Дисертації з теми "Nanocrystals composite material"
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Cozzarini, Luca. "Nanomaterials based on II-VI Semiconductors." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7359.
Повний текст джерелаThis thesis describes: (i) synthesis and characterization of colloidal nanocrystals of II-VI semiconductor compounds; (II) development of two novel materials using such nanocrystals as “building blocks”: (IIa) a nanocrystals/polymer composite, to be used as phosphor in LED-based lighting devices; (IIb) an inorganic, nano-structured multiphase material, showing a promising geometry as an electronic intermediate band material. Different typologies of nanocrystals (single-phase, alloyed or core-shells) were successfully synthesized using air-stable, safe reagents. Their optical properties (absorption spectrum, fluorescence wavelength and fluorescence quantum yield) were mapped as function of different parameters. Good results in engineering optical properties were achieved by: (a) changing size and/or composition in single-phase nanocrystals; (b) tuning shell composition and thickness and/or mutually diffusing one material into the other in multi-phase nanocrystals. The influence of different surface ligands on optical properties and on solubility in different media was also studied. Nanocrystal/polymer composite lenses were obtained from nanocrystals with desired fluorescence wavelength and quantum yield, mixed in an appropriate solvent with polymer pellets. The mixture was drop casted or tape casted on a solid substrate, obtaining solid, transparent lenses after solvent evaporation. A nano-structured, all-inorganic material (composed of semiconducor nanocrystals embedded into a wider bandgap semiconductor) was obtained through self-assembly and densification of colloidal core-shells nanocrystals. The realization of this composite supracrystal was achieved via a multi-step process: (i) colloidal synthesis of core-shell nanocrystals; (ii) surface ligands exchange; (iii) assembly; (iv) heat treatment. Evolution of the optical properties during heat treatment suggests that it is possible to sinter the shell material without altering the internal nano-heterostructure, if temperature and time of the treatment are controlled properly.
In questa tesi sono descritti: (I) la sintesi colloidale e la caratterizzazione di nanocristalli di semiconduttori II-VI; (II) lo sviluppo, utilizzando i suddetti nanocristalli quali “unità da costruzione”, di due materiali innovativi: (IIa) un composito nanocristalli/polimero, da usare come fosforo in dispositivi per illuminazione basati su LED; (IIb) un materiale inorganico nano-strutturato multifase, con una geometria promettente quale materiale a banda elettronica intermedia. Differenti semiconduttori II-VI sono stati sintetizzati in forma di nanocristalli (monofasici, in forma di lega o in struttura di tipo “core-shell”) usando reagenti sicuri e stabili in atmosfera. Le loro proprietà ottiche (spettro di assorbimento, lunghezza d’onda di fluorescenze e resa quantica di fluorescenza) sono state mappate in funzione di numerosi parametri. Sono stati raggiunti ottimi risultati nel controllo delle proprietà ottiche sia in nanocristalli a fase singola (modificandone le dimensioni o la composizione chimica) che in nanocristalli multifase (regolandone la composizione e lo spessore della “shell”, nonché mutualmente diffondendo un materiale nell’altro). È stata anche studiata l’influenza di differenti leganti superficiali sulle proprietà ottiche e sulla solubilità dei nanocristalli in differenti solventi. Lenti composite di nanocristalli/polimero sono state ottenute a partire da nanocristalli aventi la lunghezza d’onda e la resa quantica di fluorescenza desiderate, mescolandoli con pellet di polimero in solventi appropriati. La miscela è stata depositata su un supporto, tramite drop casting o tape casting, ottenendo lenti solide trasparenti dopo l’evaporazione del solvente. Un materiale inorganico nano strutturato (costituito da nanocristalli di semiconduttore racchiusi all’interno di un secondo materiale semiconduttore a bandgap maggiore) è stato ottenuto tramite l’autoassemblaggio e la densificazione di nanocristalli core-shell sintetizzati con procedure di chimica colloidale. La realizzazione di suddetto sovra-cristallo si è svolta in più fasi: (i) sintesi colloidale; (ii) sostituzione dei leganti superficiali; (iii) assemblaggio; (iv) trattamento termico. I risultati derivanti dallo studio dell’evoluzione delle proprietà ottiche durante il trattamento termico suggeriscono che sia possibile sinterizzare il materiale della shell senza alterare la nano-eterostruttura interna, se la temperatura e il tempo del trattamento sono scelti opportunamente.
XXIV Ciclo
1983
Lee, Jinwook 1966. "Semiconductor nanocrystal composite materials and devices." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8039.
Повний текст джерелаIncludes bibliographical references.
This thesis describes the synthesis and characterization of semiconductor nanocrystal (quantum dot, QD) embedded composite materials and possible device applications of the resulting luminescent materials. Chemically synthesized ZnS overcoated CdSe, (CdSe)ZnS, QDs are incorporated into a polymer host material. The main challenge in the preparation of QD-polymer composites is the prevention of both phase separation and aggregation of the QDs within the polymer host material, while sustaining the original quantum efficiency of the QDs in their growth solution. Possible ways to incorporate QDs into an optically clear polymer matrix are considered. A guideline for a successful QD-polymer composite is discussed for various polymer systems: ligand polymers, ligand monomer and covalent bonding to a polymer matrix, and in-situ polymerization. The best composite system is based on incorporation of QDs into a poly(laurylmethacrylate) matrix during in-situ polymerization in the presence of TOP ligands. The successful incorporation of QDs into a polymer host material demonstrates the ability to form QD-polymer composite light emitting materials. The emission spans nearly the entire region of saturated and mixed colors with narrow emission profiles. The light emission spectra of QD-polymer composites excited by a blue diode light are also simulated by Monte Carlo methods and compared to the measured spectra from actual devices. The synthesis and characterization of QD-microspheres, which can be used as active fluorescent building blocks, are also described.
(cont.) In order to enhance the stability and compatibility of QDs in a polymer microsphere, the QDs are treated with polymerizable phosphine ligands, small oligomeric phosphine methacrylate (SOPM), and the following homogeneous solution polymerization is investigated to form monodisperse QD-microspheres. The QD-microspheres can store optical information assigned by embedded QDs in multiple codes. The surface functionalization of these capsules could provide a means for attaching capsules to surfaces and allow capsules to assemble into 3D structures.
by Jinwook Lee.
Ph.D.
Way, Amanda E. "Stimuli-Responsive Nanofiber Composite Materials: From Functionalized Cellulose Nanocrystals to Guanosine Hydrogels." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1390388160.
Повний текст джерелаSeregin, Vladimir Victor. "Part I, Fabrication and surface modification of composite biomaterials based on silicon and calcium disilicide Part II, Synthesis and characterization of erbium doped silicon nanocrystals encapsulated by aluminum and zinc oxides /." Fort Worth, Tex. : Texas Christian University, 2006. http://etd.tcu.edu/etdfiles/available/etd-04252006-145309/unrestricted/seregin.pdf.
Повний текст джерелаBerkowitz, Kyle Matthew. "Characterization and Analysis of Shape Memory Polymer Composites With Cellulose Nanocrystal Fillers." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1396526722.
Повний текст джерелаAngellier, Hélène. "Nanocristaux d'amidon de maïs cireux pour applications composites." Phd thesis, Université Joseph Fourier (Grenoble), 2005. http://tel.archives-ouvertes.fr/tel-00010699.
Повний текст джерелаKehrle, Julian [Verfasser], Bernhard [Akademischer Betreuer] Rieger, Johann Peter [Gutachter] Plank, and Bernhard [Gutachter] Rieger. "Surface Hydrosilylation: The Key to Silicon Nanocrystal Hybrid and Composite Materials / Julian Kehrle ; Gutachter: Johann Peter Plank, Bernhard Rieger ; Betreuer: Bernhard Rieger." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1170321615/34.
Повний текст джерелаSonseca, Olalla Agueda. "DEVELOPMENT OF SHAPE-MEMORY COMPOSITES BASED ON A BIODEGRADABLE POLYESTER ELASTOMER." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/54129.
Повний текст джерела[ES] La presente tesis doctoral, se centra en el desarrollo y caracterización de nuevos nanocompuestos biodegradables, a partir de matrices de poli(mannitol sebacato) (PMS) con propiedades a medida y capacidades de memoria de forma para aplicaciones biomédicas. Dos tipos de cargas -nanocristales de celulosa (CNC) y nanofibras de ácido poliláctico (NF-PLA) obtenidas mediante electrospinning- se han utilizado como refuerzo, con la finalidad de inducir y/o mejorar las propiedades de memoria de forma en matrices de PMS. Se han estudiado y evaluado diferentes tratamientos de curado y ratios de reacción entre el mannitol y ácido sebácico (1:1 y 1:2), con la finalidad de obtener muestras con bajo y alto grado de reticulación. Una combinación adecuada del tratamiento de curado y el ratio entre monómeros del PMS, así como la adición de bajos contenidos de CNC, permitió desarrollar nanocompuestos de PMS/CNC con un amplio rango de propiedades mecánicas y perfiles de degradación. Por otro lado, se han producido mats de nanofibras de ácido poliláctico (PLA) con alta orientación mediante la técnica de electrospinning, para embeberse en matrices de PMS, observándose una mejora de hasta 53 veces en el módulo de Young para nanocompuestos de PMS/NF-PLA con un 15% en peso de nanofibras. La incorporación de cargas (CNC y NF-PLA) permitió el desarrollo de nanocompuestos con memoria de forma activada térmicamente, con una mejora de parámetros tales como la fuerza de recuperación y la capacidad de fijación. Los nanocompuestos reforzados con NF-PLA obtenidas por electrospinning, ofrecieron el mejor balance de propiedades mecánicas y térmicas, así como un mayor control de la temperatura de transición para la activación del cambio de forma en un intervalo útil de temperaturas. Por todo ello, estos materiales pueden resultar de interés como sistemas activos en aplicaciones biomédicas de larga duración.
[CAT] La present tesi doctoral se centra en el desenvolupament i caracterització de nous nanocompostos biodegradables a partir de matrius de poli(mannitol sebacato) (PMS) amb propietats a mesura i capacitats de memòria de forma per a aplicacions biomèdiques. Dos tipus de càrregues -nanocristals de cel·lulosa (CNC) i nanofibres d'àcid polilàctic (NF-PLA) obtingudes mitjançant electrospinning- s'han utilitzat com a reforç amb la finalitat d'induir i/o millorar les propietats de memòria de forma en matrius de PMS. S'han estudiat i avaluat diferents tractaments de curat i ràtios de reacció entre el mannitol i àcid sebàcic (1:1 i 1:2) amb la finalitat d'obtenir mostres amb baix i alt grau de reticulació. Una combinació adequada del tractament de curat i el ràtio entre monòmers del PMS, així com l'addició de baixos continguts de CNC, va permetre desenvolupar nanocompostos de PMS/CNC amb un ampli rang de propietats mecàniques i perfils de degradació. D'altra banda, s'han produït mats de nanofibres d'àcid polilàctic (PLA) amb alta orientació mitjançant la tècnica de electrospinning, per embeure's en matrius de PMS, observant-se una millora de fins a 53 vegades en el mòdul de Young per nanocompostos de PMS/NF-PLA amb un 15% en pes de nanofibres. La incorporació de càrregues (CNC i NF-PLA) va permetre el desenvolupament de nanocompostos amb memòria de forma activada tèrmicament, amb una millora de paràmetres tals com la força de recuperació i la capacitat de fixació. Els nanocompostos reforçats amb NF-PLA obtingudes per electrospinning, van oferir el millor balanç de propietats mecàniques i tèrmiques, així com un major control de la temperatura de transició per a l'activació del canvi de forma en un interval útil de temperatures. Per tot això, aquests materials poden resultar d'interés com a sistemes actius en aplicacions biomèdiques de llarga durada.
Sonseca Olalla, A. (2015). DEVELOPMENT OF SHAPE-MEMORY COMPOSITES BASED ON A BIODEGRADABLE POLYESTER ELASTOMER [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54129
TESIS
Wang, Qi. "Electrochemical synthesis of CeO2 and CeO2/montmorillonite nanocomposites." Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4378/.
Повний текст джерелаGuidetti, Giulia. "Cellulose photonics : designing functionality and optical appearance of natural materials." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277918.
Повний текст джерелаDas, Shyamashis. "Materials Chemistry in Search of Energy Materials : Photovoltaics and Photoluminescence." Thesis, 2016. http://hdl.handle.net/2005/2820.
Повний текст джерелаVenkataraman, B. Harihara. "Multifunctionalities Of Ceramics And Glass Nanocrystal Composites Of V2O5 Doped Aurivillius Family Of Ferroelectric Oxides." Thesis, 2005. http://etd.iisc.ernet.in/handle/2005/1424.
Повний текст джерела(8738436), Md Nuruddin. "Molecular Transportation in Polymer and Composite Materials: Barrier Performance and Mechanical Property Evaluation." Thesis, 2020.
Знайти повний текст джерелаTransport of gasses and liquids through polymers and composites is an important factor to be considered when designing a material for structure and packaging applications. For structural engineering applications, more focus has been given to the transportation of water, vapor and organic liquids rather than gases as diffusion of these liquids into the polymers and polymer-based composites can significantly lower service life. In addition, much attention has been given to the leaching of unreacted reactant molecules, solvents, additives, degradation products from the polymers and composites to the atmosphere (water, soil etc.). We studied the transport of volatile organic compounds and water in cured-in-place-pipe (CIPP) (a representative of FRPC) and gas permeability of highly engineered cellulose nanocrystals (CNC) films.
Cured-in-place-pipe (CIPP) is a popular technology which uses fiber reinforced polymer composite to repair sanitary sewer, stormwater, and drinking water pipe. The liner is installed in the field and exposed to flowing water immediately after installation (curing of the liner) is done. Curing conditions dictate liner properties as undercured liners can contain unreacted styrene monomers, additives, degradation products. These agents can leach out and enter the environment (soil, water, air). The objective of this work was to investigate the curing behavior, volatile content, thermal stability of steam-cured and UV-cured CIPP liners collected from Indiana and New York installation sites. The liner specimens were also exposed to water and other aggressive environmental conditions (saltwater, concrete pore solution at 50 °C) to explore the leaching of unreacted styrene and other organic chemicals from the liners. The influence of transportation of water, salt solution and pore solution through liners on mechanical and thermo-mechanical properties was also examined to study the durability of the liners. Study suggested that the durability of the liners depends on the curing condition and exposed environment conditions.
The function of polymer packaging materials is mainly to inhibit gas and moisture permeation through the films. Cellulose nanocrystals (CNCs) have drawn growing interest for the packaging due to their non-toxicity, abundance in nature, biodegradability and high barrier properties. The objective of this work was to corelate the alignment of CNC with free volume and barrier performance of the film. Furthermore, citric acid (CA) was added to the CNC suspensions with varying quantity to explore the effect of CA on coating quality and barrier performance of CNC coated polypropylene (PP) film. Study revealed that CA addition in CNC suspension can enhance the hydrophobicity and gas barrier performance of coated PP films while retaining the high optical transparency.
Abreu, Beatriz Martins de. "Bio-inspired nanocellulose composites systems with structural coloration as optical security features." Master's thesis, 2019. http://hdl.handle.net/10362/91293.
Повний текст джерелаBahrig, L., Stephen G. Hickey, and A. Eychmüller. "Mesocrystalline materials and the involvement of oriented attachment - a review." 2014. http://hdl.handle.net/10454/10422.
Повний текст джерелаThe latest advances in mesocrystal formation and non-classical crystallization of pre-synthesised nanoparticles have been reviewed with the focus on providing a fuller description of a number of complex systems and their properties and applications through examination of the crystallisation mechanisms at work. Two main crystallization principles have been identified; classical crystallization and particle based aggregation modes of non-classical pathways. To understand the non-classical pathways classical crystallization and its basics are introduced before non-classical pathways, such as oriented attachment and mesocrystal formation, are examined. In particular, the various destabilization mechanisms as applied to the pre-synthesized building blocks in order to form mesocrystalline materials as well as the interparticular influences providing the driving forces are analyzed and compared to the mechanisms at work within classical crystallization. Furthermore, the new properties of the mesocrystalline materials that derive from the collective properties of the nanoparticular building units, and their applications potential are presented. It is shown that this new class of materials has the potential to impact in a number of important areas such as sensor applications, energy conversion, photonic crystals as well as for energy storage, optoelectronics and heterogeneous catalysis or photocatalysis.
Paramesh, Gadige. "Investigations into the Structural and Physical Properties of Li2O-M2O-2B2O3 (M=Li, Na & K), BaO-TiO2-B2O3 and 2Bi2O3-B2O3 Glass Systems." Thesis, 2013. http://etd.iisc.ernet.in/2005/3356.
Повний текст джерела(6631748), Shikha Shrestha. "Effect of nanocellulose reinforcement on the properties of polymer composites." Thesis, 2019.
Знайти повний текст джерелаPolymer nanocomposites are envisioned for use in many advanced applications, such as structural industries, aerospace, automotive technology and electronic materials, due to the improved properties like mechanical strengthening, thermal and chemical stability, easy bulk processing, and/or light-weight instigated by the filler-matrix combination compared to the neat matrix. In recent years, due to increasing environmental concerns, many industries are inclining towards developing sustainable and renewable polymer nanocomposites. Cellulose nanomaterials (CNs), including cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), have gained popularity due to their excellent mechanical properties and eco-friendliness (extracted from trees, algae, plants etc.). However, to develop CN-reinforced nanocomposites with industrial applications it is necessary to understand impact of hygroscopic swelling (which has very limited quantitative study at present), aspect ratio, orientation, and content of CNs on the overall performance of nanocomposites; and overcome the low dispersibility of CNs and improve their compatibility with hydrophobic matrix. In this work, we attempt to understand the influence of single nanocrystals in the hygroscopic and optical response exhibited by nanostructured films; effect of CNCs on the properties of PVA/CNC fibers by experimental evidence with mathematical modeling predictions; and hydrophobized CNFs using a facile, aqueous surface modification to improve interfacial compatibility with epoxy.
To evaluate the effect of CNC alignment in the bulk response to hygroscopic expansion, self-organized and shear-oriented CNC films were prepared under two different mechanisms. The coefficient of hygroscopic swelling (CHS) of these films was determined by using a new contact-free method of Contrast Enhanced Microscopy Digital Image Correlation (CEMDIC) that enabled the characterization of dimensional changes induced by hygroscopic swelling of the films. This method can be readily used for other soft materials to accurately measure hygroscopic strain in a non-destructive way. By calculating the CHS values of CNC films, it was determined that hygroscopic swelling is highly dependent on the alignment of nanocrystals within the films, with aligned CNC films showing dramatically reduced hygroscopic expansion than randomly oriented films. Finite element analysis was used to simulate moisture sorption and kinetics profile which further predicted moisture diffusion as the predominant mechanism for swelling of CNC films.
To study the effects of different types and aspect ratios of CNCs on mechanical, thermal and morphological properties of polyvinyl alcohol (PVA) composite fibers, CNCs extracted from wood pulp and cotton were reinforced into PVA to produce fibers by dry-jet-wet spinning. The fibers were collected as-spun and with first stage drawing up to draw ratio 2. The elastic modulus and tensile strength of the fibers improved with increasing CNC content (5 – 15 wt. %) at the expense of their strain-to-failure. The mechanical properties of fibers with cotton CNC were higher than the fibers with wood CNC when the same amount of CNCs were added due to their higher aspect ratio. The degree of orientation along the spun fiber axis was quantified by 2D X-ray diffraction. As expected, the CNC orientation correlates to the mechanical properties of the composite fibers. Micromechanical models were used to predict the fiber performance and compare with experimental results. Finally, surface and cross-sectional morphologies of fibers were analyzed by scanning electron microscopy and optical microscopy.
To improve the dispersibility and compatibility of CNFs with epoxy, CNFs were modified by using a two-step water-based method where tannic acid (TA) acts as a primer with CNF suspension and reacts with hexadecylamine (HDA), forming the modified product as CNF-TA-HDA. The modified (-m) and unmodified (-um) CNFs were filled into hydrophobic epoxy resin with a co-solvent (acetone), which was subsequently removed to form a solvent-free two component epoxy system, followed by addition of hardener to cure the resin. Better dispersion and stronger adhesion between fillers and epoxy were obtained for m-CNF than the um-CNF, resulting in better mechanical properties of nanocomposites at the same loading. Thermal stability and the degradation temperature of m-CNF/epoxy improved when compared to neat epoxy.
Majhi, Koushik. "Transparent Glass Nono/Microcrystal Composites In MO-Bi2O3-B2O3(M= Sr, Ca) System And Their Physical Properties." Thesis, 2009. http://hdl.handle.net/2005/1062.
Повний текст джерелаAhamad, M. Niyaz. "Multifunctionalities Of Telllurite And Borate Based Glasses Comprising Nano/Micro Crystals Of Tetragonal Tungsten Bronze-Type Ferroelectric Oxides." Thesis, 2009. http://hdl.handle.net/2005/1004.
Повний текст джерелаKarthik, C. "Investigations Into The Synthesis, Structural And Dielectric Properties Concerning The Relaxor Behavior Of n=2 Members Of The Aurivillius Family Of Oxides." Thesis, 2007. http://hdl.handle.net/2005/686.
Повний текст джерелаShet, Tukaram. "Investigations into the Microstructure Dependent Dielectric, Piezoelectric, Ferroelectric and Non-linear Optical Properties of Sr2Bi4Ti5O18 Ceramics." Thesis, 2017. http://hdl.handle.net/2005/3269.
Повний текст джерелаDas, Mahua. "Thin Films Of A Carbonaceous Copper Oxide, Li Doped Cobalt Oxide And Li At Nanometric Dimension : Synthesis Through CVD, Solgel And Electromagnetic Irradiation And Characterisation." Thesis, 2007. http://hdl.handle.net/2005/619.
Повний текст джерелаViswanath, B. "Understanding The Growth And Properties Of Functional Inorganic Nanostructures : An Interfacial Approach." Thesis, 2008. http://hdl.handle.net/2005/785.
Повний текст джерелаLal, Nidhi. "Interfacing Biomolecules with Nanomaterials for Novel Applications." Thesis, 2014. http://hdl.handle.net/2005/3222.
Повний текст джерела