Dissertations / Theses on the topic 'Nanostructured metal'
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Eskhult, Jonas. "Electrochemical Deposition of Nanostructured Metal/Metal-Oxide Coatings." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8186.
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Li, Li. "Versatile applications of nanostructured metal oxides." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245303.
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This thesis explores applications of nanostructured metal oxides in photocatalysis, electrochromism and Raman spectroscopy. A variety of highly periodic nanoscale morphologies derived from block-copolymer self-assembly inspire the fabrication of well-ordered nanoporous metal oxide materials. Beginning with block-copolymer directed sol-gel chemistry, we have synthesized crystalline tungsten oxide consisting of micellar or cylindrical pores with uniform sizes. This porous structure reduced diffusion limitations of the reagents, allowing the easy access to a large surface area, therefore improving the photocatalytic activity compared to the non-structured material. This is followed by the fabrication of 3D highly interconnected gyroid-structured vanadium oxide via a simple, scalable and low cost replication strategy using a sacrificial polymer template derived from block-copolymer microphase separation. The electrochromic device fabricated using gyroid-structured vanadium oxide film showed significantly improved coloration responses, because the interconnected porous network greatly shortened the diffusion length of electrolyte ions. Then, the usage of metallic nanoparticles in enhanced Raman spectroscopy is explored. Au nanoparticles were employed as the Raman enhancer to probe the influence of interfacial reactions on the molecules adsorbed on a metal oxide (vanadium oxide) electrode. The spectral intensities and Raman shifts were found to be strongly dependent on the interfacial ion intercalation/extraction processes associated with the variations of the applied electric field. Next, the use of metal oxide nanoparticles in enhanced Raman spectroscopy is investigated. Metal oxide nanoparticles with high refractive indices when placed on top of metal surfaces can effectively enhance the Raman scattering field at the interface. This capability of Raman enhancement in combination with the range of functions of metal oxide nanoparticles opens up a novel approach to study the interfacial phenomena. Using this system, interfacial photocatalytic reactions of an organic dye catalyzed by titanium oxide nanoparticles were investigated by directly monitoring Raman scattering signals enhanced by the same nanoparticles. A diversion from metal oxides uses an Au nanoparticle on Au plane system as a surface- enhanced Raman scattering substrate. At the junction between an Au nanoparticle and an Au film, the electromagnetic field can be enhanced to an extent that single molecules can be detected. The use of such substrates to probe various molecules was also explored.
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Astuti, Yeni. "Bio-functionalised nanostructured metal oxide electrodes." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429459.
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Popov, M. Yu, A. P. Volkov, S. G. Buga, V. S. Bormashov, K. V. Kondrashov, R. L. Lomakin, N. V. Lyparev, V. V. Medvedev, S. A. Tarelkin, and S. A. Perfilov. "Nanostructured metal-fullerene field emission cathode." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20585.
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One of the important properties of carbon nanostructures is their cold electron
emission ability. Carbon nanotubes and other nanostructures are capable of
emitting high currents at relatively low electrical fields. They are already
used in functional devices such as field emitters. The conventional method of
carbon nanostructured cathodes manufacturing is thin film nanocarbon deposition
using CVD process on electrically conducting substrate like metal or doped
silicon plates. The alternative way of manufacturing of carbon field emission
cathodes is based on a special processing of carbon microfibers or composite materials in metal holders. We used the similar approach to produce composite
metal-nanocarbon material which may be easily processed and shaped to
produce an effective field emission cathode which can be easily fixed an any
environment.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20585
5
杨纯臻 and Chunzhen Yang. "Metal/metal oxide nanoparticles supported on nanostructured carbons for electrochemical applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/193414.
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Among various electrochemical devices that have been developed for energy storage and conversion, electric double layer capacitors (EDLCs) and direct methanol fuel cells (DMFC) have received much research attention. Nanostructured carbon materials have been playing an important role in the development of these devices, due to such characteristics as good electrical conductivity, high chemical stability, high surface area and large pore volumes and etc. In an EDLC, nanostructured carbon electrodes, possessing pores of varied length scales, can deliver electric energy at high current loadings. This kind of pore structure also benefits the deposition of metal catalysts and the transport of reactants and products in the methanol oxidation reaction.
In order to systematically study the structural effects on the electrochemical capacitance and ionic transport, a series of three-dimensional hierarchical carbons with hollow core-mesoporous shell (HCMS) structure were template-synthesized. Periodically ordered macroscopic hollow cores of 330 nm in diameter were surrounded by a mesoporous shell containing uniform pores of 3.9 nm. The shell thickness was stepwise increased from 0, 25, 50 to 100 nm. The HCMS structure was modeled by a 5-level transmission line model to study the capacitance contribution from the pores at different length scale. Results revealed that the HCMS carbon with thicker mesoporous shells can provide high capacitance, while thinner shells could deliver high power output.
A series of HCMS carbon sphere supported Pt nanoparticles were synthesized via the “Carbonization over Protected and Dispersed Metal” (CPDM) method. Contrary to the conventional “polyol” synthetic method, whereas most of Pt nanoparticles were deposited on the external surface of carbon spheres; the Pt nanoparticles synthesized via the CPDM method were found encapsulated in the mesoporous carbon shells and highly dispersed throughout the carbon texture. „Accelerated stress tests‟ (ASTs) were conducted to investigate the nanopores confinement effect toward the electrochemical stability of these Pt catalysts. Results revealed that (1) the nanopores confined Pt nanoparticles on HCMS carbon spheres exhibited a stable electrochemical active surface area (ECSA) and catalytic activity; and (2) thick mesoporous carbon shells could provide better protection over the Pt nanoparticles. This “CPDM” method was further extended to synthesize highly alloyed PtRu nanoparticles supported electrocatalysts. It is expected that this CPDM method can also be applied to synthesize other metal/metal oxide supported catalysts with stable electrochemical performance.
WO3 has been demonstrated as a promsing co-catalyst for Pt in the methanol oxidation reaction (MOR). The synthesis of Pt-WO3/C catalyst with well-controlled nanoparticle size (2.5 nm) and composition was achieved via a microwave-assisted water-oil microemulsion reaction. Hydrogen adsorption, CO-stripping and Cu- stripping methods were used to estimate the ECSA of Pt in the Pt-WO3/C catalysts. Among these, Cu-stripping method was relatively more reliable due to the overlapping involvement of the WO3 component in the other methods. The methanol oxidation measurement shows that a 1:1 Pt:W ratio catalyst exhibits the highest Pt-mass current density of 271 mA mg-1-Pt, 1.4 times higher than that of commercial E-TEK catalyst.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
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Zuo, Yong. "Nanostructured Metal Sulfides for Electrochemical Energy Conversion." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/670925.
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Storing the fluctuating renewable energy into synthetic fuels or in batteries is meaningful due to the emerging energy crisis. In this thesis, four nanostructured catalysts based on two kinds of metal sulfides, namely Cu2S and SnS2, were produced and optimized to improve their performance towards three key electrochemical energy conversion processes, namely electrochemical oxygen evolution, photoelectrochemical water splitting and lithium-ion batteries. Chapter 1 presented a general introduction to explain the motivation of the thesis topic. In chapter 2, a metallic copper substrate was used as current collector and chemical template to produce Cu2S nanorod arrays for electrochemical oxygen evolution reaction (OER). Suitable characterization tools were applied to investigate the chemical, structural and morphological transformation in OER operation, during which the initial Cu2S nanorod arrays would perform as a “pre-catalyst” that in-situ changed to CuO nanowires. Notably, the Cu2S-derived CuO showed significant improved OER performance compared with that of CuO prepared by directly annealing a Cu(OH)2 precursor, in terms of both activity and stability. Thus obtained electrocatalyst can be ranked among the best Cu-based OER catalysts reported so far. To take advantage of the unlimited solar energy, an ultrathin SnS2 NPL with a suitable band gap around
2.2 eV was produced via a hot-injection solution-based process in chapter 3. The unsatisfied photoelectrochemical (PEC) performance of bare SnS2 motivated me to deposit Pt NPs on its surface as cocatalyst via in-situ reduction of a Pt salt. The resulting SnS2-Pt heterostructures with optimal Pt amount showed significant improvement (six fold) towards PEC water oxidation. Mott-Schottky analysis and PEC impedance spectroscopy (PEIS) were used to analyze in more detail the effect of Pt on the PEC performance. The optimal SnS2-Pt heterostructure presented acceptable performance towards PEC water splitting. However, it still suffered from a moderate stability due to the peel-off of the catalyst layer from the FTO surface. To solve this problem, in chapter 4 we detailed a simple, versatile and scalable amine/thiol- based molecular ink to grow nanostructured SnS2 layers directly on conductive substrates such as FTO, stainless steel and carbon cloth. Such layers on FTO were characterized by excellent photocurrent densities. The same strategy was used to produce SnS2-graphene composites, SnS2-xSex ternary coatings and even phase pure SnSe2 layers. Finally, the potential of this precursor ink to produce gram scale amounts of unsupported SnS2 was also investigated. Apart from the application as a photocatalyst, SnS2 can also be a promising anode material for Li-ion batteries (LIB). In chapter 5, nanostructured SnS2 with different morphologies produced in chapter 3 were tested as LIB anodes firstly to find that thin SnS2 NPLs provided the highest performance. Thereafter, a colloidal synthesis strategy to grow the same SnS2 NPLs within a matrix of porous g-C3N4 (CN) and graphite plates (GPs) was developed and the obtained materials were tested for LIB application. Such hierarchical SnS2/CN/GP composites using SnS2-NPL as active materials, porous CN to provide avenues for electrolyte diffusion and ease
the volumetric expansion of SnS2, and GP as “highways” for charge transport displayed excellent rate capabilities (536.5 mAh g-1 at 2.0 A g-1) and an outstanding stability (~99.7 % retention after 400 cycles), which were partially associated with a high pseudocapacitance contribution (88.8 % at 1.0 mV s-1). The excellent electrochemical properties of these nanocomposites were ascribed to the synergy created between the three components. Overall, four nanostructured catalysts based on Cu2S and SnS2 were prepared, and proper optimizations/treatments were defined to improve their catalytic performance. The results shown in this thesis demonstrate the promising application of non-toxic, low cost metal sulfides in electrochemical energy conversion technologies.En esta tesis, se produjeron y optimizaron cuatro catalizadores nanoestructurados basados en Cu2S y SnS2 para mejorar su rendimiento hacia la conversión de energía electroquímica. El Capítulo 1 presentó una introducción general para explicar la motivación del tema de tesis. En el capítulo 2, las matrices de las nanovarillas de Cu2S se sintetizaron in situ sobre un sustrato de cobre metálico para la reacción electroquímica de evolución de oxígeno (OER). Se aplicaron herramientas de caracterización adecuadas para investigar la transformación en la operación OER, durante la cual las matrices iniciales de las nanovarillas Cu2S in situ cambió a nanohilos de CuO. En particular, el CuO derivado de Cu2S mostró un rendimiento de OER significativamente mejor cuando comparado al de CuO preparado mediante el recocido. En el capítulo 3, se detalló un proceso basado en una solución de inyección en caliente para producir nanoplacas ultrafinas SnS2 (NPL). Posteriormente, se cultivóPt en su superficie mediante la reducción in situ de una sal de Pt. Posteriormente se probó el rendimiento fotoelectroquímico (PEC) de los fotoanodes hacia la oxidación del agua. Los fotoanodes de SnS2-Pt optimizados proporcionaron densidades de fotocorriente significativamente más altas que el SnS2 desnudo (seis veces). Se analizó el efecto de Pt. En el capítulo 4, se informó una tinta molecular simple para cultivar capas de SnS2 nanoestructuradas directamente sobre sustratos conductores. Tales capas nanoestructuradas en FTO se caracterizaron por excelentes densidades de fotocorriente. Se utilize la misma estrategia para producir compuestos de grafeno-SnS2, recubrimientos ternarios SnS2-xSex, capas de SnSe2 de fase pura e incluso polvo de SnS2 a gran escala. En el capítulo 5, el SnS2 nanoestructurado con diferentes morfologías se probaron como ánodos LIB en primer lugar para encontrar que los NPL de SnS2 delgados proporcionaban el mayor rendimiento. Posteriormente, se desarrolló una estrategia de síntesis coloidal para cultivar los mismos NPL de SnS2 dentro de una matriz de g-C3N4 (CN) poroso y placas de grafito (GP) y se probaron para la aplicación LIB. Tales compuestos jerárquicos SnS2/CN/GP mostraron excelentes propiedades electroquímicas, lo que se atribuye a la sinergia creada entre los tres componentes como se investigó.
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Paul, Blain. "Nanostructured metal oxides as adsorbents and photocatalysts." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/41758/1/Blain_Paul_Thesis.pdf.
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This research underlines the extensive application of nanostructured metal oxides in environmental systems such as hazardous waste remediation and water purification. This study tries to forge a new understanding of the complexity of adsorption and photocatalysis in the process of water treatment. Sodium niobate doped with a different amount of tantalum, was prepared via a hydrothermal reaction and was observed to be able to adsorb highly hazardous bivalent radioactive isotopes such as Sr2+ and Ra2+ions. This study facilitates the preparation of Nb-based adsorbents for efficiently removing toxic radioactive ions from contaminated water and also identifies the importance of understanding the influence of heterovalent substitution in microporous frameworks. Clay adsorbents were prepared via a two-step method to remove anionic and non-ionic herbicides from water. Firstly, layered beidellite clay was treated with acid in a hydrothermal process; secondly, common silane coupling agents, 3-chloro-propyl trimethoxysilane or triethoxy silane, were grafted onto the acid treated samples to prepare the adsorption materials. In order to isolate the effect of the clay surface, we compared the adsorption property of clay adsorbents with ƒ×-Al2O3 nanofibres grafted with the same functional groups. Thin alumina (£^-Al2O3) nanofibres were modified by the grafting of two organosilane agents 3-chloropropyltriethoxysilane and octyl triethoxysilane onto the surface, for the adsorptive removal of alachlor and imazaquin herbicides from water. The formation of organic groups during the functionalisation process established super hydrophobic sites along the surfaces and those non-polar regions of the surfaces were able to make close contact with the organic pollutants. A new structure of anatase crystals linked to clay fragments was synthesised by the reaction of TiOSO4 with laponite clay for the degradation of pesticides. Based on the Ti/clay ratio, these new catalysts showed a high degradation rate when compared with P25. Moreover, immobilized TiO2 on laponite clay fragments could be readily separated out from a slurry system after the photocatalytic reaction. Using a series of partial phase transition methods, an effective catalyst with fibril morphology was prepared for the degradation of different types of phenols and trace amount of herbicides from water. Both H-titanate and TiO2-(B) fibres coated with anatase nanocrystal were studied. When compared with a laponite clay photocatalyst, it was found that anatase dotted TiO2-(B) fibres prepared by a 45 h hydrothermal treatment followed by calcination were not only superior in performance in photocatalysis but could also be readily separated from a slurry system after photocatalytic reactions. This study has laid the foundation for the development of the ability to fabricate highly efficient nanostructured solids for the removal of radioactive ions and organic pollutants from contaminated water. These results now seem set to contribute to the development of advanced water purification devices in the future. These modified nanostructured materials with unusual properties have broadened their application range beyond their traditional use as adsorbents, to also encompass the storage of nuclear waste after concentrating from contaminated water.
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Gu, Yanjuan, and 谷艳娟. "Nanostructure of transition metal and metal oxide forelectrocatalysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37774396.
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Gu, Yanjuan. "Nanostructure of transition metal and metal oxide for electrocatalysis." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37774396.
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Cruickshank, Amy Clare. "Nanostructured Metal Electrodes for Wool Processing and Electroanalysis." Thesis, University of Canterbury. Chemistry, 2007. http://hdl.handle.net/10092/3853.
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The research presented in this thesis firstly concerns the use of electrochemical techniques to develop approaches to wool processing which have a lower impact on the environment than conventional chemical methods. Wool is a sulfur rich substrate and current methods used in wool processing often rely on sulfur-based reducing agents such as metabisulfite. However, due to increasing concern over the environmental impacts of metabisulfite, alternative methods are of interest. Electrochemical techniques have been applied to the process of wool setting in the presence of thiol setting agents. Wool disulfide bonds are reduced during this process and the thiol setting agent is converted to the disulfide. Efficient conversion of the disulfide back to the thiol setting agent would allow catalytic amounts of thiols to be used in wool setting. The electroreduction of cystine and 2-hydroxyethyl disulfide has been examined at a range of metal and carbon electrodes to find efficient methods of generating the corresponding thiols, cysteine and 2-mercaptoethanol respectively. Gold and silver were identified as the most efficient electrode materials. In industrial wool processing, the use of large-scale metal electrodes is expensive and therefore, high surface area gold and silver nanoparticle electrodes were fabricated by electrochemically depositing the metals onto low-cost carbon substrates. The most efficient electrochemical system for generating the thiol setting agent involved the electroreduction of cystine at the gold nanoparticle electrode and this system was used to successfully demonstrate that wool setting can be achieved using relatively low concentrations of cysteine. Further research was carried out to investigate methods for the controlled preparation of metal nanoparticle electrodes and their utility for detecting hydrogen peroxide was examined. A simple and versatile approach for the preparation of tethered gold nanoparticle assemblies was developed by exploiting electrostatic interactions between citrate-capped gold nanoparticles and amine tether layers attached to carbon surfaces. The nanoparticle assemblies were optimised for the detection of hydrogen peroxide by selecting the size and density of electrostatically assembled nanoparticles. The number of amine functionalities on the surface and the assembly conditions controlled the nanoparticle density. Nanostructured palladium electrodes fabricated using vapour deposition methods to immobilise palladium nanoparticles directly onto carbon substrates were also examined for the electroanalysis of hydrogen peroxide.
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Alwhshe, Brnyia Omar Salem. "Synthesis and applications of nanostructured metal oxide films." Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/65099/.
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Chao, Michelle (Michelle L. ). "Hydrophobic nanostructured glass surfaces using metal dewetting process." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111342.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (page 18).
This project aims to create a hydrophobic surface through a top down fabrication process of a nanostructure surface on a glass surface. The nanostructure is created through reactive ion etching utilizing silver as a mask. The silver mask is the result of a solid state thermal dewetting process which is controlled by varying the temperature and time of the process. Using this fabrication process, contact angles up to 137 degrees was achieved. Further surface modification resulted in contact angles exceeding 150 degrees. Superhydrophobic surfaces were made with the addition of a secondary roughness feature and the a PDMS coating.
by Michelle Chao.
S.B.
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Murata, Yusuke. "Synthesis, Characterization and Application of Nanostructured Metal Oxides." Kyoto University, 2004. http://hdl.handle.net/2433/147421.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第10975号
エネ博第86号
新制||エネ||24(附属図書館)
UT51-2004-G822
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 足立 基齊, 教授 尾形 幸生, 教授 片桐 晃
学位規則第4条第1項該当
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Wang, John S. "Pseudocapacitive effects in nanostructured transition metal oxide materials." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1680034181&sid=11&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Ca, Diep Vu. "NANOSTRUCTURED ASSEMBLIES FOR SOLID PHASE EXTRACTION OF METAL IONS." Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1107552000.
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Pavasupree, Sorapong. "New aspects of nanostructured metal oxides as energy materials." Kyoto University, 2006. http://hdl.handle.net/2433/143794.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第12420号
エネ博第127号
新制||エネ||32(附属図書館)
24256
UT51-2006-J411
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 吉川 暹, 教授 八尾 健, 教授 萩原 理加
学位規則第4条第1項該当
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Zhou, Lite. "Novel Nanostructured Metal Oxides for Efficient Solar Energy Conversion." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/510.
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Metal oxide materials could offer earth-abundant, non-toxic alternatives to existing lightabsorber materials in thin-film photovoltaic and photoelectrochemical cells. However, efficiency of these devices based on existing metal oxides is typically low due to poor material properties. In this research, novel Sb:SnO2 nanorod and nanotube electron collectors have been synthesized, investigated and were used to improve the photo-conversion efficiency of top-performing BiVO4 photoelectrochemical cell. The performance of Sb:SnO2/BiVO4 photoanode achieved a new record for the product of light absorption and charge separation efficiencies (ηabs × ηsep) of ~ 57.3% and 58.5% under front- and back-side illumination at 0.6 VRHE and Sb:SnO2/BiVO4 PV cell achieved 1.22% solar power conversion efficiency. In addition, a new promising metal oxide material (CuBiW2O8) has been synthesized and its optoelectronic properties have been investigated to make photovoltaic cell which has potential to achieve over 30% solar power conversion efficiency.
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MAGAGNA, STEFANO. "Thermoelectric nanostructured silicon obtained by Metal-assisted Chemical Etching." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/312087.
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Il mio progetto di tesi prevede la preparazione di materiali a base di nanofili di silicio, sfruttando una via sintetica in soluzione: il Metal-assisted Chemical Etching (MaCE). La tecnica prevede l’immersione del substrato monoscristallino <100> di Silicio in una soluzione di acido fluoridrico, contenente una sorgente di ioni Ag+ (AgNO3). Il processo consiste sostanzialmente nell’ossidazione localizzata del Silicio, catalizzata dagli ioni Ag+; l’ossido di Silicio così formato viene successivamente disciolto dal HF presente in soluzione, permettendo la formazione di nanofili per etching chimico. Nonostante il MaCE sia una tecnica diffusamente utilizzata a livello sperimentale, l’effettivo meccanismo del processo è ancora fortemente dibattuto in letteratura. Grazie al mio periodo a Marsiglia, ho potuto caratterizzare a fondo dal punto di vista morfologico i vari nanofili ottenuti da substrati a diverse concentrazioni di drogante, diverse specie droganti. E’ stata, inoltre, variata sistematicamente la temperatura di attacco, nonché la concentrazione di Ag+ all’interno della soluzione. I risultati ottenuti grazie ad una avanzata analisi morfologica con SEM (Scanning Electron Microscopy) e TEM (Transmission Electron Microscopy) hanno permesso di aprire una riflessione e avanzare teoria su diversi aspetti dell’etching, dal trasferimento elettronico alla localizzazione dell’attacco.
La versatilità del MaCE permette la sintesi di un metamateriale, introdotto nel 2014 da Davis et al, costituito da una membrana di Silicio sulla quale è posto un array di nanofili di Silicio e definito “Nanophononic Metamaterial (NPM)”. L’interazione tra i modi fononici introdotti dai nanofili all’interno del film e i modi del film stesso porterebbe il NPM ad una conducibilità termica del 48%, rispetto a quella del corrispettivo film sottile senza nanopillars, grazie una ibridizzazione delle curve di dispersione fononica e la comparsa di modi fononici piatti e localmente risonanti. Inoltre, visto che il trasporto elettronico avviene nella membrana che rimane priva di difetti o inclusioni, le proprietà elettroniche del NPM risultano conservate, rendendolo ideale per applicazioni termoelettriche vista la bassa conducibilità termica risultante. NPM con diversi spessori di membrana sono stati prodotti partendo da un wafer Double-Side-Polished di 200 micron di spessore, sul quale sono stati prodotti i nanofili tramite MaCE, su entrambe le facce. Scegliendo la lunghezza dei nanofili è stato possibile regolare lo spessore della membrana residua. Le caratterizzazioni elettriche e termoelettriche hanno dimostrato come il comparto elettronico del NPM sia mantenuto. La caratterizzazione termica di una membrana con spessore di 62 micron ha ottenuto una conducibilità termica pari al 36% di quella del Silicio bulk. Questo materiale, quindi, permette di disaccoppiare la conducibilità elettrica (regolata dalle caratteristiche della membrana) dalla conducibilità termica (controllata dalla presenza dei nanofili), rendendolo ideale per applicazioni termoelettriche.The necessity of sustainability in energy production and the continuous increasing of global warming, which leads to tremendous consequences, are among the most complicated challenges facedby humanity along its history. Reduction of the energy wastes anda strong energetic efficiency improvement are the most relevant solutions proposed, since nearly the 60 % of the energy generated around the world is wasted as heat. The possibility to recover even a small amount of this wasted energy could lead to a significant decrease of CO2 emission. Thermoelectric devices can actively contribute to this cause sincethey allow to generate electrical power even with small temperature gradients and without moving parts. Their efficiency is described by the figure of merit zT. Therefore, an ideal thermoelectric material should have, at the same time,good electrical properties combined to a low thermal conductivity ,a difficult challenge considering that, normally, a good electrical conductor is also a good thermal conductor. However, property modification at nanoscale opened a new pathway in thermoelectric materials research. The work of this PhD thesis is focused on the nanostructuration of a non-toxic, earth-abundant material such as Silicon. Due to the high thermal conductivity, bulk silicon is not suitable for thermoelectric application. Anyway, nanostructuration offers efficient and innovative ways to lower silicon thermal conductivity and to open novel opportunities to its usage as thermoelectric material. In the first part, the mechanism of Silver-assisted Chemical etching (SaCE), a one-step method chosen for the production of silicon NW will be presented. Particularly, the results of anextended analysis of the interplay among doping level and type of silicon, nanowire morphology and the parameters controlling thechemistry of SaCE will be shown. SaCE occurs at the outer substrate surface as a result of Si extrusion by sinking self-propelled Ag particles which causes Si flakes to be exposed at the outer solution-substrate. Here, the etching actually occurs through either 2- or 4-electron electrochemical oxidation of Si. NW surface is found to be either porous (potholed) or crystalline depending on the predominant electrochemical process. The prevalence of either 2- or4-electron processes is controlled by the material resistivity andtherefore by the voltage sensed by silicon. Two-electron processes occur at low voltages for conductive, heavily doped Si,and causes the formation of superficially potholed NWs. Four-electron processes occur for weakly doped Si and lead to fully crystalline NWs.Secondly, the production, by means of SaCE, and the characterization of a recently introduced category of material, the so-called Nanophononic Metamaterial (NPM), will be presented. This material is composed by an array of silicon nanopillars on top of a silicon thin film. The hybridization of the locally-resonant phonon modes introduced by the NWs with membrane phonon modes leads to a thermal conductivity reduction. NPM demonstrates to retain electrical and thermal conductivity of the wafer from which it is etched. Preliminary thermal measurements showed a thermal conductivity reduction of 2/3 with respect of bulk silicon. In the third part, the characterization of heavily doped Si NWs arrays, produced by SaCE, will be presented. This kind of arrays shows very low thermal conductivity (around 2 W/ (m K)) and a Seebeck coefficient comparable with that of heavily doped bulk silicon. Anyway, due to the presence of the substrate (very thick if compared with NWs length), it is complicated to have a precise measurement of NW resistivity. To overcome this issue, a new structure exclusively made of NWs and free from any substrate contribution will be presented.
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Jain, Prashant K. "Plasmons in assembled metal nanostructures." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/28207.
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Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008.Committee Chair: El-Sayed, Mostafa A.; Committee Member: Lyon, L. Andrew; Committee Member: Sherrill, C. David; Committee Member: Wang, Zhong Lin; Committee Member: Whetten, Robert L.
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Cao, Shuai. "Nanostructured metal-organic frameworks and their amorphization, carbonization and applications." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707948.
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Ajayi, Olawale Adebimpe. "DC and RF Characterization of High Frequency ALD Enhanced Nanostructured Metal-Insulator-Metal Diodes." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5166.
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Metal-Insulator-Metal (MIM), Metal-Insulator-Insulator-Metal (MIIM), and Metal-Insulator-Insulator-Insulator-Metal (MIIIM) quantum tunneling diodes have been designed, fabricated, and characterized. The key interest of this work was to develop tunneling diodes capable of operating and detecting THz radiation up to 30THz, which is well beyond the operation ranges of other semiconductor-based diodes.
Al2O3, HfO2 and TiO2 metal oxides were employed for studying the behavior of metal-insulator-metal (MIM) and metal-insulator-insulator-metal (MIIM) quantum tunneling diodes. Specifically, ultra-thin films of these oxides with varied thicknesses were deposited by atomic layer deposition (ALD) as the tunneling junction material that is sandwiched between platinum (Pt) and titanium (Ti) electrodes, with dissimilar work functions of 5.3 eV and 4.1 eV, respectively.
Due to the unique and well-controlled tunneling characteristic of the ALD ultra-thin films, reproducible MIM and MIIM diode devices have been developed. The DC characteristics of MIM and MIIM tunneling junctions with different junction areas and materials were investigated in this work. The effects of the different compositions and thicknesses of the tunneling layer on the diodes were studied systematically. Through the introduction of stacked dual tunneling layers, it is demonstrated that the MIIM and MIIIM diodes exhibited a high degree of asymmetry (large ratio between forward and reverse currents) and a strong nonlinearity in their I-V characteristics. The characterization was performed on diodes with micro and nano-scale junction areas.
The MIM diodes reported herein exhibited lower junction resistances than those reported by prior works. Moreover, a study was conducted to numerically extract the average barrier heights by fitting the analytical model of the tunneling current to the measured I-V responses, which were evaluated with respect to the thickness of the constituent tunneling layer. RF characterization was performed on the MIM diodes up to 65GHz, and its junction impedance was extracted. A rigorous procedure was followed to extract the diode equivalent circuit model to obtain the intrinsic lumped element model parameters of the MIM diodes.
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Chen, Jingyi. "Synthesis and utilization of metal nanostructures /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/11547.
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Kojima, Robert Wataru. "Nanostructured composites conducting polymers and metal salts and their applications /." Diss., Restricted to subscribing institutions, 2010. http://proquest.umi.com/pqdweb?did=2026906701&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Yi, Jue-Min. "Diffraction of single holes through planar and nanostructured metal films." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01018454.
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The theme of my thesis is to investigate the diffraction behavior of subwavelength holes in metal films, and to understand the surface plasmons' (SPs) role in aperture far-field diffraction. We have built a home-made goniometer setup with high-level quality. A series of single hole continuously ranging from k*r>>1 to k*r<
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Gonçalves, Alexandre Amormino Dos Santos. "Development of Nanostructured Ceramic Catalysts Based on Mixed Metal Oxides." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1543412496976455.
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Cibrev, Dejan. "Photoelectrocatalytic and photoelectrochromic properties of composite nanostructured metal oxide films." Doctoral thesis, Universidad de Alicante, 2019. http://hdl.handle.net/10045/99689.
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Los materiales llamados semiconductores (muchos de ellos óxidos metálicos) son capaces de generar portadores de carga (huecos y electrones) cuando se iluminan con luz suficientemente energética. Estos portadores son capaces de sostener reacciones redox. Los electrones de la banda de conducción (BC) y los huecos de la banda de valencia (BV) pueden reducir y oxidar, respectivamente, especies que estén en contacto directo con el semiconductor. Además, los electrones y huecos fotogenerados pueden eliminarse en el proceso que se conoce como recombinación. El grado en que se producen estas reacciones redox depende de la eficiencia en la separación de las cargas fotogeneradas. Una separación de los portadores efectiva da lugar a aplicaciones. En esta tesis se abordan detalladamente los procesos de foto(electro)cromismo y foto(electro)catálisis. La separación de los portadores de carga en un material puede verse favorecida por: - La creación de heterouniones entre dos semiconductores (óxidos) distintos. - El diseño adecuado de la nanoestructura de los óxidos: estructuras ordenadas y/o estructuras con mucha superficie interfacial. - La modificación de la superficie o del seno de los óxidos semiconductores (dopado). En las aplicaciones prácticas se pretende que haya una transferencia de carga capaz de impulsar el proceso de interés. Por lo tanto, el control de los procesos de transferencia de carga del semiconductor a través de sus interfases es fundamental en el diseño de materiales para una determinada aplicación. Teniendo todo esto en cuenta, los objetivos establecidos para esta tesis han sido: I. Preparar estructuras ordenadas de nanobarras de α-Fe2O3 (hematita) sobre vidrio conductor e investigar sus propiedades catalíticas para fotooxidar agua. Optimizar el proceso de fotooxidación del agua sobre electrodos de hematita aplicando un pretratamiento electroquímico. Estudiar el efecto del pretratamiento sobre la composición, morfología y estructura electrónica de la hematita. II. Modificar los electrodos de hematita con Ti de dos maneras distintas, una que afecte principalmente a todo el material y otra que afecte a la superficie de la hematita, con el fin de mejorar sus propiedades catalíticas para fotooxidar agua. Aplicar y estudiar el pretratamiento reductivo para los electrodos de hematita tras ser modificados con Ti. III. Modificar la superficie de las nanobarras de hematita con trimetilaluminio (TMA) mediante depósito de capa atómica (Atomic layer deposition - ALD) desde fase gas o por adsorción en fase líquida, con el fin de mejorar sus propiedades fotoelectroquímicas para oxidar agua. Investigar los cambios en las propiedades electrónicas y electroquímicas de los electrodos de hematita tras ser modificados. IV. Preparar electrodos nanoporosos de Ni(OH)2 sobre vidrio conductor (SnO2:F - FTO) e investigar sus propiedades catalíticas para oxidar agua en medio alcalino en función de la cantidad depositada y de la morfología del hidróxido. V. Preparar electrodos nanoporosos basados en capas mixtas TiO2/Ni(OH)2 sobre vidrio conductor e investigar la separación de carga en los mismos con el fin de estudiar su posible utilización en dispositivos fotoelectrocrómicos. Estudiar las cinéticas de los procesos de la coloración y decoloración a través de medidas (foto)(espectro)electroquímicas. Las siguientes cinco conclusiones generales resumen los resultados más importantes en relación con los cinco objetivos previamente mencionados. I. En este estudio se ha conseguido sintetizar barras de hematita nanoestructuradas y con orientación (110) depositadas sobre vidrio conductor a través de un método de baño químico. Estas capas se han utilizado para estudiar el proceso de fotoxidación del agua. Para mejorar las propiedades fotocatalíticas de estas capas se ha empleado un pretratamiento electroquímico simple y altamente controlable que consiste en la aplicación de potenciales negativos por un tiempo muy corto (en el rango de segundos). Este pretratamiento da lugar a una mejora de la fotocorriente de hasta ocho veces asociada a la oxidación del agua, junto con un desplazamiento negativo de 20 mV del potencial de inicio de la fotocorriente. Este pretratamiento también induce cambios en la morfología de los electrodos, capacidad electrocatalítica y en su estructura electrónica. Por lo tanto, el dopado electroquímico no puede considerarse simplemente como un dopado tipo-n capaz de aumentar la fotoactividad de las capas debido a una mejora en el transporte de electrones. En realidad, los resultados obtenidos muestran claramente que se producen cambios mucho más profundos en la estructura electrónica y la composición de las capas que mejoran significativamente las propiedades tanto electro- como foto-electrocatalíticas. De hecho, ambas propiedades siguen una tendencia general similar con el potencial del pretratamiento empleado. Dentro de un marco más general, el pretratamiento reductivo puede ser utilizado también para la mejora de estructuras de hematita previamente modificadas o dopadas. Desde una perspectiva práctica, el dopaje electroquímico tiene la limitación de no ser permanente, lo que significa que debe aplicarse periódicamente. Esto no es un inconveniente serio en un dispositivo práctico, siempre y cuando la mejora inducida por el pretratamiento compense claramente esta limitación. II. Se han diseñado dos estrategias de modificación de hematita económicas utilizando una disolución con un mismo precursor de Ti. En un procedimiento el Ti se introduce en la estructura de hematita, mientras que en la otra, se forma una capa de TiO2 ultra-delgada que cubre por completo la superficie de hematita. Ambas modificaciones inducen un aumento significativo en la fotocorriente para la oxidación de agua (4 - 6 veces). La razón principal de la mejora en las capas modificadas con Ti es la disminución significativa del proceso de recombinación. El freno de la recombinación en las muestras modificadas con una sobre-capa de TiO2 se atribuye principalmente al bloqueo de estados superficiales, mientras que en el caso de las muestras modificadas con Ti intercalado en la estructura se relaciona principalmente con el aumento del área interfacial junto con un aumento de la conductividad electrónica. III. Se han preparado electrodos basados en nanobarras de hematita modificadas con TMA empleando una estrategia simple de impregnación a partir de una disolución de hexano. Los resultados se han comparado con los obtenidos modificando los electrodos de hematita con TMA por ALD. Los electrodos modificados muestran una importante mejora, aumentando tres veces la fotocorriente de oxidación de agua. Por un lado, el TMA bloquea los estados superficiales de hematita y por otro, induce un enriquecimiento electrónico. Tal conclusión fue confirmada cualitativamente en el caso de muestras modificadas con TMA utilizando la técnica de ALD. A pesar de que la modificación en fase líquida ha dado una foto-actividad menor en términos de la magnitud de la fotocorriente que la de ALD, representa una alternativa mucho más económica. Además, el método de impregnación a partir de una disolución es industrialmente escalable. Dentro de un marco más general, la modificación con TMA es potencialmente aplicable a otros semiconductores tipo n. Por lo tanto, podría constituir una estrategia relevante para mejorar la eficiencia de la fotooxidación de agua utilizando otros materiales tales como TiO2, BiVO4, WO3, entre otros. IV. Este estudio muestra que, a través de un procedimiento simple y potencialmente escalable como el baño químico, se pueden producir capas nanoestructuradas ultra-finas de Ni(OH)2 sobre FTO. Estas películas se caracterizan por una gran actividad electrocatalítica. Son capaces de oxidar el agua desarrollando corrientes iguales o superiores a las de películas mucho más gruesas. Esto último está relacionado con el hecho de que la reacción de generación de oxígeno depende de la formación de níquel (IV) que puede verse limitada por la baja conductividad eléctrica de Ni(OH)2. Por tanto, el proceso se favorece en capas finas donde la distancia al substrato conductor es menor. Esta noción es muy importante de cara a su aplicación. No solo se minimiza la cantidad de Ni(OH)2 necesaria sino se producen también ánodos altamente eficientes transparentes y prácticamente incoloros. V. Este trabajo ha mostrado que una capa nanoporosa mixta y delgada de TiO2/Ni(OH)2 depositada sobre vidrio conductor y sometida a un potencial catódico constante puede colorearse al ser iluminada con luz ultravioleta, mientras que se decolora completamente cuando se interrumpe la iluminación. Este fenómeno se ha denominado “fotoelectrocromismo reversible potenciostatico”. El valor del potencial empleado permite seleccionar tanto el contraste en la coloración como la cinética de la decoloración. Este fenómeno es posible debido a la existencia de un área interfacial extendida de contacto TiO2/Ni(OH)2 debido a la estructura nanoporosa que permite un contacto íntimo entre ambos componentes. Desde un punto de vista práctico, estos resultados podrían facilitar el desarrollo de ventanas inteligentes con una nueva funcionalidad porque, además del convencional efecto electrocrómico, trabajarían en un segundo modo, en el que, la coloración respondería a la intensidad de la luz incidente (a un potencial constante).
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Lam, Koon Fung. "Selective adsorption of metal ions by chemically-modified MCM-41 /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?EVNG%202006%20LAM.
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Bansal, Shubhra. "Characterization of Nanostructured Metals and Metal Nanowires for Ultra-High Density Chip-to-Package Interconnections." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14041.
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Nanocrystalline materials are being explored as potential off-chip interconnects materials for next generation microelectronics packaging. Mechanical behavior and deformation mechanisms in nanocrystalline copper and nickel have been explored. Nanostructured copper interconnections exhibit better fatigue life as compared to microcrystalline copper interconnects at a pitch of 100 and #956;m and lower. Nanocrystalline copper is quite stable upto 100 oC whereas nickel is stable even up to 400 oC. Grain boundary (GB) diffusion along with grain rotation and coalescence has been identified as the grain growth mechanism. Ultimate tensile and yield strength of nanocrystalline (nc) Cu and Ni are atleast 5 times higher than microcrystalline counterparts. Considerable amount of plastic deformation has been observed and the fracture is ductile in nature. Fracture surfaces show dimples much larger than grain size and stretching between dimples indicates localized plastic deformation. Activation energies for creep are close to GB diffusion activation energies indicating GB diffusion creep. Creep rupture at 45o to the loading axis and fracture surface shows lot of voiding and ductile kind of fracture. Grain rotation and coalescence along direction of maximum resolved shear stress plays an important role during creep. Grain refinement enhances the endurance limit and hence high cycle fatigue life. However, a deteriorating effect of grain refinement has been observed on low cycle fatigue life. This is because of the ease of crack initiation in nanomaterials. Persistent slip bands (PSBs) at an angle of 45o to loading axis are observed at higher strain ranges (> 1% for nc- Cu) with a width of about 50 nm. No relationship has been observed between PSBs and crack initiation. A non-recrystallization annealing treatment, 100 oC/ 2 hrs for nc- Cu and 250 oC/ 2 hrs for nc- Ni has been shown to improve the LCF life without lowering the strength much. Fatigue crack growth resistance is higher in nc- Cu and Ni compared to their microcrystalline counterparts. This is due to crack deflection at GBs leading to a tortuous crack path. Nanomaterials exhibit higher threshold stress intensity factors and effective threshold stress intensity is proportional to the elastic modulus of the material.
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Mott, Derrick M. "Synthesis, characterization, and catalysis of metal nanoparticles." Diss., Online access via UMI:, 2008.
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Masson, Sian Esther. "The detection of VOCs using sensors based on nanostructured metal oxides." Thesis, Bangor University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443647.
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Marwan, Jan. "The electrodeposition and electrochemical properties of nanostructured (Hâ‚-e) metal films." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252369.
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Figueras, Valls Marc. "Nanostructured transition metal carbides as potential catalysts for greenhouse gases conversion." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673020.
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Over the recent decades, several studies revealed the precarious climate situation which is threatening all Life forms on earth, including mankind, even if sometimes we tend to ignore the actual fragility of our situation. Ironically, the human species is at the origin of the rapid change on climate, mostly by practicing unsustainable activities, such as the unregulated consumption of fossil fuels, excessive deforestation, extensive agriculture, and intensive livestock. All these practices have increased the concentration of greenhouse gases in the atmosphere, producing a rapid increase in the average Earth temperature with noticeable consequences in our lifetime. Nevertheless, several efforts have been conducted by the scientific community in order to revert the actual climate situation, even if society acts delayed.
One of the actual work routes implies the use of catalysts to capture and convert greenhouse gases into less harmful and more useful chemicals. This route has found in transition metal carbides (TMCs) proficient candidates that could have an important impact in the aforementioned matter. An interesting aspect of TMCs is their capacity to catalyse such transformation reactions at low temperatures and to withstand several reaction cycles without degrading. Precisely, the present Thesis unveils and discusses several reaction mechanisms involved in the greenhouse gases transformation reactions held by TMCs, particularly, focusing on MoCy nanoparticles, a largely unexplored field. This Thesis combines experimental and theoretical approaches to explain the observed experimental evidences, where custom synthetized MoC nanoparticle supported on Au(111) are able to activate methane at room temperature, hydrogenate CO2, and act as superior H2 sponges with respect to clean MoC extended surfaces. Moreover, other important findings are revealed, such as the reconstruction held by some transition metal carbides and nitrides surfaces and the intrinsic nature of clean MoC nanoparticles towards hydrogenation reactions. Overall, the present dissertation intends to encourage further efforts on developing TMC based catalyst able to be used at industrial levels.
The experimental section of this thesis has been carried out at the Brookhaven National Laboratory by the group of Prof. J. A. Rodriguez, while the computational part and results analysis has been carried out in the present institution, the Universitat de Barcelona. The results obtained have led to several joint publications.En els darreres dècades, diversos estudis han revelat la precària situació climàtica que està amenaçant totes les formes de vida a la terra, inclosa la humanitat, encara que de vegades tendim a ignorar la fragilitat de la nostra situació. Irònicament, l’espècie humana és l’origen del ràpid canvi climàtic, principalment per practicar activitats insostenibles, com el consum no regulat de combustibles fòssils, la desforestació excessiva, l’agricultura extensiva i la ramaderia intensiva. Totes aquestes pràctiques han augmentat la concentració de gasos d’efecte hivernacle a l’atmosfera, produint un ràpid augment de la temperatura mitjana de la Terra amb conseqüències notables fins i tot durant la nostra vida. No obstant això, la comunitat científica està realitzant diversos esforços per revertir la alarmant situació climàtica, fins i tot si la societat actua amb retard. Una de les rutes de treball implica l’ús de catalitzadors per capturar i convertir els gasos d’efecte hivernacle en productes químics menys nocius i més útils. Aquesta ruta ha trobat en els carburs de metalls de transició (TMC) candidats competents que podrien tenir un impacte important en la reactivitat esmentada. L’aspecte més interessant dels TMCs és la seva capacitat per catalitzar aquestes reaccions de transformació a baixes temperatures i per suportar diversos cicles de reacció sense degradar-se. Precisament, aquesta Tesi revela i analitza diversos mecanismes de reacció implicats en les reaccions de transformació dels gasos d’efecte hivernacle catalitzades pels TMC, concretament, centrant-se en les nanopartícules de MoCy, que encara romanen inexplorades. Aquesta tesi combina enfocaments experimentals i teòrics per explicar les evidències experimentals observades, on les nanopartícules de MoC sintetitzades suportades sobre Au (111) són capaces d’activar el metà a temperatura ambient, hidrogenar CO2 i actuar com a esponges H2 superiors respecte a les superfícies netes de MoC. A més, altres descobriments importants han estat revelats, com ara la reconstrucció d’algunes superfícies de TMC/TMN i la naturalesa química intrínseca de les nanopartícules de MoC netes pel que fa a les reaccions d’hidrogenació. En general, la present dissertació té la intenció de fomentar nous esforços en el desenvolupament de catalitzadors basats en TMCs que puguin ser utilitzats a nivell industrial. La secció experimental d’aquesta tesi s’ha dut a terme al Brookhaven National Laboratory pel grup del professor J. A. Rodriguez, mentre que la part computacional i l’anàlisi de resultats s’ha dut a terme a la present institució, la Universitat de Barcelona. Els resultats obtinguts han donat lloc a diverses publicacions conjuntes.
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Gcilitshana, Oko Unathi. "Supercapacitor electrode materials based on nanostructured conducting polymers and metal oxides." Thesis, University of the Western Cape, 2013. http://hdl.handle.net/11394/3532.
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Kitiyanan, Athapol. "Dye-sensitized solar cell using nanostructured TiO2-based binary metal oxides." Kyoto University, 2006. http://hdl.handle.net/2433/143796.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第12422号
エネ博第129号
新制||エネ||32(附属図書館)
24258
UT51-2006-J413
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 吉川 暹, 教授 八尾 健, 教授 萩原 理加
学位規則第4条第1項該当
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Oloye, Olawale. "Design and engineering of nanostructured liquid metal composites for catalytic applications." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/227405/1/Olawale_Oloye_Thesis.pdf.
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This thesis concentrated on the study of the room temperature liquid metal, gallium and its eutectics. The application of liquid metal-based alloys to new areas of catalysis was extended by encompassing energy and environmental applications. A significant advancement in the potential application of liquid metal-based alloys in electrocatalysis, photocatalysis and sonocatalysis has resulted from this research. Significantly, research conducted on carbon dioxide capture/conversion to metal carbonates during this graduate study is currently being explored for industrial waste management.
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Sayeed, Md Abu. "Electrochemical fabrication of nanostructured metal oxides for the oxygen evolution reaction." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/116769/1/Md%20Abu_Sayeed_Thesis.pdf.
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This research developed a new approach to synthesise novel catalysts for electrochemical water splitting. Hydrogen and oxygen production from water mostly depends upon the performance of the water-splitting catalyst, in particular for the oxygen evolution reaction which is the focus of this thesis. The ability to efficiently produce oxygen and hydrogen from water will result in a chemical means to store intermittent renewable energy for later use. In this thesis, a room temperature electrochemical synthesis approach under ambient conditions is presented to produce highly active catalyst materials that is highly beneficial for the difficult oxygen evolution half reaction.
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Sibanyoni, Johannes Mlandu. "Nanostructured light weight hydrogen storage materials." University of the Western Cape, 2012. http://hdl.handle.net/11394/4631.
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Philosophiae Doctor - PhDThe main objective of this study was to advance kinetic performances of formation and decomposition of magnesium hydride by design strategies which include high energy ball milling in hydrogen (HRBM), in combination with the introduction of catalytic/dopant additives. In this regard, the transformation of Mg → MgH2 by high energy reactive ball milling in hydrogen atmosphere (HRBM) of Mg with various additives to yield nanostructured composite hydrogen storage materials was studied using in situ pressure-temperature monitoring that allowed to get time-resolved results about hydrogenation behaviour during HRBM. The as-prepared and re-hydrogenated nanocomposites were characterized using XRD, high-resolution SEM and TEM, as well as measurements of the mean particle size. Dehydrogenation performances of the nanocomposites were studied by DSC / TGA and TDS; and the re-hydrogenation behaviour was investigated using Sieverts volumetric technique.
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Cho, Joungmo. "Computational studies of reacting flows with applications in nanoscale materials synthesis." Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/dissertations/AAI3372259/.
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Zheng, Jie. "Fluorescent noble metal nanoclusters." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-04182005-161511/.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2005.Wang, Zhong Lin, Committee Member ; Whetten, Robert L., Committee Member ; El-Sayed, Mostafa A., Committee Member ; Dickson, Robert M., Committee Chair ; Lyon, Andrew L., Committee Member.
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Arbiol, i. Cobos Jordi. "Metal Additive Distribution in TiO2 and SnO2 Semiconductor Gas Sensor Nanostructured Materials." Doctoral thesis, Universitat de Barcelona, 2001. http://hdl.handle.net/10803/1503.
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Recently, there has been an increasing interest in the electronics world for those aspects related to semiconducting gas sensor (SGS) materials. In view of the increasingly strict legal limits for pollutant gas emissions, there is a great interest in developing high performance gas sensors for applications such as controlling air pollution and exhaust gases. In this way, semiconductor gas sensors offer good advantages with respect to other gas sensor devices (such as spectroscopic and optic systems), due to their simple implementation, low cost and good reliability for real-time control systems. In the present work, we have been especially interested in the study of the different ways of metal additive distribution in the most common SGS materials used nowadays and furthermore in the physical and chemical sensing properties they can achieve.
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Gràcia, Lanas Sara Isabel. "Fluoride and metal ions removal from water by adsorption on nanostructured materials." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/403774.
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Actualmente la contaminación ambiental es un gran enemigo global, siendo uno de los problemas que afectan más al mundo. El presente trabajo se centra en la eliminación de contaminantes acuosos, como el fluoruro o distintos iones metálicos. Diversos materiales nanoestructurados han sido utilizados para la adsorción de los contaminantes de agua anteriormente mencionados. Estos materiales han sido elegidos por la elevada area superficial que ofrecen en un volumen muy pequeño, rendiendolos materiales adsorbentes ideales para el tratamiento de aguas residuales.
La primera parte de la tesis se centra en la eliminación de fluoruro del agua. Se ha seleccionado como material óptimo las microesferas jerárquicas de alúmina (HAM), por su elevada area superficial y su porosidad, así como su estabilidad. HAM han sido sintetizadas mediante la metodología publicada con cambios significativos, y posteriormente caracterizadas con SEM, TEM, XRD, DLS o BET.
Se han elaborado estudios potenciométricos para la determinación de fluoruro restante en solución. Los resultados expeimentales obtenidos, se han ajustado con el modelo de Langmuir y Freundlich para describir el mecanismo de adsorción. Datos precisos en la entalpía de adsorción permiten el diseño de las mejores condiciones tanto para la captación como para una eventual liberación de una determinada especie química. En trabajos previos, la entalpía asociada a la adsorción de fluoruro (∆Hads) ha sido calculada mediante la ecuación de van’t Hoff. Sin embargo, distintos estudios consideran las discrepancias entre la entalpía obtenida directamente (ITC) y la obtenida mediante la ecuación de van’t Hoff, y evidencian la gran incertidumbre asociada al último método. En este trabajo, ITC ha sido usada por primera vez para la directa determinación de ∆Hads para la adsorción de fluoruro en HAM, proporcionando parámetros termodinámicos más robustos e indepedientes.
La segunda parte de la tesis se centra en la eliminación de metales pesados y preciosos del agua. En esta ocasion, se ha elegido como adsorbente nanopartículas de magnetita (SPION). Los materiales adsorbentes magnéticos (como SPION), pueden representar una herramienta interesante para la eliminación/recuperación de iones metálicos del agua, ya que pueden dispersarse en la muestra y recuperarse fácilmente usando un campo magnético. Sin embargo, para la adsorción de iones metálicos, el SPION no modificado presenta una pequeña capacidad de adsorción. No obstante, una de las ventajas que presenta éste material és que es fácilmente modificable añadiendo un ligando orgánico a la superficie. Siguendo la teoria de HSAB, ligandos con grupos funcionales como –SH o –RSR- han sido seleccionados.
El objetivo de este estudio es sintetizar SPION y funcionalizarlos con ligandos continentes de S en sus grupos funcionales para la adsorción selectiva de metales pesados y preciosos, caracterizando los procesos de adsorción en términos de capacidad de carga y parámetros termodinámicos.
SPION se han sintetizado y funcionalizado con ácido 3-mercaptopropiónico y ácido 3,3’- tiodipropionico siguiendo el procedimiento publicado en la literatura y luego caracterizado por métodos estándar. Mientras que el proceso de adsorción de cada metal ha sido estudiado utilizando una nueva metodología que combina ICP y ITC. Mientras que en trabajos anteriores se han calculado las ΔHads relacionadas con la adsorción de metales mediante la ecuación de van't Hoff, en este trabajo ITC se aplica por primera para la determinación directa de ΔHads. En nuestro método, los datos obtenidos por ICP-OES han sido equipados con una isoterma de Langmuir para obtener el valor de la constante de adsorción (Kads). A continuación, se ha utilizado Kads para calcular la concentración de metal libre para cada adición de valorante en las titulaciones calorimétricas y finalmente obtener el valor de ΔHads. Además, el ITC se aplica también como un cribado del material adsorbente, con el fin de discriminar el candidato óptimo para aplicaciones de extracción/recuperación de metal.Nowadays the environmental pollution is a great global enemy, being one of the problems that most affect the whole world. This PhD thesis focuses on the elimination of certain aqueous contaminants, such as fluoride or different metal ions. Nanostructured materials have been applied as innovative adsorption method to remove the aforementioned pollutants. These materials present a high surface area in a very small volume, being ideal materials for the treatment of wastewater. The first chapter of the thesis focuses on the removal of fluoride from contaminated water. Hierarchical alumina microspheres (HAM) have been selected as the optimum material, due to their high surface area and porosity, as well as the stability of the material. HAM have been synthesized using the published methodology with significant modifications, and have subsequently been fully characterized with techniques such as SEM, TEM, XRD, DLS or BET. Potentiometric studies have been performed to determine the fluoride remaining in solution. The obtained results have been adjusted with the Langmuir and Freundlich model to describe the adsorption mechanism. Accurate data on the enthalpy associated to the adsorption process allow the design of the best conditions both for the uptake and for the eventual successive release of a given chemical species. In previous works, the enthalpy associated to fluoride adsorption (∆Hads) has been calculated by the van’t Hoff equation. However, many studies considered the discrepancies between enthalpy obtained directly (ITC) and from van’t Hoff equation and evidenced the large uncertainties associated to the latter method. In this work, ITC is applied for the first time to obtain direct determination of ∆Hads for fluoride ion adsorption by HAM to provide independent and more robust thermodynamic parameters. The second part of the thesis focuses on the removal of heavy and precious metals from contaminated water. In this case, magnetic nanoparticles (SPION, Super Paramagentic Iron Oxide Nanoparticles) have been chosen as adsorbent. Magnetic materials may represent an interesting tool for the removal/recovery of metal ions from aqueous media, as they can be dispersed in the sample and easily recovered by using a magnetic field. However, for the adsorption of metal ions, the unmodified SPION has been demonstrated to have a small adsorption capacity. One of the advantages of this material is that its surface is easily modifiable by adding an organic ligand. Therefore, following the HSAB theory, ligands with functional groups such as -SH or -RSR- have been selected for SPION modification. The aim of this study is to synthesize and functionalize SPION with sulphur containing groups for the selective removal of heavy metals and for the recovery of precious metals from water, characterizing the adsorption processes in terms of loading capacity and thermodynamic parameters. SPION have been synthesized and functionalized with 3-mercaptopropionic acid (3-MPA) following the procedure published in the literature and then characterized by SEM, TEM, BET, FT-IR, XRD and TGA, while the metal adsorption process has been studied using a new methodology, which combines ICP and ITC. While in previous works ΔHads (adsorption enthalpy) related to metal adsorption have been calculated by the van’t Hoff equation, ITC is applied for the first time for the direct determination of ΔHads. Data obtained by ICP have been fitted with a Langmuir isotherm to obtain the value of the adsorption constant (Kads). Then, the Kads has been used to calculate the free metal concentration for each titrant addition in the calorimetric titrations in order to fit the experimental heat and ultimately obtain the ΔHads value for the metal adsorption. Moreover, ITC is also applied as a screening of the adsorbent material, in order to discriminate the optimal candidate for metal removal/recovery applications.
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Pruna, Morales Raquel. "Transparent nanostructured metal oxides for chemical biosensors: towards point-of-care environments." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/667646.
Full textAbstract:
There is an increasing need for developing innovative, versatile and low-cost point-of-care (POC) systems capable of screening for at early stages of development. POC systems usually consist of a biosensor part integrated in an electronic circuit and eventually a microfluidic system to manage the body fluid samples. The aim of this doctoral thesis is to investigate several ways of improving POC technology.
On the one hand, biosensors currently integrated into POC systems have limitations. A wide variety of important analytes cannot be properly detected and quantified, and methods supported by a powerful electronic systems that supply the necessary energy to trigger a measurable event that can be monitored are required. For this, adequate sensing substrates are required that allow the coupling of analytes and other biomolecules and enable the detection of chemical reactions occurring at their surfaces. Besides, the complex electronic circuitry capable of simultaneously exciting the sensor and monitoring its response must be redesigned into a low-cost and miniaturized format to be integrated into POC systems.
Electrochemical and optical biosensors have become relevant in point-of-care technology due to the versatility of POC systems based on such transducing principles, which provide the sensors with high sensitivities and specificities. In particular, sensitivity may become badly affected by the miniaturization of sensors and devices. Thus, the need for reducing the surface of sensing electrodes and yet maintaining the sensitivity has boosted the research and development of nanostructured surfaces. The high surface-to- volume ratio (SVR) presented by nanostructures makes them extremely interesting for the detection of biomolecules, since an increase of surface enables the interaction with a big amount of small-sized molecules and this implies an increase of sensitivity and the possibility to reduce the sensor size. In this thesis, nanostructured indium tin oxide (ITO) is proposed as working electrode (WE) for electrochemical biosensors.
The first part of this thesis consists in a study of ITO properties and its electrical, optical, electrochemical and structural characterization both as a thin film and as nanostructured electrodes prepared by electron beam evaporation onto silicon and glass substrates. Moreover, the interaction of nanostructured ITO with some molecules known as crosslinkers, which allow subsequent functionalization of surfaces with biomolecules, has also been studied in the frame of this thesis. Finally, several immunoassays were performed using nanostructured ITO as substrate, with special attention to the detection of several concentrations of tumour necrosis factor α (TNF-α).
On the other hand, several electrochemical sensor mechanisms were studied. These were based upon different ways of electrically attacking the sensor and processing its response, and included potentiometry, amperometry and electrochemical impedance spectroscopy. A low-cost and miniaturized device implementing electrochemical impedance spectroscopy measurements was designed and developed for the detection of several concentrations of TNF–α biomarker with an array of eight parallel gold-based microelectrodes. Besides, we also designed the electronics for performing two-electrode amperometry and potentiometry. The latter was tested on nanostructured ITO electrodes covered with a doped conducting polymer, which was sensitive to pH changes in aqueous media.
To synthesize, this thesis gathers several proposals for improving current POC systems, regarding both the biosensor and the electronic parts, employing an important biomarker in the biomedical area for the measurements and proofs of concept, and being such approaches extensible to the environmental field.Existe una creciente necesidad de desarrollar sistemas de punto de cuidado (POC) innovadores, versátiles y de bajo coste, capaces de detectar enfermedades en estadios de desarrollo tempranos. Un sistema POC consiste en un biosensor integrado en un sistema electrónico y eventualmente un sistema microfluídico que gestione las muestras de fluidos biológicos. El objetivo general de esta tesis es investigar distintas posibilidades de mejorar la tecnología POC. Los sistemas biosensores actualmente integrados en sistemas POC son limitados, y requieren de métodos que se apoyen en un potente sistema electrónico. Para esto, se requiere por un lado de sustratos adecuados que permitan tanto el acoplo de biomoléculas como la detección de reacciones químicas ocurridas en su superficie; por otro lado, es necesaria una potente circuitería electrónica que pueda ser miniaturizada y de bajo consumo. Los biosensores electroquímicos y ópticos han tomado mucha relevancia en sistemas POC debido a su alta sensibilidad y especificidad, aunque éstas pueden verse gravemente afectadas por la miniaturización de los dispositivos. Por ello, la elevada relación superficie-volumen que presentan las nanoestructuras las hace especialmente interesantes para biodetección. En esta tesis, se propone el óxido de indio dopado con estaño (ITO) nanoestructurado como material de electrodo de trabajo en biosensores electroquímicos. En la primera parte de esta tesis se han estudiado las propiedades del ITO, y se ha caracterizado eléctrica, óptica, electroquímica y estructuralmente, a partir de muestras preparadas sobre silicio y sobre vidrio mediante evaporación por haz de electrones. Se ha estudiado su interacción con moléculas crosslinkers, y se han realizado varios inmunoensayos usando el ITO nanoestructurado como sustrato. Se han estudiado distintos mecanismos de medida de sensores electroquímicos; por espectroscopía de impedancias se han detectado distintas concentraciones del biomarcador TNF-α. Se ha diseñado la electrónica necesaria para realizar medidas de amperometría con dos electrodos, así como de potenciometría, ensayando este último sistema con ITO nanoestructurado y modificado sensible a cambios de pH. En síntesis, esta tesis recoge algunas propuestas para la mejora de los sistemas POC actuales, tanto en la cuestión biosensora como en la parte electrónica, usando para las medidas y pruebas de concepto un biomarcador importante en el ámbito biomédico.
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Rattanavoravipa, Thitima. "Studies on surface modification of nanostructured metal oxide for hybrid solar cells." Kyoto University, 2009. http://hdl.handle.net/2433/126414.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第14965号
エネ博第208号
新制||エネ||46(附属図書館)
27403
UT51-2009-M879
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)准教授 佐川 尚, 教授 八尾 健, 教授 萩原 理加
学位規則第4条第1項該当
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Coleman, Nicholas Richard Boldero. "Direct liquid crystal templating of mesoporous silica and platinum." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302011.
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Johnson, Ryan David. "Adhesion and deformation during thermocompression bonding of vertically aligned carbon nanotube turfs to metallized substrates." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/r_johnson_120808.pdf.
Full textAbstract:
Thesis (M.S. in materials science and engineering)--Washington State University, December 2008.Title from PDF title page (viewed on Mar. 3, 2009). "Department of Mechanical and Materials Engineering." Includes bibliographical references.
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Olea, Mejía Oscar Fernando Brostow Witold. "Micro and nano composites composed of a polymer matrix and a metal disperse phase." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5135.
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Su, Zixue. "Porous anodic metal oxides." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1019.
Full textAbstract:
An equifield strength model has been established to elucidate the formation mechanism for the highly ordered alumina pore arrays and titanium oxide nanotubular arrays prepared via a common electrochemical methodology, anodisation. The fundamentals of the equifield strength model was the equilibrium between the electric field driven oxidation rate of the metal and electric field enhanced dissolution rate of oxide. During the anodic oxidation of metal, pore initiation was believed to generate based on dissolution rate difference caused by inhomogeneity near the metal/oxide interface. The ionic nanoconvection driven by the electric force exerted on the space charge layer in the vicinity of electrolyte/oxide interface is established to be the main driving force of the pore ordering at the early stage of the anodisation. While the equifield strength requirement governs the following formation of the single pore and the self-ordering of random distributed pore arrays during the anodisation process. Hexagonal patterned Al2O3 nanopore arrays and TiO2 nanotubular arrays have been achieved by anodisation of corresponding metal substrates in proper electrolytes. The two characteristic microstructural features of anodic aluminium oxide (AAO) and anodic titanium oxide (ATO) were investigated using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The observations of the hemispherical electrolyte/oxide and oxide/metal interfaces, uniform thickness of the oxide layer, as well as self-adjustment of the pore size and pore ordering can be well explained by the equifield strength model. Field enhanced dissociation of water is extremely important in determination of the porosity of anodic metal oxide. The porosity of AAO and ATO films was found to be governed by the relative dissociation rate of water which is dependent on anodisation conditions, such as electrolyte, applied voltage, current density and electric field strength. Using an empirical method, the relations between the porosity of the AAO (ATO) films and the anodisation parameters, such as electric field strength, current density and applied voltage, have been established. Besides, the extent that an external electric field can facilitate the heterolytic dissociation of water molecule has been estimated using quantum-chemical model computations combined with the experimental aspect. With these achievements, the fabrication of anodic metal oxide films can be understood and controlled more precisely. Additionally, the impacts of other factors such as the electrolyte type and the temperature effect on the morphology of the anodic products were also investigated. Some important experimental evidences on the pore diameters variation with applied voltage in the anodisation of aluminium and the titanium were obtained for future investigation of the anodic metal oxide formation processes.
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Fung, Kin-Hung. "Theoretical study of the plasmonic modes of metal nanoparticle arrays and their optical responses /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202008%20FUNG.
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Ogbazghi, Asmerom Yemane. "Conductance through Nanometer-scale Metal-to-Graphite Contacts." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6872.
Full textAbstract:
The metal/graphite interface is interesting due to the typically large disparity in the characteristics of the electronic structure (e.g.
Fermi wavelength and Fermi energy) and dimensionality (3D in the metal versus quasi-2D in graphite). The goal of this work is to
determine how the contact conductance to graphite depends on the metal contact area for nanometer-scale contacts. From this we deduce the
effect of electronic screening in the graphite. Three different metals were chosen for this work: Solid Cu and Al, and liquid Ga.
Liquid Ga provided a unique opportunity to reduce the effect of mechanical interactions to near zero, while Cu and Al were chosen for
their different electronic structures. At the interface between the metal and graphite, the large Fermi wavevector of Al should allow
phase matching of Al states to those in graphite, while the Cu Fermi surface lies inside of all available graphite wavevector states.
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Kijak, Anna M. "Analytical Preconcentration Systems Based on Nanostructured Materials." Miami University / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=miami1049915571.
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