This thesis aims to fabricate the high performance Magnesium/Carbon-Fiber/PEEK five-layer hybrid nanocomposite laminates. The adopted Mg thin sheets are 0.5mm thick. The Carbon-Fiber/PEEK prepregs were stacked into two lay-ups, such as cross-ply [0/90]s and quasi-isotropic [0/45/90/-45], with the adding of nanoparticles SiO2 spreaded among the laminates. After etching of Mg foils by CrO3-base etchants, a five-layered Mg/Carbon-Fiber/PEEK nanocomposite laminate was made according to the modified diaphragm curing process. Then, the mechanical properties, such as stress-strain curve, strength and stiffness were obtained by tensile test at room temperature (25¢J), 50, 75, 100, 125 and 150¢J and the fatigue properties were also obtained under constant stress amplitude tension-tension cyclic loading elevated at room and elevated temperatures 25, 75, 100, 125 and 150¢J. Finally, the Mg sheets and fractured laminates were observed by the SEM and OM. The results according to the experiments were summarized as follows: 1.The slope of stress-strain curve dropped at strain¡Ü0.0015. It can be inferred that fracture occurred in the laminates at this time. Stiffness approached the theoretical value by curve fitting with the strain range of 0 to 0.0015. 2.The mechanical properties decreased with the environmental temperature rise. 3.The resistance to the temperature effect of the quasi-isotropic Magnesium/Carbon-Fiber/PEEK laminate is superior to that of the cross-ply Magnesium/Carbon-Fiber/PEEK laminate. 4.The cross-ply Magnesium/Carbon-Fiber/PEEK laminate is brittler than that of the quasi-isotropic laminate generally. 5.The irregular bright lines were found in the third etched Mg sheet and that resulted in the delamination of Mg sheet after treatment. The unetched part maybe the defect of Mg sheet. 6. It was found that AZ31 has the precipitation hardening effect at 50¢J and 75¢J.

Este trabalho aborda o estudo do comportamento mecânico e térmico do nanocompósito híbrido de polipropileno com uma argila brasileira bentonítica do Estado da Paraíba (PB), conhecida como \"chocolate\" com concentração de 1, 2 e 5 % em massa com a adição de 1 e 2 % em massa de celulose proveniente de papel descartado. Foi utilizado nesse nanocompósito o agente compatibilizante polipropileno graftizado com anidrido maleico PP-g-AM com 3 % de concentração em massa, através da técnica de intercalação do fundido utilizando uma extrusora de dupla-rosca e, em seguida, os corpos de prova foram confeccionados em uma injetora. O comportamento mecânico foi avaliado pelos ensaios de tração, flexão e impacto. O comportamento térmico foi avaliado pelas técnicas de calorimetria exploratória diferencial (DSC) e termogravimetria (TGA). A morfologia dos nanocompósitos foi estudada pela técnica de microscopia eletrônica de varredura (MEV). A argila, a celulose e os nanocompósitos híbridos foram caracterizados por difração de raios X (DRX), fluorescência de raios X (FRX) e espectroscopia no infravermelho (FTIR). Nos ensaios mecânicos de tração houve um aumento de 11 % na tensão máxima em tração e 15 % no módulo de Young, para o nanocompósito com argila, PPA 5 %. No ensaio de impacto Izod, o nanocompósito com argila, PPA 2 % obteve um aumento de 63 % na resistência ao impacto. Para o nanocompósito híbrido PPAC 1 % houve aumento de 8 % na tensão máxima em tração e para o nanocompósito híbrido PPAC 2 % houve aumento de 14 % na resistência ao impacto. / This work concerns to the study of the mechanical and thermal behavior of the hybrid polypropylene nanocomposite with a Brazilian bentonite clay from State of Paraíba (PB), known as \"Chocolate\" in concentrations of 1, 2 and 5 % by weight with addition of 1 and 2 % in weight cellulose discarded bond paper. The compatibilizer agent based on maleic anhydride grafted polypropylene, known as PP-g-MA, was added at 3 % weight concentration through the melt intercalation technique using a twin-screw extruder, and afterwards, the specimens were prepared by injection process. The mechanical behavior was evaluated by strength, flexural strength and impact tests. The thermal behavior was evaluated by the differential scanning calorimetry (DSC) and thermogravimetry (TGA). The morphology of the nanocomposites was studied by the technique of scanning electron microscopy (SEM). The clay, cellulose and the hybrid nanocomposites were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and infrared spectroscopy (FTIR). Results of mechanical tests showed an 11 % and 14 % increase in the tensile strength and Young\'s modulus, respectively, for the nanocomposite PPA 5 % with clay. The nanocomposite PPA 2 % with clay obtained a 63 % increase in strength Izod impact test. The hybrid nanocomposite PPAC 1 % obtained an 8 % increase in tensile strength. In the Izod impact test, the hybrid nanocomposite PPAC 2 % obtained 14 % increased in the impact strength.

<p>The ability to detect infrared radiation is vital for a host of applications that include optical communication, medical diagnosis, thermal imaging, atmospheric monitoring, and space science. The need to actively cool infrared photon detectors increases their operation cost and weight, and the focus of much recent research has been to limit the dark current and create room-temperature infrared photodetectors appropriate for mid-to-long-wave infrared detection. Quantum dot infrared photodetectors (QDIPs) provide electron quantum confinement in three dimensions and have been shown to demonstrate high temperature operation (T>150 K) due to lower dark currents. However, these inorganic devices have not achieved sensitivity comparable to state-of-the-art photon detectors, due in large part to the inability to control the uniformity (size and shape) of QDs during strained-layer epitaxy.</p><p>The purpose of this dissertation research was to investigate the feasibility of room-temperature infrared photodetection that could overcome the shortfalls of QDIPs by using chemically synthesized inorganic colloidal quantum dots (CQDs). CQDs are coated with organic molecules known as surface ligands that prevent the agglomeration of dots while in solution. When CQDs are suspended in a semiconducting organic polymer, these materials are known as organic/inorganic hybrid nanocomposites. The novel approach investigated in this work was to use intraband transitions in the conduction band of the polymer-embedded CQD for room-temperature photodetection in the mid-wave, and possibly long-wave, infrared ranges. Hybrid nanocomposite materials promise room-temperature operation due to: (i) large bandgaps of the inorganic CQDs and the semiconducting polymer that reduce thermionic emission; and (ii) low dark current due to the three-dimensional electron confinement in the CQD and low carrier mobility in the semiconducting polymer. The primary material system investigated in this research was CdSe CQDs embedded in the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-(1-cyanovinylene)phenylene] (MEH-CN-PPV). </p><p>Photoluminescence (PL) spectroscopy of MEH-CN-PPV thin films was conducted to determine the dependence of polymer morphology on deposition method in order to identify a reliable device fabrication technique. Three different deposition methods were investigated: drop-casting and spin-casting, which are solution-based; and matrix-assisted pulsed laser evaporation (MAPLE), which is a vacuum-based method that gently evaporates polymers (or hybrid nanocomposites) and limits substrate exposure to solvents. It was found that MAPLE deposition provides repeatable control of the thin film morphology and thickness, which is important for nanocomposite device optimization. </p><p>Ultra-fast PL spectroscopy of MEH-CN-PPV/CdSe thin films was investigated to determine the charge generation and relaxation dynamics in the hybrid nanocomposite thin films. The mathematical fitting of time-integrated and time-resolved PL provided a rigorous and unique model of the charge dynamics, which enabled calculation of the radiative and non-radiative decay lifetimes in the polymer and CQD. These results imply that long-lived electrons exist in the conduction band of the CQD, which demonstrate that it should be possible to generate a mid- to long-wave infrared photocurrent based on intraband transitions. In fact, room-temperature, intraband, mid-infrared absorption was measured in thin films of MEH-CN-PPV/CdSe hybrid nanocomposites by Fourier transform infrared (FTIR) absorbance spectroscopy. In addition, the hybrid nanocomposite confined energy levels and corresponding oscillator strengths were calculated in order to model the absorption spectrum. The calculated absorption peaks agree well with the measured peaks, demonstrating that the developed computer model provides a useful design tool for determining the impact of important materials system properties, such as CQD size, organic surface ligand material choice, and conduction band offset due to differences in CQD and polymer electron affinities.</p><p>Finally, a room-temperature, two terminal, hybrid nanocomposite mid-infrared photoconductor based on intraband transitions was demonstrated by FTIR spectral response measurements, measuring a spectral responsivity peak of 4.32 µA/W at 5.5µm (5 volts), and calibrated blackbody spectral photocurrent measurements, measuring a spectral responsivity peak of 4.79 µA/W at 5.7 µm (22 volts). This device characterization demonstrated that while the novel approach of intraband infrared photodetection in hybrid nanocomposites is feasible, significant challenges exist related to device fabrication and operation. Future work is proposed that could address some of these important issues.</p> / Dissertation

Este trabalho aborda o estudo do comportamento mecânico e térmico do nanocompósito híbrido de polipropileno com uma argila brasileira bentonítica do Estado da Paraíba (PB), conhecida como \"chocolate\" com concentração de 1, 2 e 5 % em massa com a adição de 1 e 2 % em massa de celulose proveniente de papel descartado. Foi utilizado nesse nanocompósito o agente compatibilizante polipropileno graftizado com anidrido maleico PP-g-AM com 3 % de concentração em massa, através da técnica de intercalação do fundido utilizando uma extrusora de dupla-rosca e, em seguida, os corpos de prova foram confeccionados em uma injetora. O comportamento mecânico foi avaliado pelos ensaios de tração, flexão e impacto. O comportamento térmico foi avaliado pelas técnicas de calorimetria exploratória diferencial (DSC) e termogravimetria (TGA). A morfologia dos nanocompósitos foi estudada pela técnica de microscopia eletrônica de varredura (MEV). A argila, a celulose e os nanocompósitos híbridos foram caracterizados por difração de raios X (DRX), fluorescência de raios X (FRX) e espectroscopia no infravermelho (FTIR). Nos ensaios mecânicos de tração houve um aumento de 11 % na tensão máxima em tração e 15 % no módulo de Young, para o nanocompósito com argila, PPA 5 %. No ensaio de impacto Izod, o nanocompósito com argila, PPA 2 % obteve um aumento de 63 % na resistência ao impacto. Para o nanocompósito híbrido PPAC 1 % houve aumento de 8 % na tensão máxima em tração e para o nanocompósito híbrido PPAC 2 % houve aumento de 14 % na resistência ao impacto. / This work concerns to the study of the mechanical and thermal behavior of the hybrid polypropylene nanocomposite with a Brazilian bentonite clay from State of Paraíba (PB), known as \"Chocolate\" in concentrations of 1, 2 and 5 % by weight with addition of 1 and 2 % in weight cellulose discarded bond paper. The compatibilizer agent based on maleic anhydride grafted polypropylene, known as PP-g-MA, was added at 3 % weight concentration through the melt intercalation technique using a twin-screw extruder, and afterwards, the specimens were prepared by injection process. The mechanical behavior was evaluated by strength, flexural strength and impact tests. The thermal behavior was evaluated by the differential scanning calorimetry (DSC) and thermogravimetry (TGA). The morphology of the nanocomposites was studied by the technique of scanning electron microscopy (SEM). The clay, cellulose and the hybrid nanocomposites were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and infrared spectroscopy (FTIR). Results of mechanical tests showed an 11 % and 14 % increase in the tensile strength and Young\'s modulus, respectively, for the nanocomposite PPA 5 % with clay. The nanocomposite PPA 2 % with clay obtained a 63 % increase in strength Izod impact test. The hybrid nanocomposite PPAC 1 % obtained an 8 % increase in tensile strength. In the Izod impact test, the hybrid nanocomposite PPAC 2 % obtained 14 % increased in the impact strength.

The work presented in this thesis can be divided into two research areas. First, two sets of organic-inorganic hybrid nanocomposites containing phenolic resin/trisilanolphenyl-POSS and phenolic resin/octa(aminophenyl)-T8-POSS nanocomposites were synthesized and the morphology and properties were investigated. Octa(aminophenyl)-T8-polyhedral silsesquioxane is an octafunctional-T8-POSS containing eight aniline-like amino groups, one on each corner silicon atom. It was synthesized in our laboratory by an improved two-step reaction sequence; nitration (HNO3) and reduction (HCOOH/Et3N). Varying amounts of POSS were codissolved with a resole phenolic resin in organic solvent. This was followed by solvent removal and thermal curing. Intermolecular interactions in these nanocomposites were probed by FT-IR. The micro-morphology and aggregation state of POSS were investigated using SEM, TEM, and WAXD studies. The thermal and mechanical properties and thermal stabilities of these composites were investigated by DMTA, DSC, and TGA. Second, two types of carbon-covered mono- and bimetallic (Sn, and Sn/Sb alloy) nanorods for use as anode materials in lithium ion batteries were synthesized by a thermal chemical vapor deposition method. Commercial antimony and tin oxide (Sb3O4/SnO2) nanopowders and added tin (IV) oxide (SnO2) nanoparticles (~19 nm) were used as the precursors for the growth of bimetallic Sn/Sb alloy and monometallic Sn nanorods, respectively. In addition, the shape of the products recovered were different when different hydrocarbon gas flow rates were used for growing intermetallic nanorods in carbon templates. Acetylene and methane were the gases tried. The morphologies and structures of the intermetallic nanorods in carbon templates were investigated using SEM and TEM and proved by X-EDS, XRD, and XPS studies.

The ultra high barrier films for packaging find applications in a wide variety of areas where moisture and oxygen barrier is required for improved shelf-life of food/beverage products and for microbial free pharmaceutical containers. These materials also find applications in micro electro mechanical systems such as ICs, and for packaging in industrial and space electronics. Flexible and portable organic electronics like OLEDs (Organic Light Emitting Diodes), OPVDs (Organic Photo Voltaic Devices) and dye sensitized solar cells (DSSCs) have a good potential in next generation solar powered devices. In fact, organic insulators, semiconductors, and metals may be a large part of the future of electronics. However, these classes of materials are just an emerging class of materials mainly because of their life time constraints. Thus significant research is required to bring them into the forefront of electronic applications. If the degradation problems can be diminished, then these polymers could play a major role in the worldwide electronic industry. A flexible polymer film itself cannot be used as an encapsulation material owing to its high permeability. While a glass or metal substrate possesses ultra high barrier properties, it cannot be used in many electronic applications due to its brittleness and inflexibility. Polymer/ nanocomposites based hybrid materials are thus a promising class of material that can be used for device encapsulation. Chapter I summarizes some of the recent developments in the polymer/nanocomposites based materials for packaging and specifically its use in flexible as well as portable organic electronic device encapsulation. While the development of low permeable encapsulant materials is a chemistry problem, an engineering/instrumentation problem is the development of an accurate technique that can measure the low levels of permeability required for electronic application. Therefore, there is a keen interest in the development of an instrument to measure permeability at these limits. The existing techniques to measure the low permeabilities of barrier films, their importance and accuracy of measurements obtained by these instruments have been briefly discussed in this chapter. Different polymer based hybrid composite materials have been developed for the encapsulation of organic devices and their materials properties have been evaluated. Broadly, two diverse strategies have been used for the fabrication of the composites: in-situ curing and solution casting. Chapters II, III and IV discuss the fabrication of nanocomposite films based on in-situ curing while chapter V discusses fabrication based on solution casting. In chapter II, amine functionalized alumina was used as a cross-linking agent and reinforcing material for the polymer matrix in order to fabricate the composites to be used for encapsulation of devices. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to elucidate the surface chemistry. Thermogravimetric and CHN analysis were used to quantify the grafting density of amine groups over the surface of the nanoparticles. Mechanical characterizations of the composites with various loadings were carried out with dynamic mechanical analyzer (DMA). It was observed that the composites have good thermal stability and mechanical flexibility, which are important for an encapsulant. The morphology of the composites was evaluated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The work presented in chapter III is a technique based on grafting between surface decorated γ-alumina nanoparticles and the polymer to make these nanocomposites. Alumina was functionalized with allyltrimethoxysilane and used to conjugate polymer molecules (hydride terminated polydimethylsiloxane) through platinum catalyzed hydrosilylation reaction. As in the previous chapter, the surface chemistry of the nanoparticles after surface modification was characterized by different techniques (FTIR, XPS and Raman). The grafting density of alkene groups over the surface of the modified nanoparticles was calculated using CHN analyzer. Thermal stability of the composites was also evaluated using thermogravimetric analysis. Nanoindentation technique was used to analyze the mechanical characteristics of the composites. The densities of the composites were evaluated using density gradient column and the morphology of composites was evaluated using SEM. All these studies reveal that the composites have good thermal stability and mechanical flexibility and thus can be potentially used for encapsulation of organic photovoltaic devices. In addition, rheological studies of the composites were carried out to investigate the curing reaction. The platinum-catalyzed hydrosilylation reaction was studied using both DSC and rheological measurements. The competitive reactions occurring in the system was also monitored in real time through DSC and rheology. Based on the curing curves obtained from these two studies, the mechanistic detail of the curing process was proposed. In addition, swelling studies and contact angle measurements of the composites were also carried out to determine the capability of these materials as encapsulants. Chapter IV deals with a thermally stable and flexible composite that has been synthesized by following a hydrosilylation coupling between silicone polymer containing internal hydrides and mesoporous silica. The results of the characterization of the composites indicates that the composites are thermally stable, hydrophobic, flexible and can be potentially used for encapsulating flexible electronic devices. Chapter V discusses the solution casting method for the development of composites. This chapter is divided into two parts: Part I discusses the synthesis and characterization of flexible and thermally stable composites using polyvinyl alcohol as the base polymer matrix and reactive zinc oxide nanoparticles as the dispersed phase. Various studies like thermal analysis, mechanical analysis, surface analysis and permeability studies were used to characterize the composite films for their possible use as a passivation material. The material was used to encapsulate Schottky structured devices and the performance of these encapsulated devices under accelerated weathering was studied. Part II of this chapter discusses the fabrication of hybrid organic/inorganic based polymer-composite films, based on polyvinylbutyral (PVB) and organically modified mesoporous silica. PVB and amine functionalized mesoporous silica were used to synthesize the composite. An additional polyol (‘tripentaerythritol’) component was also used to enhance the –OH group content in the composite matrix. The thermal, barrier and mechanical properties of these composites were investigated. The investigation of these films suggests that these can be used as a moisture barrier layer for encapsulation. Chapter VI gives the concluding remarks of the results presented. The advantages as well as disadvantages of the in-situ cured and solution casted films and the scope for future work is discussed in this chapter.