Boli pripravené kryty rán na bázi prírodných látok polyvinyl alcohol/ hyaluronan/ strieborné nanočastice (PVA/ HA/ Ag-NPs). Hyaluronan bol použitý ako redukčné a stabilizačné činidlo pre syntézu nanočastíc striebra. Pri príprave Ag-NPs boli testované viaceré parametre ako koncentrácia dusičnanu strieborného ako zdroja Ag-NPs (0,01; 0,1;0,5;1 M), koncentrácia kyseliny hyalurónovej (1,2 %) a jej rozdielna molekulová hmotnosť. Kryty rán z nanovlákien boli pripravené pomocou techniky electro-spinning z roztokov líšiacich sa pomerom PVA a HA/Ag-NPs (100; 90/10; 80/20; 60/40; 50/50). Vlastnosti nanokompozitu HA/Ag-NPs boli hodnotené pomocou TEM, reológie, DLS, XRD, UV/Vis spektroskopie a kryty rán boli charakterizované pomocou SEM, TGA, FTIR a ťahovej skúšky.

Růst krystalů zásadně ovlivňuje morfologii a tím také mechanické vlastnosti semikrystalických polymerů. Tato PhD práce přináší alternativní pohled na popis kinetiky krystalizace v polyolefinech plněných slabě interagujícími částicemi. V nanokompozitních materiálech vysoký specifický povrch plniva i při nízkých plněních zásadně ovlivňuje dynamiku řetězců. V blízkosti povrchu plniva začíná hrát významnou roli zpomalená reptace způsobená jak vzájemnými interakcemi plnivo-polymer tak prostorovým omezením mezi nanočásticemi. Růst krystalů byl zkoumán pomocí polarizovaného optického mikroskopu vybaveného horkým stolkem. Výsledky byly korelovány s teoretickými modely a rozsáhlými počítačovými simulacemi na molekulární úrovni. Pozorovaný pokles rychlosti růstu sférolitů v závislosti na obsahu plniva a molekulové hmotnosti matrice je interpretován na základě imobilizační teorie, tedy, zpomalení reptačního pohybu.

The dissertation thesis submitted deals with the study of dielectric properties of epoxy nanocomposites containing nanoparticles of inorganic oxides. These nanocomposites may have a promising technologic application for electric insulations in view of their higher resistance against partial discharges; yet information about their behavior in the course of ageing is not available. If at least a partial mass replacement of the currently used epoxy insulation with nanocomposite-based insulations is due to occur, the knowledge of the changes of their dielectric properties in the course of their operation will become indispensable. Within the framework of this dissertation, ensembles of samples of epoxy resins without fillers and with Al2O3, WO3, TiO2 and SiO2 fillers in the form of nanopowders, in concentrations up to 12 wt %, have been prepared. These ensembles have been measured prior to ageing and exposed to long-time (up to 5000 hours) ageing at increased temperatures 200, 250 and 300 °C and in a few cases also at 330 and 360 °C. Samples were measured in the course of ageing roughly in a logarithmic time series after 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000 and 5000 hours. The measured quantities included complex permittivity , internal resistivity i and loss factor tan at temperatures ranging from -153 °C to +167 °C and in the frequency range 10-2 – 106 Hz. Changes in nanocomposites have been investigated using not just dielectric spectroscopy measurements, but other methods, too, namely Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The experiments have proved that materials with different fillers respond to the same concentrations of various fillers in different ways. The addition of nanoparticles, without the addition of microparticles, at a relatively low concentration (max 12 wt %), was not sufficient for reaching fundamental changes in dielectric spectrum; only smaller changes of dielectric strength and shifts of relaxations and in relaxation maps have occurred. Out of more pronounced changes, increase of concentration of the SiO2 filler in the epoxy matrix brings about a decrease of electrical conductivity in the resulting nanocomposite. The TiO2 filler had a different impact. Different TiO2 concentrations make their marked appearance in the region between the relaxation and relaxation. The TiO2-filled nanocomposites do not exhibit the unambiguous dependence of electrical conductivity on nanofiller concentration. It can be concluded that the mere addition of nanoparticles, without the addition of established microparticles, does not change the dielectric spectrum substantially. Generally, a serious problem was the production of the nanocomposite with a uniform distribution of nanoparticles. The preparation of such a nanocomposite was not trivial and, in industrial applications, this issue will require a specific focus, so as to avoid the formation of undesirable aggregates. Within the framework of this research, a methodology for the production of an epoxy nanocomposite has been developed with as high as possible uniformity of nanoparticle distribution.

Glasses and ceramics offer several unique characteristics over polymers or metals. However, they suffer from a shortcoming due to their brittle nature, falling short in terms of fracture toughness and mechanical strength. The aim of this work is to reinforce borosilicate glass matrix with reinforcements to increase the fracture toughness and strength of the glass. Boron nitride nanomaterials, i.e. nanotubes and nanosheets have been used as possible reinforcements for the borosilicate glass matrix. The tasks of the thesis are many fold which include: 1. Reinforcement of commercially derived and morphologically different (bamboo like and cylinder like) boron nitride nanotubes in borosilicate glass with the concentration of 0 wt%, 2.5 wt% and 5 wt% by ball milling process. Same process was repeated with reinforcing cleaned boron nitride nanotubes (after acid purification) into the borosilicate glass with similar concentrations. 2. Production of boron nitride nanosheets using liquid exfoliation technique to produce high quality and high aspect ratio nanosheets. These boron nitride nanosheets were reinforced in the borosilicate glass matrix with concentrations of 0 wt%, 2.5 wt% and 5 wt% by ball milling process. The samples were consolidated using spark plasma sintering. These composites were studied in details in terms of material analysis like thermo-gravimetric analysis, detailed scanning electron microscopy and transmission electron microscopy for the quality of reinforcements etc.; microstructure analysis which include the detailed study of the composite powder samples, the densities of bulk composite samples etc; mechanical properties which include fracture toughness, flexural strength, micro-hardness, Young’s modulus etc. and; tribological properties like scratch resistance and wear resistance. Cleaning process of boron nitride nanotubes lead to reduction in the Fe content (present in boron nitride nanotubes during their production as a catalyst) by ~54%. This leads to an improvement of ~30% of fracture toughness measured by chevron notch technique for 5 wt% boron nitride nanotubes reinforced borosilicate glass. It also contributed to the improvement of scratch resistance by ~26% for the 5 wt% boron nitride nanotubes reinforced borosilicate glass matrix. On the other hand, boron nitride nanosheets were successfully produced using liquid exfoliation technique with average length was ~0.5 µm and thickness of the nanosheets was between 4-30 layers. It accounted to an improvement of ~45% for both fracture toughness and flexural strength by reinforcing 5 wt% of boron nitride nanosheets. The wear rates reduced by ~3 times while the coefficient of friction was reduced by ~23% for 5 wt% boron nitride nanosheets reinforcements. Resulting improvements in fracture toughness and flexural strength in the composite materials were observed due to high interfacial bonding between the boron nitride nanomaterials and borosilicate glass matrix resulting in efficient load transfer. Several toughening and strengthening mechanisms like crack bridging, crack deflection and significant pull-out were observed in the matrix. It was also observed that the 2D reinforcement served as more promising candidate for reinforcements compared to 1D reinforcements. It was due to several geometrical advantages like high surface area, rougher surface morphology, and better hindrance in two dimensions rather than just one dimension in nanotubes.

Des nanocomposites polyuréthane-argent (PU-Ag) ont été élaborés à l'aide de deux procédés respectueux de l'environnement et du manipulateur, dans le but de prévenir la colonisation microbienne de ces matériaux. Le premier consiste à incorporer une dispersion aqueuse de nanoparticules d'argent, réalisée ex situ, au cours du procédé de synthèse d'un PU en dispersion aqueuse. Une dispersion de nanoparticules d'argent obtenue par réduction chimique, sous micro-ondes, d'ions d'argent en présence de polyéthylèneglycol a été développée dans l'objectif d'intégrer chimiquement le PEG dans les chaînes de PU. Le second procédé réside dans la réduction photochimique, in situ, d'ions argent dans une matrice PU, en l'absence de tout autre composé chimique.La caractérisation des matériaux obtenus montre une dispersion homogène des nanoparticules d'argent avec des tailles de particules faibles (5 à 50 nm] et une activité biocide des surfaces vis-à-vis de deux souches bactériennes (Pseudomonas aeruginosa et Enterococcus faecalis) sans modification notable des propriétés physicochimiques intrinsèques du PU. / Two environment and human-friendly processes were developed to synthesize polyurethane-silver (PU-Ag) nanocomposites having biocide surfaces able preventing the microbial colonization.The first one, called ex-situ process, consists in incorporating a silver nanoparticles aqueous dispersion during the synthesis process of polyurethane, which is itself carried out in aqueous dispersion. In this case, the chemical reduction of silver ions under microwaves and in the presence of polyethyleneglycol was particularly developed with the aim to chemically incorporate the PEG in the PUchains. For the second process, silver ions dispersed inside a PU matrix were photochemically reduced in situ.The obtained materials exhibit a homogeneous dispersion of silver nanoparticles with small diameter (from 5 to 50 nm) without marked modification of the intrisic physomchemical properties of the PU. Lastly, the antibacterial properties of the surfaces aginst Pseudomonas aeruginosa and Enterococcus faecalis were confirmed.

The aim of the work is characterization of structure and magnetic properties of various CoFe2O4/SiO2 nanocomposites. Emphasis was put on the corelation of the magnetic properties with particle size (samples with different annealing temperature) and with strenght of the interparticle interactions (samples with different Fe/Si ratio or without silica matrix). Structure properties of all samples were determinated by powder x-ray diffraction, scanning and transmission electron microscopy. Magnetic properties were determinated by standard (temperature dependence of magnetization, magnetization isotherms) and advanced (a.c. susceptibility, memory effects) magnetic measurements. A sharp increase of the values of blocking temperature and coercivity with increase of strenght of the interparticle interactions and with increase of particle size was observed. Particle size determines the maximum value of coercivity and blocking temperature and strengh of the interparticle interactions shift this values in the interval determined by particle size.

Title: Preparation of Nanocomposites of Metal Oxides in Plasma Polymer and Study of Their Properties Author: Oleksandr Polonskyi Department: Department of Macromolecular Physics, MFF UK Supervisor of the doctoral thesis: Prof. RNDr. Hynek Biederman, DrSc. Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University in Prague Abstract: This thesis is devoted to a study of nanocomposite films Al (Al oxide)/plasma polymer prepared by various techniques using magnetron sputtering, plasma polymerization and cluster beam deposition. The formation and deposition of metal/metal oxide nanoclusters using a gas aggregation cluster source (GAS) was also considered. The role of low concentration of oxygen in the aggregation gas on the process of Al and Ti cluster deposition was studied. Properties of the nanoclusters and nanocomposite films were characterized by various techniques. Morphology of the nanocomposites was examined by AFM, TEM or HRTEM and SEM. Elemental analysis and chemical composition of the films were studied by XPS and FTIR. Optical characterization of the prepared films was done by UV-Vis spectroscopy and spectroscopic ellipsometry. It has been shown that using GAS nanocomposite Al(AlxOy)/C:H may be prepared. Keywords: nanocomposite thin film, plasma polymer, metal...

With the development of modern industrial engineering technology, increasing demands of multifunctional materials drive the exploration of new applications of electrical conductive polymer nanocomposites (CPNCs). Toward applications of smart materials, sensing performance of CPNCs has gained immense attention in the last decade. Among them, strain sensors, based on piezoresistive behavior of CPNCs, are of high potential to carry out structural health monitoring (SHM) tasks. Poly(vinylidene fluoride) (PVDF) is highly thought to be potential for SHM applications in civil infrastructures like bridges and railway systems, mechanical systems, automobiles, windgenetors and airplanes, etc. because of its combination of flexibility, low weight, low thermal conductivity, high chemical corrosion resistance, and heat resistance, etc. This work aimed to achieve high piezoresistive sensitivity and wide measurable strain ranges in carbon nanotube based poly(vinylidene fluoride) (PVDF) nanocomposites. Four strategies were introduced to tune the sensitivity of the relative electrical resistance change (ΔR/R0) versus the applied tensile strain for such nanocomposites. Issues like the influence of dispersion of multi-walled carbon nanotubes (MWCNTs) on initial resistivity of PVDF nanocomposites and conductive network structure of MWCNTs, as well as piezoresistive properties of the nanocomposites, were addressed when using differently functionalized MWCNTs (strategy 1). In addition, the effects of crystalline phases of PVDF, mechanical ductility of its nanocomposites and interfacial interactions between PVDF and fillers on piezoresistive properties of PVDF nanocomposites were studied. Using hybrid fillers, to combine MWCNTs with conductive carbon black (strategy 2) or isolating organoclay (strategy 3), piezoresistive sensitivity and sensing strain ranges of PVDF nanocomposites could be tuned. Besides, both higher sensitivity and larger measurable strain ranges are achieved simultaneously in PVDF/MWCNT nanocomposites when using the ionic liquid (IL) BMIM+PF6- as interface linker/modifier (strategy 4). The detailed results and highlights are summarized as following: 1. The surface functionalization of MWCNTs influences their dispersion in the PVDF matrix, the PVDF-nanotube interactions and crystalline phases of PVDF, which finally results in different ΔR/R0 and the strain at the yield point (possibly the upper limit of sensing strain ranges). As a whole, regarding to the fabrication of strain sensors based on PVDF/MWCNT nanocomposite, in contrast to pristine CNTs, CNTs-COOH and CNTs-OH, CNT-NH2 filled PVDF nanocomposites possess not only high piezoresistive sensitivity but also wide measurable strain ranges. Gauge factor, i.e. GF, is ca.14 at 10% strain (strain at the yield point) for the nanocomposites containing 0.75% CNTs-NH2. 2. Using hybrid fillers of CNTs and CB to construct strain-susceptible network structure (conductive pathway consisting of string-like array of CNTs and CB particles) enhances the piezoresistive sensitivity of PVDF nanocomposites, which is tightly associated with the CNT content in hybrid fillers and mCNTs/mCB. The best piezoresistive effect is achieved in PVDF nanocomposites with fixed CNT content lower than the ΦC (0.53 wt. %) of PVDF/CNT nanocomposites. 3. ΔR/R0 and possible sensing strain ranges of PVDF nanocomposites were tailored by changing crystalline phases of PVDF and PVDF-MWCNT interactions. Besides, the increase of the strain at yield point in PVDF nanocomposites filled by CNTs-OH is more obvious than that in the nanocomposites containing the same amount of clay and CNTs. The nanocomposite consisting of 0.25% clay and 0.75% CNTs-OH have ca. 70% increase of the strain at the yield point (17%) and the GF at this strain is ca. 14, while GF for the nanocomposite filled by only 0.75% CNTs-OH is ca. 5 at 10% strain. 4. IL BMIM+PF6- served as interface linker for PVDF and MWCNTs, which significantly increased the values of ΔR/R0 and strain at the yield point of PVDF nanocomposites simultaneously. Besides, this increases with increasing IL content. With the aid of IL, the dispersion of nanotube and toughness of the nanocomposites are greatly improved, but the electrical conductivity of the nanocomposites is decreased with the incorporation of IL, which is related to the IL modified PVDF-MWCNT interface connection or bonding. GF reaches ca. 60 at 21% strain (the strain at the yield point) for PVDF nanocomposites filled by 10% IL premixed 2%CNTs-COOH.

<p>Vertically aligned nanocomposite (VAN) thin films are a promising thin-film platform that allows the combination of a highly desired material with another complementary oxide. Traditionally, VANs have been limited to combining an oxide with another oxide which has shown a wide range of functionality, and, by adjusting the different growth parameters, it has led to the tuning of their physical properties. While VANs have already shown to be an effective platform with immense potential, further enhancement of physical properties can be performed by replacing one of the oxides with a metal forming metal-oxide VANs. </p> <p>In this dissertation, by the inclusion of the 3d transition metals, e.g., Fe and Co, into various oxide matrices, such as La_0.5Sr_0.5FeO₃, BaZrO₃, and BaTiO₃, strong, highly anisotropic, ferromagnetic properties have been achieved. By varying the growth parameters, tunable physical properties, mainly coercivity and anisotropic ratio, have been demonstrated. Furthermore, in the case of Co-BaZrO₃, a multi-layer stack has been successfully grown and demonstrated a tailorable magnetoresistance. Additionally, a novel system by combining Fe pillars into a BaTiO₃ matrix has been demonstrated. This new system allows for the combination of the room temperature Fe ferromagnetic properties with the ferroelectric properties of BaTiO₃, allowing for coupling between the two with coercivity tuning and tailorable ferromagnetic properties. </p> <p>Lastly, it has been shown a possible framework by adding additional metals into the existing metal-oxide VAN platform. By adding the third phase, another metal, it opens up a new avenue to induce additional functionality while creating a method to introduce coupling between the different metals and physical properties. </p> <br>

Epoxy resins have been broadly used in the industry for adhesives, laminates, coatings, composites, encapsulation of electronic devices, printed circuit boards, etc. Despite their excellent adhesion to different materials, heat and chemical resistance and good mechanical properties, they also exhibit few drawbacks like brittleness, high thermal expansion coefficient (CTE), poor resistance to crack initiation and growth. Therefore, the thesis is focused on the preparation of epoxy-silica hybrid materials exhibiting improved thermomechanical properties compared to the neat epoxides, without impairing their beneficial features. The main synthetic route of epoxy-silica hybrids' preparation has been the sol-gel process of alkoxysilanes, allowing either in-situ formation of high purity and homogeneity silica particles or creation of various siloxane structures in a form of liquid (sol) silica-based precursors. The sol-gel method, on one hand, helps to omit too high viscosity of nanofiller suspension and energy-intensive nanofiller dispergation problems, but on the other hand, is often associated with necessity to use solvents and to remove formed volatiles. Therefore, in the first part of the thesis, a simple solvent-free sol-gel procedure, enabling to minimize the side-effect of solvent evaporation and...