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Dissertations / Theses on the topic 'Polymeric composites. Graphite. Nanostructured materials'
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1
Geng, Yan. "Preparation and characterization of graphite nanoplatelet, graphene and graphene-polymer nanocomposites /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20GENG.
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Wang, Shu Jun. "Applications of graphene for transparent conductors and polymer nanocomposites /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20WANGS.
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Kalaitzidou, Kyriaki. "Exfoliated graphite nanoplatelets as reinforcement for multifunctional polypropylene nanocomposites." Diss., Connect to online resource - MSU authorized users, 2006.
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Thesis (Ph. D.)--Michigan State University. Dept. of Chemical Engineering and Materials Science, 2006.<br>Title from PDF t.p. (viewed on June 19, 2009) Includes bibliographical references. Also issued in print.
4
Basnayaka, Punya A. "Development of Nanostructured Graphene/Conducting Polymer Composite Materials for Supercapacitor Applications." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4864.
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The developments in mobile/portable electronics and alternative energy vehicles prompted engineers and researchers to develop electrochemical energy storage devices called supercapacitors, as the third generation type capacitors. Most of the research and development on supercapacitors focus on electrode materials, electrolytes and hybridization. Some attempts have been directed towards increasing the energy density by employing electroactive materials, such as metal oxides and conducting polymers (CPs). However, the high cost and toxicity of applicable metal oxides and poor long term stability of CPs paved the way to alternative electrode materials. The electroactive materials with carbon particles in composites have been used substantially to improve the stability of supercapacitors. Furthermore, the use of carbon particles and CPs could significantly reduce the cost of supercapacitor electrodes compared to metal oxides. Recent developments in carbon allotropes, such as carbon nanotubes (CNTs) and especially graphene (G), have found applications in supercapacitors because of their enhanced double layer capacitance due to the large surface area, electrochemical stability, and excellent mechanical and thermal properties.
The main objective of the research presented in this dissertation is to increase the energy density of supercapacitors by the development of nanocomposite materials composed of graphene and different CPs, such as: (a) polyaniline derivatives (polyaniline (PANI), methoxy (-OCH3) aniline (POA) and methyl (-CH3) aniline (POT), (b) poly(3-4 ethylenedioxythiophene) (PEDOT) and (c) polypyrrole (PPy). The research was carried out in two phases, namely, (i) the development and performance evaluation of G-CP (graphene in conducting polymers) electrodes for supercapacitors, and (ii) the fabrication and testing of the coin cell supercapacitors with G-CP electrodes.
In the first phase, the synthesis of different morphological structures of CPs as well as their composites with graphene was carried out, and the synthesized nanostructures were characterized by different physical, chemical and thermal characterization techniques, such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, BET surface area pore size distribution analysis and Thermogravimetric Analysis (TGA). The electrochemical properties of G-CP nanocomposite-based supercapacitors were investigated using Cyclic Voltammetry (CV), galvanostatic charge-discharge and Electrochemical Impedance Spectroscopy (EIS) techniques in different electrolytes, such as acidic (2M H2SO4 and HCl), organic ( 0.2 M LiClO4) and ionic liquid (1M BMIM-PF6) electrolytes.
A comparative study was carried out to investigate the capacitive properties of G-PANI derivatives for supercapacitor applications. The methyl substituted polyaniline with graphene as a nanocomposite (G-POT) exhibited a better capacitance (425 F/g) than the G-PANI or the G-POA nanocomposite due to the electron donating group of G-POT. The relaxation time constants of 0.6, 2.5, and 5s for the G-POT, G-PANI and G-POA nanocomposite-based supercapacitors were calculated from the complex model by using the experimental EIS data.
The specific capacitances of two-electrode system supercapacitor cells were estimated as 425, 400, 380, 305 and 267 F/g for G-POT, G-PANI, G-POA, G-PEDOT and G-PPy, respectively. The improvements in specific capacitance were observed due to the increased surface area with mesoporous nanocomposite structures (5~10 nm pore size distribution) and the pseudocapacitance effect due to the redox properties of the CPs. Further, the operating voltage of G-CP supercapacitors was increased to 3.5 V by employing an ionic liquid electrolyte, compared to 1.5 V operating voltage when aqueous electrolytes were used. On top of the gain in the operating voltage, the graphene nano-filler of the nanocomposite prevented the degradation of the CPs in the long term charging and discharging processes.
In the second phase, after studying the material's chemistry and capacitive properties in three-electrode and two-electrode configuration-based basic electrochemical test cells, coin cell type supercapacitors were fabricated using G-CP nanocomposite electrodes to validate the tested G-CPs as devices. The fabrication process was optimized for the applied force and the number of spacers in crimping the two electrodes together. The pseudocapacitance and double layer capacitance values were extracted by fitting experimental EIS data to a proposed equivalent circuit, and the pseudocapacitive effect was found to be higher with G-PANI derivative nanocomposites than with the other studied G-CP nanocomposites due to the multiple redox states of G-PANI derivatives. The increased specific capacitance, voltage and small relaxation time constants of the G-CPs paved the way for the fabrication of safe, stable and high energy density supercapacitors.
5
Cheung, Man Kuen. "Investigating the tribological performance of different polymer and polymer nanocomposites using nanoscratch and wear techniques /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?mphil-ap-b19887772a.pdf.
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Thesis (M.Phil.)--City University of Hong Kong, 2005.<br>"Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Master of Philosophy" Includes bibliographical references (leaves 82-95)
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Zhao, Hongxia. "Studies of thermal, mechanical and fracture behaviors of rigid nanoparticulates filled polymeric composites /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ap-b19887589a.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2005.<br>"Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references.
7
Sahu, Laxmi Kumari D'Souza Nandika Anne. "Bulk and interfacial effects on density in polymer nanocomposites." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3619.
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8
Maniar, Ketan K. "A literature survey on nanocomposites." Full text available online (restricted access) Full text available online (restricted access), 2002. http://images.lib.monash.edu.au/ts/theses/maniar.pdf.
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Işık, Kıvanç Tanoğlu Metin. "Layered silicate/polypropylene nanocomposites/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/makinamuh/T000532.pdf.
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Olea, Mejía Oscar Fernando Brostow Witold. "Micro and nano composites composed of a polymer matrix and a metal disperse phase." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5135.
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Bhardwaj, Mohit. "Water vapor diffusion through glass fiber reinforced polymer nanocomposites." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4193.
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Thesis (M.S.)--West Virginia University, 2005.<br>Title from document title page. Document formatted into pages; contains x, 133 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 116-118).
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Wong, Kwok Wai. "Preparation and crystallization characterization of polypropylene-layered silicate clay nanocomposites." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175184a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.
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Yiu, Stephen Cheuk Bun. "Crystallization, structure and mechanical characteristics of polymer-silicate nanocomposites." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175329a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.
14
Kwok, Yee Shan. "Crystallization, structure and mechanical characteristics of polymer-silicate nanocomposites." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174386a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.
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Brown, Elvie Escorro. "Bacterial cellulose/thermoplastic polymer nanocomposites." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Spring2007/e_brown_050207.pdf.
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Wang, Huan. "Synthesis, purification and applications of carbon nanomaterials and their polymer nanocomposites /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CBME%202008%20WANG.
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Krikorian, Vahik. "Bio-nanocomposites fabrication and characterization of layered silicate nanocomposites based on biocompatible/biodegradable polymers / by Vahik Krikorian." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file , 11.06 Mb, 148 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/3187609.
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Du, Ying. "Fabrication and characterization of particulate polymer nanocomposites /." View online ; access limited to URI, 2007. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3284823.
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Liu, Jia. "Polymer-layered silicate nanocomposites : synthesis, structure and properties /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?MECH%202004%20LIU.
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Ranade, Ajit. "Barrier and Long Term Creep Properties of Polymer Nanocomposites." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc5563/.
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The barrier properties and long term strength retention of polymers are of significant importance in a number of applications. Enhanced lifetime food packaging, substrates for OLED based flexible displays and long duration scientific balloons are among them. Higher material requirements in these applications drive the need for an accurate measurement system. Therefore, a new system was engineered with enhanced sensitivity and accuracy. Permeability of polymers is affected by permeant solubility and diffusion. One effort to decrease diffusion rates is via increasing the transport path length. We explore this through dispersion of layered silicates into polymers. Layered silicates with effective aspect ratio of 1000:1 have shown promise in improving the barrier and mechanical properties of polymers. The surface of these inorganic silicates was modified with surfactants to improve the interaction with organic polymers. The micro and nanoscale dispersion of the layered silicates was probed using optical and transmission microscopy as well as x-ray diffraction. Thermal transitions were analyzed using differential scanning calorimetry. Mechanical and permeability measurements were correlated to the dispersion and increased density. The essential structure-property relationships were established by comparing semicrystalline and amorphous polymers. Semicrystalline polymers selected were nylon-6 and polyethylene terephthalate. The amorphous polymer was polyethylene terphthalate-glycol. Densification due to the layered silicate in both semicrystalline and amorphous polymers was associated with significant impact on barrier and long term creep behavior. The inferences were confirmed by investigating a semi-crystalline polymer - polyethylene - above and below the glass transition. The results show that the layered silicate influences the amorphous segments in polymers and barrier properties are affected by synergistic influences of densification and uniform dispersion of the layered silicates.
21
Liang, Qizhen. "Preparation and properties of thermally/electrically conductive material architecture based on graphene and other nanomaterials." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44846.
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With excellent electrical, thermal and mechanical properties as well as large specific surface area, graphene has been applied in next-generation nano-electronics, gas sensors, transparent electrical conductors, thermally conductive materials, and superior energy capacitors etc. Convenient and productive preparation of graphene is thereby especially important and strongly desired for its manifold applications.
Chemically developed functionalized graphene from graphene oxide (GO) has significantly high productivity and low cost, however, toxic chemical reduction agents (e.g. hydrazine hydrate) and raised temperature (400-1100°C) are usually necessary in GO reduction yet not preferred in current technologies. Here, microwaves (MW) are applied to reduce the amount of graphene oxide (GO) at a relatively low temperature (~165°C). Experimental results indicate that resurgence of interconnected graphene-like domains contributes to a low sheet resistance with a high optical transparency after MW reduction, indicating the very high efficiency of MW in GO's reduction.
Moreover, graphene is usually recumbent on solid substrates, while vertically aligned graphene architecture on solid substrate is rarely available and less studied. For TIMs, electrodes of ultracapacitors, etc, efficient heat dissipation and electrical conductance in normal direction of solid surfaces is strongly desired. In addition, large-volume heat dissipation requires a joint contribution of a large number of graphene sheets. Graphene sheets must be aligned in a large scale array in order to meet the requirements for TIM application. Here, thermally conductive fuctionalized multilayer graphene sheets (fMGs) are efficiently aligned in a large scale by vacuum filtration method at room temperature, as evidenced by SEM images and polarized Raman spectroscopy. A remarkably strong anisotropy in properties of aligned fMGs is observed. Moreover, VA-fMG TIMs are prepared by constructing a three-dimensional vertically aligned functionalized multilayer graphene architecture between contact Silicon/Silicon surfaces with pure Indium as a metallic medium. Compared with their counterpart from recumbent A-fMGs, VA-fMG TIMs have significantly higher equivalent thermal conductivity and lower contact thermal resistance.
Electrical and thermal conductivities of polymer composite are also greatly interested here. Previous researches indicated that filler loading, morphology of fillers, and chemical bonding across filler/polymer interfaces have significant influence on electrical/thermal conductivity of polymer composite. Therefore, the research also pays substantial attention to these issues. First, electrical resistivity of CPCs is highly sensitive on volume or weight ratio (filler loading) of conductive fillers in polymer matrix, especially when filler loading is close to percolation threshold (pc). Thermal oxidation aging usually can cause a significant weight loss of polymer matrix in a CPC system, resulting in a filler loading change which can be exhibited by a prompt alteration in electrical resistivity of CPCs. Here, the phenomena are applied as approach for in-situ monitoring thermal oxidation status of polymeric materials is developed based on an electrical sensors based on conductive polymeric composites (CPCs). The study developed a model for electrical resistivity of sensors from the CPCs as a function of aging time at constant aging temperature, which is in a good agreement with a Boltzmann-Sigmoidal equation. Based on the finding, the sensors show their capability of in-situ in-situ monitor and estimate aging status of polymeric components by a fast and convenient electrical resistance measurement.
Second, interfacial issues related to these thermal conductive fillers are systemically studied. On the one hand, the study focuses on relationship between morphology of h-BN particles and thermal conductivity of their epoxy composites. It is found that spherical-agglomeration of h-BN particles can significantly enhance thermal conductivity of epoxy resin, compared with dispersed h-BN plates, by substantially reducing specific interfacial area between h-BN and epoxy resin. On the other hand, surface of high thermal conductive fillers such as SiC particles and MWNTs are successfully functionalized, which makes their surface reactive with bisphenol A diglycidyl ether and able to form chemical bonding between fillers and epoxy resin. By this means, thermal conductivity of polymer composites is found to be significantly enhanced compared with control samples, indicating the interfacial chemical bonding across interface between thermal conductive fillers and polymer matrix can promote heat dissipation in polymeric composites. The finding can benefit a development of high thermal conductive polymer composites by interfacial chemical bonding enhancement to meet the demanding requirements in current fine pitch and Cu/low k technology.
22
Liu, Mingyang. "Improved durability and thermal stability of glass fiber reinforced composites using clay-polymer nanocomposites /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20LIU.
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Chan, Hong Yu. "Crystallization of polypropylene/vermiculite and polyethylene/vermiculite nanocomposites." access abstract and table of contents access full-text, 2004. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21173990a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2004.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
24
Xue, Siqi. "Organic-modifier-free pathways for the preparation of polymer-metal oxide nanocomposites." Diss., Connect to online resource - MSU authorized users, 2007.
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25
Kim, Il Tae. "Carbon-based magnetic nanohybrid materials for polymer composites and electrochemical energy storage and conversion." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45876.
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The role of nanohybrid materials in the fields of polymer composites and electrochemical energy systems is significant since they affect the enhanced physical properties and improved electrochemical performance, respectively. As basic nanomaterials, carbon nanotubes and graphene were utilized due to their outstanding physical properties. With these materials, hybrid nanostructures were generated through a novel synthesis method, modified sol-gel process; namely, carbon nanotubes (CNTs)-maghemite and reduced graphene oxide (rGO)-maghemite nanohybrid materials were developed. In the study on polymer composities, developed CNTs-maghemite (magnetic carbon nanotbues (m-CNTs)) were readily aligned under an externally applied magnetic field, and due to the aligned features of m-CNTs in polymer matrices, it showed much enhanced anisotropic electrical and mechanical properties. In the study on electrochemical energy system (Li-ion batteries), rGO-maghemite were used as anode materials; as a result, they showed improved electrochemical performance for Li-ion batteries due to their specific morphology and characteristics.
26
Olea, Mejia Oscar Fernando. "Micro and nano composites composed of a polymer matrix and a metal disperse phase." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5135/.
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Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10 %. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of the composites were also determined. Static and dynamic friction was measured. The scratch resistance of the specimens was determined. A study of the wear mechanisms in the samples was performed. The Al micro- and nanoparticles as well as Ni microparticles are well dispersed throughout the material while Ag micro and nanoparticles tend to form agglomerates. Generally the presence of microcomposites affects negatively the mechanical properties. For the nanoparticles, composites with a higher elastic modulus than that of the neat materials are achievable. For both micro- and nanocomposites it is feasible to lower the friction values with respective to the neat polymers. The addition of metal particles to polymers also improves the scratch resistance of the composites, particularly so for microcomposites. The inclusion of Ag and Ni particles causes an increase in the wear loss volume while Al can reduce the wear for both polymeric matrices.
27
Hossain, Delwar. "Endohedral and exohedral complexes of polyhedral oligomeric silsesquioxanes (POSS) endohedral clusters of Si₁₂ : a theoretical study /." Diss., Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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Mbanjwa, Khangelani Methuli. "A study of the morphology-property relationships of polymer-layered silicate nanocomposites." Thesis, Cape Peninsula University of Technology, 2007. http://hdl.handle.net/20.500.11838/2615.
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Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2007.<br>The continuous development of new materials and the improvement of existing ones ensure a
balance between technological growth and environmental sustainability. With the above
trade-offs, the quality of life for humankind is continually being improved. Polymeric
materials are some of our most valued commodities in our everyday lives. They continue to be
developed and improved in a variety of ways; one of which is to improve their properties by
preparing nanocomposites. Polymer-based nanocomposites (PNCs) is a way of getting novel
properties and enhancing existing one in polymer matrices, by incorporating additives on a
nano-scale. The most significant advantage of PNCs is the potential to design and tailor
properties for a specific application, since the control of the structure can be done at the
molecular level. Therefore, a fundamental understanding of the relationships between the
structure and the properties of PNCs is of utmost importance. Amongst the most studied and
researched PNC materials, polymer-layered silicate nanocomposites (PLSNs) have recently
enjoyed attention from academia and industry.
In the current study structure-property relationships of PLSNs were investigated. Polystyrene
(PS) was chosen as the base polymer due to its wide use in many articles such as in
packaging. It was also a material of choice based on its poor mechanical properties in its
natural state (unfilled), so as to contribute in its property improvement. Montmorillonite
(MMT) was a layered silicate (clay) of choice, as much research has been done on it, and it is
available worldwide, as a main component in Bentonite (a natural material).
Clays are composed of sheet-like, layered particles, which, when in a suitable environment,
can delaminate into single, nano-sized sheets. The sheets are held together by van der Waals
forces and between the sheets are exchangeable cations. The clays are hydrophilic in nature
and cannot readily delaminate in a hydrophobic polymer matrix due to the differences in
surface energies. A MMT surface was functionalized to be hydrophobic by conducting an ion
exchange reaction with alkyl ammonium surface active agents (surfactants). Polymerizable
surfactants (surfmers) were used to enhance the interfacial interaction between the PS matrix
and MMT silicate layers. The organically modified clays (organoclays) were used in synthesizing polystyrene-layered
silicate nanocomposites (PS-LSN) by an in-situ intercalative polymerization method. The
polymerization of the nanocomposites was conducted in bulk. The morphologies of the
nanocomposites were characterized using small-angle X-ray scattering (SAXS), transmission
electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and gel
permeation chromatography (Ope).
The study was further expanded to the investigation of the effects of the nanocomposite
structure, type of organic modifier, and amount of clay loading on the properties of the
materials. The properties were studied by dynamic mechanical analysis (DMA),
thermomechanical analysis (TMA) and dielectric analysis (DEA). The properties were
dependent on the interfacial processes between the clay layers and the polymer matrix. The
changes in properties compared to the PS homopolymer showed time and temperature
dependent effects, as determined by DEA. Even though the dynamics of the interfacial
interactions are still not fully understood, the nanocomposites showed improvements in
properties compared to the homopolymers.
29
Tong, Zhaohui. "Water-based suspension of polymer nanoclay composite prepared via miniemulsion polymerization." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19763.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Yulin Deng; Committee Member: Howard (Jeff) L. Empie; Committee Member: J. Carson Meredith; Committee Member: Jeffery S. Hsieh; Committee Member: Timothy Patterson.
30
Zhang, Xiefei. "Studies on Single Wall Carbon Nanotube and Polymer Composite Films and Fibers." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7610.
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Single wall carbon nanotubes (SWNT) have been extensively studied over the last decade due to their excellent comprehensive properties for a variety of applications. This study is focused on the applications of SWNTs as reinforcement for polymer matrices. Due to van der Waal interactions, SWNTs form bundles of about 30 nm diameters. In order to take full advantage of the SWNT mechanical properties, SWNT must exfoliate or at least disperse in small diameter bundle size. Optical microscopy and SEM only give qualitative information of dispersion. Quantitative characterization through TEM or AFM can be time consuming in order to get statistical result. In this study, simple method is developed to quantitatively estimate the size of SWNT bundle in dispersion based on the geometry controlled electrical percolation behavior. The SWNTs can be dispersed /exfoliated via PVP wrapped SWNT aqueous dispersion assisted by surfactants such as sodium dodycel sulfate. PVA / SWNT composite films prepared through PVP wrapped SWNTs exhibit improved mechanical properties as well as the evidence of load transfer from the polymer matrix to the SWNT as monitored by the Raman spectroscopy. SWNT can also be well dispersed into PVA/DMSO/H2O solution. Gel spinning of PVA/SWNT composite fiber has been successfully carried out with improved mechanical properties. Functionalized tubes can be used to enhance SWNT dispersion and exfoliation. Oxidation in strong acids is one method used for functionalizing nanotubes. SWNTs have been functionalized in nitric acid. The structure and properties of films (buckypaper) processed from nitric acid functionalized tubes have been studied exhibiting high tensile strength and high electrical conductivity. Nitric acid treatment results in selective degradation of the small diameter tubes.
31
Milliren, Eric Carlton. "Nanocomposites a study of theoretical micromechanical behavior using finite element analysis /." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/milliren/MillirenE0509.pdf.
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Current research in nanotechnology has produced an increasing number of possibilities for advanced materials. Among those materials with potential advanced mechanical properties are fiber-reinforced composite laminates that utilize nanoscale fiber diameters. Through a combination of studying classic micromechanical models and modern computer-aided finite element analysis (FEA), the advantages for utilizing these nanofibers in advanced structural applications, such as space mirror backings, was investigated. The approach for modeling these composite structures was that of a Representative Volume Element (RVE). Using the program ABAQUS/CAE, a RVE was created with the goals of accurately comparing to the shear lag theory, effectively incorporating "interphase" zones that bond the constituents, and demonstrating effects of down-scaling fiber diameter. In this thesis, the progression of the ABAQUS model is thoroughly covered as it developed into a verified model correlating with the shear lag theory. The model produced was capable of utilizing interphase if desired, and was capable of off-axis loading scenarios. A MathCAD program was written in order to employ the published theoretical techniques, which were then compared to the FEA results for verification. The FEA model was found to work well in conjunction with the theory explored using MathCAD, after which the nanofiber FEA model showed some clear advantages over a conventional-sized model, specifically an increase in strength of the composite RVE. Finally, it was determined that the interfacial bonding strength plays a large role in the structure of the interphase zone, and thus the overall strength of the composite.
32
Zhu, Honggang. "Development of epoxy-organoclay nanocomposite as high performance coating and as matrix material of durable GFRP composite for civil engineering applications /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202009%20ZHU.
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Sahu, Laxmi Kumari. "Bulk and Interfacial Effects on Density in Polymer Nanocomposites." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3619/.
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The barrier properties of polymers are a significant factor in determining the shelf or device lifetime in polymer packaging. Nanocomposites developed from the dispersion of nanometer thick platelets into a host polymer matrix have shown much promise. The magnitude of the benefit on permeability has been different depending on the polymer investigated or the degree of dispersion of the platelet in the polymer. In this dissertation, the effect of density changes in the bulk and at the polymer-platelet interface on permeability of polymer nanocomposites is investigated. Nanocomposites of nylon, PET, and PEN were processed by extrusion. Montmorillonite layered silicate (MLS) in a range of concentrations from 1 to 5% was blended with all three resins. Dispersion of the MLS in the matrix was investigated by using one or a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Variation in bulk density via crystallization was analyzed using differential scanning calorimetry (DSC) and polarized optical microscopy. Interfacial densification was investigated using force modulation atomic force microscopy (AFM) and ellipsometry. Mechanical properties are reported. Permeability of all films was measured in an in-house built permeability measurement system. The effect of polymer orientation and induced defects on permeability was investigated using biaxially stretched, small and large cycle fatigue samples of PET and nylon nanocomposites. The effect of annealing in nylon and nanocomposites was also investigated. The measured permeability was compared to predicted permeability by considering the MLS as an ideal dispersion and the matrix as a system with concentration dependent crystallinity.
34
Foston, Marcus Bernard. "Cyclic, tethered and nanoparticulate silicones for material modification." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24762.
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Thesis (Ph.D.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Dr. Haskell W. Beckham; Committee Member: Dr. Anselm Griffin; Committee Member: Dr. Johannes Leisen; Committee Member: Dr. Sankar Nair; Committee Member: Dr. Uwe Bunz.
35
Dasari, Aravind. "On toughening and wear/scratch damage in polymer nanocomposites." University of Sydney, 2007. http://hdl.handle.net/2123/1911.
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Doctor of Philosophy<br>The drastic improvements in stiffness and strength even with the addition of small percentage of clay to a polymer are commonly traded-off with significant reductions in fracture toughness. It is believed that the presence of a stiff nano-filler will restrict the mobility of the surrounding matrix chains, and thus limit its ability to undergo plastic deformation, thereby decreasing their fracture toughness. To understand the role of rigid nano-fillers, like clay and their constraint effect on the surrounding polymer matrix, the effects of preferentially organized polyamide 6 lamellae in the vicinity of organoclay layers on the toughening processes are studied and compared with polyamide 6 filled with an elastomeric additive (POE-g-MA). It is suggested that to impart high toughness to polymer/organoclay nanocomposites, full debonding at the polymer-organoclay interface is necessary so that shear yielding of large volumes of matrix material can be enhanced. However, due to the strong tethering junctions between the individual organoclay layers and the matrix, full-scale debonding at the polymer-organoclay interface is rarely observed under stress conditions indicating that the constraint on the polymer adjacent to the clay is not relieved. Therefore, this has led to the development of ternary nanocomposites by adding a soft elastomeric dispersed phase to polymer/clay systems to obtain well-balanced mechanical properties. Polyamide 66/SEBS-g-MA/organoclay nanocomposites are prepared with four different blending protocols to understand the effect of blending protocol on the microstructure, mechanical properties and fracture mechanisms of the ternary nanocomposites so as to obtain new insights for producing better toughened polymer nanocomposites. In general, it is found that the level of enhancement of fracture toughness of ternary nanocomposites depends on: (i) the location and extent of dispersion of organoclay and (ii) the internal cavitation of rubber particles leading to effective relief of crack-tip tri-axial constraint and thus activating the matrix plastic deformation. Based on the wear/scratch damage studies on different polymer nanocomposite systems, it is suggested that elastic modulus and toughness of polymer nanocomposites are not the predominant factors controlling the material removal or friction coefficient and cannot be the sole indicators to compare and rank candidate materials. It is also found that nano-fillers by themselves, even if uniformly dispersed with good interfacial interaction with the matrix, do not irrevocably improve the wear (and friction) properties. Although it is important to consider these factors, it is necessary to thoroughly understand all microstructural parameters and their response to wear/scratch damage. Other important factors that should be considered are the formation of a uniform and stable transfer film on the counterface slider and the role of excessive organic surfactants or other modifiers added to disperse nanoparticles in a polymer matrix. It is also emphasized that the mechanisms of removal of materials during the wearing/scratching process should be studied meticulously with the use of high resolution microscopic and other analytical tools as this knowledge is critical to understand the surface integrity of polymer nanocomposites.
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Samakande, Austin. "Use of the RAFT technique as an efficient method to synthesise well defined polymer-clay nanocomposites with improved properties." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1242.
Full textAbstract:
Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2009.<br>Synthesis and structural characterization of two novel cationic and three new neutral
reversible addition–fragmentation chain transfer (RAFT) agents is described. The
cationic RAFT agents bear a quaternary ammonium group: N,N-dimethyl-N-(4-
(((phenylcarbonothionyl)thio)methyl)benzyl)ethanammonium bromide (PCDBAB) and
N-(4-((((dodecylthio)carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium
bromide (DCTBAB). The three neutral RAFT agents synthesized are 1,4-
phenylenebis(methylene)dibenzene carbodithioate (PCDBDCP), didodecyl-1,4-
phenylenebis(methyllene)bistrithiocarbonate (DCTBTCD) and 11-(((benzylthio)carbonothioyl)
thio)undecanoic acid (BCTUA). The self-assembly behaviour in diluted
aqueous solutions of the cationic RAFT agents, PCDBAB and DCTBAB, is
described. The self-assembly behaviour was promoted by the presence of the thiocarbonyl-
thio group on the RAFT agents, in addition to the overall chemical structure
of the surfactant that also influence self-assembly.
The RAFT agents were used for the bulk or miniemulsion RAFT-mediated controlled
free-radical polymerization in the presence of clay to yield polymer–clay
nanocomposites (PCNs). Bulk polymerization resulted in PCNs with better control of
molar mass and polydispersity index (PDI) values when compared to PCNs prepared
by miniemulsion polymerization. In both bulk and miniemulsion polymerizations the
molar masses and PDI values were dependent on the amount of clay and RAFT
agent present in the system.
Free-radical bulk neutral RAFT agent-mediated polymerization resulted in PCNs with
predominantly intercalated morphology. This was attributed to radical–radical
coupling of the initiator anchored onto the clay galleries on which polymerization took
place. On the other hand, when the cationic RAFT agent anchored onto clay, i.e.
RAFT-modified clay was used, bulk polymerization resulted in predominantly exfoliated PCNs. However, miniemulsion polymerization carried out in the presence
of the RAFT-modified clays resulted in PCNs with a morphology that ranged from
partially exfoliated to intercalated morphology, as the clay loading was increased.
The changing morphology for miniemulsion-based PCNs was attributed to the
decreasing molar mass as the clay loading was increased.
The PCNs obtained had enhanced thermo-mechanical properties as a result of the
presence of clay. The thermo-mechanical properties depended on the molar mass,
PDI, clay loading, and the morphology of the PCNs.
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Kim, Sung-gi. "PET Nanocomposites Development with Nanoscale Materials." Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1178043237.
Full textAbstract:
Dissertation (Ph.D.)--University of Toledo, 2007.<br>Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy Degree in Engineering." Bibliography: leaves 200-205.
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Upadhyay, Prabhat Kumar. "Design, Synthesis, and Characterization of Aqueous Polymeric Hybrid Composites and Nanomaterials of Platinum(II) and Gold(I) Phosphorescent Complexes for Sensing and Biomedical Applications." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822788/.
Full textAbstract:
The two major topics studied in this dissertation are the gold(I) pyrazolate trimer {[Au(3-R,5-R’)Pz]3} complexes in aqueous chitosan polymer and phosphorescent polymeric nanoparticles based on platinum(II) based complex. The first topic is the synthesis, characterization and optical sensing application of gold(I) pyrazolate trimer complexes within aqueous chitosan polymer. A gold(I) pyrazolate trimer complex, {[Au(3-CH3,5-COOH)Pz]3}, shows high sensitivity and selectivity for silver ions in aqueous media, is discussed for optical sensing and solution-processed organic light emitting diodes (OLEDs) applications. Gold(I) pyrazolate trimer complexes are bright red emissive in polymeric solution and their emission color changes with respect to heavy metal ions, pH and dissolved carbon dioxide. These photophysical properties are very useful for designing the optical sensors. The phosphorescent polymeric nanoparticles are prepared with Pt-POP complex and polyacrylonitrile polymer. These particles show excellent photophysical properties and stable up to >3 years at room temperature. Such nanomaterials have potential applications in biomedical and polymeric OLEDs. The phosphorescent hybrid composites are also prepared with Pt-POP and biocompatible polymers, such as chitosan, poly-l-lysine, BSA, pnipam, and pdadmac. Photoluminescent enhancement of Pt-POP with such polymers is also involved in this study. These hybrid composites are promising materials for biomedical applications such as protein labeling and bioimaging.
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Redondo, Foj María Belén. "A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/59457.
Full textAbstract:
[EN] The development of new and more complex polymeric materials involves challenging problems to basic sciences. The relationship between structure and molecular dynamics assumes great importance for the future development of novel technologies based on such polymers. Thus, the understanding of how small changes in the chemical structure affect the properties of the material is essential to progress in the technological and scientific area. An in-depth analysis of the molecular mobility leads to establish the structure-properties relationships. On this basis, the main aim of the present work is to study the molecular mobility of two different families of polymeric materials. For this purpose, the experimental techniques mainly used were Differential Scanning Calorimetry (DSC) and Dielectric Relaxation Spectroscopy (DRS).
The first family of polymers characterized was a series of chemically cross-linked copolymers composed by Vinylpyrrolidone (VP) and Butyl Acrylate (BA) monomers.
In the first place, the influence of the monomer molar ratio (XVP/YBA) on the copolymer properties was studied. Thus, a Fourier Transform Infrared Spectroscopy (FTIR) analysis verified dipole-dipole interactions between amide groups. The influence of these interactions on several parameters related to the molecular mobility was evidenced by the DSC, DRS and Dynamic Mechanical Analysis (DMA) techniques. Secondly, the effect of the cross-link density on the molecular dynamics of 60VP/40BA copolymers was analyzed using DSC and DRS. One single glass transition was detected by DSC measurements. The DRS analysis showed that an increase of the cross-linking produced a typical effect on the alpha process dynamics. However, the beta process, which possessed typical features of pure JG relaxation, unexpectedly lost the intermolecular character for the highest cross-linker content. The fastest gamma process was relatively unaffected.
The second family of polymeric materials studied was a series of segmented polycarbonatediol polyurethane (PUPH) modified with different amounts of expanded graphite (EG) conductive filler. Scanning Electron Microscopy (SEM), X-ray diffraction measurements and FTIR analysis demonstrated a homogeneous dispersion of the EG filler in the matrix. DRS was used to study the dielectric properties of the PUPH/EG composites. The dielectric permittivity of the composites showed an insulator to conductor percolation transition with the increase of the EG content (2030 wt%). The addition of expanded graphite to the matrix caused a dramatic increase in the electrical conductivity of ten orders of magnitude, which is an indication of percolative behavior.<br>[ES] El desarrollo de nuevos materiales poliméricos de mayor complejidad produce un desafío cada vez mayor en el área de las ciencias básicas. La relación entre la estructura y la dinámica molecular resulta de gran importancia para el desarrollo de nuevas tecnologías basadas en estos materiales poliméricos. Así, una mayor comprensión de cómo pequeños cambios en la estructura química afectan a las propiedades de los materiales resulta esencial para el progreso científico y tecnológico. Un análisis en profundidad de la movilidad molecular permite establecer las relaciones estructura-propiedades. Partiendo de esta base, el principal objetivo del presente trabajo es el estudio de la movilidad molecular de dos familias diferentes de materiales poliméricos. Para ello, las técnicas experimentales utilizadas fueron principalmente la Calorimetría Diferencial de Barrido (DSC) y la Espectroscopia de Relajación Dieléctrica (DRS).
La primera familia de polímeros caracterizada fue una serie de copolímeros entrecruzados químicamente compuestos por los monómeros Vinilpirrolidona (VP) y Acrilato de Butilo (BA).
En primer lugar, se estudió la influencia de la proporción molar de monómero (XVP/YBA) en las propiedades del copolímero. A través de un análisis por Espectroscopia de Infrarrojo por Transformada de Fourier (FTIR), se verificó la existencia de interacciones dipolo-dipolo entre los grupos amida. Mediante el análisis por DSC, DRS y Análisis Dinamomecánico (DMA), se evidenció la influencia de estas interacciones en diferentes parámetros relacionados con la movilidad molecular.
En segundo lugar, se analizó el efecto de la densidad de entrecruzamiento en la dinámica molecular de los copolímeros 60VP/40BA usando DSC y DRS. A través de las medidas de DSC se observó una única transición vítrea para todos los entrecruzamientos. El análisis por DRS mostró como el incremento en entrecruzante produjo el típico efecto en la dinámica del proceso alpha, pero sin embargo, el proceso beta, que tenía las características típicas de una relajación JG, perdió de forma inesperada su carácter intermolecular para el mayor contenido en entrecruzante. El proceso gamma no se vio afectado.
La segunda familia de materiales poliméricos estudiada fue una serie de poliuretanos segmentados (PUPH) modificados con diferentes cantidades de grafito expandido (EG), utilizado como relleno conductivo (desde 0 a 50% en peso). El análisis de los resultados obtenidos mediante Microscopía Electrónica de Barrido (SEM), Difracción de Rayos X y FTIR demostró la homogénea dispersión del relleno de EG en la matriz de PUPH. La técnica DRS se usó para estudiar las propiedades dieléctricas de los materiales compuestos PUPH/EG. La permitividad dieléctrica de los materiales mostró una transición de percolación desde aislante a conductor al incrementarse el contenido en EG (rango de 20-30% en peso). La adición de grafito expandido a la matriz de PUPH causó un incremento significativo en la conductividad dieléctrica de diez órdenes de magnitud, lo que indica el comportamiento de percolación.<br>[CAT] El desenvolupament de nous materials polimèrics de major complexitat produeix un desafiament cada vegada major en l'àrea de les ciències bàsiques. La relació entre l'estructura i la dinàmica molecular resulta de gran importància per al desenrotllament de noves tecnologies basades en aquests materials polimèrics. Així, una major comprensió de com petits canvis en l'estructura química afecten a les propietats dels materials, resulta essencial per al progrés científic i tecnològic. Un anàlisis en profunditat de la mobilitat molecular permet establir les relacions estructura-propietats. Partint d'aquesta base, el principal objectiu del present treball és l'estudi de la mobilitat molecular de dues famílies diferents de materials polimèrics. Per a això, les tècniques experimentals utilitzades van ser principalment la Calorimetria Diferencial de Rastreig (DSC) i l'Espectroscòpia de Relaxació Dielèctrica (DRS).
La primera família de polímers caracteritzada va ser una sèrie de copolímers entrecreuats químicament compostos pels monòmers Vinilpirrolidona (VP) i Acrilat de Butilo (BA) .
En primer lloc, es va estudiar la influència de la proporció molar de monòmer (XVP/YBA) en les propietats del copolímer. A través d'una anàlisi per Espectroscòpia d'Infraroig per Transformada de Fourier (FTIR), es va verificar l'existència d'interaccions dipol-dipol entre els grups amida. Mitjançant l'anàlisi per DSC, DRS i Anàlisi Dinamomecánico (DMA), es va evidenciar la influència d'aquestes interaccions en diferents paràmetres relacionats amb la mobilitat molecular.
En segon lloc, es va analitzar l'efecte de la densitat d'entrecreuament en la dinàmica molecular dels copolímers 60VP/40BA mitjançant DSC i DRS. A través de les mesures de DSC es va observar una única transició vítria per a tots els continguts d'agent entrecreuant . L'anàlisi per DRS va mostrar com l'increment en agent entrecreuant va produir l'efecte esperat en la dinàmica del procés alfa. En canvi, el procés beta, que tenia les característiques típiques d'una relaxació JG, va perdre de forma inesperada el seu caràcter intermolecular per al major contingut en agent entrecreuant. El procés més ràpid gamma no es va veure afectat.
La segona família de materials polimèrics estudiada va ser una sèrie de poliuretans segmentats (PUPH) modificats amb diferents quantitats de grafit expandit (EG) , utilitzat com a farcit conductiu (des de 0 a 50% en pes). L'anàlisi dels resultats obtinguts per mitjà de Microscòpia Electrònica de Rastreig (SEM), Difracció de Rajos X i FTIR va mostrar la dispersió homogènia del EG en la matriu de PUPH. La tècnica DRS es va utilitzar per a estudiar les propietats dielèctriques dels materials compostos PUPH/EG. La permitivitat dielèctrica dels materials va mostrar una transició de percolació des d'aïllant a conductor amb l'increment de contingut en EG (20-30% en pes). L'addició d'EG a la matriu de PUPH va causar un increment significatiu en la conductivitat dielèctrica, de deu ordes de magnitud.<br>Redondo Foj, MB. (2015). A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59457<br>TESIS
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Gurun, Bilge. "Deformation studies of polymers and polymer/clay nanocomposites." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37118.
Full textAbstract:
Polymer clay nanocomposites have been a popular area of materials research since they were first introduced in the 1990s. The inclusion of clays into many different host polymers has been shown to improve the properties of matrix polymers in a number of ways including increased mechanical strength, thermal stability and improved barrier properties while keeping the composite light weight and transparent. Although there is a great deal of published work on the preparation and property measurements of polymer clay nanocomposites, there is no model to design a nanocomposite with a given set of properties for a specific end-use. While it is important to know the structure property relationships of materials, the understanding of how nanocomposites reach their final forms and properties is equally important. A thorough understanding of processing effects on the final structure of polymer clay nanocomposites is still missing. With this perspective, this thesis addresses building structure-processing relationships of polymer clay nanocomposites by analyzing multiaxial deformation behavior using in-situ x-ray scattering techniques.
This thesis can be divided into two distinct parts. The first part concerns the design of the in-situ multiaxial deformation device (IMDD) used to create the deformation conditions that polymers go through during processing such as blow molding and thermoforming. The device was designed to overcome several concerns with in situ measurement by maintaining constant sample to detector distance, minimizing the material between the incident beam and the detectors, as well as exposing the same point on the sample throughout deformation. A new design to create biaxial deformation, termed in-situ biaxial deformation device (IBDD), is also introduced in this part of the thesis.. In addition, a new heating unit, attached to IBDD, is designed for higher temperature studies, up to 150°C, to imitate industrial processing conditions more closely.
The second part of the thesis addresses the effect of strain, strain rate, and temperature as well as the amount of clay on the polymer morphology evolution during multiaxial deformation.. Two different polymer/clay systems were studied: poly(ethylene)/clay and poly(propylene)/clay. It was observed that the morphological evolution of polyethylene and polypropylene is affected by the existence of clay platelets as well as the deformation temperature and the strain rate. Martensitic transformation of orthorhombic polyethylene crystals into monoclinic crystal form was observed under strain but is hindered in the presence of clay nanoplatelets. The morphology evolution of poly(propylene) crystal structure during multiaxial deformation was more subtle where the most stable α-crystalline form went through strain induced melting. This was more noticeable in the nanocomposites with clays up to 5 wt%.
It was also noted that the thickness of the interlamellar amorphous region increased with increasing strain at room temperature due to the elongation of the amorphous chains. The increase in the amorphous layer thickness is slightly higher for the poly(ethylene)/clay nanocomposites compared to neat poly(ethylene) while the increase in the lamellar long spacing is slightly higher for the neat poly(propylene) compared to poly(propylene)/clay nanocomposites. The rate of change in the characteristic repeat distance in both poly(ethylene) and poly(propylene) systems is higher at faster strain rates, at room temperature, where it remained constant during higher temperature deformations.
Time dependent recovery after deformation studies have shown that poly(ethylene)/clay system reverts back to its initial configuration. The recovery in the amorphous chains was however observed to take longer in the clay added poly(ethylene)s. Crystalline relaxation was observed to happen almost instantly in the poly(ethylene)/clay system. On the other hand, amorphous chains in the poly(propylene)/clay system did not revert back to the initial configuration in the period of time that the recovery observations were performed while the crystalline configuration recovered back almost fully in the given time.
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Xu, Jianwen. "Dielectric Nanocomposites for High Performance Embedded Capacitors in Organic Printed Circuit Boards." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11525.
Full textAbstract:
Conventionally discrete passive components like capacitors, resistors, and inductors are surface-mounted on top of the printed circuit boards (PCBs). To match the ever increasing demands of miniaturization, cost reduction, and high performance in microelectronic industry, a promising approach is to integrate passive components into the board during PCB manufacture. Because they are embedded inside multilayer PCBs, such components are called embedded passives.
This work focuses on the materials design, development and processing of polymer-based dielectric nanocomposites for embedded capacitor applications. The methodology of this approach is to combine the advantages of the polymer and the filler to satisfy the electric, dielectric, mechanical, fabrication, and reliability requirements for embedded capacitors. Restrained by poor adhesion and poor thermal stress reliability at high filler loadings, currently polymer-ceramic composites can only achieve a dielectric constant of less than 50. In order to increase the dielectric constant to above 50, effects of high-k polymer matrix, bimodal fillers, and dispersing agent are systematically investigated. Surface functionalization of nanofiller particles and modification of epoxy matrix with a secondary rubberized epoxy to form sea-island structure are proposed to enhance the dielectric constant, adhesion and high-temperature thermal stress reliability of high-k composites. To obtain photodefinable high-k composites, fundamental understanding of the photopolymerization of the novel epoxy-ceramic composite photoresist is addressed. While the properties of high-k composites largely depend on the polymer matrix, the fillers can also drastically affect the material properties. Carbon black- and carbon nanotubes-filled ultrahigh-k polymer composites are investigated as the candidate materials for embedded capacitors. Dielectric composites based on percolation typically show a high dielectric constant, and a high dielectric loss which is not desirable for high frequency applications. To achieve a reproducible low-loss percolative composite, a novel low-cost core-shell particle filled high-k percolative composite is developed. The nanoscale insulating shells allow the electrons in the metallic core to tunnel through it, and thereby the composites exhibit a high dielectric constant as a percolation system; on the other hand, the insulating oxide layer restricts the electron transfer between filler particles, thus leading to a low loss as in a polymer-ceramic system.
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Cho, Hosouk. "Chemical incorporation of polyhedral oligomeric silsesquioxane into thermoset matrices." Diss., Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
Full text
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Etmimi, Hussein Mohamed. "New approaches to the synthesis and exfoliation of polymer/functional graphene nanocomposites by miniemulsion polymerization." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20119.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: New methods are described for the synthesis of polymer/graphite nanocomposites using the
miniemulsion polymerization process. Natural graphite was functionalized by oxidation to
produce graphite oxide (GO) nanosheets. Poly(styrene-co-butyl acrylate) (poly(St-co-BA))
nanocomposite latices containing GO nanosheets were successfully synthesized using
miniemulsion as a one-step nano-incorporation technique. The approach followed included
expanding the GO nanosheets in situ during the miniemulsification step and then
polymerizing the monomers in the presence of these expanded nanosheets. Styrene (St) and
butyl acrylate (BA) were mixed with GO and then emulsified in the presence of a surfactant
and a hydrophobe to afford pre-miniemulsion latex particles. The stable pre-miniemulsions
were then polymerized to yield poly(St-co-BA)/GO nanocomposite latices. The
polymerization proceeded with relatively high monomer conversion and produced stable
nanocomposite latex particles. The nanocomposites exhibited mainly an intercalated
morphology, irrespective of the percentage of GO filler loading.
The synthesis of exfoliated polymer nanocomposites made with modified GO is described.
GO was modified with a surfmer (reactive surfactant), 2-acrylamido-2-methyl-1-propane
sulfonic acid (AMPS), which widened the gap between the GO nanosheets and facilitated
monomer intercalation between its nanogalleries. The AMPS-modified GO was used for the
synthesis of poly(St-co-BA)/GO nanocomposite latices using a similar miniemulsion
procedure. The obtained nanocomposites had exfoliated morphologies and the GO nanosheets
were largely exfoliated (about 2–5 nm thick) in the resultant films obtained from the
synthesized nanocomposite latices. The synthesized nanocomposites had enhanced thermal
and mechanical properties compared to pure polymer as a result of the presence of AMPSmodified
GO. Furthermore, the nanocomposites made with AMPS-modified GO had better
thermal and mechanical properties than the unmodified GO. The mechanical properties of the
nanocomposites depended on the AMPS-modified GO loading in the nanocomposites.
The synthesis of polystyrene/GO (PS-GO) nanocomposites using the reversible additionfragmentation
chain transfer (RAFT) mediated polymerization method is also described. The
GO was synthesized and immobilized with a RAFT agent to afford RAFT-functionalized GO
nanosheets. The RAFT-immobilized GO was used for the synthesis of PS nanocomposites in
a controlled manner using miniemulsion polymerization. The molar mass and dispersity of the
PS in the nanocomposites depended on the amount of RAFT-grafted GO in the system, in
accordance with the features of the RAFT-mediated polymerization. X-ray diffraction and transmission electron microscopy analyses revealed that the nanocomposites had exfoliated
morphology, even at relatively high GO content. The thermal stability and mechanical
properties of the PS-GO nanocomposites were better than those of the neat PS polymer.
Furthermore, the mechanical properties were dependent on the modified-GO content (i.e., the
amount of RAFT-grafted GO).
The hydrophobicity and barrier properties of the resulting films prepared from the synthesized
poly(St-co-BA)/GO nanocomposite latices to water and water vapor were also investigated.
The hydrophobicity of the synthesized nanocomposite films was determined using contact
angle measurements. The water permeability was determined by measuring the moisture
vapor transmission rate of the films. The GO in the nanocomposites was reduced to its
original form (i.e., graphite), and the barrier properties of the obtained nanocomposite films
were determined and compared to films containing the unmodified GO (as-prepared GO).
Results showed that reduction of GO had a significant impact on the water affinity of the
resultant films prepared from the synthesized nanocomposite latices. The presence of
reduced-GO (RGO) instead of unmodified GO in the miniemulsion formulation significantly
improved the hydrophobicity and barrier properties of the final films to water. However, the
barrier properties of the nanocomposites were unaffected by the amount of RGO in the
nanocomposites.<br>AFRIKAANSE OPSOMMING: Nuwe metodes is beskryf vir die sintese van polimeer/grafiet nanosamestellings deur gebruik
te maak van die miniemulsie polimerisasieproses. Natuurlike grafiet is gefunksionaliseer dmv
oksidasie om grafietoksied (GO) nanovelle te vorm. Polistireen-ko-butielakrilaat (poli[St-ko-
BA]) nanosamestellinglatekse wat GO nanovelle bevat is suksesvol gesintetiseer deur gebruik
te maak van miniemulsie polimerisasie as ‘n een-stap nano-insluitingstegniek. Die benadering
wat gevolg is het die uitbreiding van die GO nanovelle, in situ, gedurende die
miniemulsifiseringstap behels, gevolg deur die polimerisasie van die monomere in die
teenwoordigheid van hierdie uitgebreide nanovelle. Stireen (St) en butielakrilaat (BA) is met
GO gemeng en daarna emulgeer in die teenwoordigheid van ‘n seepmiddel (surfactant) en ‘n
hidrofoob om pre-miniemulsielateksdeeltjies te lewer. Die stabiele pre-miniemulsies is
gepolimeriseer om poli(St-ko-BA)/GO nanosamestellinglatekse te vorm. Die polimerisasie
het met redelike hoë monomeeromskakeling verloop en het stabiele
nanosamestellinglateksdeeltjies gelewer. Hierdie nanosamestellings het hoofsaaklik
geïnterkaleerde morfologie, onafhanklik van die persentasie GO vullers, getoon.
Die sintese van afgeskilferde polimeernanosamestellings berei met gewysigde GO is beskryf.
GO is gewysig met ‘n ‘surfmer’ (reaktiewe seepmiddel), 2-akrielamido-2-metiel-1-
propaansulfoonsuur (AMPS), wat die gapings tussen die GO nanovelle vergroot het en die
monomeer interkalering tusssen sy nanogange fasiliteer. Die AMPS-gewysigde GO is gebruik
vir die sintese van poli(St-ko-BA)/GO nanosamestellinglatekse deur gebruik te maak van ‘n
soortgelyke miniemulsie prosedure. Die nanosamestelling sό verkry het ‘n afgeskilferde
morfologie getoon en die GO nanovelle was grootendeels afgeskilfer (ongeveer 2–5 nm dik)
in die films wat berei is van die gesintetiseerde nanosamestellinglatekse. Laasgenoemde het
verhoogde termiese en meganiese eienskappe gehad in vergelyking met die suiwer polimeer,
as gevolg van die teenwoordigheid van die AMPS-gewysigde-GO. Die meganiese eienskappe
van die nanosamestellings hang af van persentasie AMPS-gewysigde GO vullers in die
nanosamestellings.
Die sintese van PSt/GO nanosamestellings dmv die omkeerbare-addisie-fragmentasieoordrag-
(OAFO-, Eng. RAFT-) bemiddelde polimerisasie metode is ook beskryf. Die GO is
berei en geïmmobiliseer met ‘n RAFT verbinding om GO nanovelle met RAFT
funksionaliteit te lewer. Die RAFT-geïmmobiliseerde GO is gebruik vir die sintese van PSt
nanosamestellings in ‘n gekontrolleerde manier mbv miniemulsie polimerisasie. Die molêre massa en dispersie van die PSt in die nanosamestellings hang af van die hoeveelheid RAFTgeënte
GO in die sisteem, in ooreenstmming met die kenmerke van RAFT-bemiddelde
polimerisasie. X-straaldiffraksie en transmissie-elektronmikroskopie analises het bewys dat
die nanosamestellings, selfs by relatiewe hoë GO inhoud, ‘n afgeskilferde morfologie gehad
het. Die termiese stabiliteit en meganiese eienskappe van die PSt-GO nanosamestellings was
beter as dié van die suiwer PSt polimeer. Verder was die meganiese eienskappe afhanklik van
die gewysigde-GO-inhoud (dws, die hoeveelheid RAFT-geënte-GO).
Die hidrofobisiteit en spereienskappe van die films berei vanaf die gesintetiseerde poli(St-ko-
BA)/GO nanosamestellinglatekse teenoor water en waterdamp is ook ondersoek. Die
hidrofobisiteit is ondersoek deur gebruik te maak van kontakhoekmeting. Die
waterdeurlaatbaarheid is bepaal deur die waterdampoordragtempo van die films te bepaal. Die
GO in die nanosamestellings is gereduseer tot sy eenvoudigste vorm (grafiet) en die
spereienskappe van die nanosamestellingfilms is bepaal en vergelyk met die films wat die
ongewysigde GO bevat het. Resultate het getoon dat reduksie van GO ‘n groot invloed gehad
het op die wateraffiniteit van die films wat berei is vanaf die gesintetiseerde
nanosamestellinglatekse. Die teenwoordigheid van die gereduseerde-GO (RGO) in plaas van
die onveranderde GO in die miniemulsie formulasie het die hidrofobisiteit en spereienskappe
van die finale films, teenoor water, baie verbeter. Die spereienskappe van die
nanosamestellings is egter nie beïnvloed deur die hoeveelheid RGO in die nanosamestellings
nie.
44
Yoonessi, Mitra. "Experimental and modeling studies of clay/polydicyclopentadiene resin nanocomposites." Diss., Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-07122004-140754.
Full text
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Hernandez-Luna, Alejandro. "Structure property and deformation analysis of polypropylene montmorillonite nanocomposites." Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4213/.
Full textAbstract:
Nanocomposites with expandable smectites such as montmorillonite layered silicates (MLS) in polymer matrices have attracted extensive application interest. Numerous MLS concentrations have been used with no particular justification. Here, we investigate the effects of MLS dispersion within the matrix and on mechanical performance. The latter is resolved through a three-prong investigation on rate dependent tensile results, time dependent creep results and the influence of a sharp notch in polypropylene (PP) nanocomposites. A fixed concentration of maleated polypropylene (mPP) was utilized as a compatibilizer between the MLS and non-polar PP. Analysis of transmission electron micrographs and X-ray diffraction patterns on the surface and below the surface of our samples revealed a unique skin-core effect induced by the presence of clay. Differential scanning calorimetric and polarized optical microscopic examination of spherulites sizes showed changes in nucleation and growth resulting from both the maleated PP compatibilizer and the MLS. These structural changes resulted in a tough nanocomposite, a concept not reported before in the PP literature. Nonlinear creep analysis of the materials showed two concentrations 3 and 5 % wt of PP, which reduced the compliance in the base PP. The use of thermal wave imaging allowed the identification of ductile failure among materials, but more important, aided the mapping of the elastic and plastic contributions. These are essential concepts in fracture analysis.
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Huang, Gang. "CHARACTERIZATION AND PROPERTY STUDIES OF CYANATE ESTER/ORGANOCLAY NOCOMPOSITES." MSSTATE, 2006. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07072006-162122/.
Full textAbstract:
Five series of PT-30/organoclay (Cloisite 10A, Cloisite 30B, Nanomer I.28E, Nanomer I.30E and Nanomer I.44PA) composites were prepared and characterized. The dispersion of clay tactoids in PT-30 resin was studied by XRD and TEM. XRD analyses determined that the d-spacings of each nanoclays of these were expanded upon dispersing in the PT-30 matrix versus the as-received clay. TEM micrographs further demonstrated that the intercalation of clay layers by PT-30 occurred during the curing process. Histograms of clay tactoids distributions were generated based on the combination of XRD and TEM results. The glass transition temperatures (Tg) of selected PT-30/clay composites were measured by DSC and compared. Partial clay exfoliation with some resin intercalation was demonstrated. The average flexural strengths and flexural moduli of all composites were obtained using three-point bending tests.
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Zengeni, Eddson. "Highly filled water based polymer/clay hybrid latexes." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71613.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: The use of co-sonication (ad-miniemulsion) polymerisation for the preparation of highly filled polymer/clay hybrid latexes is described. Laponite (Lap) content levels in the range of 10–50 wt% were effectively encapsulated in both polystyrene (PS) and polystyrene-co-butyl acrylate nanoparticles (PSBA). The latex and film morphological features of these highly filled hybrid materials were evaluated using both transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). PS/Lap latexes exhibited mixed particle morphologies from armoured particles at low clay content (10 wt%) to encapsulated particles at high clay content (50 wt%). However, PSBA/Lap hybrid latexes exhibited predominantly crumpled particle morphologies through the clay content studied. The resultant polymer/clay nanocomposites (PCNs) of PS/Lap and PSBA/Lap exhibited either partially or fully exfoliated structures. It was found that generally these PCNs exhibited superior properties than the neat polymers except for thermal stability properties. As much as 5000% storage modulus improvement was observed for both PS/Lap and PSBA/Lap relative to the neat polymers. The Tg of PSBA/Lap showed a 14 ºC shift towards higher temperature. Rheology tests showed that the resultant PCNs exhibited solid-like viscoelastic behaviour. The encapsulation of montmorilonite clay (MMT) using the ad-miniemulsion procedure was found to be ineffective. The MMT platelets remained adhered onto the polymer particles surfaces. Ineffective encapsulation of MMT platelets was attributed to their dimensions which were either large or equal to those of the polymer particles. Despite the ineffective encapsulation, the MMT platelets were completely exfoliated within the final PCNs as shown by both SAXS and TEM.
Overall, the ad-miniemulsion was found to be an effective method for the preparation of highly filled water based polymer/clay hybrid latexes. However, the clay encapsulation in polymer particles and the extent of clay exfoliation were found to be dependent on clay dimensions relative to the polymer particles, monomer/clay compatibility and clay modifier reactivity. It was found that clay dimensions and use of clay modifier that improve monomer/clay compatibility enhances encapsulation. On the other hand, the modifier reactivity influenced the extent of clay exfoliation in the final PCN, irrespective of clay encapsulation in the polymer particles. These findings were based on comparative studies conducted on the use of Lap versus MMT and non-reactive modifier versus reactive modifier during ad-miniemulsion polymerisation.<br>AFRIKAANSE OPSOMMING: Die gebruik van mede-sonikasie (ad-miniemulsie) polimerisasie vir die voorbereiding van die hoogsgevulde polimeer/klei hibriedlatekse word beskryf. Laponiet (Lap) vlakke in hoeveelhede van 10-50 gew% is effektief ge-inkapsuleer in beide polistireen (PS) en polistireen-ko-butielakrilaat nanopartikels (PSBA). Die morfologiese eienskappe van die latekse en films van hierdie hoogsgevulde hibried materiale is geëvalueer deur beide transmissie-elektronmikroskopie (TEM) en klein-hoek X-straal-verstrooiing (SAXS). PS/Lap latekse het gemengde partikel morfologieë getoon, bv. vanaf gepantserde partikels by lae kleihoeveelhede (10 gew%) tot ge-inkapsuleerde partikels by hoë kleihoeveelhede (50 gew%). Daarteenoor het PSBA/Lap hibriedlatekse „n oorwegend verkreukelde partikelmorfologie getoon vir die reeks kleihoeveelhede wat bestudeer is. Die gevolglike polimeer/klei nanokomposiete (PKNs) van PS/Lap en PSBA/Lap het, óf gedeeltelike, óof ten volle geëksfolieerde strukture getoon. Oor die algemeen is bevind dat hierdie PKNs beter eienskappe as die suiwer polimere getoon het, behalwe vir die termiese stabiliteit eienskappe. Verbeteringe van soveel as 5000% in die stoormodulus is waargeneem vir beide PS/Lap en PSBA/Lap met betrekking tot die suiwer polimere. Die Tg van PSBA/Lap het „n 14°C verskuiwing na „n hoër temperatuur getoon. Reologiese toetse het getoon dat die gevolglike PKNs vastestofagtige visko-elastiese gedrag getoon het. Die inkapsulering van montmorilonietklei (MMT), deur middel van die ad-miniemulsieproses, was ondoeltreffend. Die MMT plaatjies het agtergebly op die oppervlaktes van die polimeerpartikel. Oneffektiewe inkapsulering van MMT plaatjies is toegeskryf aan hul grootte, wat óf groter, óf gelyk was aan dié van die polimeerpartikels. Ten spyte van die oneffektiewe inkapsulering was al die MMT plaatjies in die finale PKNs geëksfolieer soos deur beide SAXS en TEM aangedui.
Oor die algemeen is bevind dat ad-miniemulsie „n effektiewe metode is vir die voorbereiding van hoogsgevulde waterbasis polimeer/klei hibriedlatekse. Daar is egter bevind dat klei inkapsulering in polimeerpartikels asook die omvang van klei eksfoliëring, afhanklik is van die klei afmetings in verhouding tot die polimeerpartikels, monomeer/klei verenigbaarheid en die reaktiwiteit van die kleiwysiger. Daar is bevind dat die klei afmetings en die gebruik van „n kleiwysiger wat die monomeer/klei verenigbaarheid verbeter, inkapsulering bevorder. Aan die ander kant het die reaktiwiteit van die kleiwysiger die omvang van klei eksfoliëring in die finale PKNs beïnvloed, ongeag van klei inkapsulering in die polimeerpartikels. Hierdie bevindings is gebaseer op vergelykende studies van die gebruik van Lap teenoor MMT en nie-reaktiewe wysiger teenoor reaktiewe wysiger gedurende ad-miniemulsiepolimerisasie.
48
Wang, Qi. "Electrochemical synthesis of CeO2 and CeO2/montmorillonite nanocomposites." Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4378/.
Full textAbstract:
Nanocrystalline cerium oxide thin films on metal and semiconductor substrates have been fabricated with a novel electrodeposition approach - anodic oxidation. X-ray diffraction analysis indicated that as-produced cerium oxide films are characteristic face-centered cubic fluorite structure with 5 ~ 20 nm crystal sizes. X-ray photoelectron spectroscopy study probes the non-stoichiometry property of as-produced films. Raman spectroscopy and Scanning Electron Microscopy have been applied to analyze the films as well. Deposition mode, current density, reaction temperature and pH have also been investigated and the deposition condition has been optimized for preferred oriented film formation: galvanostatic deposition with current density of -0.06 mA/cm2, T > 50oC and 7 < pH < 10. Generally, potentiostatic deposition results in random structured cerium oxide films. Sintering of potentiostatic deposited cerium oxide films leads to crystal growth and reach nearly full density at 1100oC. It is demonstrated that in-air heating favors the 1:2 stoichiometry of CeO2. Nanocrystalline cerium oxide powders (4 ~ 10 nm) have been produced with anodic electrochemical synthesis. X-ray diffraction and Raman spectroscopy were employed to investigate lattice expansion phenomenon related to the nanoscale cerium oxide particles. The pH of reaction solution plays an important role in electrochemical synthesis of cerium oxide films and powder. Cyclic voltammetry and rotation disk electrode voltammetry have been used to study the reaction mechanisms. The results indicate that the film deposition and powder formation follow different reaction schemes. Ce(III)-L complexation is a reversible process, Ce3+ at medium basic pH region (7~10) is electrochemically oxidized to and then CeO2 film is deposited on the substrate. CE mechanism is suggested to be involved in the formation of films, free Ce3+ species is coordinated with OH- at high basic pH region (>10) to Ce2O3 immediately prior to electrochemically oxidation Ce2O3 to CeO2. CeO2 / montmorillonite nanocomposites were electrochemically produced. X-ray diffraction and Raman spectroscopy illustrate the retaining of FCC structure for cerium oxide. Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry of composites indicate the insertion of montmorillonite platelets into the structural matrix of cerium oxide. Sintering study of the nanocomposites demonstrates that low concentration of montmorillonite platelet coordination into cerium oxide matrix increases crystal growth rate whereas high concentration of montmoillonite in nanocomposites retards the increase of crystallite size during the densification process.
49
Chirowodza, Helen. "Polymer-clay nanocomposites prepared by RAFT-supported grafting." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71914.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: In materials chemistry, surface-initiated reversible deactivation radical polymerisation (SI-RDRP) has emerged as one of the most versatile routes to synthesising inorganic/organic hybrid materials consisting of well-defined polymers. The resultant materials often exhibit a remarkable improvement in bulk material properties even after the addition of very small amounts of inorganic modifiers like clay.
A novel cationic reversible addition–fragmentation chain transfer (RAFT) agent with the dual purpose of modifying the surface of Laponite clay and controlling the polymerisation of monomer therefrom, was designed and synthesised. Its efficiency to control the polymerisation of styrene was evaluated and confirmed through investigating the molar mass evolution and chain-end functionality.
The surface of Laponite clay was modified with the cationic chain transfer agent (CTA) via ion exchange and polymerisation performed in the presence of a free non-functionalised CTA. The addition of the non-functionalised CTA gave an evenly distributed CTA concentration and allowed the simultaneous growth of surface-attached and free polystyrene (PS). Further analysis of the free and grafted PS using analytical techniques developed and published during the course of this study, indicated that the free and grafted PS chains were undergoing different polymerisation mechanisms. For the second monomer system investigated n-butyl acrylate, it was apparent that the molar mass targeted and the monomer conversions attained had a significant influence on the simultaneous growth of the free and grafted polymer chains. Additional analysis of the grafted polymer chains indicated that secondary reactions dominated in the polymerisation of the surface-attached polymer chains.
A new approach to separating the inorganic/organic hybrid materials into their various components using asymmetrical flow field-flow fractionation (AF4) was described. The results obtained not only gave an indication of the success of the in situ polymerisation reaction, but also provided information on the morphology of the material.
Thermogravimetric analysis (TGA) was carried out on the polymer-clay nanocomposite samples. The results showed that by adding as little as 3 wt-% of clay to the polymer matrix, there was a remarkable improvement in the thermal stability.<br>AFRIKAANSE OPSOMMING: Oppervlakgeïnisieerde omkeerbare deaktiveringsradikaalpolimerisasie (SI-RDRP) is een van die veelsydigste roetes om anorganiese/organiese hibriedmateriale (wat bestaan uit goed-gedefinieerde polimere) te sintetiseer. Die produk toon dikwels ʼn merkwaardige verbetering in die makroskopiese eienskappe – selfs na die toevoeging van klein hoeveelhede anorganiese modifiseerders soos klei.
ʼn Nuwe kationiese omkeerbare addisie-fragmentasie kettingoordrag (RAFT) middel met die tweeledige doel om die modifisering van die oppervlak van Laponite klei en die beheer van die polimerisasie van die monomeer daarvan, is ontwerp en gesintetiseer. Die klei se doeltreffendheid om die polimerisasie van stireen te beheer is geëvalueer en bevestig deur die molêre massa en die funksionele groepe aan die einde van die ketting te ondersoek.
Die oppervlak van Laponite klei is gemodifiseer met die kationiese kettingoordragmiddel (CTA) deur middel van ioonuitruiling en polimerisasie wat uitgevoer word in die teenwoordigheid van ʼn vrye nie-gefunksionaliseerde CTA. Die toevoeging van die nie-gefunksionaliseerde CTA het ʼn eweredig-verspreide konsentrasie CTA teweeggebring en die gelyktydige groei van oppervlak-gebonde en vry polistireen (PS) toegelaat. Verdere ontleding van die vrye- en geënte PS met behulp van analitiese tegnieke wat ontwikkel en gepubliseer is gedurende die verloop van hierdie studie, het aangedui dat die vry- en geënte PS-kettings verskillende polimerisasiemeganismes ondergaan. n-Butielakrilaat is in die tweede monomeer-stelsel ondersoek en dit was duidelik dat die molêre massa wat geteiken is en die geënte polimeerkettings.
ʼn Nuwe benadering tot die skeiding van die anorganiese/organiese hibriedmateriale in hulle onderskeie komponente met behulp van asimmetriese vloeiveld-vloei fraksionering (AF4) is beskryf. Die resultate wat verkry is, het nie net 'n aanduiding gegee van die sukses van die in-situ polimerisasiereaksie nie, maar het ook inligting verskaf oor die morfologie van die materiaal. Termogravimetriese analise (TGA) is uitgevoer op die polimeer-klei nanosaamgestelde monsters. Die resultate het getoon dat daar 'n merkwaardige verbetering in die termiese stabiliteit was na die toevoeging van so min as 3 wt% klei by die polimeermatriks.
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Do, In-Hwan. "Metal decoration of exfoliated graphite nanoplatelets (xGnP) for fuel cell application." Diss., 2008.
Find full textAbstract:
Thesis (Ph. D.)--Michigan State University. Dept. of Chemical Engineering and Materials Science, 2008.<br>Title from PDF t.p. (viewed on July 23, 2009) Includes bibliographical references. Also issued in print.