Дисертації з теми "Pt layer"
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1
Shang, T., Q. F. Zhan, H. L. Yang, Z. H. Zuo, Y. L. Xie, L. P. Liu, S. L. Zhang, et al. "Effect of NiO inserted layer on spin-Hall magnetoresistance in Pt/NiO/YIG heterostructures." AMER INST PHYSICS, 2016. http://hdl.handle.net/10150/621346.
Повний текст джерелаАнотація:
We investigate spin-current transport with an antiferromagnetic insulator NiO thin layer by means of the spin-Hall magnetoresistance (SMR) over a wide range of temperature in Pt/NiO/Y3Fe5O12 (Pt/NiO/YIG) heterostructures. The SMR signal is comparable to that without the NiO layer as long as the temperature is near or above the blocking temperature of the NiO, indicating that the magnetic fluctuation of the insulating NiO is essential for transmitting the spin current from the Pt to YIG layer. On the other hand, the SMR signal becomes negligibly small at low temperature, and both conventional anisotropic magnetoresistance and the anomalous Hall resistance are extremely small at any temperature, implying that the insertion of the NiO has completely suppressed the Pt magnetization induced by the YIG magnetic proximity effect (MPE). The dual roles of the thin NiO layer are, to suppress the magnetic interaction or MPE between Pt and YIG, and to maintain efficient spin current transmission at high temperature. Published by AIP Publishing.
2
Shang, T., H. L. Yang, Q. F. Zhan, Z. H. Zuo, Y. L. Xie, L. P. Liu, S. L. Zhang, et al. "Effect of IrMn inserted layer on anomalous-Hall resistance and spin-Hall magnetoresistance in Pt/IrMn/YIG heterostructures." AMER INST PHYSICS, 2016. http://hdl.handle.net/10150/622466.
Повний текст джерелаАнотація:
We report an investigation of anomalous-Hall resistance (AHR) and spin-Hall magnetoresistance (SMR) in Pt/Ir20Mn80/Y3Fe5O12 (Pt/IrMn/YIG) heterostructures. The AHR of Pt/IrMn/YIG heterostructures with an antiferromagnetic inserted layer is dramatically enhanced as compared to that of the Pt/YIG bilayer. The temperature dependent AHR behavior is nontrivial, while the IrMn thickness dependent AHR displays a peak at an IrMn thickness of 3 nm. The observed SMR in the temperature range of 10-300 K indicates that the spin current generated in the Pt layer can penetrate the IrMn layer (<= 3 nm) to interact with the ferromagnetic YIG layer. The lack of conventional anisotropic magnetoresistance (AMR) implies that the insertion of the IrMn layer between Pt and YIG could efficiently suppress the magnetic proximity effect (MPE) on induced Pt moments by YIG. Published by AIP Publishing.
3
Thomas, Daniel. "Réalisation de transistors à un électron par encapsulation d’îlots nanométriques de platine dans une matrice diélectrique en utilisant un procédé ALD." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI131/document.
Повний текст джерелаАнотація:
L'introduction du transistor à un électron (SET) a secoué l'industrie des semi-conducteurs, avec des promesses d'efficacité inégalée. Cependant, le coût et la complexité associés à la réalisation d'un fonctionnement stable ont fortement entravé leur adoption. Après être tombé en dehors des grâces de l'industrie, la recherche universitaire a continué à pousser, démontrant des techniques novatrices pour la création de SET. Au cœur de ce problème de stabilité, il y a le besoin de construire de manière contrôlable des nanoislands de moins de 10 nm. Parmi les méthodes disponibles pour cette formation nanoisland, le dépôt de couche atomique (ALD) se distingue comme un processus hautement contrôlable industriellement. La deuxième barrière à l'entrée est la création d'électrodes nanogap, utilisées pour injecter du courant à travers ces nanoislands, pour lesquelles les chercheurs se sont largement appuyés sur des techniques de fabrication non évolutives comme la lithographie par faisceau d'électrons et le faisceau ionique focalisé. La technique d'évaporation de bord d'ombre surmonte les problèmes de complexité et d'échelle de la fabrication de nanogap, ouvrant de nouvelles possibilités. Dans ce travail, ALD sera démontré comme une superbe technique pour la culture de vastes réseaux 3D de nanoparticules de platine sous 2nm encapsulées dans Al2O3. ALD a fourni un moyen de faire croître ces matrices de nanoparticules en un seul processus, sous vide et à basse température. Grâce à l'évaporation du bord d'ombre, la lithographie UV a ensuite été utilisée pour former des électrodes nanogap avec des largeurs latérales élevées (100μm), avec des écarts démontrés au-dessous de 7 nm. La combinaison de ces techniques aboutit à un procédé de fabrication à haut rendement et à faible besoin pour la construction de SET complets. A partir des transistors résultants, de fines lamelles ont été préparées à l'aide de FIB et des modèles 3D ont été reconstruits par tomographie TEM pour analyse. La caractérisation électrique a été effectuée jusqu'à 77K, avec une modélisation révélant le transport de Poole-Frenkel en parallèle à un éventuel cotunneling. Des blocus de Coulomb stables, la signature des SET, ont été observés avec une périodicité régulière et étaient identifiables jusqu'à 170K. L'optimisation de ce processus pourrait produire des SETs de surface élevée capables de fonctionner de manière stable à température ambianteThe introduction of the single electron transistor (SET) shook the semiconductor industry, with promises of unrivaled efficiency. However, the cost and complexity associated with achieving stable operation have heavily hindered their adoption. Having fallen out of the graces of industry, academic research has continued to push, demonstrating novel techniques for SET creation. At the core of this stability issue is a need to controllably build nanoislands smaller than 10nm. Among the methods available for this nanoisland formation, atomic layer deposition (ALD) sets itself apart as an industrially scalable, highly controllable process. The second barrier to entry is the creation of nanogap electrodes, used to inject current through these nanoislands, for which researchers have leaned heavily on non-scalable fabrication techniques such as electron beam lithography and focused ion beam. The shadow edge evaporation technique overcomes the complexity and scaling issues of nanogap fabrication, opening new possibilities. In this work, ALD will be demonstrated as a superb technique for growing vast 3D arrays of sub 2nm platinum nanoparticles encapsulated in Al2O3. ALD provided a means of growing these nanoparticle matrices in a single process, under vacuum, and at low temperatures. Through shadow edge evaporation, UV lithography was then utilized to form nanogap electrodes with high lateral widths (100µm), with gaps demonstrated below 7nm. The combination of these techniques results in a high yield, low requirement fabrication process for building full SETs. From the resulting transistors, thin lamellas were prepared using FIB and 3D models were reconstructed via TEM tomography for analysis. Electrical characterization was performed down to 77K, with modeling revealing Poole-Frenkel transport alongside possible cotunneling. Stable Coulomb blockades, the signature of SETs, were observed with regular periodicity and were identifiable up to 170K. Optimization of this process could yield high surface area SETs capable of stable operation at room temperature
4
Marjunus, Roniyus [Verfasser], Walter [Akademischer Betreuer] Hansch, Walter [Gutachter] Hansch, and Ignaz [Gutachter] Eisele. "Development of Pt-based Sensitive Layer for Carbon Monoxide Work Function Change Based Sensor in Air at Room Temperature / Roniyus Marjunus ; Gutachter: Walter Hansch, Ignaz Eisele ; Akademischer Betreuer: Walter Hansch ; Universität der Bundeswehr München, Fakultät für Elektrotechnik und Informationstechnik." Neubiberg : Universitätsbibliothek der Universität der Bundeswehr München, 2018. http://d-nb.info/1175991708/34.
Повний текст джерела
5
Marjunus, Roniyus [Verfasser], Walter [Akademischer Betreuer] Hansch, Walter Gutachter] Hansch, and Ignaz [Gutachter] [Eisele. "Development of Pt-based Sensitive Layer for Carbon Monoxide Work Function Change Based Sensor in Air at Room Temperature / Roniyus Marjunus ; Gutachter: Walter Hansch, Ignaz Eisele ; Akademischer Betreuer: Walter Hansch ; Universität der Bundeswehr München, Fakultät für Elektrotechnik und Informationstechnik." Neubiberg : Universitätsbibliothek der Universität der Bundeswehr München, 2018. http://d-nb.info/1175991708/34.
Повний текст джерела
6
Rouhet, Marlene. "Etude de l'influence des protons sur la réduction de l'oxygène dans des couches catalytiques ordonnées en vue d'une application en pile à combustible." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF031/document.
Повний текст джерелаАнотація:
Les couches catalytiques avec une structure ordonnée à base de nanoparticules de Pt supportées sur des nanofilaments de carbone verticalement alignés ont montré des performances intéressantes grâce à l’amélioration des propriétés du transport de matière et à une meilleure utilisation du Pt. Des études électrochimiques combinées à une modélisation mathématique ont mis en évidence l’influence du transport de protons sur les processus d’oxydo-réduction, la cinétique et le mécanisme de réduction de l’O2 (ORR), et sur H2O2 qui s’échappe des couches pendant l’ORR. Nous avons montré que (i) les protons sont impliqués dans l’étape limitante de la réaction, (ii) pour un pH ≥ 3, un plateau de courant limité par la diffusion des protons est observé et, (iii) pour un pH ≥ 3, le mécanisme de l’ORR implique non seulement les ions hydroniums mais aussi les molécules d’eau. L’intégration de ces couches catalytiques dans des PEMFCs haute température a ensuite été étudiée. Les performances obtenues sont légèrement plus basses que celles des couches conventionnelles. Un travail d’optimisation reste donc à accomplir pour améliorer les performancesOrdered catalytic layers based on vertically aligned carbon nanofilaments with Pt nanoparticles demonstrate high efficiency for oxygen transport and Pt utilization in the catalytic layer. Electrochemical studies combined with mathematical modeling confirm the influence of the proton transport on surface red-ox processes, the kinetics and the mechanism of the O2 reduction (ORR), and on the H2O2 escape. We show that (i) protons are involved in the rate-determining step of the O2 reduction, (ii) for pH ≥ 3, a plateau corresponding to the diffusion-limited current of protons is observed and, (iii) for pH ≥ 3, the mechanism of the ORR involves not only the hydronium ions but also water molecules. The integration of these catalytic layers in high temperature PEMFCs was then studied. The performance is slightly lower than that for conventional layers. An optimization work is required to improve the performance
7
Zhu, Qing Shih Wei-Heng Shih Wan Y. "Characterization and application of piezoelectric microcantilever sensors fabricated from substrate-free PMN-PT layers /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2967.
Повний текст джерела
8
Falch, Anzel. "Synthesis, characterisation and potential employment of Pt–modified TiO2 photocatalysts towards laser induced H2 production / Falch A." Thesis, North-West University, 2011. http://hdl.handle.net/10394/7346.
Повний текст джерелаАнотація:
The photocatalytic production of H2 from water as well as from a 1:1 methanol:water
solution employing pre–treated TiO2 and various Pt–TiO2 photocatalysts was studied by
using an Nd:YAG laser as irradiation source. The photocatalysts (0.5–, 1–, 1.5– and 2
wt% Pt–TiO2) were prepared by utilizing a photocatalytic reduction method after which
characterisation by various analytical techniques, i.e. XRD, TEM, ICP, SEM, and EDX,
were conducted. XRD clearly indicated that platinum was not present in the crystal
structure of TiO2, but was rather loaded onto the surface of TiO2. TEM analysis
confirmed the presence of Pt on the surface with a particle/cluster size between 11 nm
and 22 nm. SEM showed that repeatable results in respect of surface appearance were
obtained. ICP and EDX indicated that the loading method was successful with only a
slight deviation between the actual amount loaded and the calculated amount loaded.
The impact of the loaded Pt on the band gaps of the different photocatalysts was
investigated by diffuse reflectance spectroscopy (DRS) and calculated by employing
the Kubelka–Munk method. The band gap values shifted sequentially from 3.236eV to
3.100 eV as the loading increased, moving closer to the absorbance region for visible
light. The amount of hydrogen produced from the individual photocatalysts dispersed in
both pure water and aqueous methanol solutions, was measured manually with a gas
chromatograph. As soon as irradiation was initiated, a distinct colour change from
shades of grey to dark blue–grey was observed for all the photocatalysts. XRD
confirmed that it was due to the anatase phase transforming to produce more rutile
phase. No H2 was detected for the various photocatalysts suspended in water, i.e. in
the absence of methanol. The amount of hydrogen produced from the various Pt
photocatalysts suspended in the aqueous methanol solution was found to be the
highest for the 0.5wt%– and 1.5wt% Pt–TiO2 photocatalysts and the lowest for the 2wt%
Pt–TiO2. This could be due to loading Pt above the optimum amount to such an extent,
preventing sufficient light from reaching the TiO2 surface. Pt particles can also touch
and overlap which will decrease Pt contact with TiO2 thus decreasing effective charge
transfer.Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.
9
Mano, Micaela. "POLÍTICAS PÚBLICAS EM TEMPOS DO GOVERNO PT: UMA ANÁLISE SOBRE O PELC." Universidade Federal de Santa Maria, 2016. http://repositorio.ufsm.br/handle/1/6741.
Повний текст джерелаАнотація:
Este estudio se dedica al análisis de Programa de deporte e Ocio de la Ciudad Pueblos y Comunidades Tradicionales Universidad Federal de Santa Maria. Tiene por objetivo analizar el papel del PELC/PCT/UFSM en el conjunto de las políticas públicas de deporte y ocio del gobierno PT. Para alcanzar este objetivo usaremos como base teórica el Materialismo Histórico Dialéctico. Se trata de una pesquisa organizada a partir de la revisión bibliográfica y del análisis documental, en el cual fueron usados documentos oriundos de los documentos finales de las Conferencias Nacionales de Deporte y la Política Nacional de Deporte, directrices y relatorías del PELC. La elección de realizar este estudio a partir del gobierno del PT, gestión Lula (2003-0211), se debe al PELC haber sido creado en 2003, por estarnos en una década significativa de Mega eventos que tuvo su inicio en la gestión del ex presidente Lula, y por el hecho del PT haber representado una opción de enfrentamiento a la lógica neoliberal. El estudio evidenciara que eso no aconteció, de hecho el gobierno Lula y Dilma adhirieron al proyecto neoliberal, materializándose en los paquetes de austeridad con reformas estatales, precarización de la leyes de trabajo, retirada de los derechos sociales, repase de recursos públicos a entidades privadas, defensa de exención fiscal, políticas de convenios. Por intermedio del análisis del neoliberalismo y su implantación en las áreas económicas, políticas y sociales, podemos constatar que en las políticas públicas de deporte y ocio la ideología se reproduce. El PELC/PCT/UFSM al tiempo que es desfavorecido presupuestariamente para aumentar la inversión en el área del deporte de alto rendimiento y los Mega eventos, nos trae un panorama de profundización de las relaciones de precarización, privatización mediante convenios públicos privados y delegación de responsabilidades para la sociedad civil, eximiendo de responsabilidad al Estado del deber de garantizarlas.Dedica-se, neste estudo, à análise do Programa de esporte e Lazer da Cidade Povos e Comunidades Tradicionais Universidade Federal de Santa Maria. Temos por objetivo analisar o papel do programa PELC/PCT/UFSM no conjunto das políticas públicas de esporte e lazer do governo PT. Para atingirmos este objetivo usaremos como base teórica o Materialismo Histórico Dialético. Trata-se de uma pesquisa organizada a partir de revisão bibliográfica e a análise documental, na qual foram utilizados documentos oriundos dos documentos finais das Conferências Nacionais do Esporte e a Política Nacional de Esporte, diretrizes e relatórios do PELC. A escolha de realizar este estudo a partir do governo do Partido dos Trabalhadores, gestão Lula (2003-2011), se deve ao PELC ter sido lançado em 2003, por estarmos numa década significativa de Megaeventos, que teve início na gestão do ex-presidente Lula, e pelo PT ter representado uma opção de enfrentamento à lógica neoliberal. O estudo mostrara que isso não aconteceu, de fato o governo Lula e Dilma aderiram ao projeto neoliberal, materializando-se nos pacotes de austeridade com reformas estatais, precarização das leis trabalhistas, retirada dos direitos sociais, repasse de recursos públicos a entidades privadas, defesa de isenção fiscal, políticas de parcerias. Por intermédio da análise do neoliberalismo e sua implementação nas áreas econômicas, políticas e sócias, podemos constatar que nas políticas públicas de esporte e lazer a ideologia se reproduz. O PELC/PCT/UFSM, ao tempo que é desfavorecido orçamentariamente para aumentar o investimento na área de esporte de alto rendimento e para os Megaeventos, nos traz um panorama de aprofundamento das relações de precarização, privatização mediante parcerias público privadas e delegação de responsabilidades para a sociedade civil desresponsabilizando o Estado do dever de garanti-los.
10
Lišková, Zuzana. "Aplikace SPM při studiu a modifikaci ultratenkých vrstev Pt, Co a graphenu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228669.
Повний текст джерелаАнотація:
This diploma thesis deals with the preparation of the very thin films and their investigation by scanning probe microscopy methods. The ultrathin films of Pt on Pt(111) were created by pulsed laser deposition and the ultrathin films of Co on Pt(111) were deposited by thermal evaporation. The coverage of the substrate was much smaller than one monolayer (in order of hundredths of monolayer). The nucleation theory was verified by these experiments using so-called Onset method. Further graphene sheets were prepared on layer of Si/SiO2 by the mechanical exfoliation from the graphite crystal. The fabricated graphene sheets were studied by micro-Raman spectroscopy, microreflectometry, atomic force microscopy and similar techniques. These methods proved the thinnest graphite layers were consisted of two graphene monolayers.
11
Gazdzicki, Pawel [Verfasser], and Peter [Akademischer Betreuer] Jakob. "Adsorption and Thermally Induced Reactions of Methanol on Bimetallic X/Ru(0001) Layers (X = Cu, Pt) / Pawel Gazdzicki. Betreuer: Peter Jakob." Marburg : Philipps-Universität Marburg, 2012. http://d-nb.info/1019850965/34.
Повний текст джерела
12
Fischer, Mathias [Verfasser]. "Characterization of doping atoms (Ta, Nb) in advanced PEM fuel cell supports and catalysts as well as of the surface-solvent interaction of laser-generated Pt nanoparticles : A XAFS study / Mathias Fischer." Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/112454030X/34.
Повний текст джерела
13
French, Kyle J. "Growth of Optical Quality Lead Magnesium Niobate-Lead Titanate Thick Films." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1575993750125728.
Повний текст джерела
14
Graf, Ruth Maria. "Estudo comparativo da cicatrizacao de retalho cutaneo dorsal em ratos com e sem a aplicacao do laser de Erbium : YAG /." reponame:Repositório Institucional da UFPR, 2001. http://200.17.209.5:8000/cgi-bin/gw_42_13/chameleon.42.13a?host=localhost%201111%20DEFAULT&search=KEYWORD&function=CARDSCR&SourceScreen=INITREQ&sessionid=2006092100245000953&skin=ufpr&conf=.%2fchameleon.conf&itemu1=1003&u1=1003&t1=Ruth&op1=AND&u2=1003&t2=Graf&lng=pt&pos=5&prevpos=1&.
Повний текст джерела
15
Hsu, Bao-Yin, and 許寶璌. "Preparation of dual-layer structured cathode catalyst layer with electrospun Pt nanowires and Pt/C on the performance of PEMFC." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/09437379542657313076.
Повний текст джерелаАнотація:
碩士大同大學
機械工程學系(所)
101
In the study, we have considered the effect of dual-layer structured cathode catalyst layer with electrospun Pt nanowires and Pt/C ,determined the optimal dual-layer structured catalyst layer design parameters including Pt nanowires and Pt/C loading, Nafion content by measuring the variations of cell performance. The experiments have been used polarization curve, electrochemical impedance spectroscopy, cyclic voltammetry, exchange current density . The experiment results indicated the dual-layer structured cathode catalyst layer structure can effectively improve the fuel cell performance . The dual-layer structured with inner layer of Pt/C (Near the proton exchange membrane side)and outer layer of Pt nanowires (Near the gas diffusion layer side)could enhance the performance effectively, and the parameters discussed in when loading ration of 0.4 mg cm-2 Pt/C and 0.1 mg cm-2 Pt nanowires that the performance is fine. The cell have the best performance with inner layer is 30% and outer layer is 20%.
16
Lin, Yu-Ting, and 林於亭. "Improvement of PEMFC Performance by Adding Pt/TiO2 in the Pt/C Catalyst Layer." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/04249601185451929910.
Повний текст джерелаАнотація:
碩士國立中興大學
材料科學與工程學系
96
Recently, along with the considerable increasing in the price of petroleum and the more emphasis on the environmental preservation, many efforts have embarked on the discovery and development of new fuel resources. Proton exchange membrane fuel cells (PEMFC) have been regarded as a candidate for future power sources for transport, residential and portable applications, primarily due to the advantageous characteristics of high power density, high energy-conversion, simplicity of operation and near-zero pollutant emission. High surface area carbon carriers, such as carbon black and carbon nanotube, were widely used in PEMFC in order to advance the utility of the Pt catalyst and decline the prime cost, however, this method still left much to be desired. Titania particles with high redox facility by irradiating the ultraviolet, which is caused by the jumping of electrons from valence band to conduction band to produce electron-hole pairs. In this study, the Pt/TiO2 and Pt/C catalysts were synthesized by thermal reflux method. The composition and the area of active sites of the catalyst, the particle size of Pt and the effect caused by the different adding sequence of Pt precursor were investigate by X-ray diffraction instrument （XRD）, Field emission scanning electron microscope （FESEM）, Transmission electron microscopy （TEM） and chemical analyzer, individually. The cell performance with different addition of Pt/TiO2 (0 wt. %, 5 wt. % and 10 wt. %) into Pt/C catalyst were measured by the fuel cell testing system. As the result, the Pt/C catalyst synthesized by the previous dispersion of carbon black showed the higher active area (21.05 cm2) and more uniform Pt particle size (5.4 nm). Specifically, form the results evidences, the catalyzed characteristic also can be induced by the bias of 0.7 V. In the single cell test, the results proved that the addition of Pt/TiO2 into anode catalyst layer can actually enhanced the adsorption of water and promoted the back diffusion reaction simultaneously, and the 5 wt. % Pt/TiO2-doped anode catalyst layer showed the best performance. By contrast, the addition of Pt/TiO2 catalyst in the cathode catalyst layer represents no benefits for facilitating the cell performance. The Pt/TiO2 catalyst was added to anode and cathode catalyst layer, the addition of 5 wt. % Pt/TiO2 showed the best current density.
17
Chang, Chih-Kuo, and 張智國. "The Observation of Hydrocarbon Reaction Layer on Pt Surface." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/13407046668575363090.
Повний текст джерелаАнотація:
碩士國立成功大學
航空太空工程學系
88
This thesis was to study the surface reactions of heterogeneous catalyst by applying laser-induced-predissociation-fluorescence (LIPF) spectroscopy. The study was to establish the fundamental of catalytic surface reactions by observing OH radical near the surface of Pt plate. Channel flow of a hydrogen-air mixture (ψ=0.4) was parallelly in contact with the preheated Pt plate (700K and 800K) at velocities of 5cm/sec and 10cm/sec. Near surface OH radicals diffused from Pt plate were monitored by observing the fluorescence of the laser (KrF, Excimer) excited OH (A←X, (3,0), P28, ~248.384 nm in air). A gatable Intensified Charged Couple Device (ICCD) camera couple with a spectrometer was used to collect the OH (3,2) band fluorescence. OH spectra showed that the fluorescence of OH (3,2) band P28 transition was interfered by O2 fluorescence. As a result, only the fluorescence of R26 and Q27 transitions was used to characterize the OH concentration. After solid angle calibration by N2-Raman, OH fluorescence intensity increased along the leading edge of Pt plate and reached a maximum at 4 mm downstream. To compare the physical properties of H2 with those of O2, since the diffusive velocity and adsorption rate of H2 were higher at the experimental condition, the surface reactions were limited by O2-diffusion. The analysis was supported by the results of temperature measurements, which showed that the maximum heat release was appeared near leading edge and approached partial equivalence downstream. After 4 mm downstream, the effect of catalytic reactions was not pronounced.
18
Chen, Chuen-Rung, and 陳春榮. "Composite Membrane Containing Pt-Ru Catalyst as Electrode for DMFC by Layer-By-Layer Techique." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/25088702787130444131.
Повний текст джерелаАнотація:
碩士明道大學
光電暨能源工程學系碩士班
103
Abstract The performance and utilization of catalyst of direct methane fuel cell (DMFC) remains at a low level. Therefore, this research study the membrane electrode assembly formed by the self-assembly of polyallylamine hydrochloride (PAH) and polystyrene sulfonic acid sodium salt (PSS) containing the Pt-Ru catalyst to improve the reaction surface area and the output performance. The nanometer-sized catalyst layer formed by the PAH/PSS bi-layers is believed to improve the reaction surface area and the multi-layers structure is expected to extend the reaction area to three dimension, and thus enhances the overall reaction rate even with the low Pt-Ru catalyst loading (<0.1 mg cm-2) on both anode and cathode side. In addition, this design might oxidize the penetrating methanol while reducing cathode mixed potential effect. This will reduce the degree of cathode polarization, and thus enhancing the power density.Several methods and instruments are used for characterization of the obtained samples such as ultraviolet-visible spectroscopy (UV-Vis), AC impedance, cyclic voltammetry (CV), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Result shown that, samples with 10 layers containing 40%Pt50Ru50/C and 60%Pt50Ru50/C of PAH/PSS, thickness are 1.15um and 1.19um, the loading were 0.06 mg cm-2 and 0.08mg cm-2, have a great performance of PEMFC. The maximum output are 60.02mW cm-2 and 71.22mW cm-2 @(0.4V). However, a sample of 10 layers without adding any Pt50Ru50/C, the maximum output is 40.17mW cm-2 (@0.4V). This is because of the adding of 40Pt50Ru50/C or 60%Pt50Ru50/C catalyst in to solution of PAH, effectively the PAH/PSS self-assembled monolayers catalyst generated electron and proton transfer to an external circuit, respectively, with the proton exchange membrane and enhance the overall catalyst loadings. Therefore, to enhance the potential of the battery are respectively 39.5% and 49.7%, the power density are 49.4% and 77.3% (@0.4V). And due to this origin, samples of 10 layers containing 40%Pt50Ru50/C at PAH and 60%Pt50Ru50/C at PAH, the maximum output power of Direct Methanol Fuel Cell (DMFC) are 3.65 mW cm-2 and 4.08 mW cm-2 (@0.15V). The utilization rates of catalyst for the sample 10 layers : PAH/PSS- 40% Pt50Ru50/C at PEMFC and direct methanol fuel cell (DMFC) are 1285A g-1 Pt (@0.6V) and 385A g-1 Pt-Ru(@0.15V), while , the sample 10 layers : PAH/PSS- 60% Pt50Ru50/C at PEMFC and direct methanol fuel cell (DMFC) are 1106A g-1 Pt(@0.6V) and 335A g-1 Pt-Ru(@0.15V). Compared to the utilization rates for general process of catalyst are 2000A g-1 Pt (@0.6V) and 88A g-1 Pt-Ru(@0.15V), this new process method obtained a relatively high catalyst utilization. Keywords: membrane electrode assembly, nanometer-sized catalyst layer, self-assembly layer, multi-layers structure, DMFC.
19
Kuo, Chih-Yun, and 郭芷昀. "Atomic layer deposition of Pt catalysts on one dimensional InN nanostructures." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/26636397062512083982.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
化學工程系
96
One-dimensional InN nanostructures with large surface area and high conductivity were used as templates for the deposition Pt catalyst by using atomic layer deposition (ALD) method. The chemical composition, morphology and electrochemical characteristics which were applicable for the anode electrode for direct methanol fuel cell (DMFC) were also investigated. First, the growth mechanism in a ALD system using CpPtMe3 as the precursor was investigated. The growth could be separeted into three regions：(1) Ts < 2500C, a part of precursor was decomposed to form dimethyl platinum which causes steric hindrance on the substrate surface. (2) 2500C < Ts < 3000C：precursor was decomposed to form methyl platinum and matched self-limiting mechanism. (3) Ts > 3500C：precursor was decomposed to form platinum atom and multilayer-adsorption occurred on the surface. Then, a typical ALD Pt deposition condition that applied 5.71×10-4 torr Pt precursor for 3 seconds exposure and [O2] = 28.6% for 2 seconds exposure at 3000C was used for Pt deposition on InN nanostructures. TEM results showed that the deposition of Pt catalyst on InN was polycrystalline and the average diameter of Pt cluster was about 9-11 nm. Decreasing the growth temperature to 2800C showed a better Pt coverage result of slightly (111) oriented on InN nanostructures. A cyclic voltammetry measurement with respect to methanol showed quite a small onset potential at 0.34V, coincident with the value (0.35V) for single crystalline Pt(111).
20
Huang, Chung-Han, and 黃崇涵. "Fabrication and characterization of PZT thin film on Pt/Ti layer." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/34413551287343639041.
Повний текст джерелаАнотація:
碩士國立臺灣海洋大學
電機工程學系
92
ABSRTRACT The main object of this thesis concentrates on the research of PZT thin film properties based on the Pt/Ti electrode. Pt, Ti and PZT are all prepared by the radio frequency magnetron sputter system. During suitable annealing process, PZT exhibited the highly (110) oriented perovskite structure. The crystalline of Ti film, Pt film and PZT film are analyzed by the XRD, the surface morphology and cross-section are analyzed by the SEM, and element composition was observed by EDS. In this experiment, using different deposition time, annealing temperature and annealing duration to prepare the Ti and Pt thin film. Prepare the Pt or Ti film on the silicon substrate; a chemical reaction is easily to produce after annealing process. If the PZT chemical composition of Si deposition on PZT thin film is increases the properties of piezoelectric is worse. When PZT on the Pt/Ti layer that the silicon doping can be reduced. The reduced Si doping PZT thin film will have better properties if we adjust the annealing parameters about Pt/Ti layer.
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Tzou, Dong-Ying, and 鄒東穎. "Synthesis of Pt Nanoparticles by Atomic Layer Deposition for Electrochemical Catalysis." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/76564166176875493445.
Повний текст джерелаАнотація:
博士元智大學
化學工程與材料科學學系
105
Part I This study adopts a modified atomic layer deposition (ALD) process to prepare size-controlled Platinum (Pt) nanoparticles over the surface of carbon black, showing superior catalytic activity toward ethanol oxidation. Two types of ALD precursors, (methylcyclopentadienyl) trimethyl platinum (MeCpPtMe3) and oxygen (O2), were used to grow Pt deposits at 250°C. For 30 ALD cycles, the pulse period of MeCpPtMe3 serves as a key factor in controlling the particle size and the weight loading of Pt deposits. The Pt growth rates over the carbon support can be attributed to the surface coverage of Pt-O* sites, diffusion rate of MeCpPtMe3, and lateral interaction between each active site. Since the MeCpPtMe3 dose strongly affects the Pt particle size and the deposit density, the growth of ALD-Pt can be taken into account as diffusion-limiting. Due to its surface-catalyzed reaction steps, the small-sized ALD-Pt catalysts offer better catalytic activity, CO tolerance, and long-term stability as compared with the large-sized ones. On the basis of the results, the modified ALD technique exhibits a great potential for tuning the Pt particle size and weight loading onto the carbon support for fuel cell application. Part II The present work adopts an ALD technique to synthesize highly-crystalline Pt nanoparticles onto carbon powders, offering superior catalytic activity toward methanol oxidation within the temperature range of 25-55°C. Uniformly-dispersed Pt nanoparticles with an ultralow loading are coated over the carbon supports, served as catalyst materials for methanol electro-oxidation. Experimental results reveal that ALD-Pt catalyst offers not only an improved catalytic activity toward methanol oxidation but also superior CO tolerance, as compared to commercial Pt one. The decreased current ratio for direct to indirect pathway with an increase in temperature is found, referring to the kinetic limitations for the formation and oxidation of Pt-(CO)ads sites at high temperatures. Followed up Arrhenius-type behavior, small apparent activation energies (i.e., ca. 30.3 and 41.7 kJ mol-1) of ALD-Pt catalyst can be achieved for dehydrogenation of methanol (direct pathway) and oxidation of adsorbed CO species (indirect pathway) in methanol oxidation reaction. The low potential barrier on ALD-Pt catalyst is attributed to small particle size (i.e., average particle size of 2.1 nm) and oxidized Pt surface (i.e., native Pt-O* active sites) that efficiently enhance the catalytic activity and CO tolerance, respectively. As a result, this study examines the influence of temperature on catalytic activity and anti-poisoning performance on the ALD-Pt catalyst, in which the surface chemistry and structural motif is more efficient at electrochemically oxidizing methanol and improving the CO tolerance.
22
Sung, Ming-Tung, and 宋明棟. "Preparation of cathode catalyst layer with composite of electrospun Pt nanofibers and Pt/C on the performance of a PEMFC." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/58835412099709605504.
Повний текст джерелаАнотація:
碩士大同大學
機械工程學系(所)
101
In this study, the electrospinning method was used to fabricate the catalyst layer for a proton exchange membrane fuel cell (PEMFC). The corresponding membrane electrode assembly (MEA) was also made by hot press and the fuel cell performance has been tested. The electrospun nanofibers were produced by electrospun solution made of PVP polymer mixed with Pt precursor (H2PtCl6) to be catalyst layers. Besides, the cathode catalyst layer was fabricated by different mixing ratio of Pt/C and Pt nanofibers and the performance was tested. The Pt nanofibers are sprayed on carbon cloth and then hot-pressed together with Nafion 117 membrane to form the MEA. The different Pt loading with composite of Pt/C and Pt nanofibers and Nafion contents were mixed to produce cathode catalyst layer. Then, analyzing the best parameters of catalyst layer and performance of fuel cell. The results indicated that cathode catalyst layers fabricated only by Pt nanofibers couldn’t enhance the performance of fuel cell, but the traditional Pt/C mixed with fitting ratio of Pt nanofibers could enhance the performance effectively. Results showed that the performance is fine, when loading ratio of Pt is 1:4 in the mixture of Pt nanofibers and Pt/C. Then finding out the best Nafion content with the mixing ratio of Pt, the fuel cell have the best performance with 30% content of Nafion.
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Vanbruinessen, Andrea. "Development of Pt/CNT Catalyst and Transport-Kinetic Characterization of PEMFC Catalyst Layer." Thesis, 2009. http://hdl.handle.net/1974/1664.
Повний текст джерелаАнотація:
The electrochemical performance of a polymer electrolyte membrane fuel cell is known to be dominated by the cathode processes comprising the various reaction and transport steps in the overall oxygen electro-reduction to water occurring in the catalyst layer (CL). This thesis is concerned with one such transport process – oxygen transport in ionomer phase of the CL – and the synthesis/characterization of platinum catalyst on an alternative support – carbon nanotubes (CNT). Specifically, the objectives of the thesis are: (i) exploration of methods for determining the effective permeability of oxygen in the ionomer phase of the carbon-ionomer composite representing the PEMFC catalyst layer (ii) synthesis of Pt/CNT catalysts and characterization thereof.
An electrochemical method for determination of oxygen permeability in Nafion and Nafion-carbon composite films was explored. Since the method is suitable for dense films, mathematical model for data analysis had to be modified to allow treatment of porous films. Applying the modified model to the porous Nafion film, the oxygen permeation in the Nafion phase was found to agree with the literature data for oxygen permeation in Nafion membranes. However, no relationship between the effective permeability and ionomer content was found.
Two methods for synthesis of Pt/CNT catalysts were studied – the precipitation method and the colloidal/ethylene glycol method. Functionalization of CNTs was found to be critical to obtaining any significant amount of Pt deposition on CNT. The precipitation method did not yield reproducible results. Pt/CNT catalysts of desired properties were synthesized via the colloidal/EG method. It was found that a high pH of 8.5 to 10.5 resulted in smallest Pt particle size. The Pt particles size was determined to range 2-4 nm. The synthesized Pt/CNT catalysts were also tested in a fuel cell environment. Steady-state polarization curves in humidified H2/Air system were obtained that demonstrated performance comparable to commercial electrodes in that cell potential of greater than 0.6 V at current density of 800 mA/cm2 electrode area and a limiting current density of 1200 mA/cm2 electrode area were observed.Thesis (Master, Chemical Engineering) -- Queen's University, 2009-01-13 14:46:53.853
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Chung, Chih-Yeh, and 鍾志業. "Study of Proton Exchange Membrane Fuel Cell with Sputter-Deposited Pt Catalyst Layer." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/22558487799214921759.
Повний текст джерелаАнотація:
碩士逢甲大學
材料科學所
92
Sputter deposition has been investigated as a tool for manufacturing proton exchange membrane fuel cell electrodes with improved performance and catalyst utilization vs. ink-based electrodes. The effects of substrate, Pt catalyst loading, vacuum degree and in-situ annealing treatment on the performance of PEMFC Pt film electrode made by magnetron sputtering has been studied in this project. The anode made by sputtering Pt on carbon cloth performs as well as E-TEK electrode (232 vs. 240 mA/cm2 at 0.6 V, 0.4 mg Pt/cm2), but the anode made by sputtering Pt directly on N117 shows no any power output as Pt loading is 0.4 mg Pt/cm2. The performance of Pt film electrode used as PEMFC anode doesn’t absolutely promote with increasing Pt loading, although the Pt film electrode with 0.4 mg Pt/cm2 shows the best performance, the Pt film electrode with 0.1 mg Pt/cm2 shows a better Pt catalyst utilization (1500 A/cm2-g at 0.6 V). In all samples, the Pt film anode made by sputtering process at a background vacuum of 1.0 x 10-2 torr provides the highest electric power (306 mA/cm2 at 0.6 V, 0.4 mg Pt/cm2), the performance is 25% higher than that of E-TEK electrode. The Pt film electrode with low resistance made by magnetron sputtering is only suitable for PEMFC anode. In-situ annealing treatment to substrates in sputtering process promotes the power output of the Pt film electrode used as PEMFC cathode over 100%, but comparing with E-TEK electrodes, there is still a big gap (68 vs. 240 mA/cm2 at 0.6 V, 0.4 mg Pt/cm2).
25
Huang, Chien-Hao, and 黃建豪. "The Preparation of Pt-Catalyst Layer for Fuel Cells by Using the Electrospinning." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/88584916144543550431.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
化學工程系
99
The electrospun Pt nanofibers are prepared by the electrospinning of PVP-Pt solution, and then the PVP is removed by calcination in the air. The PVP concentration, solvent composition, Pt concentration, flow rate, applied voltage and discharging distance in the electrospinning are all optimized in this study. After that, the calcinations temperature and period are also investigated. To analyze the structure and properties of metallic nanofibers, SEM, TEM and EDS were applied to obtain the morphologyof nanofibers and the distribution of Pt in fibers. The Pt-fibrous layer are homogenized by several methods, including decrease of heating rate，coating of middle layer，surface modification for carbon support and cross-linking process. The results indicated that the Pt nanofibers fabricated in this research are highly alloyed. With the optimized conditions in the electrospinning process, the diameters of nanofibers were smaller than 40 nm and with homogeneous distribution of Pt. The results also show a higher electrical conductivity of Pt nanofibers, compared with those of the conventional Pt nanoparticle catalysts. By using the pre-crosslinking with GA vapor and the post-crosslinking with concentrated GA solution, the shrinkage caused by calcinatiion can be avoided. Thus, a homogeneous catalyst layer composed of Pt electrospun fibers is successfully prepared in this study. The adhesion between carbon paper and Pt-fibrous catalyst layer is good in a large area. The enhancements of electrocatalytic properties for the Pt nanofibers could outperform on the electro-oxidations over the fuel cell electrodes.
26
Hung, Yi-Hsuan, and 洪翊軒. "PREPARATION AND CHARACTERIZATION OF Pt/CNT AS CATHODIC CATALYST LAYER IN A PEMFC." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/66201659042159811402.
Повний текст джерелаАнотація:
碩士大同大學
機械工程學系(所)
100
This study prepared and charactered of Pt/CNT as cathodic catalyst layer in a PEM fuel cell. The experiment focused on the cathodic catalyst layer, were investigated three parameters of the vector species, Platinum loading and nafion solution content. The polarization curves, electrochemical impedance spectroscopy, cyclic voltammetry, thermal gravimetric analysis and X-ray diffractometer analysis were measured by fuel cell testing machine. The results show that acidification carbon nanotubes as a carrier has the best performance, and reducing the Platinum loading causes the fuel cell performance degradation. Platinum loading and Nafion solution content are related to each other. When reducing the platinum load and increasing the content of Nafion solution, the fuel cell performance can be improved and achieve the goal of reducing the use of Platinum. The research results can help catalyst layer technology improvement and enhance the PEM fuel cell performance.
27
Tseng, Po-Kai, and 曾柏凱. "Preparation of Pt3Ni(Pt-skin) thin layer modified Pd/C oxygen reaction electrocatalysts." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2np3vc.
Повний текст джерелаАнотація:
碩士國立中興大學
化學系所
106
Bimetallic Pt-Ni with Pt on the outermost layer and an innermost layer enriched in Ni, referred to as (Pt3Ni(Pt-skin), is a promising configuration of electrocatalyst for the oxygen reduction reaction (ORR) in fuel cells. We prepare a core (Pd)/shell (Pt3Ni(Pt-skin)) catalyst (Pt3Ni(Pt-skin)/Pd/C) from Zn underpotential deposition (UPD) on a Ni UPD modified Pd/C catalyst, facilitating Pt atomic layer-by-layer growth on the Ni surface through the galvanic replacement process. The Pt3Ni(Pt-skin)/Pd/C shows the best ORR performance, with a Pt specific activity 16.7 mA cm-2 and Pt mass activity 14.2 A mgPt-1, which are 90- and 156- fold improvements over commercial Pt/C catalysts. The Pt3Ni(Pt-skin) structure effectively inhibits Ni leaching to improve the durability under the two accelerated durability test modes mimicking the catalyst lifetime and start-up/shut-down cycles.
28
Tai, Chun-Yen, and 戴均晏. "Electrooxidation of methanol catalyzed by Pt nanoparticles deposited by Plasma-Enhanced Atomic Layer Deposition." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/12317559028258989016.
Повний текст джерелаАнотація:
碩士國立交通大學
材料科學與工程學系所
102
For the application of direct methanol fuel cells (DMFC), it is desirable that the anode has a high electrocatalytic activity toward methanol oxidation reaction (MOR) with a minimized Pt catalyst loading and a high resistance against the CO poisoning effect. Titania supports for Pt catalyst loading are found to significantly enhance the electrocatalytic activity and the CO-tolerance of the anode. In the study, we used plasma enhanced atomic layer chemical vapor deposition (PEALD) to prepared Pt nanoparticles on TiO2 substrates and investigated the size effect of Pt nanoparticles on the improvement of the electrocatalytic activity toward MOR. The deposition of Pt nanoparticles on the TiO2 substrate by PEALD was performed at a substrate temperature of 2000C using (trimethyl)methylcyclopentadienylplatinum (MeCpPtMe3) as the Pt precursor. Material properties of the Pt nanoparticles were studied by secondary electron microscopy, x-ray photoelectron spectroscopy and transmission electron spectroscopy. The density and size of the PEALD Pt nanoparticles increases with the number of the PEALD reaction cycle, and the particle size was in the range of 2-5 nm. The electrochemical analysis showed that the electroactivity of the Pt/TiO2 anode toward MOR in acidic media depends on the PEALD cycle number. The anode prepared with a small PEALD cycle number exhibits a low electrochemical activity; this is because discrete Pt nanoparticles provide little electrical conductivity for the electrically insulating TiO2 support. However, the If/Ib ratio, which is defined by the ratio of the MOR peak in the forward scan to the CO-adspecies oxidation peak in the reverse scan in the cyclic voltammogram, reveals a good CO tolerance for the electrode. The CO tolerance of the electrode becomes lower when the PEALD cycle number is large (>30 cycles). The electrode with Pt nanoparticles deposited with a PECVD cycle number of 20-30 exhibits the best electrocatalytic performance, both in the electroactivity and in the CO tolerance. The excellent electrocatalytic performance of the Pt/TiO2 electrode is ascribed to the synergistic effect of the electronic effect and the bifunctional mechanism. Charge transfer (electronic effect) between Pt nanoparticles and the TiO2 support may weaken the bonding strength of CO on the Pt nanoparticles, facilitating the oxidation of CO adspecies. Moreover, the TiO2 support can improve the CO tolerance via the bifunctional mechanism effect because it dehydrogenates water forming adsorbed OH at a lower potential barrier than Pt, and thus enhance the electrocatalytic activity toward MOR.
29
Lin, Shu-Hsien, and 林書賢. "600 V PT-IGBT With Low Doping p-buffer Layer and Transparent P+ Emitter." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/09724855708796276871.
Повний текст джерелаАнотація:
碩士國立中央大學
電機工程研究所
99
The concept of energy conservation has become more and more respected. Due to the importance of green energy, medium and medium-high power electronics applications have been concerned. In this study, the proposed devices have no oscillation when turn-off in inductive load and also achieve low on-state voltage without sacrificing forward blocking drop so as to realize lower power consumption in circuitry applications. The design of the proposed devices adopted vertical structure with trench gate using Field-Stop technique, implantation from backside of the wafer to form the P+ collector. Additionally, there are two buffer layers in this structure, N+ buffer layer is formed by implantation and As as the dopant after annealing to activate then go on epitaxying the N-drift region. So there is thicker N+ buffer layer in this structure than typical FS-IGBT. The second buffer layer is P-type, the concentration is lower than P+ collector, this layer is the initial substrate and between N+ buffer layer and P+ collector interface in order to improve oscillation phenomenon. We found a tradeoff between on-state voltage and forward blocking drop. On-state voltage is about 1.29 V as injection efficiency at 0.28, in this low injection situation also can suppress oscillation phenomenon when turn-off and forward blocking voltage is approximate 710 V.
30
Huang, Chun-Hao, and 黃俊豪. "Superconductivity in the new electron-correlated 122-layer system CaT2Ge2 (T = Ir, Pd, Pt)." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/71926327246145198571.
Повний текст джерелаАнотація:
碩士國立清華大學
物理系
101
Superconductivity were observed in the new 122-layer compounds CaIr2Ge2 (Tc = 5.4 K) and CaPd2Ge2 (Tc = 2.5 K) with the BaFe2As2-type body-centered-tetragonal structure (bct, space group I4/mmm). For the pseudoternary Ca(Ir1-xPtx)2Ge2 system, superconducting transition Tc decreases from 5.4 K for CaIr2Ge2 (x = 0), to 3.8 K for x = 0.1, 3.0 K for x = 0.2, 2.2 K for x = 0.5, and below 2 K for x ﹥0.5. In addition to bct phase, x-ray powder differation pattern show the appearance of non-superconducting monoclinic 122-phase (space group P21, a < b, β > 90o). No Tc above 2 K was observed for the monoclinic compound CaPt2Ge2. Higher Tc in the bct CaIr2Ge2 is due to a strong quasi-2D Ir-Ge-Ir 5dxz,yz-4p-5dxz,yz hybridization in the Ir-Ge layer with the squeezed-along-c-axis IrGe4 tetragonal crystal field and the Ir-5d7 spin-orbital interaction. For the orthorhombic (11) layer system (Ir1-xPtx)Ge (space group Pnma), Tc decreases from 4.8 K for IrGe (x = 0), to 3.6 K for x = 0.1, 2.3 K for x = 0.2 and below 2 K for x ≧ 0.3, with low Tc of 0.4 K reported for PtGe.
31
"Temisc: a hybrid technique for layer replacement." Tese, MAXWELL, 1990. http://www.maxwell.lambda.ele.puc-rio.br/cgi-bin/db2www/PRG_0991.D2W/SHOW?Cont=9487:pt&Mat=&Sys=&Nr=&Fun=&CdLinPrg=pt.
Повний текст джерела
32
Chiu, Kuan-Chia, and 邱冠嘉. "Manipulation of Spin Current by Controlling the Thickness of AlOx Layer in Pt/AlOx/Py system." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/gcak96.
Повний текст джерелаАнотація:
碩士國立臺灣大學
應用物理研究所
105
The detection of spin current tunneling is being investigated by a technique of ferromagnetic resonance (FMR) with Inverse Spin Hall voltage (VISHE) measurement in Pt/AlOx/Py trilayer system. It is seen that the value of VISHE is apparently decreasing with the increasing thickness of oxide barrier. Furthermore,FMR and VISHE are also measured with the sample rotating out of plane with respect to the magnetic field direction. From the non-linear characteristic behaviour of I-V measurement in tunnelling magnetoresistance (MR) junction(CoFe/NiFe/AlOx/NiFe), it is confirmed that the quality of AlOx forms tunnelling junction. The combined results of FMR, VISHE and nonlinear I-V characteristic suggests that the spin transport mechanism from Py to Pt in Pt/AlOx/Py system is the tunnelling effect through the oxide barrier.
33
Lin, Ji-Hong, and 林季宏. "Exchange-spring effect of soft Fe top layer onto perpendicular magnetic anisotropy FePt/Pt/Cr trilayer." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/80332892311481539709.
Повний текст джерелаАнотація:
碩士國立臺灣大學
材料科學與工程學研究所
94
Nowadays, the areal density of longitudinal magnetic recording reaches their limits. If we keep on upgrading its recording densities, the only way is developing the perpendicular magnetic recording. But, some manufacturing issues of perpendicular magnetic recording need to be solved. For example: tilted easy axis to the film plane, higher soft-hard phase transition temperature, and large writing field of magnetic head to switch the moment of hard phase. In recent years, two problems, tilted easy axis and higher soft-hard phase transition temperature, were solved by epitaxial growth method. However, large writing field of head still confused the researchers. In this investigation, in order to reduce the writing field of magnetic head, we reduced the film coercivity by controlling depositing parameters. The concept of “Exchange Spring” was presented in our study. The film coercivity was largely reduced by capping a soft Fe layer on hard FePt(001) thin films. We found that the microstructures and magnetic properties were not influenced with depositing temperature and sputtering power. The magnetic properties were only affected by Fe layer thickness. When the Fe layer thickness is thinner than 5 nm, weak exchange coupling raised between Fe cap layer and FePt recording layer. When the thickness reached 10 nm, the strongest exchange coupling formed. Film coercivity didn’t distinctly vary as Fe layer thickness is thinner than 15 nm. Consequently, we measured DCD curves and had the same conclusions. Indeed, the appearance of exchange coupling is confirmed with 10 nm Fe cap layer. In our study, out-of-plane coercivity of Cr/Pt/FePt trilayer film is 2565 Oe. When the strongest exchange coupling appears between soft Fe cap layer and hard FePt(001) film, out-of-plane coercivity can be efficiently reduced to about 50%. This will solve the writing problem of perpendicular magnetic recording.
34
Jian, De Yuan, and 簡德淵. "The Effect of Pt-Al Top Electrode and Al2O3 Interfacial Layer on Gd2O3 Resistive Switching Memory." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/00788299933479718301.
Повний текст джерелаАнотація:
碩士長庚大學
電子工程學系
100
Recently, gadolinium oxide has been proposed to be applied in the resistive switching random-access memory (RRAM). It exhibits different resistive switching properties depending on the properties of electrodes. In this work, the characteristics of gadolinium oxide resistive switching memory with different component of Pt-Al alloy electrode and post-metallization annealing (PMA) were investigated. The current-voltage (I-V) characteristics demonstrate the bipolar resistance switching behavior of all samples. This can be responsible for the oxygen vacancies induced resistance switching between the Pt-Al alloy/GdxOy interface. The more Al diffused into the GdxOy resistive switching film will result in the formation of thicker interface domain on the interface, which will contribute to the increase of Schottky barrier height and the resistance of HRS. Moreover, the retention characteristics of the GdxOy RRAM with Pt-Al alloy electrode were significantly improved owing to the formation of interface domain between the Pt-Al alloy/GdxOy interface to prevent the oxygen ions from out-diffusing through Pt grain boundary to atmosphere. In order to increase the quantity of movable oxygen ions on the interface to improve the yield and electrical characteristic, PMA with different gas was applied.
35
Chih-Ming, Chen, and 陳志明. "Improvement of magnetic properties by introducing a diffusion layer and adjusting the Pt content for perpendicular media." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/c2vrch.
Повний текст джерела
36
Chou, Chen-wei, and 周政偉. "The transport properties of low temperature molten salt electrolytes containing EMIC and used for electrodeposited Pt layer." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/67084238249430195978.
Повний текст джерелаАнотація:
碩士國立雲林科技大學
工業化學與災害防治研究所
94
In our study, low temperature ternary molten salt system, EMIC-ZnCl2-PtCl2, and binary systems, EMIC-PtCl2 and EMIC-PtCl2 with organic solvent propylene carbonate (PC), were used as electrolytes to determine the electrical conductivity and the density, then further proceeded to the electrodeposition of platinum(Pt). The experimental results indicated that the conductivity of the low temperature ternary molten salt system, EMIC-ZnCl2-PtCl2, and binary systems, EMIC-PtCl2 and EMIC-PtCl2 with PC increased with increasing temperature or with PC concentration, and the conductivity decreased with increasing concentration of ZnCl2 or PtCl2. The density of EMIC-ZnCl2-PtCl2, EMIC-PtCl2 or EMIC-PtCl2 with PC molten salt decreased with increasing temperature or with PC concentration, and increased with increasing concentration of ZnCl2 or PtCl2. By using constant potential and pulse potential electrodeposition, the effect of varying potential, coulombs, and the pulse duration is studied. According to the SEM and EDS results, the electrodeposition of EMIC-ZnCl2-PtCl2 electrolyte can form a deposit of Pt-Zn alloy on constant potential of -0.9V or -1.0V. The electrodeposition of EMIC-PtCl2 electrolyte can form a uniform and granulous deposit of Pt on pulse potential of -0.7V, and the content of Pt increased with increasing coulomb numbers.
37
Chun-HanHsu and 許君漢. "Preparation and Catalytic Effect of Pt Loaded on Nitrogen-Doped Carbon Layer Surrounding Carbon Nanotubes through Polyaniline." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/31068770860137289067.
Повний текст джерела
38
"Smart wavelength routing assignment on wdm networks by functionality on physical layer." Tese, MAXWELL, 2001. http://www.maxwell.lambda.ele.puc-rio.br/cgi-bin/db2www/PRG_0991.D2W/SHOW?Cont=2056:pt&Mat=&Sys=&Nr=&Fun=&CdLinPrg=pt.
Повний текст джерела
39
Liu, Yoh-Rong, and 劉又榮. "Fabrication of Pt Catalyst on TiN Inverse Opal Structure for Proton Exchange Membrane Fuel Cell by Atomic Layer Deposition." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/57603714148206350869.
Повний текст джерелаАнотація:
碩士國立清華大學
材料科學工程學系
102
Titanium nitride (TiN) inverse opal structure was fabricated by atomic layer deposition (ALD) as a support for Pt catalyst for proton exchange membrane fuel cell (PEMFC) by atomic layer deposition (ALD). Polystyrene (PS) spheres were coated in multilayers on carbon paper by spin-coating as a template. The surface area can be increased by using smaller size of spheres and by increasing the thickness of PS multilayers. The proportion of micropores can also be adjusted by using spheres in different diameters. Titanium dioxide (TiO2) thin film was then deposited on PS sphere multilayers by ALD. Titanium nitride inverse opal structure was obtained by direct nitridation of TiO2 inverse opal structure in flowing ammonia atmosphere at 800 ˚C for 1 h. Platinum nanoparticles were then deposited on TiN inverse opal structure by ALD as well, and a uniform coverage down to 10 µm of depth was achieved. The particle size and loading could be controlled by the cycle number of ALD. Because of self-limiting reactions of ALD, the Pt loading can be increased by lowering the sphere size and increasing the thickness of TiN inverse opal layers. The performance of PEMFC using Pt/TiN inverse opals as electrodes was evaluated by a home-made PEMFC test station. The home-made electrodes showed lower power capacities but showed higher specific power densities and thus better utilization efficiency of Pt compared with that using commercial E-Tek electrodes.
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Tun, Sriana, and 史安菟. "Combination of Chemical Vapor Deposition and Atomic Layer Deposition Method for Pt-Ru Catalyst Deposition on Si(111) Substrate." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/03557303134725953357.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
化學工程系
97
Pt-Ru alloy can be produced with some methods. One of these methods is applying thin film technology. The aim of this research is to find the reaction zone of depositing Pt-Ru alloy catalyst by atomic layer deposition (ALD) method. Before using ALD method, the reactions of Ru precursor on various substrates were studied by chemical vapor deposition (CVD) method to understand the baseline of Ru-CVD. Then, we applied the baseline condition of CVD method to investigate the ALD growth regime. On the other hand, we investigated the Pt deposition by ALD method using hydrogen as the reactive gas. Finally, we tried to combine CVD and ALD method for the deposition of Pt-Ru binary catalysts on Si(111) substrate. Ru catalyst deposition by CVD method, the different regimes of reactions kinetics were taken place on different substrate, which resulted in different morphology of Ru catalyst by using bis(ethylcyclopentadienyl) ruthenium as precursor. Since Ru depositions were controlled by adsorption of precursor, Ru catalysts were more difficult applied by ALD method than by CVD method. The hydrogen was used as the reactive gas to react with trimethylcyclopentadienyl platinum for Pt ALD. Close to 1 ML deposition of Pt can be achieved at substrate temperatures of 300 and 350oC. 2s exposure time of purge obtained good result for 4s exposure time of precursor but not enough when exposure time of precursor was increased to 6s. Increasing exposure time of hydrogen as the reactive gas resulted in a quite low growth rate because the hydrogen would remove the precursor, though they might not react to each other. Combination of Ru CVD and Pt ALD methods applied in DMFCs using oxygen as reactive gas gave the better performance compared with using hydrogen gas. Moreover, the CO poison of Pt catalysts can be eliminated by the combination of Ru CVD and Pt ALD methods.
41
Hsu, Shih-Chieh, and 許世杰. "Plasma Enhanced Atomic Layer Deposition of Pt nanoparticles on the TiO2 substrate as the catalyst for Direct Methanol Fuel Cells." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/67126144345697352700.
Повний текст джерелаАнотація:
碩士國立交通大學
材料科學與工程學系
100
Platinum has a superior electrocatalytic activity toward methanol oxidation reaction (MOR) and, therefore, Pt is the most preferred catalyst used in direct methanol fuel cells (DMFCs). In the present time, the most widely studied subject in DMFC research is to reduce the size and to optimize the distribution of Pt nanoparticles for minimizing the use of the precious Pt catalyst and concurrent increasing the electroactivity surface area (ESA) for methanol oxidation. In addition, metal oxides can be used as the Pt support to enhance the electrocatalytic efficiency of the Pt catalyst. In this works, we used plasma-enhanced atomic layer chemical vapor deposition (PEALD) to deposit Pt nanoparticles on the TiO2 substrate, and study the electrocatalytic activity of the Pt nanoparticles toward MOR as a function of the particle size. A TiO2 thin film was prepared on the Si substrate by electron beam evaporation, and Pt nanoparticles were deposited on the TiO2 thin film by PEALD at 200oC using MeCpPtMe3 as the Pt precursor and O2 as the oxidant of the precursor. The size of Pt nanoparticles can be well controlled by varying the number of the ALD reaction cycle. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that well-dispersed Pt nanoparticles were deposited on the TiO2 surface and the particle size of Pt nanoparticles was in the range between 3 nm and 13 nm depending on the ALD cycle number. Cyclic voltammetry (CV) and CO stripping analysis were performed to study the electrocatalytic activity of the Pt/TiO2 electrode toward MOR under acidic media. The electrocatalytic activity and the CO tolerance of the electrode are a function of the Pt ALD cycle number. We found that the electrode with a Pt ALD cycle number of 35 had the best electrochemical performance. When the ALD cycle number was larger than 50, Pt nanoparticles coalesced, and the electrode exhibited a electrochemical performance for MOR similar to a Pt thin film. The excellent electrocatalytic activity is ascribed to the synergistic effect of the nanometer sized of Pt nanoparticles and the electronic interaction between the TiO2 support and the Pt nanoparticles. Charge transfer between Pt nanoparticles and the TiO2 support may modify CO chemisorption properties on the Pt nanoparticles, thereby facilitating CO oxidation via the bi-functional mechanism and thus improving the electrocatalytic activity of the Pt catalyst toward methanol oxidation.
42
Liu, Chia-Lun, and 劉家綸. "Study and Fabrication of Al2O3/Pt/Al2O3/Ti Multi-layer Structure Designed by CUDA Parallel Computing for Solar Selective Absorbers." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/64866628925233051865.
Повний текст джерела
43
Liu, Chung-Hsuan, and 劉仲軒. "Plasma enhanced atomic layer deposition of Pt nanoparticles for studying the size effect on the electrocatalytic activity toward methanol oxidation reaction." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/37631280080472220223.
Повний текст джерелаАнотація:
碩士國立交通大學
材料科學與工程學系所
102
This study prepared Pt nanoparticles with different particle sizes on a native TiO2 surface layer of a Ti thin film by plasma enhanced atomic layer deposition (PEALD), and investigated the Pt particle size effect on the electrocatalytic activity towards methanol oxidation reaction (MOR) in acidic media. The Pt nanoparticles size increases with the number of the PEALD reaction cycle, and the Pt nanoparticles have an average size between 3 nm and 7.3 nm depending on the PEALD reaction cycle number, which varies from 12 to 50 cycles in this study. From cyclic voltammetry measurements, the Pt particle size is the smaller, the electrochemical surface area is the larger and the CO tolerance in MOR is the better. According to x-ray photoelectron spectroscopy analysis, charge transfer between the Pt nanoparticles and the TiO2 support is insignificant, indicating that the better electrochemical properties of smaller Pt nanoparticles can be understood mainly by bi-functional mechanism. CO adspecies on smaller Pt nanoparticles can be oxidized more easily by hydroxyl adspecies migrating from the hydrophilic TiO2 surface, leading to a higher electrocatalytic activity of the Pt/TiO2 electrode towards MOR in the acidic media.
44
Chuang, Chin-Yao, and 莊錦堯. "Optimal synthesizing ratio of Pt/CNT and Nafion content in the preparation of cathode catalyst layer for a PEM fuel cell." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/76728287601886208818.
Повний текст джерелаАнотація:
碩士大同大學
機械工程學系(所)
101
This study aimed to explore the optimal synthesizing ratio of Pt/CNT and Nafion content in the preparation of cathode catalyst layer for a PEM fuel cell, the experiments focused on production of the catalyst layer with multi-walled carbon nanotubes as platinum support, the catalyst layer was fabricated by different weight percentage ratio of Pt/CNT electrode catalyst production to explore the best of Pt/CNT synthesis scale production of the catalyst layer, then change the Nafion content of the best Nafion concentration in catalyst layer. Experimental methods including fuel cell performance polarization curve measurements, electrochemical impedance spectroscopy, cyclic voltammetry analysis and exchange current density analysis. The results show that platinum / carbon nanotube carrier, when the platinum weight percentage concentration of 30 wt% and Nafion content of 25 wt% was obtained the top of the fuel cell performance, under the same loading of platinum, if the Pt concentration is too much or too less may leads to a loss in fuel cell performance in Pt/CNT catalyst, the research enables to application of Pt/CNT catalyst layer production technology improved, and enhance fuel cell performance.
45
Mukhopadhyay, Ankan. "Fundamental aspects of the interface engineering in the heavy metal/ferromagnet-based perpendicularly magnetized systems." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5609.
Повний текст джерелаАнотація:
The ferromagnetic (FM) material finds its applications due to the property of spontaneous magnetization. An FM object can hold its state of magnetization unless any external stimuli change it. The easy manipulation of its state by an external magnetic field or spin current manifests FMs usability for digital data storage and logic devices. The efficiency and speed of magnetic data storage and logic devices should be optimized to match the existing semiconductor devices. This thesis has mainly proclaimed the fundamental dependence of magnetism on the composition of the layers and geometry, established the nexus to understand the underlying physics to identify the promising candidates for data storage applications in the future.
In the first work, systematically modifying the strength of the induced moment in the bottom Pt layer by the thickness variation of the adjacent Ta buffer layer, the Pt spin depth profiles in Ta/Pt/Co/Pt multilayers induced by the magnetic proximity effect due to the adjacent Co layer have been quantified. The Pt spin depth profiles by hard x-ray resonant magnetic reflectivity measurements have been identified, which have been carried out at the third-generation synchrotron PETRA III at DESY. It has been found that the top Pt layer has a comparable induced magnetic moment with the bottom one. The induced magnetic moment in the bottom Pt layer reduces with increasing Ta thickness. Grazing incidence x-ray diffraction measurements have been carried out to show that the Ta buffer layer induces the growth of Pt(011) rather than Pt(111) which in turn reduces the induced moment as confirmed by detailed density functional theory calculations presented in our manuscript.
In the second work, the tilt in magnetic anisotropy and strength of the interfacial Dzyaloshinskii-Moriya interaction (iDMI), in the Pt/Co interface of the Pt/Co/Pt trilayers simultaneously have been quantified. The differential polar-Kerr microscopy technique in the creep regime of the domain wall motion for these measurements has been used. It has been found that an oblique angle sputter deposition technique results in a slight tilt of magnetic anisotropy from the film normal (quasi-perpendicular magnetic anisotropy). The effective in-plane field at the domain wall due to iDMI has been determined by decomposing the symmetric and asymmetric contributions of the domain wall motion. Furthermore, the asymmetric contribution has been decomposed into two contributions due to the tilted magnetic anisotropy and the exponentially decaying chiral damping. The collective coordinate model for a system with iDMI and quasi-PMA has been developed to study the nature of the asymmetric contribution owing to the tilted anisotropy and a functional form of the total asymmetric contribution has been determined from the simulation result.
In the third work, the effective strength of the iDMI, in the Ta/Pt/Co/Au multilayers has been estimated using the field-induced domain wall motion and spin-orbit torque efficiency estimation studies. The current-induced magnetization switching phase diagram has also been constructed. It has been found that from the phase diagram, the effective strength of the iDMI can be quantified. Multilayers with the heavy metal Pt and the novel metal Au on either side of the ferromagnetic Co layer break the structural inversion symmetry, enhancing the iDMI strength.
46
Lee, Chao-Te, and 李昭德. "Study of CoTbX thin films (X=Pd, Cu, Au, Pt) and their possibility for application to the single layer thermo-magnetic recording media." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/82592645962800594272.
Повний текст джерелаАнотація:
博士國立臺灣大學
材料科學與工程學研究所
92
The CoTbX films (X=Pd, Cu, Au, Pt, Ni, Al) were deposited on glass and naturally oxidized silicon wafer substrates at room temperature by dc magnetron sputtering. The magnetic film was sandwiched by SiNx protective layers to prevent oxidization. The SiNx protective layers were produced by rf magnetron sputtering of Si3N4 target Thickness of the magnetic layer and SiNx layer were 75 nm and 30 nm, respectively. The effects of X content (where X=Pd, Cu, Au, Pt, Ni, Al) on the magnetic properties and microstructure of the film were investigated. The X-ray diffraction and transmission electron microscope diffraction pattern revealed that all the films were amorphous. It shows that substituting small amount of Co for non-magnetic element Cu，Au or Pt will increase the saturation magnetization, the perpendicular remanence of the Co70.5Tb29.5 film. It was found that the saturation magnetization of the Co67.25Tb29.5Pt3.25 film is about 330 emu/cm3, the perpendicular squareness is about 0.85, perpendicular coercivity is about 2500 Oe at room temperature. This film is a promising candidate for hybrid recording media applications.
47
Chi, Chin-Fa, and 紀景發. "Improvement on the Performance of the Anode Catalyst Layer in DMFC by using mixtures of Carbon Materials as support for Pt-Ru/C." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/14571693082272219939.
Повний текст джерелаАнотація:
碩士國立成功大學
化學工程學系碩博士班
94
Abstract The main object of this study is to improve the performance of the anode catalyst in direct methanol fuel cell. The previous investigation reveals that with the same metal loading on carbon black, the performance of of the catalyst prepared by multiple impregnation for electrocatalytic oxidation of methanol is obviously better than that by single impregnation, and when the mixture of carbon black and carbon nanotube with a ratio of 1:1 was used as the support for Pt-Ru/C, the catalyst has the best electrocatalytic activity. In this succeeding work, four kinds of carbon materials were used as the supports for Pt-Ru/C, including carbon black(XC-72), mesoporous carbon(MC) and two different types of carbon nanotubes(CNT), the effect of pore structures of these carbon materials and the addition of CNT to XC-72 and MC on the performance of Pt-Ru/C catalysts were investigated. Experimental results reveal that when preparing 10wt% Pt-Ru/C with carbon black and mesoporous carbon as the supports, using the different reducting agents and concentrations of precursor would result in different Pt-Ru particles sizes and dispersion on carbon materials, in turn, would affect the surface area and pore size distribution of catalysts. However, their effects on the electrochemical performance should be further investigated. When the catalyst was prepared by multiple impregnation, because of the low precursor concentration, the size of Pt-Ru particles would be smaller and hence the dispersion of Pt-Ru particles and electrochemical performance would be better. Pt-Ru/XC and Pt-Ru/MC catalysts with 10 wt % Pt prepared by carbon black and mesoporous carbon as the support and by three-time impregnation have higher electrocataltytic activity for methanol oxidation. Their activities are about 95% and 90% of that of the commercial catalyst E-TEK (with 20 wt % Pt), respectively. Adding CNT or CNT(10), [CNT(x) represents CNT containing X wt % of Pt] to Pt-Ru/XC and Pt-Ru/MC would also improve the electrochemical performance. The optimum adding amounts of CNT(10) are 5 wt % for the former and 20 wt % for the latter. Their electrochemical performances are almost the same as that of E-TEK. The addition of 5 wt % and 20 wt % CNT(20) to Pt-Ru/XC and Pt-Ru/MC catalysts (both containing 20 wt % ) would give activities 20 % and 10 % higher than that of E-TEK Pt-Ru/C catalyst containing 20 wt % Pt, respectively. When CNT or CNT with loaded Pt-Ru will be added to Pt-Ru/carbon catalyst, electrical conductivity, diameter, length and entanglement of carbon nanotubes should be considered first. Besides, the particle size, surface area and pore size distribution of the carbon support are also important factors. In further studies, we will focus on those factors to elucidate how they affect the electrochemical performance. Note that the results obtained in the present study can be also applied to the proton exchange membrane fuel cell (PEMFC) with hydrogen as the feed.
48
Dhanushkodi, Shankar Raman. "Experimental Methods and Mathematical Models to Examine Durability of Polymer Electrolyte Membrane Fuel Cell Catalysts." Thesis, 2013. http://hdl.handle.net/10012/7619.
Повний текст джерелаАнотація:
Proton exchange membrane fuel cells (PEMFC) are attractive energy sources for power trains in vehicles because of their low operating temperature that enables fast start-up and high power densities. Cost reduction and durability are the key issues to be solved before PEMFCs can be successfully commercialized. The major portion of fuel cell cost is associated with the catalyst layer which is typically comprised of carbon-supported Pt and ionomer. The degradation of the catalyst layer is one of the major failure modes that can cause voltage degradation and limit the service life of the fuel cell stack during operation. To develop a highly durable and better performing catalyst layer, topics such as the causes for the degradation, modes of failure, different mechanisms and effect of degradation on fuel cell performance must be studied thoroughly.
Key degradation modes of catalyst layer are carbon corrosion and Pt dissolution. These two modes change the electrode structure in the membrane electrode assembly (MEA) and result in catalyst layer thinning, CO2 evolution, Pt deposition in the membrane and Pt agglomeration. Alteration of the electrode morphology can lead to voltage degradation.
Accelerated stress tests (ASTs) which simulate the conditions and environments to which fuel cells are subject, but which can be completed in a timely manner, are commonly used to investigate the degradation of the various components. One of the current challenges in employing these ASTs is to relate the performance loss under a given set of conditions to the various life-limiting factors and material changes. In this study, various degradation modes of the cathode catalyst layer are isolated to study their relative impact on performance loss ‗Fingerprints‘ of identifiable performance losses due to carbon corrosion are developed for MEAs with 0.4 mg cm−2 cathode platinum loadings. The fingerprint is used to determine the extent of performance loss due to carbon corrosion and Pt dissolution in cases where both mechanisms operate. This method of deconvoluting the contributions to performance loss is validated by comparison to the measured performance losses when the catalyst layer is subjected to an AST in which Pt dissolution is predominant. The limitations of this method
iv
are discussed in detail. The developed fingerprint suggests that carbon loss leading to CO2 evolution during carbon corrosion ASTs contributes to performance loss of the cell. A mechanistic model for carbon corrosion of the cathode catalyst layer based on one appearing in the literature is developed and validated by comparison of the predicted carbon losses to those measured during various carbon corrosion ASTs. Practical use of the model is verified by comparing the predicted and experimentally observed performance losses. Analysis of the model reveals that the reversible adsorption of water and subsequent oxidation of the carbon site onto which water is adsorbed is the main cause of the current decay during ASTs.
Operation of PEM fuel cells at higher cell temperatures and lower relative humidities accelerates Pt dissolution in the catalyst layer during ASTs. In this study, the effects of temperature and relative humidity on MEA degradation are investigated by applying a newly developed AST protocol in which Pt dissolution is predominant and involves the application of a potentiostatic square-wave pulse with a repeating pattern of 3s at 0.6 V followed by 3s at 1.0 V. This protocol is applied at three different temperatures (40°C, 60°C and 80°C) to the same MEA. A diagnostic signature is developed to estimate kinetic losses by making use of the effective platinum surface area (EPSA) obtained from cyclic voltammograms. The analysis indicates that performance degradation occurs mainly due to the loss of Pt in electrical contact with the support and becomes particularly large at 80°C.
This Pt dissolution AST protocol is also investigated at three different relative humidities (100%, 50% and 0%). Electrochemical impedance spectroscopy measurements of the MEAs show an increase in both the polarization and ohmic resistances during the course of the AST. Analysis by cyclic voltammetry shows a slight increase in EPSA when the humidity increases from 50% to 100%. The proton resistivity of the ionomer measured by carrying out impedance measurements on MEAs with H2 being fed on the anode side and N2 on the cathode side is found to increase by the time it reaches its end-of-life state when operated under 0 % RH conditions.
49
Wu, Yu-fu, and 吳祐福. "An Investigation of Bimetallic Nanocatalysts Pt-Ir Coated Multi-Walled Carbon Nanotubes for Glucose Sensing and Growth of MoNx Films by Reactive Sputtering and Investigation of Failure Mechanism as A barrier layer of Copper Metallization." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/3ndz4h.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
化學工程系
99
There are two topics investigated in this thesis. One is about biosensor, the other is diffusion barrier. For the research on biosensor, different enzyme immobilization methods were studied on the effect of the detection linear range and sensitivity. For the naked electrode immersed in enzyme solution with 181 units, the linear range of sensing was 1 to 6 mM and the sensitivity was 7.81 μA/mM. For the enzyme of 7.2 units entrapped in sol-gel, the linear range located at 2 to 12 mM and the sensitivity was 1.74 μA/mM. The estimated amount of impregnated enzyme was about 60%.. In addition, we successfully coated the alloy of platinum and iridium nanoparticles on the multiwall carbon nanotubes which promoted electrochemical performance significantly. The equivalent resistance for the bare gold electrode and the modified gold were 1033.6 Ω and 0 Ω, respectively by the electrochemical impedance spectroscopy analyses. Moreover, the nanotube composites revealed characteristics of catalysts that it catalyzed H2O2 which was produced by enzyme and glucose under low voltage although the reaction was limited due to dissolution of oxygen. The sensing linear range was 1 to 5 mM and the sensitivity was 0.52 μA/mM. The sensitivity was further promoted by adding mediator into the system that the linear range was 2 to 12 mM and sensitivity was 1.93 μA/mM. The diffusion barriers were evaluated by the MoNx thin films which were deposited on silicon by reactive sputtering. The failure mechanism for the diffusion barriers on Cu/Si multilayered system was investigated. The results showed that the deposition rate, N/Mo atomic ratio, crystalline structure, resistivity and surface morphology of MoNx thin film depended on the N2/Ar flow ratio. The deposition rate of MoNx thin film decreased as the N2/Ar flow ratio increased. With increasing N2/Ar flow ratio of MoNx thin film, the phase transformation was identified as cubic Mo to γ-Mo2N. The N/Mo atomic ratio and resistivity increased with increased the N2/Ar flow ratio. When the N2/Ar flow ratio was 0, a minimum resistivity of 16.9 μΩ-cm in film was also obtained. Then deposition the Cu(60 nm)/MoNx(25 nm)/Si multilayers was grown by in-situ to analyze the properties of Cu diffusion barrier. We utilized SEM, XPS, XRD, TEM and FPP to observe diffusion and reaction phenomenon of diffusion barrier in Cu/Si multilayered system after thermal treatments and obtained the diffusion coefficient and diffusion activation energy of the barrier with different N2/Ar flow ratio. Finally, the experimental results indicated that the failure temperature of Cu(60 nm)/MoNx(25 nm)/Si multilayered structure raised as the nitrogen concentration of diffusion barrier increased. Moreover, the barrier with N2/Ar flow ratio at 0.5 ( MoN0.75 ) possessed the best barrier performance. It was found that the MoN0.75 film prevented the Cu-Si interaction up to 625 ℃. Moreover, the Cu/MoN0.75/Si was fairly stable up to annealing at 650~700 ℃ for 30 minutes.
50
Ou, Lih-yuarn, and 歐瀝元. "Study of laser-assisted photoelectric effect on Pt(111) surface." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/25555629673346347332.
Повний текст джерелаАнотація:
碩士國立中央大學
物理研究所
98
High-order harmonics generated from laser-irradiated gas target is a coherent light source ranging from extreme ultraviolet to soft x-ray, with very short pulse duration, high spatiotemporal coherence, and low beam divergence. It can be used in the study of chemical reactions, molecular dynamics, surface catalysis, and transient electronic structures of condensed matters. It has been demonstrated that high-order harmonics can be applied to the experiment of laser-assisted photoelectric effect on metallic surface. In the thesis, the principle of the laser-assisted photoelectric effect is firstly introduced. Then the experimental setup of high-order harmonic generation and laser-assisted photoelectric effect on Pt(111) surface are presented, together with the analysis and discussion of the results. The angular distribution of the photoelectron energy spectrum and the modification of the spectrum resulted from laser-assisted photoelectric effect are observed.