produced with various types of nanofillers, e.g. layered silicates, carbon nanotubes and montmorillonite. In the case of HDPE, composite fibers containing calcium carbonate, carbon nanotubes, silica and layered silicates were reported. It is worth to mention that so far, no publication could be found on this work using the same nanofillers with the same matrix. This thesis is divided into six chapters; Introduction and Background, Experimental activities, after obtained Results with discussions are reported and finally Conclusions. In the Introduction and Background (Chapter I and II) general information about nanocomposites and characteristic of different nanofillers type were summarized. After that polymer processing method with particular attention on the melt extrusion and fiber spinning were described. Third Chapter is dedicated to the experimental part. Here, the used material characterization, nanocomposite preparation procedure and description of experimental techniques were reported. All nanocomposites were characterized by different experimental techniques. First nanofiller morphology by microscope (SEM and TEM) and X-ray diffraction technique was tested. Thermal stability was investigated by Thermal Gravimetric Analysis (TGA) and crystallization behavior by Differential Scanning Calorimetry (DSC). Finally mechanical properties were characterized by tensile test, Dynamical Mechanical Thermal Analysis (DMTA) and creep test. The Results and Discussion have been divided into two parts; first one was dedicated to the high density polyethylene layered double hydrotalcite nanocomposites (HDPE-LDH), while in the second polypropylene with fumed silica (PP-FS) and kaolinite (PP-K) nanocomposite were described. i. High density polyethylene hydrotalcite (HDPE-LDH) nanocomposites after different process of plates and fibers production will be compared in Chapter IV. At the beginning a polypropylene matrix, suitable for fiber production, was firstly melt compounded with organically modified hydrotalcite up to 5% by wt. Similar compositions with up to 3% wt. of LDH were performed by melt spinning. The incorporation of the clay into both bulk and fiber nanocomposite enhanced the thermal stability and induced heterogeneous nucleation of HDPE. Hydrotalcite positively affected the mechanical properties in term of higher Young’s modulus and tensile strength. After the preliminary characterization on bulk and as-spun material the fibers were hot drawn up to draw ratio (DR) 20. XRD analysis revealed intercalation with high degree of exfoliation for the composites with 1-2% wt. of LDH. For this compositions higher elastic modulus 9.0 GPa - 9.3 GPa (with respect to 8.0 GPa of the neat HDPE), and maintain tensile strength and deformation at break were observed. Moreover, the addition of low amount of LDH significantly improved the creep stability. ii. Nanocomposites of isotactic polypropylene fumed silica (PP-FS) were described in the Chapter V. Two types of hydrophobic fumed silica with different surface area (170m2•g-1 and 150m2•g-1) and surface treatment (treated respectively by dimethyldichlorosilane and octylsilane) up to 2% vol. were used. Similar as in case of HDPE-LDH nanocomposites plates production and characterization was a preliminary step to select the best compositions for the fiber preparation. After that, the work has been focused on the iPP-FS fiber production. Introduction of the nanofiller enhanced thermal stability and mechanical properties of the nanocomposite. Elastic modulus at draw ratio 10 increased from 5.3 GPa for neat iPP up to 7.5 – 8.6 GPa for compositions with 0.25 – 0.5% vol. Together with this improvement enhancement in strength at break and maintaining deformation at break were observed. Moreover, isothermal creep tests evidenced improvement in the creep stability due to the FS introduction, over the whole range of investigated draw ratios. iii. The last results of recent research dedicated to the polypropylene kaolinite (PP-K) nanocomposites are reported in Appendix 1. Nanocomposite fibers were successfully spun up to draw ratio (DR) 15 at very high nanofiller content up to 30% wt. The presence of kaolinite not only increased the thermal stability but also enhanced elastic modulus up to 5.6 GPa – 7.0 GPa for compositions with 1% up to 30% wt. of kaolinite, in comparison to 5.4 GPa for neat PP at draw ratio 10. Moreover, for the composition with 10% wt. of kaolinite better drawability with maximum modulus was obtained in comparison to neat PP. Finally the most important observation made on polyolefin nanocomposites fibers were summarized in the Chapter VI. It can be concluded that polyolefin fibers nanocomposites were successfully prepared by two different processing conditions: melt compounding and melt spinning followed by hot drawing. In case of plates the introduction of nanosilica remarkably improved the thermal stability and elastic modulus, with retention of the pristine tensile properties at break. Nanocomposites fibers showed a higher improvement of the elastic modulus with respect to the nanocomposites plates containing the same percentage of nanofiller. Moreover, the introduction of the nanofiller enhanced tensile dynamic mechanical properties especially for higher draw ratio. Similar behavior was also observed in case of creep compliance. Higher creep stability was observed for the drawn fibers with nanofiller in comparison to neat polymer. This behavior could be a consequence of the different orientation and morphology related to the crystallinity developed in the spinning. These results confirmed that polyolefin containing nanofiller could be easily spun into nanofilled fiber. TEM images revealed how the experienced improvements of the mechanical properties could be probably related to the orientation of nanofiller aggregates along the strain direction and to the consequent increase of the filler-matrix interfacial area.

Polycrystalline thin films and coatings often show preferred orientation of grains and crystalline domains, and develop a residual stress state as an effect of the growth mechanisms. These features can be conveniently measured by means of non-contact and non-destructive X-ray diffraction. As the technique only measures a map of strains along selected directions, stress evaluation requires a suitable constitutive equation, where the expression of moduli can be far from trivial if texture effects are to be taken into account; additionally, a grain interaction model needs to be enforced to describe strain and stress distribution among grains in the aggregate, based on background assumptions. Several grain interaction models are available from literature: usually, a model or a combination of them provides a good fit of experimental data; often however underlying hypotheses are too restrictive or require unavailable information on certain microstructural parameters, leading this approach to fail. For this reason an experimental method was developed, for the characterisation of elastic properties and residual stress in thin film components by means of X-ray diffraction during in-situ mechanical testing. This thesis presents a review of major literature works describing grain interaction modelling in textured components, and their implementation in X-ray diffraction stress analysis procedures. Following, the method for experimental characterisation of thin film elastic properties is described in detail. Applications are presented in the final chapter, that illustrates selected case studies on electrodeposited coatings.

Research in materials science field is often driven by the necessity to overcome problems in fast, reliable and possibly cost effective ways. Many times the starting point to find a solution is a literature survey, to understand if someone already encountered a similar problem and proposed an answer, or if some authors developed a material that can be used to solve the issue. The work performed within this thesis however fits in another type of approach, i.e. research for the research's sake. In this kind of approach the efforts are not dedicated directly to solve a given, precise and detailed problem, but to invent and develop new types of materials, characterizing them so that other researchers can take benefits from both the synthetic way and the measured properties of the new material produced. In particular, this PhD thesis deals with the combination of two "exotic" class of materials, which are aerogels and polymer derived ceramics. Aerogel is actually a shape, more than a material, from the proper chemical point of view. This kind of shape, anyway, is so peculiar that many of the properties are common to all the aerogels' products, similarly to what happen for other class of materials like conductivity for metals, hardness for ceramics and high specific strength for polymers. These common properties are: low density, high specific surface and predominantly mesoporous microstructure. Polymer derived ceramic (PDC) denotes a family of ceramic materials that can be obtained by a controlled thermolysis of a polymeric precursor. These polymers are usually Si based and contain functional groups that allow to control the final chemistry of the ceramic produced, along with the great advantage that the shape can be set already in the polymeric state. Successfully combining the two techniques, i.e. to produce polymer derived ceramic aerogel, is the core of this thesis. Preference was given to the use of commercially available pre-ceramic polymers so ceramic aerogels belonging to the SiOCN system were produced, starting from polycarbosilane (SMP-10), polysilazane (PSZ-20) and polysiloxane (PMHS). A reliable procedure was set up to produce aerogels with different composition and microstructure, leading to a wide range of properties in terms of density, specific surface, high temperature stability, electrochemical functionality etc., as will be better depicted through the thesis. Additionally, some application of the materials produced were tested, in which the aerogel shape, combined with the proper chemistry, was expected to give interesting results.