An experimental investigation was undertaken to determine the effects of marine environmental exposure on the mechanical properties of vinylester resins (VE510A and VE8084) and carbon fiber/VE510A vinylester composites. The effect of carbon fiber sizing on the composite strengths was also examined. Neat resins were exposed to marine environments until moisture content reached a point of saturation after which they were tested in tension, compression and shear. Compared to the baseline dry specimens, specimens subjected to moisture showed overall increased ductility and a reduction in strength. Dry and moisture saturated composite specimens were tested in tension and compression in different orientations. Longitudinal specimens were tested in in-plane shear and interlaminar shear. Composites with F-sized carbon fibers displayed overall higher strength than those with G-sized fibers at both dry and moisture saturated conditions. An analysis of moisture absorption of the composites was performed which vii shows that the moisture up-take is dominated by the fiber/matrix region which absorbs up to 90% of the moisture. The composites experienced reduced strength after moisture absorption. The results revealed that the fiber sizing has stronger effect on the fiber/matrix interface dominated strengths than moisture up-take. / by Alexander M. Figlionini. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

Durability of the composite materials in marine environments has been investigated experimentally and with analytical and numerical methods. The main focus of this study is on the integrity of the fiber/matrix interface under seawater exposure. A single-fiber compression test specimen called the Outwater-Murphy (OM) test has been analyzed using mechanics of materials principles and linear elastic fracture mechanics. Sizing of the OM specimen was conducted so that debonding of the fiber from the interface should be achieved prior to yielding of the matrix and global instability failure. Stress analysis of the OM specimen has been conducted from theory of elasticity and finite element analysis. A superelement technique was developed for detailed analysis of the stress state at the fiber/matrix interface. The interface stress state at the debond site in the OM specimen, i.e. at the hole edge, was identified as biaxial tension at the fiber/matrix interface. Characterization of cure and post-cure of 8084 and 510A vinlyester resins has been performed using cure shrinkage tests based on dynamic mechanical analysis and coated beam experiments. In addition, moisture absorption, swelling and the influence of moisture on the mechanical properties of the resins were determined. Testing of OM specimens consisting of a single carbon or glass fiber embedded in vinylester resin at dry conditions and after seawater exposure revealed that the debond toughness was substantially reduced after exposure of the OM specimen to seawater. C(F) did not debond. Macroscopic carbon/vinylester woven composites where the fibers were sized with F sizing were tested in shear at dry conditions and after four weeks of seawater exposure. The shear strength was very little affected after the short immersion time. / by Muhammad Umar Farooq. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

O objetivo deste trabalho é verificar como a arte e a moda, representam o cotidiano no contemporâneo, principalmente no que diz respeito à crítica ao sistema vigente, a representação do instante formador do cotidiano e da apropriação da arte pelo consumo. Por necessidade de um recorte metodológico as Artes de Muro também conhecidas como Grafites foram escolhidas como fenômeno de observação por ser uma arte pública e de fácil acesso a maioria dos indivíduos que interagem com o espaço urbano. Observa-se que embora a Arte de Muro seja em sua maioria uma crítica aos moldes impostos pelo sistema, ela acaba por ser aglutinada por ele e transformada em bens de consumo de alto valor. / The objective of this work is to see how art and fashion, represent the everyday in contemporary, especially with regard to the criticism of the current system, the representation of time trainer every day and appropriation of art by consumption. On the need for a methodological approach for the Arts also known as Wall Graffiti were chosen as a phenomenon of observation to be a public and easily accessible to most individuals who interact with the urban space art. It is observed that although the Art Wall is mostly a critique of the molds imposed by the system, it turns out to be bonded by it and transformed into consume high value goods.

"The temperature dependence of the contact angle of water on graphite, silicon and gold was investigated under various conditions to test the Sharp-Kink Approximation. Despite correctly predicting the contact angle at room temperature, the ideal Sharp-Kink Approximation was not found to accurately describe the contact angle's temperature dependence. The discrepancies from the predicted contact angle were characterized in terms of a correction H(T) to the liquid-solid surface tension. H(T) was found to be linear in temperature and decreasing, and is consistent with electrostatic charge effects."

Monolithic composites are needed that combine low friction and wear, high mechanical hardness, and high fracture toughness. Thin films and coatings are often unable to meet this engineering challenge as they can delaminate and fracture during operation ceasing to provide beneficial properties during service life. Two material systems were synthesized by spark plasma sintering (SPS) and were studied for their ability to meet these criteria. A dual hybrid composite was fabricated and consisted of a nickel matrix for fracture toughness, TiC for hardness and graphite for solid/self‐lubrication. An in‐situ reaction during processing resulted in the formation of TiC from elemental Ti and C powders. The composition was varied to determine its effects on tribological behavior. Stellite 21, a cobalt‐chrome‐molybdenum alloy, was also produced by SPS. Stellite 21 has low stacking fault energy and a hexagonal phase which forms during sliding that both contribute to low interfacial shear and friction. Samples were investigated by x‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x‐ray spectroscopy (EDS), and electron back‐scattered diffraction (EBSD). Tribological properties were characterized by pin on disc tribometry and wear rates were determined by profilometry and abrasion testing. Solid/self‐lubrication in the TiC/C/Ni system was investigated by Raman and Auger mapping. A tribofilm, which undergoes a stress‐induced phase transformation from polycrystalline graphite to amorphous carbon, was formed during sliding in the TiC/C/Ni system that is responsible for low friction and wear. TiC additions help to further decrease wear. Stellite 21 was also found to exhibit acceptably low friction and wear properties arising from the presence of Cr23C6 in the matrix and work hardening of the cobalt and chromium during sliding.

In this dissertation, I report my thesis work on studying surface electron dynamics for intercalated graphene on a metal template using both experimental and theoretical methods. A general description of the research motivation is summarized in the first Chapter. The experimental and theoretical techniques involved in this thesis research are introduced in Chapter 2. In Chapter 3 and Chapter 4, the key findings of this thesis work are reported. These findings concern two novel surface electronic phenomena in oxygen intercalated-graphene on Ir(111) interface. The first phenomenon was the observation of strongly excited image potential states (IPS) in a well-defined quasi-free-standing graphene (QFG) at an oxygen-intercalated Gr/Ir interface. Specifically, the interfaces were synthesized to form Gr/Ir and QFG (Gr/O/Ir) by oxygen intercalation. The syntheses were monitored by low-energy-electron-diffraction (LEED). Our research succeeded in exciting and measuring IPSs on both interfaces by angle-resolved two-photon-photoemission (AR-2PPE) and then the increasing of the IPS binding energy of 0.17 eV following the oxygen intercalation. Finally, our work proposed a theoretical model based on density-functional-theory (DFT) calculations and effective potential models to simulate the surface potential variations in the presence of the intercalated oxygen and its influence on IPSs. The energy shift could be understood by an approximation considering only the out-of-plane chemical and structural modulations. In addition, the results of the model are in strong agreement with the measured IPS band structures. The agreement enables us to attribute the IPS binding energy shift to two potential modulations: a deepened and widened interfacial potential well due to the presence of oxygen intercalants and an increased graphene-Ir interlayer distance. The second phenomenon investigated was a non-dispersive unoccupied band at the Brillouin Zone (BZ) center, which was observed only for Gr/O/Ir but not for Gr/Ir interface. The unoccupied state is approximately 2.6 eV above Fermi energy and was discovered by AR-2PPE. The existence of the non-dispersive band inspired us to undertake a careful examination of the in-plane structural modulation induced by oxygen intercalants. LEED measurements confirm the presence of an in-plane 2$\times$2 periodicity of the intercalated oxygen in QFG. This periodicity can provide periodic perturbation to QFG and can generate the flat unoccupied state due to zone-folding effects from the BZ edge. Angle-resolved photoemission measurements and DFT-based calculations were used to compare the measured Gr/O/Ir states to that of Gr/Ir and O/Ir, providing solid evidence for this zone-folding interpretation. The realization of mixing bands between high symmetry points in BZ by zone-folding in Gr/O/Ir demonstrates a pathway for engineering the graphene electronic structure and its two-photon optical excitation via other ordered intercalants. In addition, a separate but related collaboration work on the phase-transition and electronic-structure evolution in W-doped \ce{MoTe2} is documented in Chapter 5. In this work, I contributed expertise in photoemission to study the critical dopant stoichiometry responsible for the phase transition.

Graphite and graphene electrodes are used to study two electrochemical processes: the decoration of these electrodes with Au metallic nanoparticles through the use of electrodeposition, and electrowetting, the potential-dependent change in hydrophobicity of a surface. Electrodeposition provides a useful route to electrode functionalisation, in particular to combine the enhanced properties of metallic nanoparticles with the advantageous features of carbon materials. A combination of cyclic voltammetry, chronoamperometry, and both ex situ and in situ atomic force microscopy are used to deduce the mechanism of Au electrodeposition on graphite and graphene. Notably, the mechanism of Au nanoparticle formation cannot be deduced from simple voltammetry alone, and the spontaneous formation of Au within the timescale of the electrodeposition experiment is confirmed. Electrowetting is a uniquely responsive method to manipulate the wetting properties of an electrode. However, a dielectric coating is commonly required to protect the surface from electrolysis, which in turn further increases the potentials needed to perform electrowetting. In contrast to this, here it is shown that bare graphite and graphene electrodes support electrowetting without the disadvantages of a dielectric coating, allowing an unprecedented combination of performance and efficiency. Furthermore, the ideal behaviour this system demonstrates is implemented as a platform to study electrowetting itself. The influence of electrolyte composition, surface defects and electrode-blocking dielectric-like films are investigated to determine the factors that impede electrowetting, a key step to understanding the phenomenon that is normally hindered by the use of the dielectric.

In this research, the degradation of carbon fiber/vinylester composites in marine environments was experimentally investigated. Additionally, two types of carbon fiber surface treatments, namely Polyhedral Oligomeric Silsesquioxane (POSS) and the industrial surface treatment F0E, were evaluated to determine their effectiveness in creating a fiber/matrix (F/M) interface for use in the marine environment. Electrochemical Impedance Spectroscopy (EIS) was explored as a new application of an existing technique for use in measuring the amount of water at the F/M interface in carbon fiber/vinylester composites. EIS spectra were used to determine equivalent electric circuit models that allow for the prediction of water at the interface. The location of water within the composite was determined through Positron Annihilation Lifetime Spectroscopy (PALS). Interlaminar shear strength and transverse tensile tests were carried out for dry conditions and after hygrothermal exposure of the composites to study the influence of the integrity of the F/M interface on the macroscopic response of the composite. / by Chris J. Vinci. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Orientador: Maria Isabel Felisberti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-09-27T12:42:23Z (GMT). No. of bitstreams: 1 Nogueira_HeltonPereira_M.pdf: 2762504 bytes, checksum: 2a6c093233b2870f10da6a8408841655 (MD5) Previous issue date: 2012 / Resumo: As cargas de carbono, tais como grafite, nanotubos de carbono, fulerenos e mais recentemente o grafite tem atraído a atenção de inúmeros pesquisadores, que buscam formas de aproveitar suas excepcionais propriedades elétricas no desenvolvimento de compósitos com potenciais aplicações nas áreas de sensores eletroquímicos, células solares, barreira eletromagnética entre outras. Neste trabalho teve-se como objetivo o desenvolvimento de compósitos baseados em poli(estireno-co-butadieno-co-estireno) ¿ SBS e as cargas de carbono, grafite e grafite. Para tanto, o grafite foi obtido pela oxidação do grafite empregando-se a metodologia de Hummers, seguida de redução por hidrazina. Os compósitos de grafite e "grafite¿ foram preparados por mistura mecânica e por casting de soluções em diferentes solventes na faixa de composição de 0,5 a 10 % em massa de carga. O processamento mecânico resultou em compósitos que apresentaram comportamento mecânico dependente do tipo e quantidade de carga. Porém, esses compósitos apresentaram-se como isolantes elétricos devido a não formação de uma rede de percolação. A matriz de SBS nos compósitos obtidos por casting apresentou morfologia dependente do solvente empregado, o que se deve aos parâmetros de solubilidade dos solventes e dos blocos de poliestireno e polibutadieno do SBS, e a dispersão da carga pela matriz foi mais uniforme do que no caso de compósitos preparados por mistura mecânica, promovendo uma melhora nas propriedades mecânicas e conferindo propriedades de condução elétrica / Abstract: Carbon fillers such as graphite, carbon nanotubes, fullerenes and currently graphene have attracted the attention of many researchers, due to their exceptional and useful electrical properties for the development of composites with potential applications in electrochemical sensors, solar cells, electromagnetic barrier, and so on. The objective of the herewith work is the development of composites made up of poly(styrene-co-butadiene-co-styrene) ¿ SBS and carbon fillers (graphite or graphene). The graphene was obtained by oxidation of the graphite by the Hummers¿ method, followed by hydrazine¿s reduction. The graphite and graphene - based composites were prepared by melt compounding and by solvent casting using different organic solvents in a composition range of 0,5 to 10% in weight of filler. The results showed that the melt compounding produced composites with mechanical properties dependent on the type and amount of filler. Also, these composites behave as electrical insulators due to the absence of percolation thresholds. The morphology of SBS matrix in the composites obtained by solvent casting is determined by the organic solvent, more specifically by the interaction paramenter of solvent and of the polybutadiene and polystyrene blocks of the SBS. The filler dispersion throughout the matrix in the composites obtained by solvent-casting was more uniform than the dispersion level in the composites obtained by melt compounding. Therefore, the first materials showed higher mechanical performance and electrical conducting / Mestrado / Físico-Química / Mestre em Química

This study presents a simple way of obtaining hydrogen gas (H2) from various ranks of coal, coke, and graphite using nanosecond laser pulses. Powder samples of coal and graphite with and without water were irradiated with 1064 nm and 532 nm pulses from an Nd: YAG laser for 45 minutes under air and argon atmospheres. It was observed that 532 nm laser pulses were more effective than 1064 nm pulses in gas generation and both were nonlinearly correlated with respect to the laser energy density. Mainly hydrogen (H2) and carbon monoxide (CO) were observed. The H2 to CO ratio shows that the highest efficiency rank was the anthracite coal, with an average ratio of 1.4 due to its high fixedcarbon content and relatively high hydrocarbon amount. Coal samples were characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analyzer (TGA), and calorimeter. Graphite was used as a pure carbon source to study the possible reactions of gas yielded during irradiation process. The amount of H2 produced was negligible when graphite powder was exposed under the air and argon atmospheres. On the other hand, H2 was obtained from irradiation of graphite powder in the presence of water due to a possible carbon-water reaction. When coal powders were irradiated under air and argon atmosphere, the amount of produced H2 increased drastically compared to graphite due to the presence of hydrocarbons in coal. In addition, theoretical simulations by a standard finite difference method supported experimental observations.