The atomic mean square displacement (MSD,  ̄(σ_i^2 ) ) is often used in computational materials science studies to calculate measurable properties from the atomic trajectories of simulations; for example, the diffusion coefficient, which according to Einstein relations (Einstein 1905) on the random walk is 1/6 of the slope of the trend of  ̄(σ_i^2 ) vs. time (Chandler 1987). Equally relevant is the mean square relative displacement (MSRD,  ̄(σ_ij^2 )), used in X-ray Spectroscopies, mainly EXAFS, to describe the atomic disorder in solids (Calvin 2013) (Fornasini 2014). Less known is the relevance of the MSRD in X-ray scattering from nanoparticles. In particular, in Total Scattering methods (Pair Distribution Function and Debye Scattering Equation), which rely on an atomistic description of the nanoparticles, the MSRD is the key to distinguish dynamic (thermal) and static disorder (Krivoglaz 1969) (Kuhs 2006). Interestingly, the trend of the MRSD with the distance is characteristic of the nanoparticle shape, an aspect investigated in some detail in this Thesis work. More generally it can be shown that beyond the expected effect of nanocrystal size, the shape alters the contribution of the surface, which is quite relevant for the MSRD. The importance of the shape and of the surface region holds also in case of clusters of nanoparticles, not only in isolated particles. Besides the MSRD, the atomic configurations simulated by molecular dynamics (MD) can also be used to calculate the so-called Warren plot (or diagram), originally introduced in the seminal work of Warren & Averbach of the †̃50s to describe the effects of plastic deformation in metals (Warren B.E. 1950). Recent work has shown how to obtain Warren plots from the analysis of the diffraction line profiles according to the Whole Powder Pattern Modelling (WPPM) (L. M. Scardi P. 2002) (Scardi P 2017) (P. E.-W. Scardi 2018), in particular from the analysis of the strain component of the diffraction peak profile broadening. As proposed in this work, If the Warren plot can be calculated directly from MD simulations, then it is possible to proceed backwards, and construct more reliable strain functions from an atomistic knowledge of the local atomic displacement caused by static and dynamic disorder components. This thesis is divided in two main parts, discussing two different but complementary topics: atomistic modelling and calculations of displacement quantities, application of the above results to experimental case studies, based on the modelling of diffraction data from nanocrystalline systems. We start by describing the atomistic simulations and vibrational properties calculated for several atomic configurations. The main case study concerns Palladium nanoparticles of different sizes and shapes, for which we show that vibrational properties and correlation properties between atoms pairs are greatly influenced by the geometric shape of the nanoparticle and to a lesser extent by their size. The interest is on truncated cubes, i.e. cubes whose edges and corners are progressively removed, as in the series of so-called Wulff solids, ranging from the cubic to the octahedral shape (Wulff G. 1901). As shown in (ii), these are the object of several experimental studies. The developed methodologies are nevertheless applicable to other cases, like the clusters of nanocrystals observed in powders produced by high-energy ball milling, which is also a topic discussed in (ii). The work aims to show a general approach to atomistic modelling, both for isolated nanoparticles with definite shapes, and grains of unspecified shape in plastically deformed polycrystalline materials. We then use the values for displacement quantities (e.g., MSD, MSRD) calculated for the simulated systems to compare them to the experimental results. An underlying fact that seems to hold in all the different cases is that the surface behaviour of nanomaterials has the largest influence on the displacement quantities. For isolated particles we observe strong correlation between displacement quantities and the shape; whereas in the case of a nanocrystalline grain clusters (Figure 1 1) we see that no matter the defects inside the grain, the main contribution to MSRD is given by the grain boundary.

Tissue engineering (TE) is an interdisciplinary field, in continuous evolution, that possesses as main goal the creation of efficient systems for tissues and organs healing and regeneration. For bone, TE strategies are typically based on the combined use of scaffolds, cells, and bioactive molecules. Different materials were successfully studied and proposed for the fabrication of scaffolds. Among them, silk fibroin (SF) was evaluated as particularly promising for different TE applications, especially for bone tissue regeneration. Silk fibroin, a natural protein forming the structural core of silk filaments, holds biocompatibility, mechanical properties and biodegradation rate suitable for applications in bone regeneration. However, in the past, SF has shown some limitations, especially in terms of bioactivity and effective differentiating ability of hMSCs in regenerating bone tissue. In this work, we wanted to demonstrate that SF, properly processed, chemically modified, and conjugated with selected bioactive species, can be used to prepare different systems: a functionalised scaffold; a bioresorbable material with mineralization ability; an implantable immunomodulatory material. The experimental activities performed and the deep investigation of the properties of the SF-based systems prepared, led to promising results, indicating that SF could be a flexible and powerful platform for the realization of different therapeutic tools. For some of the SF-based systems described in this dissertation, further studies are needed to assess the biological activity of the materials prepared.

In this study, polypropylene (PP) based nanocomposites were prepared by incorporating different kinds and amounts of silica nanoparticles and graphite nanoplatelets (GNP). The role of various percentages of compatibilizer polypropylene grafted with maleic anhydride (PPgMA) into PP nanocomposites was also investigated. In order to analyze the effect of the manufacturing process on the material’s properties, the samples were produced by (i) melt compounding and compression molding and (ii) extrusion and injection molding. It was found that injection molding provides significantly greater stiffness and strength compared to compression molding for all types of PP nanocomposites. Several characterization techniques were used in order to correlate the microstructure to the physical and mechanical properties of the materials. Both silica and GNP were found to be effective nucleating agents, significantly increasing the crystallization rate during isothermal crystallization and favoring the nucleation of the the β- phase, which manifests superior impact strength and toughness compared to the most common α-form crystals. Graphite nanoplatelets were found more efficient in inducing polymorphism and favoring the formation of a transcrystalline phase on the filler surface. A significant correlation between the tensile modulus, glass transition temperature and the amount of constrained phase, as assessed through tensile and DMA analyses, revealed the presence of a secondary reinforcing mechanisms, which, concurrently to the primary stiffening effect of the high modulus filler, contributes to the enhancement of the bulk properties. A complex constrained phase, responsible for providing a secondary reinforcing mechanism, was modeled as immobilized amorphous and transcrystalline regions located at the filler surface. The non-linear viscoelastic creep of the composites, successfully studied by the application of the time strain superposition principle (TSSP), showed a considerable enhancement of the creep stability in nanocomposites with respect to unfilled PP, especially for higher creep stresses. The study of creep dependance on the temperature showed that the stabilizing effect provided by the nanoparticles was more effective at high temperatures and, considering the time temperature superposition principle (TTSP), at long loading times. The equivalence between the time strain- and time temperature- superposition principle was substantiated by comparing the correspondent superimposed master curves. The nanofilled PP matrices have also been used for the preparation of microcomposites reinforced with short glass fibers (GF). Interfacial shear strength (ISS) was measured by means of the single fiber fragmentation test on various PP/GF microcomposites. Results show that the strength at the fiber/matrix interface can be remarkably increased when using nanocomposite systems, especially in the case of dimethyldichlorosilane-functionalized silica nanoparticles and GNP platelets, and that the improvement is further increased when the nanoparticles are used in combination with PPgMA. The thermodynamic fiber/matrix work of adhesion, estimated by contact angle measurements, showed a good correlation with the ISS values. Hybrid composites reinforced with short glass fibers and nanofillers were produced and characterized in order to investigate how the morphology and the mechanical properties of the composites were affected by the combined effect of two fillers of rather different size scales (i.e. micro- and nano- scale). The stronger fiber/matrix adhesion combined with the enhancement of the matrix properties resulted in superior tensile properties and impact resistance and improved viscoelastic behavior. As means of comparison, thermosetting hybrid composites based on epoxy resin were also produced by incorporation of GNP and short GF.

Due to an increasing attention to environment preservation and the need to accomplish new regulations, a general interest to improve the recyclability of composite materials has recently emerged. In order to fulfill this new requirements, a possible strategy could be represented by the development of so-called "single polymer composites" (SPCs), i.e. composite materials in which both matrix and reinforcement have the same chemical composition. The main advantage of SPCs is that, unlike traditional heterogeneous composites (such as glass- or carbon reinforced polymer composites), they can be entirely melted down at the end of the product life for recycling. After an optimization of the annealing treatment to improve the mechanical properties and thermal stability of the reinforcing phase, SPCs containing Vectran® micro- and nano- fibers as a reinforcement were prepared, and their thermo-mechanical properties and recyclability were investigated using a multidisciplinary approach. Single polymer micro composites (SPMCs) containing up to 30 wt% of reinforcing microfibers showed a outstanding improvement of tensile modulus (up to 160 %) compared with the unfilled matrix. FESEM observations evidenced some pull-out phenomena, indicating a poor interfacial adhesion. After a surface treatment on the reinforcement, a composite containing up to 20 wt% showed a remarkable improvement of almost 180% in the tensile modulus compared with the unfilled matrix. FTIR and thermal analysis evidenced its recyclability. Single polymer nano composites (SPNCs) containing up to 10 vol% of reinforcing nanofibers showed an increase by almost 20% of their tensile modulus and strength in comparison with the unfilled matrix. Optical observations revealed a consolidation problem in the unfilled matrix due to the adapted film-stacking process used. However, the addition of the nanofibers in the composite eliminated the problem. Thermal analysis was used to ensure the SPNCs recyclability. Vectran® single polymer micro- and nano- composites have been proven to be possible candidates to substitute traditional heterogeneous composites materials, with enhanced recyclability features.

This thesis was dedicated to decorate graphene sheets with metal and metal oxide nanostructures by RF sputtering technique. Two main objectives were focused in this thesis. 1) To decorate graphene sheets uniformly with metal and metal oxide nanostructure without agglomeration. 2) To explore different kinds of application of decorated graphene sheets with metal and metal oxide nanostructures In the first step, we presented the experimental study results about Nb2O5 deposition onto graphite nanoplatelets (GNPs) by the variation of the deposition process parameters. The structural, chemical and electronic properties of the decorated GNPs with Nb2O5 layers were studied. It was found that with deposition of Nb2O5 layers onto GNPs, tensile strain was developed into the planes of the GNPs. The induced tensile strain in and between the planes of GNPs increased with raising the amount of the Nb2O5 concentration. TEM images shows that GNPs decorated with around 5 to10 nm uniform layer of Nb2O5 at 100 W on their surface were successfully fabricated. From the XPS analysis it was confirmed that, by increasing Nb2O5 layer thickness on the GNPs surface with rising RF power values binding energy downshift in C 1s peak suggests a p-type doping of GNPs due to charge transfer at the interface as a consequence of the higher work function difference between the Nb2O5 (4.70 eV) and GNPs (4.33 eV). In the second step, the interface between the graphene sheets and Nb2O5 nanoparticles were studied. It was established that the structural defects were pronounced with increasing amounts of the Nb2O5 concentration. XPS measurement on graphene/Nb2O5 suggests p-type doping of graphene due to charge transfer at the interface as a consequence of the high work function of Nb2O5. The strong p-doping effect was also confirmed by Raman analysis where the positions of the G and 2D peaks of graphene gradually upshifted upon increasing the Nb2O5 concentration. The uniform distribution of decorated Nb2O5 nanoparticles onto graphene was confirmed from TEM analysis. The ferromagnetic behavior was observed for the undecorated graphene and decorated graphene with Nb2O5 nanoparticles. The ferromagnetic behavior of graphene was enhanced with decoration of the Nb2O5 nanoparticles. In the third step, the effect of the Mg concentration on the structural, chemical and morphological properties of the graphene was described. Well dispersed Mg nanoparticles were decorated onto graphene sheets. It was found that from the XRD results, different sizes of the crystalline Mg nanoparticles were obtained onto graphene sheets with variation of the process parameters.. Raman spectra indicated that G and 2D bands of the graphene were shifted to higher wavenumber with deposition of Mg nanoparticles. The well dispersed and small size of Mg nanoparticles in the range of (8-12 nm) onto graphene sheets was decorated by using a high powder vibration frequency. No agglomeration of the sputtered particles was observed with high powder vibration frequency. This observation was confirmed by TEM micrographs. XPS analysis revealed that the decorated Mg nanoparticles onto graphene were oxidized due to exposure to the atmosphere. The well dispersed decorated Mg nanoparticles onto graphene sheets were studied for the hydrogen absorption and desorption at two different temperatures 330 oC and 360 oC at 2 and 8 bars pressure. The hydrogen up taking capacity for the decorated graphene sheets with Mg nanoparticles was 3 wt. % in whole composite. However, the up taking hydrogen storage capacity of the only Mg nanoparticles was 6.6 wt. %. In the last step, the interaction of the graphene sheets with TiO2 nanoparticles was studied. The XRD results indicated that the lattice of the graphene sheets was distorted with increasing amount of the TiO2 concentration. The particle nature of the deposited TiO2 was confirmed by TEM examination and also the TEM analysis shows that TiO2 nanoparticles were uniformly distributed onto graphene sheets. The Raman analysis showed that the G and 2D bands of graphene were shifted to higher wavenumber with increasing TiO2 concentration onto graphene sheet confirming the p doped graphene with TiO2 nanoparticles. The XPS analysis further confirmed the p doping of graphene upon the deposition of the TiO2 nanoparticles. The binding energy downshift the C 1s core level of was observed after charge transfer from graphene to TiO2 nanoparticles due to the larger work function of TiO2 relatively to that of graphene. It was observed that decorated graphene sheets with TiO2 nanoparticles shows reasonably catalytic activity.

Two-dimensional transition metal dichalcogenides (TMDCs) aroused significant interest in the last years as semiconductor materials for application in the field of electronics, due to their tunable bandgap, good carrier mobility, and strong light absorption. Among TMDCs, two-dimensional molybdenum disulfide (2D-MoS2) has been the most investigated for electronic and optoelectronic applications, like transistors and photodetectors. 2D-MoS2 can particularly benefit from the excellent light matter interaction properties in the UV-VIS spectrum combined with good charge carrier transport properties. The literature reports photodetectors based on 2D-MoS2 fabricated with different techniques, including exfoliation, chemical vapor deposition (CVD) and wet chemical synthesis. However, it is still challenging to scale the proposed devices to the industrial level, due to the lack of a versatile fabrication process that ensures both reproducibility and scalability. A possible solution to this could rise from wet chemical synthesis. In the first part of this work, I discuss the development and optimization of a fabrication method for MoS2 thin films based on a sol-gel process which allows for scalable productions. This route allowed the fabrication of large area (~cm2) MoS2 thin films of 200 nm thickness on technological relevant substrates (i.e., glass, gold, silicon). The films displayed good uniformity, although the crystallinity was affected by residual impurities. The films produced with this technique were employed for the fabrication of photodetectors, displaying responsivity of few mA/W in the NUV-VIS-NIR spectrum. However, the performance of the device was affected by a still limited quality of the MoS2 films obtained with the current method that require further optimization. Further studies will overcome the current limitations and solutions to be investigated in future works are proposed. The second part of this work focuses on expanding the detection capability of 2D-MoS2 (currently limited to the UV-VIS-NIR spectrum), by exploring for the first time X-rays sensing, taking advantage of the X-ray cross section of MoS2 associated with the high atomic number Z of Mo. A detector based on an exfoliated MoS2 monolayer (1L-MoS2) was fabricated and characterized for the purpose. The detector showed direct detection of ~10^2 keV X-rays down to dose rates of 0.08 mGy/s, with X-ray sensitivity is in the range 10^8-10^9 µC ⋅Gy-1·cm-3, outperforming most of the reported organic and inorganic materials. A strategy to improve the device response was also studied by adding a scintillator film, which resulted in a three-fold increase of the signal. These results suggest to consider 2D-MoS2 for in-vivo dosimetry applications.

In the last decade nanotechnologies have greatly developed in many research ï¬ elds such as engineering, electronic, biological and many others. They can offer several possibilities to design tools, to create new techniques or improve the already existing ones, to discover innovative applications. And nanotechonology research is just at the beginning. One of the most interesting thing of this topic is the size of nanostructures. These materials are thousand times smaller than a cell and have a compatible size with proteins, enzymes and a lot of biological molecules. For this reason many research groups specialized in biotechnology started to invest people and resources in this new scientiï¬ c possibility. Following this very promising trend, BIOtech, a research group for biotechnology at the University of Trento, has proposed the Nanosmart project. Developed together with many prestigious institutes all over the world, this project aims to exploit the nanotechnology possibilities in biological research. The purpose of this challenge is the design, development and production of magnetic nanoparticles to use them in diagnostics and therapy of cancer disease. Magnetic nanoparticles (MNP) are spherical agglomerates of iron oxide, few tens of nanometers, which can be exploited in many ways. Being magnetic they can be used as contrast agents in magnetic resonance imaging MRI. Together having a high absorbing coefficient in the radio frequency band, they can locally increase the temperature of the tissues hosts and this being used for hyperthermia treatments. Entrapping some drugs in one of their multilayers, MNP can be used as inert carriers for drug delivery: due to their small size they can enter biological tissues, cross the plasma membrane of cells and release the drug only on predetermined targets. My Ph.D. started together with the project; so I had the possibility to follow this research from the beginning. In this years many problems have been handled, many errors have been made, many brilliant ideas have been shelved but also new abilities have been acquired, important collaborations were born and alternative structures have been thought and, fortunately, realized. Trying to eliminate unnecessary things and focusing on main purpose of this work, in this thesis I want to illustrate just the long â€œï¬ l rouge†that connects the idea of producing a nanoparticle that can cure tumor to the point of verify its effectiveness.

Nowadays the environmental sustainability and the limitation of the energy consumption of buildings is of substantial importance in order to reduce greenhouse gases emissions and mitigate the consequences of climate change. Thermal energy storage (TES) allows to store thermal energy when available in order to use it when and where necessary. The use of insulating materials with TES capability may results in the compensation of energy absorption peaks caused by air conditioning or by space heating with a consequent reduction of energy consumption and related CO2 emissions. This work aims at the development and characterization of composite materials based on polymeric foams and containing a phase change material providing the TES capability. The production procedures were optimized in order to maximize the quality of the samples and the main properties of the resulting materials were then investigated. Different matrices were considered in this work: thermosetting, thermoplastic and elastomeric ones. As thermosetting matrix, a polyurethane foam was considered: this foam was filled, during the production process, with increasing amounts (from 10 to 40 wt%) of a microencapsulated PCM with a melting point of 24 °C. The addition of the PCM caused the disruption of the regular close cell morphology of the foams with a consequent increase of the thermal conductivity and a reduction of the mechanical properties. On the other hand, the addition of the PCM led to interesting TES properties, measured both through differential scanning calorimetry and infrared thermography (up to 54 J/g). Polyethylene was chosen as thermoplastic matrix and the technology of salt leaching was used to obtain foams without the use of chemical foaming agents. Foams containing different amounts (up to 56 wt%) of a microencapsulated PCM with a melting point of 24 °C were prepared. The addition of the PCM led to a decrease of the connectivity and porosity values of the prepared foams with a consequent decrease of the mechanical properties and increase of the thermal conductivity. Despite the rupture of a certain part of the PCM capsules due to the production process, good TES properties (up to 50 J/g) were measured. Elastomeric foams were prepared using an EPDM rubber as matrix and different foaming agents for the expansion process: foams obtained using two different commercial foaming agents were compared with foams obtained using the salt leaching technique. In the first case, a shape-stabilized PCM was added during the production process, while in the second one the foams were impregnated with a liquid PCM without the necessity of a shape stabilization. Salt leaching foams were able to retain higher PCM loads with respect to foams produced using commercial foaming agents and were therefore characterized by higher TES capability (up to 129 J/g). Infrared thermography tests highlighted that the time required to reach a reference temperature during heating/cooling cycles was three times longer for samples with a PCM amount of about 55 wt%. These foams evidenced a general decrease of the mechanical properties upon PCM addition. Moreover, a strong influence of the temperature on the mechanical behaviour of these foams was highlighted, with the PCM acting as softener above its melting point and as hardener below. In order to consider practical applications, elastomeric panels made of an ethylene propylene diene monomer (EPDM) rubber filled with a shape stabilized PCM and covered with a nitrile-butadiene rubber (NBR) envelope were prepared. It was possible to verify the absence of leakage, the uniform distribution of the PCM and the influence of temperature on the mechanical properties of the samples. From rheological tests it was also possible to observe the plasticizing effect of the PCM that hindered the vulcanization process of the EPDM/PCM compound. In the second part of this work larger samples were prepared and used for the internal insulation of wood boxes that were subjected to heating/cooling cycles, simulating thus real summer conditions in north Italy. The beneficial effect of the PCM resulted in a consistent reduction of the temperature peak with respect to a reference box insulated with elastomeric panels without PCM. Moreover, the fire behaviour of the produced samples was studied and the effect of the addition of different flame retardants was deeply investigated. The addition of a flame retardant based on ammonium polyphosphate and aluminium diethyl phosphinate as synergistic agents allowed a strong reduction of the peak of heat release rate measured through cone calorimeter tests, with a significant improvement of the fire behaviour. Fire tests allowed also to point out the significant role, in improving the fire performances of the samples, of the interactions between ammonium polyphosphate and the mineral fillers present in the EPDM/PCM compound (clay) and in the envelope (talc, kaolin and silica). A better comprehension of the combustion mechanisms and of the flame retardant efficacy was achieved through the analysis of the combustion residues. Finally, the specific enthalpy of the different systems was evaluated with respect to the cost of the raw materials used in the production stages in order to classify them on the basis of their melting enthalpy and on the economical aspects.

This PhD work mainly focus on the synthesis and characterization of calcium phosphate powders for plasma spray coating. The preparation of high temperature phase stabilized βTCP and HA/βTCP powders for plasma spray coating applications has been the topic of investigation. Nowadays plasma sprayed coatings are widely used for biomedical applications especially in the dental and orthopaedic implantation field. Previously Ti based alloys were widely used for the orthopaedic and dental implant applications because of its high corrosion and good biocompatibility. Due to the limited osteoconductivity edges of Ti implants with fibrous tissues delays the healing time. To overcome these limitations different types of surface modification processes are employed on the surface of Ti. The coating of HA is a widely used surface modification technique due to its excellent biological properties. HA is a well employed bone graft material due to its similarity with human hard tissues. The plasma spraying of HA on the Ti surface is the most widely used technique mainly due to its process simplicity, low cost and bulk production. The present research focuses on the modification of HA coatings for the improvement of bio-degradation properties of HA. HA/βTCP composite powders are used to overcome the poor biodegradation properties of HA. The issue related to the use of βTCP is the phase transformation (β to α) at high temperature. To overcome this phase transformation, the βTCP powder was doped with MgO. The high temperature phase stabilized MgO doped βTCP and HA/βTCP powders were synthesized by solid state method and granulated using spray granulation. The properties of the granulated powders (100-150μm) were analysed with XRD, FT-IR, SEM, flowabilty, density etc. and are used in plasma spray coating process. The produced coatings were subjected to the thermal treatment and βTCP and HA/βTCP plasma sprayed coatings are obtained. The successively produced coatings were characterized, and the invitro properties like solubility and bioactivity behaviours were studied.

This thesis is focused on the synthesis and structural characterization of hybrid Organic-Inorganic materials with different application fields (materials for VOC sensing and for polymer–based nanocomposites), exploiting the conventional sol-gel method or the Nano Building Block (NBBs) approach with the in situ water production route. In the first part of the work the co-condensation of TEOS and organofunctional alkoxysilanes allowed preparation of Hybrid Sol-Gel Networks The synergic use of XRD with NMR allowed to study in deep the phase interaction. The hybrid coatings, prepared by dip-coating technique demonstrated similarity in structural features with the bulk xerogels. Two different approaches were combined to study the coatings sorption ability towards selected Volatile Organic Compounds (VOC). The coatings appeared promising in the field of detection and removal of VOCs at low temperatures, possessing the ability to quickly desorb entrapped volatiles. Fine adjustments of such hybrids can allow to discriminate between similar compounds and decrease the water sorption phenomenon, since not only the microstructure, but the polarity of the effective hybrid coatings surface plays decisive role in sorption process. In the second part of the work the synthesis parameters were fine-tuned in order to obtain Si-based SH–functionalized NBBs. The water provided in-situ through the esterification reaction of chloroacetic acid and 1-propanol enabled the hydrolysis-condensation of –SH functionalized alkoxysilane. The choice of exploited catalyst (TFA or DBTL) and esterification reaction parameters variations clearly ruled out the preferences in NBBs structural units formation. Varying the reaction temperature conditions allowed to follow the kinetics of esterification reaction and relate the water production rate to the kinetics of NBBs growth, highlighting strong correlation of H2O availability to condensation extent. The complementary exploitation of multi-nuclear NMR, FTIR and GPC techniques elucidated in full complexity the NBBs structural features development during the reaction.