Dissertations / Theses on the topic 'Nanostructured'
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Akinyeye, Richard Odunayo. "Nanostructured polypyrrole impedimetric sensors for anthropogenic organic pollutants." Thesis, University of the Western Cape, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5301_1248150815.
Full textThe main aim of this study was to develop a novel strategy for harnessing the properties of electroconductive polymers in sensor technology by using polymeric nanostructured blends in the preparation of high performance sensor devices.
Wiley, Benjamin J. "Synthesis of silver nanostructures with controlled shapes and properties /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9923.
Full textJin, Kewang. "Fabrication and characterization of 1D oxide nanostructures /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202005%20JIN.
Full textYiu, Wing-ching James. "Synthesis of one-dimensional tungsten oxide nano-structures by thermal evaporation." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32047770.
Full textMarceau, Ross K. W. "Design in light alloys by understanding solute clustering processes during the early stages of age hardening in Al-Cu-Mg alloys." Connect to full text, 2008. http://ses.library.usyd.edu.au/handle/2123/4008.
Full textTitle from title screen (viewed Jan 07, 2009). Includes two published articles co-authored with others. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Australina Key Centre for Microscopy and Microanalysis, Electron Microscope Unit, Faculty of Science. Includes bibliographical references. Also available in print form.
Srivastava, Devesh. "Fabrication of nanostructures and nanostructure based interfaces for biosensor application." Diss., Connect to online resource - MSU authorized users, 2008.
Find full textLiu, Yong. "Novel nanostructured electrodes." Department of Chemistry - Faculty of Science, 2007. http://ro.uow.edu.au/theses/14.
Full textGilbank, Alexander. "Ceramic nanostructured catalysts." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648952.
Full textMusselman, Kevin Philip Duncan. "Nanostructured solar cells." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609003.
Full textDeplace, Fanny. "Waterborne nanostructured adhesives." Paris 6, 2008. http://www.theses.fr/2008PA066035.
Full textVandamme, Nicolas. "Nanostructured ultrathin GaAs solar cells." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112111/document.
Full textThe thickness reduction of solar cells is motivated by the reduction of production costs and the enhancement of conversion efficiencies. However, for thicknesses below a few hundreds of nanometers, new light trapping strategies are required. We propose to introduce nanophotonics and plasmonics concepts to absorb light on a wide spectral range in ultrathin GaAs layers. We conceive and fabricate multi-resonant structures made of arrays of metal nanostructures. First, we design a super-absorber made of a 25 nm-thick GaAs slab transferred on a back metallic mirror with a top metal nanogrid that can serve as an alternative front electrode. We analyze numerically the resonance mechanisms that result in an average light absorption of 80% over the 450nm-850nm spectral range. The results are validated by the fabrication and characterization of these multi-resonant super-absorbers made of ultrathin GaAs. Second, we use a similar strategy for GaAs solar cells with thicknesses 10 times thinner than record single-junction photovoltaic devices. A silver nanostructured back mirror is used to enhance the absorption efficiency by the excitation of various resonant modes (Fabry-Perot, guided modes,…). It is combined with localized ohmic contacts in order to enhance the absorption efficiency and to optimize the collection of photogenerated carriers. According to numerical calculations, the short-circuit current densities (Jsc) can reach 22.4 mA/cm2 and 26.0 mA/cm2 for absorber thicknesses of t=120 nm and t=220 nm, respectively. We have developed a fabrication process based on nano-imprint lithography and on the transfer of the active layers. Measurements exhibit record short-circuit currents up to 17.5 mA/cm2 (t=120 nm) and 22.8 mA/cm2 (t=220 nm). These results pave the way toward conversion efficiencies above 20% with single junction solar cells made of absorbers thinner than 200 nm
Chang, Sehoon. "Organic/inorganic hybrid nanostructures for chemical plasmonic sensors." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39545.
Full textWang, Lingyan. "Design and fabrication of functional nanomaterials with tunable electrical, optical, and magnetic properties." Diss., Online access via UMI:, 2007.
Find full textChubilleau, Caroline. "Influence d'inclusions de PbTe ou de ZnO sur les propriétés thermoélectriques de matériaux skutterudites." Thesis, Vandoeuvre-les-Nancy, INPL, 2010. http://www.theses.fr/2010INPL059N/document.
Full textThis work was carried out as part of a study on nanostructured bulk thermoelectric materials, compounds whose properties can potentially be improved with many interfaces. It is related to the synthesis and characterization of skutterudites (CoSb3 or In0.4Co4Sb12) containing nanoinclusions of PbTe or ZnO. Techniques of powder metallurgy and laser fragmentation in liquid medium were combined to X-rays diffraction analyses, SEM and TEM observations to develop the experimental procedure for the preparation of materials. The microstructures of the composites show that the dispersion step is the most difficult part of the preparation as it leads to agglomerates located at the grain boundaries. The porosity is also relatively large when the quantity of inclusions is high especially with ZnO. The electrical and thermal properties (thermoelectric power, electrical resistivity, Hall effect, thermal conductivity) have been measured over a wide temperature range (2-800 K) and correlated with the microstructures. The results analysis showed that PbTe tends to degrade the electrical properties of the two matrixes because of a reaction between the nanoparticles and the skutterudites. Contrarily, the addition of ZnO seems more promising although it is difficult to conclude definitively on its effectiveness given the complexity of the microstructures (defects, pores, grain boundaries). A theoretical model developed to better understand the impact of the particle sizes on the thermal properties showed that it is more interesting to work with partially filled skutterudites instead of pure CoSb3 since the inclusions mostly affect the scattering of long wavelength phonons. The trends that emerge from this study are rather in the sense of a deterioration of the thermoelectric properties with this type of nanostructure when the quantities of nanoparticles exceed a few percentage. The use of smaller quantities and a better controlled porosity should be considered
Al-Ajili, Adwan Nayef Hameed. "Photoluminescence of nanostructured silicon." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/26999.
Full textBarlow, Iain J. "Nanostructured Molecular Electronic Devices." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486548.
Full textMarshall, Matthew Spiro James. "Nanostructured strontium titanate surfaces." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509992.
Full textArias, Dylan H. "Coherence in nanostructured excitons." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82310.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 159-184).
Nanotechnology and optoelectronics have the potential to revolutionize the medicine, communications, and energy industries, with applications utilizing nanotechnology beginning to appear. However, there are still fundamental questions about optoelectronic devices incorporating nanotechnology. In particular, how do nanometer-scale materials affect potential functionality, and how can we take advantage of this scale to design nanomaterials for applications? Natural light harvesting systems in bacteria and plants provide exquisite examples of nanomaterial design, featuring remarkably efficient light harvesting antennas. Sunlight absorption first creates excitons. Complex antenna architectures control the excitons, directing them to reaction centers for conversion to chemical energy. Recently, studies found that excitonic interactions play a significant role in controlling antennas' light harvesting abilities, and that coherence may greatly affect energy transport efficiencies. While these studies have propelled our understanding of excitons in these systems, it is desirable to extend our expertise to artificial systems. In this thesis I describe experiments uncovering many fundamental properties of excitons in various nanostructured materials, relating physical structure to excitonic structure and perhaps to subsequent function in an excitonic device. Nonlinear spectroscopy offers distinct possibilities for detailed exploration of excitonic properties and processes in nanomaterials. Transient grating experiments are sensitive to population dynamics and energy transport, while multi-dimensional spectroscopy clearly reveals excitonic interactions, correlations, and coherence. In this thesis, these techniques are performed with a unique multi-dimensional spectrometer using femtosecond pulse shaping. I present results on two classes of artificial nanostructures: supramolecular J-aggregates and semiconductor quantum wells. In J-aggregate thin films I determined that coherence is controlled by thermal dephasing rather than film inhomogeneities, even at cryogenic temperatures. Tubular J-aggregates in solution undergo morphological rearrangement while maintaining a common sub-unit that remains relatively intact both structurally and excitonically. In semiconductor quantum wells, many-body correlations among excitons were shown to decay on the timescale picoseconds, depending on the exciton density and therefore revealing of high-order correlations. These insights into coherence and excitonic structure are important in determining the origin and strength of coherence in excitonic systems, potentially leading toward methods to alter or control exciton dynamics and toward possible novel application of coherence in optoelectronic devices.
by Dylan H. Arias.
Ph.D.
Finnemore, Alexander. "On biomimetic nanostructured materials." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610543.
Full textAlenezi, Mohammad Rabia. "Nanostructured zinc oxide sensors." Thesis, University of Surrey, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616927.
Full textTrofimovaite, Rima. "Nanostructured promoted titania photocatalysts." Thesis, Aston University, 2018. http://publications.aston.ac.uk/37498/.
Full textJara, Olivares Angelica Yuliana. "Biocompatible nanostructured multilayer systems." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT222/document.
Full textThin films have been the subject of intense study in materials because they offer multiple applications of great interest. Various surfaces have been modified with thin films or coatings to study how to improve their bioactivity and biocompatibility properties to form a biomaterial. Thin films of Ta, TaN and Ta/TaN were deposited on glass substrates, metallic substrates, SS316LVM and Ti, by RF Sputtering technique. By High angle XRD and GIXRD it was found that the nature of the substrate has a strong influence on the Ta phase formed. Formation of ordered α-Ta phase was obtained on SS316LVM, but the disordered metastable β-Ta phase was formed on Ti and on TaN substrates. While TaN crystallizes in the cubic phase (Fm3m) NaCl type on metallic substrates but shows a preferential orientation in the (200) plane on the glass substrate. The chemical analysis of the surfaces by XPS reveals that in the surfaces of the deposited layers are several oxidized chemical species such as Ta2O5, TaOxNy TaxOy due to Ta is a very reactive metal and is readily oxidized even at low partial pressures as for our synthesis conditions. Characterization by Scanning Electron Microscopy reveals that the microstructure of the films was homogeneous with small clusters size and a cauliflower type, also the films exhibit the typical columnar growth for films deposited by PVD techniques, following the growth of zone I described by the model developed by Movchan and Demchisin and Thornton. Biomimetic method was used to evaluate the bioactivity in all surfaces which involves immersing the thin films in simulated body fluid (SBF) to promote the deposition of calcium phosphates, two concentrations were used to assess qualitatively which could deposit the stoichiometric calcium phosphate hydroxyapatite and make it more efficiently. The SBF 1.5 enriched in Ca2 + and PO43- ions was chosen. A new layer was deposited upon the surfaces and it was determined by XRD, FTIR and XPS that crystalline Hydroxyapatite phase was formed, so that all our surfaces have the ability to form apatite spontaneously after an immersion period of three weeks. The mechanism of deposition of HAp involves the formation of small amounts of Ta-OH groups by a hydration of the tantalum oxide passive layer on its surface. To study biocompatibility properties, films were placed in cell culture containing osteoblasts, all surfaces exhibit cell adhesion and formation of filipodia. Whereas one of the main problems of bone implants is biofilm formation caused by bacterial colonization, tests were made with the bacterium Pseudomonas Aeruginosa, which is a major human opportunistic pathogens in surgical procedures, causing infections in soft tissue, bones, among others. This assay allowed us to know how the different surfaces react when exposed to this bacteria, Titanium had greater growth of P. aeruginosa and biofilm formation in all periods of study, while Ta surfaces showed the lowest activity of biofilm formation. Mesoporous silica thin films where used as bactericidal agents, and it was found by MEB that no microbial colonization or biofilm formation occur on these surfaces
Bradley, Kieren Adam. "Photoelectrochemistry of nanostructured semiconductors." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687604.
Full textSmith, Steven P. "Lanthanide-containing Nanostructured Materials." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145459.
Full textFavaro, Matteo. "Nanostructured flexible radiation sensors." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/310045.
Full textFavaro, Matteo. "Nanostructured flexible radiation sensors." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/310045.
Full textIsotta, Eleonora. "Nanostructured thermoelectric kesterite Cu2ZnSnS4." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/315174.
Full textIsotta, Eleonora. "Nanostructured thermoelectric kesterite Cu2ZnSnS4." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/315174.
Full textSaba, Johan. "Electrodéposition de polymère conducteur électronique sur des fibres de carbone greffées de nanotubes de carbone." Thesis, Cachan, Ecole normale supérieure, 2012. http://www.theses.fr/2012DENS0073.
Full textThis thesis is part of the ANR project “PROCOM” from the Mat&Pro program whose coordinator is EADS IW. The aim of the project is the development of a process likely to be scaled up industrially to produce fibrous reinforcements for high performance composites. The project incorporates new concepts in nano / micro-scale and an electrochemical surface treatment. This PhD work presents the synthesis of an electronically conductive polymer (polypyrrole) by an electrochemical route, on the surface of hybrid reinforcements which are carbon fibers grafted by carbon nanotubes (CNTs). At first, the polymer synthesis has been optimized and the influence of different electrochemical parameters on the doping level and the thickness of the polymer layer was investigated. The parameters studied were the applied potential, the polymerization time, the nature of the electrolyte and the dopant. Then, the influence of polymer deposition on three very important parameters was considered. These parameters are the electrical conductivity, the mechanical properties and the adhesion of CNTs on the surface of the carbon fibers. The electrical properties are important because these composites are intended to be used for the fuselage of aircraft that must be able to dissipate the current from lightning. Good intrinsic electrical properties of CNTs and the use of a conductive polymer have improved the conductive properties of reinforcements. The polymer, which is at the interface between the reinforcing hybrid fibers and the matrix, is expected to improve the mechanical properties of the final material. However, to improve this interface different pre-treatments were carried out, such as heat treatment, plasma surface functionalization and incorporation of a grafting layer. Finally, the polymer plays a protective role in the dissemination of CNTs in the atmosphere in order to avoid any health risk. In a second step, a system for the electropolymerization of hybrid fibers in continuous was implemented with the aim of developing an industrially scalable process
Anand, Aman Roberts James Andrew. "Studying interactions of gas molecules with nanomaterials loaded in a microwave resonant cavity." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-4009.
Full textYiu, Wing-ching James, and 姚穎貞. "Synthesis of one-dimensional tungsten oxide nano-structures by thermalevaporation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B32047770.
Full textYe, Yueping. "Microstructure and properties of epoxy/halloysite nanocomposite /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20YE.
Full textStolk, Jonathan Douglas. "Development of low thermal expansion, high conductivity nanocomposites /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full textKariuki, Nancy N. "Nanostructured materials for electroanalytical applications." Diss., Online access via UMI:, 2005.
Find full textAssfour, Bassem. "Hydrogen Storage In Nanostructured Materials." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-65858.
Full textKubo, Shiori. "Nanostructured carbohydrate-derived carbonaceous materials." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5315/.
Full textNanoporöse 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.
Melberg, Brita. "Nanostructured surfaces with patterned wettability." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19410.
Full textStannard, Andrew David. "Pattern Formation in Nanostructured Systems." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523471.
Full textKrishnan, Jagadamma Lethy. "Characterisation of nanostructured light emitters." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=17192.
Full textReiman, Kenneth Helmut. "Nanostructured eletrodes for battery applications." Thesis, University of Southampton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500855.
Full textHuang, C. "Atom diffractometry from nanostructured surfaces." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604697.
Full textKuzume, Akiyoshi. "Electron transfer at nanostructured interfaces." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402324.
Full textAl-Aaraji, Mohammed. "Nanostructured ferroelectric ceramics and coatings." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/nanostructured-ferroelectric-ceramics-and-coatings(fee6c466-fce3-40f1-806a-2f26ecacdf82).html.
Full textHeffernan, Shane. "Nanostructured CU₂O solar cells." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709220.
Full textGordon, Jeremy B. "Thermorheological properties of nanostructured dispersions." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39866.
Full textIncludes bibliographical references (p. 143-149).
Nanostructured dispersions, which consist of nanometer-sized particles, tubes, sheets, or droplets that are dispersed in liquids, have exhibited substantially higher thermal conductivities over those of the liquids alone. While it is desirable to synthesize a fluid that has improved heat transfer characteristics, it is necessary that the viscosity remain low, so as not to appreciably increase the pumping power needed to employ these fluids in "real world" applications. To this end, the theological and thermal properties of twenty-six different nanostructured dispersions were examined. In terms of rheometry, both steady flow and creep tests were employed, while the transient hot wire technique was utilized to perform measurements of the thermal conductivity of each fluid. Characterization of the dispersed phase was completed using dynamic light scattering and transmission electron microscopy. In particular, the dispersion properties examined were nanostructure material, nanoparticle size, base fluid material, nanostructure concentration, and presence of a surfactant. It was observed that several of the fluids or nanopowders obtained from commercial manufacturers either contained no particles, had the presence of a relatively large proportion of water in ethylene glycol-based fluids, or were composed of particles with sizes far in excess of those claimed by the manufacturer.
(cont.) Ultimately, it was determined that while most of the fluids studied demonstrated Newtonian or slightly shear thinning behavior, several of the fluids exhibited undesirable yield stresses that could be attributed to the formation of a network structure of aggregated nanoparticles. However, it was observed that the addition of a surfactant helped to keep the nanoparticles from clustering to the same degree, thereby eliminating the presence of a yield stress, and reducing the viscosity of the fluid over the entire range of shear rates. The surfactant also contributed to an increase in thermal conductivity enhancement, thereby producing a highly desirable behavior.
by Jeremy B. Gordon.
S.M.
Ahn, Edward Sun 1972. "Nanostructured apatites as orthopedic biomaterials." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8627.
Full textIncludes bibliographical references.
Historically, using suitable mechanical replacements for bone has been a priority in designing permanent, load-bearing orthopedic implants. As a result, the biomaterials used in these implants have been largely limited to bioinert titanium-based alloys, as well as to polycrystalline alumina and zirconia ceramics. However, analysis of implants incorporating these traditional biomaterials indicated that most failures involved an unstable implant-tissue interface and/or a mismatch of the mechanical behavior of the implant with the surrounding tissues. As a result, up to 20% of patients receiving permanent, load-bearing implants may undergo a revision operation. The objective of this research was to develop an alternative biomaterial that combined both mechanical resilience and an osteoconductive surface to provide a stable interface with the surrounding connective tissue so that the need for revision operations may be significantly reduced. In the effort to address the issue of mechanical strength and bioactivity simultaneously, hydroxyapatite (HAP) has generated considerable interest. Though a commonly used bioceramic, HAP has been limited by its processability. This material is sensitive to non-stoichiometry and impurities during synthesis and processing due to its complex composition and crystal structure (Ca10(P04)6(OH)2, P63/m).
(cont.) Consequently, conventionally processed HAP materials lack phase purity and homogeneity. Densification of HAP requires high temperatures that result in grain growth and decomposition into undesired phases with poor mechanical and chemical stability. To circumvent densification at high temperatures, glassy additives have been introduced to promote liquid-phase sintering at a lower temperature. However, the presence of a secondary glassy phase gave rise to poor mechanical characteristics. Hence, clinical applications of HAP have been limited to powders, coatings, porous bodies, and non-load-bearing implants. To overcome the deficiencies of conventionally processed HAP, nanostructure processing was applied, which allowed for materials design from the molecular level. By using an aqueous chemical precipitation technique, a fully dense, transparent, nanostructured HAP-based bioceramic that exhibited superior mechanical properties and enhanced tissue bonding was obtained. Processing parameters affecting the molecular and structural development of HAP were used to tailor HAP stoichiometry, crystallite size, morphology and surface chemistry for optimal thermal stability and sinterability. Unlike conventionally processed HAP, the stoichiometric, equiaxed, nanocrystalline HAP powders demonstrated significantly enhanced sinterability by fully densifying at a remarkably low temperature of 900ʻC with pressure-assisted sintering.
(cont.) Furthermore, high-resolution electron micrographs illustrated that the sintered compact possessed a uniform and ultrafine microstructure with an average grain size of -100 nm, with no glassy or amorphous interfaces along the grain boundaries. The crystallinity of the HAP grains and grain boundaries and the minimal flaw sizes could be credited for the superior strength of nanostructured HAP compared to conventional HAP. Compared to polycrystalline HAP, nanocrystalline HAP also provided greater osteoblast function. In vitro experiments indicated that nanocrystalline HAP surfaces enhanced cell attachment, proliferation and mineralization. The larger grain boundary volume resulting from the ultrafine microstructure might have enhanced protein adsorption, ...
by Edward Sun Ahn.
Ph.D.
Clavel, Guylhaine. "Magnetic impurities in nanostructured materials." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/3210.
Full textOs resultados apresentados aqui foram alcançados no âmbito do programa de doutoramento intitulado “Impurezas Magnéticas em Materiais Nanoestruturados”. O objectivo do estudo foi a síntese e caracterização de óxido contendo impurezas magnéticas. Durante este trabalho, sínteses de sol-gel não-aquoso têm sido desenvolvidos para a síntese de óxidos dopados com metais de transição (ZnO e ZrO2). A dopagem uniforme é particularmente importante no estudo de semicondutores magnéticos diluídos (DMSs) e o ponto principal deste estudo foi verificar o estado de oxidação e a estrutura local do dopante e para excluir a existência de uma fase secundária como a origem do ferromagnetismo. Para alargar o âmbito da investigação e explorar plenamente o conceito de "impurezas magnéticas em materiais nanoestruturados" estudamos as propriedades de nanopartículas magnéticas dispersas em uma matriz de óxido. As nanopartículas (ferrita de cobalto) foram depositadas como um filme e cobertas com um óxido metálico semicondutor ou dielétrico (ZnO, TiO2). Estes hetero-sistemas podem ser considerados como a dispersão de impurezas magnéticas em um óxido. As caracterizações exigidas por estes nanomateriais têm sido conduzidas na Universidade de Aveiro e Universidade de Montpellier, devido ao equipamento complementar.
The results presented here have been achieved under the PhD program entitled “Magnetic Impurities in Nanostructured Materials”. This study had as purpose the synthesis and characterization of oxidic semiconductor containing magnetic impurities. During this work we have developed non-aqueous sol-gel routes, leading to well controlled oxide nanomaterials, to the synthesis of transition-metal doped oxides (ZnO and ZrO2). Homogeneous doping is particularly important in the comprehensive study of diluted magnetic semiconductors (DMSs), and the main point of this study was to ascertain the oxidation state and local structure of the dopant, as well as to exclude the existence of secondary phase as the origin of ferromagnetism. To enlarge the field of research and fully explore the concept of “magnetic impurities in nanostructured materials” we have studied the magnetic properties of nanoparticles embedded in an oxide matrix. The nanoparticles (cobalt ferrite) were deposited as a film and coated by a semiconducting or dielectric metal oxide (ZnO, TiO2). These hetero-systems can be regarded as dispersion of magnetic impurities in oxides. The characterizations needed by these nanomaterials were performed at the University of Aveiro and University of Montpellier because of complementary available equipments.
Li, Guangru. "Nanostructured materials for optoelectronic devices." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/263671.
Full textGherbaz, Gabriele. "Nanostructured polymers : morphology and properties." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/66593/.
Full textZhu, Ronghua (Richard). "Atomistic Simulation of Nanostructured Materials." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164059775.
Full text