Дисертації з теми "Graphene dispersion"
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Wei, Jiacheng. "Graphene in epoxy system : dispersion, preparation and reinforcement effect." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36264/.
Повний текст джерелаO'Driscoll, Luke James. "New responsive surfactants for aqueous dispersion of CNTs and graphene." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10647/.
Повний текст джерелаRodgers, Andrew Norman John. "Dispersion, assembly and electrochemistry of graphene at the liquid-liquid interface." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/dispersion-assembly-and-electrochemistry-of-graphene-at-the-liquidliquid-interface(c2ffd27a-cf5f-45c2-a471-60dcab788e12).html.
Повний текст джерелаPhan, Anh Duc. "Graphene Casimir Interactions and Some Possible Applications." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4386.
Повний текст джерелаPeixoto, Renato de Oliveira. "Estudo de propriedades vibracionais em sistema de baixa dimensionalidade /." Rio Claro, 2019. http://hdl.handle.net/11449/182253.
Повний текст джерелаResumo: Neste trabalho, tivemos como objetivo obter a dispersão de fônons de materiais bidimensionais, por meio de simulações de dinâmica molecular clássica, a fim de examinar propriedades mecânicas e elásticas, como a velocidade do som, módulo volumétrico, módulo de cisalhamento, coeficiente de Poisson e módulo de Young. Apresentamos as principais características da ferramenta utilizada na investigação, o método de dinâmica molecular clássica. Abordamos o Algoritmo Velocity Verlet, empregado para a integração das equações de movimento; o Ensemble estatístico, utilizado para realizar as simulações; o termostato de Nosé-Hoover, responsável por regular a temperatura do sistema; e os potenciais que descrevem as interações atômicas. Utilizamos potenciais reativos, sendo eles Tersoff, Tersoff-2010, AIREBO e ReaxFF. As simulações computacionais foram realizadas através do software LAMMPS. Além disso, discorreremos sobre a dinâmica de rede, a obtenção das curvas de dispersão a partir da construção da matriz dinâmica, por meio da matriz dos coeficientes de rigidez baseado nos deslocamentos dos átomos. Os materiais de baixa dimensionalidade investigados nesta dissertação são derivados do carbono como o grafeno, grafeno bifenileno – BPC e nanotubos. As propriedades vibracionais e elásticas calculadas, para o grafeno foram comparadas com resultados experimentais para o grafite no plano e resultados de simulações de dinâmica molecular. O grafeno bifenileno e os nanotubos de carbono foram compara... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In this work, we aimed to obtain the phonon dispersion of two-dimensional materials by classical molecular dynamics simulations, in order to explore mechanical and elastical properties, such as velocity of sound, volumetric modulus, shear modulus, Poisson's ratio, and Young's modulus. We present the main features of the tool used in the research, the classical molecular dynamics method. We approach the Velocity Verlet Algorithm, used for the integration of the equations of motion; the statistical Ensemble, used to perform the simulations; Nosé-Hoover’s thermostat, responsible for regulate the system temperature; and the potentials that describe the atomic interactions. We used reactive potentials, being Tersoff, Tersoff-2010, AIREBO and ReaxFF. The computational simulations were performed through LAMMPS software. In addition, we will discuss lattice dynamics, the obtaining the dispersion curves from the dynamic matrix construction, through the matrix of stiffness coefficients based on the displacements of the atoms. The low-dimensional materials investigated in this dissertation are derived from carbon such as graphene, graphene biphenylene - BPC and nanotubes. The calculated vibrational and elastical properties for graphene were compared with experimental results for graphite in-plane and results of molecular dynamics simulations. Graphene biphenylene and carbon nanotubes were compared with graphene values. The other materials, biphenylene nanotubes, were compared with carbo... (Complete abstract click electronic access below)
Mestre
Lagier, Laura. "Ecotoxicité comparative de l'oxyde de graphène et d'autres nanoparticules de carbone chez des organismes aquatiques modèles : d'une évaluation en conditions monospécifiques vers l'étude d'une chaîne trophique expérimentale." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30270/document.
Повний текст джерелаThe ecotoxicity of different carbon-based nanoparticles (CNPs) was assessed in freshwater organisms, especially in Xenopus laevis. The surface of the CNPs was shown to be the more relevant parameter to describe the growth inhibition in Xenopus, regardless of their allotropic form and their state of dispersion. Micronucleus induction was also studied in Xenopus and graphene oxide (GO) was found genotoxic at low dose. This result was in compliance with the study of genes expression. The involved toxicity mechanisms would be related to the oxidized functions of the CNP. Moreover, GO was also found responsible for genotoxicity in Pleurodeles waltl. and for teratogenicity, development delay and growth inhibition in Chironomus riparius. These organisms have finally been put together in a mesocosm, which has also led to genotoxicity in Pleurodeles in the presence of GO
Brandenburg, Ricardo Fischer. "Nanocompósitos de polietileno com grafenos ou nanotubos de carbono." Universidade do Estado de Santa Catarina, 2014. http://tede.udesc.br/handle/handle/1653.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
The dispersion of carbon nanoparticles in polymer matrices has been studied by many researchers. This paper used nanoparticles of carbon nanotubes and graphene, in high density polyethylene matrix, making use of solution dispersion and melt dispersion. The solution dispersion used as solvent 1,2 dichlorobenzene and the melt dispersion was performed with torque rheometer. Analysis of Differential Scanning Calorimetry, Thermogravimetry, Size Exclusion Chromatography, Raman Spectroscopy, Infrared Spectroscopy Fourier Transform , analyzes of torque in the melt dispersion, nanoindentation to determine nanohardness and elastic modulus, Vickers hardness, Transmission Electron Microscopy, and Scanning Electron Microscopy with Field Emission. It was found that there was no significant change in melting temperature and crystallization of the nanocomposites. No significant change was identified in thermogravimetric analysis. The results of the elastic modulus demonstrate 22.8% increase in the use of carbon nanotubes for both methods of dispersion. The results obtained in graphene nanocomposites show that the dispersion method directly affects the properties of the nanocomposites. There was a 14% increase in tensile modulus for composites with 1% solution by graphene dispersed and scattered compositions with 5 % in melt dispersion. Analysis of Transmission Electron Microscopy and Scanning Electron Microscopy with Field Emission confirm dispersion states of carbon nanotubes dispersed by fusion , and agglomerated states of graphene in both dispersion processes, with smaller nanoplateletes of the solution dispersion compared to the melt dispersion. Crystallinity index showed similar levels in nanocomposites with carbon nanotubes and differentiated for nanocomposites with graphene, which reduces the degree of crystallinity compared to pure polymer matrix values.
A dispersão de nanopartículas de carbono em matrizes poliméricas tem sido objeto de estudo de diversos pesquisadores. Este trabalho utilizou nanopartículas de nanotubos de carbono e grafenos, em matriz de polietileno de alta densidade, fazendo-se uso de dispersão por solução e dispersão por fusão. A dispersão por solução utilizou como solvente 1,2 diclorobenzeno e a dispersão por fusão foi realizada com reômetro de torque. Foram realizadas análises de Calorimetria Diferencial Exploratória, Termogravimetria, Cromatografia de Exclusão por Tamanho, Espectroscopia RAMAN, Espectroscopia no Infravermelho com Transformada de Fourier, análises de torque na dispersão por fusão, nanoindentação para determinação de módulo de elasticidade e nanodureza, microdureza Vickers, Microscopia Eletrônica de Transmissão e Microscopia Eletrônica de Varredura com Emissão de Campo. Verificou-se que não há alteração significativa da temperatura de fusão e de cristalização dos nanocompósitos obtidos. Não foi identificado alteração significativa do comportamento térmico no ensaio de termogravimetria. Os resultados do módulo de elasticidade demonstram aumento de 22,8% na utilização de nanotubos de carbono, para os dois métodos de dispersão. Os resultados obtidos nos nanocompósitos com grafenos demonstram que o método de dispersão interfere diretamente nas propriedades dos nanocompósitos. Houve aumento de 14% no módulo de elasticidade para composições com 1% de grafeno dispersados por solução e para composições com 5% dispersados por fusão. As análises de Microscopia Eletrônica de Transmissão e Microscopia Eletrônica de Varredura com Emissão de Campo confirmam estados de dispersão de nanotubos de carbono dispersados por fusão, e estados aglomerados de grafenos em ambos os processos de dispersão, havendo dimensões menores dos nanoplateletes na dispersão por solução, em comparação à dispersão por fusão. Os índices de cristalinidade apresentaram teores semelhantes nos nanocompósitos com nanotubos de carbono e valores diferenciados para os nanocompósitos com grafenos, com redução do grau de cristalinidade em relação à matriz polimérica pura.
Závacký, Jakub. "Technologie úpravy nanočástic pro zlepšení jejich dispergovatelnosti pro využití v cemtových kompzitech." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2021. http://www.nusl.cz/ntk/nusl-432484.
Повний текст джерелаPacltová, Klára. "Ověřování vlastností betonů s nanočásticemi." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392361.
Повний текст джерелаEneborg, Alexander. "Improvement and Characterization of Aqueous Graphene Dispersions." Thesis, KTH, Tillämpad fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-248004.
Повний текст джерелаDobson, Benjamin Pirnie. "Dispersions of graphene for use as thermal and functional fluids." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12570/.
Повний текст джерелаCardoch, Sebastian. "Studying Atomic Vibrations by Transmission Electron Microscopy." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305370.
Повний текст джерелаAlfonso, Marco Salvatore. "Liquid carbon dispersions for energy applications." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0240/document.
Повний текст джерелаThe aim of this work is to develop and study a new class of smart fluids made of colloidalcarbon-based dispersions, which are sensitive to an external stimulus for energy storage orconversion applications. The effect of an external input, such as mechanical vibration, humanmotion, variable pressure, flowing of a solvent, can alter the structures of such systems.Consequently these changes induce modifications of the dielectric and electrical properties. Usually,the suspensions of carbon materials are investigated at rest or dried. However, their flow behavior iscritical when new technologies, which exploit these materials in dynamic conditions such as FAES(Flow-Assisted Electrochemical Energy Storage) are considered. For example, graphene-basedmaterials are now playing a significant role in energy materials. They act as conductive additives inelectrode assemblies, but due to their specific anisotropic shape they also provide a new route toachieve dielectric liquid media.In details, Graphene Oxide liquid crystals as electrostrictive soft material for mechanical energyharvesting and Carbon black dispersions as percolated flowable electrodes for capacitive energystorage are investigated.In particular, the dielectric and electrical properties of these flowable dispersions are studied understatic and dynamic conditions. The effect of the flow-rate on the local orientation and reorganizationof the particles and their related dielectric and electrical behavior are examined
Zhang, Zhaopeng. "Research into order parameters and graphene dispersions in liquid crystal systems using Raman spectroscopy." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/research-into-order-parameters-and-graphene-dispersions-in-liquid-crystal-systems-using-raman-spectroscopy(c7ccd62e-817b-4d82-b9e1-68be43f28ff5).html.
Повний текст джерелаJames, Candace M. "The dispersion and delamination of graphite in PETI298 by High Torque Melt Mixing." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2012. http://digitalcommons.auctr.edu/dissertations/315.
Повний текст джерелаTölle, Folke Johannes [Verfasser], and Rolf [Akademischer Betreuer] Mülhaupt. "Bindemittelfreie Graphen-Dispersionen aus Graphit und Graphitoxid für Katalyse und Polymer-Nanokomposite." Freiburg : Universität, 2013. http://d-nb.info/1123478473/34.
Повний текст джерелаAllard, Adrien. "Étude ab initio des phonons du graphène sur substrats métalliques." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10174/document.
Повний текст джерелаThe fabrication of high quality large-area graphene films is one of the biggest problem. Recently, the synthesis by chemical vapor deposition of hydrocarbons over a metallic substrate have shown promising results. To manage as well as possible the transfer process of the graphene layer in an insulator, it is important to know the interaction strength between the graphene layer and the metallic substrate. We propose in this paper to calculate the phonon dispersion of an adsorbed graphene. The phonon dispersion of graphene is known to display two strong Kohn Anomalies (kinks) in the highest optical branch (HOB) at the high-symmetry points Gamma and K. The phonon slope around the Kohn anomalies is related to the electron-phonon-coupling (EPC) with the graphene pi bands. We show that this EPC, which has strong impact, for example, on Raman scattering and electron transport, can be strongly modified due to interaction with a metallic substrate. For graphene grown on a Ni(111) surface, our ab initio calculations show a total suppression of the Kohn anomaly ; the HOB around Gamma and K becomes completely flat. This is due to the strong hybridization of the graphene pi-bands with the nickel d-bands that lifts the linear crossing of the pi bands at K. Raman spectroscopy and low-energy electron diffraction are quick and reliable methods to characterize graphene on metallic substrates. Our results show how to obtain additional information, by means of vibrational and photoemission spectroscopy, on the chemisorption or physisorption of graphene layers on metal surfaces
Klimentová, Jiřina. "Optimalizace procesu tepelného zpracování LKG legovaných niklem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229066.
Повний текст джерелаPavloušková, Zina. "Využití homogenizačního žíhání k potlačení segregace křemíku a niklu v LKG." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233926.
Повний текст джерелаWang, Wei-Ping, and 王惟平. "Dispersion of Graphene/NSP nanohybrid for anti-staticapplications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/4v64kw.
Повний текст джерела國立臺灣大學
高分子科學與工程學研究所
105
The interaction between the platelet-like materials of graphene and nano silicate platelet (NSP) was studied for antistatic applications. Two different source of graphite, electronic graphite and CPC graphite-like materials were compared for illustrating the dispersion mechanism involving the effect of the silicate platelet (NSP) presence. It was discovered that CPC graphite-like with the properties of oleophilic could be well dispersed in aqueous medium. Furthermore, the amphiphilic property and irreversibly dispersion behaviour either in water or in toluene, depending on the exposing order, were achieved for the graphene/NSP nanohybrid. The mechanism involved micelle-like microstructure of oil-in-water and water-in-oil forms. Low molecular weight of POEM (s-POEM), compared with home-made dispersant poly(oxyethylene)-segmented imide (POEM), was synthesized for affecting the dispersibility and long term stability of graphene. As prepared graphene/NSP nanohybrid was solution blending with WPU to form graphene/NSP/WPU nanocomposites film. The comparison among graphene/WPU, NSP/WPU and graphene/NSP/WPU was made. In the absence of NSP, graphene showed sedimentation in the bottom of composite film and resulted in the uneven performance of sheet resistance. The presence of NSP prevented graphene from sedimentation, leading to the Graphene/NSP/WPU nanocomposites, shown the sheet resistance from larger than 1012 of pristine WPU, to 107 ohm/sq with uniform electrical property in both side of film. These graphene/NSP/WPU composites can well meet the requirement of antistatic uses.
黃宣詠. "Effects of Surfacant on Dispersion of Graphene in Surfacant Aqueous Solutions." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/86244971380255169102.
Повний текст джерелаSyu, Jian-Wei, and 徐堅偉. "Preparation and Mechanical Properties of Graphene Nanoplatelets/Epoxy Nanocomposite via Rapid Dispersion Process." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/b3nu5c.
Повний текст джерела中華科技大學
飛機系統工程研究所
106
Nanomaterials were dispersed in epoxy resin by using ultrasonicationor mechanical stirring is the main method of nanocomposite prepared.However, the above process often takes hours or even longer, which is notcost-effective for future production in the industry. Therefore, this studyhopes to prepare nanocarbon material/epoxy nanocomposites via a rapidly and simple dispersing process. In this study, the preparation method and mechanical properties of graphene nanoplatelets/epoxy nanocomposites were investigated by planetary dispersion method. The graphene nanoplatelet(GNPs) containing different proportions(0.1, 0.25, 0.50, and 1.0 wt%)were used to reinforce epoxy resin to enhance their mechanical properties of nanocomposites.The experimental results showed that the mechanical properties of the nanocomposies steadily improved with 0.1~0.25 wt% GNPs added.Furthermore, the solution of epoxy resin containing the GNPs on the three different proportion(i.e. 0, 0.25, and 1.0 wt%)permeate through a unidirectional(UD)carbon fiber was used to prepare the GNPs/UD CFRP laminates in order to investigate whether different ratios of GNPs have the same reinforcing behavior for GNPs/UD CFRP laminates and GNPs/epoxy nanocomposites. Experimental results showed that when the GNPs added in an amount of 0.25 %, the tensile strength, flexural strength, and interlaminar shear strength of the GNPs/UD CFRP laminate compared to that of neat CFRP were increased by 6%, 4%, and 10%, respectively. However, the Young’s modulus and flexural modulus of the 0.25 wt% GNPs/CFRP laminate show negligible improvements compared to that of the neat composite laminate.
Teh, Say Lee. "The Impact of Non-Covalent Interactions on the Dispersion of Fullerenes and Graphene in Polymers." 2010. http://trace.tennessee.edu/utk_gradthes/913.
Повний текст джерелаFan, Jia-Cheng, and 范家誠. "Poly(4-hydroxystyrene)-co-Polystyrene / Graphene Oxide Nanocomposites:Study of Dispersion and Anticorrosion Through H-bonding." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/76612806692337280049.
Повний текст джерела輔仁大學
化學系
102
Three polyhydroxystyrene-co-polystyrene coploymers (PHS-co-PS) have been synthesized and blend with graphene oxide (GO) to study the anticorrosion properties through H-bond formatiom. Experimental results show that dispersion of GO in the PHS-co-PS is improved as the content of hydroxystyrene increases. The enhanced dispersion morphology leads to a better anticorrosion performance for the PHS-co-PS film. Transmission Electron Microscopy (TEM) and X-ray Diffraction spectroscopy (XRD) are used to characterize the dispersion of GO in PHS-co-PS films. Cyclic Voltammetry is used to study the anticorrosion properties of PHS-co-PS/GO composites. TEM images indicate a phase- separated polystyrene/GO composite is gradually intercalated by copolymerized hydroxystyrene into the polystyrene. H-bonding occurs between GO and PHS-co-PS forces GO to separated. XRD results indicates the separation of GO in the composites. Corrosion Protection Efficiency (P.E.%) measurement from CV experiments show the anticorrosion behavior is enhanced in the higher hydroxystyrene content PHS-co-PS/GO composites. The P.E.% increases from 85.57% for the PS/2 wt% GO film to 99.98% for the PHS-co-PS (PHS 20%)/2 wt% GO film. Evidently, the H-Bond formation between GO and PHS-co-PS dose separate the GO into the PHS-co-PS film and significantly improves the anticorrosion properties of PS/GO film.
Konkena, Bharathi. "Aqueous Dispersions of Graphene Oxide, Reduced Graphene Oxide and Functionalized Graphene Oxide." Thesis, 2014. http://hdl.handle.net/2005/3035.
Повний текст джерела"SWNT and Graphene Colloidal Dispersions: Phase behavior, Material Fabrication and Characterization." Thesis, 2011. http://hdl.handle.net/1911/64416.
Повний текст джерелаDu, Zhen-Wei, and 杜振維. "Study on Dispersion of Graphite through Ultrasonic Probe Assisted with Taguchi Method." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4st3vy.
Повний текст джерела國立中興大學
化學工程學系所
106
Graphite, one of carbon material, has a layered planar structure that are held together by van der Waals forces. When the number of layers is less than a certain number, it can be called graphene. Due to graphene possesses extraordinary electronic, thermal and optical properties, it holds great promise in a wide range of applications including cooling, composite, medical materials and energy storage, etc. However, surface of graphite has strong van der Waals forces and makes it easy to aggregate to limit its application. Therefore, how to enhance the stability of the dispersion solution and reducing the secondary particle size is a very important issue. In this study, the dispersion and exfoliation of graphite in the solution is carried out by batch or cyclic ultrasonic probe processes. In the experimental design, graphite plays role of the dispersion phase, and the mixture of acetone and deionized water are used as continue phase. Using UV-Visible Spectrometers (UV-Vis) with Taguchi method to find the optimal parameters, indicating the dispersion conditions that allows the dispersion to have the lowest light transmittance, including graphite amount, ratio of acetone to water, dispersion temperature, dispersion time, wetting time, ultrosonic frequency, ultrosonic power, and the flow rate of dispersion solution, in batch and cyclic processes. In the characterization, we used polarized optical microscope (POM) to evaluate the lateral dimensions of the dispersed graphite, atomic force microscopy (AFM) to observe the morphology and thickness of the exfoliated graphene, Raman spectroscopy (Raman) was used to identify the surface properties of graphite and exfoliated graphene. As shown in the results, we summarized the following remarks: (1) According to the results from Taguchi experiment, the optimal condition for the dispersion of graphite in the batch process was A1B4C4D4E4, meaning 1 wt% of graphite, 1/4 ratio of water to acetone, 25 ̊C of dispersion solution, 10 minutes for dispersion, and 7 days for wetting, which the most effect of parameter is graphite amount that contribution reach 73%, as well as that through the cyclic process, the optimal condition was A1B3C3D3E3F2G3H3, expressing 1 wt% of graphite, 1/4 ratio of water to acetone, 25 ̊C of dispersion solution, 25 minutes for dispersion, 5 days for wetting , 0.75: 0.25 of ultrasonic frequency, 175 W of ultrasonic power, and 300 ml/min of dispersion solution flow, which the most influential parameter is also graphite amount contributed by about 65%. (2) As analyzed by POM, smaller average particle sizes of dispersed graphite in mixture of acetone and water by means of batch and cyclic processes were 7.9 μm and 10.2 μm respectively. This discrepancy is because that the optimal conditions of dispersion time and wetting time in batch process are both longer than that in continue ones. If the dispersion time and wetting time of the cyclic process are regulated to be the same as those of the batch ones, the average particle size of dispersed graphite in solution can be reduced to 7.1 μm. This suggests that the wetting and dispersion time are significant factors for the dispersion of graphite in solution through ultrasonic probe. (3) From the Raman spectra, with the optimal conditions of batch and cyclic processes, the ratios of ID/IG and I2D/IG were 1.02 and 0.76, as well as 0.33 and 0.80 respectively. This infers that the disorder of exfoliated graphene by batch process is more than that by cyclic process, but the layer number of exfoliated graphene are almost same for the batch and cyclic process. (4) With the UV-Vis spectra and AFM image under same wetting and dispersion time, the obtained concentration and thickness of exfoliated graphene were 0.0451 mg/ml and 2.29 nm, as well as 0.0360 mg/ml and 1.74 nm, through batch and cyclic processes respectively. (5) As measured by zeta potential and natural sedimentation, with optimal conditions of batch process, the zeta potential of as-prepared dispersion solution of graphite was -31 mV, having well stability, which life time was more than three weeks at least for storage without sedimentation. (6) The yield of graphene can be known by dividing the concentration of graphene after exfoliation from the concentration of graphite before dispersion. As a result, under same wetting and dispersion time, the yield of graphene were 0.37% and 0.31%, for the batch and cyclic process, respectively, meaning that the production rate of graphene is almost same for two different processes in this study.
Vaghetto, Rodolfo. "Experimental Study of the Thermal-Hydraulic Phenomena in the Reactor Cavity Cooling System and Analysis of the Effects of Graphite Dispersion." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9225.
Повний текст джерелаLi, Shang-Shih, and 李尚實. "Dispersion of the Graphite Encapsulated Nickel Nanocrystals with Different Particle Sizes in the NP-9 Colloidal System." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/47376080066599460911.
Повний текст джерела國立臺灣大學
地質科學研究所
94
Graphite encapsulated metal (GEM) nanoparticles is a relatively new material. With an inner ferromagnetic metal core and several layers of outer graphitic shells, GEM (1-100 nm in diameter) can survive in severe environments and still preserve its nanocrystalline properties. GEM has many potential applications, and some of which require dispersive particles, e.g. as a dispersive catalyst on a substrate when making carbon nanotubes; yet before this type of applications could ever become reality one major problem must be solved. The problem is the severe agglomeration of the GEM nanoparticles, which is due to both the van der Waal’s forces among the particles and the strong magnetic forces of their ferromagnetic cores. Because the sizes of agglomerated particles are much larger than nanometer scale, the characteristic properties of nanoparticles, such as high surface to volume ratio and better absorption, will be lost. To effectively disperse the GEM nanoparticles, many organic solvents such as methanol, oleic acid and acetone had been used but with little success. The best results came when a non-ionic surfactant – nonylphenol ethoxylate (NP-9) – was used, combined with an improved synthesis technique to control the average particle sizes by adjusting total pressure, that GEM nanoparticles uniformly suspended in NP9 solution and formed a colloid. Colloids are distinguished from true solutions by the presence of particles that are too small to be observed under a microscope yet are much larger than common molecules. The viscosity of GEM colloids of various weight percentage of NP-9, with fixed temperature and pH, were analyzed by a rheometer. The viscosity apparently decreases with the particle size of GEM. In addition, the solution becomes saturated jelly-like substance as the weight percentage of NP-9 is equal to 40%-50%. Preliminary results show that the key of success is to reduce the average particle sizes of GEM, e.g. from 25 nm to 14 nm such as in this work, thus minimize the magnetic interaction between GEM and increase the effective reaction surface area with surfactant NP-9. Other factors such as temperature and pH value will be included in future experiments.
Hsu, Wen-Yin, and 許文音. "Study of Improving Dispersity of Conductive Additive VGCF and Anode Graphite in Lithium Ion Battery." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/08492171893736117134.
Повний текст джерела靜宜大學
應用化學研究所
98
Because of the worldwide concern about energy source and environment, the development of energy storage products and technologies has been paid highly attention to. Lithium ion battery is one of the most potential energy storage products now. Mesophase graphite powder(MGP) is spherical material with lamellar microstructure and with good performance as an anode material of lithium ion battery. However, the thermal expansion of the electrode will easily spoil the connection between each Mesophase graphite sphere. By adding fibrous conductive additive, Vapor Growth Carbon Fiber (VGCF), the linkage of condcutive channel of graphite spheres will be effectively improved. Nevertheless, the dispersing method of VGCF is the key process of this technology. In this research, the nonionic surfactant, Hypermer KD-1(KD-1) and Polyvinylpyrrolidone K30 (PVP K30) were chosen to improve the dispersity of Mesophase graphite powder and VGCF. The rheometer was applied to analyze rheological properties of anode slurries with different recipes. And the micro-image of electrodes by SEM and uniformity of resistance on electrodes by resistance analyzer were used to understand the relationship between concentration and types of surfactant and dispersity of VGCF. The electrode expansion ratio was tested to prove the influence of VGCF on electrode structure. Then the discharge capacity and the first cycle irreversible loss of the coin-type cells made of the electrodes respectively were tested. The discharge rate test and cycle life test of LiCoO2+ LiNi0.33Co0.33Mn0.33O2/MGP+VGCF cell were tested to check the effectiveness of surfactants and dispersity of VGCF on the performance of cell.
Lin, Yun-Hsuan, and 林昀萱. "Preparation of Graphene oxide-based magnetic molecularly imprinted polymer for dispersive solid phase microextraction of Hexestrol prior to HPLC-UV determination." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/jd67j7.
Повний текст джерела國立中興大學
化學系所
106
In this study, using magnetic particles as a substrate, modifying graphene oxide can increase the surface area of molecularly imprinted polymers, enhance adsorption capacity, also reduce the adsorbent materials used. After modification of the magnetic particles with graphene oxide, secondary modification of Tetramethylsilane (TMOS) and 3-(trimethoxysilyl) propyl mthacrylate (MPS) with this composite material (MGO) can effectively bond the MIP on the MGO surface. In addition, a certain thickness of cross-linking agent can be used between MIP and MGO to reduce the adsorption capacity of graphene and improve the selectivity to analytes. Hexestrol is used as a template molecule, methacrylic acid (MAA) as functional monomer, Ethylene glycol dimethacrylate (EDGMA) as cross linker, and Azobisisobutyronitrile (AIBN) as initiator in the preparation of MIP. In order to achieve the best extraction efficiency, graphene oxide addition amount, extraction time, desorption time, desorption solvent, pH value, and salting-out effect. The experimental results show that under the condition of pH = 7 only for 5 minutes, the MGO-MIP particles were adsorbed by strong magnets and the matrix solution was removed. After washing with ultrapure water, desorption was performed with 1 ml of acetone. After the extraction solution was dried with nitrogen, it was re-dissolved with 100 μL of acetonitrile and injected into the HPLC-UV analysis. Adsorption of different concentrations of sample under optimized conditions, the linear range of the concentration is 1.5-150 ng∙mL^(-1) with the correlation coefficient of 0.9994. Limit of detection was 0.1 ng∙mL^(-1), limits of quantitative 0.5 ng∙mL^(-1), precision RSD was 1.1 %. The MGO-MIP/SPE was applied in real sample analysis such as river and lake. The relative recoveries were ranged between 93.5 %-101.8 % hexestrol in real samples. Result showed that the MGO-MIP/SPE sorbent for the determination of hexestrol in aqueous samples with HPLC-UV method demonstrated the advantages of simple, rapid, and good recovery sampling pretreatment methods.
Alves, Ana Catarina Gomes Moreira. "Synthesis and characterization of abiotic electrocatalysts based on reduced graphene oxide for oxygen reduction reaction." Master's thesis, 2019. http://hdl.handle.net/10451/40629.
Повний текст джерелаThe use of low-temperature fuel cells as power supplies of energy conversion devices is attracting considerable interest because of the direct electrochemical conversion of a fuel, e.g. hydrogen and glucose, and an oxidant, such as oxygen, producing electrical current. The sluggish kinetic of the oxygen reduction reaction (ORR) on the cathode half-reaction is particularly investigated since its acceleration relies on the development of efficient electrocatalysts. Unfortunately, the most promising catalysts for ORR are platinum-based materials that exhibit poor durability, limited resource and high cost. Under such circumstances, the development of non-noble, efficient and low-cost electrocatalysts has attracted a great deal of attention. The present dissertation focuses on the synthesis and physicochemical characterization of graphene-based materials doped with nitrogen and 2 and 10 wt % transition metals (Fe, Co, Mn, Cu, Ni and Rh), denoted as rGO/M 2 and 10 %, capable of reducing molecular oxygen. Firstly, nitrogen-doped reduced graphene oxide with atomically dispersed transition metal materials were synthesized using commercial graphene as precursor. A sequential extra-exfoliation and oxidation of the graphene increased the d-spacing between carbon layers and created porosity on the structure, which is essential for the diffusion of reactants on the material. Further simultaneous N doping and reduction of graphene oxide using thermal and low-temperature plasma treatment allowed the formation of M-Nx active sites that contribute greatly on the ORR activity. The obtained carbon structure exhibited a large specific surface area (c.a. 800 m2 g-1) doped with c.a. 1.98 wt % of nitrogen. The incorporation of atomically dispersed metal reached 21 % of 2 wt %, 3 % and 0.46 % of 10 wt % using different reduction methods. The engagement of aromatic macrocycle molecules, particularly iron and cobalt metalloporphyrins, in the graphene oxide structure was also studied. The synthesis of these hybrid materials was based on a procedure described previously, relying on the addition of the metalloporphyrin to the graphene structure, followed by its pyrolysis under N2 atmosphere. The ORR electrochemical characterization of the materials was performed using hydrodynamic convective systems: the rotating disk electrode (RDE) and the rotating ring-disk electrode (RRDE), in acidic, alkaline and neutral media. Among all the synthesized materials, iron- and cobalt-based materials showed the highest performance towards ORR. In particular rGO/Fe 2 % exhibited a remarkable activity in acidic (Eonset 0.76 V vs. RHE), alkaline (Eonset 0.91 V vs. RHE) and neutral (Eonset 0.78 V vs. RHE) media, comparable to Pt/C catalysts. A mixed 2- and 4-electron pathway was observed for rGO/Fe 2 % in acidic and alkaline media due to the contributions of several functional groups in the structure. The remaining materials displayed lower onset potential in acidic (0.44 to 0.71 V vs. RHE), alkaline (0.80 to 0.87 V vs. RHE) and neutral (0.64 to 0.74 V vs. RHE) media. The outstanding ORR performance of these materials is attributed to the presence of M-Nx actives sites dispersed in the carbon structure and intrinsic ORR activity of metalloporphyrins.
Rodrigues, Pedro António Veiga. "Estudos de dispersão de nanografite em polipropileno." Master's thesis, 2015. http://hdl.handle.net/1822/39537.
Повний текст джерелаNo presente trabalho foram estudados os mecanismos de dispersão e reaglomeração de nanocompósitos de polipropileno (PP) /grafite exfoliada na composição e no processamento por extrusão. A composição foi realizada numa mini-extrusora de duplo-fuso com três zonas de mistura intensiva constituídas por elementos de mistura (kneading blocks) separadas por zonas de transporte. Procedeu-se à composição de nanocompósitos de PP com 2% ou 10% (p/p) de grafite GnP C ou grafite GnP H, e o seu posterior processamento numa mini-extrusora de mono-fuso, utilizando duas velocidades de rotação do parafuso. A evolução da dispersão ao longo das duas extrusoras foi analisada por microscopia ótica de campo claro. Também foram estudados o efeito da funcionalização via cicloadição dipolar 1,3 das grafites ligadas covalentemente ao PP enxertado com anidrido maleico (PP-g-AM), bem como as propriedades elétricas dos nanocompósitos. Na etapa de composição, observou-se o decréscimo significativo no tamanho e na quantidade dos aglomerados de grafite na passagem pela primeira zona de mistura intensiva, demonstrando a sua ação eficaz. A dispersão ao longo da mini-extrusora revelou-se constante após a primeira zona. No entanto, a funcionalização da grafite GnP C revelou um aumento da dispersão contínuo até à cabeça de extrusão. Os níveis de dispersão da grafite GnP H funcionalizada foram muito similares às da não-funcionalizada. No processamento, observou-se uma tendência geral de aumento da quantidade de aglomerados visíveis, indicando reaglomeração, independentemente da velocidade de processamento. Esta reaglomeração foi menos expressiva para os nanocompósitos com grafite funcionalizada. A dispersão foi aumentando ao longo da mini-extrusora, sendo o aumento maior para a velocidade mais elevada. A morfologia final dos nanocompósitos processados apresenta um nível de dispersão menor do que a resultante da composição. Simultaneamente, verificou-se um aumento da condutividade elétrica após o processamento. Nos nanocompósitos de PP com grafite GnP C, a funcionalização resultou numa menor condutividade, uma vez que induziu níveis de dispersão maiores.
The present work reports the study on the mechanisms of dispersion of exfoliated graphite/ polypropylene nanocomposites upon melt compounding and extrusion. Compounding was performed in a mini twinscrew extruder containing three intensive mixing zones consisting of kneading blocks. PP with 2wt. % or 10wt. % of GnP C or GnP H were compounded and subsequently processed by a mini single-screw extruder using two different screw speeds. The evolution of dispersion throughout compounding and processing was analysed by optical microscopy. The effect of graphite functionalization via 1,3 dipolar cycloaddition grafted with PP-g-MA (PP grafted with maleic anhydride) was also studied, as well as the electrical properties of the nanocomposites. The first set of kneading blocks were effective in decreasing the number and size of the graphite agglomerates. The dispersion along the mini-extruder proved to be constant after the first zone. However, functionalization of graphite GnP C revealed an increase in dispersion. The dispersing levels of as received and functionalized graphite GnP H were very similar, indicating that this kind of functionalization had no significant impact on dispersion. Along extrusion, the amount of agglomerates increased, indicating re-agglomeration of graphite agglomerates, regardless of processing speed. This re-agglomeration was less pronounced for nanocomposites with functionalized graphite. The final morphology of processed nanocomposites is coarser in comparison with composition. Concerning the electrical properties, there was an increase in conductivity of several orders of magnitude after processing. In the case of nanocomposites with GnP C graphite, functionalization induced lower conductivity, since it resulted in higher levels of dispersion.
Su, Huang-kai, and 蘇煌凱. "Dispersing conductive carbon to LiFePO4 electrode and Tin oxides and sulfides modified graphite for negative electrode in lithium ion battery." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/34849523748754602409.
Повний текст джерела國立臺南大學
綠色能源科技研究所碩士班
99
Lithium ion battery has been requested for further property improvement to meet the need of 3C products, portable equipments and electric vehicles (EVs). Recently, the concept of green-tech has been an important topic for many scientists in all different kinds of fields. In this study, we choose LiFePO4 and natural graphite as the electrode materials, which are cost efficient and environmental friendly. We add conductive addictive into LiFePO4 under different conditions and modified natural graphite with different Tin compounds. By combining two modified methods, we expect to obtain a better electrochemical property. In addition, the improved positive electrode and the modified negative electrode were investigated by half-cell tests to obtain the efficiency of electronic capacity and some electrochemical properties. The results suggest that when using HSC-03 dispersion to LiFePO4 as a conductive additive in positive electrode, the high-rate test and the performance of cycle life are greatly improved (capacity is raised by 40% after 100 cycles at rate of 1C). On the other hand, we modified Tin sulfide or Tin oxide compounds on the surface of natural graphite and surveyed the structural changes of SEI film by CV and ESCA analysis. The Tin compounds are likely to reduce the thermal stability but enhance the capacity and the stability of cycle life. In conclusion, we have proved that the combination of the improved electrodes in this study for full cell test can enhance the capacity and cycling performance for lithium ion battery.
Chen, Yu-Shin, and 陳淯信. "New In-tube Dispersive Micro-solid-phase Extraction Coupled Electrostatic-Assisted Collection of Sulfonated Graphene for the Determination of Polycyclic Aromatic Hydrocarbons in Aqueous Samples by GC-MS." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/60122255363170424727.
Повний текст джерела國立中興大學
化學系所
101
In this work, a new rapid dispersive micro-solid phase extraction (DMSPE) technique coupled electrostatic-assisted collection of sulfonated graphene nanosheets (sGNS) followed by gas chromatography-mass spectrometry (GC-MS) for the determination of polycyclic aromatic hydrocarbons (PAH) in aqueous samples was developed. In this method, water soluble sulfonated graphene nanosheets was synthesized and utilized as nano-sorbent for the extraction of PAH and a newly designed home-made glass extraction device was adopted to collect the negatively charged sGNS based on the electrostatic migration by applying positive high voltage. Parameters affecting the proposed extraction method was thoroughly examined and optimized. The maximum extraction efficiency was obtained under the selected condition as follows; 8 mL of aqueous sample (pH 6) with 1 mg of sGNS were taken in the extraction device and 30 kV was applied to collect sGNS and followed by desorption using 10μL of toluene under ultrasonication for 15 min. Under the optimal conditions, the liner ranges were 1-1000 μg/L for naphthalene, acenaphthylene and acenaphthene, 2-2000 μg/L for fluorine, phenanthrene, anthracene, fluoranthene, pyrene and 3-3000 μg/L for benzo(a)anthracene and chrysene. Detection limits were achieved at level of 0.3-0.9 μg/L and the limit of quantitation were 1.0-3.2 μg/L. The relative recoveries of river samples were between 82.3-117.7 % and RSD were below 8.1%. The results demonstrated that the proposed method was a simple, rapid, sensitive, low cost and eco-friendly approach for the determination of PAH in aqueous samples.