In this study, the effects of chain extension and branching on the properties of nanocomposites produced from recycled poly(ethylene terephthalate) and organically modified clay were investigated. As the chain extension/branching agent, maleic anhydride (MA) and pyromellitic dianhydride (PMDA) were used. The nanocomposites were prepared by twin-screw extrusion, followed by injection molding. Recycled poly(ethylene terephthalate), was mixed with 2, 3 and 4 weight % of organically modified montmorillonite. During the second extrusion step, 0.5, 0.75 or 1 weight % of MA or PMDA was added to the products of the first extrusion. As the second extrusion step is reactive extrusion, the anhydrides were added at three different screw speeds of 75, 150, 350 rpm, in order to observe the change of properties with the screw speed. XRD analysis showed that, the interlayer spacing of Cloisite 25A expanded from 19.21 &amp / #506 / to about 28-34 &amp / #506 / after processing with polymer indicating an intercalated structure. PMDA, MA and organoclay content as well as the screw speed did not have a recognizable effect on interlayer distance. In the first extrusion step, nanocomposites containing 3% organoclay content gave significant increase in Young&rsquo / s modulus and decrease in elongation to break values indicating good interfacial adhesion. After the addition of chain extenders, it was observed that both MA and PMDA gave rise to improved mechanical properties of the nanocomposite owing to the branching and chain extending effects that increase the molecular weight. However, PMDA gave better mechanical properties at lower content which makes it a more effective chain extender. DSC analysis showed that MA was more effective in increasing the glass transition temperature and melting temperature in comparison to PMDA.

Noble metal incorporated MCM-41 based nanostructured mesoporous materials have attracted the attention of material researchers in recent years. Sorption characteristics of MCM materials can be improved by surface modification techniques. Besides surface modification, metal nanoparticles can also be produced within the pores of mesoporous materials. MCM-41 can act as host for several metal nanoparticles such as palladium. The present study is focused on the synthesis of Pd-MCM-41 nanocomposite catalytic materials by using different direct synthesis procedures, as well as an impregnation method. Impregnated samples were used to synthesize Pd nanoparticles inside the pores of MCM-41. In the direct hydrothermal synthesis of Pd-MCM-41, incorporation of the Pd metal was achieved by adding PdCl2, K2PdCl4 and Pd(NH3)4(NO2)3 solutions into the synthesis mixture. Syntheses were performed in acidic and basic routes. Hydrothermal synthesis was carried out in an autoclave at 120 oC. The solid product was filtered, washed, dried, calcined at 550 oC in a stream of dry air and reduced in a stream of hydrogen at 200 oC. In the case of impregnation, PdCl2 solution was added to a suspension of MCM-41. The product was evaporated to dryness, dried under vacuum and reduced with H2 gas at 200 oC. Physical and chemical properties and surface morphology of Pd-MCM-41 nanomaterials were characterized by using XRD, XPS, EDS, BET, SEM, TEM and TPR techniques. Very high Pd/Si ratios, as high as 0.45 and 0.18 were obtained in the mesoporous materials produced by the basic and acidic direct synthesis routes, respectively. The BET surface areas of these materials were found as 999 m2/g and 694 m2/g, respectively. These results showed that the basic direct synthesis procedure was highly successful for the incorporation of Pd into the mesoporous Si structure. In addition, EDS analysis of the Pd-MCM-41 materials prepared by the impregnation technique showed that Pd/Si ratios were 0.24 and 0.12 in the two samples having surface areas of 527 m2/g and 883 m2/g, respectively. In conclusion, high surface area of the material synthesized by the basic route together with a higher Pd/Si ratio makes this material more attractive for catalytic and hydrogen storage applications.

Vibration problems are still the major constraint in modern machining processes that seek higher material removal rate, shorter process time, longer tool life and better product quality. Depending on the process, the weaker structure element can be the tool/tool holder, workpiece/fixture or both. When the tool/tool holder is the main source of vibration, the stability limit is determined in most cases by the ratio of length-to-diameter. Regenerative chatter is the most significant dynamic phenomenon generated through the interaction between machine tool and machining process. As a rule of thumb, the ratio between the tool’s overhang length and the tool’s diameter shouldn’t exceed 4 to maintain a stable machining process while using a conventional machining tool. While a longer tool overhang is needed for specific machining operations, vibration damping solutions are required to ensure a stable machining process. Vibration damping solutions include both active and passive damping solutions. In the passive damping solutions, damping medium such as viscoelastic material is used to transform the vibration strain energy into heat and thereby reduce vibration amplitude. For a typical cantilever tool, the highest oscillation displacement is near the anti-node regions of a vibration mode and the highest oscillation strain energy is concentrated at the node of a vibration mode. Viscoelastic materials have been successfully applied in these regions to exhibit their damping property. The node region of the 1st bending mode is at the joint interfaces where the cantilever tools are clamped. In this thesis, the general method that can be used to measure and characterize the joint interface stiffness and damping properties is developed and improved, joint interfaces’ importance at optimizing the dynamic stiffness of the joint interface is studied, and a novel advancing material that is designed to possess both high young’s modulus and high damping property is introduced. In the joint interface characterization model, a method that can measure the joint interface’s stiffness and damping over the full frequency range with only the assembled structure is presented. With the influence of a joint interface’s normal pressure on its stiffness and damping, an optimized joint interface normal pressure is selected for delivering a stable machining process against chatter with a boring bar setting at 6.5 times overhang length to diameter ratio in an internal turning process. The novel advancing material utilizes the carbon nano particles mixed in a metal matrix, and it can deliver both high damping property and high elastic stiffness to the mechanical structure. / <p>QC 20130521</p> / PoPJIM, HydroMod, XPRES, NanoComfort

Structurer les matériaux composites, pour au moins une des phases, à l’échelle nanométrique, c’est-à-dire former des matériaux nanocomposites, est une voie pour optimiser nombre de leurs propriétés. Le domaine de la propulsion et des propergols n’échappe pas à cette règle. C’est dans ce contexte que s’est déroulée cette thèse sur la synthèse de nanocomposites ‘nanoparticules métalliques/polymère’ en milieux fluides supercritiques (FSCs). Les principales étapes rencontrées dans l’élaboration de nanocomposites en milieu scCO2 ont été étudiées : i) Etude thermodynamique des systèmes polymère/scCO2, ii) Mesure de leur viscosité et iii) Synthèse de nanoparticules inorganiques dans des polymères en milieux FSCs. De plus, une partie importante de la thèse a concerné la synthèse de nanoparticules d’aluminium en milieux fluides supercritiques en vue de leur intégration dans des matrices polymères pour des applications propergols. / Structuring composite materials, at least for one phase, at the nanometer scale, that is to say synthesize nanocomposite materials, is an interesting way to optimize their properties. The field of propulsion and propellants follows this rule. This is the context of this PhD dealing with the synthesis of nanocomposites constituted of metallic nanoparticles and polymer in supercritical fluids. The main steps for the formation of nanocomposites in scCO2 have been studied: i) Thermodynamical study of polymer/scCO2 systems, ii) Viscosity measurements of polymer/scCO2 systems and iii) Synthesis of inorganic nanoparticles in polymers in supercritical fluids. Moreover, an important part of this work has concerned the synthesis of aluminum nanoparticles in supercritical fluids in order to incorporate them in polymer matrixes for applications to propellants.

Submitted by UILIAN GABALDI YONEZAWA null (uilian_yonezawa@yahoo.com.br) on 2016-05-16T21:16:30Z No. of bitstreams: 1 dissertação Final.pdf: 3612402 bytes, checksum: b582b0fd2450b9deae8e2a4e625add5a (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-05-17T18:33:33Z (GMT) No. of bitstreams: 1 yonezawa_ug_me_ilha.pdf: 3612402 bytes, checksum: b582b0fd2450b9deae8e2a4e625add5a (MD5) / Made available in DSpace on 2016-05-17T18:33:33Z (GMT). No. of bitstreams: 1 yonezawa_ug_me_ilha.pdf: 3612402 bytes, checksum: b582b0fd2450b9deae8e2a4e625add5a (MD5) Previous issue date: 2016-03-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os hidrogéis são polímeros hidrorretentores reticulados, que são capazes de reter e absorver grande quantidade de água. A combinação de polissacarídeos e nanoargila na matriz polimérica otimiza o desenvolvimento de materiais biodegradáveis e nanoestruturados que podem ser utilizados na agricultura. Nesta dissertação foram preparados e caracterizados hidrogéis nanoestruturados biodegradáveis, afim de aplicá-lo como um acelerador no crescimento de mudas de hortaliça. Os hidrogéis foram preparados fixando as concentrações de acrilamida (AAm) em 6% m/v e carboximetilcelulose (CMC) em 1% m/v, e incorporando diferentes concentrações de nanoargila cloisita-Na+. Diferentes quantidades de hidrogéis foram incorporadas ao substrato e investigado a sua eficiência no cultivo de alface. Foram analisadas as propriedades hidrofílicas e cinéticas em água destilada e em soluções salinas. Os hidrogéis demonstraram excelentes resultados de intumescimento. A incorporação de nanoargila na matriz do polímero aumentou a velocidade de absorção de água (indicada pelo aumento da constante cinética k) quando intumescido em água destilada. A formação das redes poliméricas foi confirmada pela análise de espectroscopia no infravermelho com transformada de Fourier (FTIR). A difração do raios-x (DRX) e a espectroscopia de energia dispersiva de Raios-X (EDX) permitiu avaliar a conformação das plaquetas de nanoargila e os elementos químicos presente nos nanocompósitos, respectivamente. A microscopia eletrônica de varredura (MEV) demonstrou uma morfologia de estruturas porosas, com formas bem definidas e tamanhos de poros heterogêneos. A análise térmica evidenciou uma estabilidade térmica abaixo de 200 ºC para todas as amostras analisadas. A aplicação do hidrogel como condicionador de solo demonstrou ser eficiente no cultivo de alface, se aplicado na dose ideal. A presença de nanoargila na matriz polimérica melhorou a germinação, o desenvolvimento e a qualidade das mudas testadas. Os resultados demonstram que os nanocompósitos são produtos promissores em meio de cultura que precisam de liberação controlada e de condicionadores de solo. / Hydrogels are water-retainer crosslinked polymers which are able to retain and absorb large quantities of water. The combination of polysaccharides and nanoclay in the polymeric matrix enhanced the development of nanostructured and biodegradable materials and it can be used in agriculture. In this work, nanostructured biodegradable hydrogels was prepared in order to improve germination and seedling quality of lettuce cultivation. The hydrogels were prepared by fixing the concentrations of acrylamide (AAm) in 6% w/v carboxymethylcellulose (CMC) in 1% w/v, containing different nanoclay Cloisite-Na+ concentrations. Different amounts of hydrogel were incorporated to the substrate and investigated their efficiency in lettuce cultivation. Hydrophilic and kinetic properties were investigated in distilled water and in saline solutions. The hydrogels showed excellent swelling degree results. Also, the incorporation of nanoclay in the polymer matrix increased the water absorption speed (indicated by an increase in kinetic constant k) when swollen in distilled water. The formation of polymer networks was confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. The x-ray diffraction (XRD) and energy dispersive spectroscopy X-ray (EDX) corfimed the conformation of the nanoclay platelets and chemical elements present in the nanocomposite, respectively. The scanning electron microscopy (SEM) showed porous structures morphology with well-defined shapes, but with heterogeneity in the size. Thermal analysis showed thermal stability for all samples below 200 °C. The application of hydrogel as a soil conditioner confirmed the efficiency in lettuce cultivation if applied in an optimal dose. The presence of nanoclay in the polymeric matrix enhanced the germination, the development and the quality of the tested seedlings. The results showed that nanocomposites are promising products in a culture medium that need controlled release and soil conditioners.

Made available in DSpace on 2014-12-17T14:07:15Z (GMT). No. of bitstreams: 1 MaraTST_DISSERT.pdf: 2071273 bytes, checksum: 9636b6602dd1a469f78b17d077ba757f (MD5) Previous issue date: 2013-03-04 / In recent decades have seen a sharp growth in the study area of nanoscience and nanotechnology and is included in this area, the study of nanocomposites with self-cleaning properties. Since titanium dioxide (TiO2) has high photocatalytic activity and also antimicrobial, self-cleaning surfaces in your application has been explored. In this study a comparison was made between two synthesis routes to obtain TiO2 nanoparticles by hydrothermal method assisted by microwave. And after analysis of XRD and SEM was considered the best material for use in nanocomposites. It was deposited nanocomposite film of poly (dimethyl siloxane) (PDMS) with 0.5, 1, 1.5 and 2% by weight of nanoparticles of titanium dioxide (TiO2) by the spraying method. The nanocomposite was diluted with hexane and the suspension was deposited onto glass substrate, followed by curing in an oven with forced air circulation. The photocatalytic activity of the nanocomposite impregnated with methylene blue was evaluated by UV- vis spectroscopy from the intensity variation of absorption main peak at 660nm with time of exposure to the UV chamber. Changes in the contact angle and microhardness were analyzed before and after UV aging test. The effect of ultraviolet radiation on the chemical structure of the PDMS matrix was evaluated by spectrophotometry Fourier transform infrared (FTIR).The results indicated that the addition of TiO2 nanoparticles in the coating PDMS gave high photocatalytic activity in the decomposition of methylene blue, an important characteristic for the development of self-cleaning coatings / Nas ?ltimas d?cadas tem-se observado um crescimento acentuado no estudo da ?rea de nanoci?ncia e nanotecnologia em que inclui-se nessa ?rea, o estudo de nanocomp?sitos com propriedades autolimpantes. Desde que o di?xido de tit?nio (TiO2) apresenta alta atividade fotocatal?tica e tamb?m, atividade antimicrobiana, sua aplica??o em superf?cies autolimpantes tem sido amplamente explorada. Neste trabalho foi feito uma compara??o entre duas rotas de s?ntese para obten??o de nanopart?culas de TiO2 pelo m?todo hidrot?rmico assistido por micro-ondas. Ap?s an?lise de DRX e MEV foi analisado o melhor material para aplica??o em nanocomp?sitos. Foram depositados filmes de nanocomp?sito de poli(dimetil siloxano) (PDMS) com 0,5, 1, 1,5 e 2% em massa de nanopart?culas de di?xido de tit?nio (TiO2) pelo m?todo de aspers?o. O nanocomp?sito foi dilu?do em hexano e a suspens?o foi depositada sobre l?minas de vidro, seguida de cura em estufa com circula??o for?ada de ar. A atividade fotocatal?tica do nanocomp?sito impregnado com azul de metileno foi avaliada pela t?cnica de espectroscopia de UV-V?sivel, a partir da varia??o da intensidade de absor??o do pico principal a 660 nm com o tempo de exposi??o em c?mara UV. Altera??es no ?ngulo de contato e na microdureza foram analisadas antes e ap?s o ensaio de envelhecimento UV. O efeito da radia??o ultravioleta na estrutura qu?mica da matriz de PDMS foi avaliado por espectrofotometria no infravermelho por transformada de Fourier (FTIR). Os resultados indicaram que a adi??o das nanopart?culas de TiO2 em PDMS conferiram ao revestimento boa atividade fotocatal?tica na decomposi??o do azul de metileno, caracter?stica importante para o desenvolvimento de revestimentos autolimpantes

Novel solutions to offset thermal degradation of polyamide-6 (PA-6) and organoclay (organically modified layered silicates) nanocomposites during melt compounding have been investigated. In this research, a novel chain extender (Joncryl ADR 3400) has been used to improve thermal stability of PA-6 and PA- 6/organoclay nanocomposites during melt compounding. The materials were compounded using a linear twin extruder and various laboratory scale mixers. The effects of organoclay and chain extender were studied using both processing methods. In order to replicate large scale production used in industry, a comprehensive plan of experimental work was carried out under different processing conditions (extrusion temperature and screw speed), organoclay and chain extender loading using a linear twin screw extruder. Rheology, mechanical and thermal properties were analysed and selected samples were also characterised by TEM and FTIR. Process induced degradation of PA-6 during the melt compounding was found to have significant influence on the rheological and mechanical properties. Rheological and mechanical characterisation clearly showed showed that incorporation of the chain extender minimised thermal degradation of PA-6 and nanocomposites during melt processing. Visual analysis of selected nanocomposites using TEM confirmed that chain extender increased the dispersion of nanoclays in the PA- 6 matrix. The crystallinity of the PA-6 was slightly affected by addition of organoclay and chain extender. The samples obtained by linear twin screw extrusion showed higher rheological properties than the samples from laboratory scale mixers suggesting better mixing and less thermal degradation during extrusion.

Orientador: Luiz Francisco Malmonge / Resumo: Nanocompósitos com matriz de fibras em escala micro e nanométrica de poli(fluoreto de vinilideno) – PVDF com adição de argila montmorilonita ou zeólita faujasita – FAU, nas concentrações de 3%, 5%, 10%, 20% e 30%, foram produzidas pela técnica de fiação por sopro em solução e submetidas a caracterizações morfológica e estrutural (Microscopia Eletrônica de Varredura – MEV, Difratometria de Raios X – DRX e Energia Dispersiva de Raios X – EDX). As análises térmicas foram feitas por Calorimetria Exploratória Diferencial – DSC e Análise Termogravimétrica – TGA; as mecânicas por análises de Tensão – Deformação; e de molhabilidade por Ângulo de Contato. As amostras foram submetidas a testes de remoção de metais pesados através da adsorção em banho e em membrana. Os resultados demonstraram queda da espessura dos nanocompósitos, que passaram de 500 μm do polímero puro, para 251 μm e 315 μm para os nanocompósitos com 30% de argila e FAU, respectivamente. A técnica de MEV evidenciou amostras com grande quantidade de fibras lisas, uniformes, cilíndricas e pouco aglomeradas, cujos diâmetros foram inferiores a 200 nm. A ferramenta de EDX confirmou a presença dos elementos da argila e da FAU dispersos por todo o filme, porém surgem aglomerados com o aumento de sua concentração. A técnica de DRX demonstrou a presença das fases cristalinas α e β da matriz, além disso, o aumento da quantidade de argila e FAU nos nanocompósitos intensificou seus picos característicos. A técnica DSC revelou que ... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Title: Preparation of Nanocomposites TiOx/Plasma Polymer and Study of Their Properties Author: Mgr. Martin Drábik Department: Department of Macromolecular Physics Supervisor: Prof. RNDr. Hynek Biederman, DrSc. Supervisor's e-mail address: bieder@kmf.troja.mff.cuni.cz Abstract: This thesis concerns a study of nanocomposite films TiOx/plasma polymer prepared by various deposition techniques using different organic precursors. Processes of deposition of the films were diagnosed in-situ by means of OES and measuring the deposition rate by QCM. Properties of the nanocomposite films were studied by various characterization techniques. Wettability of the films was described by means of the contact angle of water. Morphology of the nanocomposites was characterized by AFM, TEM and SEM. Elemental analysis and chemical composition of the films were studied by XPS, RBS, SIMS and FTIR. Crystal structure of TiO2 films was identified by XRD. Optical characterization of the prepared films was done by UV-Vis spectroscopy. Electrical properties of the samples were characterized by I-V and SPV measurements. In the end, 'wet' chemical processes were utilized for preparation of both TiO2 nanostructures and organic films for comparison with vacuum deposition techniques and plasma polymer composite films. Keywords: nanocomposite...

Title: XPS analysis of plasma polymers and nanocomposite films without breaking vacuum Author: Anna Artemenko Institute: Charles University in Prague, Department of Macromolecular Physics Supervisor of the doctoral thesis: Prof. RNDr. Hynek Biederman, DrSc., Charles University in Prague, Department of Macromolecular Physics. Abstract: Plasma polymers and metal/ plasma polymer nanocomposites have been widely used for various biomedical proposes. Naturally, surface properties of the coatings such as high wettability, stability on the open air and in aqueous media, resistance towards different sterilization processes and cells adhesion are required for bioapplications. This thesis is mainly dedicated to the investigation of chemical composition of deposited coatings using XPS analysis. Nylon-like plasma polymer, PEO-like coatings, fluorocarbon plasma polymer (PTFE) films and Au/PEO-like, Ag/C:H, Al/C:H nanocomposites were chosen as the subject material. In addition, results of XPS measurements were used for the computer simulation for calculation of filling factor of metal/ plasma polymer nanocomposites. These results were in a good agreement with experimental data. Keywords: plasma polymer, nanocomposite, XPS analysis, bioapplication, simulation.