Academic literature on the topic 'Graphene Oxide - Polymer Hybrid Systems'
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Journal articles on the topic "Graphene Oxide - Polymer Hybrid Systems"
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Plachá, Daniela, Alexandra Muñoz-Bonilla, Kateřina Škrlová, Coro Echeverria, Alberto Chiloeches, Martin Petr, Khalid Lafdi, and Marta Fernández-García. "Antibacterial Character of Cationic Polymers Attached to Carbon-Based Nanomaterials." Nanomaterials 10, no. 6 (June 22, 2020): 1218. http://dx.doi.org/10.3390/nano10061218.
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The preparation of hybrid polymeric systems based on carbon derivatives with a cationic polymer is described. The polymer used is a copolymer of a quaternizable methacrylic monomer with another dopamine-based monomer capable of anchoring to carbon compounds. Graphene oxide and graphene as well as hybrid polymeric systems were widely characterized by infrared, Raman and photoemission X-ray spectroscopies, electron scanning microscopy, zeta potential and thermal degradation. These allowed confirming the attachment of copolymer onto carbonaceous materials. Besides, the antimicrobial activity of hybrid polymeric systems was tested against Gram positive Staphylococcus aureus and Staphylococcus epidermidis and Gram negative Escherichia coli and Pseudomonas aeruginosa bacteria. The results showed the antibacterial character of these hybrid systems.
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Kosowska, Karolina, Patrycja Domalik-Pyzik, Małgorzata Krok-Borkowicz, and Jan Chłopek. "Synthesis and Characterization of Chitosan/Reduced Graphene Oxide Hybrid Composites." Materials 12, no. 13 (June 28, 2019): 2077. http://dx.doi.org/10.3390/ma12132077.
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Graphene family materials (GFM) are currently considered to be one of the most interesting nanomaterials with a wide range of application. They can also be used as modifiers of polymer matrices to develop composite materials with favorable properties. In this study, hybrid nanocomposites based on chitosan (CS) and reduced graphene oxide (rGO) were fabricated for potential use in bone tissue engineering. CS/rGO hydrogels were prepared by simultaneous reduction and composite formation in acetic acid or lactic acid and crosslinked with a natural agent—tannic acid (TAc). A broad spectrum of research methods was applied in order to thoroughly characterize both the components and the composite systems, i.e., X-ray Photoelectron Spectroscopy, X-ray Diffractometry, Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy, Scanning Electron Microscopy, ninhydrin assay, mechanical testing, in vitro degradation and bioactivity study, wettability, and, finally, cytocompatibility. The composites formed through the self-assembly of CS chains and exfoliated rGO sheets. Obtained results allowed also to conclude that the type of solvent used impacts the polymer structure and its ability to interact with rGO sheets and the mechanical properties of the composites. Both rGO and TAc acted as crosslinkers of the polymer chains. This study shows that the developed materials demonstrate the potential for use in bone tissue engineering. The next step should be their detailed biological examinations.
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Arshadi-Rastabi, Shahrzad, Rasoul Sarraf-Mamoory, Ghadir Razaz, Nicklas Blomquist, Jonas Örtegren, and Håkan Olin. "Porous NiMoO4-NrGO as a Battery-Like Electrode Material for Aqueous Hybrid Supercapacitors." Journal of Composites Science 7, no. 6 (May 26, 2023): 217. http://dx.doi.org/10.3390/jcs7060217.
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Recently, much research has investigated nanocomposites and their properties for the development of energy storage systems. Supercapacitor performance is usually enhanced by the use of porous electrode structures, which produce a larger surface area for reaction. In this work, a biocompatible polymer of starch medium was used to create the porous nanostructure. Two powders, i.e., Nickel molybdate/reduced graphene oxide (NiMoO4-rGO) and Nickel molybdate/nitrogen-doped reduced graphene oxide (NiMoO4-NrGO), were synthesized using the deposition method in a medium containing starch, nickel nitrate salts, sodium molybdate, and graphene oxide powder. In terms of electrochemical performance, the NiMoO4-NrGO electrode displayed a higher specific capacitance, i.e., 932 Fg−1 (466 Cg−1), than the NiMoO4-rGO electrode, i.e., 884 Fg−1 (442 Cg−1), at a current density of 1 Ag−1. In fact, graphene oxide sheets could lose more oxygen groups in the presence of ammonia, resulting in increased electrical conductivity. For the asymmetric supercapacitor of NiMoO4-NrGO//AC, the specific capacitance at 1 Ag−1, energy density, and power density were 101.2 Fg−1 (111.32 Cg−1), 17 Wh kg−1, and 174.4 kW kg−1, respectively. In addition, this supercapacitor material displayed a good cycling stability of over 82%.
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Mehrabian, Mohammad Hosein, Shahzad Feizi, and Shahram Moradi Dehaghi. "Cadmium telluride quantum dots/graphene oxide/poly vinyl acetate (CdTe QDs/GO/PVAc) nanocomposite: a novel sensor for real time gamma radiation detection." Radiochimica Acta 108, no. 6 (June 25, 2020): 483–90. http://dx.doi.org/10.1515/ract-2019-3209.
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AbstractThe design of organic/inorganic nanoparticles hybrids provides the great potential for the fabrication of γ-ray sensor systems. Herein, structural and dosimetric properties of the gamma irradiated poly vinyl acetate (PVAc) doped with cadmium telluride quantum dots (CdTe QDs) and graphene oxide (GO) nanoflakes have been investigated. Thioglycolic acid (TGA) capped water-soluble CdTe QDs and (GO) nanoflakes are synthesized and characterized. Then, CdTe QDs/GO/PVAc sensors were formed by post-depositing CdTe and GO over polymer matrix. The photophysical interactions between nanoparticles and organic polymer have been investigated using ohmic contact detectors with two gold coated electrodes. Real time dose rate information of the sensors such as sensitivity, repeatability, and the linearity of dose rate response were assessed. A wider photoelectric response range and wider gamma harvesting range were observed in the resultant hybrid gamma sensor at a standard bias voltage with respect to non-hybrid CdTe QDs/PVAc sensors.
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Madeo, Lorenzo Francesco, Manuela Curcio, Francesca Iemma, Fiore Pasquale Nicoletta, Silke Hampel, and Giuseppe Cirillo. "Release of Bioactive Molecules from Graphene Oxide-Alginate Hybrid Hydrogels: Effect of Crosslinking Method." C 9, no. 1 (January 8, 2023): 8. http://dx.doi.org/10.3390/c9010008.
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To investigate the influence of crosslinking methods on the releasing performance of hybrid hydrogels, we synthesized two systems consisting of Graphene oxide (GO) as a functional element and alginate as polymer counterpart by means of ionic gelation (physical method, HA−GOP) and radical polymerization (chemical method, HA−GOC). Formulations were optimized to maximize the GO content (2.0 and 1.15% for HA−GOP and HA−GOC, respectively) and Curcumin (CUR) was loaded as a model drug at 2.5, 5.0, and 7.5% (by weight). The physico-chemical characterization confirmed the homogeneous incorporation of GO within the polymer network and the enhanced thermal stability of hybrid vs. blank hydrogels. The determination of swelling profiles showed a higher swelling degree for HA−GOC and a marked pH responsivity due to the COOH functionalities. Moreover, the application of external voltages modified the water affinity of HA−GOC, while they accelerated the degradation of HA−GOP due to the disruption of the crosslinking points and the partial dissolution of alginate. The evaluation of release profiles, extensively analysed by the application of semi-empirical mathematical models, showed a sustained release from hybrid hydrogels, and the possibility to modulate the releasing amount and rate by electro-stimulation of HA−GOC.
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Cote, Laura J., Jaemyung Kim, Vincent C. Tung, Jiayan Luo, Franklin Kim, and Jiaxing Huang. "Graphene oxide as surfactant sheets." Pure and Applied Chemistry 83, no. 1 (December 1, 2010): 95–110. http://dx.doi.org/10.1351/pac-con-10-10-25.
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Graphite oxide sheet, now referred to as graphene oxide (GO), is the product of chemical oxidation and exfoliation of graphite powders that was first synthesized over a century ago. Interest in this old material has resurged in recent years, especially after the discovery of graphene, as GO is considered a promising precursor for the bulk production of graphene-based materials. GO sheets are single atomic layers that can readily extend up to tens of microns in lateral dimension. Therefore, their structure bridges the typical length scales of both chemistry and materials science. GO can be viewed as an unconventional type of soft material as it carries the characteristics of polymers, colloids, membranes, and as highlighted in this review, amphiphiles. GO has long been considered hydrophilic due to its excellent water dispersity, however, our recent work revealed that GO sheets are actually amphiphilic with an edge-to-center distribution of hydrophilic and hydrophobic domains. Thus, GO can adhere to interfaces and lower interfacial energy, acting as surfactant. This new property insight helps to better understand GO’s solution properties which can inspire novel material assembly and processing methods such as for fabricating thin films with controllable microstructures and separating GO sheets of different sizes. In addition, GO can be used as a surfactant sheet to emulsify organic solvents with water and disperse insoluble materials such as graphite and carbon nanotubes (CNTs) in water, which opens up opportunities for creating functional hybrid materials of graphene and other π-conjugated systems.
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Madeo, Lorenzo Francesco, Patrizia Sarogni, Giuseppe Cirillo, Orazio Vittorio, Valerio Voliani, Manuela Curcio, Tyler Shai-Hee, Bernd Büchner, Michael Mertig, and Silke Hampel. "Curcumin and Graphene Oxide Incorporated into Alginate Hydrogels as Versatile Devices for the Local Treatment of Squamous Cell Carcinoma." Materials 15, no. 5 (February 22, 2022): 1648. http://dx.doi.org/10.3390/ma15051648.
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With the aim of preparing hybrid hydrogels suitable for use as patches for the local treatment of squamous cell carcinoma (SCC)-affected areas, curcumin (CUR) was loaded onto graphene oxide (GO) nanosheets, which were then blended into an alginate hydrogel that was crosslinked by means of calcium ions. The homogeneous incorporation of GO within the polymer network, which was confirmed through morphological investigations, improved the stability of the hybrid system compared to blank hydrogels. The weight loss in the 100–170 °C temperature range was reduced from 30% to 20%, and the degradation of alginate chains shifted to higher temperatures. Moreover, GO enhanced the stability in water media by counteracting the de-crosslinking process of the polymer network. Cell viability assays showed that the loading of CUR (2.5% and 5% by weight) was able to reduce the intrinsic toxicity of GO towards healthy cells, while higher amounts were ineffective due to the antioxidant/prooxidant paradox. Interestingly, the CUR-loaded systems were found to possess a strong cytotoxic effect in SCC cancer cells, and the sustained CUR release (~50% after 96 h) allowed long-term anticancer efficiency to be hypothesized.
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Sajjan, Kiran, Nehad Ali Shah, N. Ameer Ahammad, C. S. K. Raju, M. Dinesh Kumar, and Wajaree Weera. "Nonlinear Boussinesq and Rosseland approximations on 3D flow in an interruption of Ternary nanoparticles with various shapes of densities and conductivity properties." AIMS Mathematics 7, no. 10 (2022): 18416–49. http://dx.doi.org/10.3934/math.20221014.
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<abstract> <p>In current days, hybrid models have become more essential in a wide range of systems, including medical treatment, aerosol particle handling, laboratory instrument design, industry and naval academia, and more. The influence of linear, nonlinear, and quadratic Rosseland approximations on 3D flow behavior was explored in the presence of Fourier fluxes and Boussinesq quadratic thermal oscillations. Ternary hybrid nanoparticles of different shapes and densities were also included. Using the necessary transformation, the resulting partial differential system is transformed into a governing ordinary differential system, and the solution is then furnished with two mixed compositions (Case-Ⅰ and Case-Ⅱ). Combination one looked at aluminum oxide (Platelet), graphene (Cylindrical), and carbon nanotubes (Spherical), whereas mixture two looked at copper (Cylindrical), copper oxide (Spherical), and silver oxide (Platelet). Many changes in two mixture compositions, as well as linear, quadratic, and nonlinear thermal radiation situations of the flow, are discovered. Case-1 ternary combinations have a wider temperature distribution than Case-2 ternary mixtures. Carbon nanotubes (Spherical), graphene (Cylindrical), and aluminum oxide (Platelet) exhibit stronger conductivity than copper oxide (Spherical), copper (Cylindrical), and silver oxide (Platelet) in Case 1. (Platelet). In copper oxide (Spherical), copper (Cylindrical), and silver (Platelet) compositions, the friction factor coefficient is much higher. The combination of liquids is of great importance in various systems such as medical treatment, manufacturing, experimental instrument design, aerosol particle handling and naval academies, etc. Roseland's quadratic and linear approximation of three-dimensional flow characteristics with the existence of Boussinesq quadratic buoyancy and thermal variation. In addition, we combine tertiary solid nanoparticles with different shapes and densities. In many practical applications such as the plastics manufacturing and polymer industry, the temperature difference is remarkably large, causing the density of the working fluid to vary non-linearly with temperature. Therefore, the nonlinear Boussinesq (NBA) approximation cannot be ignored, since it greatly affects the flow and heat transport characteristics of the working fluid. Here, the flow of non-Newtonian elastomers is controlled by the tension of an elastic sheet subjected to NBA and the quadratic form of the Rosseland thermal radiation is studied.</p> </abstract>
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Koczorowski, Tomasz, Magdalena Cerbin-Koczorowska, and Tomasz Rębiś. "Azaporphyrins Embedded on Carbon-Based Nanomaterials for Potential Use in Electrochemical Sensing—A Review." Nanomaterials 11, no. 11 (October 27, 2021): 2861. http://dx.doi.org/10.3390/nano11112861.
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Phthalocyanines and porphyrazines as macrocyclic aza-analogues of well-known porphyrins were deposited on diverse carbon-based nanomaterials and investigated as sensing devices. The extended π-conjugated electron system of these macrocycles influences their ability to create stable hybrid systems with graphene or carbon nanotubes commonly based on π–π stacking interactions. During a 15-year period, the electrodes modified by deposition of these systems have been applied for the determination of diverse analytes, such as food pollutants, heavy metals, catecholamines, thiols, glucose, peroxides, some active pharmaceutical ingredients, and poisonous gases. These procedures have also taken place, on occasion, in the presence of various polymers, ionic liquids, and other moieties. In the review, studies are presented that were performed for sensing purposes, involving azaporphyrins embedded on graphene, graphene oxide or carbon nanotubes (both single and multi-walled ones). Moreover, possible methods of electrode fabrication, limits of detection of each analyte, as well as examples of macrocyclic compounds applied as sensing materials, are critically discussed.
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Zygo, Monika, Miroslav Mrlik, Marketa Ilcikova, Martina Hrabalikova, Josef Osicka, Martin Cvek, Michal Sedlacik, et al. "Effect of Structure of Polymers Grafted from Graphene Oxide on the Compatibility of Particles with a Silicone-Based Environment and the Stimuli-Responsive Capabilities of Their Composites." Nanomaterials 10, no. 3 (March 24, 2020): 591. http://dx.doi.org/10.3390/nano10030591.
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This study reports the utilization of controlled radical polymerization as a tool for controlling the stimuli-responsive capabilities of graphene oxide (GO) based hybrid systems. Various polymer brushes with controlled molecular weight and narrow molecular weight distribution were grafted from the GO surface by surface-initiated atom transfer radical polymerization (SI-ATRP). The modification of GO with poly(n-butyl methacrylate) (PBMA), poly(glycidyl methacrylate) (PGMA), poly(trimethylsilyloxyethyl methacrylate) (PHEMATMS) and poly(methyl methacrylate) (PMMA) was confirmed by thermogravimetric analysis (TGA) coupled with online Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Various grafting densities of GO-based materials were investigated, and conductivity was elucidated using a four-point probe method. Raman shift and XPS were used to confirm the reduction of surface properties of the GO particles during SI-ATRP. The contact angle measurements indicated the changes in the compatibility of GOs with silicone oil, depending on the structure of the grafted polymer chains. The compatibility of the GOs with poly(dimethylsiloxane) was also investigated using steady shear rheology. The tunability of the electrorheological, as well as the photo-actuation capability, was investigated. It was shown that in addition to the modification of conductivity, the dipole moment of the pendant groups of the grafted polymer chains also plays an important role in the electrorheological (ER) performance. The compatibility of the particles with the polymer matrix, and thus proper particles dispersibility, is the most important factor for the photo-actuation efficiency. The plasticizing effect of the GO-polymer hybrid filler also has a crucial impact on the matrix stiffness and thus the ability to reversibly respond to the external light stimulation.
Dissertations / Theses on the topic "Graphene Oxide - Polymer Hybrid Systems"
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Signorini, Virginia. "Hybrid polymer-based membranes with graphene oxide nanoparticles for carbon dioxide capture." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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The project focuses on the development of hybrid polymer/inorganic membranes with aligned nanoparticles within the polymeric matrix for CO2 separation membrane fabrication. The investigated polymer is the PEG3A, while the inorganic particles are the Graphene Oxide (GO).
The addition of the GO nanoparticles is done due to a UV-light cross-linking reaction between the polymer, the polymer solvent and the solvent in which nanoparticles are dispersed in different concentration. The solvents used for the incorporation of GO into the membrane matrix are Water, Ethanol and Acetone since these fillers are considered non-toxic for human being.
The membrane alignment is expected to improve the performance for CO2/N2 and CO2/He separation application which had been calculated by testing each membrane with the Single Gas Apparatus with the same operative condition.
The compatibility of the polymers and nanoparticles will be characterized by using different techniques such as SEM, TGA and DSC, in order to develop the optimal hybrids for the carbon capture.
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ALRASHED, MAHER M. "ORGANIC/INORGANIC HYBRID COATINGS FOR ANTICORROSION APPLICATIONS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491226580793534.
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Okafor, Patricia A. "Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823253057854.
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Zang, Dejin. "Hybrid polyoxometalate@M NP photosensitized systems for the generation of photocurrent or for the generation of dihydrogen." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF032.
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Différents systèmes polyoxométallates@M-colorants ont été réalisés dans cette thèse pour électrochimique dégagement d'hydrogène catalytique et génération photocourant.• Des films hybrides, basés sur des interactions électrostatiques entre une porphyrine tetracationique et des nanoparticules stabilisées par des POMs du type POM@Pt sur ITO, ont été formés par la méthode dite couche par couche et ont été utilisés pour la génération de H2 ou de photocourant. • Pour améliorer le transfert de charge entre les nanoparticules POM@M et le substrat, la réduction de l'oxyde de graphène a été réalisée pour former des systèmes hybrides rGO/POM@Pt. Le dégagement d'hydrogène a été mesuré.• Les copolymères polycationiques bis-porphyrine ont également été obtenus par électropolymérisation avec des espaceurs bis-pyridinium. Par réaction de métathèse, l’incorporation avec divers POM de type Keggin ou des nanoparticules du type POM@Ag ont ensuite été realise. Leurs performances photovoltaïques ont ensuite été étudiées.• Enfin des films hybrides PEDOT dopés avec des nanoparticules du type POM@M ont également été fabriqués. Les performances photovoltaïques ont été examinés montrant une forte amélioration sous illumination dans le domaine du visible. L’ensemble de ces matériaux hybrides ont montré des propriétés intéressantes pour des applications photovoltaïques et la conversion d'énergiePolyoxometalates@M NPs-dyes molecular hybrid systems were realized in this thesis for electrochemical catalytic hydrogen evolution and photocurrent generation. • First, hybrid films, based on electrostatic interactions between the tetracationic porphyrin and POMs@Pt NPs composites on ITO slides, were formed by the so called Layer-by-Layer method for HER and photocurrent generation.• To improve the charge transfer between POMs@M NPs and the substrate, reduced graphene oxide was introduced to form rGO/POMs@Pt NPs hybrid systems. Hydrogen evolution was measured after dropping this composites onto the surface of glassy carbon electrodes.• Polycationic bis-porphyrin copolymers have been also obtained by an electropolymerization leading to the formation of new bis-porphyrin copolymers with pyridinium as spacers. Incorporation with various Keggin type POMs or POMs@Ag was then achieved, their photovoltaic performances were also studied.• POMs@M NPs doped PEDOT hybrids films have been also fabricated. The photovoltaic performances has been examined showing particularly strong enhancement under visible light. In conclusion, these polyoxometalates based hybrids materials have shown interesting properties for photovoltaic application and energy conversion
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Tsai, Cheng Lung, and 蔡丞龍. "Hybrid photovoltaic devices based on the reduced graphene oxide-based polymer composite and n-type GaAs." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/57158947170290048754.
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碩士國立彰化師範大學
光電科技研究所
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e present a hybrid photovoltaic device based on GaAs and poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) having the reduced graphene oxide (RGO). It is found that conductivity of RGO-doped PEDOT:PSS samples is 27 times higher than that of PEDOT:PSS at 300 K. The improvement of electrical conductivity is considered to mainly come from the mobility enhancement. The carrier mobility in RGO-doped PEDOT:PSS samples exhibits unexpectedly strong temperature dependence, implying the domination of tunneling (hopping) at low (high) temperatures. An exhibition of high mobility of RGO-doped PEDOT:PSS samples is attributed to the increase of the spacing between molecules. In addition, this RGO-doped PEDOT:PSS/GaAs device shows good rectifying behavior with ideality factor of 1.8. The enhanced power conversion efficiency of the PEDOT:PSS/GaAs device was observed by RGO doping. The high photocurrent density originates from high-mobility hole transport combined with long-lifetime electron trapping in the RGO-doped PEDOT:PSS film.
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Kumar, Sachin B. "Engineering Bioactive And Multifunctional Graphene Polymer Composites for Bone Tissue Regeneration." Thesis, 2016. http://etd.iisc.ac.in/handle/2005/2684.
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The growing incidences of orthopedic problems globally have created a huge demand for strong bioactive materials for bone tissue engineering. Over the years, studies have shown chemical, physical, and mechanical properties of biomaterials influence the cellular interactions at the material-tissue interface, which subsequently controls biological response to materials. Strong biomaterials with surface properties that actively direct cellular response hold the key for engineering the next generation orthopedic implants. With its unique properties graphene can be used to reinforce poly (ε-caprolactone) (PCL) to prepare strong and bioactive polymer nanocomposites for bone tissue regeneration. The thesis entitled ―Engineering bioactive and multifunctional graphene polymer composites for bone tissue regeneration” systematically studies the effect of different chemically functionalized and metal-graphene hybrid nanoparticles in PCL composites for bone tissue engineering. The thesis comprises of seven chapters. Chapter 1 is an outline review on the impact of graphene and graphene derived particles to prepare supporting substrates for tissue regeneration and the associated cell response to multifunctional graphene substrate. This chapter discusses how cells interact with different graphene based particles and the interplay between cells performance and multifunctional properties of graphene based substrates.
Chapter 2 describes the role, if any, of the functionalization of graphene on mechanical properties, stem cell response and bacterial biofilm formation. PCL composites of graphene oxide (GO), reduced GO (RGO) and amine-functionalized GO (AGO) were prepared at different filler contents (1%, 3% and 5%). Although the addition of the nanoparticles to PCL markedly increased the storage modulus, this increase was higher for GO and AGO than with RGO. In vitro cell studies revealed that the AGO and GO particles significantly increased human mesenchymal stem cell (hMSC) proliferation. AGO was most effective in augmenting stem cell osteogenesis leading to mineralization. Bacterial studies revealed that interaction with functionalized GO induced bacterial cell death due to membrane damage which was further accentuated by amine groups in AGO. The synergistic effect of oxygen containing functional groups and amine groups on AGO-reinforced composites renders the optimal combination of improved modulus, favorable stem cell response and biofilm inhibition desired for orthopaedic applications. In Chapter 3, toward preparing strong multi-biofunctional materials, poly(ethylenimine) (PEI) conjugated graphene oxide (GO_PEI) was synthesized using poly(acrylic acid) (PAA) as spacer and incorporated in PCL at different fractions. GO_PEI significantly promoted proliferation and formation of focal adhesions in hMSCs on PCL. GO_PEI was highly potent in inducing stem cell osteogenesis leading to 90% increase in alkaline phosphatase activity and mineralization over neat PCL with 5% filler content and was 50% better than GO. Remarkably, 5% GO_PEI was as potent as soluble osteo-inductive factors. Increased adsorption of osteogenic factors due to the amine and oxygen containing functional groups on GO_PEI augment stem cell differentiation. GO_PEI was also highly efficient in imparting bactericidal activity with 85% reduction in counts of E. coli colonies compared to neat PCL at 5% filler content and was more than twice as efficient as GO. This may be attributed to the synergistic effect of the sharp edges of the particles along with the presence of the different chemical moieties. Thus, in contrast to using labile biomolecules, GO_PEI based polymer composites can be utilized to prepare bioactive resorbable biomaterials for fabricating orthopedic devices for fracture fixation and tissue engineering.
Chapter 4 describes the preparation of hybrid nanoparticles of graphene sheets decorated with strontium metallic nanoparticles and its advantages in bone tissue engineering. Strontium-decorated reduced graphene oxide (RGO_Sr) nanoparticles were synthesized by
facile reduction of graphene oxide and strontium nitrate. X-ray diffraction, transmission electron microscopy, and atomic force microscopy revealed that the hybrid particles were composed of RGO sheets decorated with 200 – 300 nm metallic strontium particles. Thermal gravimetric analysis further confirmed the composition of the hybrid particles as 22 wt% of strontium. Macroporous tissue scaffolds were prepared incorporating RGO_Sr particles in PCL. The PCL/RGO_Sr scaffolds were found to elute strontium ions in aqueous medium. Osteoblast proliferation and differentiation was significantly higher in the PCL scaffolds containing the RGO_Sr particles in contrast to neat PCL and PCL/RGO scaffolds. The increased biological activity can be attributed to the release of strontium ions from the hybrid nanoparticles. This study demonstrates that composites prepared using hybrid nanoparticles that elute strontium ions can be used to prepare scaffolds with osteoinductive property. These findings have important implications for designing the next generation of biomaterials for use in tissue regeneration.
Chapter 5 discusses the use of hybrid graphene-silver particles (RGO_Ag) to reinforce PCL and compared with PCL/RGO and PCL/Ag composites containing RGO and silver nanoparticles (AgNPs), respectively. RGO_Ag hybrid particles were well dispersed in the PCL matrix unlike the RGO and AgNPs due to enhanced exfoliation. RGO_Ag led to 77 % increase in the modulus of PCL and provided a conductive network for electron transfer. Electrical conductivity increased four orders of magnitude from 10-11 S/cm to 10-7 S/cm at 5 wt % filler that greatly exceeded the improvements with the use of RGO and AgNP in PCL. RGO_Ag particles reinforced in PCL showed sustained release of silver ions from the PCL matrix unlike the burst release from PCL/Ag. PCL/RGO_Ag and PCL/RGO composites were non-toxic to hMSCs and supported osteogenic differentiation unlike the PCL/Ag composites which were highly toxic at ≥3% filler content. The PCL/RGO_Ag composites exhibited good antibacterial effect due to a combination of silver ion release from the AgNPs and the mechanical rupture induced by the RGO in the hybrid nanoparticles. Thus, the synergistic effect of Ag and RGO in the PCL matrix uniquely yielded a multifunctional material for use in implantable biomedical devices and tissue engineering. Chapter 6 presents investigation of potential differences in the biological response to graphene in polymer composites in the form of 2D substrates and 3D scaffolds. Results showed that osteoblast response to graphene in polymer nanocomposites is markedly altered between 2D substrates and 3D scaffold due to the roughness induced by the sharp edges of graphene at the surface in 3D but not in 2D. Osteoblast organized into aggregates in 3D scaffolds in contrast to more well spread and randomly distributed cells on 2D discs due to the macro-porous architecture of the scaffolds. Increased cell-cell contact and altered cellular morphology led to significantly higher mineralization in 3D scaffolds compared to 2D. This study demonstrates that the cellular response to nanoparticles in composites can change markedly by varying the processing route.
Chapter 7 summarizes the important results and future directions of the work. This chapter provides general conclusions arising from this study, and makes suggestions for future work designed to provide a greater understanding of the in vivo response in terms of bio-distribution of the released functionalized graphene from the scaffold or substrate must be assessed with special attention on their accumulation or excretion.
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Kumar, Sachin B. "Engineering Bioactive And Multifunctional Graphene Polymer Composites for Bone Tissue Regeneration." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2684.
Full textAbstract:
The growing incidences of orthopedic problems globally have created a huge demand for strong bioactive materials for bone tissue engineering. Over the years, studies have shown chemical, physical, and mechanical properties of biomaterials influence the cellular interactions at the material-tissue interface, which subsequently controls biological response to materials. Strong biomaterials with surface properties that actively direct cellular response hold the key for engineering the next generation orthopedic implants. With its unique properties graphene can be used to reinforce poly (ε-caprolactone) (PCL) to prepare strong and bioactive polymer nanocomposites for bone tissue regeneration. The thesis entitled ―Engineering bioactive and multifunctional graphene polymer composites for bone tissue regeneration” systematically studies the effect of different chemically functionalized and metal-graphene hybrid nanoparticles in PCL composites for bone tissue engineering. The thesis comprises of seven chapters. Chapter 1 is an outline review on the impact of graphene and graphene derived particles to prepare supporting substrates for tissue regeneration and the associated cell response to multifunctional graphene substrate. This chapter discusses how cells interact with different graphene based particles and the interplay between cells performance and multifunctional properties of graphene based substrates.
Chapter 2 describes the role, if any, of the functionalization of graphene on mechanical properties, stem cell response and bacterial biofilm formation. PCL composites of graphene oxide (GO), reduced GO (RGO) and amine-functionalized GO (AGO) were prepared at different filler contents (1%, 3% and 5%). Although the addition of the nanoparticles to PCL markedly increased the storage modulus, this increase was higher for GO and AGO than with RGO. In vitro cell studies revealed that the AGO and GO particles significantly increased human mesenchymal stem cell (hMSC) proliferation. AGO was most effective in augmenting stem cell osteogenesis leading to mineralization. Bacterial studies revealed that interaction with functionalized GO induced bacterial cell death due to membrane damage which was further accentuated by amine groups in AGO. The synergistic effect of oxygen containing functional groups and amine groups on AGO-reinforced composites renders the optimal combination of improved modulus, favorable stem cell response and biofilm inhibition desired for orthopaedic applications. In Chapter 3, toward preparing strong multi-biofunctional materials, poly(ethylenimine) (PEI) conjugated graphene oxide (GO_PEI) was synthesized using poly(acrylic acid) (PAA) as spacer and incorporated in PCL at different fractions. GO_PEI significantly promoted proliferation and formation of focal adhesions in hMSCs on PCL. GO_PEI was highly potent in inducing stem cell osteogenesis leading to 90% increase in alkaline phosphatase activity and mineralization over neat PCL with 5% filler content and was 50% better than GO. Remarkably, 5% GO_PEI was as potent as soluble osteo-inductive factors. Increased adsorption of osteogenic factors due to the amine and oxygen containing functional groups on GO_PEI augment stem cell differentiation. GO_PEI was also highly efficient in imparting bactericidal activity with 85% reduction in counts of E. coli colonies compared to neat PCL at 5% filler content and was more than twice as efficient as GO. This may be attributed to the synergistic effect of the sharp edges of the particles along with the presence of the different chemical moieties. Thus, in contrast to using labile biomolecules, GO_PEI based polymer composites can be utilized to prepare bioactive resorbable biomaterials for fabricating orthopedic devices for fracture fixation and tissue engineering.
Chapter 4 describes the preparation of hybrid nanoparticles of graphene sheets decorated with strontium metallic nanoparticles and its advantages in bone tissue engineering. Strontium-decorated reduced graphene oxide (RGO_Sr) nanoparticles were synthesized by
facile reduction of graphene oxide and strontium nitrate. X-ray diffraction, transmission electron microscopy, and atomic force microscopy revealed that the hybrid particles were composed of RGO sheets decorated with 200 – 300 nm metallic strontium particles. Thermal gravimetric analysis further confirmed the composition of the hybrid particles as 22 wt% of strontium. Macroporous tissue scaffolds were prepared incorporating RGO_Sr particles in PCL. The PCL/RGO_Sr scaffolds were found to elute strontium ions in aqueous medium. Osteoblast proliferation and differentiation was significantly higher in the PCL scaffolds containing the RGO_Sr particles in contrast to neat PCL and PCL/RGO scaffolds. The increased biological activity can be attributed to the release of strontium ions from the hybrid nanoparticles. This study demonstrates that composites prepared using hybrid nanoparticles that elute strontium ions can be used to prepare scaffolds with osteoinductive property. These findings have important implications for designing the next generation of biomaterials for use in tissue regeneration.
Chapter 5 discusses the use of hybrid graphene-silver particles (RGO_Ag) to reinforce PCL and compared with PCL/RGO and PCL/Ag composites containing RGO and silver nanoparticles (AgNPs), respectively. RGO_Ag hybrid particles were well dispersed in the PCL matrix unlike the RGO and AgNPs due to enhanced exfoliation. RGO_Ag led to 77 % increase in the modulus of PCL and provided a conductive network for electron transfer. Electrical conductivity increased four orders of magnitude from 10-11 S/cm to 10-7 S/cm at 5 wt % filler that greatly exceeded the improvements with the use of RGO and AgNP in PCL. RGO_Ag particles reinforced in PCL showed sustained release of silver ions from the PCL matrix unlike the burst release from PCL/Ag. PCL/RGO_Ag and PCL/RGO composites were non-toxic to hMSCs and supported osteogenic differentiation unlike the PCL/Ag composites which were highly toxic at ≥3% filler content. The PCL/RGO_Ag composites exhibited good antibacterial effect due to a combination of silver ion release from the AgNPs and the mechanical rupture induced by the RGO in the hybrid nanoparticles. Thus, the synergistic effect of Ag and RGO in the PCL matrix uniquely yielded a multifunctional material for use in implantable biomedical devices and tissue engineering. Chapter 6 presents investigation of potential differences in the biological response to graphene in polymer composites in the form of 2D substrates and 3D scaffolds. Results showed that osteoblast response to graphene in polymer nanocomposites is markedly altered between 2D substrates and 3D scaffold due to the roughness induced by the sharp edges of graphene at the surface in 3D but not in 2D. Osteoblast organized into aggregates in 3D scaffolds in contrast to more well spread and randomly distributed cells on 2D discs due to the macro-porous architecture of the scaffolds. Increased cell-cell contact and altered cellular morphology led to significantly higher mineralization in 3D scaffolds compared to 2D. This study demonstrates that the cellular response to nanoparticles in composites can change markedly by varying the processing route.
Chapter 7 summarizes the important results and future directions of the work. This chapter provides general conclusions arising from this study, and makes suggestions for future work designed to provide a greater understanding of the in vivo response in terms of bio-distribution of the released functionalized graphene from the scaffold or substrate must be assessed with special attention on their accumulation or excretion.
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Berbeć, Sylwia. "Nanokompozyty nanocząstek złota i srebra z elektrochemicznie redukowanym tlenkiem grafenu do zastosowań w elektrokatalizie oraz SERS." Doctoral thesis, 2021. https://depotuw.ceon.pl/handle/item/4036.
Full textAbstract:
Streszczenie
Tematem przewodnim rozprawy jest projektowanie oraz badanie właściwości fizykochemicznych kompozytowych podłoży bazujących na nanostrukturach metalicznych dekorowanych arkuszami grafenowymi. Zaproponowane układy hybrydowe charakteryzujące się różną hydrofilowością były sprawdzane pod kątem możliwych zastosowań jako aktywne katalitycznie powierzchnie oraz podłoża do ultraczułej detekcji SERS.
Niekwestionowaną zaletą połączeń hybrydowych jest możliwość implementowania zupełnie nowych właściwości związanych z ujawnieniem efektów synergii będących wynikiem oddziaływania między molekułami wprowadzonymi do warstwy hybrydowej. Nanostruktury metaliczne o powierzchni stabilizowanej wielocentrowymi mediatorami redoks Keggina (POM) są ciekawą alternatywną w stosunku do powszechnie wykorzystywanych układów kompleksujących ze względu na swoją elektroaktywność. Ligandy POM jednocześnie stabilizują nanostruktury jak i wspomagają przeniesienie elektronu. Związki te posiadają właściwości elektrokatalityczne względem redukcji nadtlenku wodoru w środowisku kwaśnym. W roztworach obojętnych ich stabilność jest ograniczona. Produkty częściowej degradacji POM również wykazują elektroaktywność. Rozkład POM na mniejsze jony odsłania nano-powierzchnię metalu, co skutkuje lepszą aktywnością SERS w porównaniu do wyjściowych nanostruktur metalicznych dekorowanych mediatorami redoks Keggina.
Efektywna, ukierunkowana adsorpcja tego typu anionów na stałych powierzchniach, wysokie przewodnictwo protonowe i elektronowe oraz możliwość przyjmowania szerokiej gamy stanów redoks czyni polioksometalany atrakcyjnymi katalizatorami. Niekwestionowaną zaletą tej klasy stabilizatorów jest również wysoka stabilność chemiczna, termiczna oraz możliwość dostosowania potencjału redoks ligandu do zakresu potencjałowego badanej reakcji elektrodowej co korzystnie wpływa na selektywność procesów elektrokatalitycznych monitorowanych przy użyciu warstw hybrydowych nanocząstka metalu – POM.
W części eksperymentalnej przedkładanej pracy został zaproponowany szereg układów opartych na nanostrukturach złota i srebra stabilizowanych polioksometalanami typu Keggina, które unieruchamiano w obrębie arkuszy o heksagonalnych pierścieniach węglowych bogatych w defekty strukturalne otrzymanych w wyniku elektrochemicznej redukcji tlenku grafenu. Zaprezentowane połączenia hybrydowe zostały sprawdzone pod kątem możliwych zastosowań jako powierzchnie wykazujące aktywność w procesach elektroredukcji nadtlenku wodoru oraz jako podłoża SERS do detekcji sond molekularnych wykazujących luminescencję.
Ważnym osiągnięciem niniejszej rozprawy było wykazanie, iż struktura macierzystych jednostek Keggina nie ulega niekorzystnym zmianom po etapie chemisorpcji anionu na filmie nanostrukturalnym niezależnie od rodzaju rdzenia metalicznego i wybranego typu stabilizatora. Różnice w widmach w podczerwieni oraz Ramana filmów nano-metalicznych świadczyły jednak o odmiennym sposobie unieruchamiania otoczki modyfikującej na warstwie katalizatora.Summary of dissertation The main topic of the dissertation is design and physicochemical characterization of nanocomposites based on surface – decorated metal nanostructures covered by electrochemically reduced graphene oxide. The proposed hybrid systems of different hydrophilicity were tested for possible applications as electrochemical catalysts and platforms for ultra – sensitive SERS detection. Great advantages of hybrid systems are new properties due to the intermolecular interactions between the components resulting in synergy effects. Metal nanoparticles capped with Keggin – type polyoxometalates (POMs) show unique optical and electrochemical properties due to the redox activity of stabilizing ligands. Polyoxometalates (POM) have the ability to stabilize metal nanoparticles and to facilitate the electron transfer at the same time. This class of inorganic ions show intrinsic electrocatalytic properties towards the reduction of hydrogen peroxide in acidic solutions, but their stability at neutral pH is rather weak. The tendency of POM to undergo hydrolysis can be beneficial in electrochemical applications since products of partial POM degradation are electroactive. Due to the fact that electrochemical transformation of POM ions into smaller units leads to exposure of metallic surface, nanoparticles with partially hydrolyzed stabilization agents can exhibit better SERS performance compared to pristine POM-MNPs units. Keggin – type structures chemisorb irreversibly on carbon and metal surfaces, disclose high proton and electron conductivity and have the ability to adopt a wide range of redox states which makes them attractive catalysts. This class of inorganic ions was used in this thesis as ligands stabilizing metal nanoparticles. The ability of POM to adsorb on solid surfaces helped to control the size of metal cores during synthesis. In this dissertation I focused on obtaining and characterization of gold and silver nanostructures stabilized with Keggin – type polyoxometalates covered by layers of hexagonal carbon rings rich in structural defects obtained by the electrochemical reduction of graphene oxide. The presented hybrids were tested as electrochemical sensors for hydrogen peroxide and SERS platforms for molecule showing fluorescence (Rhodamine 6G). An important achievement of this dissertation was to demonstrate that the POM structures do not significantly change after chemisorption regardless the type of metal core used (Au/Ag) and the POMs (SiW or PMo units). However, infrared and Raman spectra of POM-coated nanometallic particles indicated different interaction between POMs and metal core depending on catalyst layer. The phenomenal catalytical performance of gold and silver nanostructures decorated with polyoxometalates were significantly expanded in its nanocomposites with partially reduced graphene oxide. The justification of synergy observed for hybrid systems were discussed based on spectral data. All hybrid systems were examined as possible SERS supports. The observed differences were rationalized by various SERS mechanisms.
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Ivaturi, Sameera. "Electron Filed Emission Studies of Nanostructured Carbon Materials." Thesis, 2012. http://etd.iisc.ac.in/handle/2005/3251.
Full textAbstract:
Field emission is the emission of electrons from a solid under an intense electric field, of the order of 109 V/m. Emission occurs by the quantum mechanical tunneling of electrons through a potential barrier to vacuum. Field emission sources offer several attractive features such as instantaneous response to field variation, resistance to temperature fluctuation and radiation, a high degree of focusing ability in electron optics, good on/off ratio, ballistic transport, and a nonlinear current-voltage relationship.
Carbon nanotubes (CNTs) are potential candidates as field emitters since they possess high aspect ratio and are chemically inert to poisoning, and physically inert to sputtering during field emission. They can carry a very high current density and do not suffer field-induced tip sharpening like metallic tips. In addition, the CNT field emitters have the advantage of charge transport through 1D channels and electron emission at the sharp tips due to large enhancement. But the injection of electrons from the back contact remains a technical challenge which requires binding of CNT emitters to metallic substrate. Also, detachment of the CNT from the substrate tends to occur with time. The electrically conducting mixtures of CNTs and polymer can provide an alternative route to address these issues in the field emission of CNTs. The composites can be casted on any substrate in desired shape and the polymer matrix provides necessary support.
The research work reported in this thesis includes the preparation of high quality multiwall carbon nanotubes (MWCNTs), MWCNT-polystyrene (PS) composites, and experimental investigation on field emission properties of MWCNT¬PS composites in two different configurations. Electrical conductivity and percolation threshold of the MWCNT-PS composites are also investigated to ensure their high quality prior to the field emission studies. The study has been further extended to reduced graphene oxide (rGO) coated on polymer substrate. The main results obtained in present work are briefly summarized below.
This thesis contains eight chapters.
Chapter 1 provides an overview of basics of field emission, and the potential of CNT and CNT-polymer composites as field emitters.
Chapter 2 deals with the concise introduction of various structural characterization tools and experimental techniques employed in this study.
Chapter 3 describes the synthesis of MWCNTs and characterization by using electron microscopy and Raman spectroscopy.
MWCNTs are synthesized by chemical vapor deposition (CVD) of toluene [(C6H5) CH3] and ferrocene [(C5H5)2 Fe] mixture at 980 °C. Here toluene acts as carbon source material and ferrocene provides catalytic iron (Fe) particles. The MWCNT formation is based on the thermal decomposition of the precursor mixture. Scanning electron microscopy (SEM) characterization shows that the MWCNTs are closely packed and quite aligned in one direction. The average length of MWCNTs is about 200 μm and outer diameter lies in the range of 50-80 nm. The high quality of as-prepared MWCNT sample is confirmed by Raman spectroscopy. The as-grown MWCNTs are encapsulated with catalytic Fe nanoparticles, revealed by transmission electron microscopy. The Fe nanoparticles trapped within the MWCNT serve as fantastic system for studying the magnetic properties. Three types of MWCNT samples filled with Fe nanoparticles of different aspect ratio (~10, 5 and 2) are synthesized by varying the amount of ferrocene in the precursor material, and their magnetic properties are investigated. Enhanced values of coercivity (Hc) are observed for all samples, Hc being maximum (~2.6 kOe) at 10 K. The enhancement in Hc values is attributed to the strong shape anisotropy of Fe nanoparticles and significant dipolar interactions between Fe nanoparticles.
Chapter 4 deals with the field emission studies of MWCNT-PS composites in the parallel configuration.
By incorporating as-prepared MWCNTs in PS matrix in a specific ratio, composites with varying loading from 0.01-0.45 weight (wt.) fraction are prepared using solution mixing and casting. High degree of dispersion of MWCNTs in PS matrix without employing any surfactant is achieved by ultrasonication. Low percolation threshold (~0.0025 wt. fraction) in the MWCNT-PS composites ensures the good connectivity of filler in the fabricated samples. Field emission of MWCNT¬PS composites is studied in two different configurations: along the top surface of the film (parallel configuration) and along the cross section of the sample (perpendicular configuration). In this chapter field emission results of the MWCNT-PS composites in parallel configuration are presented. The effect of charge transport in limiting the field emission of MWCNT-PS composite is discussed. Field emission results of MWCNT-PS composites in parallel configuration indicate that the emission performance can be maximized at moderate wt. fraction of MWCNT (0.15). The obtained current densities are ~10 µA/cm2 in the parallel configuration.
Chapter 5 presents the study of field emission characteristics of MWCNT¬PS composites of various wt. fractions in the perpendicular configuration. Till date most studies using nanotube composites tend to have the nanotubes lying in two dimensional plane, perpendicular to the applied electric field. In the perpendicular configuration, the nanotubes are nearly aligned parallel to the direction of the applied electric field which results in high field enhancement, and electron emission at lower applied fields.
SEM micrographs in cross-sectional view reveal that MWCNTs are homogeneously distributed across the thickness and the density of protruding tubes can be scaled with wt. fraction of the composite film. Field emission from composites has been observed to vary considerably with density of MWCNTs in the polymer matrix. High emission current density of 100 mA/cm2 is achieved at a field of 2.2 V/µm for 0.15 wt. fraction. The field emission is observed to follow the Fowler– Nordheim tunneling mechanism, however, electrostatic screening plays a role in limiting the current density at higher wt. fractions.
Chapter 6 highlights the field emission response of rGO coated on a flexible PS film.
Field emission of rGO coated PS film along the cross section of the sample is studied in addition to the top film surface of the film. The effect of geometry on the improved field emission efficiency of rGO coated polymer film is demonstrated. The emission characteristics are analyzed by Fowler–Nordheim tunneling for field emission. Low turn-on field (~0.6 V/µm) and high emission current (~200 mA/cm2) in the perpendicular configuration ensure that rGO can be a potential field emitter.
Furthermore, stability and repeatability of the field emission characteristics are also presented.
Chapter 7 deals with the synthesis, characterization, and field emission of two different kinds of hybrid materials: (1) MWCNT coated with zinc oxide (ZnO) nanoparticles (2) ZnO/graphitic carbon (g-C) core-shell nanowires. The field emission from the bucky paper is improved by anchoring ZnO nanoparticles on the surface of MWCNT. A shift in turn on field from 3.5 V/µm (bucky paper) to 1.0 V/µm is observed by increasing the ZnO nanoparticle loading on the surface of MWCNT with an increase in enhancement factor from 1921 to 4894.
Field emission properties of a new type of field emitter ZnO/g-C core-shell nanowires are also presented in this chapter. ZnO/g-C core/shell nanowires are synthesized by CVD of zinc acetate at 1300 °C. Overcoming the problems of ZnO nanowire field emitters, which in general possess high turn on fields and low current densities, the core-shell nanowires exhibit excellent field emission performance with low turn on field of 2.75 V/µm and high current density of 1 mA/cm2.
Chapter 8 presents a brief summary of the important results and future perspectives of the work reported in the thesis.
10
Ivaturi, Sameera. "Electron Filed Emission Studies of Nanostructured Carbon Materials." Thesis, 2012. http://hdl.handle.net/2005/3251.
Full textAbstract:
Field emission is the emission of electrons from a solid under an intense electric field, of the order of 109 V/m. Emission occurs by the quantum mechanical tunneling of electrons through a potential barrier to vacuum. Field emission sources offer several attractive features such as instantaneous response to field variation, resistance to temperature fluctuation and radiation, a high degree of focusing ability in electron optics, good on/off ratio, ballistic transport, and a nonlinear current-voltage relationship.
Carbon nanotubes (CNTs) are potential candidates as field emitters since they possess high aspect ratio and are chemically inert to poisoning, and physically inert to sputtering during field emission. They can carry a very high current density and do not suffer field-induced tip sharpening like metallic tips. In addition, the CNT field emitters have the advantage of charge transport through 1D channels and electron emission at the sharp tips due to large enhancement. But the injection of electrons from the back contact remains a technical challenge which requires binding of CNT emitters to metallic substrate. Also, detachment of the CNT from the substrate tends to occur with time. The electrically conducting mixtures of CNTs and polymer can provide an alternative route to address these issues in the field emission of CNTs. The composites can be casted on any substrate in desired shape and the polymer matrix provides necessary support.
The research work reported in this thesis includes the preparation of high quality multiwall carbon nanotubes (MWCNTs), MWCNT-polystyrene (PS) composites, and experimental investigation on field emission properties of MWCNT¬PS composites in two different configurations. Electrical conductivity and percolation threshold of the MWCNT-PS composites are also investigated to ensure their high quality prior to the field emission studies. The study has been further extended to reduced graphene oxide (rGO) coated on polymer substrate. The main results obtained in present work are briefly summarized below.
This thesis contains eight chapters.
Chapter 1 provides an overview of basics of field emission, and the potential of CNT and CNT-polymer composites as field emitters.
Chapter 2 deals with the concise introduction of various structural characterization tools and experimental techniques employed in this study.
Chapter 3 describes the synthesis of MWCNTs and characterization by using electron microscopy and Raman spectroscopy.
MWCNTs are synthesized by chemical vapor deposition (CVD) of toluene [(C6H5) CH3] and ferrocene [(C5H5)2 Fe] mixture at 980 °C. Here toluene acts as carbon source material and ferrocene provides catalytic iron (Fe) particles. The MWCNT formation is based on the thermal decomposition of the precursor mixture. Scanning electron microscopy (SEM) characterization shows that the MWCNTs are closely packed and quite aligned in one direction. The average length of MWCNTs is about 200 μm and outer diameter lies in the range of 50-80 nm. The high quality of as-prepared MWCNT sample is confirmed by Raman spectroscopy. The as-grown MWCNTs are encapsulated with catalytic Fe nanoparticles, revealed by transmission electron microscopy. The Fe nanoparticles trapped within the MWCNT serve as fantastic system for studying the magnetic properties. Three types of MWCNT samples filled with Fe nanoparticles of different aspect ratio (~10, 5 and 2) are synthesized by varying the amount of ferrocene in the precursor material, and their magnetic properties are investigated. Enhanced values of coercivity (Hc) are observed for all samples, Hc being maximum (~2.6 kOe) at 10 K. The enhancement in Hc values is attributed to the strong shape anisotropy of Fe nanoparticles and significant dipolar interactions between Fe nanoparticles.
Chapter 4 deals with the field emission studies of MWCNT-PS composites in the parallel configuration.
By incorporating as-prepared MWCNTs in PS matrix in a specific ratio, composites with varying loading from 0.01-0.45 weight (wt.) fraction are prepared using solution mixing and casting. High degree of dispersion of MWCNTs in PS matrix without employing any surfactant is achieved by ultrasonication. Low percolation threshold (~0.0025 wt. fraction) in the MWCNT-PS composites ensures the good connectivity of filler in the fabricated samples. Field emission of MWCNT¬PS composites is studied in two different configurations: along the top surface of the film (parallel configuration) and along the cross section of the sample (perpendicular configuration). In this chapter field emission results of the MWCNT-PS composites in parallel configuration are presented. The effect of charge transport in limiting the field emission of MWCNT-PS composite is discussed. Field emission results of MWCNT-PS composites in parallel configuration indicate that the emission performance can be maximized at moderate wt. fraction of MWCNT (0.15). The obtained current densities are ~10 µA/cm2 in the parallel configuration.
Chapter 5 presents the study of field emission characteristics of MWCNT¬PS composites of various wt. fractions in the perpendicular configuration. Till date most studies using nanotube composites tend to have the nanotubes lying in two dimensional plane, perpendicular to the applied electric field. In the perpendicular configuration, the nanotubes are nearly aligned parallel to the direction of the applied electric field which results in high field enhancement, and electron emission at lower applied fields.
SEM micrographs in cross-sectional view reveal that MWCNTs are homogeneously distributed across the thickness and the density of protruding tubes can be scaled with wt. fraction of the composite film. Field emission from composites has been observed to vary considerably with density of MWCNTs in the polymer matrix. High emission current density of 100 mA/cm2 is achieved at a field of 2.2 V/µm for 0.15 wt. fraction. The field emission is observed to follow the Fowler– Nordheim tunneling mechanism, however, electrostatic screening plays a role in limiting the current density at higher wt. fractions.
Chapter 6 highlights the field emission response of rGO coated on a flexible PS film.
Field emission of rGO coated PS film along the cross section of the sample is studied in addition to the top film surface of the film. The effect of geometry on the improved field emission efficiency of rGO coated polymer film is demonstrated. The emission characteristics are analyzed by Fowler–Nordheim tunneling for field emission. Low turn-on field (~0.6 V/µm) and high emission current (~200 mA/cm2) in the perpendicular configuration ensure that rGO can be a potential field emitter.
Furthermore, stability and repeatability of the field emission characteristics are also presented.
Chapter 7 deals with the synthesis, characterization, and field emission of two different kinds of hybrid materials: (1) MWCNT coated with zinc oxide (ZnO) nanoparticles (2) ZnO/graphitic carbon (g-C) core-shell nanowires. The field emission from the bucky paper is improved by anchoring ZnO nanoparticles on the surface of MWCNT. A shift in turn on field from 3.5 V/µm (bucky paper) to 1.0 V/µm is observed by increasing the ZnO nanoparticle loading on the surface of MWCNT with an increase in enhancement factor from 1921 to 4894.
Field emission properties of a new type of field emitter ZnO/g-C core-shell nanowires are also presented in this chapter. ZnO/g-C core/shell nanowires are synthesized by CVD of zinc acetate at 1300 °C. Overcoming the problems of ZnO nanowire field emitters, which in general possess high turn on fields and low current densities, the core-shell nanowires exhibit excellent field emission performance with low turn on field of 2.75 V/µm and high current density of 1 mA/cm2.
Chapter 8 presents a brief summary of the important results and future perspectives of the work reported in the thesis.
Book chapters on the topic "Graphene Oxide - Polymer Hybrid Systems"
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Sadroddini, Mohsen, and Mehdi Razzaghi-Kashani. "Dielectric Properties of Polydimethylsiloxane (PDMS) Composites Containing Hybrid Silica-Decorated Reduced-Graphene Oxide (SiO2@rGO)." In Eco-friendly and Smart Polymer Systems, 442–45. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45085-4_107.
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Farhanmoghaddam, Fatemeh, and Azizeh Javadi. "Study on Rheology, Crystallinity and Electrical Resistance of Poly(Lactic Acid)/Graphene Oxide Nanocomposites." In Eco-friendly and Smart Polymer Systems, 71–74. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45085-4_18.
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Mirzaee, Ramin, and Ahmad Aref Azar. "Effect of Compatibilizers on Polyamide 6 and Styrene-Butadiene Rubber Blend: Graphene Oxide and Glycidyl Methacrylate." In Eco-friendly and Smart Polymer Systems, 469–72. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45085-4_114.
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Rezvani Moghaddam, Amir, Milad Kamkar, Zahra Ranjbar, Uttandaraman Sundararaj, and Ali Jannesari. "Effect of Low-Functionalized Graphene Oxide on the Rheological and Electrical Properties of Water-Based Epoxy Coatings." In Eco-friendly and Smart Polymer Systems, 166–69. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45085-4_40.
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Naseem, Z., K. Sagoe-Crentsil, and W. Duan. "Graphene-Induced Nano- and Microscale Modification of Polymer Structures in Cement Composite Systems." In Lecture Notes in Civil Engineering, 527–33. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-3330-3_56.
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AbstractRedispersible polymers such as ethylene–vinyl acetate copolymer (EVA) have attracted attention in construction due to their enhanced flexural strength, adhesion, flexibility and resistance against water penetration. However, EVA particles cluster in a highly alkaline cementitious matrix and exhibit poor interaction with the cement matrix. The underlying mechanism of poor dispersibility of EVA is attributed to hydrophobic groups of polymers, a variation in the adsorption rate and molecular diffusion to the interface where they cluster together. This phenomenon can negatively affect the fresh properties of cement and produce a weak microstructure, adversely affecting the resulting composites’ performance. This study highlights how graphene oxide (GO) nanomaterial alters the nano- and microscale structural characteristics of EVA to minimize the negative effects. Transmission electron microscopy (TEM) revealed that the GO sheets modify EVA’s clustered nanostructure and disperse it through electrostatic and steric interactions. Furthermore, scanning electron microscopy (SEM) confirmed altered microscale structural characteristics (viz. surface features) by GO. The altered and enhanced material scale engineering performance, such as the compressive strength of the resulting cement composite, was notable.
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Kim, Hee-Je. "Hybrid Reduced–Graphene Oxide/MnSe2 Cubes: A New Electrode Material for Supercapacitors." In Solar Power and Energy Storage Systems, 143–64. Jenny Stanford Publishing, 2019. http://dx.doi.org/10.1201/9780429458774-6.
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Krishnamoorthy, Karthikeyan, and Sang-Jae Kim. "Raman Spectroscopy and Mapping Analysis of Low-Dimensional Nanostructured Materials and Systems." In Recent Developments in Atomic Force Microscopy and Raman Spectroscopy for Materials Characterization [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99775.
Full textAbstract:
This chapter describes the use of Raman spectroscopy and mapping analysis for the characterization of low dimensional nanostructures, including 2D sheets (graphene oxide, graphene sheets, MoS2, siloxene), and one-dimensional carbyne chains. The Raman mapping analysis and their application towards understanding the molecular level interactions in these low dimensional materials, nanostructured polymer composites, and nanopaints are also discussed. The stoichiometric composition and structure of these low dimensional materials were correlated with the Raman spectral and mapping analysis. Further, Raman spectroscopy for understanding or probing the mechanism of mechanical to electrical energy harvesting properties of carbyne films via the structural transformation from cumulene to polynne networks of carbyne is demonstrated.
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Naghib, Seyed Morteza, Samin Hoseinpour, and Shadi Zarshad. "Carbon Nanostructure/polymer Composites Processing and Characteristics in Localized Controlled Drug Delivery System (LCDDSs)." In Localized Micro/Nanocarriers for Programmed and On-Demand Controlled Drug Release, 71–92. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/9789815051636122010005.
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Carbon nanostructures such as carbon nanotubes, graphene, graphene oxide and their derivatives, have been recognized in biomedicine and drug delivery, due to their outstanding optical, mechanical, thermal, and electrical characteristics. Carbon nanostructures/ polymer composites with various active and functional groups provide many binding sites for inorganic/organic species and biomolecules and are described as favorable candidates to label and drag different drugs, genes, proteins and therapeutic molecules. This chapter focuses on studies about the deployment of nanostructures/ polymer composites, for efficient drug delivery, especially localized controlled drug/gene delivery systems (LCDDS). Effects of various parameters and features, including composite microstructures, hydrophobicity and hydrophilicity of composites, glass transition and polymer matrix molecular weight, on LCDDS are fully examined and discussed.
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Meera, A. P., Reshma R. Pillai, and P. B. Sreelekshmi. "Novel Polymer Nanocomposites: Synthesis, Designing and Cost-effective Biomedical Applications." In Bio-Inspired Nanotechnology, 56–72. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815080179123010006.
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The design of materials for various biomedical applications is truly challenging since it demands exceptional characteristics such as biocompatibility, biodegradability, non-cytotoxicity, adequate strength, etc. Several strategies have been developed for the synthesis of nanoparticles based on chemical methods. However, the toxicity limits their applications in biological systems. So researchers are looking for materials that can fulfill green criteria in the sense that they should be renewable, harmless to human health, and environment friendly. Recently, the evolution of nanomedicine led to explore the possibilities of different types of nanomaterials in various applications. Nanoscale polymeric materials and polymer nanocomposites have already proved their versatility in various biomedical applications. This chapter presents a brief overview of the potential of biobased nanomaterials and nanofillers such as metal and metal oxide nanoparticles, hydroxyapatite, nanotubes, graphene, chitin whiskers, lignin, nano cellulose, etc. and their pros and cons when used in the biomedical field. Bio-based polymers are promising candidates for the next generation nanocomposite materials due to their multi-functionality, renewability, low toxicity and excellent biocompatibility. The chapter begins with the state of the art including the recent developments in the biomedical field and finally, the challenges and future potential of various nanoparticles and polymer nanocomposites are also discussed.
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Vargas-Bernal, Rafael, and Margarita Tecpoyotl-Torres. "Nanocomposites for Space Applications." In Research Anthology on Synthesis, Characterization, and Applications of Nanomaterials, 1681–705. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-8591-7.ch070.
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A review on the advances achieved in the last 25 years in the development of hybrid nanocomposites based on polymer matrix for aerospace applications is presented here. The chapter analyzes the state-of-the-art strategies used in the design of materials that support the different conditions of the space environment. These materials are aimed primarily at structural applications, electromagnetic interference shielding, self-sensing, and self-healing, although they are not restricted to these applications. The introduction of metallic, ceramic, carbon-based nanomaterials such as carbon nanotubes and graphene, as well as two-dimensional materials have been used with a successful impact. Despite the significant advances that have been reached, much work must be done to achieve complete reliability for all properties required to protect the systems against the hazardous conditions found in space. Therefore, futuristic visions of the actions that must be carried out are raised in this chapter.
Conference papers on the topic "Graphene Oxide - Polymer Hybrid Systems"
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Sigamani, Nirmal Shankar, Zoubeida Ounaies, and Henry Sodano. "Synthesis and Characterization of PVDF-Based SWNT/GO Hybrid Films." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8021.
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Hybrid nanocomposites with single walled carbon nanotubes (SWNT) and graphene oxide (GO) as nanofillers and polyvinylidene fluoride (PVDF) as a polymer were synthesized as potential electronic active polymers (EAPs) with high breakdown strength. A co-solvent method was developed to achieve exfoliation and dispersion of GO in PVDF. The microstructure of the PVDF was found to be predominantly γ phase. Percent crystallinity of PVDF increased due to the addition of the hybrid nanofillers. And, at room temperature, the storage modulus is increased by 56.26% over the pure PVDF. The dielectric constant increased from ∼7 to ∼25 for the hybrid nanocomposites as compared to pure PVDF at 1KHz measurement frequency. Dielectric loss of the hybrid nanocomposite is found less than 0.6 for the frequency range from 20 Hz–1MHz. Electrical conductivity of the hybrid nanocomposite increase by nearly two orders of magnitude at 1KHz when compared to pure PVDF. The effect of the presence of these hybrid nanofillers on microstructure and properties of PVDF are discussed.
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Giuri, Antonella, Sofia Masi, Silvia Colella, Andrea Listorti, Aurora Rizzo, Giuseppe Gigli, Andrea Liscio, et al. "Polymer Nanocomposites based on in situ reduced graphene oxide for photovoltaic applications in innovative hybrid solar cells." In 2015 1st Workshop on Nanotechnology in Instrumentation and Measurement (NANOFIM). IEEE, 2015. http://dx.doi.org/10.1109/nanofim.2015.8425328.
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Yoshida, Hideki, Shinji Amaha, and Hisataka Yakabe. "Hybrid Systems Using Solid Oxide Fuel Cell and Polymer Electrolyte Fuel Cell." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66213.
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In this paper, the concept of an SOFC (Solid Oxide Fuel Cell) and PEFC (Polymer Electrolyte Fuel Cell) hybrid system is presented. Large-scale SOFC systems operated in a thermally self-sustainable state produce excess heat. The excess heat can be used for producing hydrogen. Several variations of hydrogen production systems are presented here. One way is to produce the hydrogen by using an extra reformer. Another way is purifying the off-fuel of SOFCs. The produced hydrogen can be used as the fuel for PEFCs. The overall electrical efficiency of a combination of an SOFC and PEFCs is higher than that of a standalone SOFC. When the hydrogen produced by purifying the off-fuel of the SOFC is used as the fuel for PEFCs, the overall electrical conversion efficiency increases by around 20%.
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Junaid, Muhammad, Mohd Haris Bin Md Khir, Gunawan Witjaksono, M. Shuaib Bin Mohamed Saheed, Zaka Ullah, and Muhammad Aadil Siddiqui. "Enhanced and Tunable Surface Plasmons Assisted Emission from Reduced Graphene Oxide and Gold Hybrid Configuration." In 2020 8th International Conference on Intelligent and Advanced Systems (ICIAS). IEEE, 2021. http://dx.doi.org/10.1109/icias49414.2021.9642698.
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Malakooti, Mohammad H., Hyun-Sik Hwang, and Henry A. Sodano. "Vibration Damping Enhancement in Hybrid Carbon Fiber Composites With Zinc Oxide Nanowire Interphase." In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7451.
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Traditional composite materials invented to be used in structures with the purpose of high load-bearing with excellent in-plane properties. Continuous fiber reinforced composites are one of the mostly used categories of advanced composites. This class of composites has gained a lot of attention due to their light-weight and decent mechanical properties. However, additional material design is required to tune both mechanical and structural properties of these composites. Since the load transfer between reinforcement phase and polymer matrix happens at the interfacial region, a better interphase might result in a composite with higher vibration damping. In this study, a gradient interphase between carbon fiber and polymer matrix has been created by using ZnO nanowires to engineer the damping loss factor of the carbon fiber composites. For the growth of ZnO nanowires on the carbon fabric, low temperature hydrothermal reaction has been used. Then the carbon fabrics with ZnO nanowires were infiltrated with a low viscosity epoxy using vacuum assisted resin transfer molding technique. The stiffness and structural damping of the composite were examined using dynamic mechanical analysis. The results show that the damping properties of hybrid composites using ZnO nanowires are enhanced compare to the bare carbon fabric composites. Since the growth of ZnO nanowires is a tunable process, the length, diameter and aspect ratio of the nanowires and consequently the architecture of the interphase can be tailored for the desired vibration damping in the system. Thus, the hybrid composites with ZnO nanowire interphase can be used to enhance the energy dissipation in a structural system.
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Khodaparast, Payam, and Zoubeida Ounaies. "On the Dielectric and Mechanical Behavior of Metal Oxide-Modified PVDF-Based Nanocomposites." In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3302.
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Nanoparticle modified polymers have promise as hybrid materials that exhibit properties beyond those predicted by mixing law theories. In the case of metal-oxide nanoparticles in a polymer, it is expected that multifunctional properties of the obtained nanocomposite, including dielectric and mechanical, will be dominated by presence of interface rather than predicted by the inherent properties of individual components. This paper will focus on understanding the role of different types of nanoparticles, namely, titania, silica and alumina and a polymer matrix, Polyvinylidene fluoride (PVDF) in affecting the final dielectric and mechanical properties.
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ANILAL, ASHISH, JUSTIN BENDESKY, SEHEE JEONG, STEPHANIE S. LEE, and MICHAEL BOZLAR. "EFFECTS OF GRAPHENE ON TWISTING OF HIGH DENSITY POLYETHYLENE." In Proceedings for the American Society for Composites-Thirty Seventh Technical Conference. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/asc37/36468.
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High density polyethylene (HDPE) is known to form banded spherulites when crystallized from the melt. In such spherulites, concentric bands of alternating light and dark colors emanating from the spherulite nucleation center are observable between cross polarizers and appear as a function of the anisotropy of the dielectric susceptibility as crystal orientations continuously rotate about the growth direction. Recently, we identified PE to be a promising compound to induce twisting in conjugated carbonaceous systems, such as triisopropylsilylethynyl anthradithiophene (TIPS ADT). When blended together in ratios between 10 – 70 wt.% PE, TIPS ADT and PE crystals twist in concert with one another to form composite films of intertwined helicoidal fibrils. In this work, we investigate crystal twisting in HDPE-graphene oxide composites. In addition to its unique multifunctionality, graphene has also recently demonstrated peculiar twisting capabilities that strongly alter its physical properties. Here, we first produce graphene sheets through the chemical oxidation of natural graphite, and then investigate the influence of graphene on the twisting of HDPE composites under various processing parameters (graphene concentration, polymer cooling rate, etc). HDPE-graphene composites have been prepared using melt extrusion in the form of microfibers and films. We measured the influence of twisting on the mechanical and electrical properties of the composites, as well as the crystallographic structure using optical and electron microscopy, and X-Ray diffraction spectroscopy.
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Welles, Thomas S., and Jeongmin Ahn. "Advancements of a Piston Engine and Electrochemical Combined Hybrid System for Unmanned Aerial Systems." In ASME 2020 Power Conference collocated with the 2020 International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/power2020-16381.
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Abstract This work investigates the integration of solid oxide fuel cells (SOFCs) and a small methanol/nitromethane fueled piston engine as a prospective hybrid powertrain for small unmanned aerial systems (UASs). The increased chemical energy density of a liquid fuel when compared to traditional batteries, along with ease of storage, accessibility, and refuel time make the use of a liquid fuel powered UAS preferable when compared to battery only power UAS’. Currently small UAS’ of increasing interest as a research area, as they have a wide application to a variety of fields. UAS’ are currently being used for precision agricultural crop management and water resource visual inspection. UAS’ are a cost effective avenue to survey water resources and track water runoff that is contaminating water resources. UAS’ can be easily automated and fitted with sensors and cameras capable of providing actionable feedback to the user. The use of UAS’ for land management and survey is expected to continue to expand. However, nearly all UAS’ are powered by a typical lithium polymer battery pack, giving an average endurance of approximately twenty minutes. This is acceptable to most hobbyists and for short filming duration; however, it limits UAS’ to only being able to be operated in close proximity to the user. Current power plants for UAS’ are not suited for long duration missions, such as the survey of water resources. Therefore, the development of a hybrid power plant is crucial for UAS’ to be utilized to their full potential as a survey tool. This work introduces a small internal combustion engine to act as a partial oxidation fuel reformer, producing high temperature exhaust and syngas. The exhaust of this engine is then analyzed as a fuel source for tubular SOFC’s. The SOFC is integrated into the exhaust of a 3.3 cm3 nitromethane fueled two-stroke engine, achieving a maximum power of 680 mW/cm2. A theoretical comparison of flight time indicates that the modular hybrid system could increase a typical small UAS’ flight time beyond 1 hour. The system is capable of achieving a significantly higher energy density than traditional lithium polymer batteries.