Dissertations / Theses on the topic 'Graphene - Nano composite materials'
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1
Cheekati, Sree Lakshmi. "GRAPHENE BASED ANODE MATERIALS FOR LITHIUM-ION BATTERIES." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1302573691.
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Holliday, Nathan. "Processing and Properties of SBR-PU Bilayer and Blend Composite Films Reinforced with Multilayered Nano-Graphene Sheets." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1458300045.
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Rai, Rachel H. "Synthesis and Characterization of Graphene Based Composites for Non-Linear Optical Applications." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461600917.
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Liu, Jian. "Fabrication of composite materials with addition of graphene platelets." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5484/.
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This PhD project set out to tackle the disadvantages of brittleness and low corrosion resistance that ceramics and mild steel bear respectively by developing ceramic and metallic nanocomposites using nanostructured fillers. Graphene platelets (GPLs) as newly emerging carbon materials were chosen as the reinforcing fillers. Two types of nanocomposites were fabricated and their mechanical or corrosion resistant properties were characterized. Alumina (Al2O3) based nanocomposites reinforced with GPLs were sintered and GPL/Nickel (Ni) nanocomposites were produced using an electrodeposition technique. The results show that the mechanical properties of the ceramic matrices are significantly improved by adding nano fillers. Toughening mechanisms induced by GPLs, such as pull-out, crack deflection and crack bridging are observed. On the other hand, the mechanical and corrosion resistance properties of Ni matrix are greatly enhanced by the addition of GPLs. In addition, the higher percentage of GPLs results in finer and more uniform Ni microstructures, leading to the higher hardness and corrosion resistance.
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Shirolkar, Ajay. "A Nano-composite for Cardiovascular Tissue Engineering." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10840053.
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Cardiovascular disease (CVD) is one of the largest epidemic in the world causing 800,000 annual deaths in the U.S alone and 15 million deaths worldwide. After a myocardial infarction, commonly known as a heart attack, the cells around the infarct area get deprived of oxygen and die resulting in scar tissue formation and subsequent arrhythmic beating of the heart. Due to the inability of cardiomyocytes to differentiate, the chances of recurrence of an infarction are tremendous. Research has shown that recurrence lead to death within 2 years in 10% of the cases and within 10 years in 50% of the cases. Therefore, an external structure is needed to support cardiomyocyte growth and bring the heart back to proper functioning. Current research shows that composite materials coupled with nanotechnology, a material where one of its dimension is less than or equal to 100nm, has very high potential in becoming a successful alternative treatment for end stage heart failure. The main goal of this research is to develop a composite material that will act as a scaffold to help externally cultured cardiomyocytes grow in the infarct area of the heart. The composite will consist of a poly-lactic co glycolic acid (PLGA) matrix, reinforced with carbon nanotubes. Prior research has been conducted with this same composite, however the significance of the composite developed in this research is that the nanotubes will be aligned with the help of an electro-magnetic field. This alignment is proposed to promote mechanical strength and significantly enhance proliferation and adhesion of the cardiomyocytes.
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Kudo, Akira Ph D. Massachusetts Institute of Technology. "Growth mechanisms of carbon nano-fibers, -tubes, and graphene on metal oxide nano-particles and -wires." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104466.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 195-208).
Carbon nanostructures (CNS) such as carbon nano-fibers (CNFs), -tubes (CNTs), and graphene are of interest for a diverse set of applications. Currently, these CNS are synthesized primarily by chemical vapor deposition (CVD) techniques, using metal catalysts. However, after CNS synthesis, those metals are oftentimes detrimental to the intended application, and extra steps for their removal, if available, have to be taken. As an alternative to metallic catalysts, metal oxide catalysts are investigated in order to better understand metal-free CVD processes for CNS synthesis. This thesis furthers the mechanistic understanding of metal oxide mediated CNS growth, especially metal oxide nanoparticles (MONPs) for CNTs, thereby addressing yield and expanding the range of known catalysts and atmospheric CVD conditions for CNS growth. CNT and CNF growth from zirconia nanoparticles (NPs) are first studied, and a technique is developed to grow CNTs and CNFs from metal NP (MNP) and MONP catalysts under identical CVD conditions. The morphologies of the catalyst-CNT and -CNF interface for zirconia NPs are found to be different than for iron or chromium NPs via high resolution transmission electron microscopy (HRTEM) including elemental and phase analyses, and evidence of surface-bound base growth mechanisms are observed for the zirconia NPs. Titania NP growth conditions are investigated parametrically to achieve homogeneous and relatively (vs. zirconia) high growth yield, where clusters of CNTs and CNFs separated by only tens of nanometers are observed. Catalytic activity of titania NPs are estimated to be an order of magnitude lower than iron NPs, and a lift-off mechanism for titania NP catalysts is described, indicating that several layers of graphene will cause lift-off, consistent with HRTEM observations of 4-5 layer graphite within the CNFs. Potential catalytic CNS activity of chromia, vanadia, ceria, lithia and alumina NPs are explored, establishing for the first time CNT growth from chromia and vanadia precursor-derived NPs, although the phases of those NPs are not determined during growth. The insights acquired from MONP-mediated CNS growth are applied to demonstrate continuous, high-yield, few-layer graphene formation on titania nanowires.
by Akira Kudo.
Ph. D.
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Smith, Jacob A. "Electrical Performance of Copper-Graphene Nano-Alloys." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1550675878730599.
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Evanoff, Kara. "Highly structured nano-composite anodes for secondary lithium ion batteries." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53388.
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Interest in high performance portable energy devices for electronics and electric vehicles is the basis for a significant level of activity in battery research in recent history. Li-ion batteries are of particular interest due to their high energy density, decreasing cost, and adaptable form factor. A common goal of researchers is to develop new materials that will lower the cost and weight of Li-ion batteries while simultaneously improving the performance. There are several approaches to facilitate improved battery system-level performance including, but not limited to, the development of new material structures and/or chemistries, manufacturing techniques, and cell management.
The performed research sought to enhance the understanding of structure-property relationships of carbon-containing composite anode materials in a Li-ion cell through extensive materials and anode performance characterization. The approach was to focus on the development of new electrode material designs to yield higher energy and power characteristics, as well as increased thermal and electrical conductivities or mechanical strength, using techniques that could be scaled for large volume manufacturing. Here, three different electrode architectures of nanomaterial composites were synthesized and characterized. Each electrode structure consisted of a carbon substrate that was conformally coated with a high Li capacity material. The dimensionality and design for each structure was unique, with each offering different advantages. The addition of an external coating to further increase the stability of high capacity materials was also investigated.
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Zhang, Meixi. "Synthesis, characterization of graphene and the application of graphene carbon nanotube composite in fabricating electrodes." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1445615248.
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MacGibbon, Rebecca Mary Alice. "Designer nano-composite materials with tailored adsorption and sensor properties." Thesis, University of Surrey, 2006. http://epubs.surrey.ac.uk/844469/.
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This thesis is concerned with the possibility of producing novel materials by the sol-gel method that could be incorporated into a new sensing system to be used for the detection of hydrocarbons, in particular methane. Possibilities for a new system include coating optical fibres, at pre-determined points, with a material that causes some sort of disruption in the signal of the fibre when in contact with a hydrocarbon or specifically methane. Dip coating an optical fibre with a sol-gel would be a method for producing an optical fibre based system. This would provide variable chemistry, refractive index and hydrocarbon sensitivity. New silica-based sol-gel materials are presented and titania is incorporated to some of these materials in order to improve the catalytic potential of the system and to increase the refractive index. In order to increase the hydrophobicity and elasticity of the final coatings, organic modifiers are added. The sol-gel materials are characterised by a variety of techniques as both monoliths and thin films. Along with the characterisation, the samples are analysed to determine their potential to adsorb methane and water and the possibility of incorporating the samples in to an optical fibre sensor system utilising ultra-violet/visible spectroscopy. The presence of titania and/or organic modifiers in a silica based sol-gel system are seen to increase significantly the extent of methane adsorption and decrease the extent of water sorption at 293-298 K. It appears that having both titania and organic modifier gives a bigger effect on adsorption than either one alone. The reasons for this are considered in detail.
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Basnayaka, Punya A. "Development of Nanostructured Graphene/Conducting Polymer Composite Materials for Supercapacitor Applications." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4864.
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The developments in mobile/portable electronics and alternative energy vehicles prompted engineers and researchers to develop electrochemical energy storage devices called supercapacitors, as the third generation type capacitors. Most of the research and development on supercapacitors focus on electrode materials, electrolytes and hybridization. Some attempts have been directed towards increasing the energy density by employing electroactive materials, such as metal oxides and conducting polymers (CPs). However, the high cost and toxicity of applicable metal oxides and poor long term stability of CPs paved the way to alternative electrode materials. The electroactive materials with carbon particles in composites have been used substantially to improve the stability of supercapacitors. Furthermore, the use of carbon particles and CPs could significantly reduce the cost of supercapacitor electrodes compared to metal oxides. Recent developments in carbon allotropes, such as carbon nanotubes (CNTs) and especially graphene (G), have found applications in supercapacitors because of their enhanced double layer capacitance due to the large surface area, electrochemical stability, and excellent mechanical and thermal properties.
The main objective of the research presented in this dissertation is to increase the energy density of supercapacitors by the development of nanocomposite materials composed of graphene and different CPs, such as: (a) polyaniline derivatives (polyaniline (PANI), methoxy (-OCH3) aniline (POA) and methyl (-CH3) aniline (POT), (b) poly(3-4 ethylenedioxythiophene) (PEDOT) and (c) polypyrrole (PPy). The research was carried out in two phases, namely, (i) the development and performance evaluation of G-CP (graphene in conducting polymers) electrodes for supercapacitors, and (ii) the fabrication and testing of the coin cell supercapacitors with G-CP electrodes.
In the first phase, the synthesis of different morphological structures of CPs as well as their composites with graphene was carried out, and the synthesized nanostructures were characterized by different physical, chemical and thermal characterization techniques, such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, BET surface area pore size distribution analysis and Thermogravimetric Analysis (TGA). The electrochemical properties of G-CP nanocomposite-based supercapacitors were investigated using Cyclic Voltammetry (CV), galvanostatic charge-discharge and Electrochemical Impedance Spectroscopy (EIS) techniques in different electrolytes, such as acidic (2M H2SO4 and HCl), organic ( 0.2 M LiClO4) and ionic liquid (1M BMIM-PF6) electrolytes.
A comparative study was carried out to investigate the capacitive properties of G-PANI derivatives for supercapacitor applications. The methyl substituted polyaniline with graphene as a nanocomposite (G-POT) exhibited a better capacitance (425 F/g) than the G-PANI or the G-POA nanocomposite due to the electron donating group of G-POT. The relaxation time constants of 0.6, 2.5, and 5s for the G-POT, G-PANI and G-POA nanocomposite-based supercapacitors were calculated from the complex model by using the experimental EIS data.
The specific capacitances of two-electrode system supercapacitor cells were estimated as 425, 400, 380, 305 and 267 F/g for G-POT, G-PANI, G-POA, G-PEDOT and G-PPy, respectively. The improvements in specific capacitance were observed due to the increased surface area with mesoporous nanocomposite structures (5~10 nm pore size distribution) and the pseudocapacitance effect due to the redox properties of the CPs. Further, the operating voltage of G-CP supercapacitors was increased to 3.5 V by employing an ionic liquid electrolyte, compared to 1.5 V operating voltage when aqueous electrolytes were used. On top of the gain in the operating voltage, the graphene nano-filler of the nanocomposite prevented the degradation of the CPs in the long term charging and discharging processes.
In the second phase, after studying the material's chemistry and capacitive properties in three-electrode and two-electrode configuration-based basic electrochemical test cells, coin cell type supercapacitors were fabricated using G-CP nanocomposite electrodes to validate the tested G-CPs as devices. The fabrication process was optimized for the applied force and the number of spacers in crimping the two electrodes together. The pseudocapacitance and double layer capacitance values were extracted by fitting experimental EIS data to a proposed equivalent circuit, and the pseudocapacitive effect was found to be higher with G-PANI derivative nanocomposites than with the other studied G-CP nanocomposites due to the multiple redox states of G-PANI derivatives. The increased specific capacitance, voltage and small relaxation time constants of the G-CPs paved the way for the fabrication of safe, stable and high energy density supercapacitors.
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Peng, Suili. "Nano/micro particle-based functional composites and applications /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?NSNT%202007%20PENG.
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Peters, Sarah June. "Fracture Toughness Investigations of Micro and Nano Cellulose Fiber Reinforced Ultra High Performance Concrete." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/PetersSJ2009.pdf.
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POLVERINO, SALVATORE. "Graphene-based construction materials: experimentation and application development." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1058131.
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The construction sector is entering the new era of production, construction and management of Industry 4.0. The development of smart and resilient technologies focused on the user and the environment has significant potential to improve the ways of experiencing indoor and outdoor spaces. This scenario generates new opportunities to exploit innovation to create the conditions for human well-being and to contribute to the future of the Earth.
The construction sector is in a period of transition. On the one hand, there is a demand for construction with high technological content, capable of incorporating innovations at low cost, low environmental impact, low energy consumption, safe and resilient, adaptable, convertible, transformable over time and personalised; on the other hand, there is a continued reliance on traditional building approaches/solutions that only partially meet the new requirements.
In this context, the research into new materials to produce innovative construction components capable of contributing to the achievement of the above-mentioned objectives is one of the areas of contemporary development. Among them are included two-dimensional materials that owe their name to their particular structure, consisting of a single atomic layer.
The event that enabled such a reduction in the size scale was the isolation of graphene, a material with unique properties and numerous possible applications. Its potential uses are currently being studied and tested, as demonstrated by the numerous research programmes on the subject, aimed at transferring technology from research laboratories to industry.
This PhD research aims to investigate the potential applications of graphene in the field of cementitious composites and polymer-based coatings. The activities carried out included: a critical analysis of the state of the art of the most recent applications in the field of construction; the consequent choice of possible composite materials graphene and graphene-related materials based; the design and development of an experimental campaign; the proposal and final verification of the applications in the construction sector. The activities were carried out in collaboration with the Graphene Labs of the Italian Institute of Technology (IIT).
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Zhai, Yun. "Studies on Structure and Property of Polymer-based Nano-composite Materials." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1680.
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The mixing of polymers and nanoparticles makes it possible to give advantageous macroscopic material performance by tailoring the microstructure of composites. In this thesis, five combinations of nano inclusion and polymer matrix have been investigated.
The first type of composites is titanium dioxide/ polyaniline combination. The effects of 4 different doping-acids on the microstructure, morphology, thermal stability and thermoelectric properties were discussed, showing that the sample with HCl and sulfosalicylic dual acids gave a better thermoelectric property. The second combination is titanium dioxide/polystyrene composite. Avrami equation was used to investigate the crystallization process. The best fit of the mass derivative dependence on temperature has been obtained using the double Gaussian dependence. The third combination is titanium dioxide/polyaniline/ polystyrene. In the titanium dioxide/polyaniline/ polystyrene ternary system, polystyrene provides the mechanical strength supporting the whole structure; TiO2 nanoparticles are the thermoelectric component; Polyaniline (PANI) gives the additional boost to the electrical conductivity. We also did some investigations on Polyethylene odide-TiO2 composite. The cubic anatase TiO2 with an average size of 13nm was mixed with Polyethylene-oxide using Nano Debee equipment from BEE international;
Single wall carbon nanotubes were introduced into the vinyl acetate-ethylene copolymer (VAE) to form a connecting network, using high pressure homogenizer (HPH). The processing time has been reduced to 1/60 of sonication for HPH to give better sample quality. Theoretical percolation was derived according to the excluded volume theory in the expression of the threshold as a function of aspect ratio.
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Liu, Yiyang. "PHOTOLUMINESCENCE MECHANISM AND APPLICATIONS OF GRAPHENE QUANTUM DOTS." UKnowledge, 2017. http://uknowledge.uky.edu/chemistry_etds/78.
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Graphene quantum dots (GQDs) are small pieces of graphene oxide whose physical dimensions are so confined (a few to a few tens nm) that they have a finite bandgap due to a quantum confinement effect. The finite bandgap of GQDs grants them pronounced absorption bands and a substantial photoluminescence. These optical properties are rarely observed in traditional carbon materials, since most of carbon materials are metallic with a near-zero bandgap and thus have broad absorption spectra with no photoluminescence. The unique optical properties of GQDs, along with GQDs’ inherited advantages from carbon material family (cheap, abundant, non-toxic), make GQDs an attractive material for various applications such as bio-imaging, photoinduced therapy, chemical and metal ion sensors, and photovoltaic devices. Despite of their great potential, several great challenges need to be overcome to enable wider applications. One challenge is the fact that GQDs prepared by typical chemical methods possess significant inhomogeneity, so the precise control of the dimension and surface functionalities is very difficult. Due to the inhomogeneity of GQDs in terms of dimensions and surface functionalities, it is challengeable to establish a precise structure-property relationship. As of today, it is still under debate how surface functional groups of GQDs are responsible for the photoluminescence mechanism, photophysics, and photochemistry. This dissertation is mainly to provide a dedicated study about the photoluminescence mechanism and structure-property relations of GQDs.
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Johnson, Timothy Michael. "Strain Monitoring of Carbon Fiber Composite with Embedded Nickel Nano-Composite Strain Gage." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2622.
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Carbon fiber reinforced plastic (CFRP) composites have extensive value in the aerospace, defense, sporting goods, and high performance automobile industries. These composites have huge benefits including high strength to weight ratios and the ability to tailor their properties. A significant issue with carbon fiber composites is the potential for catastrophic fatigue failure. To better understand this fatigue, there is first a huge push to measure strain accurately and in-situ to monitor carbon fiber composites. In this paper, piezoresistive nickel nanostrand (NiNs) nanocomposites were embedded in between layers of carbon fiber composite for real time, in situ strain monitoring. Several different embedding methods have been investigated. These include the direct embedding of a patch of dry NiNs and the embedding of NiNs-polymer matrix nanocomposite patches which are insulated from the surrounding carbon fiber. Also, two different polymer matrix materials were used in the nanocomposite to compare the piezoresistive signal. These nanocomposites are shown to display repeatable piezoresistivity, thus becoming a strain sensor capable of accurately measuring strain real time and in-situ. This patch has compatible mechanical properties to existing advanced composites and shows good resolution to small strain. This method of strain sensing in carbon fiber composites is more easily implemented and used than other strain measurement methods including fiber Bragg grating and acoustic emissions. To show that these embedded strain gages can be used in a variety of carbon fiber components, two different applications were also pursued.
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Liu, Liyu. "Design and fabrication of microfluidic/microelectronic devices from nano particle based composites /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?NSNT%202008%20LIU.
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LAVAGNA, LUCA. "Carbon materials and their role as reinforcement in composite materials." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2729657.
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Song, Yicheng. "The behavior and properties of ferroelectric single crystals and ferroelectric nano-composites." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B3955806X.
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Song, Yicheng, and 宋亦誠. "The behavior and properties of ferroelectric single crystals and ferroelectric nano-composites." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3955806X.
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Ball, Jeffrey Craig. "Design and analysis of multifunctional composite structures for nano-satellites." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2572.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017.The aim of this thesis is to investigate the applications of multifunctional compos- ite (MFC) technology to nano-satellite structures and to produce a working concept design, which can be implemented on future Cube-Satellites (CubeSats). MFC tech- nologies can be used to optimise the performance of the satellite structure in terms of mass, volume and the protection it provides. The optimisation of the structure will allow further room for other sub-systems to be expanded and greater payload allowance. An extensive literature view of existing applications of MFC materials has been conducted, along with the analysis of a MFC CubeSat structural design account- ing for the environmental conditions in space and well-known design practices used in the space industry. Numerical analysis data has been supported by empirical analysis that was done where possible on the concept material and structure. The ndings indicate that the MFC technology shows an improvement over the conventional alu- minium structures that are currently being used. Improvements in rigidity, mass and internal volume were observed. Additional functions that the MFC structure o ers include electrical circuitry and connections through the material itself, as well as an increase electromagnetic shielding capability through the use of carbon- bre composite materials. Empirical data collected on the MFC samples also show good support for the numerical analysis results. The main conclusion to be drawn from this work is that multifunctional composite materials can indeed be used for nano-satellite structures and in the same light, can be tailor-made to the speci c mission requirements of the satellite. The technology is in its infancy still and has vast room for improvement and technological development beyond this work and well into the future. Further improvements and additional functions can be added through the inclusion of various other materials.
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Rodier, Bradley J. "Modification of Graphene Oxide for Tailored Functionality." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1515509392532651.
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Henriques, Alexandra J. "Nano-Confined Metal Oxide in Carbon Nanotube Composite Electrodes for Lithium Ion Batteries." FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3169.
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Lithium ion batteries (LIB) are one of the most commercially significant secondary batteries, but in order to continue improving the devices that rely on this form of energy storage, it is necessary to optimize their components. One common problem with anode materials that hinders their performance is volumetric expansion during cycling. One of the methods studied to resolve this issue is the confinement of metal oxides with the interest of improving the longevity of their performance with cycling. Confinement of metal oxide nanoparticles within carbon nanotubes has shown to improve the performance of these anode materials versus unconfined metal oxides. Here, electrostatic spray deposition (ESD) is used to create thin films of nano-confined tin oxide/CNT composite as the active anode material for subsequent property testing of assembled LIBs. This thesis gives the details of the techniques used to produce the desired anode materials and their electrochemical characterization as LIB anodes.
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Bai, Jing. "Percolation study of nano-composite conductivity using Monte Carlo simulation." Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002644.
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Suberu, Bolaji A. "Multi-scale Composite Materials with Increased Design Limits." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377868507.
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Myers, Joshua. "NANO-MATERIALS FOR MICROWAVE AND TERAHERTZ APPLICATIONS." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1450358356.
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Huang, Yaoting. "Fundamental studies on nano-composite phase change materials (PCM) for cold storage applications." Thesis, University of Birmingham, 2019. http://etheses.bham.ac.uk//id/eprint/8844/.
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This thesis studies the thermophysical properties and the phase change behaviour of EG-water and Salt-water based PCMs for cold storage applications, and investigates the role of adding MCNT on the thermophysical properties and the phase change processes. First, the structure of MCNT clusters is linked to the rheological behaviour of the nanofluids by fitting the experimental viscosity data to the modified K-D model. Second, the MCNT cluster information is used to predict thermal conductivity. The effective thermal conductivity of nanofluids not only relies on the particle concentration, but also depends on the particle cluster structure. The specific heat of MCNT nanofluids is decreasing proportionally with the concentration of MCNT. The supercooling degree of EG-water and salt-water based samples can be reduced by adding MCNT particles. The crystallization process of salt-water basefluid and nanofluid was observed and recorded under an optical microscope with cooling stage. Adding MCNT can promote the crystal growth rate.
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Giani, Niccolò <1994>. "Production and characterization of novel thermoplastic (nano)composite materials for additive manufacturing applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10421/1/Giani_Niccol%C3%B2_tesi.pdf.
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The increasing environmental global regulations have directed scientific research towards more
sustainable materials, even in the field of composite materials for additive manufacturing. In this
context, the presented research is devoted to the development of thermoplastic composites for FDM
application with a low environmental impact, focusing on the possibility to use wastes from different
industrial processes as filler for the production of composite filaments for FDM 3D printing. In
particular carbon fibers recycled by pyro-gasification process of CFRP scraps were used as
reinforcing agent for PLA, a biobased polymeric matrix. Since the high value of CFs, the ability to
re-use recycled CFs, replacing virgin ones, seems to be a promising option in terms of sustainability
and circular economy. Moreover, wastes from different agricultural industries, i.e. wheat and rice
production processes, were valorised and used as biofillers for the production of PLA-biocomposites.
The integration of these agricultural wastes into PLA bioplastic allowed to obtain biocomposites with
improved eco-sustainability, biodegradability, lightweight, and lower cost. Finally, the study of novel
composites for FDM was extended towards elastomeric nanocomposite materials, in particular TPU
reinforced with graphene. The research procedure of all projects involves the optimization of
production methods of composite filaments with a particular attention on the possible degradation of
polymeric matrices. Then, main thermal properties of 3D printed object are evaluated by TGA, DSC
characterization. Additionally, specific heat capacity (CP) and Coefficient of Linear Thermal
Expansion (CLTE) measurements are useful to estimate the attitude of composites for the prevention
of typical FDM issues, i.e. shrinkage and warping. Finally, the mechanical properties of 3D printed
composites and their anisotropy are investigated by tensile test using distinct kinds of specimens with
different printing angles with respect to the testing direction.
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Khfagi, Osama Mohamed Ibrahim. "Synthesis of Co-Cr-Mo/ fluorapatie nano-composite coating by pulsed laser depositionfor dental applications." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2259.
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Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2016.Metallic materials play an essential role in assisting with the repair or replacement of bone tissue that has become diseased or damaged. Metals are more suitable for load bearing applications compared to ceramics or polymeric materials due to high mechanical strength and fracture toughness that are exhibited by metallic materials. However, the main limitation in the application of these metallic materials is the release of the toxic metallic ions. The release of these ions is caused by the interaction of metallic materials with human body fluids. These ions react with body tissue, which might lead to various adverse tissue reactions and/or hypersensitivity reactions. Cobalt-chromium-molybdenum (Co-Cr-Mo) alloys are one of the most useful alloys for biomedical applications such as dental and orthopedic implants because of acceptable mechanical properties and biocompatibility. However, the use of these alloys in biomedical applications has of late come under scrutiny recently due to unacceptable revision rates of applications such as hip resurfacing and total hip arthroplasty designs. Failure analysis has demonstrated that solid and soluble wear debris and corrosion products resulted. This release of ions from the joints has resulted in adverse local tissue reactions. Laser-aided deposition is a material additive based manufacturing process via metallurgically bonding the deposited material to the substrate. Due to its capability to bond various materials together, it became an attractive technology. The principal aims of this study were to 1a) fabricate nanocomposite materials by depositing fluorapatite nanopowder onto the Co-Cr-Mo dental alloy using pulsed laser deposition and 1b) evaluate which laser beam energy and layer thickness, based on the exposure time period, would be applicable, and 2) evaluate bioactivity properties on biological material.
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Khan, Abdul Samad. "A novel bioactive nano-composite : synthesis and characterisation with potential use as dental restorative material." Thesis, Queen Mary, University of London, 2009. http://qmro.qmul.ac.uk/xmlui/handle/123456789/441.
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It is desirable for a dental restorative material to have bioactive and bonding properties. This study focuses on the synthesis of a covalently-linked polyurethane/nanohydroxyapatite (PU/nHA) composite and evaluates its chemical, physical, thermal and biochemical characteristics. nHA powder was produced from the sol-gel and novel composite material was chemically prepared by utilising solvent polymerisation. The resulting composites were analysed by chemical, thermal, and mechanical characterisations and electrospun to form fibre mats. The composites were hydrolytically degraded in deionised water and phosphate buffer solution (PBS) and were analysed. Bioactive behaviour was determined in modified-simulated body fluid. The bioadhesion with dentine was analysed in distilled water and artificial saliva. Cell growth and proliferation was measured and number of adhering bacteria was determined and serial dilution followed by plating for colony forming units per disc. Spectral analyses showed the grafted isocyanate and ether peaks on nHA indicating that urethane linkage was established. Covalent-linkage between nHA and PU were found in this novel composite with no silane agent. The physical and thermal properties were enhanced by nHA. These composites had high resistance toward hydrolysis and little degradation was observed. Bioadhesion and bioactivity analysis showed the composite adhered firmly on the tooth surface (dentine) and bond strength was similar to existing obturating material. Higher nHA content composite showed a thicker layer of adhesion. Cells were proliferated although at a lower rate of growth compared to PU, whereas, there was reduction in bacteria adhering to the grafted composite compared to PU. With its low bacterial adhesion and biocompatibility it may provide a promising solution to reduce infections. The electrospun nano-fibres were successfully developed and revealed no loose nHA particles. Hence, this novel composite has the potential to be used as a bioactive dental restorative material.
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Vicentini, Nicola. "Screening on the functionalization of carbon nanostructures and their compatibilization in polymer-based composite materials." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3424578.
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Composites of carbon nanostructures (CNSs) and biocompatible polymers are promising materials for a series of advanced technological applications, ranging from biomedicine and bioelectronics to smart packaging and soft robotics. In this thesis, we present three types of organic functionalized CNSs, namely 4-methoxyphenyl functionalized multi-walled carbon nanotubes, carbon nanohorns and reduced graphene oxide, used as nanofillers for the preparation of homogeneous and well-dispersed composites of poly(l-lactic acid), a biocompatible and biodegradable FDA approved polymer. A thorough characterization of the composites is given in terms of calorimetric response, electrical and mechanical properties. Significant differences are observed among the different types of CNS nanofillers, underlying the key role played by the nanoscale shape, and distribution of the components in driving the macroscopic behavior of the composite material. Surface properties are probed through advanced atomic force microscopy techniques, on both flat substrates (films) and confined systems (nanofibers). All these composites are found to be fully biocompatible when tested as scaffolds for supporting the proliferation, and differentiations of human neuronal precursor cell line SH-SY5Y, and of human Circulating Multipotent stem Cells (hCMCs). Prototypes of Nerve Guide Conduits (NGCs) for in vivo tests were also designed, and obtained using the material based on functionalized Multi Walled Carbon Nanotubes (MWCNTs), and tested on mice, finding promising results. We also propose the functionalization of MWCNTs with “functional” organic groups (4-benzoic acids and styrene), and performed an additional derivatization on them respectively through an amidation reaction, and a “grafting from” polymerization. The so obtained CNSs are promising for the preparation of more complex composite materials. Finally, we analyzed the reaction pathway of the Tour functionalization of CNSs, and we hypothesized that the real reaction scheme could be a balance between two different pathways.Le nanostrutture di carbonio (CNS) e i polimeri biocompatibili sono materiali molto promettenti in un grande numero di applicazioni tecnologicamente avanzate, che vanno dalla biomedicina e bioelettronica, allo smart packaging e alla robotica soft. In questa tesi presentiamo la funzionalizzazione organica tramite addizione della p-metossianilina di 3 diverse CNS: i nanotubi di carbonio a parete multipla, i nanoconi di carbonio e il grafene ossido risotto. Questi materiali sono impiegati come additivi per la preparazione di materiali compositi nanostrutturati a base di acido polilattico (PLLA). In questa tesi è riportata una completa caratterizzazione in termini di proprietà termiche, elettriche e meccaniche. Sono evidenti differenze significative tra le tre nanostrutture e sul loro effetto sulle proprietà dei compositi; ciò sottolinea il ruolo chiave giocato dalla morfologia e forma a livello nanometrico nell’interazione nanostruttura-polimero e quindi nella determinazione delle caratteristiche finali del composito. La superfice dei materiali è stata caratterizzata tramite AFM e CAFM sia nella forma di film piatti sia nella forma di nanofibre ottenute tramite eletrospinning. Sono state quindi testate le proprietà di biocompatibilità e induzione/controllo della differenziazione sia su cellule umane neuronali (SH-SY5Y), sia su cellule staminali umane (hCMCs). I materiali a base di nanotubi di carbonio a parete multipla (MWCNT) ottenuti sono stati utilizzati per la preparazione di prototipi di nerve guide conduits (NGC) per operazioni in-vivo su topi, ottenendo risultati molto promettenti. Presentiamo anche la funzionalizzazione dei MWCNT con 2 gruppi organici “funzionali” (l’acido p-benzoico e lo stirene) sui quali è stata effettuata una derivatizzazione aggiuntiva sfruttando rispettivamente una reazione di ammidazione e una reazione di polimerizzazione “grafting from”. Infine abbiamo analizzato lo schema di reazione della funzionalizzazione di Tour delle CNS a abbiamo ipotizzato che la reale via sintetica sia costituita da due differenti vie in equilibrio tra di loro.
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Noorbehesht, Nikan. "Enhanced Energy Storage and Conversion through Carbon Nanostructured Composites." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15675.
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Experts rank climate change and energy shortage as the most important issues that we confront over the next 50 years. These problems are connected, since non-regenerative fossil fuels are responsible for greenhouse gas emission thanks to the CO2 they produce during combustion. From all the observations, it is evident that these two major global problems concerning energy and the environment must be faced together. Hence, this doctoral work aims to tackle sustainable energy production, conversion, and storage challenges. Graphene and carbon nanotubes (CNTs) have been considered as promising electrode materials for energy conversion and storage due to their unique physical and electrical properties. Considering this fact, a novel nanostructured composite synthesised consisting of graphene and carbon nanotubes (CNTs), each pre-doped with nitrogen (N). This unique composite demonstrated remarkable electrocatalytic activity toward the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and Hydrogen evolution reaction (HER) compared to commercial platinum on supported carbon (Pt/C) catalyst. Therfore, replacing the expensive noble metal catalysts, which offer relatively short service life, with this composite produced from cheap and readily available materials, opens up a new avenue to target sustainable energy production and conversion issues. Employing of this composite to impregnate sulfur into its structure to be used as a cathode in Li-S batteries, and as a support to grow iron and cobalt Oxide (Fe3O4, Co3O4) nanoparticles on its body to be applied in anode for Li-ion batteries, exhibited superior electrochemical performances, including relatively low irreversible capacity loss, high specific capacity, and satisfactory cyclability. This carbon nanostructured composite proved to have a promising potential in sustainable energy storage applications.
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Mohammed, Mohammed K. "Processing and Properties of Multifunctional Two Dimensional Nanocomposites Based on Graphene Nano-Flakes." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1600087340883598.
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Gonciaruk, Aleksandra. "Graphene and triptycene based porous materials for adsorption applications." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/graphene-and-triptycene-based-porous-materials-for-adsorption-applications(932755b9-1600-4f64-8683-00844645a58b).html.
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There were three main driving forces behind this thesis: global concern over climate change mainly due to uncontrolled carbon dioxide (CO2) emissions, the excitement over the discovery of graphene and its versatile potential, and the potential to design three-dimensional (3D) or two-dimensional (2D) structures, in our case using unique triptycene molecule. We examined two polymeric materials for CO2 adsorption and suggested simple design of disordered carbons suitable for gas adsorption studies. The approach in each task was to examine structural and adsorption properties of materials using detailed atomistic modelling employing Monte Carlo and Molecular Dynamics techniques and where possible provide experimental measurements to validate the simulations. The thesis is presented as a collection of papers and the work can be divided into three independent projects. The aim of the first project is to utilize graphene as an additive in polymer composites in order to increase separation between the polymer chains increasing available surface area. The matrix used is a polymer of intrinsic microporosity (PIM-1), which possess large surface area and narrow nano-sized ( > 2nm) pore distribution attractive for gas separation membrane applications. Adding a filler can reduce aging of the polymer, and enhance permeability across the membrane, often to the expense of loosing selectivity. Therefore, we investigated the packing of PIM-1 chains in presence of discrete 2D graphene platelets and 3D graphene-derived structures and its effect on composite structure and adsorption properties. We found that additives do not alter structural polymer properties at the molecular level preserving the same adsorption capacity and affinity. Potential permeability increase would benefit from the retention of selectivity in the material. Building on design philosophy of materials with intrinsic microporosity we continued further investigation of 3D graphene-derived structures. The idea is that highly concave molecules or polymer chains pack inefficiently creating microporous materials with sufficient surface area for gas adsorption. 3D propeller-like structures were derived from graphene arms connected through the rigid triptycene and other types of cores. The resulting structures created a large amount of micropores and showed similar CO2/CH4 selectivity to activated carbons reported in the literature. It was shown that rigid triptycene core leads to more open structures. The model was also applied to model commercially available activated carbon to predict n- perfluorohexane adsorption. The fitting to experimental structural information proved to be challenging due to trial and error nature of the approach. Nevertheless, the simple packing procedure and diverse structure design have a great potential to serve as a virtual model for porous carbons that possess pore complexity and does not require any previous experimental data to be build on. The last project concerns CO2 adsorption and selectivity over CH4 and N2 in recently reported triptycene-based polymer. The triptycene shape polymer can form a porous 2D network that can be exfoliated into free-standing sheets and potentially used as a membrane. Sheets stack in the bulk material forming anisotropic channel pores. Additionally it contains fluoro- functional groups, which are known to have a high CO2 affinity. We explored pore structure and chemistry of stacked material for gas adsorption and predicted comparable capacity and CO2 selectivity to other microporous covalent materials such as activated carbons and PIMs. The CH4/N2 selectivity was similar to currently most selective material belonging to MOF family. We showed that fluoro-group have a positive effect on CO2 affinity, however predictions are sensitive to the charges of fluorine atoms assigned by different methods.
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shieh, Yi jiun, and 謝宜君. "Synthesis and Chacracterization of nano-silver wires/graphene composite materials." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/99232621260551263810.
Full textAbstract:
碩士明新科技大學
化學工程與材料科技系碩士班
103
Graphene is the thinnest and hardest nano-materials. Graphene have unique structure and excellent properties which has a wide range of applications in optoelectronics, gas sensors, capacitor, transparent conductive touch panel, composite and hydrogen storage materials. Metal silver has excellent electrical and thermal conductivity. Nano silver wires (NSWs) with high aspect ratio interlace into the network structure then will increase the conductivity. It is anticipated that replace ITO to use as multi-point touch panel material. In conventional, hydrothermal method was used to synthesis NSWs that need more than 2 hr procedure time. It has time-consuming and complex procedure problems. In this thesis, graphene were synthesized on copper foil by thermal chemical vapor deposition. Wrinkled surface of copper due to copper were deposited on a rotating drum and then peel off to form a rolled foil. The optimal copper substrate electropolishing pretreatment parameters were investigated and then a high quality graphene were obtained. The results show that a high quality graphene can be obtained by copper substrate with 60 min electropolishing pretreatment time, and using PEG/H3PO4 ratio of 1：3. NSWs was rapid synthesize by microwave polyol method. The results show that 0.07 M PtCl2, 0.2 M PVP were added into 0.4 M AgNO3 at 160℃ ,with 2 min reaction time , under 500W power. The high quality nano silver wires were obainted. The NSWs were coated on graphene/ITO to prepare a composite. The addition amount of NSW and procedure parameters was studied to improve the conductivity and transmittance of composite. The optimal results show that 1 mg NSWs were dipping into 3 mL Ethanol, with 5000 rpm spin coating on graphene. Resistance and transmittance of NSWs/graphene composite are 30.55 Ω/□, and 95.47% respectively. It is apparent improvement characteristic properties of graphene thin films.
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Bagotia, Nisha. "Studies on multiwalled carbon nanotube and graphene based polycarbonate/ethylene methyl acrylate nanocomposites." Thesis, 2018. http://eprint.iitd.ac.in:80//handle/2074/7937.
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Dong, S., L. Li, Ashraf F. Ashour, X. Dong, and B. Han. "Self-assembled 0D/2D nano carbon materials enabled smart and multifunctional cement-based composites." 2020. http://hdl.handle.net/10454/18170.
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YesIn this paper, two types of nano carbon materials including 0D nano carbon black and 2D graphene are assembled through electrostatic adsorption to develop smart cement-based composites. Owing to their excellent mechanical, electrical properties and synergistic effect, self-assembled 0D/2D nano carbon materials can form toughening and conductive networks in cement-based materials at low content level and without changing the preparation process of conventional cement-based materials, thus endowing cement-based materials with smart and multifunctional properties including high toughness, self-sensing property to stress/strain and damage, shielding/absorbing property to electromagnetic wave. The developed smart cement-based composites with self-assembled 0D/2D nano carbon materials have promising application in the fields of oil well cementing, structural health monitoring, and electromagnetic protection and anti-electromagnetic pollution. It can therefore conclude that electrostatic self-assembled 0D/2D nano carbon materials provide a simple preparation method and excellent composite effect for developing nano cement-based materials, which can be applied in large-scale infrastructures.
The National Science Foundation of China (51908103) and the China Postdoctoral Science Foundation (2019M651116).
The full-text of this article will be released for public view at the end of the publisher embargo on 22 Nov 2021.
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Wu, Shin Sheng, and 吳信昇. "Size effects of Pt/graphene nano composie materials on mehanol oxdation reaction." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/21047676821690613358.
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碩士長庚大學
化工與材料工程學系
100
In this study, the colloidal platinum nanoparticles with the sizes of13.9 nm, 4.37 nm, 3.54 nm, 2.9 nm, 1.7 nm, 1.3 nm were synthesized. The nanoparticles were loaded on graphene as the catalyst for the methanol oxidation reaction. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and EDX were used to analyze the platinum nanoparticles / graphene composite materials. Furthermore, cyclic voltammetry analysis results showed that the methanol oxidation current is low with a high If / Ib ratio when the platinum nanoparticle size is higher than 2 nm. When the platinum nanoparticle size is between 2 nm and 1 nm, the high methanol oxidation current can be obtained along with the low If / Ib ratio due to the aggregation of platinum particles.
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Kim, Baejung. "Non-Precious Cathode Electrocatalytic Materials for Zinc-Air Battery." Thesis, 2013. http://hdl.handle.net/10012/8102.
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In the past decade, rechargeable batteries attracted the attention from the researchers in search for renewable and sustainable energy sources. Up to date, lithium-ion battery is the most commercialized and has been supplying power to electronic devices and hybrid and electric vehicles. Lithium-ion battery, however, does not satisfy the expectations of ever-increasing energy and power density, which of their limits owes to its intercalation chemistry and the safety.1-2 Therefore, metal-air battery drew much attention as an alternative for its high energy density and a simple cell configuration.1 There are several different types of metal-air batteries that convey different viable reaction mechanisms depending on the anode metals; such as Li, Al, Ca, Cd, and Zn. Redox reactions take place in a metal-air cell regardless of the anode metal; oxidation reaction at the anode and reduction reaction at the air electrode. Between the two reaction, the oxygen reduction reaction (ORR) at the air electrode is the relatively the limiting factor within the overall cell reactions. The sluggish ORR kinetics greatly affects the performance of the battery system in terms of power output, efficiency, and durability. Therefore, researchers have put tremendous efforts in developing highly efficient metal air batteries and fuel cells, especially for high capacity applications such as electric vehicles. Currently, the catalyst with platinum nanoparticles supported on carbon material (Pt-C) is considered to exhibit the best ORR activities. Despite of the admirable electrocatalytic performance, Pt-C suffers from its lack of practicality in commercialization due to their prohibitively high cost and scarcity as of being a precious metal. Thus, there is increasing demand for replacing Pt with more abundant metals due economic feasibility and sustainability of this noble metal.3-5 Two different attitudes are taken for solution. The first approach is by optimizing the platinum loading in the formulation, or the alternatively the platinum can be replaced with non-precious materials. The purpose of this work is to discover and synthesize alternative catalysts for metal-air battery applications through optimized method without addition of precious metals.
Different non-precious metals are investigated as the replacement of the precious metal including transition metal alloys, transition metal or mixed metal oxides, and chalcogenides. These types of metals, alone, still exhibits unsatisfying, yet worse, kinetics in comparison to the precious metals. Nitrogen-doped carbon material is a recently well studied carbon based material that exhibits great potential towards the cathodic reaction.6 Nitrogen-doped carbon materials are found to exhibit higher catalytic activity compared to the mentioned types of metals for its improved conductivity. Benefits of the carbon based materials are in its abundance and minimal environmental footprints. However, the degradation of these materials has demonstrated loss of catalytic activity through destruction of active sites containing the transition metal centre, ultimately causing infeasible stability. To compensate for these drawbacks and other limits of the nitrogen-doped carbon based catalysts, nitrogen-doped carbon nanotubes (NCNT) are also investigated in the series of study.
The first investigation focuses on a development of a simple method to thermally synthesize a non-precious metal based nitrogen-doped graphene (NG) electrocatalyst using exfoliated graphene (Ex-G) and urea with varying amounts of iron (Fe) precursor. The morphology and structural features of the synthesized electrocatalyst (Fe-NG) were characterized by SEM and TEM, revealing the existence of graphitic nanoshells that potentially contribute to the ORR activity by providing a higher degree of edge plane exposure. The surface elemental composition of the catalyst was analyzed through XPS, which showed high content of a total N species (~8 at.%) indicative of the effective N-doping, present mostly in the form of pyridinic nitrogen groups. The oxygen reduction reaction (ORR) performance of the catalyst was evaluated by rotating disk electrode voltammetry in alkaline electrolyte and in a zinc-air battery cell. Fe-NG demonstrated high onset and half-wave potentials of -0.023 V (vs. SCE) and -0.110 V (vs. SCE), respectively. This excellent ORR activity is translated into practical zinc-air battery performance capabilities approaching that of commercial platinum based catalyst.
Another approach was made in the carbon materials to further improve the cost of the electrode. Popular carbon allotropes, CNT and graphene, are combined as a composite (GC) and heteroatoms, nitrogen and sulfur, are introduced in order to improve the charge distribution of the graphitic network. Dopants were doped through two step processes; nitrogen dopant was introduced into the graphitic framework followed by the sulfur dopant. The coexistence of the two heteroatoms as dopants demonstrated outstanding ORR performance to those of reported as metal free catalysts. Furthermore, effects of temperature were investigated through comparing ORR performances of the catalysts synthesized in two different temperatures (500 ??? and 900 ???) during the N-doping process (consistent temperature was used for S-doping). Through XPS analysis of the surface chemistry of catalysts produced with high temperature during the N-doping step showed absence of N-species after the subsequent S-doping process (GC-NHS). Thus, the synergetic effects of the two heteroatoms were not revealed during the half-cell testing. Meanwhile, the two heteroatoms were verified in the catalyst synthesized though using low temperature during the N-doping process followed by the S-doping step (GC-NLS). Consequently, ORR activity of the resulting material demonstrated promising onset and half-wave potentials of -0.117 V (vs. SCE) and -0.193 V (vs. SCE).
In combination of these investigations, this document introduces thorough study of novel materials and their performance in its application as ORR catalyst in metal air batteries. Moreover, this report provides detailed fundamental insights of carbon allotropes, and their properties as potential elecrocatalysts and essential concepts in electrochemistry that lies behind zinc-air batteries. The outstanding performances of carbon based electrocatalyst are reviewed and used as the guides for further direction in the development of metal-air batteries as a promising sustainable energy resource in the future.
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Hsueh, Wei-Jung, and 薛蔚榮. "A Study on the Flame Retarded Properties of PMMA Composite Materials by Synthesis Method with Expandable Graphite and Nano Mica." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/avzxf7.
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碩士國立臺北科技大學
有機高分子研究所
99
Ammonium salt was used to modify the nano mica and expandable graphite powder (EG) with the different particle sizes in this study. Furthermore, EG and mica were added into Methyl Methacrylate (MMA) to synthesize PMMA/EG/mica composites. The compression molding was used to fabricate the PMMA/EG/mica composites and carry on the various test of physical and chemical properties. Through the flame retardant testing results showed that PMMA/EG/mica composites with the same particle size and loadings have the better flame retardant performance. However, the composites with larger particle size EG have significant performance. Otherwise, the chemical properties variation was tested by FT-IR. Finally, the surface morphology of PMMA/EG/mica composites was observed by SEM and thermal properties analysis was used by DSC instrument.
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Lin, Wei-Fu, and 林韋甫. "Polythiophene block copolymer and nano-composite materials." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/235r9p.
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碩士國立臺北科技大學
有機高分子研究所
99
Polythiophene is an important polymer,which can be used in OLED,feed effect transistor,and solar-cells.In this experiment, Thiophene with carboxylate functional groups are copolymerized with thiophene.Different compositions of random copolymers are synthesized in this research. Alternating copolymer are also synthesized. It is found that the alternating copolymer manifest excellent electrical conductivity. Their physical properties and elucidated by UV,NMR,and FTIR. The optoelectronic applications of the polythiophene will be elucidated.
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Zhang, Fan. "Experimental Study of Nano-materials (Graphene, MoS2, and WSe2)." Thesis, 2018. https://doi.org/10.7916/D8PV6XZV.
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Since the successful isolation of graphene in 2004, two-dimensional (2D) materials have become one of the hottest research fields in material science. My research is about two kinds of popular 2D materials--graphene and transition metal dichalcogenides (TMDCs).
Making graphene into nanoribbons has been predicted and demonstrated to be an effective way to open a bandgap in this pristinely zero-bandgap 2D material. But the rough edge condition of etched graphene nanoribbons has always been a big issue adversely affecting electron transport performance. The electron mean free path of this kind of devices is usually way below the channel width. By using a dual-gate structure based on bilayer graphene/hexagonal boron nitride heterostructure, we found a way to form 300nm-wide conducting channels with high aspect ratio (>15) that can achieve ballistic transport, indicating perfect edge conditions.
As the first star member of TMDCs family, monolayer MoS2 is predicted to be strongly piezoelectric, an effect that disappears in the bulk owing to the opposite orientations of adjacent atomic layers. We conduct the first experimental study of the piezoelectric properties of two-dimensional MoS2 and show that cyclic stretching and releasing of thin MoS2 flakes with an odd number of atomic layers produces oscillating piezoelectric voltage and current outputs, whereas no output is observed for flakes with an even number of layers. In agreement with theoretical predictions, the output increases with decreasing thickness and reverses sign when the strain direction is rotated by 90 degrees. Transport measurements show a strong piezotronic effect in single-layer MoS2, but not in bilayer and bulk MoS2.
Monolayer WSe2, another popular TMDC, has also attracted much recent attention. In contrast to the initial understanding, the minima of the conduction band are predicted to be spin split. Because of this splitting and the spin-polarized character of the valence bands, the lowest-lying excitonic states in WSe2 are expected to be spin-forbidden and optically dark. We show how an in-plane magnetic field can brighten the dark excitonic states and allow their properties to be revealed experimentally in monolayer WSe2. In particular, precise energy levels for both the neutral and charged dark excitons were obtained. Greatly increased emission and valley lifetimes were observed for the brightened dark states as a result of their spin configuration.
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Lee, Hsi Ming, and 李溪銘. "Oligoaniline – Graphene / Silver Nanowires and Aliphatic Polyurethane Composite Materials." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/cpa3xp.
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碩士國立臺北科技大學
有機高分子研究所
101
The study commences with the synthesis of tetraaniline by dianiline as monomer and FeCl3 as oxidant. The prepolymer was reacted with ether-type poly(tetramethyleneglycol) (PTMO) as the soft segments with molecular weight of 2900 and 1,6-hexamethylene diisocyanate (HDI) as the hard segments. Then using triethylamine as catalyst, the tetraaniline can connect the short chains end to end of the prepolymers into copolymer. By this method, we can enhance the intensity of bulk polyaniline. After dissolving the synthetic product copolymer with solvent dimethylformamide (DMF), we then add certain amount of graphene and silver nanowires as additional agent to increase the electrical conductivity. At the final step, Dodecyl benzene sulfonic acid (DBSA) is added as dopant agent. After drying, the membranous nano-composite copolymer has the properties of elasticity and electrical conductivity. We are able to obtain the chemical structures of the copolymer and polyurethane by FT-IR, the properties and glass transition temperature (Tg) of the copolymer by dynamic mechanical analysis, and creep-recovery behavior by Burger’s model simulation, retardation time of copolymer large than polyurethanes,beacause of teraaniline reduced the elastic behavior. In addition, we can examine the electrical conductivity aroused by graphene and silver nanowires through an impedance measurement method, and test the stretching conductivity with ohmmeter. From the result, we learned that the copolymer has the highest conductivity 6.12x10-2 S/cm as 3% silver nanowires within. Also, the conductivity rises as the stretching rate increases.
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Cheng, Ke-Siang, and 程科翔. "Development of supercapacitors using RuO2/Graphene/Polyaniline composite materials." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/fn74fz.
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Lin, Chih Wen, and 林志文. "Graphene-based Composite Materials for Cancer Diagnosis and Therapy." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/j8a5wu.
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博士國立清華大學
化學工程學系
104
The objectives of this research are the preparation of drug / gene delivery vector and the biological sensor electrode materials by utilizing different modified graphenes, which can be applied to cancer therapy and diagnosis. The performances of different modified graphenes for the treatment of brain tumors and the detection ability of prostate cancer, brain tumors have been investigated. There are six chapters in this dissertation. The first chapter describes the development of a statistical analysis of cancer, cancer treatment and diagnosis, and the proposed method for preparation the graphene material. The second chapter introduces the basic theory of graphene composites and reviews the related literatures redarding the brain tumor therapy and magnetic graphene biosensor. The third chapter focuses on the research on the gadolinium-functionalized nanographene oxide for combined drug and microRNA delivery and magnetic resonance imaging. The fourth chapter discusses on the study on the combined detection of cancer cells and a tumor biomarker using an immunomagnetic sensor for the improvement of prostate-cancer diagnosis. The fifth chapter studies the investigation on the use a magnetic graphene biosensor to detect blood levels of vascular endothelial growth factor as the diagnosis of brain tumors. The sixth chapter is the general conclusions of this dissertation. 1.Gadolinium-functionalized nanographene oxide for combined drug and microRNA delivery and magnetic resonance imaging The delivery of anti-cancer therapeutics to tumors at clinically effective concentrations, while avoiding nonspecific toxicity, remains a major challenge for cancer treatment. The first part of this thesis presents the nanoparticles of gadolinium-functionalized nanographene oxide (Gd-NGO) can be used as effective carriers to deliver both chemotherapeutic drugs and highly specific gene-targeting agents such as microRNAs (miRNAs) to cancer cells. The positively charged surface of Gd-NGO was capable of simultaneous adsorption of the anti-cancer drug epirubicin (EPI) and interaction with negatively charged Let-7g miRNA. Using human glioblastoma (U87) cells as a model, we found that this conjugate of Let-7g and EPI (Gd-NGO/Let-7g/EPI) not only exhibited considerably higher transfection efficiency, but also induced better inhibition of cancer cell growth than Gd-NGO/Let-7g or Gd-NGO/EPI. The concentration of Gd-NGO/Let-7g/EPI required for 50% inhibition of cellular growth (IC50) was significantly reduced (to the equivalent of 1.3 mg mL−1 EPI) compared to Gd-NGO/EPI (3.4 mg mL−1 EPI). In addition, Gd-NGO/Let-7g/EPI could be used as a contrast agent for magnetic resonance imaging to identify the location and extent of blood-brain-barrier opening and quantitate drug delivery to tumor tissues. These results suggest that Gd-NGO/Let-7g/EPI is a promising non-viral vector for chemogene therapy and molecular imaging diagnosis in future clinical applications. 2.Combined detection of cancer cells and a tumor biomarker using an immunomagnetic sensor for the improvement of prostate-cancer diagnosis Prostate cancer (PCa) is the second most common cancer in men worldwide. In addition, the incidence of prostate carcinoma increases with age-more rapidly than any other cancers. The development of assays for the early and accurate detection of PCa is therefore of utmost importance. The second part of this thesis introduce a simple, low-cost method for Capture and detection of both a relevant PSMA and CWR22R PCa cells are demonstrated using magnetic graphene oxide (MGO) possessing conjugated antibodies. By simply dropping the MGO onto the surface of Pt electrodes while in a magnetic field, MGO-PSMAab-modified Pt sensor is rapidly constructed. The detection limit for PSMA was 10 pg mL−1 and 46 CWR22R PCa cells per sensor, and the amount of PSMA detected was close to that measured by ELISA. The dual approach of the sensor potentially offers a more accurate, rapid platform than current tests based on immunological methods. 3.Using a magnetic graphene biosensor to detect blood levels of vascular endothelial growth factor as the diagnosis of brain tumors Currently, the diagnosis of brain tumors in the body examination with medical diagnostic imaging. However, it is great needed to develop a technology in vitro diagnosis rapidly for early diagnosis of brain tumors. The third part of this thesis, a reusable biosensor was proposed based on a magnetic graphene oxide (MGO)-modified Au electrode to detect vascular endothelial growth factor (VEGF) in human plasma for brain tumor diagnosis. In this biosensor, Avastin is used as the VEGF biorecognition element, and MGO is used as the carrier for Avastin loading. The use of MGO enables rapid purification due to its magnetic properties, which prevents the loss of bioactivity. Moreover, the biosensor can be constructed quickly, without requiring a drying process, which is convenient for proceeding to detection. Our reusable biosensor provides the appropriate sensitivity for clinical diagnostics and has a wide range of linear detection, from 31.25-2000 pg mL−1, compared to ELISA analysis. In addition, 100% serum of experiments were obtained from clinical samples, readouts from the sensor and an ELISA for VEGF showed good correlation within the limits of the ELISA kit. The relative standard deviation (RSD) of the change in current (ΔC) for reproducibility of the Au biosensor was 2.36% (n=50), indicating that it can be reused with high reproducibility. Furthermore, the advantages of the Avastin-MGO-modified biosensor for VEGF detection are that it provides an efficient detection strategy that not only improves the detection ability but also reduces the cost and decreases the response time by 10-fold, indicating its potential as a diagnosis product for brain tumor.
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Wang, Chi-Wei, and 王淇威. "Electrospun Graphene Composite Fibers for Electrode Materials of Supercapacitors." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/11269913155422914126.
Full textAbstract:
碩士逢甲大學
綠色能源科技碩士學位學程
101
The major task involved in this study has twofold: (a) fabrication graphene composite fibers by electrospinning process (ESP) and (b) manufacturing and characterization of a supercapacitor electrode using activated graphene composite fibers by adding acetylene carbon black and PVDF solution. The size distribution of graphene composite fibers were adjusted by PVA concentration, applied electric field, work distance, flow rate of PVA/graphene suspension, needle specifications during the ESP process and carbonization temperature after the ESP process. The results showed that graphene composite fibers with avg. dia. of 73~225 nm were derived from ESP under a flow rate of 0.1 ml/hr of mixture of 1 ml graphene oxide aqueous solution (6 wt%) and 2 ml polyvinyl alcohol (PVA) aqueous solution (15 wt%) to be electrosprayed through a syringe needle of 0.5 inch long and 0.84 mm diameter under applied working voltage of 10 kV at a working distance of 10 cm. The crystalline phase and microstructure of acquired graphene composite nanowires and nanofibers were analyzed by FESEM, EDS, XRD and Raman spectroscopy. Under the electrochemical testing conditions of 1 M H2SO4 electrolyte and C-V scan rate of 25 mV/s, the optimized specific capacitance of electrical double-layer capacitors of such eletrospun graphene composite fibers was 33.19 F/g, which was enhanced to be 44 F/g when the chemically activated graphene composite fibers were applied.
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Wang, FU-KAI, and 王富凱. "Study on Amorphous MnO/Graphene/Nano-carbon Composite as Supercapacitor Electrodes." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8h6tnm.
Full textAbstract:
碩士國立勤益科技大學
化工與材料工程系
106
Among many energy storage devices, supercapacitors are devices with high charge and discharge efficiency, high power density, and high cycle life. On the electrode material, graphene has excellent thermal conductivity, electrical conductivity and high specific surface area, which has become one of the most popular materials for super capacitor research. However, graphene itself has the property of self-aggregation and interface resistance, resulting in a decrease in its specific surface area, which makes it unable to exhibit excellent capacitance performance. As a result, the application of graphene to supercapacitors is still one of the main reasons for academic research and commercialization. In this study, the nanocomposites of amorphous manganese oxide/graphene/carbon nanotubes were synthesized by hydrothermal synthesis method using polyol reduction method. The use of manganese oxide to adhere the carbon nanotubes to the graphene, to avoid the phenomenon of its own aggregation, to provide better pore and interface properties to maximize the contact of the electrolyte and the material, increase the specific capacitance. In the 1 M Na2SO4 electrolyte, excellent specific capacitance (210F/g) characteristics are exhibited; at a current of 1 A/g, the specific capacitance of all components can reach 33 F/g. The results show that the amorphous manganese oxide/graphene/carbon nanotubes developed by the institute are potential capacitive materials and help to break through the bottleneck of the commercial application of graphene in supercapacitors.
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Beladi, Mousavi Seyyed Mohsen. "Organometallic Polymer - Graphene Nanocomposites: Promising Battery Materials." Doctoral thesis, 2017. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2017012715280.
Full textAbstract:
Preparation, structural analysis, and electrochemical performance of a new cathodic battery material, consisting of a nanocomposite of poly(vinylferrocene) (PVFc) (Eox: 0.4 V vs. Ag/AgCl) and reduced graphene oxide (rGO), are described. The nanocomposite shows the highest charge-discharge efficiency (at a rate of 100 A g-1) ever reported for any organic / organomatellic battery material. Remarkably, the composite is “thickness scalable” up to 0.21 mAh cm-2 (770 mC cm−2 at 29 μm film thickness) on a flat surface with > 99% coloumbic efficiency, exhibiting a specific capacity density of 114 mAh g−1. The composite material is binder free and the charge storing material (PVFc) accounts for > 88% of the total weight of the cathodic material. The secret behind such a performance is the electrostatic interaction between the redox polymer in its oxidized state (exhibiting positive charge) and the original filler i.e., graphene oxide (GO) with negative surface charge. This self-assembling step is analyzed by zeta potential measurements, and a modeling study confirms the experimentally found heavy polymer loading on the GO (in aqueous solution). The efficient self-assembly led to composites with high ratio of redox polymer / GO where all polymers are in close contact with GO sheets. The stable colloidal solution was casted on the surface of a flat current collector and the insulating GO was electrochemically transformed to conductive reduced graphene oxide (rGO). The GO / rGO transformation was catalyzed by methyl viologen dichloride (MV++) working as a redox shuttle (solublized in the aqueous electrolyte) and thereby accelerating the electron transfer to GO. Complete GO / rGO transformation and the quantitative ion breathing of the composite are found by means of electrochemical quartz crystal microbalance and electrochemical AFM.
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McIntosh, Ross William. "Quantum transport through impurity clusters in carbon nano-materials." Thesis, 2014.
Find full textAbstract:
Modified graphene and low dimensional carbon nano-electronic devices have the potential to supersede current technologies in many respects although manufacturing and understanding these materials poses a significant challenge which requires an incremental approach. Doping of graphene, a prerequisite for modifying the electronic properties, is still poorly understood.Band-modulation is therefore difficult to control. Resonant tunneling induced through the incorporation of impurity clusters has not yet been addressed. On the other hand electronspin correlations in modified graphenes have hardly been studied. In this work we address these issues through a tandem approach of theoretical and experimental studies. This work begins with an ab-initio study of the electronic properties of bilayer graphene and the modifications induced through the substitutional incorporation of isolated nitrogen impurities.Nitrogen modification results in a change from a zero-gap semiconductor to a metal as a result of nitrogen incorporation while charge density calculations show the localization of charge in the vicinity of the impurity. This work on isolated impurities was then extended to impurity clusters.
The quantum transport properties of impurity clusters distributed within a high bandgap
material were then studied. Different geometrical configurations of the impurity clusters were studied to tune quantum interference to control the carrier lifetime. The effects of randomly distributed clusters were also studied to interpret the effects of disorder. These studies provide insight into the transport properties of naturally grown quantum dot systems such as reduced graphene oxide which consists of low defect density graphene nano-islands randomly distributed in oxygen and free radical functionalized graphene which was studied experimentally. Resistance was recorded as a function of temperature for graphene oxide and reduced graphene oxide two terminal devices. Evidence of mesoscopic resistance fluctuations, charge carrier activation and enhanced elastic scattering was found while the magnetic properties of reduced graphene oxide showed a phase transition from ferromagnetism at low temperatures to diamagnetism at higher temperatures.
Finally, the Kondo effect was demonstrated in reduced graphene oxide through transport
and magnetoresistance measurements which were interpreted within the Fermi liquid
description of the Kondo effect. These effects were explained through the microstructure
of reduced graphene oxide and illustrate the significance of spin in reduced graphene oxide. These studies will inform the design of functionalized graphene spin-polarized devices and spin valves.