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1
Al-Shahrani, Abdullah A. "Layered silicate nanocomposites." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492712.
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Over the past decade, nanomaterials have been the subject of enormous interest. Notable for their extremely small feature size, they have the potential for wide-ranging industrial applications. Using such materials combined with epoxy resin to synthesise nanocomposite is proposed to enhance the corrosion protection performance of the resin.
2
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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Becker, Lars-Ole 1973. "High performance epoxy-layered silicate nanocomposites." Monash University, School of Physics and Materials Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/5747.
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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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Lightwing, Andrew. "Catastrophic disruption of layered ice-silicate bodies." Thesis, University of Kent, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589961.
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Large icy Kuiper Belt Objects (KBOs) such as Pluto have observed densities on the order of 1.8 - 2.0 g cm-3. This indicates that they are made up of some combination of ice and silicate material; their size further implies that they will possess a differentiated structure with ice dominating towards the surface and silicate material dominating towards the core. A series of impact experiments using the University of Kent's light gas gun have been carried out in order to determine the impact strength of spherical layered ice-silicate targets that reflect the suspected structure of these bodies. Impacts are also carried out on unlayered ice-silicate targets and pure ice targets for the purposes of comparison. Impact velocities ranged from 1 to 7 km S-1 using a range of projectile sizes and materials including stainless steel, titanium, aluminium and copper. Data from previous work undertaken at the University of Kent is incorporated in order to provide a more complete picture of target behaviour.
6
Kato, Ryo. "Interfacial interactions in polymer layered silicate nanocomposites." Thesis, Manchester Metropolitan University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491172.
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Polymer layered silicate nanocomposites (PLSN) have attracted great interest because they exhibit remarkable improvements in materials properties relative to pristine polymers. Successful formation of a PLSN is critically dependent on generation of very high interfacial area in the composite. This is accomplished when the stacks of silicate platelets (tactoids) split into discrete platelets. The latter phenomenon is known as exfoliation and is strongly influenced by interfacial chemistry (i.e. structure and properties of the interface or interphase) associated with the edge and basal surfaces of the silicate platelets, chemical modification (usually with quaternary alkyl ammonium halides) of the latter and the resulting effect on interactions between the platelets themselves and polymer chains. Interactions between sodium montmorillonite (Na-MMT)/organically modified montmorillonite (o-MMT) and a variety of probes, some of which are intended to model the structures present in the components of a polyurethane (PU), epoxy resin and polystyrene system (PS), have been studied. The adsorption process was characterised using flow microcalorimetry (FMC) in conjuncqon with diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and wide angle x-ray scattering (\VAXS). Adsorption of hydrogen bondable groups, such as alcohol, ether, amine probes, onto Na-MMT was dominated by the hydrogen bonding interactions with hydrated Na+ ions and with the hydroxyl groups present at the platelet edges. Moreover, stronger interactions with hydrated Na+ ions led to greater retention of the probes after the desorption process. When the Na-MMT was moisturized at ambient atmosphere, hydrogen bondable probes showed a reversible adsorption. In contrast, chemical adsorption (reaction) dominated the adsorption of the isocyanate probe onto Na-MMT; the latter reacted either with the platelet edge hydroxyl groups forming a urethane linkage or with pre-adsorbed ambient water molecules adsorbed onto Na-MMT ultimately forming a physically adsorbed urea. In the case of o-MMTs, when only the platelet edge hydroxyl groups were available, hydrogen bondable probes showed a reversible adsorption. Reactions between reactive probes, including isocyanate and epoxide probes, and surfactant functional groups (OH and COOH groups) are affected by the gallery structures, such as the arrangement of surfactant within the galleries and level of surfactant intercalated. Adsorption of aromatic probes, including styrene, ethylbenzene and polystyrene, was dominated by the relatively weak dispersive interactions with the basal surfaces of o-MMT, and was significantly affected by the gallery structures ofo-MMT (surfactant level and surfactant structure). This study has provided valuable new insight into interactions in nanocomposite materials.
7
Lander, Julie-Anne. "Structure development in silicate-layered polymer nanocomposites." Thesis, Brunel University, 2002. http://bura.brunel.ac.uk/handle/2438/4390.
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The demands made of materials have resulted in the formation of complex composite structures; one such example of these is nanocomposites. This study is primarily devoted to the preparation and characterisation of nanocomposites. Reactively cast and reactively extruded nanocomposite strategies for the preparation of polyamide-6 composites were compared. The catalyst and activator system selected was based on an industrially successful combination. The extruder screw and barrel configuration used had previously been proven effective for the reactive polymerisation of polyamide-6. The principal objectives were the investigation of the influence of layered-silicates on both the microstructure and the physical properties of the composites. As well as the analysis of the mechanisms that influence the physical performance of the materials produced. The characterisation of the filler-matrix microstructure and its effect on physical properties of the composites were investigated using a range of chromatographic, microscopic, thermal and X-ray analytical techniques. Selected mechanical properties were measured using standard test procedures. Therefore results obtained and subsequent trends observed in reaction cast and reaction extruded nanocomposites could be compared and contrasted. The influence of the polymerisation conditions, residual monomer content and the nature of the composite structure produced were considered. It was observed that the nature of the matrix crystalline structure could be greatly influenced by the material composition, method of preparation and processing technique. The crystal form of the spherulites present appeared to be the key factor in influencing mechanical strength. The treatment of the silicate-layered clay successfully increased the inter-layer spacings, which was further increased by the presence of high shear forces.
8
Lewis, M. N. "Styrene-ethylene/butylene-styrene layered silicate nanocomposites." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432525.
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Ha, Yung-Hoon Sam 1975. "Hierarchical layered-silicate-- lamellar triblock copolymer nanocomposites." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29969.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2003.Includes bibliographical references.
The fundamental role of the layered-silicates in a styrene-butadiene-styrene triblock copolymer (SBS) as a function of layered-silicate dispersion during deformation was investigated. Predominantly immiscible composites of mixed morphology provided the initial proof that dramatic alteration of the SBS deformation behavior exists, but a clear understanding of the nature of reinforcement was precluded due to the fiber symmetric orientation of the SBS and the mixed clay morphologies. Following the theory of Vaia and Giannelis, use of a more hydrophobic organically modified clay resulted in an intercalated morphology with a near single crystalline texture of the SBS due to roll-casting. Significant heterogeneous deformation was observed at ambient conditions as well as at elevated temperature as verified through Cohen's affine deformation model in combination with Kratky's scattering pattern model. The intercalated morphology shows little or modest mechanical property enhancements at all temperatures studied. Exfoliated nanocomposite was produced by functionalization of the clay surfaces with polystyrene, altering the enthalpic interactions. Entropic interactions were also controlled by varying the molecular weight of the surfactant and the grafting density and shows remarkable agreement with the theory proposed by Balazs et al. Due to the increase surface volume ratio of the clay, a flipping transition of the block copolymer morphology was observed during roll-casting producing a near single crystalline parallel/parallel clay/BCP orientation. The modulus was relatively unaffected whereas the toughness increased significantly due to an earlier onset of strain hardening.
by Yung-Hoon Sam Ha.
Ph.D.
10
Kornmann, Xavier. "Synthesis and characterisation of thermoset-layered silicate nanocomposites." Doctoral thesis, Luleå, 2001. http://epubl.luth.se/1402-1544/2001/14/index.html.
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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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Katoch, Sunain, Vinay Sharma, and Patit Paban Kundu. "Swelling kinetics of unsaturated polyester–layered silicate nanocomposite." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186443.
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Kinetics of swelling and sorption behavior of unsaturated polyester nanocomposite (based on glycolyzed PET, maleic anhydride, styrene, and montmorillonite) synthesized by two different mixing methods, simultaneous and sequential is studied in acetic acid at different temperatures. The values of n in the transport equation are found to be below 0.5, showing non-Fickian or pseudo-Fickian transport in the polymers. The dependence of diffusion coefficient on the mixing methods and temperature has also been studied for the unsaturated polyester nanocomposite. The diffusion coefficients in simultaneous mixing samples decrease with an increase in the mixing time in the samples. In case of the sequential mixing samples, the diffusion coefficient increases with an increase in mixing time. The diffusion coefficient increases with an increase in temperature for all the unsaturated polyester nanocomposite samples. The sorption coefficient increases with an increase in the mixing time for all the samples synthesized by in-situ mixing method. The crosslink density (calculated from the CH3COOH swelling) ranges from 5.014 to 7.092 × 102 mol/cm3 for simultaneous mixed samples and 5.212 to 7.192 × 102 mol/cm3 for sequentially mixed samples.
13
Limpanapittayatorn, Pipat. "Factors influencing the formation of polymer layered silicate nanocomposites." Thesis, Manchester Metropolitan University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400600.
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Mollet, Vincent. "Characterization of exfoliation and intercalation in polymer layered silicate nanocomposites." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82620.
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A microstructural and morphological analysis of polymer/layered silicate nanocomposites (PLSN) is proposed. The analysis employs wide angle x-ray diffraction (WAXD) and to a larger extent, transmission electron microscopy (TEM).Polyamide-6 (PA) and polystyrene (PS) nanocomposites were produced by melt processing the resins with several grades of organically modified clay in a twin screw extruder (TSE). The TSE was operated in two different configurations (C and A). The effects of the type of organoclay, TSE configuration, clay concentrations and addition of a compatibilizing agent in the matrix were evaluated.
Both WAXD and TEM analysis revealed exfoliated or intercalated structures for PA-based nanocomposites depending on the organoclay, whereas PS-based nanocomposites mainly exhibited intercalated structure. A quantitative analysis of the diffraction peaks was carried out in order to identify the ambiguous nature of the secondary reflection peak. Depending on the case, it is proposed that the secondary reflection peak could be due to a combination of secondary reflection of the intercalated structure and a primary reflection of a collapsed structure of the layered silicate particles.
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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.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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Tarrant, Anne Elizabeth. "Thermoset-acrylic/layered-silicate nanocomposites : synthesis and structure-property relationships." Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/7515.
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Tasan, Cemal Cem. "Production And Characterization Of Resol Type Phenolic Resin / Layered Silicate Nanocomposites." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605992/index.pdf.
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ABSTRACT
PRODUCTION AND CHARACTERIZATION OF RESOL TYPE PHENOLIC RESIN / LAYERED SILICATE NANOCOMPOSITES
TaSan, Cemal Cem M.S.,
Department of Metallurgical and Materials Engineering Supervisor: Assoc.Prof. Cevdet Kaynak
April 2005
133 Pages
Polymer / layered silicate (P/LS) nanocomposites belong to one of the most promising group of materials of the past few decades and most probably for the near future. Combining two of the most widely studied topics of material science: composite materials and nanotechnologyP/LS research have drawn great attention starting with the pioneering works of Toyota Research Group in 1980&rsquo
s. The research is now being carried out world wide
since the excellent properties of these new materials, which is achieved by using very low amounts of a cheap reinforcement material (clay), increases the interest on these materials everyday after. In this present study, the object was to investigate the production parameters of phenol formaldehyde based layered silicate nanocomposites. For this purpose, 14 different specimen groups were produced
using two different resol type phenolic resins (PF76 and PF76TD) as the matrix
and 9 different montmorillonite clays (Rheospan, Resadiye, Cloisite Na+, 10A, 15A, 20A, 25A, 30B, 94A) as the reinforcement phase. Initially the curing schedules for the available resins were experimentally determined. Then, a short and effective mixing procedure for the thermosetting resin and the montmorillonite clay was developed. The effects of several processing parameters
such as clay type, clay source, clay content, clay modification, resin type, resin cure type, cure cycle and mixing cycle were determined by X-ray Diffraction, Scanning Electron Microscopy and Mechanical Tests. Then, Transmission Electron Microscopy was used to investigate the level of intercalation and/or exfoliation of the layered silicates. Finally, Differential Scanning Calorimetry was also carried out to analyse thermal properties of the specimens. It was concluded that, a partially intercalated and/or exfoliated structure could be obtained in resol type phenolic resin based systems at very low clay contents (such as 0,5%) leading to remarkable increases in mechanical properties (e.g. 66% increase in fracture toughness).
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Firthriyah, Nural Hidayati. "Structure Development and Properties of Flexible Polyurethane Foam-Layered Silicate Nanocomposites." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503646.
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Sheng, Nuo 1977. "Micro/nanoscale modeling of anisotropic mechanical properties of polymer/layered-silicate nanocomposites." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/28257.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (leaves 123-125).
Polymer nano-clay composites have been observed to exhibit dramatic enhancements in mechanical properties with relatively low filler loadings (1-4 percent volume fraction). These property enhancements have been speculated to be a result of the change in polymer morphology and properties within the polymer/particle interfacial regions, due to the nanometer length scale and the large interface area/unit volume of the nanoparticles. In this work, the potential contribution of composite-level effects on the observed enhancements is explored. Two-dimensional models of various representative volume elements (RVEs) of the underlying structure of the polymer nano-clay composite are constructed. These models are characterized by clay particle volume fraction and micro/nano scale morphological features such as clay particle aspect ratio (length/thickness, L/t), clay particle distribution (random vs. regular patterns) and clay particle orientation distribution. Macroscopic moduli of these RVEs are predicted as a function of these geometrical parameters as well as particle and matrix stiffness parameters through FEM simulations. Effective properties of intercalated clay particles have been estimated in terms of characteristic clay structural parameters (interlayer spacing and number of layers), with additional information from molecular dynamics simulations of silicate layer stiffness. The predictions of macroscopic stiffness from these two-dimensional micromechanical models, based on structure-dependent particle volume fraction and properties, are consistent with experimental observations. Furthermore, studies of the local stress/strain fields show that the stiffness enhancement comes through the efficient load transfer mechanism in the high aspect ratio fillers, modulated by the strain shielding effect in the matrix. These results suggest that physically-based composite level interpretations may explain the stiffness enhancement mechanism of polymer nanocomposites to a large degree. The adopted methodology offers promise for study of related properties in polymer/layered-silicate nanocomposites.
by Nuo Sheng.
S.M.
20
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.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.
21
Aldousiri, Barjas. "The manufacture, properties and characterisation of layered silicate reinforced spent polymer nanocomposites." Thesis, University of Portsmouth, 2011. https://researchportal.port.ac.uk/portal/en/theses/the-manufacture-properties-and-characterisation-of-layered-silicate-reinforced-spent-polymer-nanocomposites(e76905dd-2e8e-46e5-959f-2ee6ac05e684).html.
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This research work deals with the manufacture, properties and characterisation of layered silicate (LS) reinforced novel spent polymer nanocomposites. Three different materials used for nanocomposites preparation were polyamide 12 (PA-12), DuraForm polyamide 11 (EX) and Glass Filled polyamide 12 (GF-12). Various concentrations (1, 3, 5 and 7 wt. %) of the layered silicates were dispersed in three different types of spent polyamide matrix by the melt compounding method, in order to investigate the effect of LS reinforcement on mechanical and thermal properties of spent polymer. The interlayer d-spacing, interlamellar structure and surface morphologies were investigated by wide angle x-ray diffraction (WXRD), transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. The tensile strength and modulus of the un-reinforced spent PA-12 samples were found to increase with the incorporation of LS. This improvement in the tensile strength and modulus appear to be directly related to the LS loading. Similarly, the flexural strength and modulus were found to increase significantly with incorporation of the LS reinforcement. Nanoindentation test results were used to evaluate the nanomechanical properties (i.e. hardness and modulus) of spent PA-12/nanocomposites. The results show that the hardness and modulus of LS reinforced spent PA-12 nanocomposites were higher compared to the un-reinforced spent PA-12 sample. Crystallisation temperature measured using DSC showed a gradual decrease as the LS loading increased. For spent PA-12 nanocomposites samples the melting temperature slightly increased with 1 and 3 wt. % of LS loading when compared with the unreinforced spent PA-12 sample. However, samples with 5 and 7 wt. % of LS have approximately the same melting temperature of the un-reinforced spent PA-12 sample. Glass transition temperature (Tg) of the spent PA-12 nanocomposites slightly decreased in comparison to the un-reinforced spent PA-12 sample. It was found that the incorporation of LS does not affect or improve the tensile strength and modulus of the spent EX nanocomposites. However, flexural strength and modulus for the spent EX nanocomposites are improved when compared with the un-reinforced spent EX sample. The nanoindentation results show that as the LS concentration increased up to 3 wt.%, the hardness and modulus were improved. Different levels of layered silicates dispersion as characterised by XRD, TEM and SEM correlated strongly with improvements in mechanical and thermal performances. The crystallisation temperature of spent EX and GF-12 nanocomposites samples shows gradual increases with increasing LS loading. The measured crystallisation temperature was approximately 6˚C higher for the spent EX nanocomposites samples than for the un-reinforced spent EX sample. Secondary heating of the un-reinforced spent EX sample and the nanocomposites samples resulted in an increase in melting temperature which corresponded to increasing LS loading. However, the melting temperature for all the spent GF-12 nanocomposites samples was similar to the one for the un-reinforced spent GF-12 sample. It was found that Tg values decreased with increased in LS loading for spent GF-12 samples. The presence of layered silicate did not contribute in improving tensile and flexural strength of spent GF-12 matrix. However, the hardness and elastic modulus were found to increase with increased layered silicates loading up to 7 wt.%.
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Martinez, Vilarino Sofia. "Thermal and transport properties of layered silicate nanomaterials subjected to extreme thermal cycling." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/556.
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There is a raising need to design a safe and efficient cryogenic fuel tank for the new generation of reusable launch vehicles. The new tank design focuses on composite materials that can achieve the drastic reduction of empty/non-payload and structural weight. In addition to the materials to be compatible with cryogenic temperatures, interior components of the vehicle may be subjected to significantly elevated temperatures due to heat conduction from the vehicle surfaces during and after atmospheric re-entry. Therefore, there is the need to understand the performance of the composites after experiencing extreme thermal environments. Polymer-layered nanocomposites were studied to determine if they can reduce the permeation to the liquid nitrogen used as fuel in the next generation of space vehicles. Due to the non-permeable nature of the silicates and the exfoliated structure they adopt into the polymer matrix the addition of nanoclays into a polymer is expected to reduce the permeation to several gases without sacrificing the mechanical strength of the nanocomposite as well as providing additional improvements such as increase of thermal stability of the nanocomposite. Several types of matrixes modified with different types and content of nanoclays were tested and their permeability coefficient was calculated. The permeability values obtained for the different formulations assisted to understand the transport properties of nanoclay modified composites. In addition to this, thermal characterization was performed with the help of dynamic mechanical analysis, thermogravimetric analyses and differential scanning calorimetry studies. To determine if the nanoclay modified nanocomposites were affected by extreme temperatures the samples were subjected to thermal cycling. Comparison of the transport and thermal properties before and after cycling helped to analyze the effect of the addition of the nanoclays in the nanocomposites. Positron annihilation spectroscopy (PAS) was utilized to comprehend how the distribution of the free volume was affected by the presence of the nanoclays and by the thermal cycling applied. Different permeability models were utilized in an attempt to validate the experimental results of the different nanocomposite structures. This analysis was used to provide additional insight into many aspects of the experimental results obtained in this study.
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Katoch, Sunain, Vinay Sharma, and Patit Paban Kundu. "Swelling kinetics of unsaturated polyester–layered silicate nanocomposite: depending on the fabrication method." Diffusion fundamentals 13 (2010) 1, S. 1-31, 2010. https://ul.qucosa.de/id/qucosa%3A13860.
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Kinetics of swelling and sorption behavior of unsaturated polyester nanocomposite (based on glycolyzed PET, maleic anhydride, styrene, and montmorillonite) synthesized by two different mixing methods, simultaneous and sequential is studied in acetic acid at different temperatures. The values of n in the transport equation are found to be below 0.5, showing non-Fickian or pseudo-Fickian transport in the polymers. The dependence of diffusion coefficient on the mixing methods and temperature has also been studied for the unsaturated polyester nanocomposite. The diffusion coefficients in simultaneous mixing samples decrease with an increase in the mixing time in the samples. In case of the sequential mixing samples, the diffusion coefficient increases with an increase in mixing time. The diffusion coefficient increases with an increase in temperature for all the unsaturated polyester nanocomposite samples. The sorption coefficient increases with an increase in the mixing time for all the samples synthesized by in-situ mixing method. The crosslink density (calculated from the CH3COOH swelling) ranges from 5.014 to 7.092 × 102 mol/cm3 for simultaneous mixed samples and 5.212 to 7.192 × 102 mol/cm3 for sequentially mixed samples.
24
Gintert, Michael Jason. "A NOVEL APPROACH TO OBTAIN HIGH PERFORMANCE LAYERED SILICATE THERMOSET POLYIMIDE MATRIX NANOCOMPOSITES." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1185469995.
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Alateyah, Abdulrahman Ibrahim S. "Characterisations and properties of nanocomposites based upon vinyl ester matrix and layered silicate." Thesis, University of Portsmouth, 2014. https://researchportal.port.ac.uk/portal/en/theses/characterisations-and-properties-of-nanocomposites-based-upon-vinyl-ester-matrix-and-layered-silicate(284a9725-a8b1-4d34-9f30-64926735cd1b).html.
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In this research, various concentrations of layered silicate based on vinyl ester nanocomposites were prepared and the effect of the incorporation of layered silicate into the polymer matrix on the different properties was investigated. The characterisations of interlaminar structure of the nanocomposites by X-ray Diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Spectrometry and Transmission Electron Microscopy are undertaken. This study revealed that the incorporation of layered silicate into the polymer matrix formed uniformly distributed nanocomposites structure at low clay content (i.e. 1, 2, and 3 wt.%). At 4 wt.% clay loading, the partially intercalated / exfoliated nanocomposites system was observed as proved by the different characterisations' results. However, the addition of more clay such as 5 wt.% resulted in decreasing the overall intercalation level due to the existence of aggregation layers. The addition of layered silicate into the vinyl ester matrix increased the environmental, mechanical and thermal properties, and the enhancements were correlated to the results of the characterisations' outputs. The mechanical properties such as flexural, tensile, nanoindentation, impact, and creep properties of neat samples were improved by the incorporation of layered silicate. The presence of layered silicate into the polymer matrix increased the tensile strength and modulus and flexural strength and modulus up to 4 wt.% clay content. The level of intercalation of nanocomposites played an important role in the improvements of the mechanical properties. So, the tensile and flexural properties were correlated to the characterisations' results. At 5 wt.% clay content, the modulus and strength of both tensile and flexural were reduced due to the effect of aggregation layers where the interfacial interaction between the layered silicate and the polymer is reduced. The nanoindentation test showed that the addition of layered silicate increased the reduced modulus and hardness of the nanocomposites compared to the neat vinyl ester. The presence of only 1 wt.% clay loading increased the hardness and reduced modulus at up to 13% and 11% respectively compared to the pristine polymer. The improvement percentage of hardness and modulus at 2 wt.% were 31% and 19% respectively. The ultimate improvements were observed at 4 wt.% clay loading, where the enhancements in hardness and modulus were 56 and 50% respectively compared to the neat vinyl ester. Further addition of clay resulted in marginal reductions in these properties. The impact properties of the neat vinyl ester and the nanocomposites were investigated using a low velocity impact testing. The addition of layered silicate into the polymer matrix showed that an optimum range of nanoclay reinforcement in the vinyl ester matrix can produce enhanced load bearing and energy absorption capability compared to the neat matrix. Likewise, the influence of the clay addition into the neat polymer on the creep relaxation behaviour at 25°C and 60°C was studied. In both cases, the presence of the layered silicate remarkably improved the creep behaviour. The strain reduction is related to the clay concentration level. The neat polymer illustrated higher strain compared to the nanocomposites samples. Moreover, the addition of layered silicate into the polymer matrix improved the thermal properties. Thermal Gravimetric Analysis (TGA) showed that the nanocomposites represent better stability compared to the neat polymer. The onset temperature of the nanocomposites was higher than the neat polymer. At 1, 2, 3, and 4, wt.% clay content, the improvements in onset temperature were 7 %, 4.2 %, 4 %, 2.5 % respectively compared to the virgin polymer. In addition, the incorporation of layered silicate into the polymer matrix increased the thermal conductivity. At 4 wt.% clay, the thermal conductivity was increased by 12% compared to the neat polymer. Differential Scanning Calorimetry (DSC) is also performed in order to study the effect of the addition of layered silicate into the polymer on the glass transition temperature. The level of intercalation is critical to the Tg values. The nanocomposites represented a marginal reduction in Tg, however at 4 wt.% clay loading the Tg was as same as the neat polymer which was traced to the well-dispersed structure. Furthermore, the study of environmental measurements, which included the water absorption behaviour and its effect on the nanoindentation test, was investigated. The improvement of the water repellence behaviour was observed for the nanocomposites. The enhancements in barrier properties were related to the clay content. At 5 wt.% clay loading, the reduction of water uptake was about 1266% compared to the neat polymer. The hardness and elastic moduli after water absorption was reduced due to the effect of water molecules entering into the polymer chains. However, the higher amount of clay reinforcement led to less reduction in hardness due to the formation of the barrier properties by the layered silicate. The hardness of neat polymer after immersing in water was reduced by 30% whereas the hardness of 5 wt.% nanocomposites showed only a reduction by 10.3% compared to the dry sample.
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Gatos, Konstantinos G. [Verfasser], and Jôzsef [Akademischer Betreuer] Karger-Kocsis. "Structure-Property Relationships in Rubber/Layered Silicate Nanocomposites / Konstantinos, G. Gatos ; Betreuer: Jôzsef Karger-Kocsis." Kaiserslautern : Technische Universität Kaiserslautern, 2018. http://d-nb.info/116023552X/34.
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Pourbeik, Pouya. "Nanostructure and Engineering Properties of 1.4 nm Tobermorite, Jennite and other Layered Calcium Silicate Hydrates." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32452.
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The nature of the calcium-silicate-hydrate phase in hydrated Portland cement has been the subject of considerable debate for decades. Various nanostructural models have been proposed including those constructed from colloidal-based particulate systems and those formulated on the basis of layered calcium-silicate-hydrates. These are examined in detail in the literature review section of the thesis. Relatively recent composition-based models have been proposed by Taylor and Richardson-Groves. These models contain structural elements comprised of 1.4 nm tobermorite and jennite. Details are also provided in the literature review. There is however a paucity of data on the engineering properties of pure calcium-silicate-hydrate phases and virtually none on the mechanical performance of 1.4 nm tobermorite and jennite. The global objective of this thesis was to examine the compatibility of the composition-based models with the engineering behaviour of the pure tobermorite and jennite phases. Pure phases of a variety of layered calcium-silicate-hydrates were synthesized and novel techniques developed to determine their engineering characteristics in a variety of test environments. The silicate phases investigated included high temperature silicates e.g. gyrolite as these layered structures are known to be cross-linked. Investigation of the role of ‘structural’ water in layered silicates was also a part of these studies.
The thesis is based on a series of twelve refereed journal papers by the candidate (eight are published or accepted and four have been submitted for publication). The research is reported in four parts with each part comprised of three papers. Each part provides insight into the nanostructure of C-S-H in hydrated cement. The arguments developed evolve from an assessment of various factors including aging and the state of water in the layered silicates.
The first part of the thesis focuses on the development and application of dynamic mechanical thermo-analysis methods that are sensitive to phase changes and are useful for assessing the compatibility of engineering behaviour with model composition based on 1.4 nm tobermorite and jennite. The second part represents a study of volume stability and mechanical property-porosity relationships for the pure silicate phases that are germane to these studies. The third part focuses on prolonged aging and role of structural water in cement paste hydrated for 45 years. The fourth and final part attempts to address the role of layer structure e.g. cross-linking of silicate sheets on engineering behaviour. The non-uniqueness of modulus of elasticity with respect to equilibrium moisture content is demonstrated. Structurally related irreversible effects that are dependent on drying history are rationalized.
A summary chapter is provided wherein the evidence for a composition-based model with tobermorite and jennite structural units is rationalized in terms of the experimental evidence provided in this study and suggestions for future research are discussed.
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Al-Yamani, Faisal M. "A route to enhanced intercalation in rubber-silicate nanocomposites." Akron, OH : University of Akron, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1124544242.
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Thesis (M.S.)--University of Akron, Dept. of Polymer Engineering, 2005."August, 2005." Title from electronic thesis title page (viewed 11/28/2005) Advisor, Lloyd Goettler; Faculty Reader, Avraam I. Isayev; Department Chair, Sadhan C. Jana; Dean of College, Frank N. Kelley; Dean of Graduate School, George R. Newkome. Includes bibliographical references.
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Samaniuk, Joseph Reese. "Improving the Exfoliation of Layered Silicate in a Poly(ethylene terephthalate) Matrix Using Supercritical Carbon Dioxide." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32187.
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Supercritical carbon dioxide (scCO2) was used as a processing aid to improve the level of exfoliation achievable in a PET-layered silicate nanocomposite produced from melt compounding. Layered silicate and scCO2 were allowed to mix for a period of time before being released into the second stage of a single screw extruder. The rapid expansion forced silicate particles into a modified hopper containing neat PET pellets. The mixture of layered silicate and PET was immediately melt mixed in a single screw extruder, cooled in a water bath and pelletized. Two sets of samples each containing layered silicate with different surface chemistries were produced with this method at 1, 3 and 5 wt% silicate. For comparison, samples of the same weight fraction and type of silicate were produced from a traditional melt compounding method. Wide angle x-ray diffraction (WAXD), mechanical testing and rheological analysis were used in order to characterize the silicate morphology, the composite mechanical properties and the relative amount of degradation between the various samples. Results show that scCO2 processed samples contain a higher degree of layered silicate exfoliation than samples produced with traditional melt compounding. Mechanical property improvements are shown to be dependent on the type of silicate surface modification employed. Finally, degradation of the PET matrix appears to be far less extensive in the scCO2 processed samples as shown from rheological data.Master of Science
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Zhu, Bin. "Polystyrene Based Layered Silicate Nanocomposite Foam Using Carbon Dioxide as Blowing Agent and Shear Rheology Study." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338226070.
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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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Kalkan, Zehra Sibel. "THE GENERATION AND THERMO-MECHANICAL CHARACTERIZATION OF ADVANCED POLYAMIDE-6,6 NANOCOMPOSITES USING INTERFACIAL POLYCONDENSATION." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1153753352.
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Strauss, William C. "Saturation and foaming of thermoplastic nanocomposites using supercritical CO2." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4745/.
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Polystyrene (PS) nanocomposite foams were prepared using supercritical fluid (SCF) CO2 as a solvent and blowing agent. PS was first in-situ polymerized with a range of concentrations of montmorillonite layered silicate (MLS). The polymerized samples were then compression molded into 1 to 2mm thick laminates. The laminates were foamed in a batch supercritical CO2 process at various temperatures and pressures from 60°-85°C and 7.6-12MPa. The resulting foams were analyzed by scanning electron microscopy to determine effect of MLS on cellular morphology. Differential scanning calorimetry was used to determine the impact of nanocomposite microstructure on glass transition of the foamed polymer. X-ray diffraction spectra suggested that the PS/MLS composite had an intercalated structure at both the 1% and 3% mixtures, and that the intercalation may be enhanced by the foaming process.
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Silva, Rafael Caetano Jardim Pinto da. "Síntese e caracterização de nanocompósitos do tipo polímero/silicatos lamelares com propriedades anisotrópicas via polimerização RAFT em emulsão." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/97/97136/tde-01022016-143552/.
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Nos últimos anos, a incorporação de partículas inorgânicas em uma matriz polimérica com a finalidade de se obter sistemas híbridos orgânico/inorgânico utilizando diferentes técnicas de polimerização tem recebido grande atenção. Neste sentido, preservar e controlar as propriedades físico-químicas das partículas inorgânicas torna-se essencial para manter a integridade destas em nanoescala, bem como para obtenção de dispersões uniformes, magnificando os efeitos de reforço e demais ganhos de propriedades desejadas para a matriz polimérica. Quando se utiliza partículas inorgânicas anisotrópicas tais como a montmorilonita, silicato lamelar mais utilizado para obtenção de nanocompósitos do tipo polímero/silicato lamelar, este controle apresenta-se como um problema particularmente desafiador. Nesse contexto, a polimerização radicalar controlada (PRC) vem se destacando como uma importante via para atingir os objetivos mencionados acima, encontrando-se na literatura diversas estratégias de síntese em meio a solventes orgânicos na qual a efetiva nanoencapsulação de partículas inorgânicas dá-se por meio do crescimento de cadeias poliméricas na superfície destas estruturas inorgânicas. Entretanto, poucos trabalhos são encontrados envolvendo rota de obtenção semelhante em meio aquoso, tais como suspensão, emulsão e miniemulsão, processos estes que possuem grande interesse industrial, ambiental e viabilidade real de ampliação de escala quanto à produção.Desta forma, o objetivo deste projeto de pesquisa concentra-se na síntese e na caracterização de nanocompósitos do tipo polímero/silicato lamelar via polimerização radicalar controlada em emulsão. As polimerizações radicalares controladas de estireno em emulsão, via mecanismo de transferência reversível de cadeia por adição-fragmentação (RAFT), foram conduzidas na presença de argila montmorilonita (MMT) e mediadas por dois macroagentes de transferência de cadeia com grupo funcional tri-tioéster, sendo o primeiro constituído de cadeia polimérica não iônica de monoetil éter de poli(etilenoglicol) (MPEG-CPP) e outro derivado do MPEG-CPP contendo adicionalmente um bloco ionizável de poli(ácido metacrílico) incorporado à cadeia polimérica (MPEG-b-PMAA-CPP). Foram avaliados inicialmente os parâmetros de adsorção dos macroagentes MPEG-CPP e MPEG-b-PMAA-CPP na superfície da MMT bem como a influência das variáveis do processo de polimerização na adsorção dos macroagentes na MMT e na estabilidade coloidal dos complexos macroagente RAFT / MMT formados. Posteriormente foram avaliados os efeitos do pH, das concentrações dos macroagente RAFT e de MMT, bem como do tipo de iniciador na cinética de polimerização em emulsão \"ab-initio\" de estireno, conduzidas na ausência de surfatantes. As técnicas utilizadas nos estudos de adsorção e para a caracterização das argilas, dos látices híbridos e dos materiais nanocompósitos incluem: espectroscopia de UV-vis, espalhamento dinâmico de luz (DLS), espalhamento eletroforético de luz (ELS), cromatografia de permeação em gel (GPC), análise termogravimétrica (TGA), calorimetria diferencial de varredura (DSC) e microscopia eletrônica de transmissão (TEM).In recent years, the incorporation of inorganic particles in a polymer matrix in order to obtain hybrid organic/inorganic systems using different polymerization techniques have received great attention. In this sense, preserve and manage the physical and chemical properties of inorganic particles is essential to maintain its integrity at the nanoscale, as well as to obtain uniform dispersions of them, magnifying the effects of reinforcement and other desired properties into the polymer matrix. When using anisotropic inorganic nanoobjects such as montmorillonite, the most used layered silicate to obtain polymer / layered silicate nanocomposites, this control is presented as a particularly challenging problem. In this context, the controlled radical polymerization (CRP) has been highlighted as an important way to achieve the goals mentioned above, several strategies of organic solvent-borne synthesis can be found in literature in which the effective nanoencapsulation of inorganic particles is given by through the growth of polymer chains on the surface of these inorganic structures. However, few works are found involving obtaining similar route in water-borne, such as suspension, emulsion, miniemulsion, these procedures have great interest in industrial, environmental and actual feasibility of expanding scale in manufacture. Thus, the objective of this research project focuses on the synthesis and characterization of nanocomposite-type polymer / layered silicate via controlled radical polymerization in emulsion media. The controlled radical polymerizations in emulsion, via transfer mechanism for the reversible addition-fragmentation chain (RAFT) have been conducted in the presence of montmorillonite clay (MMT) and mediated by two macroRAFT agents with functional tri-thioesters groups, being the first one constituted by a nonionic poly(ethylene glycol) methyl ether polymeric chain (MPEG-CPP) and the second on being MPEG-CPP derived but containing additionally an ionizable block of poly(methacrylic acid) inserted to its polymeric chain. The parameters of adsorption of MPEG-CPP and MPEG-b-PMAA-CPP agent on the surface of MMT as well as the influence of the polymerization process variables on the adsorption of PEO-RAFT in MMT and colloidal stability of the complex formed macroRAFT agents / MMT were firstly evaluated. Subsequently, the influence of pH, macroRAFT agents and MMT concentrations as well as the type of initiator on the kinetics of RAFT emulsion polymerization were equally evaluated. The techniques used the for adsorption studies and characterization of clays, latexes of hybrid materials and nanocomposites include: UV-vis spectroscopy, dynamic light scattering (DLS), electrophoretic light scattering (ELS), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), dynamic scanning calorimetry (DSC) and transmission electron microscopy (TEM).
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Chaparro, Thaíssa de Camargo. "Síntese de nanocompósitos com propriedades anisotrópicas via polimerização radicalar controlada em emulsão." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/97/97134/tde-13092016-110713/.
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Este trabalho de tese tem como objetivo a preparação de látices nanocompósitos à base da argila Laponita RD em emulsão aquosa, via polimerização radicalar controlada por transferência de cadeia via adição-fragmentação reversível (RAFT). A Laponita foi escolhida como carga inorgânica devido principalmente à forma anisotrópica de suas lamelas, o que permite a elaboração de filmes nanoestruturados, mas também por suas propriedades térmicas e mecânicas, por sua alta pureza química e pela distribuição uniforme, em termos de tamanho, de suas partículas. Inicialmente, polímeros hidrofílicos (macroRAFT) à base de poli(etileno glicol) (PEG), de ácido acrílico (AA) ou de metacrilato de N,N-dimetilaminoetila (DMAEMA) que contêm unidades hidrofóbicas de acrilato de nbutila (ABu) (em alguns casos) e um grupo tritiocarbonílico terminal foram sintetizados. Em seguida, a interação entre os macroagentes de controle (macroRAFTs) e a argila foi estudada através de isotermas de adsorção. Atuando como agentes de acoplamento e estabilizantes, esses macroRAFTs foram então utilizados na copolimerização em emulsão do (met)acrilato de metila e do ABu em processo semicontínuo na presença da argila Laponita. Partículas de látex híbrido de diferentes morfologias foram obtidas e os resultados foram correlacionados à natureza e à concentração dos macroRAFTs, ao pH da dispersão macroRAFT/Laponita, à temperatura de transição vítrea do copolímero final (função da composição da mistura de monômeros hidrofóbicos) e às condições de polimerização. As análises de cryo-TEM indicam a formação de lamelas de Laponita decoradas com partículas de polímero (várias partículas de látex localizadas na superfície das lamelas), de partículas do tipo dumbbell, janus, blindadas (partículas de látex decoradas com lamelas de argila em sua superfície) ou ainda de partículas multiencapsuladas (diversas lamelas encapsuladas dentro de uma única partícula de látex). As propriedades mecânicas dos filmes de polímero/Laponita foram estudadas por análise dinâmico-mecânica e correlacionadas à morfologia das partículas e à microestrutura dos filmes.The aim of this work is to prepare Laponite RD-based nanocomposite latexes by aqueous emulsion polymerization, using the reversible addition-fragmentation chain transfer (RAFT) polymerization. Laponite platelets were selected as the inorganic filler due, especially, to their anisotropic shape, which allows the production of nanostructured films, but also for their thermal and mechanical properties, their high chemical purity and the uniform dispersity of the platelets. Hydrophilic polymers (macroRAFT) composed of poly(ethylene glycol) (PEG), acrylic acid (AA) or N,N-dimethylaminoethyl methacrylate (DMAEMA) and comprising hydrophobic n-butyl acrylate (BA) units (in some cases) and trithiocarbonate terminal group were initially synthesized. Then, the interaction between the macroRAFTs and the clay was studied through the plot of adsorption isotherms. By acting as coupling agents and stabilizers, the macroRAFT agents were used in the emulsion copolymerization of methyl (meth)acrylate and BA by semi-continuous process in the presence of the clay. Hybrid latex particles with different morphologies were obtained and the results were associated to the nature and concentration of the RAFT (co)polymers, to the pH of the macroRAFT/Laponite dispersion, the glass transition temperature of the final copolymer (function of the composition of the hydrophobic monomers mixture) and to the polymerization conditions. The cryo-TEM images indicate the formation of polymerdecorated Laponite platelets (several latex particles located at the surface of the platelets), dumbbell-like, janus, Laponite-decorated (armored) latex particles, and multiple encapsulated particles (several platelets inside each latex particle). The mechanical properties of polymer/Laponite films were studied by dynamic mechanical analysis and correlated with the particles morphology and the films microstructure.
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De, Camargo Chaparro Thaissa. "Synthesis of nanocomposites with anisotropic properties by controlled radical emulsion polymerization Lorena." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1045/document.
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L'objectif de ce travail de thèse est de préparer des latex nanocomposites à base d’argile, la Laponite RD, en émulsion aqueuse, à l'aide de la polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT). Les plaquettes de Laponite ont été choisies comme charge inorganique surtout pour leur anisotropie de forme, ce qui pourrait permettre l’elaboration de films nanostructurés, mais aussi pour leurs propriétés thermiques et mécaniques, leur pureté chimique élevée et la distribution uniforme en taille des plaquettes. Des polymères hydrophiles (macroRAFT) à base de polyéthylène glycol (PEG), d’acide acrylique (AA) ou de méthacrylate de N,N- diméthylaminoéthyle (DMAEMA) et comportant des unités hydrophobes d’acrylate de n-butyle (ABu) (dans certains cas) et un groupe trithiocarbonate terminal, ont été tout d'abord synthétisés. Ensuite, l'interaction entre les macroRAFTs et l’argile a été étudiée à travers le tracé des isothermes d'adsorption. En agissant comme des agents de couplage et des stabilisants, ces macroRAFTs ont eté utilisés dans la copolymérisation en émulsion du (méth)acrylate de méthyle et de l’ABu en mode semi-continu en presence d’argile. Des particules de latex hybrides de différentes morphologies ont été obtenues et les morphologies ont été reliées à la nature et à la concentration de l’agent macroRAFT, au pH de la dispersion macroRAFT/Laponite, à la température de transition vitreuse du copolymère final (fonction de la composition du mélange de monomères hydrophobes) et aux conditions de polymérisation. Les analyses par cryo-MET indiquent des plaquettes de Laponite décorées par des particules de polymère (plusieurs particules de latex en surface des plaquettes d'argile), des particules ‘haltère’, janus, ‘carapace’ (particules de latex décorées en surface par les plaquettes de Laponite) ou encore des particules multi-encapsulées (plusieurs plaquettes encapsulées dans chaque particule de latex). Les propriétés mécaniques des films de polymère/Laponite ont été étudiées par spectrométrie mécanique dynamique et corrélées à la morphologie des particules et à la microstructure des filmsThe aim of this work is to prepare Laponite RD-based nanocomposite latexes by aqueous emulsion polymerization, using the reversible addition-fragmentation chain transfer (RAFT) polymerization. Laponite platelets were selected as the inorganic filler due, especially, to their anisotropic shape, which allows the production of nanostructured films, but also for their thermal and mechanical properties, their high chemical purity and the uniform dispersity of the platelets. Hydrophilic polymers (macroRAFT) composed of poly(ethylene glycol) (PEG), acrylic acid (AA) or N,N-dimethylaminoethyl methacrylate (DMAEMA) and comprising hydrophobic n-butyl acrylate (BA) units (in some cases) and trithiocarbonate terminal group were initially synthesized. Then, the interaction between the macroRAFTs and the clay was studied through the plot of adsorption isotherms. By acting as coupling agents and stabilizers, the macroRAFT agents were used in the emulsion copolymerization of methyl (meth)acrylate and BA by semi-continuous process in the presence of the clay. Hybrid latex particles with different morphologies were obtained and the results were associated to the nature and concentration of the RAFT (co)polymers, to the pH of the macroRAFT/Laponite dispersion, the glass transition temperature of the final copolymer (function of the composition of the hydrophobic monomers mixture) and to the polymerization conditions. The cryo-TEM images indicate the formation of polymerdecorated Laponite platelets (several latex particles located at the surface of the platelets), dumbbell-like, janus, Laponite-decorated (armored) latex particles, and multiple encapsulated particles (several platelets inside each latex particle). The mechanical properties of polymer/Laponite films were studied by dynamic mechanical analysis and correlated with the particles morphology and the films microstructure
Este trabalho de tese tem como objetivo a preparação de látices nanocompósitos à base da argila Laponita RD em emulsão aquosa, via polimerização radicalar controlada por transferência de cadeia via adição-fragmentação reversível (RAFT). A Laponita foi escolhida como carga inorgânica devido principalmente à forma anisotrópica de suas lamelas, o que permite a elaboração de filmes nanoestruturados, mas também por suas propriedades térmicas e mecânicas, por sua alta pureza química e pela distribuição uniforme, em termos de tamanho, de suas partículas. Inicialmente, polímeros hidrofílicos (macroRAFT) à base de poli(etileno glicol) (PEG), de ácido acrílico (AA) ou de metacrilato de N,N-dimetilaminoetila (DMAEMA) que contêm unidades hidrofóbicas de acrilato de nbutila (ABu) (em alguns casos) e um grupo tritiocarbonílico terminal foram sintetizados. Em seguida, a interação entre os macroagentes de controle (macroRAFTs) e a argila foi estudada através de isotermas de adsorção. Atuando como agentes de acoplamento e estabilizantes, esses macroRAFTs foram então utilizados na copolimerização em emulsão do (met)acrilato de metila e do ABu em processo semicontínuo na presença da argila Laponita. Partículas de látex híbrido de diferentes morfologias foram obtidas e os resultados foram correlacionados à natureza e à concentração dos macroRAFTs, ao pH da dispersão macroRAFT/Laponita, à temperatura de transição vítrea do copolímero final (função da composição da mistura de monômeros hidrofóbicos) e às condições de polimerização. As análises de cryo-TEM indicam a formação de lamelas de Laponita decoradas com partículas de polímero (várias partículas de látex localizadas na superfície das lamelas), de partículas do tipo dumbbell, janus, blindadas (partículas de látex decoradas com lamelas de argila em sua superfície) ou ainda de partículas multiencapsuladas (diversas lamelas encapsuladas dentro de uma única partícula de látex). As propriedades mecânicas dos filmes de polímero/Laponita foram estudadas por análise dinâmico-mecânica e correlacionadas à morfologia das partículas e à microestrutura dos filmes
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Almuhamed, Sliman. "Study and Development of Nonwovens made of Electrospun Composite Nanofibers." Thesis, Mulhouse, 2015. http://www.theses.fr/2015MULH8864.
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L’électrofilage est actuellement la méthode la plus utilisée pour la production de nanofibres grâce à sa simplicité, sa reproductibilité et la possibilité d’être industrialisée. Grâce à leurs propriétés particulières telles qu’un grand rapport surface-volume, une porosité inter-fibre élevée et une grande capacité d’adsorption, les nanofibres électrofilées sont de bons candidats pour de nombreuses applications telles que la filtration, les masques respiratoires, les matériaux composites, etc. Cependant, certaines applications particulières, telles que les capteurs, les systèmes d'administration contrôlée de médicaments ou les super condensateurs, exigent que les nanofibres doivent présenter des propriétés complémentaires telles que la conductivité électrique, la porosité de surface de nanofibres, l’hydrophobicité, ou d’autres propriétés particulières. Certains nanomatériaux comme les nanotubes de carbone, la silice mésoporeuse ordonnée, les argiles, ont des propriétés particulières comme la conductivité électriques élevée des nanotubes de carbone, la porosité des matériaux de silice mésoporeuse ordonnée ou de l’argile. Ces propriétés des nanomatériaux peuvent être les fonctions complémentaires cherchées. Dans notre étude, des non-tissés composés de nanofibres de polyacrylonitrile chargées par nanotubes de carbone à multi-parois (MWNT), de la montmorillonite sodique (MMT-Na) ou de la silice mésoporeuse ordonnée (de type SBA-15), sont produits par électrofilage. Les résultats montrent que l’insertion de MWNT rend le non-tissé conducteur en augmentant la conductivité électrique volumique par six ordres de grandeur (de ~ 2×10-12 à ~ 3×10-6 S/m) avec un très faible seuil de percolation de 0.5 % massique. Lorsque le non-tissé est soumis à une compression, la conductivité électrique volumique augmente en augmentant la pression (jusqu’à ~ 2 kPa). Ces non-tissés conducteurs sont très intéressants pour le développement des capteurs à faible amplitude. Les résultats montrent aussi que l’accessibilité des pores des particules inorganiques (c’est-à-dire, les mésopores de SBA-15 et l’espace interfoliaire de MMT-Na) insérées dans la structure nano fibreuse est encore possible. Il a été trouvé que plus de 50% des mésopores de SBA-15 insérées sont encore accessibles quelles que soit les conditions de l’électrofilage et la fraction massique de SBA-15. En outre, l’insertion de ces particules inorganiques apporte plus de stabilité thermique aux nanofibres compositesElectrospinning is the most common method for the production of nanofibres due to its simplicity, repeatability, and the ability to be scaled up. Owing to their advanced properties like the high surface-to-volume ratio, high interfibrous porosity, high adsorption capacity, etc. electrospun nanofibers are good candidates for many applications such as filtration, respiratory masks, composite materials and others. However, some specific applications including sensors, controlled drug delivery systems, supercapacitors, etc. still require complimentary functions that do not exist in pristine nanofibers in their basic structure like the electrical conductivity, surface porosity of the nanofibers, hydrophobicity, and others.Nanomaterials like carbon nanotubes, ordered mesoporous silica, layered silicate, etc. are characterized by particular properties like the high electrical conductivity of carbon nanotubes, the porosity of ordered mesoporous silica or layered silicate. These particular properties of nanomaterials can fulfill of the targeted functions.In our study, nonwovens made from nanofibers of polyacrylonitrile incorporated with multiwalled carbon nanotubes (MWNT), layered silicate type Na-montmorillonite (Na-MMT) or ordered mesoporous silica type SBA-15 are successfully produced by electrospinning.Results reveal that the incorporation of MWNT altered the electrical state of the nonwoven from insolent to conductor where the volume electrical conductivity increased by six order of magnitude (from ~ 2×10-12 to ~ 3×10-6 S/m) with a very low percolation threshold of about 0.5 wt%. The application of mechanical pressure to the conductive nonwoven causes an increase in the volume electrical conductivity with the increase of the applied pressure (up to ~ 2 kPa). Such conductive nonwoven is very interesting for the development of sensor with low amplitude.Results also show that accessibility of the pores of the inorganic particles (i.e. mesopores of SBA-15 and interlayer space of Na-MMT) incorporated into the nanofibers is still possible. It is found that at least 50% of SBA-15 mesopores are still accessible whatever is the electrospinning conditions and SBA-15 mass fraction. In addition, the incorporation of the studied inorganic particles yields higher thermal stability for the composite nanofibers
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Bovey, J. "Modified layered silicates as acid catalysts." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596810.
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Three montmorillonites were modified by ion exchange, acid activation and pillaring. The acid activated clays were further pillared with Al, Ti, Zr or Cr polycations to produce pillared acid activated clays. Characterisation techniques included powder X-ray diffraction, FTIR spectroscopy, elemental analysis, N2 porosimetry and thermogravimetry. Characterisation revealed that the properties of the acid activated products were dependent upon the nature of the starting material and the conditions of activation. In turn, the properties of the pillared acid activated derivatives depended upon the particular and activated host and were generally intermediate between those of pillared raw clays and acid activated clays. In general, they possessed higher surface areas, pore volumes and acidities, wider pore size distributions and larger average pore diameters than their pillared raw counterparts. Variation of the pillaring cation revealed that the properties of the pillared acid activated materials depended on the pillar identity. Total surface areas and pore volumes of the Zr pillared materials were higher than those of the A1 pillared and Ti pillared counterparts. In general, Al pillared materials were the most microporous and Ti pillared materials were the most mesoporous. Three different methods reported in the literature were used to produce Ti pillared clays. Two of these methods led to products which did not appear to be pillared and which contained high amounts of precipitated anatase. A third method was successfully employed to produce Ti pillared acid activated clays and Ti pillared raw clays. The thermal stabilities of the products critically depended upon the identity of the host clay. Materials of maximal surface areas with large pore volumes were only formed upon calcination at 400 - 500oC. All the modifications of the original clays resulted in improved catalytic activity for a variety of acid catalysed reactions. In general, Al, Zr and Cr pillared acid activated clays were more active catalysts than their pillared raw counterparts. Ti pillared acid activated clays were, however, slightly less active than Ti pillared raw clays. The activities of the Ti pillared materials were comparable to those of the acid activated clays. In the one case examined, an overall order of activity existed which dependent on the identity of the pillaring cation such that Ti > Zr > Al ≥ Cr.
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Byrne, C. P. "Modification of layered silicates for PET nanocomposites." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431475.
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Pires, Cleo Thomas Gabriel Vilela Menegaz Teixeira. "Síntese e pilarização de ácidos silícicos lamelares." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250072.
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Orientador: Claudio AiroldiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Nos últimos anos tem sido observado um crescente interesse na obtenção de materiais lamelares modificados, devido as suas propriedades únicas e consequentes aplicações científicas e tecnológicas possíveis. Ácidos silícicos como a magadeíta, a kaneíta e a ilerita são compostos extremamente versáteis, podendo-se variar os seus espaçamentos basais a partir de intercalações com grupos de cadeia carbônica longa ou troca iônica. Outras alterações possíveis são as substituições isomórficas do silício por átomos tri- ou tetravalentes como alumínio e titânio respectivamente, modificando as propriedades químicas da lamela. Neste trabalho os ácidos silícicos lamelares magadeíta, ilerita e kaneíta foram sintetizados pelo método hidrotérmico, contendo também átomos de Al e Ti inseridos na estrutura. Em todos os casos observou-se que conforme aumenta-se a quantidade de metal adicionado ou o tempo de tratamento hidrotérmico, ocorrem transições de fase que seguem a ordem: amorfa, fase lamelar de interesse, cristobalita e tridimita, bem como suas misturas em situações intermediárias. Diferentes métodos de pilarização com TiO2 foram exaustivamente testados, variando-se uma série de parâmetros. O método que se mostrou mais eficiente consistiu na utilização de CTAB e TBAOH como agentes espaçadores sob refluxo a 353 K, seguido de adição direta do alcoxido no material intercalado seco, então refluxados a 363 K sob fluxo de nitrogênio. Os materiais obtidos por este método possuem mesoporos com 4,8 nm de diâmetro em media, porem a área superficial obtida foi de apenas cerca de 270 m g. Nos materiais pilarizados foram imobilizados os fotocatalisadores pirílio (TPP) e tiapirílio (TPTP) de modo a provar a eficiência na degradação fotocatalítica do pesticida metidation. Os materiais híbridos apresentaram desempenho superior aos fotocatalisadores orgânicos puros, o que representa um ótimo ponto inicial para a otimização deste processo. Também o comportamento fotofísico dos corantes impregnados nos materiais pilarizados foram estudados
Abstract: Recently, the interest to obtain modified layered materials is increasing, due to their properties and possible scientific and technological applications. Silicic acids such as magadiite, kenyaite and ilerite are extremely versatile compounds, allowing to vary the basal spacing by intercalation with carbonic long chains groups or ionic exchange process. Other possible modifications are isomorphic substitution by aluminum, titanium or iron atoms, with changeing the lamella chemical properties. In this investigation layered silicic acids magadiite, ilerite and kenyaite, containing also Al and Ti atoms inserted into the lamellar structure, were synthesized by hydrothermal method. For all cases was observed that with the increase of metal amount added or the hydrothermal treatment time there are phase transitions, following the order: from amorphous, to layered phase to crystobalite and tridimite, as mixtures of them at intermediate situations. Different pilarization methods with TiO2 were exhaustedly tested by varying many parameters. The most efficient methods used CTAB and TBAOH as swelling agents under reflux at 353 K, followed by direct alcoxide addition on the dry material, then refluxed at 363 K with dry nitrogen atmosphere. These materials have mesopores with 4.8 nm average diameter, nevertheless just 270 m g surface area. Some pillared materials were used to immobilize the photocatalyst pyrylium (TPP) and thiopyrylium (TPTP) and then test in the photocatalytic degradation of methidathion pesticide. The hybrid materials showed a better activity than that of pure organic, what means a great initial point to optimize this process. The photophysic behavior of impregnated dyes on pillared materials was also studied
Doutorado
Quimica Inorganica
Doutor em Ciências
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Jiang, Zhimei. "Structural investigations of layered silicates by vibrational spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ31440.pdf.
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Curcella, Alberto. "From silicen to Si films and clusters : silicon growth on Ag and layered materials studied by STM, GIXD and DFT." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS410.
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Dans cet ouvrage, je résume les études menées au cours de ma thèse concernant la synthèse de monocouches de silicium, de couches minces de Si sur Ag(111) et des dépôts de Si sur des matériaux lamellaires. Je présente des résultats originaux qui ont dévoilés des phénomènes physiques intéressants associés aux systèmes étudiés. Dans une première partie, je présente les résultats d’une étude combinant expériences et théorie, basée sur des mesures GIXD et des simulations DFT, visant à déterminer la disposition atomique exacte des structures de la monocouche de silicène sur Ag(111). Ensuite, je décris la structure atomique des couches minces de Si sur Ag(111). Je montre, au moyen de mesures GIXD, que le film de Si a une structure en forme de diamant avec des défauts d’empilement. Enfin, je détermine la structure atomique de la reconstruction de surface observée au-dessus du film de Si par des mesures de GIXD. Puis, par des études combinées de STM et DFT, je donne une image originale de la croissance de Si sur Ag(111) au-delà de la couverture de 1 ML de Si. Dans la dernière partie de cette thèse, je présente des études STM concernant l’évaporation de Si sur plusieurs matériaux lamellaires: HOPG, MoS2, TiTe2 et ZrSe2. Je montre que sur chacun de ces substrats la croissance de Si, à la fois pour température ambiante et pour des hautes températures, entraîne la formation de nanoclusters 3DIn this work I summarize the studies conducted during my PhD, concerning the synthesis of silicene layers and thin Si films on Ag(111) and Si deposition on layered materials. I present original results which unveil interesting physical phenomena associated with the system under study. In a first part, I present the outcomes of a combined experimental and theoretical study, based on GIXD measurements and DFT simulations, aimed to determine the exact atomic arrangement of the silicene monolayer structures on Ag(111). Afterwards I focus on the atomic structure of Si thin films on Ag(111). I show, by means of GIXD measurements, that the Si film has a diamond bulklike structure with stacking faults. Finally, I determine the atomic structure of the reconstruction observed on top of the aforementioned diamond bulklike Si film by menas of GIXD measurements. Then, by combined STM and DFT studies I give an original picture for Si growth on Ag(111) above 1 ML Si coverage. In the last part of this Thesis, I report STM studies regarding Si evaporation on several layered materials: HOPG, MoS2, TiTe2 and ZrSe2. I show that on each of these substrates and both for room temperature and high temperature growth, Si evaporation results in the formation 3D Si nanoclusters
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Reichel, Oliver [Verfasser]. "Synthesis and Properties of Photochromic Layered Silicates and Model Experiments for Colouring and Reinforcement in Organic Coatings by Layered Silicates / Oliver Reichel." Aachen : Shaker, 2014. http://d-nb.info/1050342216/34.
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Ramos, Francisca Solânea de Oliveira 1985. "Estruturas 3D a partir de estruturas 2D : transformações hidrotérmica e topotática." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250404.
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Orientador: Heloise de Oliveira PastoreDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: A aplicação dos silicatos lamelares como catalisadores apresenta como limitações as baixas área superficial e acidez, porém, esses sólidos têm como principais propriedades a reatividade dos grupos Si-OH e Si-ONa da superfície de suas lamelas e sua capacidade de troca iônica. Em função disso, esses sólidos podem sofrer uma variedade de modificações em sua superfície e em seu espaço lamelar e até passar de uma estrutura 2D para uma estrutura 3D. As lamelas do silicato lamelar Na-RUB-18, além de serem recobertas por Si-OH e Si-O, são constituídas de cavidades de quatro anéis de cinco membros [5], presentes tanto no RUB-24 quanto na MOR, assim como em outros zeólitos, indicando que tal lamelar seja potencial precursor de estruturas zeolíticas. Por tais motivos, o presente trabalho teve como objetivo estudar e descrever como o Na-RUB-18 se transforma nas estruturas zeolíticas MOR e RUB-24, por processos hidrotérmico e topotático, respectivamente, e como essas estruturas 2D e 3D se relacionam. A gradual aproximação das lamelas do Na-RUB-18 e conseqüente condensação dos grupos Si-OH, ou seja, unidades Q ([O4Si]3Si-OH), ocasiona a formação de ligações Si-O-Si, unidades Q ([O4Si]4-Si), gerando a estrutura 3D. No caso do zeólito MOR, esse processo é induzido pela adição de uma fonte de alumínio, Al[OCH(CH3)2]3 ou Na2Al2O4. O presente trabalho também investiga a etapa de aproximação das lamelas do Na-RUB-18, ocasionando na sua condensação em RUB-24. A condensação das lamelas do precursor lamelar no RUB-24 via processo topotático é conduzida por um agente direcionador de estrutura, o íon trietilenotetramônio, comprovando que tal processo, como a transformação hidrotérmica, não acontece aleatoriamente
Abstract: The application of the layered silicates in heterogeneous catalysis has limitations such as low surface area and acidity. However, these solids also have ion exchange capacity and their surfaces can be covalently modified with silylation reagents. As a result, they can undergo a variety of surface changes yielding modifications in interlayer space and in the structure lamellar that may even cause collapse of a 2D structure to a 3D. The framework of layered silicate Na-RUB-18 is composed of four five-membered rings, [5] and its surface made of Si-OH and Si-ONa. The [5] cage is a building unit also found in zeolitic structures, as RUB-24 and MOR, indicating that the structure of Na-RUB-18 contains important elements of microporous materials structures and should be regarded as a potential precursor structure to the three-dimensional four-connected microporous framework silicates. This work aimed of studying and describing the transformations of the Na-RUB-18 into MOR and RUB-24 by hydrothermal and topotactic process, respectively. The gradual reduction of interlayer distance of the Na-RUB-18 led to the condensation of the Si-OH groups, Q units ([O4Si]3Si-OH), forming Si-O-Si bonds, Q units ([O4Si]4-Si), i.e., a 3D structure. In the preparation of MOR zeolite by hydrothermal transformation, the process is conducted through addition of a aluminum source, Al[OCH(CH3)2]3 or Na2Al2O4. This work also investigated the formation of RUB-24 through Na-RUB-18 collapsing. The topotactic reaction between Si-OH groups of the lamellar precursor was conducted by a structure-directing agent, triethylenetetrammonium ion, proving that this process, as the hydrothermal transformation, does not occur randomly
Mestrado
Quimica Inorganica
Mestra em Química
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Kostova, Mariya Hristova. "Synthesis and characterization of new layered and microporous photoluminescent silicates." Doctoral thesis, Universidade de Aveiro, 2007. http://hdl.handle.net/10773/3190.
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Doutoramento em QuímicaEsta tese tem como principal objectivo a síntese, a caracterização estrutural e o estudo das propriedades de fotoluminescência de novos silicatos, lamelares e microporosos de terras raras. As técnicas de caracterização utilizadas foram a difracção de raios-X de pós e de mono-cristal, a microscopia electrónica de varrimento, as análises térmica e elementar, e as espectroscopias de fotoluminescência, ressonância magnética nuclear, Raman e infravermelho. Os silicatos de terras raras cristalinos foram obtidos por síntese hidrotérmica em condições de temperatura e pressão moderadas. Os silicatos lamelares AV-22, K3[(RE)Si3O8(OH)2], RE3+=Y3+, Eu3+, Er3+ ,Tb3+, Gd3+ e Ce3+ são sistemas hóspede-hospedeiro convenientes para criar materiais multifuncionais com um amplo leque de propriedades. A estrutura dos materiais AV-22 foi determinada por difracção de raios-X de mono-cristal. Os materiais Tb- e Eu-AV-22 são emissores de luz visível (verde e vermelho, respectivamente), com eficiências comparáveis à dos padrões usados em lâmpadas comerciais, enquanto que Er-AV-22 é um emissor de infravermelho, à temperatura ambiente. A incorporação de Ce3+ e Tb3+ no mesmo silicato lamelar cria um efectivo canal de transferência da energia do primeiro para o segundo. Após calcinação a 650 ºC, os materiais AV-22 sofrem uma transformação de fase, convertendo-se em uma estrutura de poros estreitos, conhecida como AV-23, K3[RESi3O9], RE3+=Y3+, Eu3+, Er3+ e Tb3+. O valor da radiância da amostra Tb-AV-23 é semelhante à do padrão (Gd2O2S:Tb) verde de Tb3+. O processo de calcinação aumenta a intensidade da emissão de Er3+ (essencialmente devido à remoção de grupos OH) e a importância das interacções Er3+-Er3+ como um mecanismo de extinção da fotoluminescência. Os silicatos microporosos AV-24, K7Ln3Si12O32⋅3H2O, Ln3+=Eu3+, Sm3+, Tb3+ e Gd3+ constituem o primeiro sistema que possui dímeros Ln-O-Ln isolados em uma matriz siliciosa, exibindo uma emissão característica: o tempo de vida do estado excitado 5D0 é notavelmente longo, ca. 10 ms a 10 K. A estrutura de todos estes silicatos admite a inclusão de um segundo (ou até mesmo um terceiro) tipo de ião Ln3+ na rede cristalina, permitindo um ajuste (muitas vezes fino) das propriedades de fotoluminescencia.
This thesis reports the synthesis, structural characterization and photoluminescence properties of new layered and microporous rare-earth silicates. These materials have been characterized by powder and single crystal Xray diffraction, scanning electron microscopy, thermal analysis, elemental analysis, nuclear magnetic resonance, infrared, Raman and photoluminescence spectroscopies. The crystalline rare-earth silicates were obtained by hydrothermal synthesis at moderate temperatures and pressures. Layered rare-earth silicates AV-22, K3[(RE)Si3O8(OH)2], RE3+=Y3+, Eu3+, Er3+ ,Tb3+, Gd3+ and Ce3+ are host-guest systems suitable for engineering multifunctional materials with tuneable properties. The structure of AV-22 was solved by single crystal X-ray diffraction. The Tb- and Eu-AV-22 samples are visible emitters (green and red, respectively) with output efficiency comparable to that of standards used in commercial lamps, while Er-AV-22 is a roomtemperature infrared phosphor. The incorporation of Ce3+ and Tb3+ in the same layered silicate induces and effective Ce3+ to Tb3+ energy transfer channel. Upon calcination at 650 ºC, AV-22 materials undergo a phase transformation to small-pore framework AV-23, K3[RESi3O9], RE3+=Y3+, Eu3+, Er3+ and Tb3+. The radiance values of Tb-AV-23 and standard Tb3+ green phosphors (Gd2O2S:Tb) are similar. The calcination process increases the intensity of the Er3+ emission (essentially due to the removing of OH groups) and the importance of the Er3+-Er3+ interactions as a quenching emission channel. Microporous lanthanide silicates AV-24, K7Ln3Si12O32⋅3H2O, Ln3+=Eu3+, Sm3+ ,Tb3+ and Gd3+ are the first reported to contain Ln-O-Ln dimmers isolated in a siliceous matrix and exhibiting a unique emission feature: the lifetime of the 5D0 excited state is remarkably long, ca. 10 ms at 10 K. The structure of all these silicates allows the inclusion of a second (or even third) type of Ln3+ ion in the framework and, therefore, the fine-tuning of their photoluminescence properties.
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Tang, Youhong. "Microrheological study on polyethylene/thermotropic liquid crystalline polymer/layered silicates nanocomposites /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CENG%202007%20TANG.
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Vamvounis, Emmanouil. "Polypropylene ternary nanocomposites with layered silicates and single-walled carbon nanotubes." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499936.
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Weiß, Stephan [Verfasser], and Axel H. E. [Akademischer Betreuer] Müller. "Hybrids Based on Layered Silicates / Stephan Weiß. Betreuer: Axel H. E. Müller." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/1059353024/34.
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Mingbunjerdsuk, Jirachai. "Organically-modified layered silicates as reinforcing fillers for natural and synthetic rubbers." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/33646.
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This research is concerned with the characterisation and properties of natural rubber (NR), styrene-butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) nanocomposites. The fillers used were unmodified sodium montmorillonite clay, three organically-modified clays with different types and concentrations of modifiers, and, for comparison, a carbon black. The clays were characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and x-ray diffraction (XRD). The composites were prepared via melt compounding and sulphur curing in an internal mixer. Better dispersion was found for the organoclays rather than for the unmodified clay as was seen by scanning electron microscopy (SEM). Intercalation and some exfoliation of certain organoclays in rubbers were achieved as revealed by XRD and transmission electron microscopy (TEM). The most polar rubber proved more effective in nanocomposite formation. The incorporation of organoclays affected torque and curing time as measured using a Monsanto rheometer. The organoclays can accelerate the vulcanization process, but the effect was reduced with increasing clay loading. The crosslink density decreased with increasing organoclay content. The static and dynamic mechanical properties of the rubber-layered silicate composites such as tensile properties, modulus, tear strength, fatigue life and dynamic visco-elastic properties are discussed. There was a significant improvement in modulus, tensile strength and elongation at break as compared to the composites prepared with the untreated clay. Dynamic mechanical analysis shows an increase in the storage and loss modulus for the nanocomposites. Overall, the content of clay and the type of modifier both affect the curing and mechanical properties. Rubber-organoclay nanocomposites show a good reinforcing effect which is comparable to that achieved with carbon black. In particular, the tear and fatigue properties of the organoclay-rubber nanocomposites exceeded those of the rubbers reinforced with carbon black.
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Benasutti, Patrick B. "Electronic and Structural Properties of Silicene and Graphene Layered Structures." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1348192958.
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