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1
Acquadro, Julien. "Étude des propriétés tribologiques et électriques de revêtements sol-gel comme alternative anticorrosion au cadmium et au chrome hexavalent pour la connectique en environnements sévères." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST150.
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Le domaine de la connectique englobe l'ensemble des éléments permettant de réaliser des liaisons électriques entre différents composants. Dans les secteurs aéronautique et militaire, ces liaisons doivent être hautement fiables et fonctionner de manière optimale dans des environnements sévères. Ainsi, les contacts électriques des connecteurs sont généralement protégés par des boîtiers fabriqués en alliages d'aluminium, notamment l'alliage AA6061, qui doivent remplir les trois principales fonctions de conduction électrique, de tenue mécanique et de résistance à la corrosion. Actuellement, ces propriétés sont assurées par des revêtements de protection de surface à base de cadmium passivé au chrome (VI). Cependant, depuis 2017, cette solution n'est plus acceptable en Europe en raison de l'évolution des directives et réglementations RoHS et REACH, le cadmium et le chrome hexavalent étant tous deux très toxiques pour l'environnement et la santé humaine.Cette thèse s'inscrit dans un vaste programme de collaboration industrielle regroupant sept partenaires visant à développer et produire des revêtements de substitution au cadmium passivé au chrome (VI). Parmi les nombreuses approches explorées, la voie la plus innovante et prometteuse est celle des revêtements sol-gel rendus conducteurs par l'intégration de charges conductrices adaptées. La stratégie adoptée consiste à mettre en œuvre ces revêtements à l'échelle du laboratoire, puis à les tester sur des boîtiers de connecteurs soumis à des qualifications industrielles rigoureuses.L'objectif principal de cette thèse est de contribuer à une meilleure compréhension du rôle et de l'influence des différentes étapes d'élaboration des revêtements sur leurs propriétés de conduction, d'usure et d'anticorrosion. Les dépôts réalisés sur des éprouvettes modèles de laboratoire ont été étudiés aux échelles macroscopique et microscopique afin de déterminer les paramètres de synthèse optimaux, tels que les précurseurs, le taux d'hydrolyse, les conditions de maturation et les paramètres de dépôt. Ces paramètres ont été ajustés en fonction des propriétés physico-chimiques et structurelles des films formés. L'impact de la nature et de la quantité des charges conductrices, qu'elles soient carbonées ou métalliques, sur les propriétés de conduction, d'usure, de tenue mécanique et de protection contre la corrosion, a été rigoureusement évalué.Les résultats de ces études ont été comparés périodiquement aux résultats des tests de qualification réalisés sur des boîtiers industriels de formes complexes revêtus des mêmes formulations, permettant ainsi d'identifier les défis à surmonter pour atteindre les propriétés requises en termes de conduction électrique, de tenue mécanique et de résistance à la corrosion. Ces travaux offrent également des perspectives de développement pour l'avenir de cette technologie dans le domaine de la connectiqueConnector technology involves the components that create electrical connections between different systems. In critical sectors such as aerospace and military, these connections must be highly reliable and able to perform under harsh conditions. Therefore, the electrical contacts within connectors are protected by housings made from aluminium alloys, like AA6061, which must meet three essential criteria: electrical conductivity, mechanical strength, and corrosion resistance. Currently, these properties are achieved through surface protection coatings based on cadmium passivated with hexavalent chromium (VI). However, since 2017, this solution has been deemed unacceptable in Europe due to evolving RoHS and REACH directives and regulations, given the severe toxicity of cadmium and hexavalent chromium to both the environment and human health.This thesis is part of a significant industrial collaboration involving seven partners focused on developing and producing coatings to replace cadmium passivated with chromium (VI). Among the various approaches explored, the most innovative and promising involves using sol-gel coatings made conductive through the incorporation of appropriate conductive fillers. The strategy entails implementing these coatings at the laboratory scale and subjecting them to rigorous industrial qualification tests on connector housings.This thesis aims to enhance understanding of how various stages in the development of coatings affect their properties related to electrical conduction, wear resistance, and anti-corrosion capabilities. Deposits applied to laboratory model specimens were studied at both macroscopic and microscopic scales to determine the optimal synthesis parameters. These parameters include sol-gel precursors, amount of water, maturation conditions, and deposition techniques, all of which are adjusted based on the physicochemical and structural properties of the resulting films. The influence of the type and quantity of conductive fillers, whether carbon-based or metallic, on properties such as electrical conduction, wear resistance, mechanical strength, and corrosion protection, was rigorously evaluated.Periodic comparisons were made between these study results and the outcomes of qualification tests conducted on industrially complex connector housings coated with the same formulations. This allowed the identification of challenges to overcome in achieving the necessary properties of electrical conduction, mechanical strength, and corrosion resistance. These efforts also provide development prospects for the future of this technology in the connector industry
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Oyharçabal, Mathieu. "Synthèse, formulation, et mise en oeuvre de nanomatériaux conducteurs base poly(aniline) / nanotubes de carbone pour des applications micro-ondes." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14633.
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Ces travaux de thèse consistent à formuler des nanocomposites électriquement conducteurs pour des applications micro-ondes. L’objectif principal est la mise en œuvre de matériaux absorbant les ondes radar, plus particulièrement sur la bande X (8-12 GHz). La polyaniline et les nanotubes de carbone, dispersés dans une matrice époxyde, ont été sélectionnés pour apporter les propriétés d’absorption aux fréquences visées. Différentes morphologies de polyaniline ont été synthétisées afin d’étudier leur influence sur les propriétés d’absorption des composites. L’utilisation d’une polyaniline à morphologie feuillet, présentant une forte anisotropie et un facteur de forme élevé, permet d’augmenter la conductivité et les pertes diélectriques des composites. De plus, leur association avec des nanotubes de carbone améliore significativement les propriétés d’absorption aux fréquences micro-ondes. Des écrans absorbants radar performants qui présentent des coefficients de réflexion inférieurs à -20 dB ont pu être modélisés et mis en œuvre, confirmant le potentiel de ces matériaux pour des applications de furtivité radarThis thesis deals with the formulation of electrically conductive nanocomposites for microwave applications. The main purpose is to process radar-absorbent materials, more particularly at the X band. (8-12 GHz). Polyaniline and carbon nanotubes, dispersed in an epoxyde matrix, have been selected. Different morphologies of polyaniline have been synthesized to study its impact on the absorption properties of composites. Using flake-like polyaniline showing high anisotropy and aspect ratio increases conductivity and dielectric losses of composites. Moreover, its association with carbon nanotubes significantly improves the absorption properties at microwaves frequencies. Efficient radar absorbing screens, showing reflection losses lower than -20 dB, have been calculated and processed confirming the potential of these materials for stealth applications
3
PAMMI, SRI LAXMI. "CARBON NANOCOMPOSITE MATERIALS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1069881274.
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Thomas, Michael David Ross. "Electrical phenomena in nanocomposite materials." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621926.
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Bobrinetskiy, I. I., A. Y. Gerasimenko, L. Ichkitidze, O. R. Khrolova, R. V. Morozov, V. M. Podgaetsky, and S. V. Selishchev. "Nanocomposite Materials for Cell Growth." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35452.
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We propose a development of carbon nanotube (CNT)/albumin nanocomposite for 2D and 3D tissue organization by cell growth. The adhesion and proliferation for neuroblastoma and fibroblast cells have been investigated on films based on CNT/bovine serum albumin (BSA) nanocomposite. Single-walled car-bon nanotube (SWNT)/BSA composites can be used as a substrate for cell growth of different kind. The layers of nanocomposite properties growing method based on laser radiation action. Investigations of sta-bility, an adhesion and internal structure of layers were performed. Stabilizing properties of the described laser method of manufacture (laser nanoforming) of layers may be associated with the ability to obtain nanotube frame work in composite structure under action of electric field of directed laser radiation. The presence of a such frame creates the conditions for self-assembly of biomedical tissues.
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Lee, Ji Hoon. "Tensegrity-inspired nanocomposite structures." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44839.
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The main goal of this research is to construct hierarchical microstructures from polymer nanocomposites. Specifically, the research focused on constructing tensegrity-inspired microstructure where the nanoparticles are the compression members and the polymer matrix is tensile web. In order to achieve the tensegrity-inpired microstruture, the research was conducted with the following objectives.
1. Synthesis of Hydroxyapatite (HAp) nanoparticles of controlled shapes using block copolymer templates.
2. Investigation of the effects of particle loadings and shapes on isotropic nanocomposite properties.
3. Construction of HAp building blocks into the tensegrity-inspired microstructures
First, in order to use the nanoparticles for this structure, needle-shaped HAp nanoparticles were synthesized using block copolymer templates. The results indicated that significant amount of polymer remained on particle surface. Since these particles were coated with polymer blocks, the decorated polymer blocks were considered as the interphase material which would be used to prestress the HAp nanoparticles, and the particles would be acted as the building blocks for constructing tensegrity-inspired microstructure. For nanocomposites, polymer coating on HAp nanoparticles promoted particle dispersion. The effect of particle shapes on thermomechanical properties did not show significant differences between the two particle systems due to their low aspect ratios and chemical similarity. However, the polymer crystallinity and crystallization showed different trend as a function of particle loadings in two particle systems, and the behavior was unified through a common particle spacing of approximately 120 nm. In order to investigate the effect of particle arrangement in the polymer matrix, needle-shaped HAp nanoparticles synthesized with two different block copolymers were mixed with different morphology of polymer matrices and manipulated particle arrangement using the drawing process. Nanocomposites prepared with different matrix morphologies showed the similar dispersion characteristics and reinforcement behavior. The experimental results showed the drawing process influenced the particle arrangement in the polymer matrix, and the particle arrangement and reinforcement behavior were influenced by polymer matrix morphology. The thermomechanical properties of both matrix systems enhanced through the drawing process in the glassy region, but the effect of degree of particle orientation was difficult to distinguish due to low aspect ratios of HAp particles which was not enough to impact on overall microstructure.
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Bera, Chandan. "Thermo electric properties of nanocomposite materials." Phd thesis, Ecole Centrale Paris, 2010. http://tel.archives-ouvertes.fr/tel-00576360.
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Cette thèse présente une étude théorique du transport de chaleur dans les matériaux composites nano poreux et nano fils ainsi qu'une étude théorique des propriétés thermoélectriques de l'alliage Si0:8Ge0:2 confrontée à des mesures expérimentales réalisées pour une partie, dans le cadre de l'étude.La première étude démontre que les alliages poreux affichent des réductions de conductivité thermique à des dimensions de pores beaucoup plus grandes que les matériaux poreux non alliés de même porosité nominale. Si on considère une taille de pores de 1000nm, la conductivité thermique de l'alliage Si0:5Ge0:5 avec 0:1 de porosité est deux fois plus faible que la conductivité thermique d'un matériau non poreux, alors que les pores plus petits que 100 nm sont nécessaires pour obtenir la même réduction relative dans le Si ou Ge pur. Nos résultats indiquent que les alliages nano poreux devraient être avantageux devant les matériaux nano poreux non alliés, et ceux pour les applications nécessitant une faible conductivité thermique, tels que les nouveaux matériaux thermoélectriques.La deuxième étude théorique sur la conductance thermique de nano fils révèle l'effet de la structure sur le transport des phonons. Avec un modèle théorique qui considère la dépendance en fréquence du transport des phonons, nous sommes en mesure quantitativement de rendre compte des résultats expérimentaux sur des nano fils droits et coudés dans la gamme de température qui montre qu'un double coude sur un fil réduit sa conductance thermique de 40% à la température de 5K. Enfin, nous avons procédé à une approche théorique des propriétés thermoélectriques des alliages SiGe frittés, en les comparant aux mesures expérimentales nouvelles et antérieures, tout en évaluant leur potentiel d'amélioration. L'approche théorique a été validée par comparaison de la mobilité prévue et la conductivité thermique prévues, en faisant varier la quantité de Ge et les concentrations de dopage, dans une gamme de température comprise entre 300 et 1000K. Nos calculs suggèrent qu'une optimisation par rapport à l'état de l'art actuel est possible pour le matériau de type n et type p, conduisant potentiellement à une augmentation de 6% (5%) du ZT _a 1000K et 25% (4%) _a température ambiante. Même des améliorations plus grandes devraient être possibles si la probabilité de diffusion des phonons aux joints de grains pouvait être augmentée au-delà de sa valeur actuelle de 10%.
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Yani, Yin. "Molecular dynamics simulation of nanocomposite materials." [Ames, Iowa : Iowa State University], 2009.
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Di, Carlo Lidia. "Nanocomposite cathodic materials for secondary cells." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17765.
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Hexagonales Wolframbronze (HTB)–FeF3·0.33H2O Xerogel und eine HTB– FeF3·0.33H2O/GO Nanoverbindung wurden zunächst durch einen fluorolytischen Sol-Gel Ansatz bei Raumtemperatur in MeOH erhalten und ihre elektrochemischen Eigenschaften bewertet. Operando Mössbauer Spektroskopie und Röntgendiffraktometrie (XRD) wurden verwendet, um den Mechanismus während der Reaktion mit Lithium zu untersuchen. Das Fluorid zeigte ein komplexes Verhalten und den strukturellen Zerfall der HTB Phase sowie eine allmähliche Umwandlung in Fe-F2–Rutil–ähnliche Nanodomänen, welche sich als Hauptkomponente im Verlaufe der Reaktion ausbildeten. Die XRD-Analyse bestätigte die Amorphisierung des elektroaktiven Materials. Die strukturelle Optimierung von HTB-FeF3·0.33H2O wurde durch eine mikrowellenunterstützte, fluorolytische Sol-Gel-Reaktion in Benzylalkohol erreicht. Das Verfahren ermöglichte die Synthese von phasenreinen Nanopartikeln mit einem Durchmesser von rund 30 nm, zusammen mit der Herstellung eines auf reduziertem Graphenoxid (RGO) basierten Nanokomposits bei verminderter Reaktionszeit. Die Abscheidung auf leitfähigem RGO erwies sich als vorteilhaft für die elektrochemische Leistung des Fluorids, das wiederholten Zyklen zu unterschiedlichen C–Raten standhalten konnte und seine volle Kapazität nach mehr als 50 Zyklen aufrecht erhielt im Gegensatz zum reinen HTBFeF3 ·0.33H2O. Für die Herstellung von aktiven Ionenspeichermaterialien zur Verminderung der Sichereitsrisiken (im Vergleich zur Verwendung von Metallanoden) sind Strukturen wie HTBFeF3 ·0.33H2O notwendig. Hierzu wurden Na–enthaltende Hexafluoroferrat-Nanokomposite hergestellt und mit RGO und teilweise oxidierten Ruß (ox–CB) als leitfähigen Kohlenstoff versetzt. Die Art des Kohlenstoffzusatzes beeinflusste die elektrochemische Leistung stark, wobei mit RGO die größten Verbesserungen erzielt werden konntenHexagonal tungsten bronze (HTB)-FeF3∙0.33H2O xerogel and HTB-FeF3∙0.33H2O/GO nanocomposite were firstly obtained by a room temperature fluorolytic sol-gel approach in MeOH, and their electrochemical properties evaluated. Operando Mössbauer spectroscopy and X-Ray diffraction were employed to investigate the reaction mechanism during reaction with lithium. The fluoride evidenced a complex behavior, with structural collapse of the HTB phase and gradual transformation into FeF2-rutile-like nanodomains, becoming the predominant component all along the reaction. XRD confirmed the amorphization of the electroactive material. Structural optimization of HTB-FeF3·0.33H2O was then achieved by a microwave-assisted fluorolytic sol-gel in benzyl alcohol. The procedure allowed the synthesis of phase pure nanoparticles of ~30 nm in diameter, along with the production of a reduced graphene oxide (RGO)-based nanocomposite and the reduction of reaction times. Deposition onto conductive RGO resulted beneficial for the electrochemical performance of the fluoride, which was able to sustain repeated cycling at different C-rates and recovered full capacity after more than 50 cycles with respect to the unsupported HTB-FeF3·0.33H2O. Aiming at the production of active ions-holding materials to solve safety issues related to the use of metallic anodes, necessary with structures such as HTB-FeF3·0.33H2O, Na-containing hexafluoroferrate nanocomposites were produced using RGO and partially oxidized carbon black (ox-CB) as conductive carbons. Carbon type greatly affected the electrochemical performance, whose best improvement was obtained using RGO as support
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Ye, 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.
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李德利 and Deli Li. "Thermodynamic formulation for damaging materials." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31233764.
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Li, Deli. "Thermodynamic formulation for damaging materials /." [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1367173X.
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Khanlari, Samaneh. "Poly(Sodium Acrylate)-Based Antibacterial Nanocomposite Materials." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32556.
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Afzal, Muhammad. "Nanocomposite Materials for New Energy Conversion Device." Thesis, KTH, Materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122675.
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This thesis gives an approach how to develop newperovskite and nanocomposite cathode material for low temperature solid oxidefuel cells on the basis of nanocomposite approach to lower the operatingtemperature of SOFC. BaxCa1-xCoyFe1-yO3-δ(BCCF) and BSCF perovskite or nanocomposite oxides have been synthesized andinvestigated as catalytically potential cathode materials for low temperaturesolid oxide fuel cells (LTSOFC). Some single component materials have been alsosynthesized for new energy conversion device or EFFC. These nanocomposite andperovskite electrical conductors were synthesized by wet chemical, sol gel,co-precipitation and solid state reaction methods. Comparison with that ofcommercial Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) cathode material, BCCF and locally prepared BSCF exhibit higher electricalconductivities as compared to that of commercial BSCF at same setup andconditions. In particular, novel Ba0.3Ca0.7Co0.8Fe0.2O3-δhas shown the maximum conductivity of 143 S/cm in air and local BSCF withconductivity of 313 S/cm in air at 550°C were measured by DC 4 probe method. Anadditional positive aspect of BCCF is that it is cost effective and works atroom temperature but with small output which will lead SOFC to operate atextremely low temperatures. XRD patterns of the samples reveal perovskite andnanocomposite structures of the said materials. Microstructure studies give thehomogeneous structure and morphology of the nanoparticles by using HighResolution Scanning Electron Microscopy (SEM). Cell resistance has beendetermined by Electrochemical Impedance Spectroscopy (EIS). Devised materialshave shown very good mechanical strength and stability proving their importancein advanced fuel cell technology. Power density of devices from 126 to 192 mWcm-2hasbeen achieved.
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Boni, Alessandro <1987>. "Electrochemistry of Nanocomposite Materials for Energy Conversion." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7510/1/boni_alessandro_tesi.pdf.
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Energy is the most relevant technological issue that the world experiences today, and the development of efficient technologies able to store and convert energy in different forms is urgently needed. The storage of electrical energy is of major importance and electrochemical processes are particularly suited for the demanding task of an efficient inter-conversion.
A potential strategy is to store electricity into the chemical bonds of electrogenerated fuels, like hydrogen and/or energy-dense hydrocarbons. This conversion can be accomplished by water splitting and CO2 electrolysis. In this context, are herein presented three different electrochemical approaches towards water and CO2 reduction.
In Chapter 1 is reported a novel class of nanostructured electrocatalysts, MWCNTs@Pd/TiO2, able to efficiently reduce water at neutral pH. Multi-walled carbon nanotubes, Pd nanoparticles and titanium dioxide are mutually integrated within the nanocomposites, whose electrocatalytic properties are thoroughly investigated and optimized. By electrochemical methods it is rationalized the effect of each building block on the overall activity, which originate from the synergic cooperation of the three units.
In Chapter 2 is presented an electrochemical study of MWCNTs@CeO2, a noble-metal free electrocatalyst with a similar architecture to MWCNTs@Pd/TiO2. The electroreduction of CO2 has often the drawbacks of a poor selectivity and high energy losses for the high overpotential required to drive the reaction. However, detailed studies of MWCNTs@CeO2 highlights the possibility to convert CO2 to formic acid at very low overpotential and with a high selectivity. A reaction mechanism that involves the participation of surface hydride species and the CeO2 shell is proposed.
Finally, in Chapter 3 is presented a photo-electrochemical approach to hydrogen production. Solar energy is converted to hydrogen via water reduction on the surface of a catalyst-free, oxide-protected solar cell. The large solar-to-hydrogen activity of the photocathode assembly has been explained by a combination of experimental and theoretical studies.
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Hynowska, Anna. "Biocompatible Ti-based metallic glasses and nanocomposite materials." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/283651.
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Aquesta Tesi comprèn la síntesi i caracterització d’aliatges de base Ti amorfs i
nanoestructurats. Així, s’han estudiat diversos aliatges amb composició Ti-44.3Nb-
8.7Zr12.3Ta, Ti-31.0Fe-9.0Sn, Ti40Zr20Hf20Fe20, Ti45Zr15Pd35-xSi5Nbx (x = 0, 5%) com a
exemples d’aliatges de base Ti nanoestructurats, i el vidre amorf massís
Ti40Zr10Cu38Pd12. Aquests materials es van escollir tenint en compte les seves potencials
aplicacions com a implants ortopèdics. La primera part d’aquesta Tesi va consistir en
la síntesi i caracterització d’aquests aliatges bo i fent especial èmfasi en les
correlacions existents en el triangle microestructura – comportament mecànic –
biocompatibilitat. En la segona part es van dur a terme tractaments d’irradiació amb
feixos d’ions del vidre amorf com a estratègia per modificar les seves propietats
superficials i, de retruc, incrementar-ne la compatibilitat biomecànica.
Totes les mostres es van sintetitzar per fusió d’arc i posterior emmotllament. Es va dur a
terme una caracterització exhaustiva de tipus tèrmic i estructural de les mostres
anteriorment mencionades mitjançant calorimetria diferencial d’escombrat (DSC),
difracció de raigs X (XRD) i microscòpia electrònica de rastreig i transmissió (SEM,
TEM). Tot seguit, els materials es van caracteritzar mecànicament (nanoindentació,
mesures acústiques), electroquímicament (assaigs de polarització potenciodinàmica) i
biològicament (toxicitat, morfologia, adhesió i diferenciació cel·lular).
S’ha vist que l’aliatge nanoestructurat Ti-Nb-Zr-Ta és interessant pel seu baix mòdul de
Young (Er = 71 GPa), mentre que el sistema Ti-Fe-Sn destaca per la seva elevada
duresa (H = 8.9 GPa). Ensems, l’aliatge Ti-Zr-Pd-Si-Nb posseeix un mòdul de Young
relativament baix (Er = 85 GPa) i una duresa elevada (H = 10.4 GPa). En general,
quan s’alien amb el Ti elements estabilitzadors tipus (Nb, Ta, Fe i Pd), combinats
d’una forma adient, s’aconsegueix reduir del mòdul de Young del material i, al mateix
temps, incrementar-ne la duresa. La substitució parcial de Pd per Nb és una estratègia
eficaç per disminuir el mòdul elàstic (es va observar una davallada de fins a un 30% en
el valor de Er) del sistema Ti-Zr-Pd-Si i, simultàniament, reduir-ne el cost. D’altra
banda, s’obtenen valors elevats de duresa, com és el cas dels aliatges Ti-Zr-Pd-Si-(Nb) i
Ti-Zr-Hf-Fe, quan s’aconsegueix tenir una microestructura formada per una mescla de nanofases. Val a dir que tots els aliatges estudiats presenten una resistència al desgast
superior a la de l’aliatge d’ús comercial Ti-6Al-4V. Així mateix, no s’ha observat un
deteriorament significatiu dels materials en els estudis de corrosió electroquímica,
malgrat que es va detectar atac per picadura en el vidre amorf massís Ti40Zr10Cu38Pd12.
Els assajos biològics van demostrar que tant les cèl·lules preosteoblast de ratolí com
humanes s’adhereixen molt bé sobre la superfícies dels aliatges i que són capaces de
diferenciar-se en osteoblasts, en part com a conseqüència de la presència d’elements no
tòxics en la seva composició.
En aquesta Tesi també es demostra que per a fluències d’ions i energies incidents
suficientment baixes, es preserva el caràcter amorf del vidre massís Ti40Zr10Cu38Pd12
després de la irradiació a temperatura ambient. En canvi, quan aquestes condicions
d’irradiació s’apliquen a una temperatura propera a Tg (620 K), s’indueix una
nanocristal·lització parcial a la superfície del material. Això fa que ocorrin canvis en
les propietats mecàniques que són totalment oposats dels observats a temperatura
ambient (reducció de la duresa i del mòdul de Young probablement a causa de
l’increment de concentració del volum lliure). En particular, després del tractament
amb feixos d’ions a alta temperatura, s’observa un increment tant de la duresa com del
mòdul de Young. Els resultats indiquen, per tant, que bo i modulant tant la temperatura
de la mostra com les condicions d’irradació, poden controlar-se les propietats del
material resultant per tal de satisfer demandes tecnològiques específiques, com ara de
tipus mecànic.This Thesis covers the synthesis and overall characterization of Ti-based glassy alloys and nanostructured materials. Several Ti-based nanostructured alloys with nominal composition, Ti-44.3Nb-8.7Zr12.3Ta, Ti-31.0Fe-9.0Sn, Ti40Zr20Hf20Fe20, Ti45Zr15Pd35-xSi5Nbx (x = 0, 5%), and Ti-based bulk metallic glass (BMG), Ti40Zr10Cu38Pd12, were investigated. These materials were chosen due to their potential applications as orthopedic implants. The first part of the study focused on the synthesis and characterization of these alloys by paying special attention to the correlation triangle microstructure-mechanical behaviourbiocompatibility. The second part was devoted to ion-irradiation treatment of the BMG material as a means to modify the surface properties and therefore increase its biomechanical compatibility. All samples were produced by arc melting and subsequenct suction casting. The in-depth thermal and structural characterization of above-mentioned samples was carried out by means of differencial scanning calorymetry (DSC) and x-ray diffraction (XRD), together with scanning and transmission electron miscroscopies (SEM, TEM). Subsequently, the samples were subjected to mechanical (nanoindentation, acoustic measurement), electrochemical (potentiodynamic polarization tests) and biological (cytotoxicity, cell morphology, adhesion and differentiation) analysis. It is shown that Ti-Nb-Zr-Ta nanostructured alloy is appealing because of its low Young’s modulus (Er = 71 GPa), whereas the Ti-Fe-Sn system is interesting because of its large hardness (H = 8.9 GPa). Meanwhile Ti-Zr-Pd-Si-Nb alloy possesses relatively low Young’s modulus (Er = 85 GPa) and high hardness (H = 10.4 GPa). The lowering of Young’s modulus and the increase in hardness was achieved through proper combination of - stabilizer elements (Nb, Ta, Fe and Pd) alloyed with Ti. Partial replacement of Pd by Nb is a convenient strategy to decrease the Young’s modulus (almost a drop of 30% in Er was observed) of the Ti-Zr-Pd-Si system, and to reduce costs. On the other hand, a microstructure consisting of a mixture of nanophases gives rise to large hardness values, as is the case of Ti-Zr-Pd-Si-(Nb) and Ti-Zr-Hf-Fe alloys. Additionally, all studied alloys exhibit better wear resistance than that of commercially used Ti-6Al-4V. None of the studied materials showed extensive corrosion damage when tested electrochemically, although pitting was observed in Ti40Zr10Cu38Pd12 BMG. The biological assays demonstrated that either preosteoblast mouse or human cells adhered very well to the surface of the studied alloys and were able to differentiate into osteoblasts. This is due, to some extent, to the presence of safe (i.e., non-toxic) elements in alloys’ composition. In this Thesis, it is also demonstrated that for sufficiently low ion fluencies and low incident energies, the glassy structure of the as-cast Ti40Zr10Cu38Pd12 BMG is preserved after irradiation at room temperature (RT). Conversely, the same mild irradiation conditions applied at a temperature close to Tg (620 K) induce partial nanocrystallization at the surface of the material. As a consequence, the changes in mechanical properties observed after irradiation at RT (reduction of hardness and Young’s modulus, presumably due to the increase of the free volume concentration) are opposite to those observed after temperatureassisted ion irradiation processes. Namely, an enhancement is observed after hightemperature irradiation of the Ti-based glassy alloy. Hence, these results indicate that, by tuning both the sample temperature and the irradiation conditions, the properties of the resulting material can be controlled in order to meet specific technological demands, such as mechanical performance.
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Sadeghi, Forouzan. "Development of nanocomposite materials for gas separation membranes." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27553.
Full textAbstract:
The objective of this study is to improve the compatibility of nanoparticles in composite materials. This was achieved by developing a method in which an inorganic precursor contained in a stable water/oil (W/O) emulsion was mixed with a polymer solution containing a second inorganic precursor. Inorganic polymerization occurred in the aqueous domain of the W/O emulsion. The in-situ synthesis of the precursor was performed in order to enhance the nanoscale compatibility between the inorganic material and polymer. This technique produced materials which we have named: emulsion polymerized mixed matrix (EPMM) materials.
A series of poly (2,6-dimethyl-1,4-phenylene oxide) (PPO)-based organic-inorganic membranes were prepared by employing this method. A W/O emulsion containing aluminium hydroxonitrate was added to a PPO solution containing tetraethyl orthosilicate (TEOS). Droplet sizes in the W/O emulsions, observed by dynamic light scattering (DLS) ranged from 254 to 344 nm.
Scanning electron micrography (SEM), electron diffractive X-Ray (EDX), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gas permeation and separation measurements were carried out to characterize the EPMM membranes. SEM indicated the presence of inorganic particles in the PPO matrix, and EDX measurements showed the embedded particles contained Al and Si elements, which confirmed the hydrolysis and condensation of TEOS with aluminium hydroxonitrate. DSC analysis showed a decrease in the glass transition of the EPMM membranes with increasing of TEOS loading. The fractional free volume of the EPMM membranes was predicted through the measurement of the heat capacity jump at the glass transition temperature. The integrity of the EPMM membranes was confirmed in gas separation test with air, in which the ideal selectivity for O2/N2 was observed to be as high as 4.56.
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Kulkarni, Dhaval Deepak. "Interface properties of carbon nanostructures and nanocomposite materials." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49092.
Full textAbstract:
Two different interfaces were the focus of study: 1) the interface between disordered amorphous carbon and inorganic materials (metal nanostructures and silicon), and 2) the interface between partially ordered graphene (graphene oxide) and synthetic polymer matrix. Specifically, the uniqueness of this study can be summarized through the following novel findings, fabrication processes, and characterization techniques:
• A simple and efficient process for faster, greener, less-expensive, and highly localized transformation of amorphous carbon nanostructures into graphitic nanostructures using low temperature heat and light treatments was developed for the fabrication of low-resistance interfaces between carbon nanomaterials and inorganic metal surfaces.
• A new protocol for high resolution mapping the charge distribution and electronic properties of nanoscale chemically heterogeneous domains on non-homogeneous surfaces such as graphene oxide was established.
• High strength laminated mechanical nanocomposites based on high interfacial stress transfer between polymer matrices and large area, flat, and non-wrinkled graphene oxide sheets were suggested and demonstrated.
• Scanning Thermal Twist Microscopy – a thermal microscopy based technique was developed and demonstrated for characterizing the thermal properties of homogeneous and heterogeneous interfaces with nanoscale spatial resolution and high thermal sensitivity unachievable using traditional techniques.
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Wang, Yan. "Exploring Biopolymer-Clay Nanocomposite Materials by Molecular Modelling." Doctoral thesis, KTH, Teoretisk kemi och biologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166299.
Full textAbstract:
In this thesis, bio-nanocomposites made from two alternative biopolymers and montmorillonite (Mnt) clay have been investigated by molecular modelling. These biopolymers are xyloglucan (XG) and chitosan (CHS), both of which are abundant, renewable, and cost-effective. After being reinforced by Mnt clay nanoparticles, the polymer nanocomposites gains in multifunctionality and in the possibility to register unique combinations of properties, like mechanical, biodegradable, electrical, thermal and gas barrier properties. I apply molecular dynamics (MD) simulations to study the interfacial mechanisms of the adhesion of these biopolymers to the Mnt nanoplatelets at an atomic level. For the XG-Mnt system, a strong binding affinity of XG to a fully hydrated Mnt interface was demonstrated. It was concluded that the dominant driving force for the interfacing is the enthalpy, i.e. the potential energy of the XG-Mnt interacting system. The adsorbed XG favors a flat conformation with a galactose residue in its side chain that facilitates the adsorption of the polymer to the nanoclay. The XG adsorption was found do depend strongly on the hydration ability of counterions. The binding affinity of XG to Mnt was found to be strongest in the K-Mnt/XG system, followed by, in decreasing order, Na-Mnt/XG, Li-Mnt/XG, and Ca-Mnt/XG. The competing mechanism between ions, water and the XG in the interlayer region was shown to play an important role. The dimensional stability upon moisture exposure, i.e. the ability of a material to resist swelling, is an important parameter for biopolymer-clay nanocomposites. While pure clay swells significantly even at low hydration levels, it is here shown that for the XG-Mnt system, at a hydration level below 50%, the inter-lamellar spacing is well preserved, suggesting a stable material performance. However, at higher hydration levels, the XG-Mnt composite was found to exhibit swelling at the same rate as the pure hydrated Mnt clay. For the CHS-Mnt system, the significant electrostatic interactions from the direct charge-charge attraction between the polymer and the Mnt clay play a key role in the composite formation. Varying the degree of acetylation (DA) and the degree of protonation (DPr) resulted in different effects on the polymer-clay interaction. For the heavily acetylated CHS (DA > 50%, also known as chitin), the strong adhesion of the neutral chitin to the Mnt clay was attributed to strong correlation between the acetyl functional groups and the counterions which act as an electrostatic “glue”. Similarly, the poor adhesion of the fully deprotonated (DPr = 0%) neutral CHS to the clay is attributed to a weak correlation between the amino functional group and the counterions. The stress-strain behavior of the CHS-Mnt composite shows that the mechanical properties are highly affected by the volume fraction of the Mnt clay and the degree of exfoliation of the composite. The material structure has a close relationship to the material properties. Biopolymer-clay nanocomposites hold a bright future to replace petroleum-derived polymer plastics and will become widely used in common life. The theme of the thesis is that further critical improvements of these materials can be accomplished by development of the experimental methods in conjunction with increased understanding of the interactions between polymer, clay, water, ions, solutions in the polymer-clay mixtures provided by molecular modelling.I denna avhandling har molekylär modellering och molekyldynamisk (MD) simulering använts för att studera modellsystem för bio-nanokompositer bestående av montmorillonit-lera samt två olika sorters biopolymerer – xyloglukan (XG) och kitosan (CHS). Båda dessa polymerer är naturligt förekommande och mycket vanliga. De är dessutom förnyelsebara och kostnadseffektiva. Då polymererna förstärkts med nanopartiklar av montmorillonit får det resulterande kompositmaterialet en unik kombination av egenskaper såsom mekaniska, elektriska, termiska och barriär egenskaper etc. Genom att använda molekyldynamiska (MD) simuleringar, studeras här växelverkan mellan dessa biopolymerer och lernanopartiklar (Mnt) på grundläggande atomistisk detaljnivå. Mellan XG och Mnt i ett fullt hydrerat system kunde stark bindningsaffinitet påvisas. Den dominerande drivkraften för affiniteten var entalpi, d.v.s. potentiell växelverkansenergi. Den adsorberade XG-kedjan antar en platt konformation på ytan. Ett förslag utifrån simuleringsresultaten var att galaktosresidyn i xyloglukanets sidokedja underlättar adsorptionen till lerytan. Simuleringarna kunde också visa att adsorption av XG till Mnt beror starkt på motjonernas hydreringsförmåga. Bindningsaffiniteten mellan XG och Mnt var som starkast i K-Mnt/XG- systemet. Därefter följde, i minskande ordning, Na-Mnt/XG, Li-Mnt/XG och Ca-Mnt/XG. Det kunde visas att strukturen vid gränsytan styrs av konkurrerande mekanismer mellan joner, vatten och XG. Dimensionsstabilitet vid fuktexponering, d.v.s. förmågan hos ett material att motverka svällning, är en viktig egenskap för biopolymer-lernanokompositer. Ren lera sväller signifikant även vid låga fukthalter. Dock kunde MD simuleringar visa att ett modellsystem av XG-Mnt behåller sitt ursprungliga interlamellära avstånd vid hydreringsnivåer under 50%, vilket indikerar ett stabilare material. Vid högre hydrering uppmättes dock svällningen vara densamma som för ren lera. I CHS-Mnt-systemet visade det sig att direkt elektrostatisk växelverkan med signifikant styrka mellan laddningar på polymer och Mnt-yta spelar störst roll för kompositformeringen. Olika effekt på polymer-lerväxelverkan uppnåddes genom att variera acetyleringsgraden (DA) respektive protoneringsgraden (DPr). För den tungt acetylerade CHS-polymeren (DA > 50%, även kallad kitin) visade sig den starka vidhäftningen bero på korrelation mellan acetylgrupperna och motjonerna som i sin tur verkade som ett elektrostatiskt “lim”. På liknande sätt kunde den svaga vidhäftningen mellan fullt deprotonerad (DPr = 0%) neutral CHS och lera förklaras med en betydligt svagare korrelation mellan aminogrupperna och motjonerna. Spänning-töjningsbeteendet hos CHS-Mnt modellen visar att dess mekaniska egenskaper beror kraftigt på volymsandelen Mnt och graden av exfoliering i kompositen. Materialets struktur är nära relaterat till materialegenskaperna. Framtiden för nanokompositer av biopolymerer och lera är ljus då de kan komma att ersätta oljebaserade plaster och användas frekvent i våra dagliga liv. Materialen kommer successivt förbättras genom utveckling av experimentella metoder i kombination med molekylmodellering för ökad förståelse för växelverkan mellan polymer, lera, vatten, joner och lösningsmedel.
本论文利用分子动力学模拟技术研究了两种备选生物大分子与蒙脱土(Montmorillonite, Mnt)（一种粘土）组成的生物纳米复合材料，分别是木葡聚糖（Xyloglucan, XG）/蒙脱土和壳聚糖(Chitosan, CHS)/蒙脱土。木葡聚糖与壳聚糖都是自然界广泛存在的生物大分子，资源丰富且取材面宽，提取及加工成本低廉，加之可以生物降解并可再生，是优秀的生物复合材料备选原料。经过蒙脱土纳米颗粒加固后，这些基于生物大分子的复合材料将获得多功能且有多种独特特性相结合的优点，比如，更好的力学性能，生物可降解，良好的导电性能，传热性能和屏蔽气体与液体侵扰的能力等等。论文中，我们采用分子动力学模拟的方法着重对生物大分子与蒙脱土在界面上的粘附相互作用机理进行了深入探讨。 首先，对于木葡聚糖/蒙脱土纳米复合材料，我们发现糖分子与土分子间有着很强的天然亲和力。研究证明它们之间的这种相互作用，热焓是主要的推动力，也就是糖和土分子间的相互作用势能。含有半乳糖残基的木葡聚糖分子（本文中亦称天然木葡聚糖分子）吸附到粘土表面后，分子构型呈现扁平状，半乳糖残基似有辅助木葡聚糖大分子吸附到粘土颗粒上的作用。 进一步研究发现，木葡聚糖分子在粘土表面上的吸附与溶液中抗衡离子的水和作用密切相关。在钾离子平衡的糖/粘土系统中，糖分子与土分子的相互作用最强，钠离子平衡的糖/粘土系统次之，紧接着是锂离子平衡的糖/粘土系统，最弱的是钙离子平衡的糖/粘土系统。研究发现，离子，水分子，以及糖分子在粘土层间的竞争机制在糖分子的粘附过程中起着重要的作用。 材料暴露于潮湿环境中的尺寸稳定性，也就是材料抗肿胀的能力是生物大分子/蒙脱土所构成的复合材料的重要参数。蒙脱土自身即使在很低的潮湿环境下就会有明显地膨胀现象，然而，对木葡聚糖/蒙脱土复合材料来说，尺寸稳定性可以在水和值低于50%以下有效保存。其夹层尺寸的稳定保持暗示了材料在这个程度的潮湿环境下的稳定性。然而，当水和值高于50%时，木葡聚糖/蒙脱土复合材料将出现明显的肿胀现象，表现在夹层尺寸的明显增大，且其膨胀速率与粘土自身的膨胀速率逐渐趋于相当水平。 其次，对于壳聚糖/蒙脱土复合材料，我们发现由电荷-电荷间直接产生地强烈的静电吸引作用是壳聚糖分子与蒙脱土分子相互粘附并构成复合材料的关键因素。通过改变壳聚糖分子的乙酰化程度（Degree of acetylation, DA）和质子化程度(Degree of protonation, DPr)，糖分子与土分子的相互作用有着显著地不同。对于乙酰化程度（DA）高于50%的壳聚糖分子（亦成为甲壳素分子chitin, CHT），电中性的甲壳素分子与土分子间的强吸附作用源于乙酰基功能团与抗衡离子的强相关性。抗衡离子此时扮演着类似于“电子胶”的作用，可以有效地将电中性的甲壳素分子与土分子粘结在一起。类似地，当质子化程度最低时，亦即壳聚糖分子完全非质子化，即呈现电中性时，较差的糖/土吸附作用源于氨基功能团与抗衡离子的较弱的相关性。 进一步对壳聚糖/蒙脱土复合材料的分子系统进行应力应变计算发现，复合材料的力学性能直接受蒙脱土体积分数和其剥离程度的影响，通常，粘土的体积分数越大体系的力学性能越高，且剥离程度对材料的整体性能也有直接影响。因此，材料的结构与其性能的表征有着密切联系。 我们相信生物大分子与蒙脱土构成的生物复合材料有着光明的前景，可以取代石油提取物制成的塑料材料，并将能够广泛应用在日常生活中。通过实验技术的改善和应用分子模拟技术对复合材料体系中生物大分子，蒙脱土分子，水分子，离子，溶液环境等混合物质相互作用的理解增加，这种可再生的新材料将会得到重要改进，这也是整本论文的主旋律。
QC 20150520
Bio-nanocomposites
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Czarnecka, Anna. "Preparation and Characterization of Kaolinite-based Nanocomposite Materials." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24379.
Full textAbstract:
A kaolinite-nylon 6 composite was prepared by a polycondensation reaction from 6-aminohexanoic acid (AHA) intercalated in the kaolinite interlayer space. The basal spacing of kaolinite-AHA was 1.47 nm and the basal spacing of the heated products decreased to 1.16 nm. The signals attributed to nylon 6 were detected in the 13C CP/MAS NMR spectra of the heated products. Formation of nylon 6 in kaolinite was confirmed by appearance of IR band due to amide I and amide II.
Sarcosine was intercalated in kaolinite for the first time by guest displacement with methanol from the kaolinite-methanol precursor. The basal spacing of kaolinite-sarcosine was 1.27 nm. This intercalation compound was characterized by NMR, TGA, XRD, and IR.
The physical and chemical properties of natural clay sample from Mirandela formation (Portugal) were determined in terms of external skin treatment. The low CEC 4,45meq/100g is consistent with high content of kaolinite in the sample
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Yee, Swee Li Maxine. "Silver-based nanocomposite materials for marine antifouling applications." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/45513/.
Full textAbstract:
Biofouling of marine surfaces is an age-old problem that affects natural and man-made surfaces exposed to the aquatic environment. The tenacious attachment of seaweed and invertebrates to man-made surfaces, notably on ship hulls, has incurred undesirable economic losses. The initial stage of the biofouling process has been attributed to the attachment of marine bacteria and their subsequent formation of biofilm which attract the settlement of larger sessile organisms including barnacles and seaweed. Silver nanostructured materials have a well-documented history as antimicrobial agents against pathogenic bacteria due to their ability to penetrate cell walls and interfere with crucial cellular processes. However, there is a surprising lack of information on their activity against marine biofilm bacteria that have critical roles in the initiation of marine fouling processes. This PhD project explores the antifouling properties of novel silver nanocomposite materials as potent antifouling agents against targeted organisms present in marine environments. The study consists of the syntheses of novel silver nanocomposite materials using various templates/matrices such as ion-exchange polymeric microspheres, zeolites, TiO2 nanotubes and graphene nanosheets. These materials were characterized through various instrumentation techniques including scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray powder diffraction (XRD), UV-visible (UV-vis) spectrophotometry, transmission electron microscopy (TEM), accelerated surface area porosimetry (ASAP), thermal gravimetric analysis (TGA), and Raman spectroscopy to elucidate their physical properties. Their antifouling effects were evaluated on Halomonas pacifica, a model marine microfouling bacterium, through an established static biofilm assay. In addition, the biological effects of these silver nanocomposites were also studied on marine microalgae Dunaliella tertiolecta and Isochrysis sp. Silver-polymer nanocomposite (Ag-PNC) microspheres were formed through a rapid chemical synthesis procedure at room temperature via the reduction of silver nitrate by sodium borohydride. The introduction of Ag nanoparticles (AgNPs) enhanced the thermal stability of the Dowex microspheres by shifting the glass transition temperature to above 300°C and the material decomposition occurred above 460°C. XRD analysis confirmed the presence of metallic Ag, while UV-vis absorption studies showed the characteristic surface plasmon resonance (SPR) for AgNPs ranging from 406 – 422 nm maximum absorption wavelengths. SEM imaging revealed the uniform distribution of AgNPs with diameters between 20 – 60 nm on the surface of the microbeads. The Ag-PNC materials, diluted to a concentration of 1 mg/mL in marine broth, showed a potent inhibitory effect on H. pacifica biofilm formation, with up to 76% decrease of biofilm when contrasted with the polymeric microspheres without Ag. Ag-PNCs also caused significant growth inhibition of D. tertiolecta and Isochrysis sp. Silver-zeolite nanocomposite clusters (AgZ) were formed through a low temperature chemical reduction method using the environmentally friendly trisodium citrate. The stable and porous inner structure of ZSM-5 zeolites performed a dual role as a stable size-control template and a reservoir of antimicrobial nanosilver. SEM revealed the globular and cluster-like morphology of the AgZ composites, with a homogenous distribution of silver particles on the surface of the clusters. EDX results displayed an increasing Ag loading with higher concentrations of Ag precursor, up to 10 wt% Ag. The UV-visible absorption displayed the characteristic SPR absorption maximum ranging from 408 – 500 nm. The AgZ clusters with metallic silver loading of up to 10 wt% Ag, diluted to a concentration of 1 mg/mL, reduced H. pacifica biofilm attachment of up to 81% compared to pure zeolite alone. XRD analysis clearly indicated the presence of metallic Ag while the ZSM-5 zeolite crystalline framework remained largely intact after the Ag crystal growth process. Brunauer-Emmett-Teller (BET) analysis showed a reduction in surface area of up to 44% with the incorporation of AgNPs into the zeolite, indicating the formation and growth of Ag within the internal pores and channels of the zeolite. Although the introduction and crystal growth of silver nanoparticles within the porous structure of the zeolite caused a change from a mesoporous to a largely macroporous structure, the integrity of the zeolite template was preserved. Silver-titania nanotube (Ag/TNT) composite material was prepared through a novel 2-step hydrothermal synthesis method. Titania nanotubes were chosen as a support material for the AgNPs as its greater specific surface area on the inner and outer surfaces of its tubular structure lead to enhanced properties. The morphology, particle size, chemical content, crystal structure, optical properties and surface area were systematically characterized. Determination of biofilm inhibitory properties revealed that Ag/TNT (concentration of 0.1 mg/mL) with the lowest silver content (0.95 wt% Ag) decorated with AgNPs of approximately 3 nm reduced biofilm formation of H. pacifica by 98% compared to pure titania nanotubes and bulk silver alone. Growth inhibition of D. tertiolecta and Isochrysis sp. were also observed. Interestingly, the antifouling properties were improved with a size decrease of AgNPs. The work shows that titania nanotubes are a stable and effective support for the anchoring and growth of AgNPs. The addition of very low amounts of Ag enhanced the antifouling property of pure TiO2 to produce an extremely potent antifouling effect on the targeted organisms. Graphene-Ag (GAg) nanocomposites were prepared from a novel and mild hydrothermal synthesis method which bypasses the formation of graphene oxide. The GAg nanocomposite combines the antimicrobial property of silver nanoparticles and the unique structure of graphene as a support material, with potent marine antifouling properties. The results show that GAg nanocomposites displayed significant biofilm inhibition property on H. pacifica and antiproliferative effects on D. tertiolecta and Isochrysis sp. As low as 1.3 wt% of Ag loading on a GAg sample, diluted to a concentration of 0.1 mg/mL, inhibited biofilm formation from H. pacifica. The GAg sample with 4.9 wt% Ag loading was associated with a biofilm inhibition of 99.6%. The marine antifouling properties of GAg nanocomposites were a synergy of the biocidal AgNPs anchored on the flexible graphene sheets, thereby providing maximum active contact surface areas to the target organisms. The GAg material was characterized with SEM, EDX, TEM, XRD and Raman spectroscopy. In addition, the GAg material exhibited the surface-enhanced Raman scattering (SERS) effect. The AgNPs were estimated to be between 72-86 nm, observed supported on micron-scaled graphene flakes. These results strongly suggest that the 4 types of silver-based nanocomposite materials are promising marine antifouling agents. The addition of very low amounts of Ag enhanced the antifouling property of the support structure, and the nanocomposites were shown to be more effective on the targeted organisms compared to the matrix material or bulk silver alone. In addition, the precursor materials used in the syntheses are affordable and easily available, whilst the synthetic methods and conditions are facile, environmentally friendly, and capable of producing high yields.
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Link, Jessica. "Stabilization and structural study of new nanocomposite materials." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1238/document.
Full textAbstract:
Ce travail de thèse a été consacré au développement de nanocomposites polymère (PVDF-co-HFP) – silice hautement chargés en nanoparticules par voie solvant. La combinaison d’un polymère fluoré ; ayant des propriétés mécaniques, diélectriques, piézoélectriques et pyroélectriques très intéressantes ; avec des nanoparticules de silice pourrait nous permettre le développement de nouvelles solutions dans le domaine de l’énergie. Ainsi nous avons étudié l’impact de la chimie de surface des nanoparticules de silice, des paramètres expérimentaux et du procédé par voie solvant sur la structure et les propriétés finales des matériaux obtenus. Pour la réalisation de ces matériaux par voie solvant, une solution P(VDF-co-HFP) – silice dans un solvant commun est préparée puis séchée. Dans le cadre de ce projet nous avons travaillé avec des cétones aliphatiques présentant différentes longueurs de chaînes: la Methyl Ethyl Ketone (MEK) et la 2-heptanone. Ainsi pour la préparation des solutions nous avons développé une approche générique pour transférer des nanoparticules en solution dans l’eau dans un solvant organique par l’intermédiaire d’un agent de transfert. Cependant, avant l’étape de dépôt et séchage, nous avons constaté que le PVDF et ses copolymères (dont le P(VDF-co-HFP)) forment un gel thermoréversible dans ces deux solvants ; avec ou sans silice. Cette gélification impacte certainement l’étape de solvent casting or aucun consensus concernant les mécanismes responsables de la gélification de ce polymère n’a été trouvé dans la littérature. Il apparait primordial de comprendre les mécanismes de gélification du P(VDF-co-HFP) avant d’étudier les propriétés des nanocomposites. Pour cela nous avons étudié l’influence de différents paramètres : nature du solvant, concentration en copolymère, température, présence de charges (concentration et chimie de surface) sur les mécanismes de gélification (Chapitre 3). La cinétique de gélification a été étudiée par tube-tilting et rhéologie linéaire. Une combinaison de RMN 19F, DSC, SAXS, WAXS et rhéologie non-linéaire a été utilisée pour déterminer les mécanismes réponsables de la gélification du P(VDF-co-HFP) dans ces solvants. La 19F RMN a montré l'existence d'un réseau de polymère où des zones rigides agiraient comme des noeuds de réticulation. Ce comportement n'a été observé qu'à l'état gel: aucun réseau de polymère ou aucune zone rigide n'existent quand la solution de polymère est à l'état liquide. La nature et la fraction volumique de ces zones rigides présentes à l'état gel ont été étudiés par DSC et diffraction des rayons X. Une faible fraction de cristallites, qui correspondrait aux zones rigides, a été observée dans ces gels. Dans une troisième étape (Chapitre 4), l'impact de l'addition de silice sur la gélification du P(VDF-co-HFP) a été étudié. Pour cela, des gels polymère-silice ont été formulés dans la MEK et la 2-heptanone en utilisant deux sources de silice nanométrique: celle préparée par transfert de phase et une solution commerciale Nissan. Nous avons observé que la présence de silice impacte peu la gélification du polymère contrairement au procédé, et plus particulièrement à la présence d'eau résiduelle dans le matériau. La rhéologie non linéaire des gels dans la 2-heptanone, chargés ou non en silice, a ensuite été étudiée sous LAOS. Le comportement de ces matériaux varie avec la contrainte et passe d'un régime élastique à un régime visqueux. Cependant avant de passer dans le domaine visqueux, les gels non chargés montre un fort strain-hardening. Au contraire, l'incorporation de nanoparticules inhibe le strain-hardening. Dans une dernière étape, des films P(VDF-co-HFP)-silice ont été préparés par voie solvant. Des matériaux homogènes contenant jusqu'à 40wt% de nanoparticules ont été obtenus, avec des états de dispersions différents et finement controlés. L'impact de la concentration et de l'état de dispersion sur les propriétés mécaniques a été finalement étudiésThe general context of this PhD thesis is the development of highly filled polymer– silica model nanocomposites by solvent route, based on copolymers of vinylidene fluoride and hexafluoropropylene, denoted as P(VDF-co-HFP). Due to their unique combination of mechanical, dielectric, piezoelectric and pyroelectric properties, PVDF and VDF-copolymers combined with silica are good candidates for new advanced applications like actuation or energy harvesting. In this context, the primary objective was to understand how the filler surface chemistry and formulation parameters, as well as the solvent casting process, affect the final structure and properties of the materials. To elaborate P(VDF-co-HFP) nanocomposites with silica by solvent casting, a first step was to prepare solutions of silica and the polymer in a common solvent which will be subsequently dried. Aliphatic ketone solvents of various chain length, namely methyl ethyl ketone (MEK) and 2-heptanone, were used. For this purpose a generic approach to transfer silica nanoparticles from water to organic solvent through a transfer agent was developed. VDF-based copolymer solutions (filled or not with nanoparticles) exhibit thermoreversible gelation in ketone solvents, which may subsequently impact the processing of materials by solvent casting. Studying the phenomenology of PVDF gelation in thus of major concern for controlling the processing of those nanocomposites. No general consensus on the gelation mechanisms is found in the literature. In this context, the gelation of a semi-crystalline P(VDF-co-HFP) in MEK or 2-heptanone was studied. The gelation kinetics was investigated by tube-tilting and linear rheology. A combination of 19F Nuclear Magnetic Resonance (NMR), DSC, SAXS, WAXS and nonlinear rheology was used to probe the structure of these systems and the gelation mechanisms. 19F NMR shows the occurrence of a polymer network-like structure with rigid zones which may act as cross-links. Such a behavior is only observed in the gel state: no polymer network or rigid zones are present when the polymer solution is in the liquid state. The nature and volume fraction of the rigid zones present in the gel state were investigated with DSC and X-ray diffraction. A small crystalline fraction, which may correspond to the rigid zones, is observed in gels. In a third step, the impact of adding silica nanoparticles on the gelation kinetics of P(VDF-co-HFP) was studied. To do so, copolymer – silica gels were formulated in MEK and 2-heptanone using two sources of organic silica solutions, the one prepared previously by phase transfer and a commercial one from Nissan. We found that the presence of silica nanoparticles hardly disturbs the gelation of P(VDF-co-HFP). Conversely, the process, and more particularly the presence of residual water within the material, has a strong impact on the structure of the gels and gelation kinetics.The nonlinear rheological properties of the P(VDF-co-HFP) physical gels filled or not with silica nanoparticles were investigated in 2-heptanone only (as MEK is too volatile), using Large Amplitude Oscillatory Shear (LAOS) experiments (Chapter 5). The behavior of all materials changes from elastic at small strain to viscous at high strain amplitudes. Before abruptly changing from elastic to viscous behavior, unfilled gels exhibit strong strain-hardening. Incorporating silica nanoparticles is found to inhibit strain-hardening. In a last step, P(VDF-co-HFP) – silica solid films were obtained by solvent casting the previously prepared systems. Homogeneous materials filled up to 40 wt% of silica nanoparticles were obtained, with different and finely controlled dispersion states of nanoparticles, related to the structure of the initial gels or solutions. The impact of the concentration and dispersion state of the fillers on the mechanical performances (particularly the mechanical toughness) was investigated
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Kaya, Elçin Dilek Tanoğlu Metin. "Development of layered silicate/epoxy nanocomposite/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000538.pdf.
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Thesis (Master)--İzmir Institute Of Technology, İzmir, 2006.Keywords: epoxy resin, nanocomposites, clay, scanning electron microscope, mechanical properties. Includes bibliographical references (leaves. 93-98).
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Fang, Liming. "Processing of UHMWPE and HA/UHMWPE nanocomposite for biomedical applications /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20FANG.
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Santos, Peter J. (Peter Jeffries). "Self-assembling nanocomposite Tectons for ordered superlattices." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127907.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 260-280).
Nanocomposites, materials of heterogeneous composition with at least one of the phases having dimensions between 1-100 nm, can be produced with unique properties dependent on their composition and geometric configuration. However, it is a major challenge to precisely and simultaneously design the structure of synthetic nanocomposites at the nanoscale, microscale, and macroscale. To create advanced nanocomposites in which both structure and composition can be programmed across these disparate size regimes, we have developed a new nanoparticle-based building block, the Nanocomposite Tecton (NCT). An NCT consists of an inorganic nanoparticle core and a polymeric shell, with each chain terminating in a supramolecular binding group at the periphery of the NCT.
As each NCT contains both an inorganic nanoparticle and a polymer phase, each building block is itself a nanocomposite, and the incorporation of supramolecular binding groups allows for the directed assembly of NCTs that contain complementary binding groups. These reversible supramolecular interactions enable the assembly of NCTs into ordered arrays, and the collective behavior of the binding groups can be regulated by the dynamics of the polymer chains. The NCTs are capable of rapidly self-assembling into several different crystalline phases that are determined by the design of the building block, and are resilient against dispersity in the molecular weight of the polymer brush and the diameter of the nanoparticle cores. NCTs have been synthesized with both gold and iron oxide nanoparticle cores, indicating the ability to produce NCTs at reasonable scales.
Moreover, the incorporation of multiple nanoparticle compositions allows for the synthesis of NCT-based materials with plasmonic and magnetic properties that can affect, as well as be affected by, the assembly process. We further demonstrate that the crystallization kinetics can be modulated to induce the assembly of NCTs into faceted crystallites with micron-sized diameters, and the resulting NCT crystallites can be post-processed into bulk solids with arbitrary macroscopic shape and controlled grain size. The NCT design concept is therefore a highly modular and versatile building block capable of fabricating materials with controlled structures at the levels of atomic composition and molecular geometry, nanoscale organization, microstructure, and macroscopic form.
by Peter J. Santos.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
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Karabulut, Metin. "Production And Characterization Of Nanocomposite Materials From Recycled Thermoplastics." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1255728/index.pdf.
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Nanocomposites are a new class of mineral-field plastics that contain relatively small amounts (<10%) of nanometer-sized clay particles. The particles, due to their extremely high aspect ratios (about 100-15000), and high surface area (in excess of 750-800 m2/g) promise to improve structural, mechanical, flame retardant, thermal and barrier properties without substantially increasing the density or reducing the light transmission properties of the base polymer. Production of thermoplastic based nanocomposites involves melt mixing the base polymer and layered silicate powders that have been modified with hydroxyl terminated quaternary ammonium salt. During mixing, polymer chains diffuse from the bulk polymer into the van der Waals galleries between the silicate layers. In this study, new nanocomposite materials were produced from the components of recycled thermoplastic as the matrix and montmorillonite as the filler by using a co-rotating twin screw extruder. During the study, recycled poly(ethylene terepthalate), R-PET, was mixed with organically modified quaternary alkylammonium montmorillonite in the contents of 1, 2, and 5 weight %. Three types of clays were evaluated during the studies. For comparison, 2 weight % clay containing samples were prepared with three different clay types, Cloisite 15A, 25A, 30B. The nanocomposites were prepared at three different screw speeds, 150, 350, 500 rpm, in order to observe the property changes with the screw speed. Mechanical tests, scanning electron microscopy and melt flow index measurements were used to characterize the nanocomposites. The clay type of 25A having long alkyl sidegroups gave the best results in general. Owing to its branched nature, in nanocomposites with 25A mixing characteristics were enhanced leading to better dispersion of clay platelets. This effect was observed in the SEM micrographs as higher degrees of clay exfoliation. Nearly all the mechanical properties were found to increase with the processing speed of 350 rpm. In the studies, it was seen that the highest processing speed of 500 rpm does not give the material performance enhancements due to higher shear intensity which causes defect points in the structure. Also the residence time is smaller at high screw speeds, thus there is not enough time for exfoliation. In general, the MFI values showed minimum, thus the viscosity showed a maximum at the intermediate speed of 350 rpm. At this processing speed, maximum exfoliation took place giving rise to maximum viscosity. Also, the clay type of 25A produced the lowest MFI value at this speed, indicating the highest degree of exfoliation, highest viscosity, and best mechanical properties.
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Tunney, James J. "New nanocomposite materials from kaolinite as a mineral precursor." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9852.
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New thermally resistant nanocomposite organokaolinite material have been prepared and characterized. The preparation method for these materials generally involves first expanding the kaolinite interlayers with an intercalating agent such as dimethyl sulfoxide, followed by reaction with a given reagent in the interlayer space of the expanded kaolinite. In many cases the interlamellar surface of kaolinite was chemically modified through the grafting of organic units on the mineral surface. One new class of organokaolinite material was proposed to be formed through the interlayer condensation reaction between an alcohol group of the attacking species and an interlayer surface aluminol group of the kaolinite host to form Al-O-C linkages between the mineral and the organic components. In this manner, new chemically robust methoxy and ethylene glycol functionalized organokaolinites were prepared, with basal spacing of 8.2 A and 9.4A respectively. Furthermore, a new family of oxyethylene (-OCH$\sb2$CH$\sb2$-) based organokaolinite material was prepared and characterized. These materials include the species 15-crown-5 and 18-crown-6 as well as polyethylene glycol chains (MW 3400) which have been successfully incorporated into the interlayers of kaolinite. The products exhibit well defined basal spacings ranging from 10.8 Ato 11.2 A, indicative of a 3.6-4.0 A, layer expansion due to a flattened monolayer arrangement of the oxyethylene units. The materials were generally stable up to temperatures greater than 250$\sp\circ$C in both nitrogen and air atmospheres, but the oxyethylene component could be leached out in refluxing water. Finally, some promising exploratory work involving the functionalization of the interlamellar surface of kaolinite with aminoalcohols, carboxylic acid derivatives and other reagents is presented.
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Thyveetil, Mary-Ann. "Large-scale simulations of layered double hydroxide nanocomposite materials." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/16745/.
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Layered double hydroxides (LDHs) have generated a large amount of interest in recent years due to their ability to intercalate a multitude of anionic species. Atomistic simulation techniques such as molecular dynamics have provided considerable insight into the behaviour of these materials. The advent of supercomputing grids allows us to explore larger scale models with considerable ease. In this thesis we present our findings from large scale molecular dynamics simulations of Mg_2AI-LDHs intercalated with either chloride ions or a mixture of DNA and chloride ions. The system exhibits emergent properties, which are suppressed in smaller scale simulations. Undulatory modes are caused by the collective thermal motion of atoms in the LDH layers. Thermal undulations provide information about the materials properties of the system. In this way, we obtain values for elastic properties of the system including the bending modulus, Young's moduli and Poisson's ratios. The intercalation of DNA into LDHs has various applications, including drug delivery for gene therapy and origins of life studies. The nanoscale dimensions of the interlayer region make the exact conformation of the intercalated DNA difficult to elucidate experimentally. We use molecular dynamics techniques to perform simulations of double stranded, linear and plasmid DNA up to 480 base pairs in length intercalated within LDHs. Currently only limited experimental data has been reported for these systems. Our models are found to be in agreement with experimental observations, according to which hydration is a crucial factor in determining the structural stability of DNA. Phosphate backbone groups are found to align with aluminium lattice positions. At elevated temperatures and pressures, relevant to origins of life studies which maintain that the earliest life forms originated around deep ocean hydrothermal vents, the structural stability of LDH-intercalated DNA is substantially enhanced as compared to DNA in bulk water. We also discuss how the materials properties of the LDH are modified due to DNA intercalation. Recent experimental studies of LDHs have shown that these minerals can form staged intermediate structures during intercalation. However, the mechanism which produces staged structures remains undetermined. Our studies show that LDHs are flexible enough to deform around bulky intercalants such as DNA. The flexibility of layered materials has been shown to affect the pathway by which staging occurs. Even though the structures under study are all energetically very similar, overall there is greater diffusion of DNA strands in a Daumas-Hérold configuration compared to a Rüdorff model and a stage-1 structure.
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Wong, Ben. "The preparation of nanocomposite materials using supercritical carbon dioxide." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428928.
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Morley, Kelly Sarah. "The clean preparation of nanocomposite materials : a supercritical route." Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275912.
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OLIVEROS, MARTIN EMILIO MENDOZA. "SYNTHESIS, PROCESSING AND CHARACTERIZATION OF CU-CNT NANOCOMPOSITE MATERIALS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=13223@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O aumento do interesse em materiais nanoestruturados, nos anos recentes, tem incentivado o desenvolvimento de materiais compósitos de matriz metálica reforçados com nanotubos de carbono. No presente estudo foi produzido um material nano compósito de matriz de cobre contendo nanotubos de carbono (CNT 2% peso), a partir de síntese por métodos químicos. O procedimento começa pela dissociação do nitrato de cobre na presença de CNT e um tensoactivo aniônico a 250°C e sua posterior redução in-situ com atmosfera de Hidrogênio sobre pressão de 1 atm. a 350°C. A análise por difração de Raios X confirmou a formação de CuO puro no momento da dissociação, assim como de cobre metálico após a redução. A presença dos CNT foi detectada nas duas etapas por essa técnica. Análises por Microscopia Eletrônica de Transmissão (MET)mostram que o tamanho médio de partícula do óxido e de 30nm em quanto que para o material reduzido está na faixa de 150-300nm, apresentando-se boa dispersão dos nanotubos. O material reduzido foi compactado, em forma de pastilhas, por pressão uniaxial a frio sob 25MPa e, posteriormente, por pressão isostática a 150MPa. O material compactado foi sinterizado em atmosfera de Argônio a 650°C por 15 min. Análise por Microscopia Eletrônica de Varredura (MEV) assim como TEM do material sinterizado, mostrou uma distribuição heterogênea de tamanho de grão na faixa de 100nm a 4 μm. Medidas de resistividade elétrica mostram que o compósito apresenta uma resistividade sensivelmente menor a baixa temperatura (2x10(-6) ? .cm) a 83°K que o cobre sem nanotubos (5.9x10(-6) ? .cm).
The increasing interest in nanostructure materials in recent years has provided incentive to develop nanostructure composite materials with metal matrix, reinforced with carbon nanotubes. In the present work, copper matrix nano composite with carbon nanotubos (2% wt) was produced by chemical synthesis method. The procedure begins by the copper nitrate dissociation containing SWCNT and anionic tensoactive agent at 250°C, followed by in-situ reduction at 350°C, under hydrogen atmosphere at pressure of 1atm. CuO and Cu formation was confirmed by X ray diffraction at the moment of dissociation and reduction respectively. CNTs presence was detected at both steps by this characterization method. Transmission Electron Microscopy analysis, estimate particles grain size of 30nm for CuO powder while Cu powder particles were observed to be in the 100-300nm range, showing good dispersion of CNT. Bulk nano-composite pellets of the reduced material were obtained by pre-compactation under uniaxial pressure of 17 MPa followed by issostatic pressure of 150MPa. Sinterizing of the compacted material was carry out at 650°C under Argon atmosphere by 15 min. Scanning Electron Microscopy and Transmission Electron Microscopy analysis of the sinterized material showed an heterogeneous grain size distribution in the 100nm to 4 ìm range. Electric resistivity measures show that the nanocomposite material has lower resistivity at low temperature (2x10(-6) ? .cm) at 83°K than the copper without carbon nanotubes (5.9x10(-6) ? .cm).
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Farhatnia, Y. "Development of coronary artery covered stent using nanocomposite materials." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1416832/.
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Bare-metal stents (BMS) and drug-eluting stents (DES) are the two main categories of FDA-approved coronary stents in the market for treating atherosclerosis. Problems associated with BMS include in-stent restenosis due to intimal hyperplasia, leading to stent failure, while DES harbours a life-threatening complication called late-stent thrombosis due to drug-polymer hypersensitivity and impaired re-endothelialization. One approach to overcoming the above-mentioned problems could be using covered stents. Covered stents have an additional layer of membrane spanning the stent struts, and can be considered hybrid stent-grafts. Due to the added protection that the membrane affords, covered stents are currently used for vessel perforations and aneurysms. They can act as a physical barrier to inhibit smooth muscle cell in-growth and intimal hyperplasia formation. The most commonly used membrane for covered stents is expanded polytetrafluoethylene (ePTFE). However, its non-compliant and thrombogenic nature prevents it from being suitable for use in small-diameter vessels, resulting in an unmet clinical need for a haemocompatible covered stent for this application. A polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) nanocomposite polymer was developed by our group, and has already been used in three first-in-man studies as a bypass graft, lacrimal duct, and the world’s first synthetic trachea. Hence we sought to assess the feasibility of using POSS-PCU as a membrane for covered stents. Results indicate that POSS-PCU was haemocompatible, and was able to support the growth and proliferation of endothelial cells, compared to controls. Mechanical tests on membranes revealed that POSS-PCU was superior to ePTFE. Furthermore, it was also found that integration of POSS-PCU membrane onto stents did not adversely affect stent mechanics. In summary, the overall biomechanical performance of POSS-PCU indicates that it has the potential to function as a viable membrane material for covered stents in small diameter vessels.
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Conrad, Heidi Ann. "Electrochemically Deposited Metal Alloy-silicate Nanocomposite Corrosion Resistant Materials." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271794/.
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Zinc-nickel ?-phase silicate and copper-nickel silicate corrosion resistant coatings have been prepared via electrochemical methods to improve currently available corrosion resistant materials in the oil and gas industry. A layered silicate, montmorillonite, has been incorporated into the coatings for increased corrosion protection. For the zinc nickel silicate coatings, optimal plating conditions were determined to be a working pH range of 9.3 -9.5 with a borate based electrolyte solution, resulting in more uniform deposits and better corrosion protection of the basis metal as compared to acidic conditions. Quality, strongly adhering deposits were obtained quickly with strong, even overall coverage of the metal substrate. The corrosion current of the zinc-nickel-silicate coating is Icorr = 3.33E-6 for a borate based bath as compared to a zinc-nickel bath without silicate incorporation (Icorr = 3.52E-5). Step potential and direct potential methods were examined, showing a morphological advantage to step potential deposition. The effect of borate addition was examined in relation to zinc, nickel and zinc-nickel alloy deposition. Borate was found to affect the onset of hydrogen evolution and was examined for absorption onto the electrode surface. For copper-nickel silicate coatings, optimal conditions were determined to be a citrate based electrolytic bath, with pH = 6. The solutions were stable over time and strong adhering, compact particle deposits were obtained. The corrosion current of the copper-nickel-silicate coatings is Icorr = 3.86E-6 (copper-nickel coatings without silicate, Icorr = 1.78E-4). The large decrease in the corrosion current as the silicate is incorporated into the coating demonstrates the increase in corrosion resistance of the coatings with the incorporation of silicates.
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Fulvio, Pasquale Fernando. "Synthesis and Characterization of Ordered Mesoporous Inorganic Nanocomposite Materials." Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1258990927.
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Duan, Ruozhu. "Fabrication and Characterization of Organic Solar Cell Nanocomposite Materials." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1395406673.
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Eaves, Elizabeth. "Soft-soft nanocomposite coating materials produced by emulsion polymerisation." Thesis, University of Manchester, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654865.
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This thesis reports on the challenge of applying an innovative ‘soft-soft nanocomposite’ design strategy to establish synthesis parameters that affect the performance of coatings based upon water-borne latexes, which is driven by the environmental and legislative need to develop feasible alternatives to solvent-borne coatings. A framework emulsion polymerisation formulation to synthesise core-shell latexes with (poly[(butyl acrylate)-co-(butyl methacrylate)]) core and (poly[(butyl acrylate)-co-(butyl methacrylate)-co-(diacetone acrylamide)]) shell copolymer phases in a controlled manner was established, with high monomer conversions and approximately constant particle numbers. Retention of particle morphology in the films was confirmed using atomic force microscopy (AFM). The effect of adding adipic acid dihydrazide to the latex post-polymerisation to facilitate crosslinking of the shell phase during film formation was found to have a significant effect on the stress-strain properties of latex films. A core:shell mass ratio of 80:20 was found to be optimum in all crosslinked systems tested. Increasing the amount of crosslinking in the shell phase of the particles was found to have an effect on the large strain tensile properties of films, leading to strain hardening with reduced extension to break and higher failure stresses at higher crosslinker levels. Core phase copolymer Tg had a very significant effect upon the low strain mechanical properties, with Young’s modulus values of 5-180 MPa being accessible in the range of core Tg¬s from 5 – 25 oC, although little difference in mechanical behaviour was seen when varying the shell phase Tg from 5 – 15 oC. Adding 2 wt% methacrylic acid (MAA) to the shell phase copolymer gave an additional improvement in the low strain tensile region, with a Young’s modulus of 425 MPa being realised. However, it was found that additional amounts of MAA (up to 5 wt% in the shell phase) were deterious to film properties, with low Young’s modulus and poor extensibility. This was interpreted as being due to an increased concentration of ionomeric crosslinks restricting interparticle chain diffusion and keto-hydrazide crosslinking. Studies to evaluate the mechanical performance of soft-soft nanocomposite films compared to binder latexes used in commercial products were favourable, and showed that a high level of versatility with regards to mechanical properties is possible.
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Kim, Bo Yun. "Preparation of Electro- and Magneto-Active Hybrid Nanocomposite Materials." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145390.
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This dissertation describes the preparation and characterization of magneto and electro-active hybrid nanocomposite materials. In this research, two hybrid nanocomposite materials, gold-cobalt oxide nanowires and ferrocene functional polymer brushes on electrode surface, were investigated. Polymerizations of magnetic colloidal monomers to form electro-active nanowires and ferrocene functional monomers on electrode to form electro-active polymer brushes were demonstrated. The central focus of this research is utilizing colloidal polymerization and surface-initiated polymerization to prepare electro-active hybrid nanocomposite materials for potential applications in energy storage and conversion.Colloidal polymerization has been developed as a novel synthetic methodology to prepare 1-D mesostructures via dipolar assembly and chemical reaction. This method was exploited to synthesize multicomponent 1-D nanowires by using polymer-coated ferromagnetic gold-cobalt core-shell nanoparticles as colloidal monomers. Prepared semiconductor cobalt oxide nanowires with gold inclusions exhibited enhanced optical and electrochemical properties compared to cobalt oxide nanowires. This research provided a platform in fabricating a wide range multicomponent semiconductor nanowires as new nanostructured electrodes for potential applications in energy storage and conversion. Further, self-assembled gold-cobalt core-shell nanoparticles were utilized to align novel gold nanoparticles on a substrate. This facile and template free approach enabled the linear and ring assembly of noble gold metal on a substrate.Indium tin oxide (ITO) thin films are key components as transparent electrodes in a number of optoelectronic devices. The modification of ITO surfaces with polymers via electropolymerization has been widely investigated to improve surface compatibility and charge injection from the interface. However, there remain challenges to prepare polymers possessing, well-defined interfacial chemistry, molecular weight, composition, and functionality. This dissertation provides a modular synthetic methodology to prepare ferrocene functional polymer brushes on ITO via surface-initiated atom transfer radical polymerization (SI-ATRP). This work provided a simple model study to enable direct electrochemical and topographic characterization of well-defined polymer brushes on ITO with controlled molar mass and composition. These ITO grafted polymer brushes are also a novel model system for optoelectronic materials, where the effect of chain alignment and morphology can be correlated with electrical and electrochemical properties.
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Bell, Bryan Frederick Jr. "Functionally graded, multilayer diamondlike carbon-hydroxyapatite nanocomposite coatings for orthopedic implants." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7962.
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Li, Qiaochu Ph D. Massachusetts Institute of Technology. "Designing dynamic mechanics in self-healing nanocomposite hydrogels." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115711.
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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 127-136).
The functional versatility and endurable self-healing capacity of soft materials in nature is found to originate from the dynamic supramolecular scaffolds assembled via reversible interactions. To mimic this strategy, extensive efforts have been made to design polymer networks with transient crosslinks, which lays the foundation for synthetic self-healing hydrogels. Towards the development of stronger and faster self-healing hydrogels, understanding and controlling the gel network dynamics is of critical importance, since it provides design principles for key properties such as dynamic mechanics and self-healing performance. For this purpose, a universal strategy independent of exact crosslinking chemistry would be regulating the polymer material's dynamic behavior by optimal network design, yet current understanding of the relationship between network structure and macroscopic dynamic mechanics is still limited, and implementation of complex network structure has always been challenging. In this thesis, we show how the dynamic mechanical properties in a hydrogel can be controlled by rational design of polymer network structures. Using mussel-inspired reversible catechol coordination chemistry, we developed a nanocomposite hydrogel network (NP gel) with hierarchical assembly of polymer chains on iron oxide (Fe3O4) nanoparticles as network crosslinks. With NP gel as a model system, we first investigated its unique dynamic mechanics in comparison with traditional permanent and dynamic gels, and discovered a general approach to manipulate the network dynamics by controlling the crosslink structural functionality. Then we further explored the underlying relationship between polymer network structure and two key parameters in relaxation mechanics, which elucidated universal approaches for designing relaxation patterns in supramolecular transient gel network. Finally, by utilizing these design principles, we designed a hybrid gel network using two crosslinking structures with distinct relaxation timescales. By simply adjusting the ratio of two crosslinks, we can precisely tune the material's dynamic mechanics from a viscoelastic fluid to a rigid solid. Such controllability in dynamic mechanics enabled performance optimization towards mechanically rigid and fast self-healing hydrogel materials.
by Qiaochu Li.
Ph. D.
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Bell, Bryan Frederick. "Functionally graded, multilayer diamondlike carbon-hydroxyapatite nanocomposite coatings for orthopedic implants." Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131058/unrestricted/bell%5Fbryan%5Ff%5F200405%5Fms.pdf.
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Patel, Alpa C. Wei Yen. "Bioapplicable, nanostructured and nanocomposite materials for catalytic and biosensor applications /." Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1124.
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Sener, Canan. "Synthesis And Characterization Of Pd-mcm-type Mesoporous Nanocomposite Materials." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12606987/index.pdf.
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Noble metal incorporated MCM-41 based nanostructured mesoporous materials have attracted the attention of material researchers in recent years. Sorption characteristics of MCM materials can be improved by surface modification techniques. Besides surface modification, metal nanoparticles can also be produced within the pores of mesoporous materials. MCM-41 can act as host for several metal nanoparticles such as palladium.
The present study is focused on the synthesis of Pd-MCM-41 nanocomposite catalytic materials by using different direct synthesis procedures, as well as an impregnation method. Impregnated samples were used to synthesize Pd nanoparticles inside the pores of MCM-41. In the direct hydrothermal synthesis of Pd-MCM-41, incorporation of the Pd metal was achieved by adding PdCl2, K2PdCl4 and Pd(NH3)4(NO2)3 solutions into the synthesis mixture. Syntheses were performed in acidic and basic routes. Hydrothermal synthesis was carried out in an autoclave at 120 oC. The solid product was filtered, washed, dried, calcined at 550 oC in a stream of dry air and reduced in a stream of hydrogen at 200 oC. In the case of impregnation, PdCl2 solution was added to a suspension of MCM-41. The product was evaporated to dryness, dried under vacuum and reduced with H2 gas at 200 oC. Physical and chemical properties and surface morphology of Pd-MCM-41 nanomaterials were characterized by using XRD, XPS, EDS, BET, SEM, TEM and TPR techniques.
Very high Pd/Si ratios, as high as 0.45 and 0.18 were obtained in the mesoporous materials produced by the basic and acidic direct synthesis routes, respectively. The BET surface areas of these materials were found as 999 m2/g and 694 m2/g, respectively. These results showed that the basic direct synthesis procedure was highly successful for the incorporation of Pd into the mesoporous Si structure. In addition, EDS analysis of the Pd-MCM-41 materials prepared by the impregnation technique showed that Pd/Si ratios were 0.24 and 0.12 in the two samples having surface areas of 527 m2/g and 883 m2/g, respectively.
In conclusion, high surface area of the material synthesized by the basic route together with a higher Pd/Si ratio makes this material more attractive for catalytic and hydrogen storage applications.
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Minnich, Austin (Austin Jerome). "Modeling the thermoelectric properties of bulk and nanocomposite thermoelectric materials." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44852.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 95-99).
Thermoelectric materials are materials which are capable of converting heat directly into electricity. They have long been used in specialized fields where high reliability is needed, such as space power generation. Recently, certain nanostructured materials have been fabricated with high thermoelectric properties than those of commercial bulk materials, leading to a renewed interest in thermoelectrics. One of these types of nanostructured materials is nanocomposites, which are materials with either nanosized grains or particles on the nanometer scale embedded in a host material. Nanocomposites present many challenges in modeling due to their random nature and unknown grain boundary scattering mechanisms. In this thesis we introduce new models for phonon and electron transport in nanocomposites. For phonon modeling we develop an analytical formula for the phonon thermal conductivity using the effective medium approximation, while for electron modeling and more detailed phonon modeling we use the Boltzmann equation to calculate the thermoelectric properties. To model nanocomposites we incorporate a grain boundary scattering relaxation time. The models allow us to better understand the transport processes in nanocomposites and help identify strategies for material selection and fabrication.
by Austin Minnich.
S.M.
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Chen, Chen. "The Manufacture of Polymer Nanocomposite Materials Using Supercritical Carbon Dioxide." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/30020.
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The use of supercritical carbon dioxide (scCO2) as a processing aid to help exfoliate nano-clays and improve their dispersion during melt blending in polymer matrices has been reported in the literature. One of the best processes in terms of improving the degree of nano-clay dispersion and composite mechanical properties was developed in our laboratory. This process allows the clay to be in direct contact with scCO2 and expanding the clay-CO2 mixture via rapid depressurization into a two-stage screw extruder to mix with the polymer pellets. However, composites with clay loading higher than 6.6 wt % were not reported. In addition, the scCO2 aided processing method has not been applied to carbon nanotube (CNT) based composites.
This dissertation initially focused on applying the scCO2 aided processing technique to the field of CNT expansion and CNT/polymer composite preparation. The relationship with the expanded CNT morphology and the experimental conditions of the expansion procedure (including pressures, temperatures, exposure time, and depressurization rates) was studied. Microscopy results showed improved CNT dispersion in the polymer matrix and more uniform networks formed with the use of scCO2, which indicated that CO2 expanded CNTs are easier to disperse into the polymer matrix during the blending procedure. The CNT/ poly(phenylsulfone) (PPSF) composites prepared with scCO2 aided method provided continuous improvements in Youngâ s modulus up to the addition of 7 wt % CNTs. However, the Youngâ s modulus of the composite prepared by means of conventional direct melt blending failed to increase beyond the addition of 1 wt % CNT.
The second part of this work is concerned with the development of a semi-continuous process using scCO2 to process polymer-clay composites with clay loading higher than 6.6 wt % (i.e. 10 wt %). Two major modifications are involved in the new procedure: exfoliating the nano-clay directly into the hopper filled with pellets followed by processing the composite immediately and sequentially mixing the clay into the melt. Transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) results show that this modified procedure help to reduce the clay collapse when processing the composites with high clay loadings. Surface modified montmorillonite (MMT) nano-clay/polypropylene (PP) composite at 10 wt % nano-clay with improved clay dispersion was obtained with increased modulus and tensile strength of 63 % and 16%, respectively, compared to the pure PP matrix.
Additional mechanical property improvements for nano-clay based composites are then obtained with the use of high crystallinity polypropylene (HCPP) and polypropylene grafted with maleic anhydride (PP-g-MA). HCPP has higher crystallinity and stiffness than conventional PP and, therefore, composites made from HCPP have better mechanical properties to start with. PP-g-MA has polar groups grafted on the PP chains that promote the intercalation of PP with clay. By using the newly developed procedure, the HCPP nanocomposite at 10 wt % of nano-clay has a Youngâ s modulus as high as 3.236 GPa, and the modulus of the 10% MMT/PP-g-MA sample is found to be 2.595 GPa, both higher than that of the composite prepared by the direct blending method and that of a composite based on a conventional PP matrix.Ph. D.
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Chang, Tae-Eun. "Microscopic mechanism of reinforcement and conductivity in polymer nanocomposite materials." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1176746415.
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England, M. W. "Synthesis and characterisation of self-assembled host-guest nanocomposite materials." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682677.
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One of the challenges within nanoscience is the formation of nanoparticles of a consistent size, shape, and spatial arrangement. One solution to this problem is to incorporate guest molecules into larger hosts for confined nanoscale synthesis. The central theme of this thesis is the formation of novel nanocomposites using this host-guest approach. Cross-linked tetragonal lysozyme crystals and hydrophobic 2:1 phyllosilicate clays were utilized as the host materials for the synthesis of nanostructured arrays, and were characterised using optical microscopy, SEM, TEM, EDX, FTIR, UV-vis and TGA. Tetragonal lysozyme crystals were grown, cross-linked, and characterised before being infiltrated with various precursors. An oxidising agent was infiltrated along with heterocyclic monomers to form high aspect ratio wires of the conducting polymers polypyrrole and polyaniline. Cross-linked lysozyme crystals were also used for the deposition of arrays of plasmonically active gold and silver, by chemical and photoreduction, respectively. The internal metallic structure of the protein/metal composites were then modelled using advanced UV-vis and fluorescence spectroscopy to reveal the presence of prolate spheroidal nanoclusters. Finally, microwave-assisted pyrolysis was used to synthesise intracrystalline arrays of highly fluorescent nanoscale carbon dots from a precursor solution of citric acid and ethylene diamine. The carbon nanostructures could be released from the protein crystals via treatment with a solution of sodium borohydride, and could also have their fluorescence emissions tuned by infiltration of fluorescent dye molecules. Finally, three novel 2: 1 phyllosilicateorganoclays were synthesised with pendant propyl, octyl, and octadecyl chains using a one-step sol-gel method. The octyl clay was used to accommodate a palladium (11) complex that was subsequently reduced into Pdo nanoparticles within the clay structure. All of the clays and the clay/nanoparticle composite were found to be hydrophobic, and could be exfoliated in toluene to form water-in-oil Pickering emulsions, which were chemically crosslinked to form colloidosomes
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Li, Wenqi. "LIGNIN-DERIVED CARBON AND NANOCOMPOSITE MATERIALS FOR ENERGY STORAGE APPLICATIONS." UKnowledge, 2019. https://uknowledge.uky.edu/bae_etds/68.
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With a growing demand for electrical energy storage materials, lignin-derived carbon materials have received increasing attention in recent years. As a highly abundant renewable carbon source, lignin can be converted to a variety of advanced carbon materials with tailorable chemical, structural, mechanical and electrochemical properties through thermochemical conversion (e.g. pyrolysis). However, the non-uniformity in lignin structure, composition, inter-unit linkages and reactivity of diverse lignin sources greatly influence lignin fractionation from plant biomass, the pyrolysis chemistry, and property of the resulting carbon materials.
To introduce a better use of lignocellulosic biomass to biofuels and co-products, it is necessary to find novel ways to fractionate lignin and cellulose from the feedstock at high efficacy and low cost. Deep eutectic solvent (DES) was used to extract lignin from high lignin-content walnut and peach endocarps. Over 90% sugar yields were achieved during enzymatic hydrolysis of DES pretreated peach and walnut endocarps while lignins were extracted at high yields and purity. The molecular weights of the extracted lignin from DES pretreated endocarp biomass were significantly reduced. The native endocarp lignins were SGH type lignins with dominant G-unit. DES pretreatment decreased the S and H-unit which led to an increase in condensed G-units, which may contribute to a higher thermal stability of the isolated lignin.
Lignin slow pyrolysis was investigated using a commercial pyrolysis–GC/MS system for the first time to link pyrolysis chemistry and carbon material properties. The overall product distributions, including volatiles and solid product were tracked at different heating rates (2, 20, 40 ℃/min) and different temperature regions (100-200, 200-300 and 300-600 ℃). Results demonstrate that changes in reaction chemistry as a factor of pyrolysis conditions led to changes in yield and properties of the resulting carbon materials. Physical and chemical properties of the resulting carbon material, such as porosity, chemical composition and surface functional groups were greatly affected by lignin slow pyrolysis temperature and heating rate.
Lignin-derived activated carbons (AC) were synthesized from three different lignin sources: poplar, pine derived alkaline lignin and commercial kraft lignin under identical conditions. The poplar lignin-derived ACs exhibited a larger surface area and total mesopore volume than softwood lignin-derived AC, which contribute to a larger electrochemical capacitance over a range of scan rates. The presence of oxygen-containing functional groups in all lignin-derived ACs, which participated in redox reaction and thus contributed to an additional pseudo-capacitance. By delineating the carbonization and activation parameters, results from this study suggest that lignin structure and composition are important factors determining the pore structure and electrochemical properties of the derived carbon materials.
A 3-dimensional, interconnected carbon/silicon nanoparticles composite synthesized from kraft lignin (KL) and silicon nanoparticles (Si NPs) is shown to have a high starting specific capacity of 2932 mAh/g and a retaining capacity of 1760 mAh/g after 100 cycles at 0.72 A/g as negative electrode in a half-cell lithium-ion battery (LIB) test. It was found the elemental Si and C of the C/Si NPs were most likely linked via Si-O-C rather than direct Si-C bond, a feature that helps to alleviate the mechanical degradation from Si volume change and assure a sound electronic and ionic conductivity for enhanced electrochemical performance. EGA-MS and HC-GC/MS analyses suggest that the interaction of the Si, O and C can be tailored by controlling pyrolysis conditions.
This study systematically investigated the interconnecting aspects among lignin source, pyrolysis chemistry, characteristics of the derived carbon materials and electrochemical performance. Such knowledge on the processing-structure-function relationships serves as a basis for designing lignin-based carbon materials for electrochemical energy storage applications.
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Schiavoni, M. L. "BIFUNCTIONAL NANOCOMPOSITE MATERIALS AS LONG-LIFE CATALYSTS FOR BIOMASS VALORIZATION." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/244734.
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Phosphorylated mesoporous carbons (PMCs) were investigated as catalysts in the dehydration of fructose to hydroxymethylfurfural (HMF). The acidic PMCs show better selectivity to HMF compared to sulfonated carbon catalyst (SC) despite lower activity. The concentration of P–O groups on the PMC was correlated with the activity/selectivity of the catalysts; the higher the P–O concentration, the higher the activity. However, the higher the P–O content, the lower the selectivity to HMF. Indeed, a lower concentration of the P–O groups minimized the degradation of HMF to levulinic acid and the formation of by-products, such as humines. Stability tests showed that these systems deactivate due to the formation of humines and water insoluble by-products derived from the dehydration of fructose which blocked the catalytically active sites.
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CRIPPA, MAURIZIO. "Hybrid and nanocomposite concepts: a driving force for novel materials." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/42253.
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The general concepts of hybrid and nanocomposite were used not only to classify but also to drive the synthesis optimizing the materials for the different applications.
The common denominator of each material was the titanium dioxide as photoreactive material, chapters 3 and 4, and dielectric material in chapter 5. Because both the morphology and the crystal phase of the titanium dioxide play a crucial role on the material performances the used TiO2 was always synthesized ex situ by hydrothermal synthesis allowing to control the morphological characteristics. In the chapter 3 and 4 anatase phase was used for its photocatalytic ability in presence of oxygen and water while in the chapter 5 the rutile phase was used because its highest dielectric constant compare anatase.
In chapter 3 a polyacrilate composite material prepared by mechanical mixing of nanocrystalline titania with acrylate oligomers shows that, without titania surface functionalisation, the oxide forms micrometric aggregates reducing the exposed surface of the TiO2. Despite the filler aggregation the material preserves its photocatalytic properties. As drawback of the photocatalytic activity in phenol photomineralisation (use to simulate pollutants in water) some photooxidative degradation phenomena involve the organic matrix. Hence the necessity to have a stable material was the driving force to create a new material containing titania as photoactive material while embedded into an inorganic matrix.
In the chapter 4 this porous and UV transparent inorganic-inorganic nanocomposite material is described. In order to obtain the desired porosity of the final material the silica sol-gel solution was mixed with PEG obtaining a class I hybrid material. During the silica formation PEG segregates in warm-like polymeric phase that, once the material is calcinated, leaves the voids conferring the desired macroporosity to the material. The photoactive oxide, previously functionalized on the surface with organic molecules, migrates in the polymeric phase during silica precursors hydrolysis and condensation. After calcination the titania nanocrystallites decorate the wall of the channels leaved by the organic species remotion. The molecules functionalizing the catalyst surface induce the TiO2 migration into the PEG phase because of their more affinity with polymer instead with silica. The exposed titania is then able to freely react with pollutants while the silica matrix provides the UV transparency and macroporosity for the photocatalytic reactions. The abatement efficiency of the material is comparable with slurry TiO2. The material is not affected by the photocatalyst leaching demonstrating that it is suitable for an industrial application. The nanocomposite material was tested for NOx degradation too using P25 commercial titania instead of home made one demonstrating the generality of the preparation method. The abatement efficiency of the NOx was comparable with the DENOX technology currently used for industrial applications.
In chapter 5 the same reaction technique used to functionalize the nanoparticles in the chapter 4 was used to functionalize rutile titania nanoparticles with a RAFT reagent. After the styrene “polymerization from” reaction polystyrene chains were obtained. The brush like conformation of the chains justifies the high polymer surface density. The functionalized nanoparticles (class II material) are mixed in different concentrations with commercial polystyrene. The different concentration materials present good dispersion because of the high compatibilization properties of the surface functionalisation. At high concentrations the material shows a percolative behavior ascribed to the formation of chestnut like aggregates which increase the relative dielectric constant. Despite the charges percolation trough the material the polymeric surface layer acts as an insulating layer which contributes to mitigate the charge mobility and consequently the conductivity of the material. The low conductivity of the material allows to obtain low tanδ values.
The low tanδ values in a large range of frequencies allows to candidate the material for radio frequency (RF) applications where very low dissipation factor is desired to avoid signal losses.
In conclusion the present work, despite it covers three different materials, demonstrates how it is possible to create and optimize a material modifying the surface of the nanoparticles in order to confer them peculiar properties which drive the final material morphology. The final material morphology is then able to combine the properties both of the active material and of the matrix giving a new optimized material for a specific application.
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Cai, Bing. "Ceramic Materials for Administration of Potent Drugs." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-245031.
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This thesis aimed to investigate and document the potential of applying ceramics in two specific drug delivery applications: tamper-resistant opioid formulations and transdermal enhancement protrusions. Geopolymers were developed into the matrix for a tamper-resistant formulation, aiming to protect drug substances from non-medical abuse. The synthesis conditions and excipients composition of the geopolymer-based formulation were modified in this work to facilitate a stable and extended drug delivery. Results showed that 37ºC 100% humidity for 48 hours were applicable conditions to obtain geopolymer with suitable mechanical strength and porosity. Moreover, it was found that the integration of poly(methyl acrylate) into the geopolymer-based formulation could reduce the drug release at low pH and, meanwhile, maintain the mechanical strength. Therefore, the geopolymer-based drug formulations concluded from these studies were applied in oral and transdermal delivery systems. Evidence of the tamper-resistance of geopolymer-based oral and transdermal formulations was documented and compared to the corresponding commercial opioid formulations. The results provided experimental support for the positive effects of geopolymers as drug carriers for the tamper-resistance of oral and transdermal delivery systems. Self-setting bioceramics, calcium phosphate and calcium sulfate were fabricated into transdermal enhancement protrusions in this work for the first time. Results showed that, under mild conditions, both bioceramics could form pyramid-shaped needles in the micron size. The drug release from these needles could be controlled by the bulk surface area, porosity and degradation of the bioceramics. An in vitro insertion test showed that the bioceramic microneedles had enough mechanical strength to insert into skin. Further optimization on the geometry of needles and the substrate material was also performed. The higher aspect-ratio needles with a flexible and self-swellable substrate could release most of the drug content within 4 hours and could penetrate through the stratum corneum by manual insertion. This study explored the potential application of bioceramics in transdermal enhancement protrusions and showed promising indication of their future developments.