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Saha, Aniruddha. "Studies on the resistance of tea Camellia Sinensis (L). O.KTZE to Bipolaris carbonum Nelson." Thesis, University of North Bengal, 1992. http://hdl.handle.net/123456789/900.
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Jouan, Sébastien. "Développement et caractérisation de transistors bipolaires à hétérojonctions Si/SiGe pour les circuits radiofréquences." Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10011.
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Kumsapaya, Chawanwit. "Greffage de couches organiques par électrochimie bipolaire." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0269/document.
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Dans cette thèse, le concept d’électrochimie bipolaire qui permet de réaliser des réactions électrochimiques par l’application d’un champ électrique, sur un objet conducteur placé dans une solution électrolytique sans aucun contact avec les électrodes, a été utilisé pour générer des objets Janus possédant une partie organique et une partie inorganique. Comme preuve de principe, des billes de carbone vitreux de taille micrométrique ont été modifiées de manière asymétrique par électrochimie bipolaire en réduisant un sel d’aryl diazonium. La couche organique ainsi greffée a pu être observée après interaction avec des nanoparticules d’or, ou des molécules fluorescentes. Les résultats ont montré que la moitié de la surface des billes a pu être modifiée de manière sélective et avec une grande précision. En ajustant le temps et/ou le champ électrique utilisé pour la réduction du sel de diazonium, la surface greffée peut être modulée. Ce concept a été généralisé à l’échelle nanométrique sur des nanotubes de carbone alignés verticalement. Ces nanotubes de carbone ont été préparés par un dépôt chimique en phase gazeuse en utilisant un template d’oxyde d’aluminium poreux. L’électrogreffage bipolaire d’une couche organique uniquement sur une extrémité des nanotubes et uniquement sur la face interne de ces tubes, a été possible en conservant les nanotubes piégés dans le template d’oxyde d’aluminium. Cette technique ouvre donc la voie d’applications dans le domaine des piles à combustible, des bio-capteurs, et également pour la délivrance contrôlée de médicamentsIn this thesis, the concept of bipolar electrochemistry, which allows carrying out electrochemical reactions on a free-standing conductive object in an electric field, was employed to generate Janus-type objects with a hybrid organic-inorganic composition. As a proof-of-concept micrometer-sized glassy carbon beads were modified asymmetrically via the bipolar electrochemical reduction of aryl diazonium salts. The grafted organic layers can be probed either with gold nanoparticles (AuNPs) or with fluorescent molecules. The results show that one-half sphere of the beads was modified selectively and with high precision. This concept was then generalized to vertically aligned carbon nonotubes (VACNTs). They were prepared via chemical vapor deposition using porous anodic aluminum oxide (AAO) as template. The bipolar electrografting of an organic layer onto the inner surface of the VACNTs was performed by using the tubes that were still embedded in the pores of the AAO membrane as the starting material. The grafted results can be visualized by coupling them with AuNPs. After the AAO removal, the results reveal a grafting of organic layers only at one end of the tubes along the inner wall. For both cases, fine tuning of the deposition time and/or the electric field used for the reduction of diazonium salts can control the geometric area of the grafting. This technique opens up applications of these objects in the fields of controlled drug delivery and storage
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Phuakkong, Oranit. "Design of carbon based structures for electrochemical applications." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0305/document.
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Dans cette thèse nous avons étudié la mise en forme de matériaux carbonés par des méthodes électrochimiques pour des applications dans les domaines des capteurs et de l’énergie. Dans la première partie, l’électrochimie bipolaire, qui permet de réaliser des réactions électrochimiques sur un objet conducteur présent dans une solution et soumise à un champ électrique, a été utilisée pour générer des objets de type Janus. Ces objets asymétriques ont été modifiés à une extrémité par du poly(N-isopropylacrylamide (pNIPAM), un hydrogel sensible à la température, et par une peinture électrophorétique à l’autre extrémité. En contrôlant l’intensité du champ électrique ainsi que son temps d’application il a été possible de varier la longueur ainsi que l’épaisseur de l’hydrogel. Ces objets sensibles à la température, émettant de la lumière, ont des applications potentielles dans le domaine des capteurs ou dans le milieu médical.Dans la seconde partie, la mise en forme de carbone poreux pour des applications électrochimiques a été étudiée. La carbonisation de polymères contenant du zinc a été utilisé pour synthétiser du carbone micro/mésoporeux possédant ainsi une grande surface spécifique. Les polymères contenant du zinc ont été préparés à partir de différents types de ligands d’acide dicarboxylique par une méthode solvothermique. Ils ont ensuite été carbonisés pour obtenir des matériaux poreux avec des caractéristiques et des propriétés particulières. Ils ont été utilisés comme matériaux d’électrode pour des supercondensateurs, montrant des capacités élevées. De plus ils possèdent également une activité électrocatalytique à la réaction de réduction de l’oxygèneIn this thesis, the design of advanced carbon materials via electrochemical techniques and for electrochemical applications have been studied. In the first part, the concept of bipolar electrochemistry, which allows carrying out electrochemical reactions on a free-standing conductive object in an electric field, was employed to generate Janus-type objects. These objects are modified with a thermoresponsive hydrogel of poly(N-isopropylacrylamide) (pNIPAM) on one side and an electrophoretic deposition paint (EDP) on the other side. The results show that the length and the thickness of the hydrogel can be controlled by varying the electric field and the time of the experiment. The concept can be further generalized to other micro- and nanometer-sized objects, thus opening up perspectives for various applications.In the second part, the design of porous carbon structures for electrochemical applications was studied. The direct carbonization of non-porous zinc containing polymers was used to synthesize micro/mesoporous carbons with high surface area, pore volume. Non-porous zinc containing polymers with various types of dicarboxylic acid ligands prepared by solvothermal method were used as templates and starting materials. After carbonization porous carbons with various characteristics and properties were obtained. The synthesized porous carbon samples showed good electrochemical performance with high capacitance values. In addition, the derived materials exhibit excellent electrocatalytic activity with respect to the oxygen reduction reaction (ORR)
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Dahlström, Mattias. "Ultra High Speed InP Heterojunction Bipolar Transistors." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3527.
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This thesis deals with the development of high speed InPmesa HBTs with power gain cutoff frequencies up toand above 300 GHz, with high current density and low collectordischarging times.
Key developments are Pdbased base ohmics yielding basecontact resistances as low as 10 Ωµm2, basecollector grades to enable to use ofInP in the collector, and an increase in the maximum currentdensity through collector design and thermal optimization.HBTs with a linear doping gradient in the base are forthe first time reported and compared to HBTs with abandgap graded base. The effect of degenerate base doping issimulated, as well as the base transit time.
Key results include a DHBT with a 215 nm thick collector andan fτ= 280GHz, and fmax=400 GHz. This represents the highest fmaxreported for a mesa HBT. Results also include aDHBT with a 150 nm thick collector and an fτ= 300 GHz, and fmax=280 GHz. The maximum operating current densityhas been increased to above 10 mAµm while maintaining fτand fmax≥ 200 GHz.
A mesa DHBT process with and as much yield and simplicity aspossible has been developed, while maintaining or pushingworldclass performance.
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Brossard, Florence. "Epitaxies Si/SiGe(C) pour transistors bipolaires avancés." Phd thesis, Université Joseph Fourier (Grenoble), 2007. http://tel.archives-ouvertes.fr/tel-00200095.
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L'objectif de cette thèse est d'étudier les épitaxies SiGeC sélectives par rapport au nitrure de silicium afin d'améliorer les performances en fréquence des transistors bipolaires à hétérojonction à structure complètement auto alignée. Pour répondre à cette attente, le système SiH4/GeH4/SiH3CH3/HCl/B2H6/H2 est utilisé pour élaborer nos épitaxies sélectives.Cette chimie à base de silane permet d'augmenter significativement la vitesse de croissance par rapport au système SiCl2H2/GeH4/HCl/H2 utilisé classiquement, aussi bien pour un dépôt silicium sélectif que pour un film SiGe sélectif. Par exemple, pour un film Si0,75Ge0,25 la vitesse de croissance est multipliée par un facteur 8.
L'incorporation des atomes de carbone dans les sites substitutionnels est facilitée par cette hausse du taux de croissance. En effet, la teneur en carbone substitutionnel est plus élevée en utilisant le silane comme précurseur de silicium (jusqu'à un facteur 4). L'effet bloquant du carbone sur la diffusion du bore est alors meilleur et le dopant est mieux contenu dans la base Si/SiGeC:B. Cette meilleure incorporation du carbone se reflète dans les résultats électriques. Le courant IB n'augmente pas aux fortes concentrations de carbone, ce qui signifie qu'il n'y a pas de centres recombinants dans la base. Le courant IC et la fréquence fT augmentent aussi, ce qui suggère que la largeur de la base neutre est plus fine et donc que la diffusion du bore est ralentie.
Nous avons également mis en évidence l'existence d'une corrélation entre le courant IB et l'intensité du signal de photoluminescence à température ambiante. En effet, considérant que leurs mécanismes de recombinaison sont similaires, nous avons noté que la hausse de IB correspond à la chute de la photoluminescence.
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Yoshioka, Ricardo Toshinori. "Processo de fabricação de HBT em camadas de InGaP/GaAs." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261260.
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Orientador : Jacobus Willibrordus SwartTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-01T03:19:05Z (GMT). No. of bitstreams: 1 Yoshioka_RicardoToshinori_D.pdf: 5664583 bytes, checksum: 23bca28e4856ca609fc3f0c59981bf76 (MD5) Previous issue date: 2001
Doutorado
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Suvar, Erdal. "SiGeC Heterojunction Bipolar Transistors." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3674.
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Heterojunction bipolar transistors (HBT) based on SiGeC havebeen investigated. Two high-frequency architectures have beendesigned, fabricated and characterized. Different collectordesigns were applied either by using selective epitaxial growthdoped with phosphorous or by non-selective epitaxial growthdoped with arsenic. Both designs have a non-selectivelydeposited SiGeC base doped with boron and a poly-crystallineemitter doped with phosphorous.
Selective epitaxial growth of the collector layer has beendeveloped by using a reduced pressure chemical vapor deposition(RPCVD) technique. The incorporation of phosphorous and defectformation during selective deposition of these layers has beenstudied. A major problem of phosphorous-doping during selectiveepitaxy is segregation. Different methods, e.g. chemical orthermal oxidation, are shown to efficiently remove thesegregated dopants. Chemical-mechanical polishing (CMP) hasalso been used as an alternative to solve this problem. The CMPstep was successfully integrated in the HBT process flow.
Epitaxial growth of Si1-x-yGexCy layers for base layerapplications in bipolar transistors has been investigated indetail. The optimization of the growth parameters has beenperformed in order to incorporate carbon substitutionally inthe SiGe matrix without increasing the defect density in theepitaxial layers.
The thermal stability of npn SiGe-based heterojunctionstructures has been investigated. The influence of thediffusion of dopants in SiGe or in adjacent layers on thethermal stability of the structure has also been discussed.
SiGeC-based transistors with both non-selectively depositedcollector and selectively grown collector have been fabricatedand electrically characterized. The fabricated transistorsexhibit electrostatic current gain values in the range of 1000-2000. The cut-off frequency and maximum oscillation frequencyvary from 40-80 GHz and 15-30 GHz, respectively, depending onthe lateral design. The leakage current was investigated usinga selectively deposited collector design and possible causesfor leakage has been discussed. Solutions for decreasing thejunction leakage are proposed.
Key words:Silicon-Germanium-Carbon (SiGeC),Heterojunction bipolar transistor (HBT), chemical vapordeposition (CVD), selective epitaxy, non-selective epitaxy,collector design, high-frequency measurement, dopantsegregation, thermal stability.
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Husby, Håvard. "Carbon Based Coatings for Metallic Bipolar Plates in PEM Fuel Cells." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemisk prosessteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22407.
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Global warming and the climate changes are issues that concern everyone. The transition to other energy carriers than fossil fuels is a key barrier if we are to reduce our dependence on oil. Hydrogen is forecasted as the energy carrier of the future, and one of the most efficient ways to convert hydrogen to electrical, useful energy is to feed it to the anode side of a polymer electrolyte (PEM) fuel cell. Oxygen (usually in the form of air) is supplied to the cathode side and the only products are water, electricity and some heat.A key component in PEM fuel cells are the bipolar plates that facilitate gas flow, electron transfer, heat and water removal. The bipolar plates contribute greatly to both weight and cost of PEM fuel cells, and there is continuous development in making cheap, durable, light and efficient bipolar plates.In this work we attempted to coat stainless steel (316L) plates with a coating consisting of graphite and carbon black mixed with epoxy. The goal was to get a coating that conducts electrons while still protecting against corrosion. The coatings were sought further improved by adding Teflon particles. This was done to get the coating more hydrophobic, and thus a better corrosion protection of the underlying stainless steel substrate. Plates were glass blasted prior to coating to improve adhesion.Coatings were thinned with xylene and sprayed onto the plates with an air brush. The plates were then pressed in a ?Carver? hot-press to achieve minimum porosity. The coated plates were examined in a contact resistance apparatus, subjected to linear sweep voltammetry and chronoampereometry, the contact angles were measured, the surface roughness measured and SEM images are taken.Plates pressed at 2670 N cm-2 for 30 minutes with 4.8 vol% Zonyl in the coating performed best prior to electrochemical measurements both for the glass blasted plates and for the as-delivered plates. The contact resistances measured at 147 N cm-2 compaction pressure was 11.3 and 10.6 mOmega cm2 respectively. This is close to the goals set by DOE to reached by 2020 (10 mOmega cm2 at 138 N cm-2). The contact resistances for all coatings tested increased very much after the electrochemical testing, and all were far above the goals set by DOE.A correlation was found between the coating thickness and the current densities measured during the potentiostatic measurements. The current densities increased with increasing coating thickness. Possible mechanisms and reasons for this are discussed, and a combination of carbon corrosion and crevice corrosion is suggested as explanation.A possible method for anchoring the coating to the substrate while protecting the contact points from degradation during electrochemical measurements was suggested. By pressing the coating into carefully controlled voids, connections between the graphite in the coating and the metal substrate might be retained, even if the connection between main substrate surface and the coating is broken. This effect can explain the differences seen between the plates coated in the project work, and the metal sheets coated in this work.
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Duddukuri, Ramesh. "SYNTHESIZING AND CHARACTERIZATION OF TITANIUM DIBORIDE FOR COMPOSITE BIPOLAR PLATES IN PEM FUEL CELL." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/862.
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This research deals with the synthesis and characterization of titanium diboride (TiB2) from novel carbon coated precursors. This work provides information on using different boron sources and their effect on the resulting powders of TiB2.The process has two steps in which the oxide powders were first coated with carbon by cracking of a hydrocarbon gas, propylene (C3H6) and then, mixed with boron carbide and boric acid powders in a stoichiometric ratio. These precursors were treated at temperatures in the range of 1200-1400° C for 2 h in flowing Argon atmosphere to synthesize TiB2.The process utilizes a carbothermic reduction reaction of novel carbon coated precursor that has potential of producing high-quality powders (sub-micrometer and high purity). Single phase TiB2 powders produced, were compared with commercially available titanium diboride using X-ray diffraction and Transmission electron microscopy obtained from boron carbide and boric acid containing carbon coated precursor.
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Braun, Artur [Verfasser]. "Development and Characterization of Glassy Carbon Electrodes for a Bipolar Electrochemical Double Layer Capacitor / Artur Braun." Hamburg : Diplom.de, 2002. http://d-nb.info/1117595579/34.
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Anteney, Iain M. "An investigation of group IV alloys and their applications in bipolar transistors." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326641.
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Gueth, Frederic. "Observations interférométriques des flots moléculaires L1157 et HH211." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10202.
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La formation des etoiles s'accompagne de puissants phenomenes d'ejection de matiere, qui se traduisent par la presence de flots moleculaires bipolaires autour de la plupart des protoetoiles. Cette these etudie la structure interne des flots moleculaires, a l'aide d'observations interferometriques millimetriques realisees a l'interferometre du plateau de bure de l'iram. Les cartes presentees figurent parmi les toutes premieres images de flots moleculaires realisees avec une resolution angulaire aussi elevee (de l'ordre de la seconde d'arc). Deux flots extremement jeunes (environ 10000 ans) et leurs protoetoiles excitatrices sont etudies, a travers l'emission de co et sio. Le flot moleculaire de l 1157 revele deux cavites distinctes, dont les distributions de brillance et les proprietes cinematiques peuvent etre reproduite par un modele de precession. Une forte interaction prend place entre le flot et l'enveloppe entourant la protoetoile. Cette derniere montre de plus une signature d'effondrement gravitationnel. Le flot de hh 211 presente quant a lui une structure remarquable dans laquelle un jet moleculaire rapide emerge de la source centrale et est entoure d'une cavite detectee a plus faible vitesse. La forme de cette derniere correspond parfaitement aux predictions de modeles simples de propagation d'un choc en arc. Plusieurs aspects des observations de l 1157 et hh 211 sont egalement discutes, parmis lesquels les mecanismes de formation des flots moleculaires (la propagation de larges chocs en arc semble etre l'hypothese la plus pertinente) et les processus de formation de la molecule sio dans les flots. Finalement, la deuxieme partie de cette these presente les algorithmes de reconstruction et de deconvolution, adaptes au cas des observations interferometriques de mosaiques, qui ont ete developpes pour permettre les observations decrites precedemment.
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DRIAD, RACHID. "Etude du gaas dope carbone et realisation de transistors bipolaires a heterojonction gainp/gaas planars par reprise selective d'epitaxie par jets chimiques." Evry-Val d'Essonne, 1996. http://www.theses.fr/1996EVRY0021.
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Cette etude est une contribution au developpement des techniques de fabrication de circuits integres sur arseniure de gallium. Une nouvelle technologie pour transistors bipolaires a heterojonction autoalignes planar a ete mise au point. Ce procede utilise la croissance selective par jets chimiques pour ramener en surface les couches enterrees de contacts de base et de collecteur. L'interet de la planarisation est d'accroitre la densite d'integration et la fiabilite des interconnexions metalliques pour la realisation de circuits complexes, notamment pour les telecommunications haut debit. Par ailleurs, la reprise de croissance de la zone extrinseque de base avec du gaas fortement dope carbone, permet de diminuer la resistance de base et par consequent d'augmenter la frequence maximale d'oscillation des tbh. En raison de l'utilisation de precurseurs organometalliques et de traitements thermiques intrinseques aux procedes de reprise de croissance, les composants planarises presentent systematiquement une degradation du gain en courant apres reprise d'epitaxie. Afin de determiner les mecanismes a l'origine de cette degradation, nous avons effectue une etude systematique de la stabilite thermique du gaas:c constituant la couche de base du tbh. Des tbh planars de 44 microns de jonction emeteur-base, avec des gains en courant de 47 et des frequences de coupures superieures a 50 ghz, ont ete obtenus a l'aide de cette nouvelle technologie planar
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Ndungu, Patrick Gathura Bradley Jean-Claude. "The use of bipolar electrochemistry in nanoscience : contact free methods for the site selective modification of nanostructured carbon materials /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/275.
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Lin, Kaijie. "Development of advanced plasma surface technologies for high performance carbon paper gas diffusion layer and 316 stainless steel bipolar plates." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6351/.
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In this work, a portfolio of novel active screen plasma surface engineering technologies have been developed including active screen plasma surface modification of carbon paper for gas diffusion layer (GDL) and active screen plasma surface co-alloying of 316 austenitic stainless steel with both interstitial alloying element of nitrogen and such substitutional alloying elements as silver (Ag), niobium (Nb) and platinum (Pt). The active screen plasma surface modification of GDL carbon paper at a low temperature for a short period of time can effective activate the carbon paper surface mainly due to the removal of the hydrophobic PTFE coating and introduction of many functional groups, thus contributing to the improved growth of Pt nano-wires. Accordingly, the electrochemical and catalysis performance can be effective improved. The novel ASP surface alloying technique developed from this research has been applied to modify the 316 stainless steel surface using nitrogen for active screen plasma nitriding (ASPN); nitrogen and silver (N&Ag); nitrogen and niobium (N&Nb); and nitrogen and platinum (N&Pt). The experimental results have demonstrated that the layer structure of the ASP treated 316 SS surfaces can be tailored by using different alloying elements and/or adjusting treatment parameters. The surface electrical conductivity of 316 can be reduced significantly. The ASPN, ASPA(N&Ag) and ASPA(N&Nb) increase the corrosion potential, lower the corrosion current density, but raise the passive current density of 316 SS. Among all the surface alloying treatments, the ASPA(N&Pt) treatment has delivered the best performance and fulfilled the technique target set by the Department of Energy (DoE), USA.
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Souissi, Mohamed Ali. "Développement et caractérisation de matériaux électriquement conducteurs à base de mélanges polymères pour plaques bipolaires de piles à combustible de type PEMFC." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28082/28082.pdf.
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Günther, Marcus. "Harte amorphe wasserstoffhaltige Kohlenstoffschichten mittels mittelfrequenzgepulster Plasmaentladungen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-95197.
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Harte amorphe wasserstoffhaltige Kohlenstoffschichten (a-C:H) haben in den letzten Jahrzehnten stark an Bedeutung gewonnen. Diese Art von Hartstoffschichten wird zunehmend für die Reduzierung von Reibung und Verschleiß in unterschiedlichen Bereichen eingesetzt. In der Forschung, aber auch für Kleinserien, werden a-C:H-Schichten üblicherweise mit Hochfrequenzplasmaentladungen abgeschieden. Eine Alternative ist die Plasmaaktivierung mit einer asymmetrisch bipolar gepulsten Spannung im Mittelfrequenzbereich. Auf diese Weise wird eine homogene Beschichtung großer Substratflächen mit qualitativ hochwertigen Schichten ermöglicht.
Die vorliegende Arbeit beschäftigt sich mit der plasmagestützten Abscheidung von harten a-C:H-Schichten mit mittelfrequenzgepulsten Entladungen. Zur Schichtabscheidung werden Ethin-Argon- und Isobuten-Argon-Gasgemische verwendet. Der Einfluss des Prozessdrucks auf den Abscheideprozess und die Schichteigenschaften wird untersucht. Dazu wurden Argonentladungen und Beschichtungsplasmen mittels optischer Emissionsspektroskopie charakterisiert. Zur Charakterisierung der Schichteigenschaften wurden unter anderem Nanoindentation-Messungen, elastische Rückstreudetektionsanalysen und thermische Desorptionsspektroskopie verwendet. Zur Untersuchung des Einflusses der Ionen auf das Schichtwachstum wird ein Modell zur Identifizierung von Ionenspezies in Beschichtungsplasmen vorgestellt. In Verbindung mit der Messung der Substratströme konnte der Ionenanteil am Schichtwachstum bestimmt werden.
Ein weiterer Teil der vorliegenden Arbeit untersucht ein Hybridverfahren, in dem die mittelfrequenzgepulste Entladung mit einer zusätzlichen ECR-Entladung kombiniert wird. Es wird gezeigt, dass durch dieses Hybridverfahren eine deutliche Steigerung der Abscheiderate harter a-C:H-Schichten erreicht werden kann. Die abgeschiedenen Schichten wurden zusätzlich bezüglich ihrer Oberflächenstruktur und ihrer Verschleißfestigkeit untersucht.
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Chu, Po-Jen, and 朱柏任. "Carbon-film modified stainless steels as PEMFC bipolar plate." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/72732126715915340567.
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碩士逢甲大學
材料科學所
94
Main functions of polymer electrolyte membrane fuel cell (PEMFC) include electrical conductivity, corrosion resistance, mechanical strength, chemical stability, and density. As a substitute for costly graphite bipolar plates, our studies focus on stainless-steel bipolar plates. Carbon-film stainless steel has obvious advantages like excellent corrosion resistance (comparable to that of graphite), high electric/thermal conductivity, low cost, smaller volume, and great strength. Nickel is known as an effective catalyst for the graphitization of amorphous carbon. Nickel layer was applied to AISI 304 stainless steel by magnetron sputtering, then carbon film deposited on this nickel layer by chemical vapor deposition (CVD). Acetylene served as carbon source, argon and hydrogen as carrier gases in the CVD process. Properties of the film were evaluated with grazing incident energy dispersive spectrometer (EDS), scanning electron microscope (SEM), electrochemical analyzer, and Raman spectroscope. Test results proved that higher carrier gas flow rate promoted density of thin carbon film. Using C2H2/H2 mixture gases with flow-rate ratio of 9/20, the carbon film demonstrated continuous morphology and provided better resistances to corrosion.
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Raunija, Thakur Sudesh Kumar. "Studies on carbon/carbon composite bipolar plate for pem fuel cell in aerospace application." Thesis, 2017. http://localhost:8080/xmlui/handle/12345678/7286.
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Chih-Hung, Hung, and 洪誌鴻. "Preparation and Characterization of Carbon Nanotube/Composite Bipolar Plate for Fuel Cell." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/57459314341640147161.
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碩士國立清華大學
化學工程學系
95
This study investigates the preparation and properties of polymer composite bipolar plates (the thickness < 1.2 mm) for use in polymer electrolyte membrane fuel cells (PEMFCs). The composites contain vinyl ester resin, graphite powder, and multiwalled carbon nanotube (MWCNT). The polymer composite bipolar plates were fabricated by bulk molding compound (BMC) process. The MWCNTs studied include prinstine CNT, acid modified CNT, surfactant-modified MWCNT (CNT/POP400 and CNT/POP2000), and the functionalized MWCNT (CNT-mPOP400 and CNT-mPOP2000) prepared by free radical reaction with Poly(oxypropylene)-backboned diamine. The effect of the carbon nanotube content on the electrical, physical, mechanical, thermal properties and sigle cell test of the polymer composite bipolar plate were investigated. Both the flow field path and depth in composite bipolar plate were 0.8 mm and the flow field land was 0.8 mm. The thickness of the composite bipolar plate was 1.2 mm. The optimum composites bipolar plate was prepared with 2 phr CNT-mPOP2000. The porosity and the coefficient of thermal expansion (CTE) of the composite bipolar plate with 2 phr CNT-mPOP2000 was decreased from 0.270 % to 0.118 % and from 37.00 μm/moC to 16.62 μm/moC. The flexural strength, the electrical conductivity, and the corrosion current of the composite bipolar plate with 2 phr CNT-mPOP2000 were increased from 28.00 MPa to 48.33 MPa, and from 2.5×10-7 Acm-2 to 2.4×10-6 Acm-2 and from 155 S/cm to 1370 S/cm, respectively. The unnotched Izod impact strength of the composite bipolar plate with 1 phr CNT-mPOP2000 was increased from 53.56 J/m to 108.51 J/m. The gas permeability of composite bipolar plates in this study were no leak. All of the composite bipolar plates in this study met UL-94V0 and LOI>50. The maximum current density and the power density of single cell of the composite bipolar plate with 1 phr CNT-mPOP2000 were promoted from 1.03 A/cm2 to 1.32 A/cm2 and from 0.392 W/cm2 to 0.580 W/cm2.These data meet the DOE (Department of Energy U.S.A.)target. The overall performance confirms the bipolar plates prepared in this study are suitable for PEMFC.
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Wang, Jia-ching, and 王嘉慶. "The study on the fabrication of the heterogeneous carbon fiber bipolar plate." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/98351026391629662121.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
100
The advantage for new carbon fiber bipolar plate are as follow, low cost, light weight, low contact resistance and good chemical stability. After process automation, to further reduce costs, enhance quality stability, improve production efficiency, bipolar plates can be achieved mass production. Bipolar plate manufacturing process is divided into five parts:(1) the unfolding of carbon fiber (2) automation of gluing (3) hot-compression harden (4) cutting of carbon fiber bunch (5) Injection molding of bipolar plates. Without leakage, tightness test of the carbon fibers must reach a pressure of 0.2 kg/cm2. The contact resistance is lowest when number of carbon fiber has 160 layers, and compressed fiber bunch height of 2mm on the assembly. Anode inlet pressure is 0.1 kg/cm2. Cathode is required to install a fan. And the fan speed has to cooperate with current load. The quality of carbon fiber bunch will affect the performance of the battery, such as the wide of the rubbers, the flat of the section, Tightness, and numbers of fibers. The structure of the bipolar plate must be considered fuel transfer and number of carbon fibers bunch. Fuel supply and the contact resistance value to achieve a good balance.
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Weng, Cheng-Chih, and 翁政智. "Preparation and Characterization of Carbon Nanotube/Polypropylene Composite Bipolar Plate for Fuel Cell." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/52952305011562490315.
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Wu, Min-Wei, and 吳敏偉. "The Effect of Rapid Thermal Annealing on Carbon-Doped InGaAs/InP Heterojunction Bipolar Transistors." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/42946118578478568405.
Full textAbstract:
碩士國立清華大學
電子工程研究所
90
Abstract We investigate the effect of rapid thermal annealing on Carbon-doped InGaAs/InP heterojunction bipolar transistors（HBT's）.We predicted that, after 700℃ annealing, the p-type dopant can be increased by an order of magnitude, but the InGaAs base doping concentration shows that only about 2-3 fold dopant activation after RTA process. This could be attributed to hydrogen passivation during the growth. However, because of base dopant is activated, not additionally introduced, and less base current are spent on the space-charge recombination,higher gain can be anticipated for RTA device. Finally, we will also present the current gain which is over 100 by reducing the spacer thickness.
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Clifford, Jason Paul. "A self-consistent numerical model for bipolar transport in carbon nanotube field-effect transistors." Thesis, 2003. http://hdl.handle.net/2429/15302.
Full textAbstract:
Carbon nanotube (CNT) field-effect transistors (CNTFETs) utilize a semiconducting CNT
channel controlled by an isolated electrostatic gate. The essential physics of these devices is
captured in a numerical model that allows calculation of energy band diagrams and currentvoltage
(I-V) relationships to describe their behavior.
The numerical CNTFET device model is based on a solution to Poisson's equation that links the
electrostatic potential everywhere in the device to charge induced in the CNT. This charge is a
function of the local electrostatic potential and can be calculated from the carrier distribution
and the local density of states for the nanotube. Under equilibrium conditions the carrier distribution
within the CNT channel is known precisely. However, under non-equilibrium conditions
(when a source-drain bias is present) carrier distributions in the channel are distorted from
their equilibrium forms due existence of hot electrons and holes emitted from the source and
drain, respectively. Quasi-equilibrium Fermi statistics are used to approximate non-equilibrium
carrier distributions using an equilibrium distribution function shifted in energy. Solving Poisson's
equation self-consistently for charge and the electrostatic potential provides a profile of
potential energy along the length of the CNT channel. Current flow in the device is a function
of the ability of carriers to tunnel through or be thermionically emitted over the potential barriers
in the channel. The contribution of both electrons and holes is considered when solving
Poisson's equation and calculating the drain current.
The numerical CNTFET model is a flexible framework for the examination of a wide variety
of device geometries and materials parameters. It employs a finite element package to solve
Poisson's equation in a two-dimensional projection of a cylindrical model space with azimuthal
symmetry. The technique of conformal mapping is used to allow exact electrostatic solutions
in unbounded structures without imposing artificial boundary conditions. The geometry and
materials parameters of the CNTFET are systematically varied and the effects of these changes
are observed in the performance predictions of the model. The model is also used to explore
the behavior of more complex experimental architectures, such as partially gated CNTFETs,
and provides new insight into their operation.
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You, Shun-Hsiung, and 游舜雄. "Cathode performance of carbon-coated metal bipolar plate for polymer electrolyte membrane fuel cell." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/99731228257262165536.
Full textAbstract:
碩士逢甲大學
材料科學所
99
Cathode performance of carbon-coated metal bipolar plates for polymer electrolyte membrane fuel cells (PEMFC) has been investigated. The carbon film was deposited on AISI 304 stainless steel by chemical vapor deposition (CVD). The i-V curves and electrochemical impedance spectroscopy (EIS) of carbon-coated bipolar plates in PEMFC were studied under various conditions, such as the flow rates of reaction gases (200 to 1000 sccm H2 and 400 to 2000 sccm air) and the humidification temperatures (ranging from 25 to 80oC). The efficiency-current density of carbon-coated bipolar plates is demonstrated to be higher (120%) than that of metal bipolar plates. And the results of EIS indicate that using carbon-coated bipolar plate can reduce ohm and electrochemical impedances in fuel cell as compared with metal bipolar plates. After testing, the surface morphology of samples was observed using optical microscope. It is noticed that the corrosion area is reduced on carbon-coated bipolar plates. The content of impurities on MEA cathode examined by energy-dispersive spectroscopy show that the metal content is less as using carbon-coated bipolar plates. In PEMFC both the current density and the electrochemical resistance can be improved by using carbon-coated bipolar plates instead of metal bipolar plates. This composite plate has the potential to replace the commercial graphite bipolar plate.
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LIAO, BO-KAI, and 廖柏凱. "Optimized of PEMFC Hot Running-Layer Composite Carbon Bipolar Plates Using Grey - Taguchi Method." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/h29nsg.
Full textAbstract:
碩士國立虎尾科技大學
機械與電腦輔助工程系碩士班
106
With the rapid development of science and technology, overproduction and over consumption come with high pollution; gradually, a series of destruction has overwhelmed. Fuel cells have the advantages of high efficiency, low noise and low pollution, so it has became the highest potential new energy source recently. Bipolar plate is an extremely important component of fuel cell. At present, the commercial bipolar plate has high development cost and heavy weight, which is not suitable for application. Therefore, this research is to develop a bipolar plate with good light conductivity and good conductivity. As a research goal, the polar plate is expected to have the above two advantages. This research is different from the traditional hot press forming method for producing composite bipolar plates. The rapid and mass-produced injection molding method for preparing composite bipolar plates is expected to reduce the time and cost in this way, and the surface modification is achieved by the new hot pressing method developed by the team. (Polymethylmethacrylate, PMMA) is expected to achieve corrosion resistance and electrical conductivity with its light weight and strong performance combined with the team's own (Tea Graphite, TG). The experimental method of this study is to reduce the time and cost by Taguchi and gray correlation method, discuss the single quality optimization of conductivity and adhesion rate, and obtain the experimental parameters of conductivity and adhesion rate multiple quality optimization, and observe the heat by SEM and OM. In the case of the carbon-coated runner layer composite bipolar plate, the PMMA substrate is bonded to the conductive material TG. The elements and structures and bonds are observed by FTIR, XRD, WCA and EDS. The properties of the material and its heat resistance and electrochemical corrosion are observed by TGA and DSC. The test measures the corrosion resistance, and finally the Proton Exchange Membrane Fuel Cell (PEMFC) single cell is measured for its voltage. The maximum factor affecting the conductivity of Taguchi is hot pressing temperature, and the conductivity of the process parameters optimized for conductivity is 0.99071S/cm; the maximum factor affecting the adhesion rate of Taguchi is hot pressing time, and the adhesion rate is optimized for the attachment of process parameters. The rate is 1.3N.mm.; the gray correlation analysis optimizes the conductivity and adhesion rate multiple quality, the conductivity is not improved compared with the first order L6, and the adhesion rate is increased by 45%; in addition, the XRD results show that the diffraction peak representing the PMMA substrate is 30° in the composite bipolar plate of the hot-pressed carbon channel layer, and the peaks of TG are 24.7°(002) and 43°(101), and the gray correlation The optimization intensity is also better than the first L6 of gray correlation ordering; the characteristic peak position of FTIR observation is that TG is heterogeneous material and the combination does not produce chemical reaction, so there is no displacement; TGA and DSC observation, the material starts gas at around 335℃ Completely gasified at 440℃, leaving about 3% of TG, the substrate is not heat resistant due to TG protection, and because the study is amorphous, only the glass transition temperature is exhibited, and the temperature is about 107℃. The gray correlation optimization WCA=127.5° is the most hydrophobic, but it may cause the hydrogen to fail to adhere to the reaction, and the electrical property is lowered. The electrical measurement results are consistent with the bipolar plate conductivity results, and the conductivity is optimized to have a maximum voltage of 24.1mv.
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Yang, Sish-hung, and 楊士弘. "Studies of Graphite Bipolar Plate applied to a HFC stack and the Performance Studies of a New-type Heterogeneous Composite Carbon Fiber Bipolar Plate." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/50414501326062845879.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
92
The characteristics of the proton exchange membrane fuel cell (called PEMFC) stacks made with the graphite unipolar/bipolar plates are studied in this thesis. Using pure hydrogen as fuel, certain experimental work is conducted to help us to understand the factors which influence on the performance of a HFC stack. The experimental work under various operating conditions starts from single cell stacks to multi-cell stacks. The maximum power is about 200 W, which is made with two 10-cell stacks in series. For simplification, all of the flow channels in the cathode are open type in which air is directly supplied from ambient by fan. The comparison of the performance of two single cells, which are made with both a graphite unipolar plate and a new-type carbon fiber unipolar plate, is conducted. The total resistances of the two types of bipolar plates with gas diffusion layers are tested to help us to understand their strong or weak points. The experimental results display that the double inlets has better performance than the single inlet due to larger entrance space. Increasing the applied torque will reduce the contact resistance between bipolar plate and diffusion layer and also the gaps between the fibers of carbon cloth. Reducing the contact resistance is helpful in increasing the performance of the cell, but reducing the gaps between fibers will inhibit the entering of reactive gas and is unfavorable for performance; therefore, the proper torque is necessary to obtain the best voltage output. When air is used as an oxidizer and the flow channel is an open type channel, the fan in high rotating speed is helpful at high current density. The high air volume flow rate can supply sufficient oxidizer and avoid the decay of the voltage output at high current density. At the current density 1 A/cm2, the power density of the single-cell stack is about 400 mW/cm2 and the power density of the 10-cell stack is down to about 310 mW/cm2 in our experiment. The rib of the carbon fiber unipolar/bipolar plate is soft, so there is no deformation in the gas diffusion layer in stack assembly. Only slight compression is needed to assemble a stack; therefore, the reactive gas can easily flow into the most of active area. This type unipolar/bipolar plate is made with low density plastic except that the rib is made with carbon fiber bunches. Thus the new plate is weight light, cost low and volume small. So it is quite possible that the new-type of carbon fiber plate is used as substitution for the graphite bipolar plate in the future. In that case the light, low cost and high performance choice can be achieved.
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Huang, Cheng-Hao, and 黃政豪. "Preparation of Carbon Films by CVD Process for the Applications of PEMFC Metallic Bipolar Plates." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/19487564307638016742.
Full textAbstract:
碩士逢甲大學
材料科學所
93
Bipolar plates have to accomplish many functions in polymer electrolyte membrane fuel cell (PEMFC). The main functions are: electric conductivity, corrosion resistance, chemical stability, mechanical strength and density. Metallic bipolar plates are focus of the investigations. The advantages of graphite film coated on stainless steel are their excellent corrosion resistances, electric/thermal conductivity, reduce cost, volume, and weight. Nickel has been known to be an efficient catalyst for the graphitization of amorphous carbon. Nickel layer is deposited on stainless steel by plasma assisted physical vapor deposition (PAPVD). Carbon film was obtained by chemical vapor deposition (CVD) on nickel layer. In CVD process, methane is carbon sources, argon or hydrogen is used as carrier gas. The properties of the film were investigated by scanning electron microscope (SEM), grazing incident X-ray diffraction (XRD), Raman spectroscopy and electrochemical analysis. The results reveal that increasing carrier gas flow can promote catalytic graphitization. With the carrier gas is hydrogen, the ratio of D mode to G mod is lower than 0.1. The carbon films coated on substrate can improvement in resistances to corrosion. Although the continuous carbon film was observed, but it can’t provide for more resistances to corrosion.
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Chen, Tsung-Han, and 陳宗漢. "Diamond-Like Carbon/Aluminum Plate for the Bipolar Plate of Proton Exchange Membrane Fuel Cell." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/57686900686277646600.
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Chen, Wei-Jen, and 陳韋任. "Preparation and Characterization of Carbon Nano Tube / Phenolic resin Nanocomposites for Fuel Cell Bipolar Plate." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/94088797259148467824.
Full textAbstract:
碩士中原大學
機械工程研究所
92
ABSTRACT Electrical conductive bipolar platse for fuel cell prepared by phenolic resin modified by conducting filler with Bulk Molding Compound (BMC). The conductive fillers used wes graphite, nickel-coated graphite powder(Ni-Graphite) and nickel-coated carbon fiber (Ni-Carbon fiber) and carbon nanotube(CNT). The electricat conductivity bipolar plate with the nickel-coated carbon fiber content increase from 31S/cm(2wt%)to 195S/cm(8wt%) and the electricity conductivity with the Ni-Graphite content increased from 0.56S/m(5wt%) to 1.57S/cm(30wt%). Thermal conductivity of the bipolar plate increase from 54.6W/m-K to 63W/m-K white CNT content from 0.1phr to 0.3 phr. Oxygen permeability decreass from 1.07 x 10-6 mL/cm2-sec to 9.68 x 10-8 mL/cm2-sec white CNT content 0.01phr to 0.3 phr. The limiting oxygen index(L.O.I.)and the UL-94 test revealed that the bipolar plate possesses excellent flame retartance which L.O.I. > 50 and UL-94 to conform to UL-94V0.
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Li, Dong-Syuan, and 李東軒. "Preparation and charaterization of the Epoxy /Carbon nanotube composites as bipolar plate of fuel cell." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/48273041300167375338.
Full textAbstract:
碩士國立雲林科技大學
化學工程與材料工程研究所
97
This study investigates the preparation and properties of polymer composite bipolar plates for use in proton exchange membrane fuel cells (PEMFCs). The composites contain epoxy resin, graphite powder and multiwalled carbon nanotube (MWCNT). The polymer composite bipolar plates were fabricated by compression molding process. The MWCNTs based studies include prinstine CNT (P-CNT), acid modified CNT (A-CNT), and functionalized MWCNT (GPT-CNT) prepared by grafting (3-glycidoxypropyl) trimethoxysilane (GPT) to graft on MWCNT. The first part confers the effect of the graphite powder content on the electrical, mechaical, physical, thermal properties and cross-section surface morphology. The optimum graphite powder content was 90 wt.%. The electrical conductivity achieved 6.58 S/cm, the impact strength attained 42.52 J/m and the porosity achieved 30.22%. The thermal stability showed the temperature of degradation could achieve 350℃. The morphology was displayed the graphite presented in a regular arrangement. The second part confers the effect of the replacement amount of GPT-CNT on the electrical, mechaical, physical, thermal properties and cross-section surface morphology. The result showed that when GPT-CNT replaced 10 wt.% of graphite powder, the electrical conductivity was enhanced from 6.58 S/cm to 33.33 S/cm, the impact strength was decrease from 42.52 J/m to 23.95 J/m and the porosity was increased from 30.22% to 44.32%. The thermal stability displayed the temperature of degradation was dropped from 350℃ to 300℃. The morphology was observed that the clear difference between EP-G90 and EP-G90-NT10. The EP-G90-NT10 was presented in an irregular arrangement and observed that the GPT-CNT was observed to aggregate together.
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Wang, Chi-yin, and 王啟銀. "The Theoretical Studies and Numerical Simulations Of The Effects Of Heterogeneous Composite Carbon Fiber Bipolar Plates And Traditional Hard Surface Bipolar Plates On The Flow Field." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/36744872587364261016.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
94
In this thesis the numerical method is adopted to study the flow characteristics of reactants, when the newly developed heterogeneous composite carbon bipolar plate and the traditional hard surface bipolar plate are applied to fuel cells. The simulation in this study includes the distributions of the velocity and pressure of oxidizers flowing in a parallel or serpentine flow channel under several inlet gas flow rates and pressures. The difficulty to supply reactant to the active area under the ribs is also studied in this thesis. From these studies we can understand the strong and weak points of the newly developed bipolar plates and the traditional bipolar plates better. The simulation results display that the gaseous reactants or products can permeate through the gaps between carbon fibers into or out of active area under the rib, which is formed with carbon fiber bunches. Therefore more reactant gases can be supplied with the heterogeneous carbon fiber bipolar plates than the graphite bipolar plates. In addition, the higher efficiency of fuel cells can be obtained with the new plate, especially in high power density. The pressure distribution in making use the heterogeneous carbon fiber bipolar plates are more uniform, and the pressure drop is also less than the traditional bipolar plates. For large fuel cells the current distribution will be more uniform and the pumping power will be less. The reactant gases can flow through the gaps of carbon fibers and the porous carbon cloth into the catalyst layers by convection and diffusion. So no matter what type of the flow channels used the needed oxidizer is much less with the new bipolar plate than with traditional one. The flow fields of the two types of bipolar plates are quite similar, but the gas needed to supply is also much less with the new plate. Because of the advantages mentioned above, we believe that the heterogeneous carbon fiber bipolar plate is better than the traditional graphite bipolar plate. Keywords: fuel cell, heterogeneous carbon fiber bipolar plate,hard surface bipolar plate
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Tseng, Sheng-Hsiu, and 曾聖修. "Mechanical and Electrical Properties of Bipolar Plate of Fuel Cell Mixed with Utillize Phenolic Resin/Molybdenum Hexacarbonyl To Prepare Carbon/Carbon Nanocomposites." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/64979743774280611612.
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Su, Feng-chien, and 蘇烽堅. "Studies of the High Performance New-type Carbon Fiber Bipolar Plate Applied to a DMFC Stack." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/76090916752105328422.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
92
The experimental test and analysis of the direct methanol fuel cell (DMFC), which is made with a newly developed heterogeneous composite carbon fiber unipolar/bipolar plate, is performed in our lab. The work from the making of carbon fiber unipolar plate to the design of single-cell DMFC is also included in this study. The experimental work of various control parameters, such as methanol concentration, operating temperature, and the air flow rate, is also conducted in this thesis. The formation of carbon dioxide in anode is inspected during experiment. From a series of experimental test, we have understood the characteristics of DMFC better. The experimental result and experience can also provide the references of the application and development of DMFC in the future. According to our experiment, we find that the assembling of the new-type unipolar/bipolar plate doesn’t need to use the large compressing force to reduce the contact resistance like those of the traditional unipolar/bipolar plates. The structure of the DMFC stack made with the new carbon fiber unipolar/bipolar plate is simple and weight light. However, the experimental results still show that the factors that affect the performance of the DMFC fuel cell are similar to those with the conventional unipolar/bipolar plates. For example, increasing the reactive temperature of fuel, proper methanol concentration, and proper content of catalyst all can effectively improve the power density of a DMFC. The structure of the methanol mixture directly stored in the flow channel of the anode is simple. However, the design exists the problems of the crossover of methanol, the stripping of the anode electrode, and the removal of the carbon dioxide. Special attention is needed to overcome and improve those problems in making DMFC stacks. Or the performance of the cell will decline after long period operation.
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Liao, Shu-Hang, and 廖述杭. "Preparation and Properties of Carbon Nanotubes/Polymer Nanocomposite Bipolar Plates for Proton Exchange Membrane Fuel Cells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/qv6e59.
Full textAbstract:
博士國立清華大學
化學工程學系
98
The objectives of this research are the preparation and characterization of multiwalled carbon nanotubes (MWCNTs) and functionalized MWCNTs/polymer nanocomposite bipolar plates for use in proton exchange membrane fuel cells (PEMFCs). There are four parts in this dissertation. The first part of this dissertation investigates the novel functionalized multi-walled carbon nanotubes (MWCNTs) which are used as cross-links between MWCNTs-vinyl ester interfaces to achieve homogeneous dispersion and strong interfacial bonding for developing fully integrated MWCNTs-vinyl ester nanocomposite bipolar plates. POAMA (i.e. poly(oxyalkylene)-amines (POA) bearing maleic anhydride (MA)) are grafted onto the MWCNTs by amidization reaction, forming MWCNTs-POAMA. In the MWCNTs-POAMA/vinyl ester nanocomposites, MWCNT-POAMAs react with vinyl ester and become part of the cross-linked structure, rather than just a separate component. It was found that MWCNTs-POAMA exhibited better dispersion in the vinyl ester matrix than those of pristine MWCNTs. Moreover, results demonstrate that the mechanical and electrical properties of the vinyl ester nanocomposite bipolar plate are improved dramatically. The ultimate flexural strength and bulk electrical conductivity of the MWCNTs-POAMA/vinyl ester nanocomposite bipolar plate are increased from 28.54 MPa to 41.44 MPa and 156 S cm-1 to 643 S cm-1, exhibiting 45 and 315 % improvement, respectively. The gas tightness of all of composite bipolar plates in this study was no leak. In addition, the maximum current and power densities of the single fuel cell test using the MWCNTs-POAMA/vinyl ester nanocomposite bipolar plates were enhanced from 1.03 to 1.23 A cm-2 and from 0.366 to 0.518 W cm-2, respectively, which suggested that a higher electron transfer ability for PEMFC applications can be achieved. The second part of this dissertation investigates a novel one-step preparation of functionalized multi-walled carbon nanotubes (MWCNTs) by free-radical modification. MA-POA, i.e. Maleic anhydride (MA) grafting molecular weight 400 and 2,000 poly (oxyalkylene)-amines (POA400 and POA2000), was attached onto the MWCNTs, forming MWCNTs/MA-POA400 and MWCNTs/MA-POA2000. The functionalized MWCNTs, especially MWCNTs/MA-POA2000, exhibited higher solubility than the pristine MWCNTs in organic solvents and showed well dispersion in the vinyl ester matrix. Furthermore, this study also investigated the mechanical, electrical and single fuel cell properties of functionalized MWCNT nanocomposite bipolar plates for use in polymer electrolyte membrane fuel cells. The flexural strength of the nanocomposite bipolar plates containing 2 wt% MWCNTs/MA-POA2000 was increased from 28 MPa to 48.33 MPa, exhibiting 73% improvement. In addition, the bulk electrical conductivity of the nanocomposite bipolar plates was 780 % (from 156 to 1340 S cm-1) higher than those of the original composite bipolar plates by adding only a small quantity (1 wt%) of MWCNTs/MA-POA2000. The maximum current density and power density of the single cell tests of the nanocomposite bipolar plate with 1 wt% MWCNTs/MA-POA2000 were enhanced from 1.03 to 1.32 A cm-2 and from 0.392 to 0.587 W cm-2, respectively. The overall performance confirms the MWCNTs/MA-POA2000 nanocomposite bipolar plates prepared in this study are suitable for PEMFC application. The third part of this dissertation studies the fabrication of lightweight and high performance nanocomposite bipolar plates for the application in proton exchange membrane fuel cells (PEMFCs). Three types of polypropylene (PP) with different crystallinities including high crystallinity PP (HC-PP)、medium crystallinity PP (MC-PP) and low crystallinity PP (LC-PP) were prepared. The optimum composition of original composite bipolar plates was determined with 80 wt% graphite content and 20 wt% PP content based on the measurements of electrical and mechanical properties with various graphite contents. Results indicated that MWCNTs was dispersed better in LC-PP than other PP owing to enough dispersed regions in nanocomposite bipolar plates. The good MWCNT dispersion of LC-PP causes better bulk electrical conductivity and mechanical properties of MWCNTs/PP nanocomposite bipolar plates. In the MWCNTs/LC-PP system, the bulk electrical conductivity of 4 wt% MWCNTs/LC-PP nanocomposite bipolar plates increases from 160 S cm-1 (0 wt%) to 548 S cm-1, exhibiting 242 % improvement. The flexural strength of the MWCNTs/LC-PP nanocomposite bipolar plate with 8 wt% of MWCNTs was 29.46 MPa, approximately 37 % higher than that of the original nanocomposite bipolar plate. The single cell performance of MWCNTs/LC-PP nanocomposite bipolar plate was also evaluated. The maximum current density and power density of the single cell tests of the nanocomposite bipolar plate with 4 wt% MWCNTs/LC-PP were 1.19 Acm-2 and 0.533 Wcm-2, respectively. The four part of this dissertation investigates the preparation of aminated mullti-walled carbon nanotubes (MWCNTs-NH2) attached with polypropylene grafted maleic anhydride (PP-g-MA compatibilizer) by ring-opening reaction. The prepared MWCNTs/PP-g-MA was introduced to the PP/composite bipolar plates, to achieve a high compatibility and good adhesion between carbon nanotubes and PP matrix via PP-g-MA chains. Replacement of amine-terminated groups by PP-g-MA in the MWCNTs leads to the grafting of long copolymer chains to the MWCNTs, and improves the dispersion of MWCNTs. Due to the strong reinforcing properties of MWCNTs, the electrical and mechanical properties of the PP composite bipolar plates were enhanced. The effect of incorporating MWCNTs/PP-g-MA on the morphology, electrical and mechanical properties of the PP-based composite bipolar plates was studied. The resulting PP composite bipolar plates with 1, 2, and 4 wt% of MWCNTs/PP-g-MA demonstrate the flexural strength and the bulk electrical conductivity were improved by 56.3, 68.5, and 70.9 % and by 282, 425, and 473 %, respectively. Comparing with the maximum power density of the graphite bipolar plates (0.614 W cm-2), the MWCNTs/PP-g-MA PP nanocomposite bipolar plates (0.586 W cm-2) are suitable for bipolar plates of PEMFCs.
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chang, chi-an, and 張志安. "Studies From Reactant Supply for Heterogeneous Composite Carbon Fiber Bipolar Plates Applied to a Fuel Cell." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/14587401326643862277.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
93
Via the viewpoint of fuel and oxidant supply in this study, we compare heterogeneous carbon fiber bipolar plates with graphite bipolar plates that apply to fuel cell. In operating condition with different gas inlet pressure and compressing pressure, we study the penetrability of reactant gases that come into the carbon cloth under the rib of a bipolar plate. Eventually the output voltage and power density are measured to prove the advantages of the new bipolar plate. The experimental results show that carbon fiber bipolar bunch in low compressing pressure 2bar already display high gas penetrability. Its dimensionless flow rate is about quadruple of graphite bipolar plates. The reactant gas can enter the carbon cloth either from the side or from the top of the penetrating carbon fiber bipolar bunch. In addition, carbon fiber bipolar plates are affected slightly by compressing pressure. Further, the total electrical resistant of carbon fiber bipolar plates with carbon cloth already decreases to 18.5mΩ*cm² in low compressing pressure 2bar. Therefore, by appling the new bipolar plate, the fuel cell in compressing pressure 2bar and inlet fuel pressure 1.15bar(absolute pressure) can developed a power rate 180mW/cm². Concerning graphite bipolar plates, we can find that compressing pressure increase from 1bar to 4bar due to the reduction in total resistance so the output voltage and power density can increase to maximum value 113mW/cm2. However, while we augment more compressing pressure, the influence in reducing total resistance is much smaller than that in reducing the porosity of carbon cloth. Therefore, the output power density decreases. Also, output voltage of carbon fiber bipolar plates at 0.5mA/cm2 is 0.38 V and is higher than that of graphite bipolar plate 0.2 V.
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Hsiao, Min-Chien, and 蕭閔謙. "Preparation and Characterization of Carbon Nanomaterials Reinforced Composite Bipolar Plate for Proton Exchange Membrane Fuel Cells." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55366812054070768964.
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su, syuan-jie, and 蘇鉉傑. "Studies of a New-type Heterogeneous Composite Carbon Fiber Bipolar Plate Applied to a Portable DMFC stack." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/03863403846718258839.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
93
Several disadvantages in general unipolar/bipolar plates are that cost is expensive, weight is heavy and the volume is large. The high compressing pressure is also necessary to reduce the contact resistance in making up a fuel cell stack. Therefore, it is difficult in making use general unipolar/bipolar plates to portable fuel cells. With a new heterogeneous carbon fiber bipolar plate, pumpless and air-breathing design and in cooperating with a special MEA, a portable fuel cell stacks developed in our lab have made portable applications to be possible. The structure of the DMFC stack made with the new carbon fiber bipolar plate is much more simple and weight-light than the other designs. The three portable DMFC stacks flat type, cylinder type (I), and cylinder type (II) are developed in series in our lab. The methanol solution can be stored directly in the flow channel of the anode, and does not need the extra auxiliary equipment, so it easy to apply to the portable fuel cell. The developed portable DMFC of cylinder type (II), weight is only 20g, volume is 30cm3, and the fuel stored capacity is 7.5ml. In the flat type DMFC, In anode Pt-Ru loading 3 mg/cm2, and cathode Pt loading 1 mg/cm2, methanol concentration 3 M, pumpless, air-breathing, and room temperature, the largest of output power density of the fuel cell can reach 5.27 mW/cm2, and the total power can reach 71 mW. The weight of DMFC of cylinder type (II) is far lower than DMFC of flat type in addition, so its power density 1.33mW/g is about 1.68 times of flat type 0.79 mW/g.
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Chien, Po-Hsiu, and 簡伯修. "The study in characteristics of chromized coating on SS430 stainless steel and high-carbon steel bipolar plates." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/08159915034826988500.
Full textAbstract:
碩士國防大學理工學院
材料科學碩士班
98
In this study, AISI 1080 carbon steel and SS430 stainless steel are used as the substrates. The rolling or Ni-electroplating technieque is employed as a pretreatment to produce many defects on the surface of the substrate, and then the low temperature (700℃) pack chromium-nickel co-deposition is carried out to improve the corrosion resistance and interfacial contact resistance of the steels. The pack powder mixture composes a codeposition master (chromium-nickel), activator (NH4Cl) and inert filler (Al2O3). The powder mixture is mixed up in accordance with a suitable proportion in order to produce the anti-resistance coatings with rich-chromium and a little amount of nickel. The XRD results show that the coating mainly composes of (Cr, Fe)7C3 and (Cr, Fe)23C6 phases, and little amount of nickel oxides. The co-deposition specimens are conducted with potentiodynamic and potentiostatic test in a 0.5 M H2SO4 solution. The results show that the corrosion potential of SS430 stainless steel treated with chromium-nickel co-deposition can be improved from -0.47 V to 0.05 V, and the corrosion current density can be reduced from 2.6E-3 Acm-2 to 9.86E-8 Acm-2. The corrosion potential of AISI 1080 carbon steel treated with chromium-nickel co-deposition can be improved from -0.5 V to 0.4 V, and the corrosion current density can be reduced from 3.2E-3 Acm-2 to 4.98E-7 Acm-2. Potentiostatic results show that the specimen treated with chromium-nickel co-deposition is more stable than that of simple chromized specimen, which verified that a small amount of nickel in the chromized coating is more stable and can prevent the coating from pitting corrosion in the simulated PEMFC environments. The Ni-electroplated and chromized specimens exhibit better corrosion resistance than simple chromized specimens as a result of the thicker chromized coating and less amounts of Fe in the coatings, which indicated that the nickel electroplated layer can not only improve the diffusion rate of elements greatly, but alse serve as a barrier layer to enhance the corrosion resistance and interfacial contact resistance of the coating produced in the same processing conditions.
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Pan, Shih-yuan, and 潘世原. "Numerical Studies of the Effects of the Flow Channel Structures of Heterogeneous Composite Carbon Fiber Bipolar Plates and Traditional Hard Surface Bipolar Plates on the PEMFC Flow Field and Performance." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/b4w8z2.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
95
In this study a three-dimensional mathematical model is developed to simulate the flow field and mass transfer in a PEM fuel cell. In the model, the effects of the different flow channel structures in heterogeneous composite carbon fiber bipolar plates and traditional hard surface bipolar plates on the performance are studied. The results show that, the cell performance with the heterogeneous composite carbon fiber bipolar plates have better performance than that with the traditional hard surface bipolar plates, whether in the parallel flow channel structures or the serpentine flow channel structures. The reason is that, the heterogeneous composite carbon fiber ribs are porous material, so it allows the reactants and products transport uniformly even in the rib zone. This greatly improved the mass transfer and the gases distribution in the fuel cell. With the traditional bipolar plates, the reactants can only enter the reaction zone from the side of carbon cloth under ribs, so that the performance in this area under rib is relatively poor. In the simulation of the flow channel structures, we detect that, due to the single inlet serpentine flow channel have stronger convective effects that forced reactants to flow through the whole reaction zones, so it has better performance at high current density than in the singles inlet parallel flow channel. In addition, the results also show that, higher fuel stoichiometric number and operated pressure and properly humidified at anode will all improve the performance of the fuel cell.
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Chen, Wei-cheng, and 陳威呈. "Studies of the Structure of Carbon Fiber Bunch Unipolar/Bipolar Plates on the Performance of PEM Fuel Cell." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/00387743496056865138.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
98
The effects of the structure of new carbon fiber bunch heterogeneous unipolar plates on the performance of PEMFC are studied in this thesis. Internal structure of carbon fiber bunches can be modified by embedding different thickness or number of copper plates in the glue bonding area to increase the air permeability of carbon fiber bunches in its soft end. We can add different thickness or amount of coppers at the middle of bonding area, making the carbon fiber bunches soft side to form parallel to the longitudinal fiber bunch with a small flow channel. We can also make a trench at the appropriate place of the soft side of the carbon fiber bunches to form an extra air passage. In order to make the above flow channel, a new process for making the carbon fiber bunches is developed also. This process will be easier to produce a variety of different structures of carbon fiber bunch. Finally, several different experiments are performed to help us to understand the effect of the carbon fiber bunch structure on the performance and find out the best structure of the carbon fiber bunches. The carbon fiber bunch structures of the test cells on the anode side are all the same, but the carbon fiber bunch structures of on cathode side are all different. Experiments show that there are two structures among all test structures displayed better gas permeability. The first one is two 0.2 mm copper plates embedded within both sides of the glue ends of a cathode carbon fiber bunch, so that a small longitudinal flow channel are formed in soft end of the cathode carbon fiber bunch. When the HFC operates at room temperature and by air-breathing, the highest performance of the HFC can reach a value of 185 mW/cm2. The second one is a 0.2 mm copper plate embedded in the center of the glue end of a carbon fiber bunch, and then three 2 mm wide serrated slots are cut on the soft end of the carbon fiber bunch. The highest performance of the HFC can reach a value of 190 mW/cm2. The highest performance of the HFC with no copper plate and no slot structure can only reach a value 160 mW/cm2. The second design can increase the no structure cell performance 18.8%. Therefore, the internal structures of carbon fiber bunches are significant to affect on the fuel cell performance, and its internal design must be considered.
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Chen, Cheng-Chieh, and 張程傑. "Study on Bipolar Plate of 1045 Carbon Steel Chromized by Pack Cementation with Various Electroplated Cr-C Pretreatments." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/24897131520283556590.
Full textAbstract:
碩士國防大學理工學院
材料科學與工程碩士班
100
Abstract AISI 1045 carbon steel, as a substrate, was electroplated with nickel to form a layer of microcrystalline and then followed by a thin Cr-C electroplated deposition. These two electroplated layers provide a pretreatment for the activation of Cr-C coating available in the pack cementation process at a lower temperature 700℃. Four varied Cr-C electroplating sources has been selected and operated with different operating time. After pretreatment, samples were chromized with chromium powder for 2 hours to produce a Cr-C coating. The experimental results were analyzed to verify the one(s) with high corrosion resistance and electrical conductivity. The results show that the samples of 1045-Ni-CrC (Cl3-5)-Cr (700-2) have a prominent performance over the others. The SEM observations show that the coating surface of specimens has a dense and continuous appearance. The XRD analyses show that the phases formed are chromium-carbides and few chromium-nitrides. The potentiodynamic test were carried out with 0.5 M H2SO4 solution at room temperature, whereas the potentiostatic test with 0.5 M H2SO4 solution at 80 ℃ for 1 hr with air bubbling. It is found that the corrosion potential for the Cr-C coating increases with the additional Cr-C layer, and the corrosion current decreases in a stable manner. Interfacial contact resistance observed at 140N/cm2 pressure renders to a lower value. These performances prove that the electrodepositing Cr-C layer, during the low-temperature pack chromization, significantly helps to form a sound Cr-C coating with high corrosion resistance and electrical conductivity.
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Ou, Cheng-Chung, and 歐政忠. "Study on the Manufacture Process and Property of Expandable Graphite/Powder Epoxy/Carbon Fiber Bipolar Plate for PEMFC." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/fwk9h8.
Full textAbstract:
碩士國立虎尾科技大學
材料科學與綠色能源工程研究所
101
PEMFC is an electrical device which directly converts chemical energy of fuel and oxidant to electricity. Compare with a heat engine or a rechargeable battery, PEMFC has high efficiency of energy transform. The main capability of a bipolar in fuel cell is to distribute fuel and oxidant to the membrane electrode and to provide electrically connection between neighboring single cells. In this research, the composite plates are made of mixture which include expandable graphite、powder Epoxy and carbon fiber by hot-press process. The purpose of this paper is to study the influence of type of carbon fiber(short carbon fiber、plain weave carbon fiber、three-dimensional structure carbon fiber、plain weave carbon fiber prepreg) on the mechanical and electrical properties of the expanded graphite bipolar plates made by hot-press method. All properties decrease when content of short carbon fiber is over 13.5%. The type of plain weave carbon fiber can promote mechanical property. The type of three-dimensional structure carbon fiber can improve heat conduction property, but permeability is so bad. Plain weave carbon fiber prepreg enhance the binding force of expandable graphite and carbon fiber, it promote permeability. The manufacture condition of bipolar is expandable graphite and 30% powder Epoxy and add in 5 pieces(1 piece) plain weave carbon fiber. The characteristic IV curves and IP curves of the fuel cells are obtained from the single fuel cell tests. The results of add in 5 pieces plain weave carbon fiber that the great current density of 2080 mA/cm2 occurs at 0.3 V, and the highest power density of 759 mW/cm2 occurs at 0.5 V. The results of add in 1 pieces plain weave carbon fiber that the great current density of 2240 mA/cm2 occurs at 0.3 V, and the highest power density of 807 mW/cm2 occurs at 0.4 V.
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Chiang, Pei-Hsin, and 江沛忻. "Study on the Manufacture Processes and Properties of the Carbon Fiber/Graphite Base Bipolar Plate of Fuel Cell." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/5gpvjt.
Full textAbstract:
碩士國立虎尾科技大學
材料科學與綠色能源工程研究所
102
This study is based to graphite composite material. Adding carbon fiber, metal mesh as a reinforced material and discuss the composition, process and property. The experiment with powder epoxy as a binder. Adding to graphite or expanded graphite and mixed then hot press with thickness 2mm. To understand different reinforced material mechanical properties, electrical conductivity, impermeability and thermal conductivity impact to composite plate. Finally, find the most apposite composite conductive plates. And use this process to produce two kinds of graphite bipolar plates assembled single cell measured IV and IP curves. Were analyzed as graphite and expanded graphite substrate performance differences. The results are displayed the metal mesh for the delivery of electrical and thermal energy have great help. But the transfer of mechanical energy because of insufficient base strength of the relationship was significantly weaker. And because the properties of the metal substrates and can’t freely choose to use. Metal compare the carbon fibers thermal expansion coefficient is the smaller. So this based material can be used graphite powder. In the test can be found the graphite through carbon fibers can be impact to the property. Adding 240k carbon fibers can get a good electrical conductivity as 0.971 mΩ, but it loses the mechanical properties and the impermeability. After testing the carbon fiber prepreg further combination with carbon fibers in a layered composite of two electrically conductive graphite plates. The composite plates can be get the good mechanical properties, that even can over 60 MPa. Impermeability also has the good level like the high density carbon fibers composite plate. So final choose is the layer composite plate and high density carbon fiber composite plate. The plate density 1.3 g/cm3 expanded graphite plate can get the highest power density 682 mW/cm2 in voltage 0.36 V. And the plate density 2 g/cm3 graphite plate can get the highest power density 662 mW/cm2 in voltage 0.36 V.
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Jhan, Ting-Wei, and 詹庭惟. "Study of the Properties of Graphite Base Bipolar Plate of Fuel Cell with Different Carbon Fiber Structure and the Evaluation of Different Release agents During the Manufacture Process of Bipolar Plate." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/8k3bys.
Full textAbstract:
碩士國立虎尾科技大學
材料科學與工程系材料科學與綠色能源工程碩士班
104
This thesis is to explore several properties of PEMFC bipolar plate which were made of different carbon fiber structures with different states of epoxy, and to discuss several release agents for the hot-press molding process. In this research, the 2mm-thick bipolar plates were made of the mixture of liquid or solid powdery epoxy and graphite with several kinds of carbon fiber structures by hot-press molding process. The main issue of this study is on the influence of the structure type of carbon-fiber (different three-dimensional structures of woven carbon fiber sheet) and the state of epoxy on mechanical properties, electrical conductivity, and thermal conduction of the composite plate. And finally, the single fuel cell tests were completed to obtain the IV curves and IP curves of the fuel cells, which bipolar plates with mass density of 2g / cm3 were made of the mixture with the content of above composites.The experimental data reveal that electrical conductivity of the specimens made of powder epoxy is better than the one made of liquid epoxy. However the mechanical properties of the specimens made of liquid epoxy is better than the one made of powder epoxy. It reveals that specimens made of powder epoxy have much more closed-circuit, and the specimens made of liquid epoxy have higher bonding force. It can outstanding improve the mechanical properties and electrical conductivity of a bipolar plate by addition of carbon fiber structures.The results reveal that the fuel cell with bipolar plates reinforced by carbon fiber structure and powder epoxy has the highest power density of 830.394 mW/cm2 occurs at 0.369V. This study also used several release agents or membrane and release methods to make bipolar plates remove smoothly from the hot pressing mold. The result reveals that a few folds emerged when Teflon membrane was used as release membrane. This resulted in gas leaking. There was shear stress between silicone oil and wall of mold during hot pressing when silicone oil was used to be release agent, silicone oil was dispersed and graphite adhered to the mold wall. If Zinc stearate was utilied to be the external mold release agent, the bipolar plate can remove smoothly from the hot pressing mold.
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Chou, Chin-Hui, and 周晉輝. "Study on the Manufacture Processes and Properties of Fuel Cell Bipolar-Plate Made of Aluminum/Carbon Fiber Corrugated Sheet." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/48suqa.
Full textAbstract:
碩士國立虎尾科技大學
材料科學與綠色能源工程研究所
102
PEMFC is a perfluorosulfonic acid type solid polymer electrolyte, a platinum / carbon electrocatalyst, Purifying recombinant or hydrogen gas as fuel, air or pure oxygen as the oxidant. Graphite or a metal plate surface modified with a gas flow channel as a bipolar plate, bipolar plate with the function of the reactive gas transport, both sides are machined or uniform distribution of the reaction gas flow field channels, In order to ensure uniform distribution of the reaction gas in the electrodes. In this research, the carbon fiber prepreg material, carbon fiber woven with graphite powder, graphite, aluminum foil laminated together with a mixture, by hot-press molding process. The purpose of this paper is to study the extent of the carbon fiber woven fabric density, powder type and aluminum foil on the mechanical and electrical properties of the expanded graphite bipolar plates. From the results, the addition of expanded graphite, graphite powder significantly improved plane conductivity than the original composite board, For the mechanical properties had no significant effect. Join the 3K、 12K carbon fiber woven to produce the composite panels, because of the uneven surface to produce the effect on the electrical properties, and after adding aluminum foil for improved heat conduction effect, but will let conductivity deteriorates. Based on the above results, to add a different powder in carbon fiber prepreg, have a conductive path is formed between carbon fibers, for plane conductivity, penetration resistance with good enhance results. The results reveal that the fuel cell with carbon fiber prepreg * 6 + graphite(20％epoxy) has the great current density of 1054 mA/cm2 occurs at 0.28 V, and the highest power density of 295.68 mW/cm2 occurs at 0.48 V.
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Hsu, Fu-Ming, and 許富明. "Electric/Electromagnetic fields include alignment of nickel-coated carbon fiber in epoxy resin substrate and Applied to fuel cell bipolar plates." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/35880727943093383774.
Full textAbstract:
碩士國立交通大學
機械工程學系
98
Physical properties are tunable by mixing fibers into the base material. Product anisotropy is achieved by controlling fiber alignment during the formation process. The researchers in this study manufactured a rectangular plate with anisotropic physical properties. The plate contained nickel-coated carbon fiber of high electrical conductivity and epoxy resin with a supreme physical property. An electrical and electromagnetic field generator was designed and fabricated to modulate electric and electromagnetic fields during solidification in the casting process. This study investigated fiber alignment of nickel-coated carbon products under the influence of different force fields. In the first section of experiments, the effects of electric and electromagnetic fields on fiber alignment were examined. This study utilized Optical microscopy (OM) to observe alignment of fibers, and penetrative conductivity measurement devices for fiber alignment verification were used. The researchers treated epoxy resin with an electric field to induce fiber alignment. Electric field experiments revealed that, the fibers did not satisfy electrophoresis properties and failed to aggregate and align when no electrical transition and aggregation occurred. The procedure of using the electric field to induce fiber alignment in epoxy resin is not applicable for mass production of virtual products with high electrical conductivity. The results of electromagnetic field experiments demonstrated that nearly all fibers aligned perpendicular to the magnetic field under certain conditions: such as, system magnetic flux density 0.069 Tesla, specimen thickness 2 mm, fiber content 0.5 wt percentage, length 1 mm, and certain resin viscosity. Compared to specimens that did not undergo aligning treatment, the penetrative conductivity (under 200MΩ) increased from 18.75% to 84.37%. The study used the experimental conditions fiber density 0.4, 0.6, and 0.8wtpercentage, length 2mm. The penetrative conductivity decreased while the fiber content increased. Fiber content ranged from 100%, 75%, and 72.9%with changed conductivity from 25, 125, and 250 Ω. The method of inducing fiber alignment with electromagnetic fields is applicable to the manufacture and development of products requiring anisotropic properties under certain levels of enhancement of system magnetic flux density. Research reports on fiber alignment control of nickel-coated carbon and its application in manufacturing fuel cell bipolar plates are nonexistent. The second phase of the experiment focused on whether the procedure of fiber alignment along the penetration direction of the epoxy resin rectangular plate is applicable to fuel cell bipolar plates. The researchers milled the composite and graphite plates to create serpentine flow fields. These two materials were compared for single cell power generation performance. Results showed that the composite of interest qualified under the Department of Energy (DOE) requirements for thermal properties, gas permeability, and corrosion resistance for fuel cell bipolar plates. The maximum power density of the composite bipolar plate was 1% (2.1mW) of the graphite counterpart under the conditions of fiber content 0.4 wt%, length 2 mm, magnetic flux density 0.069 Tesla, and plate dimensions of 63×54×2 mm. The maximum power density results were due to the greater penetrative resistance of the composite bipolar plate. The researchers utilized composite material with a planar conductivity of greater than 200MΩ; therefore, the electricity generated was mainly due to the conductive current provided by the penetrative conductivity of the bipolar plate. The study concludes that the procedure of conductive fiber alignment along with penetrative direction of fuel cell bipolar plates may be used in fuel cell applications.
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Chang, Yao-ting, and 張耀庭. "Experimental Studies of the Effects of Flow Channel Structures and Inlets of Heterogeneous Composite Carbon Fiber Bipolar Plates on the PEMFC Performance." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/5tm3yz.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
95
The performance characteristics of pure hydrogen PEMFC (called HFC) stacks made with heterogeneous carbon fiber bipolar plates are studied in this thesis. In addition, the problem that the heterogeneous carbon fiber bipolar plate leaks in the high gas pressure is also solved in this studies so that the new plate can be used to the high current power sources. Because of the gas leakage of the first generation stack at high inlet gas pressure, the fuel supply is insufficient in the high current density. A 4-cell PEMFC stack made with this new bipolar plate is built with weight 370 g and volume 385 cm3 without a fan. The total power out of the 4-cell stack is about 30 W at room temperature. The specific power and volumetric power densities are 81 mW/g and 78 mW/cm3, respectively. The average power density is about 160 mW/cm2, but the power density of a single-cell can reach a value about 220 mW/cm2. The insufficient fuel supply cause that the power density of 4-cell PEMFC stack is lower than single cell, so it is necessary to solve the gas leakage at high pressure. Our experiment found that gas leakage occurs in heterogeneous bipolar plates can be relate to the insufficient or improper hot-pressing temperature, time and pressure while we are making the carbon fiber bunches. So the processes in making new carbon fiber bunches include water expansion, uniform glue adding, high hot-pressing pressure, and using proper temperature and enough solidification time. The airtight of the second generation of heterogeneous carbon fiber bipolar plates improves obviously with the new processes. No leakage occurs for gas pressure under 1atm. We expect that this design can be used to high inlet pressure. It is also quite suitable for various high-power electrical sources.
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Lo, Ming-Yuan, and 羅鳴遠. "Studies of a New-type Heterogeneous Composite Carbon Fiber Bipolar Plate Applied to a Portable Pure Hydrogen Proton Exchange Membrane Fuel Cell." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/54165153992423975090.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
93
A new type of heterogeneous carbon fiber bunch bipolar plate developed in our lab is applied to portable pure hydrogen proton exchange membrane fuel cell stacks. Several different types of bipolar plate structures have been designed, and the voltages and currents of these fuel cell stacks are measured to compare their performance. The new type of heterogeneous carbon fiber bunch bipolar plate is well in low contact resistance, weight low, small volume and the flexible geometry shape. Due to its flexible structure of carbon fiber bunch, the compressing pressure is small while assembling stack so that the electrode can not be over compressed and out of shape. Therefore the high porosity of diffusion layer can be keep and reaction gas can enter and distribute to all reaction areas easily. For using to portable equipments, a small 6-cell flat type of fuel cell stack are developed firstly. The total weight is about 75g and the total volume is about 68cm . The second stack is cylinder-type(I) fuel cell stack. The total weight is about 60g and the total volume is about 71cm . The third stack is cylinder-type (II). The total weight has been reduced to about 20g and the total volume has been reduced to about 30cm . Above three kinds of the 6-cell stacks the total electrode area is 13.5cm . Using Nafion, the catalyst content anode Pt 0.4mg/cm , cathode Pt 1.0mg/cm , On room temperature and inlet hydrogen gauge pressure 0.15atm air-breathing, total output power of the cylinder (II) can reach 1.85W, and the power density of unit area can reach about 137mW/cm^2.