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Dissertations / Theses on the topic 'Nanostructure materials'

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Published: 4 June 2021
Last updated: 1 August 2024

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1

Bude, Romain. "Synthèses et caractérisations de matériaux thermoélectriques nanostructurés." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC032/document.

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Les marchés de la thermoélectricité sont en pleine expansion avec l’intérêt croissant pour la récupération d’énergie thermique ou encore pour la gestion de la température de composants électroniques. En dépit de ses nombreux avantages, le développement de cette technologie est freiné par les performances des matériaux. Une voie d’amélioration identifiée est leur nanostructuration afin d’en diminuer la conductivité thermique de réseau.Dans ce travail de thèse, cette voie est appliquée au tellurure de bismuth, matériau connu pour posséder les meilleures performances autour de la température ambiante. Les matériaux sont obtenus par synthèse de nanoparticules en solution avant d’être mis en forme par pressage à chaud.Une première étude est réalisée sur la recherche d’un optimum de la taille de grain dans le massif. On montre que le contrôle des conditions de synthèse permet le contrôle des dimensions des nanoparticules. Par ailleurs, les analyses structurales et fonctionnelles des massifs après densification montrent que la variation de la taille initiale des particules permet le contrôle de la microstructure et des propriétés detransport des massifs.Une seconde étude porte sur la recherche d’un optimum en composition des matériaux Bi2Te3-xSex. Les analyses morphologiques mettent en évidence une structure complexe et particulière, laissant apparaitre la présence de trois phases dans les massifs.Les matériaux obtenus par cette méthode de synthèse possèdent a priori des propriétés de transport anisotropes. La caractérisation de leurs performances thermoélectriques est donc difficile. Plusieurs techniques de caractérisation sont mises en oeuvre afin de mieux connaitre leurs conductivités thermiques. Celles-ci sont faibles, ce qui montre l’intérêt de l’approche. Toutefois, leur conductivité électrique est plus basse que leurs homologues obtenus par des techniques plus conventionnelles. On montre néanmoins que l’optimisation des conditions de synthèse des particules entrant dans la composition des massifs alliés permet d’améliorer leurs propriétés électriques et donc leurs performances thermoélectriques
The global thermoelectric markets are in expansion with a growing interest for the energy harvesting or the thermal management of electronic components. Despite numerous advantages, this technology development is limited by the materials performances. A way to improve them is to use nanostructures in order to decrease the lattice thermal conductivity.In this work, this approach is applied to bismuth telluride, material well known for its high performance around room temperature. Materials are obtained from solution synthesis of nanoparticles before hot press compaction.A first study focuses on the determination of an optimal grain size in the bulk materials. It is shown that control over the synthesis parameters allows control on the size of nanoparticles.Moreover, structural and physical analyses on the bulks after sintering show that the change of thesynthesis parameters allows control over the microstructure and thermoelectric properties of the bulks.A second study is based on the study of an optimal composition of Bi2Te3-xSex materials. Morphological analysis show a specific and complex structure with three phases in the bulks.It is postulated that these materials should have anisotropic transport properties. Consequently, their characterizations are difficult. Different characterization techniques are used in order to have a better understanding of their thermal conductivities. Thermal conductivity of the bulks is found low which confirm the interest of this approach. However the electrical conductivity is lower than the one of the materials obtained by more conventional methods. We show that the synthesis parameters of the particles can be optimized to increase the thermoelectric performances of the bulk materials
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2

Zhou, Zhengzhi. "Synthesis of one-dimensional nanostructure materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29703.

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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Deng,Yulin; Committee Member: Hsieh, Jeffery S.; Committee Member: Nair, Sankar; Committee Member: Singh, Preet; Committee Member: Yao, Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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3

Srivastava, Devesh. "Fabrication of nanostructures and nanostructure based interfaces for biosensor application." Diss., Connect to online resource - MSU authorized users, 2008.

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4

Chew, Zheng Jun. "Integrated transducers and nanostructure synthesis." Thesis, Swansea University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678389.

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5

Tan, Yu-May. "Mesoporous materials." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370067.

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6

Yu, Mingjun. "Magnetism of films with controlled nanostructure." [Lincoln, Neb. : University of Nebraska-Lincoln], 1999. http://international.unl.edu/Private/1999/mingjunab.pdf.

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7

Tadd, Erica Heitman. "Spatial distribution of cobalt nanoclusters in a block copolymer matrix." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/19453.

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8

Chen, Fanglin. "Synthesis and characterization of nanostructured materials for electrochemical and catalytic applications." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/20004.

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9

Chan, Yu Fai. "Nanostructure characterization by transmission electron microscopy /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202002%20CHAN.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 62-63). Also available in electronic version. Access restricted to campus users.
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10

Chen, Xinyi, and 陈辛夷. "Wide band-gap nanostructure based devices." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49799290.

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Wide band gap based nanostructures have being attracting much research interest because of their promise for application in optoelectronic devices. Among those wide band gap semiconductors, gallium nitride (GaN) and zinc oxide (ZnO) are the most commonly studied and optoelectronic devices based on GaN and ZnO have been widely investigated. This thesis concentrates on the growth, optical and electrical properties of GaN and ZnO nanostructures, plus their application in solar cells and light emitting diodes (LEDs). GaN-nanowire based dye sensitized solar cells were studied. Different post-growth treatments such as annealing and coating with a TiOx shell were applied to enhance dye absorption. It was found that TiOx increased the dye absorption and the performance of the dye sensitized solar cell. ZnO nanorods were synthesized by vapor deposition and electrodeposition. Post-growth treatments such as annealing and hydrothermal processing were used to modify the defect chemistry and optical properties. LEDs based on GaN/ZnO heterojunctions were studied. The influence of ZnO seed layers on GaN/ZnO LEDs was investigated. GaN/ZnO LEDs based on ZnO nanorods with MgO and TiOx shells were also prepared in order to modify the LED performance. The coating condition of the shell was found to influence the current-voltage (I-V) characteristics and device performance. Moreover, high brightness LEDs based on GaN with InGaN multiple quantum wells were also fabricated. The origin of the emission from GaN/ZnO LEDs was studied using different kinds of GaN substrates. Direct metal contacts on bare GaN substrates were also employed to investigate the optical emission and electrical properties. It is found that the emission from the GaN/ZnO LEDs probably originated from the GaN substrate. GaN/ZnO LEDs with MgO as an interlayer were also fabricated. The MgO layer was expected to modify the band alignment between the GaN and the ZnO. It was shown that GaN/MgO/ZnO heterojunctions (using both ZnO nanorods and ZnO films) have quite different emission performance under forward bias compared to those that have no MgO interlayer. An emission peak was around 400 nm could originate from ZnO. Nitrogen doped ZnO nanorods on n-type GaN have been prepared by electrodeposition. Zinc nitrate and zinc acetate were used as ZnO precursors and NH4NO3 was used as a nitrogen precursor. Only the ZnO nanorods made using zinc nitrate showed obvious evidence of doping and coherent I-V characteristics. Cerium doped ZnO based LEDs were fabricated and showed an emission that depended on the cerium precursor that was employed. This indicates that the choice of precursor influences the growth, the materials properties and the optical properties of ZnO.
published_or_final_version
Physics
Doctoral
Doctor of Philosophy
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11

Tong, Wing-yun. "Organic optoelectronic materials optical properties and 1D nanostructure fabrication /." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38574597.

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12

Yeh, Wei-Ming. "Pattern collapse in lithographic nanostructures: quantifying photoresist nanostructure behavior and novel methods for collapse mitigation." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47696.

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The Microelectronics industry has continuously pushed the limit of critical dimensions to sub-20 nm. One of the challenges is pattern collapse, caused by unbalanced capillary forces during the final rinse and drying process. The use of surfactants offers a convenient method to reduce capillary forces but causes another deformation issue. This thesis work focuses on alternative approaches that are compatible with lithographic processes to mitigate pattern collapse. First, an e-beam lithography pattern with a series of varying line and space widths has been specifically designed in order to quantitatively study pattern collapse behavior. This pattern generates increasing stress in the pairs of resist lines as one moves across the pattern array and eventually a sufficiently small space value (critical space, S1c) is reached in each array such that the stress applied to the resist exceeds the critical stress (σc) required for pattern bending and subsequently feature deformation and collapse occurrs. The patterns we designed allow us to qualitatively and quantitatively study pattern collapse and obtain consistent, reproducible results. In the first part of the thesis work, a quick surface crosslink (called a reactive rinse) that involves the strengthening of the resist using crosslinking via carbodiimide chemistry while the resist structures are still in their wet state, has been developed and demonstrated. This technique provides efficient and significant improvement on the pattern collapse issue. In the second part of the thesis work, a triethoxysilane compound, vinyl ether silane (VE), has been successfully synthesized. It can be used to modify the silicon or silicon nitride substrates and form a covalent bond with the resist film instead of manipulating the surface energies using common HMDS. Compared to traditional Hexamethyldisilazane (HMDS) vapor primed surfaces, the implementation of the VE adhesion promoter resulted in a significant improvement in the adhesion and resistance to adhesion based pattern collapse failure in small sub-60 nm resist features. In the third part of the thesis work, the effect of drying rates and drying methods has been systematically studied. SEM analysis and critical stress results showed that fast drying appear to reduce the resist collapse. The line pair orientations in each pattern array with respect to the wafer radius reveal an apparent effect of fluid flow and centrifugal forces on collapse. Finally, a comprehensive pattern collapse model that incorporates adhesion based pattern failure and elastoplastic deformation-based failure, and dimensionally dependent resist modulus properties has been developed. This model provides such an excellent prediction of the experimental data and supports the idea that this level of combined adhesion-failure and elastoplastic-failure based pattern collapse modeling, where one explicitly considers the dimensionally dependent mechanical properties of the resist can be quantitatively predictive and useful for understanding the pattern collapse behavior of polymeric nanostructures.
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13

Tong, Wing-yun, and 唐穎潤. "Organic optoelectronic materials: optical properties and 1D nanostructure fabrication." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38574597.

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14

Doss, Calvin James. "Raman studies of the nanostructure of sol-gel materials." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164932/.

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15

Shao, Qinghui. "Optimized designs and materials for nanostructure based solar cells." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957340961&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268668089&clientId=48051.

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Thesis (Ph. D.)--University of California, Riverside, 2009.
Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 12, 2010). Includes bibliographical references. Also issued in print.
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16

Yin, Jinsong. "Self-assembly of ordered nanostructures." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19116.

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17

Xing, Wenting Ph D. Massachusetts Institute of Technology. "Design of stable nanostructure configurations in ternary alloys." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/117947.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 129-135).
The development of stable nanocrystalline binary alloys, which possess a large volume fraction of grain boundaries at elevated temperatures, is a promising route to high yield strength materials. Previous studies have focused on alloying by selecting solute elements that segregate at grain boundaries to stabilize the nanostructure. A selection criterion has been established for designing stable binary nanocrystalline materials. This thesis explores the extension of this concept to the design of multicomponent nanostructured systems. In contrast to the simplicity of a binary system where not many topological possibilities are accessible, multicomponent nanostructured systems are shown to occupy a vast space where the large majority of interesting configurations will be missed by a regular solution approximation. This thesis describes research to develop a conceptual basis for the thermodynamic properties of multicomponent nanocrystalline alloys, and to design interesting ternary configurations not accessible in binary systems. The conditions necessary to achieve the desired nanostructure configurations are developed in a model that takes solute interactions into consideration. Based on the model, we performed a systematic case study on one alloy system expected to exhibit nanocrystalline stability: Pt-Pd-Au. As a control, two binary systems (Pt-Au, Pt-Pd) were produced for comparison. While a uniform distribution of Pd is observed in binary Pt-Pd alloys at 400 °C, the results from scanning transmission electron microscopy (STEM) reveal that Pd segregation behavior was induced by the Au grain boundary segregation in the ternary system at 400 °C. Our work on induced co-segregation behavior of Pt-Pd-Au alloy is just a simple example of solute interaction in nanocrystalline alloys. Our approach more generally presents a new design framework to control the complex configurations possible in nanocrystalline materials by alloying element selection.
by Wenting Xing.
Ph. D.
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18

Nkosi, Mlungisi Moses. "Preparation and physico-chemical properties of nickel nanostructured materials deposited in etched ion-track membrane." Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_6214_1182749152.

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The development of finely dispersed powders and superfine-grained materials intended for application in various areas of science and engineering is one of the challenges facing modern nanotechnology. Thus, specific fundamental and applied research was required in order to consolidate advancement made in preparing nano- and submicron crystalline composite materials.


Useful templates for electrochemical deposition of nanowires include porous alumina films formed by anodic oxidation of aluminium, nuclear track-etched porous membranes, nanochannel array-glass and mesoporous channel hosts. The properties of the nanowires are directly related to the properties of the nanoporous templates such as, the relative pore orientations in the assembly, the pore size distribution, and the surface roughness of the pores. The template synthesis method, based on the use of porous polymeric and inorganic matrixes, is now actively used for synthesis of such composite materials. The method allows the chemical and/or electrochemical synthesis of nano- and microstructured tubes and wires consisting of conducting polymers, metals and semiconductors.


In this study various technological challenges relating to template synthesis and development of nickel nano- and microstructures on adequately strong and durable substrates were investigated. The two methods used were the electrochemical and chemical deposition. &ldquo
Hard nickel&rdquo
bath solution was used for optimal nickel deposition. This optimization included investigating variables such as the template structure, type of electrolyte and form of electrolytic deposition. Scanning Electron Microscopy was used to investigate the structures of template matrixes and the resultant materials. The cyclic voltammetry method was applied for the analysis of electrochemical properties and hydrogen evaluation reaction of nano- and microstructured nickel based electrodes. The activity of composite nano- and microstructured materials in various configurations resulting from pore filling of template matrices by nickel was explored. Studies of the physical structure and chemical properties of the nanostructured materials included investigating the necessary parameters of template matrices. The optimum conditions of synthesis, which allowed development of materials with the highest catalytic activity, were determined. 
The effect of the template structure on microcrystallinity of the catalyst particles was established using the XRD method. Different new types of non-commercial asymmetric ion track membranes has been tested for nanostructure preparation. The catalytic activity of the new developed nanomaterials is higher as compared to materials using commercial templates. The procedures to modify the newly developed nickel catalyst with Pt, Pd and Pt-Pd alloy have been developed. The Pt and Pt-Pd alloy containing catalyst showed the best performance in water electrolysis. In this work, the promising role for specific application of the new materials in hydrogen economy has been demonstrated.

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19

Link, Stephen. "Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/30706.

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20

Yang, Zhaoyang. "Spin angular momentum transfer in magnetic nanostructure." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4720.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 4, 2008) Vita. Includes bibliographical references.
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21

Dong, Ou. "Polymer nanostructure fabrication and application in biosensors /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CBME%202009%20DONG.

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22

Kimura, Yoshihiko. "Self-Assembled Polymer Materials : From Amphiphile Design to Nanostructure Control." Kyoto University, 2020. http://hdl.handle.net/2433/259742.

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23

Chang, Sehoon. "Organic/inorganic hybrid nanostructures for chemical plasmonic sensors." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39545.

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The work presented in this dissertation suggests novel design of chemical plasmonic sensors which have been developed based on Localized Surface Plasmon Resonance (LSPR), and Surface-enhanced Raman scattering (SERS) phenomena. The goal of the study is to understand the SERS phenomena for 3D hybrid (organic/inorganic) templates and to design of the templates for trace-level detection of selected chemical analytes relevant to liquid explosives and hazardous chemicals. The key design criteria for the development of the SERS templates are utilizing selective polymeric nanocoatings within cylindrical nanopores for promoting selective adsorption of chemical analyte molecules, maximizing specific surface area, and optimizing concentration of hot spots with efficient light interaction inside nanochannels. The organic/inorganic hybrid templates are optimized through a comprehensive understanding of the LSPR properties of the gold nanoparticles, gold nanorods, interaction of light with highly porous alumina template, and the choice of physical and chemical attributes of the selective coating. Furthermore, novel method to assemble silver nanoparticles in 3D as the active SERS-active substrate has been demonstrated by uniform, in situ growth of silver nanoparticles from electroless deposited silver seeds excluding any adhesive polymer layer on template. This approach can be the optimal for SERS sensing applications because it is not necessary to separate the Raman bands of the polyelectrolyte binding layer from those of the desired analyte. The fabrication method is an efficient, simple and fast way to assemble nanoparticles into 3D nanostructures. Addressable Raman markers from silver nanowire crossbars with silver nanoparticles are also introduced and studied. Assembly of silver nanowire crossbar structure is achieved by simple, double-step capillary transfer lithography. The on/off SERS properties can be observed on silver nanowire crossbars with silver nanoparticles depending on the exact location and orientation of decorated silver nanoparticles nearby silver nanowire crossbars. As an alternative approach for the template-assisted nanostructure design, porous alumina membrane (PAM) can be utilized as a sacrificial template for the fabrication of the nanotube structure. The study seeks to investigate the design aspects of polymeric/inorganic hybrid nanotube structures with plasmonic properties, which can be dynamically tuned by external stimuli such as pH. This research suggests several different organic/inorganic nanostructure assemblies by various template-assisted techniques. The polymeric/inorganic hybrid nanostructures including SERS property, pH responsive characteristics, and large surface area will enable us to understand and design the novel chemical plasmonic sensors.
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24

Kubo, Shiori. "Nanostructured carbohydrate-derived carbonaceous materials." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5315/.

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Nanoporous carbon materials are widely used in industry as adsorbents or catalyst supports, whilst becoming increasingly critical to the developing fields of energy storage / generation or separation technologies. In this thesis, the combined use of carbohydrate hydrothermal carbonisation (HTC) and templating strategies is demonstrated as an efficient route to nanostructured carbonaceous materials. HTC is an aqueous-phase, low-temperature (e.g. 130 – 200 °C) carbonisation, which proceeds via dehydration / poly-condensation of carbon precursors (e.g. carbohydrates and their derivatives), allowing facile access to highly functional carbonaceous materials. Whilst possessing utile, modifiable surface functional groups (e.g. -OH and -C=O-containing moieties), materials synthesised via HTC typically present limited accessible surface area or pore volume. Therefore, this thesis focuses on the development of fabrication routes to HTC materials which present enhanced textural properties and well-defined porosity. In the first discussed synthesis, a combined hard templating / HTC route was investigated using a range of sacrificial inorganic templates (e.g. mesoporous silica beads and macroporous alumina membranes (AAO)). Via pore impregnation of mesoporous silica beads with a biomass-derived carbon source (e.g. 2-furaldehyde) and subsequent HTC at 180 oC, an inorganic / carbonaceous hybrid material was produced. Removal of the template component by acid etching revealed the replication of the silica into mesoporous carbonaceous spheres (particle size ~ 5 μm), representing the inverse morphological structure of the original inorganic body. Surface analysis (e.g. FTIR) indicated a material decorated with hydrophilic (oxygenated) functional groups. Further thermal treatment at increasingly elevated temperatures (e.g. at 350, 550, 750 oC) under inert atmosphere allowed manipulation of functionalities from polar hydrophilic to increasingly non-polar / hydrophobic structural motifs (e.g. extension of the aromatic / pseudo-graphitic nature), thus demonstrating a process capable of simultaneous control of nanostructure and surface / bulk chemistry. As an extension of this approach, carbonaceous tubular nanostructures with controlled surface functionality were synthesised by the nanocasting of uniform, linear macropores of an AAO template (~ 200 nm). In this example, material porosity could be controlled, showing increasingly microporous tube wall features as post carbonisation temperature increased. Additionally, by taking advantage of modifiable surface groups, the introduction of useful polymeric moieties (i.e. grafting of thermoresponsive poly(N-isopropylacrylamide)) was also demonstrated, potentially enabling application of these interesting tubular structures in the fields of biotechnology (e.g. enzyme immobilization) and medicine (e.g. as drug micro-containers). Complimentary to these hard templating routes, a combined HTC / soft templating route for the direct synthesis of ordered porous carbonaceous materials was also developed. After selection of structural directing agents and optimisation of synthesis composition, the F127 triblock copolymer (i.e. ethylene oxide (EO)106 propylene oxide (PO)70 ethylene oxide (EO)106) / D-Fructose system was extensively studied. D-Fructose was found to be a useful carbon precursor as the HTC process could be performed at 130 oC, thus allowing access to stable micellular phase. Thermolytic template removal from the synthesised ordered copolymer / carbon composite yielded functional cuboctahedron single crystalline-like particles (~ 5 μm) with well ordered pore structure of a near perfect cubic Im3m symmetry. N2 sorption analysis revealed a predominantly microporous carbonaceous material (i.e. Type I isotherm, SBET = 257 m2g-1, 79 % microporosity) possessing a pore size of ca. 0.9 nm. The addition of a simple pore swelling additive (e.g. trimethylbenzene (TMB)) to this system was found to direct pore size into the mesopore size domain (i.e. Type IV isotherm, SBET = 116 m2g-1, 60 % mesoporosity) generating pore size of ca. 4 nm. It is proposed that in both cases as HTC proceeds to generate a polyfuran-like network, the organised block copolymer micellular phase is essentially “templated”, either via hydrogen bonding between hydrophilic poly(EO) moiety and the carbohydrate or via hydrophobic interaction between hydrophobic poly(PO) moiety and forming polyfuran-like network, whilst the additive TMB presumably interact with poly(PO) moieties, thus swelling the hydrophobic region expanding the micelle template size further into the mesopore range.
Nanoporöse kohlenstoffbasierte Materialien sind in der Industrie als Adsorbentien und Katalysatorträger weit verbreitet und gewinnen im aufstrebenden Bereich der Energiespeicherung/erzeugung und für Trennverfahren an wachsender Bedeutung. In der vorliegenden Arbeit wird gezeigt, dass die Kombination aus hydrothermaler Karbonisierung von Zuckern (HTC) mit Templatierungsstrategien einen effizienten Weg zu nanostrukturierten kohlenstoffbasierten Materialien darstellt. HTC ist ein in Wasser und bei niedrigen Temperaturen (130 - 200 °C) durchgeführter Karbonisierungsprozess, bei dem Zucker und deren Derivate einen einfachen Zugang zu hochfunktionalisierten Materialien erlauben. Obwohl diese sauerstoffhaltige Funktionalitäten auf der Oberfläche besitzen, an welche andere chemische Gruppen gebunden werden könnten, was die Verwendung für Trennverfahren und in der verzögerten Wirkstofffreisetzung ermöglichen sollte, ist die mittels HTC hergestellte Kohle für solche Anwendungen nicht porös genug. Das Ziel dieser Arbeit ist es daher, Methoden zu entwickeln, um wohldefinierte Poren in solchen Materialien zu erzeugen. Hierbei führte unter anderem der Einsatz von anorganischen formgebenden mesoporösen Silikapartikeln und makroporösen Aluminiumoxid-Membranen zum Erfolg. Durch Zugabe einer Kohlenstoffquelle (z. B. 2-Furfural), HTC und anschließender Entfernung des Templats konnten poröse kohlenstoffbasierte Partikel und röhrenförmige Nanostrukturen hergestellt werden. Gleichzeitig konnte durch eine zusätzliche Nachbehandlung bei hoher Temperatur (350-750 °C) auch noch die Oberflächenfunktionalität hin zu aromatischen Systemen verschoben werden. Analog zur Formgebung durch anorganische Template konnte mit sog. Soft-Templaten, z. B. PEO-PPO-PEO Blockcopolymeren, eine funktionelle poröse Struktur induziert werden. Hierbei machte man sich die Ausbildung geordneter Mizellen mit der Kohlenstoffquelle D-Fructose zu Nutze. Das erhaltene Material wies hochgeordnete Mikroporen mit einem Durchmesser von ca. 0,9 nm auf. Dieser konnte desweiteren durch Zugabe von Quell-Additiven (z. B. Trimethylbenzol) auf 4 nm in den mesoporösen Bereich vergrößert werden. Zusammenfassend lässt sich sagen, dass beide untersuchten Synthesewege nanostrukturierte kohlenstoffbasierte Materialien mit vielfältiger Oberflächenchemie liefern, und das mittels einer bei relativ niedriger Temperatur in Wasser ablaufenden Reaktion und einer billigen, nachhaltigen Kohlenstoffquelle. Die so hergestellten Produkte eröffnen vielseitige Anwendungsmöglichkeiten, z. B. zur Molekültrennung in der Flüssigchromatographie, in der Energiespeicherung als Anodenmaterial in Li-Ionen Akkus oder Superkondensatoren, oder als Trägermaterial für die gezielte Pharmakotherapie.
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25

Trelewicz, Jason R. "Nanostructure stabilization and mechanical behavior of binary nanocrystalline alloys." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46679.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2009.
Includes bibliographical references (leaves 131-145).
The unique mechanical behavior of nanocrystalline metals has become of great interest in recent years, owing to both their remarkable strength and the emergence of new deformation physics at the nanoscale. Of particular interest has been the breakdown in Hall-Petch strength scaling, which is frequently attributed by atomistic simulations to a mechanistic shift to interface dominated plasticity. Experimental validation has been less abundant, primarily due to the processing challenges associated with achieving homogeneous nanocrystalline samples suitable for mechanical testing. Alloying has been proposed as a potential route to high-quality nanocrystalline metals, although choice of an appropriate alloy system, based on available thermodynamic data, remains elusive. In this thesis, we propose a thermodynamic model for nanostructure stabilization that derives from the energetic state variables characteristic of binary alloys. These modeling results motivate the study of Ni-W alloys in particular, which may be synthesized via aqueous electrodeposition, accessing grain sizes across the entire Hall-Petch breakdown regime as characterized by x-ray diffraction and transmission electron microscopy. Ambient temperature nanoindentation testing is employed to evaluate the mechanical behavior of the as-deposited alloys, assessing the nature of flow, the rate sensitivity, and pressure sensitivity of deformation, with emphasis on property inflections required to bridge the behavior of nanocrystalline metals to amorphous solids. The rate sensitivity, in particular, demonstrates an inherent dependence on nanocrystalline grain size, exhibiting a maximum in the vicinity of the Hall-Petch breakdown as a consequence of a shift to glass-like shear localization. In light of this finding, we study the Hall-Petch breakdown at high strain rates, and show that an "inverse Hall-Petch" weakening regime emerges at high rates. Additional effects from structural relaxation are investigated, and illustrated to strongly influence the strength scaling behavior and shift to inhomogeneous flow. Relaxed samples are also subjected to elevated temperature indentation tests, and the results discussed in the context of thermally-activated plasticity, thus providing a more quantitative analysis of the nanoscale deformation mechanisms.
by Jason R. Trelewicz.
Ph.D.
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Huang, Chun. "Processing and properties of nanostructured solid-state energy storage devices." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:f97b7c40-35cc-4cd8-96d4-9928ec62b368.

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A scalable spray processing technique was used to fabricate carbon nanotube (CNT)-based film electrodes and solid-state supercapacitors. The sprayed CNT-based electrodes comprised a randomly interconnected meso-porous network with a high electrical conductivity. Layer-by-layer (LbL) deposition of functionalised and oppositely charged single-wall carbon nanotubes (SWNTs) increased the electrode density and improved charging and discharging kinetics when compared with carboxylic functionalised only SWNT electrodes. The capacitance was further increased to 151 F g-1 at 2 mV s-1 and 120 F g-1 at 100 mV s-1 after vacuum and H2 heat treatments that removed the functional groups, and resulted in a hybrid microstructure of SWNTs and multi-layer graphene sheets from unzipped SWNTs. Flexible solid-state supercapacitors were fabricated by directly spraying multi-wall carbon nanotube (MWNT)-based aqueous suspensions onto both sides of a Nafion membrane and dried. A single cell with MWNT-only electrodes had a capacitance of 57 F g-1 per electrode at 2 mV s-1 and 44 F g-1 at 150 mV s-1. Cells with MWNT/ionomer electrodes showed a higher H+ mobility and a lower charge transfer resistance, and the capacitance increased to 145 F g-1 at 2 mV s-1 and 91 F g-1 at 150 mV s-1. Finally, MWNT/TiO2 nanoparticle/ionomer hybrid electrodes were used in the same solid-state supercapacitor configuration and provided a capacitance of 484 F g-1 per electrode at 5 mV s-1 and 322 F g-1 at 100 mV s-1. A qualitative model of the charge storage mechanism was developed, where TiO2 promoted H+ ions via redox reactions that fed protons into the proton-conducting ionomer coating over the MWNTs (in which the TiO2 was embedded), while electrons were readily conducted through the MWNT scaffold. This solid-state supercapacitor provided both attractive energy (31.8 Wh kg-1) and power (14.9 kW kg-1) densities, where such high energy density is difficult to achieve for MWNTs alone and such high power density is difficult for metal oxides alone, especially in the solid state.
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Wu, Nan. "Studies on Photo-initiation of Nanostructure Materials by Femtosecond Laser Irradiation." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157598.

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28

Zeng, Qinghua Materials Science &amp Engineering Faculty of Science UNSW. "Fundamental studies of oganoclays and polymer nanocomposites." Awarded by:University of New South Wales. School of Materials Science and Engineering, 2004. http://handle.unsw.edu.au/1959.4/20657.

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Polymer materials are commonly reinforced with organic or inorganic fillers to improve their mechanical properties and to reduce the cost. Such reinforcement strongly depends on the characteristics of fillers (e.g. size, shape, aspect ratio and surface feature) and their dispersion in polymer matrix. The use of inorganic fillers exploits the synergistic effect of high mechanical strength and heat durability of fillers and processing ease of polymers. However, it often causes interfacial incompatibility and an increase in density and a loss of tenacity and opacity. Because layered clays possess rich intercalation chemistry and can be delaminated into disk-like nanopartciles, we investigate the possibility of developing polymer nanocomposites from montmorillonite (MMT). As a result, two nanomaterials, intercalated polyaniline (PANI) nanocomposites and exfoliated PS nanocomposites, have been fabricated via in situ polymerization. Morevoer, experimental work shows that the surface modification of clays and the dispersion of organically modified clays (i.e. organoclays) are crucial to the success of fabricating polymer nanocomposites. Therefore, molecular dynamics (MD) simulations are used to investigate such fundamental aspects on the structure and dynamics of organoclays and the interfacial interactions and structure of diblock copolymer (i.e. PU) nanocomposites. The simulated results are in good agreement with the available experimental data. For organoclays, the results indicate that the alkyl chains exhibit strong layered structures in the interlayer space of clays. Such layering behaviors strongly depend on the chain length and layer charge. More importantly, a pseudo-quadrilayer structure is observed for organoclays modified with dioctadecyldimethyl ammoniums in which the alkyl chains do not lie flat within a single layer but interlace and spread into the adjacent layers. Finally, different orientaion of chain segments is found in the middle and end segments, and within and out of the layer structure. For polyurethane (PU) nanocomposites, van der Waals interaction between apolar alkyl chains and PU soft segments dominates the interactions between organoclay and PU. In addition, hydrogen bonding can form between the siloxane oxygen of clay surface and nitrogen (hard segment) or oxygen (soft segments) of PU. Furthermore, there is no distinct phase-separated structure for PU in the nanocomposites, which is attributed to the results of competitive interactions among PU, alkyl ammonium and clay surface.
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Green, Travis Christopher. "Photo-induced charge carrier dynamics and self-organization in semiconductor and metallic nanocrystals : in between the bulk and individual molecules." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30480.

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Shafigullin, Marat Nailevich. "Preparation and structural studies of gold nanocrystals and their arrays." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30991.

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31

Rudenko, Anton. "Numerical study of ultrashort laser-induced periodic nanostructure formation in dielectric materials." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSES020/document.

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Cette thèse se concentre sur l'étude numérique de l'interaction laser ultrabref avec les diélectriques transparents. En particulier, le phénomène d'auto-organisation des nanoréseaux dans la silice est discuté et un modèle multiphysique est proposé pour expliquer le mécanisme de leur formation. Les nanoréseaux en volume sont des nanostructures périodiques de périodicité sub-longueur d'onde, qui consistent en un matériau moins dense et sont générés par une irradiation laser multi-impulsionnelle femtoseconde dans certains verres, cristaux et semiconducteurs. Leur origine physique ainsi que les conditions d'irradiation laser pour leur formation et leur effacement sont investiguées dans ce travail théorique. Pour simuler la propagation nonlinéaire dans les verres, les équations de Maxwell sont couplées avec l'équation d'évolution de la densité électronique. Il est démontré que les nanoplasmas périodiques 3D sont formés pendant l'interaction laser ultrabref avec les inhomogénéités de la silice fondue. Les nanopores induits par laser sont supposés jouer le rôle de centres inhomogènes de diffusion. La périodicité sub-longueur d'onde et l'orientation des nanoplasmas dépendante de la polarisation, révélées dans cette thèse, font d'eux un excellent candidat pour expliquer la formation des nanoréseaux en volume. En plus, il est demontré que les nano-ripples sur la surface de silice fondue et les nanoréseaux en volume ont des mécanismes de formation similaires. Pour justifier la présence de nanopores dans la silice fondue irradiée par laser, les processus de décomposition du verre sont étudiés. Premièrement, les profils de température sont calculés sur la base d'un modèle électron-ion. Ensuite, à partir des températures calculées, des critères de cavitation et de nucléation dans le verre ainsi que des équations hydrodynamiques de Rayleigh-Plesset, les conditions pour la formation des nanopores et la survie des nanoréseaux en volume sont élucidées. Pour établir les dépendances des paramètres du laser de formation et d'effacement des nanoréseaux en volume, l'approche multiphysique est développée comprenant la propagation du laser ultrabref dans le verre, les processus d'excitation/relaxation électroniques et le modèle à deux températures. Les résultats numériques fournissent les paramètres du laser en fonction de l'énergie de l'impulsion, sa durée et le taux de répétition pour induire des nanoréseaux en volume, en bon accord avec les expériences nombreuses et indépendantes de la littérature. Le travail réalisé a non seulement permis de déterminer les mécanismes de formation des nanostructures périodiques mais améliore également notre connaissance du contrôle optimal des paramètres du laser sur la réponse ultrarapide d matériau, en ouvrant des nouvelles opportunités de traitement des diélectriques par laser ultrabref
This thesis is focused on the numerical modeling of ultrashort laser interaction with transparent dielectrics. More particularly, the phenomenon of self-organized volume nanogratings in fused silica bulk is discussed and a multiphysical model is proposed to explain the mechanism of their formation. Volume nanogratings are sub-wavelength periodic nanostructures, consisting of less dense material, which are commonly induced by multipulse femtosecond laser irradiation in some glasses, crystals and indirect semiconductors. Their physical origin as well as the laser irradiation conditions for theirformation and erasure are investigated in this theoretical work. To model the nonlinear propagation inside glass, Maxwell's equations are coupled with rate equation. It is shown that three-dimensional periodic nanoplasmas are formed during ultrashort laser interaction with fused silica inhomogeneities. Laser-induced nanopores are proposed to play the role of inhomogeneous scattering centers. Subwavelength periodicity and polarization dependent orientation of the nanoplasmas, revealed in this thesis, make them a strong candidate for explaining volume nanogratings formation. Additionally, it is demonstrated that the nanoripples on fused silica surface and volume nanogratings have similar formation mechanisms. To justify the presence of nanopores in laser-irradiated fused silica bulk, glass decomposition processes are investigated. Firstly, the temperature profiles are found by incorporating the electron-ion temperature model. Then, based on the calculated temperatures, criteria for cavitation and nucleation in glass and also hydrodynamic Rayleigh-Plesset equation, the conditions for nanopores formation and for volume nanogratings survival are elucidated. To define the laser parameter dependencies on the volume nanogratings formation/erasure, a selfconsistent multiphysical approach is developed including ultrafast laser propagation in glass, multiple rate equation to take into account excitation/relaxation processes and two-temperature model. The numerical results provide a laser parameter window as a function of laser pulse energy, laser pulse duration and repetition rate for volume nanogratings consistent with numerous independent experiments. The performed work not only provides new insights into the formation mechanisms of periodic nanostructures but also improves our knowledge of the optimal laser parameter control over ultrafast material response, opening new opportunities in ultrashort laser processing of dielectrics
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32

Kassangana, Alain Gabriel Mbengu. "Anodized alumina as a template for nanostructure processing." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112572.

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A novel way of producing nanostructures in the past decade has been through the use of an anodized alumina template. This template has dense, self-ordered nanometric pores that grow in the oxide as the aluminum is being anodized. This technique is a fairly new method of processing nanostructures, and much study and research is presently being done to understand the formation mechanisms of the highly ordered pores. Ultra-pure aluminum foil and pure aluminium single crystal plates were anodized to create porous anodized alumina, and using it as a template to electro-deposit Nickel nanostructures. The effects different anodizing parameters have on oxide creation were studied, and the results obtained from studying the effects of substrate purity and texture of the anodized aluminum substrate on the morphology of the alumina template, through the use of X-ray diffraction and scanning electron microscopy.
Nickel nanowires were prepared by DC electrodeposition inside the porous alumina template with a gold-palladium coating serving a conductive base. The nanowires have a diameter of 65 nm, and their length depends on the deposition time. The nanowires can uphold a position perpendicular to the substrate by partially dissolving the alumina template. They also have a tendency to gather together once the template is partially removed.
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33

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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34

Song, Myung-Eun. "Processing, Structure and Properties of High Temperature Thermoelectric Oxide Materials." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/98542.

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High temperature thermal energy harvesting has attracted much attention recently. In order to achieve stable operation at high temperatures there is emerging need to develop efficient and oxidation-resistant materials. Most of the well-known materials with high dimensionless figure of merit (ZT) values such as Bi2Te3, PbTe, skutterudites, and half-Heusler alloys, are not thermally stable at temperatures approaching 500°C or higher, due to the presence of volatile elements. Oxide thermoelectric materials are considered to be potential candidates for high temperature applications due to their robust thermal and chemical stability in oxidizing atmosphere along with the reduced toxicity, relatively simpler fabrication, and cost. In this dissertation, nanoscale texturing and interface engineering were utilized for enhancing the thermoelectric performance of oxide polycrystalline Ca3Co4O9 materials, which were synthesized using conventional sintering and spark plasma sintering (SPS) techniques. In order to tailor the electrical and thermal properties, Lu and Ga co-doping was investigated in Ca3Co4O9 system. The effect of co-doping at Ca and Co sites on the thermoelectric properties was quantified and the anisotropic behavior was investigated. Because of the effective scattering of phonons by doping-induced defects, lower thermal conductivity and higher ZT were achieved. The layered structure of Ca3Co4O9 has strong anisotropy in the transport properties. For this reason, the thermoelectric measurements were conducted for the samples along both vertical and horizontal directions. The ZT value along the vertical direction was found to be 3 to 4 times higher than that along the horizontal direction. Metallic inclusions along with ionic doping were also utilized in order to enhance the ZT of Ca3Co4O9. The texturing occurring in the nanostructured Ca3Co4O9 through ion doping and Ag inclusions was studied using microscopy and diffraction analysis. Multi-length scale inclusions and heavier ion doping in Ca3Co4O9 resulted in higher electrical conductivity and reduced thermal conductivity. The maximum ZT of 0.25 at 670°C was found in the spark plasma sintered Ca2.95Ag0.05Co4O9 sample. In literature, limited number of studies have been conducted on understanding the anisotropic thermoelectric performance of Ca3Co4O9, which often results in erroneous estimation of ZT. This study addresses this limitation and provides systematic evaluation of the anisotropic response with respect to platelet microstructure. Textured Ca3Co4O9/Ag nanocomposites were fabricated using spark plasma sintering (SPS) technique and utilized for understanding the role of microstructure towards anisotropic thermoelectric properties. The thermoelectric response was measured along both vertical and horizontal direction with respect to the SPS pressure axis. In order to achieve enhanced degree of texturing and increase electrical conductivity along ab planes, a two-step SPS method was developed. Ag nanoinclusions was found to increase the overall electrical conductivity and the thermoelectric power factor because of improved electrical connections among the grains. Through two-step SPS method, 28% improvement in the average ZT values below 400°C and 10% improvement above 400°C in Ca3Co4O9/Ag nanocomposites was achieved. Lastly, this dissertation provides significant progress towards understanding the effect of synthesis method on thermoelectric properties and evolution of textured microstructure. The anisotropy resulting from the crystal structure and microstructural features is systematically quantified. Results reported in this study will assist the continued progress in developing Ca3Co4O9 materials for practical thermoelectric applications.
PHD
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35

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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36

Song, Min Kyu. "Synthesis and characterization of nanostructured, mixed-valent compounds for electrochemical energy storage devices." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45925.

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The performances of current electrical energy storage systems (both batteries and electrochemical capacitors) are not capable of meeting the ever-increasing demands of emerging technologies. This is because batteries often suffer from slow power delivery, limited life-time, and long charging time whereas electrochemical capacitors suffer from low energy density. While extensive efforts have been made to the development of novel electrode materials, progress has been hindered by the lack of a profound understanding on the complex charge storage mechanism. Therefore, the main objective of this research is to develop novel electrode materials which can exhibit both high energy and power density with prolonged life-time and to gain a fundamental understanding of their charge storage mechanism. First, nanostructured, thin, and conformal coatings of transition metal oxides have been deposited onto three-dimensional porous substrates of current collectors to form composite electrodes. The structures and compositions of the oxide coatings are further altered by a controlled annealing process and characterized by electron microscopy and spectroscopy, laboratory X-ray diffraction, gas adsorption analysis, and in-situ and ex-situ synchrotron-enabled X-ray diffraction and absorption spectroscopy. The structural features have also been correlated with the electrochemical behavior of the transition metal oxides as an electrode in an electrochemical capacitor. It is found that the electrochemical performance of the composite electrodes depends sensitively on the composition, nanostructure, and morphology of the oxide coatings. When optimized, the electrodes displayed the highest energy and power density with excellent cycling life among all materials reported for electrochemical capacitors. Finally, new charge storage mechanisms have also been proposed for the novel electrode materials based on insights gained from in-situ synchrotron-based X-ray absorption spectroscopy.
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37

Windlass, Hitesh. "Development and integration of thin film polymer ceramic nanocomposite capacitor dielectrics in SOP." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19064.

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38

Zhao, Yu. "Correlation between structure, doping and performance of thermoelectric materials." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64899.

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Thermoelectric materials can convert thermal energy into electrical energy and vice-versa. They are widely used in energy harvesters, thermal sensors, and cooling systems. However, the low efficiency and high cost of the known material compositions limit their widespread utilization in electricity generation applications. Therefore, there is a strong interest in identifying new thermoelectric materials with high figure of merit. In response to this need, this dissertation works on the synthesis, structure, doping mechanism, and thermoelectric properties of zinc oxide (ZnO) and lead tellurium (PbTe). The main focus is on ZnO based materials and in improving their performance. The influences of micro- or nano-structures on thermal conductivity, as well as the correlation between the electrical property and synthesis conditions, have been systematically investigated. ZnO is a likely candidate for thermoelectric applications, because of its good Seebeck coefficient, high stability at high temperature, non-toxicity and abundance. Its main drawbacks are the high thermal conductivity (κ) and low electrical conductivity (σ). To decrease κ, two novel structures—namely, precipitate system and layered-and-correlated grain microstructure—have been proposed and synthesized in ZnO. The mechanisms iii governing the nature of thermal behavior in these structures have been explored and quantified. Due to strong phonon scattering, the nano-precipitates can reduce the thermal conductivity of ZnO by 73%. The ZnO with layered-and-correlated grains can further reduce κ by about 52%, which compares favorably with the dense ZnO with nanoprecipitates. The figure of merit of this ZnO based structure was 0.14×10⁻³ K⁻¹ at 573 K. In order to understand the electrical behavior in nanostructured ZnO, the impact of Al doping and chemical defects in ZnO under different synthesis conditions were studied. Under varying sintering temperatures, atmospheres and initial physical conditions, ZnO exhibited very distinct σ. High temperature, lack of oxygen, vacuum condition, and chemically synthesized powder can increase the carrier concentration and σ of ZnO. A promising alloy system, PbTe-PbS, undergoes natural phase separation by nucleation and growth, and spinodal decomposition depending on the thermal treatment. The correlation between the thermal treatment, structure, and the thermoelectric properties of Pb0.9S0.1Te has been studied. The nano-precipitates were incorporated in the annealed alloy resulting in a 40% decrease in κ. The PbS precipitation was shown to enhance the carrier concentration and improves the Seebeck coefficient. These concomitant effects result in a maximum ZT of 0.76 at 573 K. Throughout the thesis, the emphasis was on understanding the impact of the microstructures on thermal conductivity and the effect of the synthesis condition on thermal and electrical properties. The process and control variables identified in this study provide practical ways to optimize the figure of merit of ZnO and PbTe materials for thermoelectric applications.
Ph. D.
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39

Amooali, Khosroabadi Akram. "Optical and Electrical Properties of Composite Nanostructured Materials." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/333480.

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A novel lithographic fabrication method is used to fabricate nanopillars arrays of anisotropic Ag and TCO electrodes. Optical and electrical properties of the electrodes including bandgap, free carrier concentration, resistivity and surface plasmon frequency of different electrodes can be tuned by adjusting the dimensions and geometry of the pillars. Given the ability to tune the nonlocal responses of the plasmonic field enhancements, we attempt to determine the nature of the effective refractive index profile within the visible wavelength region for multi-layer hybrid nanostructures. Knowledge of the effective optical constants of the obtained structure is critical for various applications. nanopillars of TCO\Ag core shell structures have been successfully fabricated. The Maxwell-Garnett mixing law has been used to determine the optical constants of the nanostructure based on spectroscopic ellipsometry measurements. Simulated reflection spectra indicate a down shift in the Brewster angle of the pillars resulting from the reduction in the effective refractive index of the nanostructure. Two plasmonic resonances were observed, with one in the visible region and the other in the IR region. Plasmon hybridization model is used to describe the behavior of metal and metal oxide core shell nanostructured electrodes. Different charge density distributions around the pillars determine the plasma frequency which depends on the core and surrounding media dielectric constants. Finite Difference Time Domain (FDTD) simulation of different structures agree well with experiment and help us to understand electric field behavior at different structures with different geometries and dielectric constants. Plasmonic Ag nanopillar arrays are effective substrates for surface enhanced Raman spectroscopy (SERS). An enhancement factor up to 6 orders of magnitude is obtained. Monolayers of C60 is deposited on the Ag nanopillars and the interface of C60/Ag is studied which is important in optoelectronic devices. Electron delocalization between C60 and Ag is confirmed.
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40

Rice, Philip Zachary. "The Effect of Nanostructure on the Electrical Properties of Metal Oxide Materials." Thesis, State University of New York at Albany, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3568291.

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Resistive random access memory (ReRAM) is a potential replacement technology for Flash and other memory implementations. Advantages of ReRAM include increased scalability, low power operation, and compatibility with silicon semiconductor manufacturing. Most of the ReRAM devices described to date have utilized thin film based metal oxide dielectrics as a resistive switching matrix. The goal of this dissertation project has been to investigate the resistive switching behavior of nanoparticulate metal oxides and to develop methods to utilize these materials in ReRAM device fabrication. To this end, nanoparticles of TiO2 and HfO2 were synthesized under a variety of conditions resulting in various size, shape, and crystallinity. Electrical measurements of individual nanoparticles, as well as composite films of nanoparticles, were performed with limited success. To improve the stability of nanoparticle films, a spin on glass, hydrogen silsesquioxane (HSQ), was incorporated into the film stack. Addition of HSQ prevented electrical shorting and stabilized the nanoparticle films. In addition to serving as a stabilizer for nanoparticle films, HSQ was also found to have its own resistive switching properties. Composite films consisting of HSQ and nanoparticles yielded modified switching behavior which was tunable based upon nanoparticle composition and the thickness of the nanoparticle film. Our results demonstrate that both VSET and VRESET of HSQ switching can be increased when nanoparticles are incorporated with HSQ, without any significant changes to the device's high and low resistance states. We conclude that metal oxide nanoparticles can function as the dielectric material for ReRAM and can also be used to modulate the switching properties of composite ReRAM devices.

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41

Wang, Hai. "Block copolymer thin films for nanometer pattern generation and nanostructure synthesis." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36979843.

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42

Chang, Shih-wei Ph D. Massachusetts Institute of Technology. "Fabrication of high aspect ratio silicon nanostructure arrays by metal-assisted etching." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59214.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.
Includes bibliographical references (p. 167-178).
The goal of this research was to explore and understand the mechanisms involved in the fabrication of silicon nanostructures using metal-assisted etching. We developed a method utilizing metal-assisted etching in conjunction with block copolymer lithography to create ordered and densely-packed arrays of high-aspect-ratio single-crystal silicon nanowires with uniform crystallographic orientations. Nanowires with sub-20 nm diameters were created as either continuous carpets or as carpets within trenches. Wires with aspect ratios up to 220 with much reduced capillary-induced clustering were achieved through post-etching critical point drying. The size distribution of the diameters was narrow and closely followed the size distribution of the block copolymer. Fabrication of wires in topographic features demonstrated the ability to accurately control wire placement. The flexibility of this method will facilitate the use of such wire arrays in micro- and nano-systems in which high device densities and/or high surface areas are desired. In addition, we report a systematic study of metal-catalyzed etching of (100), (110), and (111) silicon substrates using gold catalysts with varying geometrical characteristics. It is shown that for isolated catalyst nanoparticles and metal meshes with small hole spacings, etching proceeded preferentially in the <100> direction. However, etching was confined in the direction vertical to the substrate surface when a catalyst mesh with large hole spacings was used. This result was used to demonstrate the use of metal-assisted etching to create arrays of vertically-aligned polycrystalline and amorphous silicon nanowires etched from deposited silicon thin films using catalyst meshes with relatively large hole spacings. The ability to pattern wires from polycrystalline and amorphous silicon thin films opens the possibility of making silicon nanowire-array-based devices on a much wider range of substrates. Finally, we demonstrated the fabrication of a silicon-nanopillar-based nanocapacitor array using metal-assisted etching and electrodeposition. The capacitance density was increased significantly as a result of an increased electrode area made possible by the catalytic etching approach. We also showed that the measured capacitance densities closely follow the expected trend as a function of pillar height and array period. The capacitance densities can be further enhanced by increasing the array density and wire length with the incorporation of known self-assembly-based patterning techniques such as block copolymer lithography.
by Shih-wei Chang.
Ph.D.
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43

Chen, Tao. "The mechanical properties and oxidation behavior of nanocrystalline NiAl synthesized via shock consolidation of mechanically alloyed powders of Ni and Al." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20029.

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Harrell, Lee E. "Investigation of gold nanocrystals by ultrahigh vacuum cryogenic scanning tunneling microscopy." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/30030.

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45

偉亞東 and Yadong Wei. "Resonant Andreev reflections in superconductor-carbon-nanotubedevices." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31242406.

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Li, Yanguang. "Nanostructured Materials for Energy Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275610758.

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Wang, Hai, and 王海. "Block copolymer thin films for nanometer pattern generation and nanostructure synthesis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36979843.

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48

Dondero, Russell A. "Silica coating of spinel ferrite nanoparticles." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/27375.

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Khovaylo, V., A. Usenko, M. Gorshenkov, and S. Kaloshkin. "Optimization of Ball-Milling Process for Preparation of Si-Ge Nanostructured Thermoelectric Materials." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35302.

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Here we report on technical details of preparation of Si-Ge-based nanostructured thermoelectic materials by a mechnical alloying method. It has been shown that for a milling speed of 350 rpm a single Si-Ge phase is formed after milling time less than 6 h. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35302
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50

Xiao, Zhizhao. "Optical properties of zinc oxide nanostructure materials using near-field scanning optical microscopy /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202007%20XIAO.

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