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1
Černohorský, Petr. „Elektrospřádaná vlákna na bázi PVDF a nylonu“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442506.
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Polymer nanofibers used for the construction of triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) are new and promising technologies for energy recovery. Thanks to the generation of electrical energy based on mechanical movement (deformation), these fibers can find application in the field of self-powered electronic devices. In this work, three nanofibrous structures of materials were prepared by electrostatic spinning: pure polyvinylidene fluoride (PVDF), pure polyamide-6 (PA6) and their mixed combination PVDF / PA6. Non-destructive analyzes such as Raman spectroscopy, FTIR, XPS and electron microscopy were used to study the properties of nanofibers. Analyzes confirmed the positive effect of electrostatic spinning of polymers on the support of the formation of highly polar crystalline -phase in PVDF and , -phase in PA6. The structure arrangement of the nanofibrous material and their defects were observed by scanning electron microscopy (SEM). Furthermore, the contact angle of the wettability of the liquid on the surface was measured for the materials, and the permittivity was measured to monitor the dielectric properties. The described results make the mixed material PVDF / PA6 very promising for further research in the field of nanogenerators and functional textiles.
2
Khan, Saima N. „Electrospinning Polymer Nanofibers-Electrical and Optical Characterization“. Ohio : Ohio University, 2007. http://www.ohiolink.edu/etd/view.cgi?ohiou1200600595.
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3
Bshena, Osama E. S. „Synthesis of permanent non-leaching antimicrobial polymer nanofibers“. Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20160.
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Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Antimicrobial fibers are very useful in various fields such as air and water purification, wound dressings and protective bandages, where sterile environments are essential. The nonwoven nanofiber mats or membranes are able to filter out microorganisms and potentially kill several threatening pathogenic bacteria. In this thesis, a variety of styrene-maleimide copolymer derivatives were prepared based on the modification of poly(styrene-co-maleic anhydride with various primary amine compounds. All prepared copolymer derivatives were electrospun to nanofiber mats using the needle electrospinning technique. For the characterization, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal properties of the electrospun fiber mats. Scanning electron microscopy (SEM) was carried out to observe fiber dimensions and morphology. The antibacterial activity of electrospun fiber mats was evaluated against different bacteria including Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative). The evaluation study utilized different tools to test for antibacterial activity and mode of cell death, including bioluminescent imaging, fluorescence imaging and the viable cell counting method. Excellent antimicrobial activity was obtained against the different strains especially against Staphylococcus aureus. Fiber mats containing tertiary amino groups, phenol or quaternary ammonium groups had the strongest antimicrobial properties.
AFRIKAANSE OPSOMMING: Antimikrobiese vesels is baie nuttig in verskeie toepassingsgebiede, soos lug- en watersuiwering, wondbedekkings en beskermende verbande, waar ‘n steriele omgewing noodsaaklik is. Die ongeweefde nanovesel matte of membrane is in staat om mikroorganismes te verwyder deur filtrasie, maar kan ook verskeie patogeniese bakterieë doodmaak. In hierdie proefskrif is ‘n verskeidenheid stireen-maleimied kopolimeer afgeleides gesintetiseer, gebaseer op die modifikasie van poli(stireen-ko-maleïne anhidried) met verskeie primêre amien verbindings. Nanovesel matte van al die gesintetiseerde kopolimeer afgeleides is gemaak deur gebruik te maak van die naald-elektrospin tegniek. Die termiese eienskappe van hierdie nanovesel matte is bestudeer deur gebruik te maak van differensiële skandeer kalorimetrie (DSK) en termogravitasie analiese (TGA) as karakteriseringsmetodes. Die vesel dimensies en morfologie is bestudeer deur skandeer elektronmikroskopie as karakteriseringsmetode te gebruik. Die antibakteriële aktiwiteit van die gespinde vesel matte is geëvalueer teen verskillende bakterieë, naamlik Staphylococcus aureus (Gram-positief), Escherichia coli en Pseudomonas aeruginosa (Gram-negatief). Die evalueringstudie het verskillende instrumente gebruik om vir antibakteriële aktiwiteit en meganisme van seldood te toets, insluitend bioluminiserings beelding, fluoressensie beelding en die lewensvatbare sel tellingsmetode. Uitstekende antimikrobiese aktiwiteit is verkry teen die verskillende rasse, veral teen Staphylococcus aureus. Vesel matte met tersiêre aminogroepe, fenol of kwaternêre ammoniumgroepe het die sterkste antimikrobiese eienskappe gehad.
4
Shin, Y. Michael (Young-Moon Michael) 1969. „Formation of polymer nanofibers from electrified fluid jets“. Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8848.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000.Includes bibliographical references (leaves 176-182).
The formation of polymer nanofibers from fluid jets in· an electric field, also referred to as electrospinning, has been studied. Controlling the fiber properties requires a detailed understanding of how a millimeter-diameter fluid jet emanating from a nozzle is transformed into solid fibers that are four orders of magnitude smaller in diameter. To this end, a fiber spinner operating under a uniform electric field and providing a controlled process environment was designed. In the conventional view of electrospinning, the mechanism leading to small fiber diameters has been attributed to the splaying phenomenon, in which a single jet splits into multiple smaller jets due to radial charge repulsion. Using high-speed photography and an aqueous solution of poly(ethylene oxide) as a model fluid, it was shown that the jet does not splay but instead undergoes a rapid whipping motion. The high whipping frequency created the optical artifact of multiple jets. The whipping jet was best observed in the onset region of the instability. Further downstream, the amplitude of the instability continued to grow, and the jet trajectory became more chaotic. This was verified through photography of the entire jet and close-up observations of representative regions further downstream. Based on these findings, an alternative mechanism for the formation of polymer nanofibers is proposed. It is conjectured that the whipping instability causes stretching and bending of the jet. The large reduction in jet diameter is achieved by increasing the path length over which the fluid jet is accelerated and stretched prior to solidification or deposition on a collector. Whipping induced stretching is conjectured to be the primary mechanism causing the jet diameter reduction. To provide a concise way of displaying the stability of electrified fluid jets as a function of the electric field and the flow rate, operating diagrams were developed. These diagrams delineate regions of different jet behavior, and the stability borders for two transitions have been mapped. The first transition is from dripping to a stable jet; and represents the suppression of the Rayleigh instability. For high conductivity fluids, an additional transition from a stable to a whipping jet can be observed at higher electric fields. The experimental findings are supported by a theoretical analysis of the jet thinning and the onset of the instability. To elucidate the fundamental electrohydrodynamics, glycerol was studied as a model fluid. Based on the experimental observation that whipping occurs on a length scale much larger than the jet radius, an asymptotic approximation of the electrohydrodynamic equations has been developed by Hohman and Brenner. This theory governs both long wavelength axisymmetric and non-axisymmetric distortions of the jet, and allows the jet stability to be evaluated as a function of all relevant fluid and process parameters. Three different instabilities are predicted: the classical Rayleigh instability, an axisymmetric conducting mode, and a non-axisymmetric conducting mode. The presence of these instabilities at various locations along the jet has been verified with high-speed video and photography. The particular instability that is observed depends on the jet shape and the surface charge density. To achieve quantitative agreement between experimental and theoretical jet profiles, the jet current and the local electric field in the vicinity of the nozzle had to be taken into account. The electric currents in stable jets were found to be linear in both the electric field and the flow rate Theoretical operating diagrams were developed based on the experimental insight that the instabilities are convective. The dependence of the stability borders on both the electric field and the flow rate is correctly reproduced by the Hohman-Brenner theory. This implies that operating diagrams have the potential to be used as predictive tools to better understand and control the process. The quantitative agreement between theory and experiments suggests that the fundamental process in electrospinning involves indeed a rapidly whipping jet, which is caused by the interaction of surface charges on the jet and the applied electric field. The notion of a whipping jet has also been extended to low viscosity fluids, where the jet disintegrates into fine droplets, i.e., electrospraying. For sufficiently large jet radii, experiments have verified the theoretical prediction that the dispersal of fluid results from the growth of a non-axisymmetric conducting mode along the jet, which subsequently breaks into droplets due to the axisymmetric conducting mode.
by Y. Michael Shin.
Ph.D.
5
Barzegar, Farshad. „Synthesis and characterization of Polymer/Graphene electrospun nanofibers“. Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/41188.
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Polymer nanofibers have attracted a lot of industrial interest in the past decade. In general, these
fibers need to be thermally stable for many applications, such as in the aerospace industry.
However, most of these polymer nanofibers suffer from low temperature degradation, limiting
their use in many potential applications. Graphene, which is one sheet of graphite, has unique
properties such as high conductivity, and high thermal stability. This exceptional material can be
incorporated into the polymer nanofibers as nanofillers in order to enhance their thermal
properties.
The aim of this dissertation is to investigate the effect of adding graphene nanofillers into the
polymer fiber on the resulting fibers’ thermal properties. For that purpose, polyvinyl alcohol
(PVA), a non-conductive polymer and a different source of graphene, namely graphene foam,
expendable graphite and graphite powder were used. The growth technique was the
electrospinning technique which offers a variety of parameters that need to be optimized. For this
includes, the amount of PVA in the water solvent, the flow rate, the applied voltage, the growth
time, and the tip/collector distance. In summary, it has been optimized that the best conditions
for growth of fibers will be as follows: PVA concentration will be fixed at 10 wt%, flow rate will
be 3 ml/h, applied voltage will be 30 kV, growth time of 60 s and tip/collector distance will be
fixed at 12 cm. The resulted PVA fibers from these conditions were smooth continuous and
hollow with diameter ranging between 190-340 nm, while PVA/graphene nano-fibers are much
thinner with diameter ranging between 132 - 235 nm when the same parameters were used with
only graphene concentration varied.
The fiber obtained with PVA showed a hollow structure which is desirable for incorporation of
graphene nanofillers. The dispersion of the different source of graphene sheets in the starting
PVA solution showed enhanced thermal stability compared to the PVA fibers alone.
Furthermore, an increase in the thermal stability is observed with increasing concentration of
graphene nanofillers. This work shows the promising use of graphene as nanofillers for PVA fibers. This can be
expended to other non-conductive and conductive polymers in order to broaden the application
of these fibers in the industries, where thermal stability is a prerequisite.Dissertation (MSc)--University of Pretoria, 2013.
gm2014
Physics
unrestricted
6
Kakade, Meghana Vasant. „Uniaxial orientation of polymer molecules via electrospinning“. Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 53 p, 2007. http://proquest.umi.com/pqdweb?did=1338927121&sid=11&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Qi, Zhigang. „Synthesis of conducting polymer colloids, hollow nanoparticles, and nanofibers“. Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40229.
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Colloidal polypyrrole and polyaniline stabilized by anionic surfactants were prepared and characterized. A "pseudo-micelle" model has been proposed. The aggregation of pseudo-micelles on the forming polymer chains is believed to be the key step in the stabilization process. Only when the aggregation is possible and fast enough to follow the polymer formation, will the polymer be stabilized.Colloidal polypyrrole and polyaniline were prepared in the presence of the sodium salt of poly(styrene sulfonate). The polymerization is believed to follow a template-guided fashion in which poly(styrene sulfonate) functions as a molecular template for pyrrole and aniline polymerization. The stability and water solubility of the colloids are attributed to the presence of excess poly(styrene sulfonate) sulfonate groups in the resulting complexes.
It was found that the chemical polymerization of pyrrole is catalyzed by anionic surfactants and polyelectrolytes. The catalysis is believed to arise from the accumulation of protons, neutral pyrrole monomer and oligomers, and their radical cations in the micellar or polyelectrolyte pseudophase via electrostatic and hydrophobic interactions. Nucleation was found to be a necessary and important step in the chemical polymerization of conducting polyaniline and polypyrole. A nucleation process has been proposed. A polyaniline-polypyrrole graft- or block-copolymer was produced by adding colloidal PANI to a similar amount of pyrrole.
Hollow conducting polypyrrole nanoparticles with diameters of ca. 140 nm or 60 nm and wall thicknesses of ca. 10 nm were fabricated. The shape and size of the hollow particles are determined by the core particles and the wall thickness is controlled by reaction conditions. A $ gamma$-Fe$ rm sb2O sb3$-polypyrrole composite possessing both magnetic and electrically conductive properties was also produced.
Polypyrrole and polyaniline nanofibers with highly uniform diameters between 10 and 50 nm were fabricated via the templating by lipid microstructures. The hydrophobic edges of the lipid microstructures function as the template. The polymer thickness is readily controlled by the polymerization time. Well-defined conducting polymer nano-rings were also produced.
Finally, the sensitivity enhancement of the electroanalysis of halides through the accumulation of trihalides in an overoxidized polypyrrole film was presented. This reveals a new method of using polymer-modified electrodes in electroanalysis, and we term the accumulation of a reaction product "product concentration".
8
Li, Pengfei. „Mechanical and Thermal Characterizations of Crystalline Polymer Micro/nanofibers“. Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/596.
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For crystalline polymers, especially those in micro/nanoscale, the number of defects per unit volume is significantly lower than that in the bulk. With extended and aligned polymer chains, the resulting polymer fibers possess remarkably enhanced mechanical and thermal properties and approach the inherent properties of the carbon backbones which form the polymer chains. Together with other unique properties of polymers, such as, low density, easy processability, good biocompatibility, and electrical insulation, the crystalline fibers in micro/nano scale can be used in a broad range of applications, for example, heat spreaders in electronics, high strength ropes, and personnel armors. This dissertation studies various schemes of polymer crystallization, especially the stress induced crystallization in fiber drawing process. In this work, a two-stage drawing method is finally adopted to produce individual polyethylene (PE) nanofibers. To demonstrate the PE nanofibers possess more enhanced mechanical properties than the commercially available PE nanofibers, an atomic force microscopy (AFM) based force deflection spectroscopy (FDS) technique is explored to characterize the Young's modulus of the PE nanofibers. By attaching a PE nanofiber onto a specially designed micro trench, and deflecting the nanofiber with an AFM cantilever, we are able to deduce the Young's modulus from the geometry of the trench and the level of deflection on the nanofiber based on Bernoulli's beam equations. The experimentally proved Young's modulus of these nanofibers is 312GPa approaching the theoretical limit of the Young's modulus of PE single crystal. To study thermal properties of a polysilsesquioxane (PSQ) hybrid crystal, we apply a micro device based thermal characterization method. The micro device consists of two suspended SiNx membranes with built-on Pt coils; the two membranes serve as heater and thermometer during the measurements. The PSQ micro beam is placed between the two membranes. Due to the Joule heating on the heating membrane, heat transfers through the sample to the sensing membrane. By analyzing the steady state heat transfer model, we are able to calculate the thermal conductivity of the PSQ beam. The experimentally measured thermal conductivities greatly help us to understand the heat transfer mechanism in the PSQ hybrid crystal which is formed by hydrogen bonding in the longitudinal direction. With the same characterization method as used in PSQ thermal characterization, we also measure the thermal conductivity of PE nanofibers. We discover the thermal contact resistance between the nanofiber and the islands is comparable or even bigger than the intrinsic thermal resistance of the PE nanofibers with an assumed thermal conductivity of 20W/mK at room temperature. Cyanoacrylate based super glue and focus ion beam (FIB) assisted Pt deposition are attempted to reduce the thermal contact resistance, however, as demonstrated by the experiments, super glue is likely to lift the nanofiber above the islands which dramatically increases the thermal resistance. While the FIB assisted Pt deposition introduces great crystal damage on the PE fibers, which results in very low measured thermal conductivities (<1W/mK).
9
Lin, Yinan. „Electrospinning Polymer Fibers for Design and Fabrication of New Materials“. University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1310997689.
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10
Calavalle, Francesco. „Electrospun polymer nanofibers for electromechanical transduction investigated by scanning probe microscopy“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13504/.
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Negli ultimi anni, il copolimero ferroelettrico P(VDF-TrFE), ha suscitato un grande interesse nella ricerca scientifica per le potenziali applicazioni elettroniche come ad esempio l’energy harvesting per la produzione di dispositivi indossabili e autoalimentabili, sensori biocompatibili e memorie non volatili. Molti sforzi si sono concentrati nello sviluppo di procedure di fabbricazione che possano migliorare le performance elettromeccaniche di questi materiali. Una delle soluzioni proposte è un processo chiamato elettrofilatura, una tecnica efficiente e a basso costo che sarebbe in grado di realizzare nanofibre polimeriche già polarizzate e pronte per l’integrazione nei dispositivi. Dalle analisi microscopiche svolte in questa tesi, utilizzando tecniche di microscopia a scansione di sonda, è stato scoperto che in realtà l’elettrofilatura non provoca polarizzazione nelle fibre, bensì induce un processo di iniezione di cariche all’interno del materiale che, se testato a livello macroscopico, mostra un’apparente risposta ferroelettrica dovuta però alle cariche intrappolate, come in un elettrete. Nonostante ciò, dopo la dissipazione delle cariche spaziali, ho potuto dimostrare, grazie al’implementazione della Switching Spectroscopy PFM ad alto potenziale, che le nanofibre elettrofilate possono essere polarizzate e mostrano proprietà piezoelettriche simili a quelle del film sottile. Quindi, inducendo la completa polarizzazione del network dopo la deposizione, è auspicabile un miglioramento delle proprietà elettromeccaniche dei dispositivi basati su nano-fibre elettrofilate.
11
Lee, Sungho. „Effect of carbon nanofibers on microstructure and properties of polymer nanocomposites“. Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202500308/.
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12
Rhodes, Christopher R. (Christopher Randolph). „Microfluidic flow-focusing device for the electrospinning of hollow polymer nanofibers“. Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36290.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 52-53).
Polymer nanofibers hold much promise as advanced composite materials, and can be customized into matrices with special electrical, optical and biological properties. Electrospinning, which utilizes the destabilization of a fluid's surface in a strong electric field, has gained the most favor as a top-down approach to producing polymer nanofibers. In this work, a microfluidic device was designed and assembled for the two-dimensional focusing of immiscible fluids and integrated into a system for electrospinning. Hollow fibers were produced with diameters on the order of 100-240 nm, at steady-state flow rates around 50 pL/min. TEM images show hollow interiors with diameters approximately one third of the total fiber diameter. These results are important for future efforts at multiplexing the electrospinning process, and prove that the creation of hollow fibers is feasible using a microfabricated device. Furthermore, the focusing of immiscible streams in two dimensions may be used for sample transport and reaction control in microfluidics. Suggestions are made for further evaluation of flow focusing behavior, and improvements that may increase the viability of electrospinning as an industrial process.
by Christopher R. Rhodes.
S.B.
13
He, Tianda. „Electrospun Nanofibers Patterning for Flexible Electronics“. University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1490199672185484.
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14
Chiou, Nan-Rong. „Aligned and oriented polyaniline nanofibers fabrication and applications /“. Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1148485692.
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15
Casper, Cheryl L. „Structure and properties of electrospun polymer fibers and applications in biomedical engineering“. Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 5.69 Mb., 165 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3200539.
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Presley, Kayla Fay. „Oxygen Sensing Electrospun Nanofibers for Biological Applications“. The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531616455684609.
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17
Cronje, Lizl. „Surface modification of styrene maleic anhydride nanofibers for efficient capture of Mycobacterium tuberculosis“. Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71923.
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Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Tuberculosis (TB) is a major cause of morbidity and mortality across the world, affecting adults and children. Children infected with TB differ from adults, as their immunological and patho-physiological response to the disease is different. Although there are a variety of tests available for TB diagnosis, they have limitations when used to diagnose paediatric TB. Children are also unable to generate sputum spontaneously when required for the use in culture or microscopy as diagnostic method. Children however do produce sputum, containing the TB bacilli, which they swallow. If the TB bacilli can therefore be retrieved from the stomach and tested, TB can be diagnosed using gastric samples. In this thesis, a variety of styrene maleimide copolymer (SMI) derivatives were prepared as potential M. tuberculosis-capturing platforms. This was done by modifying poly(styrene-co-maleic anhydride) (SMA) with a variety of primary amine compounds, selected based on possible chemical interactions with the M. tuberculosis cell wall. All the prepared copolymer derivatives were electrospun into nanofibrous mats using the single needle electrospinning technique to yield SMI nanofibers, functionalized with different compounds. Some of the functionalized SMI nanofibers were prepared by surface-functionalization of the polymer nanofibers after electrospinning and some by modification of the polymer before electrospinning. Affinity studies were conducted at neutral and low pH between the different functionalized SMI nanofibers and two mycobacterium strains, namely the bacillus Calmette-Guérin strain of Mycobacterium bovis (BCG) and M. tuberculosis, to evaluate the surfaces of the modified SMI nanofibers as mycobacterium-capturing platforms. The successful capture of BCG onto the surfaces of the various functionalized nanofibers was confirmed by SEM and fluorescence microscopy (FM). Analysis of the SEM and FM images indicated that the SMI nanofibers, functionalized with a C12 aliphatic quaternary ammonium moiety (SMI-qC12), captured BCG the most effectively through a combination of ionic and hydrophobic interaction. Concentration and time studies revealed that the extent of this interaction was dependent on incubation time and concentration of BCG. The affinity studies with BCG also concluded that the polymer used for the nanofibrous-capturing platform should not be too hydrophobic in character as this caused poor wetting of the functionalized nanofibers, thus preventing close contact with the mycobacteria and a reduction in the capture effectivity of the polymer nanofibers. The successful capture of M. tuberculosis onto the SMI-qC12 nanofibrous surface was confirmed by FM, light microscopy (LM) and polymerase chain reaction (PCR). The extent of this interaction was dependent on the concentration of M. tuberculosis. The detection of M. tuberculosis using FM and LM as detection methods was simplified by the tendency of M. tuberculosis to clump together in clusters on the hydrophobic surface of the SMI-qC12 nanofibers. As a result of this clustering, FM and LM were therefore regarded as feasible detection methods to image M. tuberculosis on the surface of the SMI-qC12 nanofibers, even at relatively low concentration of M. tuberculosis.
AFRIKAANSE OPSOMMING: Tuberkulose (TB) is 'n groot oorsaak van morbiditeit en mortaliteit regoor die wêreld en affekteer volwassenes en kinders. Kinders wat met TB geïnfekteer is, se immunologiese en patofisiologiese reaksie op die siekte verskil van die van volwassenes en dit het belangrike implikasies vir die diagnose van TB in kinders. Alhoewel daar 'n verskeidenheid van toetse beskikbaar is vir die diagnose van TB, het hulle beperkings wanneer dit gebruik word om pediatriese TB te diagnoseer. Kinders kan ook nie spontaan sputum produseer as dit nodig is vir die gebruik in kultuur of mikroskopie as diagnostiese metode. Kinders produseer egter wel sputum, wat die TB basille bevat, wat hulle dan insluk. As die TB basille uit die maag versamel kan word en getoets kan word, kan TB gediagnoseer word met behulp van maag monsters. In hierdie tesis is 'n verskeidenheid van stireen maleimied kopolimeer (SMI) afgeleides voorberei as potensiële Mycobacterium tuberkulose (Mtb)-vaslegging platforms. Dit is gedoen deur die modifikasie van poli(stireen-ko-maleïen anhidried) (SMA) met 'n verskeidenheid primêre amien verbindings as oppervlak-funksionaliseringsagente. Hierdie primêre amien verbindings is gekies op grond van moontlike chemiese interaksies met die Mtb selwand. Al die voorbereide kopolimeer afgeleides is elektrogespin in nanoveselagtige matte met behulp van die enkel-naald elektrospin tegniek om SMI nanovesels te lewer wat gefunksionaliseer is met verskillende verbindings. Sommige van die gefunksionaliseerde SMI nanovesels is berei deur oppervlak-funksionalisering van die polimeer nanovesels na elektrospin, en sommige deur die modifikasie van die polimeer voor elektrospin. Affiniteitstudies is uitgevoer, by neutrale en lae pH, tussen die verskillende gefunksionaliseerde SMI nanovesels en twee mikobakterium rasse, naamlik die basillus Calmette-Guérin ras van Mycobacterium bovis (BCG) en M. tuberculosis, om die oppervlaktes van die gewysigde SMI nanovesels te evalueer as mikobakterium-vaslegging platforms. Ontleding van die SEM en FM beelde het aangedui dat die SMI nanovesels, gefunksionaliseer met 'n C12 alifatiese kwaternêre ammonium groep (SMI-qC12), BCG die doeltreffendste vasgevang het deur 'n kombinasie van ioniese en hidrofobiese interaksie. Konsentrasie- en tydstudies tussen BCG en SMI-qC12 het aangedui dat die omvang van hierdie interaksie afhanklik is van inkubasietyd en konsentrasie van BCG. Die affiniteitstudies met BCG het ook aangedui dat die polimeer wat gebruik word vir die nanoveselagtige-vaslegging platform nie te hidrofobiese moet wees nie, aangesien dit swak benatting van die gefunksionaliseerde nanovesels veroorsaak, en dus noue kontak met die mikobakterieë voorkom met ʼn gevolglike vermindering in die vasvang-effektiwiteit van die polimeer nanovesels. Die suksesvolle vasvang van M. tuberculosis op die SMI-qC12 nanovesels is bevestig deur FM, lig mikroskopie (LM) en polimerase kettingreaksie (PKR). Die opsporing van Mtb deur die gebruik van FM en LM as opsporingmetodes is vergemaklik deur die tendens van Mtb om in groepies saam te pak op die hidrofobiese oppervlak van die SMI-qC12 nanovesels. As gevolg van hierdie groepering, is FM en LM dus haalbare opsporingmetodes om M. tuberculosis op die oppervlak van die SMI-qC12 nanovesels waar te neem, selfs by relatief lae konsentrasie van M. tuberculosis.
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Liu, Jing. „Carbon nanotube/polymer composites and novel micro- and nano-structured electrospun polymer materials“. Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22673.
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Thesis (Ph. D.)--Textile and Fiber Engineering, Georgia Institute of Technology, 2007.Committee Chair: Kumar, Satish; Committee Member: Carr, Wallace; Committee Member: Graham, Samuel; Committee Member: Griffin, Anselm; Committee Member: Yao, Donggang.
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LIU, XIAOXIAO. „A Preliminary Study on Water Collection Ability of Nanofibers Derived from Electrospun Polymers“. University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1573050761831223.
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Swart, Morne. „Synthesis and characterization of electrospun organic-inorganic hybrid graft copolymer nanofibers of poly(methyl methacrylate) and polydimethylsiloxane“. Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/718.
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Sandler, Jan K. W. „Structure-property-relationships of carbon nanotubes/nanofibres and their polymer composites“. Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615300.
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Rhodes, Susan M. „Electrically Conductive Polymer Composites“. University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1194556747.
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Wu, Jie. „Extraction of chitin nanofibers and utilization for sustainable composites and foams“. Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54006.
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Developing renewable materials to reduce the dependence on fossil fuel as a feedstock for a wide range of applications is becoming increasingly acknowledged as important in society. Chitin, the second most abundant biopolymer in nature, is an ideal candidate for diverse applications because of its remarkable properties, such as abundance, renewability, biodegradability, biocompatibility, antibacterial activity, chemical functionality, and high stiffness and strength. Despite these inherent advantages, chitin is currently still underutilized mainly due to its strong molecular interactions, which make it insoluble in common solvents. Currently, its major applications are limited to biomedical engineering, such as tissue engineering, wound dressing and sutures.
This thesis aims to explore and enable the potential utilization of chitin in other fields where it may serve as a renewable functional advanced material. Here, a number of novel chitin-based materials were developed successfully without employing chitin dissolution. These include chitin nanofibers (CNFs), porous chitin with tunable structures, chitin-reinforced polymer composites and chitin-stabilized aqueous foams. Moreover, the properties of these materials including interfacial, optical, thermal, and mechanical characteristics were determined, and their potential utilizations were demonstrated.
Briefly, in chapter 2, CNFs with diameters of ~20 nm were successfully extracted from crab α-chitin by a high pressure homogenization process. The produced CNFs were dispersed well in water without forming strong network structures due to their electrostatic repulsions. The obtained CNF film has a high residue amount (40%) when heated up to 1000 ˚C. Meanwhile, it exhibited high optical transparency as well as great gas barrier properties. In chapter 3, on the basis of the obtained CNFs in chapter 2, versatile porous structures including oriented sheets and three-dimensional aperiodic nanofiber networks were achieved by using a freeze drying technique. Since the formation of nanofibrous structures cannot be predicted by the widely-used particle encapsulation model, a modified structure formation mechanism was proposed. In chapter 4, the structure-property relationships of the CNF/poly(ethylene oxide)(PEO) nanocomposites were established. We demonstrated that the CNFs formed network structures in PEO matrix and had hydrogen bonding interaction with PEO. The CNFs can greatly enhance the mechanical properties of PEO, such as elastic modulus and tensile strength. In chapter 5, the aqueous foams stabilized by high-aspect-ratio CNFs were developed. The created foams exhibited strong hindrance on film drainage, coalescence and disproportionation. The fibrillated CNFs alone were not able to stabilize air bubbles, but the addition of small amounts of valeric acids in CNF dispersion can make chitin foamable. The results clearly showed that valeric acid modified CNFs reduced the surface tension of aqueous dispersion and were attached at the air-water interface.
Overall, this research has provided many new insights for the fabrication, characterization, and utilization of chitin, and has built a solid foundation for further exploiting chitin for diverse applications.
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Jacobs, Nokwindla Valencia. „Optimising the polymer solutions and process parameters in the electrospinning of Chitosan“. Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1010762.
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Electrospinning is a technique, which can be used to produce nanofibrous materials by introducing electrostatic fields into the polymer solution. Due to their intrinsic properties, such as small fiber diameter, small pore size and large surface area, nanofibres are suitable for use in a variety of applications including wound dressing, filtration, composites and tissue engineering. The study demonstrates the successful and optimised production of Poly(ethylene oxide) (PEO) and chitosan nanofibres by electrospinning. The biocidal effects of chitosan, chitosan-silver nanofibres and silver nanoparticles were successfully investigated. To set up a functional electrospinning apparatus, the PEO solution parameters (concentration, molecular weight, solvent, and addition of polyelectrolyte) and applied potential voltage on the structural morphology and diameter of PEO nanofibres were studied. At lower PEO concentrations, the fibres had morphology with a large variation in fibre diameter, whereas at the higher concentrations, the nanofibres exhibited ordinary morphology with uniform but larger fibre diameters. Higher molecular weight showed larger average diameters when compared to that obtained with the same polymer but of a lower molecular weight. The addition of polyelectrolyte to the polymer solution had an influence on the structural morphology of the PEO. Flow simulation studies of an electrically charged polymer solution showed that an increase in the flow rate was associated with an increase in poly(allylamine hydrochloride) (PAH) concentration for the low molecular weight polymer, the shape and size of the Taylor cone increasing with an increase in PAH concentration for the low molecular weight polymer. During optimization of the PEO nanofibres, based on statistical modelling and using the Box and Behnken factorial design, the interaction effect between PAH concentration and the tip-to-collector distance played the most significant role in obtaining uniform diameter of nanofibres, followed by the interaction between the tip-to-collector distance and the applied voltage and lastly by the applied voltage. The production and optimization of chitosan nanofibres indicated that the interactions between electric field strength and the ratio of trifluoroacetic acid (TFA) and dichloromethane (DCM), TFA/DCM solvents as well as between electric field strength and chitosan concentration had the most significant effect, followed by the concentration of chitosan in terms of producing nanofibres with uniform diameters. Chitosan and chitosan-silver nanofibres could be successfully electrospun by controlling the solution properties, such as surface tension and electrical conductivity with the silver nanoparticles in the chitosan solutions affecting the electrospinnability. The silver nanoparticles in the chitosan solution modified the morphological characteristics of the electrospun nanofibres, while the conductivity and the surface tension were elevated. The fibre diameter of the chitosan and chitosan-silver nanoparticles decreased with an increase in the silver content. The electrospun chitosan nanofibres had a smooth surface and round shape as compared to the silver-chitosan nanofibres with a distorted morphology. The chitosan and chitosan-silver nanofibres as well as the silver nanoparticles exhibited antimicrobial or inhibition activity against S. aureus than against E. coli. S. aureus bacterial culture showed good cell adhesion and spreading inwards into the chitosan nanofibrous membrane. The chitosan-silver nanofibres exhibited a greater minimum inhibitory concentration (MIC), followed by silver nanoparticles and then chitosan nanofibres; suggesting a synergistic effect between the chitosan and silver nanoparticles.
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Adetunji, Oludurotimi Oluwaseun. „The nature of electronic states in conducting polymer nano-networks“. Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1206218304.
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Ondigo, Dezzline Adhiambo. „Polymer based electrospun nanofibers as diagnostic probes for the detection of toxic metal ions in water“. Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1018261.
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The thesis presents the development of polymer based electrospun nanofibers as diagnostic probes for the selective detection of toxic metal ions in water. Through modification of the chemical characteristics of nanofibers by pre- and post-electrospinning treatments, three different diagnostic probes were successfully developed. These were the fluorescent pyridylazo-2-naphthol-poly(acrylic acid) nanofiber probe, the colorimetric probe based on glutathione-stabilized silver/copper alloy nanoparticles and the colorimetric probe based on 2-(2’-Pyridyl)-imidazole functionalized nanofibers. The probes were characterized by Fourier transform infrared spectroscopy (FTIR), Energy dispersive x-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The fluorescent nanofiber probe was developed towards the determination of Ni²⁺. Covalently functionalized pyridylazo-2-naphthol-poly(acrylic acid) polymeric nanofibers were employed. The solid state Ni²⁺ probe exhibited a good correlation between the fluorescence intensity and nickel concentration up to 1.0 mg/mL based on the Stern-Volmer mechanism. The detection limit of the nanofiber probe was found to be 0.07 ng/mL. The versatility of the fluorescent probe was demonstrated by affording a simple, rapid and selective detection of Ni²⁺ in the presence of other competing metal ions by direct analysis without employing any sample handling steps. For the second part of the study, a simple strategy based on the in-situ synthesis of the glutathione stabilized silver/copper alloy nanoparticles (Ag/Cu alloy NPs) in nylon 6 provided a fast procedure for fabricating a colorimetric probe for the detection of Ni²⁺ in water samples. The electrospun nanofiber composites responded to Ni²⁺ ions but did not suffer any interference from the other metal ions. The effect of Ni²⁺ concentration on the nanocomposite fibers was considered and the “eye-ball” limit of detection was found to be 5.8 μg/mL. Lastly, the third probe was developed by covalently linking an imidazole derivative; 2-(2′-Pyridyl)-imidazole (PIMH) to Poly(vinylbenzyl chloride) (PVBC) and nylon 6 nanofibers by post-electrospinning treatments using a wet chemical method and graft copolymerization technique, respectively. The post-electrospinning modifications of the nanofibers were achieved without altering their fibrous morphology. The color change to red-orange in the presence of Fe²⁺ for both the grafted nylon 6 (white) and the chemically modified PVBC (yellow) nanofibers was instantaneous. The developed diagnostic probes exhibited the desired selectivity towards the targeted metal ions.
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Devadas, Suchitha. „Fabrication of Lignin-Based Nanofibers: Influence of Lignin Type, Blend Ratios, and Total Polymer Concentration“. University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton160831003121355.
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Pringle, Carla. „Single bubble-electrospinning of polyvinyl alcohol and polyacrylonitrile“. Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/18009.
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Thesis (MSc)--Stellenbosch University, 2011.ENGLISH ABSTRACT: Needle-electrospinning is an uncomplicated and highly versatile nanofiber (fiber diameter of 50 to 500 nm) production technique. Nevertheless the process can only produce 0.01 to 1.0 g/h/m2 of nanofibers, unpractical for large-scale productions. Bubble-electrospinning, in the presence of surfactants, is a novel nanofiber mass-production technique developed at Stellenbosch University.[1] The technique is similar to needle-electrospinning only that the surface area of a bubble surpasses that of a solution droplet, making it possible for multiple jets to form on the bubble surface at high field strengths. Thus far little research has been done on the influence of solution properties on the bubble-electrospinning technique. During electrospinning the solution experiences three competing forces, namely, surface tension (contracting force), charge repulsion (expanding force), and viscosity (resistance to flow). The first aim of this study was to obtain better understanding on the influence of three significant solution properties (viscosity, conductivity and surface tension) on bubble-electrospinning in terms of bubble lifetime, bubble size, average number of jets and the resultant fibers. The solution properties were varied using a range of polymer and surfactant concentrations. A second aim was to obtain better understanding on the comparison of the bubble-electrospinning process between two polymer solutions, namely Polyvinyl alcohol (PVOH) solutions containing sodium lauryl ether sulphate (SLES) surfactant, and Polyacrylonitrile (PAN) solutions containing silicone surfactant. Results indicated that the solution viscosity and conductivity increased with increasing polymer concentrations for both polymer solutions. In addition, both the solution surface tensions were not influenced by polymer concentration. With regards to bubble-electrospinning of PVOH solutions, results indicated that the average number of jets per bubble was influenced by the polymer concentration. Regarding PAN solutions, bubble lifetime and the average number of jets was influenced by polymer concentration. Results indicated that the solution viscosity increased and surface tension decreased with increasing surfactant concentration for both polymer solutions. PVOH solution conductivity increased whilst PAN solution conductivity decreased with increasing surfactant concentrations. With regards to bubble-electrospinning of PVOH solutions, the bubble lifetime and bubble size was significantly influenced by the SLES concentration. Regarding PAN solutions, the silicone surfactant concentration had no significant effect on the bubble-electrospinning process. Overall, PVOH fiber diameters decreased with increasing surfactant concentration. There was no common trend between the bubble-electrospinning of PVOH and PAN solutions in relation to their solution properties. It was concluded that solution viscosity, conductivity and surface tension are not the only significant contributing parameters to the bubble-electrospinning process.
AFRIKAANSE OPSOMMING: Die naald-elektrospinproses is 'n eenvoudige, hoogsaanpasbare tegniek wat gebruik word vir die maak van nanovesels. Nanovesels het tipies 'n deursnee van 50nm tot 500nm. Ongelukkig is dit onprakties vir grootskaalse produksie omdat die uitset daarvan beperk is tot 0.01 tot 1.0 g/h/m2. Die borrel-elektrospinproses, waar elektrospinstrale gespin word vanaf die oppervlak van borrels op die oppervlak van die spinoplossing en waar die borrels gestabiliseer is m.b.v. sepe, is 'n nuwe tegniek wat ontwikkel is by die Universiteit van Stellenbosch. [1]. Die tegniek is soortgelyk aan die naald-elektrospinproses in dié sin dat die elektrospinstraal vorm vanaf 'n gelaaide halfsfeervormige oppervlak in die spinoplossing, maar die aansienlik groter oppervlakarea van die borrel in die borrel-elektrospinproses maak dit moontlik om verskeie elektrospinstrale gelyktydig op die oppervlak van die borrel te onderhou. Dit lei tot baie hoër doeltreffendheid in die saamgroeppering van die strale en gevolglik tot hoër nanoveseluitsette. Tot dusver is daar weinig navorsing aangaande die invloed van oplossingseienskappe op die borrel- elektrospintegniek gedoen. Tydens die elektrospinproses ervaar die oplossing drie kompeterende kragte, naamlik: oppervlakspanning (sametrekkende krag), elektrostatiese afstoting (afstotende krag) en viskositeit (vertragende effek op vloei van die oplossing). Die hoofdoelwit van hierdie navorsing was om 'n beter begrip te kry van die invloed van drie gemete oplossingswaardes, d.w.s. viskositeit, elektriese geleidingsvermoë en oppervlakspanning op die borrel-elektrospinproses. Die impak van hierde waardes is spesifiek geëvalueer in terme van borrellewensduur, borrelgrootte, gemiddelde hoeveelheid elektrospinstrale per borrel en die morfologie van die vesels wat in die proses gevorm is. Die tweede doelwit van die studie was om 'n vergelyking te tref tussen die mees optimale oplossingswaardes in die borrel-elektrospinproses van twee baie uiteenlopende polimeerspinoplossings, naamlik polivinielalkohol (PVOH), met natrium dodesieletersulfaat (SLES) as die borrelstabiliserende seep en poliakrilonitriel (PAN) oplossing, met 'n silikoonseep as die borrelstabiliserende seep. Resultate het getoon dat die viskositeit en elektriese geleidingsvermoë toeneem met toename in polimeerkonsentrasie vir beide PVOH- en PAN-oplossings. Verder is oppervlakspanning in beide gevalle nie beduidend beïnvloed deur die polimeerkonsentrasie nie. In die geval van die borrel-elektrospin van die PVOH-oplossings het resultate daarop gedui dat die gemiddelde aantal elektrospinstrale per borrel moontlik beïnvloed kon word deur die polimeerkonsentrasie. In die geval van borrel-elektrospin van PAN-oplossing is bevind dat polimeerkonsentrasie die borrelleeftyd en die gemiddelde aantal elektrospinstrale per borrel beïnvloed. Resultate het ook getoon dat die viskositeit vermeerder en die oppervlakspanning afneem met toename in die konsentrasie van die sepe in beide die polimeeroplossings. Die PVOH-oplossing se elektriese geleidingsvermoë het vermeerder terwyl dit verminder in die geval van die PAN-oplossings met 'n toename in die seepkonsentrasie. Tydens borrel-elektrospin van die PVOH-oplossings is beide borrelleeftyd en borrelgrootte beduidend beïnvloed deur die SLES konsentrasie. By die borrel-elektrospin van PAN-oplossings het die silikoonseepkonsentrasie nie 'n beduidende invloed gehad op die borrelleeftyd en borrelgrootte nie. Oor die algemeen het die gemiddelde PVOH veseldeursnee afgeneem met toename in seepkonsentrasie. Geen algemene tendens kon waargeneem word tussen die optimale oplossingswaardes vir borrel-elektrospin van die PVOH- en die PAN-oplossings onderskeidelik nie. Die gevolgtrekking is dat die viskositeit, elektriese geleidingsvermoë en oppervlakspanning nie die enigste beduidende waardes is wat bepaal of die borrel-elektrospinproses sal werk vir 'n spesifieke polimeeroplossing nie.
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Ghochaghi, Negar. „EXPERIMENTAL DEVELOPMENT OF ADVANCED AIR FILTRATION MEDIA BASED ON ELECTROSPUN POLYMER FIBERS“. VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3631.
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Electrospinning is a process by which polymer fibers can be produced using an electrostatically driven fluid jet. Electrospun fibers can be produced at the micro- or nano-scale and are, therefore, very promising for air filtration applications. However, because electrospun fibers are electrically charged, it is difficult to control the morphology of filtration media. Fiber size, alignment and uniformity are very important factors that affect filter performance. The focus of this project is to understand the relationship between filter morphology and performance and to develop new methods to create filtration media with optimum morphology.
This study is divided into three focus areas: unimodal and bimodal microscale fibrous media with aligned, orthogonal and random fiber orientations; unimodal and bimodal nanoscale fibers in random orientations; bimodal micrometer and nanometer fiber media with orthogonally aligned orientations. The results indicate that the most efficient filters, which are those with the highest ratio of particle collection efficiency divided by pressure drop, can be obtained through fabricating filters in orthogonal layers of aligned fibers with two different fiber diameters. Moreover, our results show that increasing the number of layers increases the performance of orthogonally layered fibers. Also, controlling fiber spacing in orthogonally layered micrometer fiber media can be an alternative way to study the filtration performance. Finally, such coatings presented throughout this research study can be designed and placed up-stream, down-stream, and/or in between conventional filters.
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Movva, Siva Subramanyam. „Effects of Carbon Nanoparticles on Properties of Thermoset Polymer Systems“. The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281996658.
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Benavides, Rafael Esteban. „Gas Jet Process for Production of Sub-micron Fibers“. University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1365991608.
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Kumar, Rishi. „Manufacturing of High Performance Polymer Nanocomposites Containing Carbon Nanotubes And Carbon Nanofibers Using Ultrasound Assisted Extrusion Process“. University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1291639408.
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Smit, Eugene A. „Studies towards high-throughput production of nanofiber yarns“. Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/4785.
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Thesis (PhD)--Stellenbosch University, 2008.ENGLISH ABSTRACT: Electrospinning is a simple yet versatile method used for producing nanofibers from various materials, including natural and synthetic polymers, polymer blends, ceramics and metals. The high specific surface areas, high aspect ratios (length/diameter), and the biomimicking nature of nanofibers make them ideally suited for application in diverse areas, including high-performance filtration, biomedical materials for tissue engineering scaffolds, wound dressings and controlled drug release, fiber-reinforced composites and highly sensitive nano-sensors. Two of the main requirements that need to be met for electrospun nanofiber materials to become commercially viable are: (1) a process for manufacturing continuous aligned nanofiber yarns, and (2) a drastic increase in the fiber production rate of the electrospinning process. The objectives of this study were to develop a scalable process for making continuous yarns of aligned electrospun nanofibers, and to develop a needleless electrospinning method for the high-throughput production of nanofibers. Three novel processes were developed while exploring innovative ways for making yarns from electrospun fibers. Finally, a fourth process, the so-called the NanoCaterpillar process, was developed. This process can be used as a scalable method for obtaining continuous yarns of aligned nanofibers. Advantages of the process include the requirement for relatively simple equipment, the simple process variations required for obtaining yarns of different linear densities, and the fact that, as a 'dry' process, it can be used to manufacture yarns from most materials that can be electrospun. The second goal of this study was to develop a needle-less electrospinning process, capable of making nanofibers at commercially viable throughput rates. The phenomenon of bubble electrospinning was discovered and developed further. Initial exploratory studies showed that bubble electrospinning could be employed to produce nanofibers from polymers in aqueous as well as organic solutions, and that the process follows similar trends to classic electrospinning such as the dependence of fiber diameter on polymer solution concentration and the possibility of including substances in the formed fibers by including them in the spin solution. A second, more in-depth study of the bubble electrospinning process revealed that fibers could be produced at very high rates with estimates, under ideal spinning conditions, reaching 5 kg/h per square meter of bubble bath surface. Furthermore it was found that fiber yield did not depend on the size or the lifetime per bubble. Investigations into several interesting aspects of bubble and jet behaviour during bubble electrospinning, such as child bubble formation and jet-splitting, led to predictive multiple linear regression models being fitted to the experimental data to describe process variables like yield per bubble, number of jets per bubble and fiber diameters.
AFRIKAANSE OPSOMMING: Die elektrospintegniek is 'n eenvoudige, dog veelsydige metode wat gebruik word om nanovesels van verskeie materiale, insluitend natuurlike en sintetiese polimere, polimeermengsels, keramieke, en ook metale te vervaardig. Die hoë spesifieke oppervlakareas, hoë lengte tot deursnee verhoudings en bio-naboodsende eienskappe van nanovesels maak hulle ideaalgeskik vir toepassing in uiteenlopende velde soos filtrasie, biomediese materiale vir weefselingenieurswese, wondbedekkings en beheerde vrystelling van geneesmiddels, veselversterkte saamgestelde materiale en hoogs-sensitiewe nanosensors. Twee van die hoofvereistes waaraan voldoen moet word, voordat elektrogespinde nanovesels kommersieël-lewensvatbaar kan word, is: (1) 'n proses vir die vervaardiging van kontinuë garings van gerigte nanovesels, en (2) 'n drastiese toename in die vervaardigingstempo van die elektrospinproses. Die doelwitte van hierdie studie was om 'n skalleerbare proses te ontwikkel vir die vervaardiging van kontinuë garings van gerigte nanovesels, en om 'n naaldlose elektrospinmetode te ontwikkel vir die hoë-uitset vervaardiging van nanovesels. Drie nuwe prosesse is ontwikkel tydens ondersoeke na innoverende maniere om garings van elektrogespinde nanovesels te vervaardig. Laastelik is 'n vierde proses, die sogenaamde NanoCaterpillar proses ontwikkel. Hierdie proses kan gebruik word as 'n skalleerbare metode vir die vervaardiging van kontinuë garings van gerigte nanovesels. Voordele van die proses sluit in dat relatief eenvoudige toerusting benodig word om die konsep toe te pas, dat slegs eenvoudige veranderinge aan die proses benodig word om garings van verskillende liniêre digthede te verkry, en dat die proses, synde 'n 'droë' proses, gebruik kan word om garings te maak van meeste materiale wat gespin kan word met die elektrospintegniek. Die tweede doelwit van hierdie studie was om 'n naaldlose elektrospinproses te ontwikkel wat nanovesels kon vervaardig teen kommersieël-lewensvatbare tempo's. Die borrelelektrospin verskynsel is ontdek en verder ontwikkel. Aanvanklike ondersoeke het getoon dat die borrelelektrospinproses gebruik kon word om nanovesels te vervaardig van polimere in water- sowel as organiese oplossings. Dit het ook getoon dat die proses soortgelyke tendense toon as die klassieke elektrospintegniek, soos die afhanklikheid van veseldeursnee aan polimeeroplossingkonsentrasie en die moontlikheid om ander stowwe in die gevormde vesels in te sluit deur dit aanvanklik in die spinoplossing in te sluit. 'n Verdere indiepte ondersoek van die borrelelektrospinproses het onthul dat vesels, onder geïdealiseerde omstandighede, vervaardig kon word teen baie hoë tempo's, na beraming 5 kg/h per vierkante meter borrelbadoppervlakarea. Verder is bevind dat die veselopbrengs nie afhanklik was van die borrelgrootte of -lewensduur nie. Ondersoeke na verskillende aspekte van die borrel- en polimeerstraalgedrag tydens die borrelelektrospinproses, soos die vorming van kind-borrels en polimeerstraalsplitsing, het gelei tot die passing van voorspellende meerfoudige liniêre regressiemodelle op die eksperimentele data, ten einde prosesveranderlikes soos opbrengs per borrel, aantal polimeerstrale, en vesels deursnee te kan beskryf.
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Sadzevičius, Vilius. „Kai kurių polimerų laidumo tyrimas diferencinių voltamperinių charakteristikų metodu“. Master's thesis, Lithuanian Academic Libraries Network (LABT), 2006. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2006~D_20060615_104319-43417.
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Polymers, typically known, as plastics, long time were only insulators. In 1977 D.J. Heeger, A.G. Diarmid ir H. Shirakawa discovered a new type of this organic material – conductive polymers. Conductive polymers have a unique property of high electrical conductivity, where the electronic structure of polymer chains plays essential role.
In this work we theoretically investigate conductive organic materials. Conductance of this materials is the result of charge carriers tunnelling. Tunnelling is a temperature-dependent process due to the interaction of electrons with phonons (phonon – kvaziparticle describing the periodical motion of cristal atoms). The basic quantum-mechanical theory what helps us to interpret the experimental results – phonon-assisted tunnelling theory. Experimental results were taken from other authors papers. In this theory is assumed that tunnelling rate depends on both – temperature and field.
All the calculations were taken in Mathematica 5.0. Programs made in this algebrical system helped us to fit experimentical and theoretical data. It let us to describe tunnelling rate variating parameters.
The main attention was taken to investigate how some of this parameters change tunnelling rate (W) and estimate parameters of polyacetylene and carbon nanotubes (CNT). This materials were taken because of it`s unique properties. Polyacetylene can become very good conductor by it`s doping. Carbon is one of the most abundant ellements in the Earth crust. It... [to full text]
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Jimenez, Guillermo Alfonso. „Characterization of Poly(Methyl Methacrylate) and Thermoplastic Polyurethane-Carbon Nanofiber Composites Produced by Chaotic Mixing“. University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1166105818.
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Meltz, Freda-Jean. „Amphiphilic electrospun fibres of poly(methacrylic acid)-graft-poly(dimethylsiloxane) copolymers as a means to controlling electrospun fibre morphology and obtaining nanofibre hydrogels“. Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86620.
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Thesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Novel poly(methacrylic acid)-graft-poly(dimethylsiloxane) copolymers were synthesised by conventional free radical reactions using a poly(dimethylsiloxane) macromonomer. The polymers were electrospun to investigate how the fibre morphology can be modified by manipulating the electrospinning solution parameters, and to determine the possibility of using the polymers as new materials for the production of polymer nanofibre hydrogels. The electrospinning solution parameters were varied by electrospinning the highly amphiphilic copolymers in solvents with variable solvent qualities. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FE–SEM) was used to investigate the fibre morphology. Internal morphology was studied using a freeze fracture technique prior to FE-SEM imaging. It is revealed that the polymers in this study does not form any fine structure or pores even when self-assembled structures are present in the solution. Attempts were made to visualise any self-assembled structures of films produced from dilute solutions using TEM. Further studies included investigating the fibres properties, primarily with regards to their rate and extent of moisture and water uptake. The fibres showed hydrogel behaviour and the PDMS content were found to have an impact on the hydrogel stability. Post electrospinning crosslinking of the nanofibres was also explored.
AFRIKAANSE OPSOMMING: Unieke ent-kopolimere wat bestaan uit poli(metielakrielsuur) (PMAS) en poli(dimetielsiloksaan) (PDMS) is gesintetiseer deur middel van 'n “ent-deur” vryeradikaalkopolimerisasie. 'n PDMS makromonomeer is vir hierdie doel gebruik. Die polimere is geëlektrospin om vesels te vorm. Die doel was om die invloed van verkillende strukture in oplossing op die veselmorfologie te bepaal. Die moontlikheid om hierdie nanovesels as gels te gebruik is ook ondersoek. Die amfifiliese kopolimere is geëlektrospin uit die oplossing waarin dit wisselende oplosbaarheid toon. Skandeer elektron mikroskopie (SEM) is gebruik om die morfologie te ondersoek. Die interne morfologie van die vesels is ondersoek deur die vesels te vries en in die gevriesde toestand te breek. Die studie het getoon dat geen strukture op, of binne, die vesels vorm nie, selfs al moes daar assosiasie tussen segmente van die polimere gewees het. Hierdie tipe assosiasies sou strukture in die oplossing tot gevolg gehad het. 'n Poging is aangewend om die strukture in oplossing te visualiseer deur transmissie elektron mikroskopie (TEM) van dun films te ondersoek. Films is vanaf verdunde oplossings gevorm. Ander studies het ingesluit om die eienskappe van die vesels te ondersoek, met die fokus op hoeveel en hoe vinnig die vesels waterdamp en water kon absorbeer. Die vesels het soos 'n gel reageer. Hierdie gedrag is beïnvloed deur die hoeveelheid PDMS wat 'n definitiewe invloed op die stabiliteit van die gel gehad het. Kruisverbindings van die vesels, nadat dit geëlektrospin is, is ook ondersoek.
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Rao, Vivek S. „Collection of highly aligned electrostrictive graft elastomer nanofibers using electrospinning in a vacuum environment“. Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1636.
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Park, ChangKyoo. „Development of Precise Femtosecond Laser Micromachining Processes for Metals and Electrospun Nanofibers“. The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437690070.
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Gissentaner, Tremaine D. „Development of Conductive Green Polymer Nano-Composite for use in Construction of Transportation Infrastructure“. Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1408697877.
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Kamarsu, Prasanth R. „Towards Developing a Technique to Produce Nanocomposites with Uniform Auxetic Behavior“. University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1310136514.
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Rubio, Martínez Marta. „Coordination polymer nanofibers made of amino acids and peptides and their use as templates to synthesize inorganic nanoparticle superstructures“. Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/283949.
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La present Tesi Doctoral s'ha dedicat a explorar les capacitats de coordinació d’aminoàcids i pèptids per tal de desenvolupar nous Polimers de Coordinació (PCs) en forma de nanofibres a escala nanoemetrica, i poder utilitzar-los com a (doble) plantilla per la síntesi de superestructures fetes amb nanopartícules inorgàniques (INPs). Utilitzar PC en forma de nanofibres com a doble plantilla té l’avantatge de poder aprofitar tant les propietats de plantilla com les característiques inherents de reconeixement dels pèptids per tal de formar CPs.
En el primer capítol es mostra una breu introducció als PC, centrant-se en l’ús de biomolècules. Aquest capítol inclou el treball titulat "Metal–biomolecule frameworks (MBioFs)", Chem. Commun (2011), on es fa una estesa i detallada descripció sobre aquests tipus de materials. A continuació, els objectius generals d'aquesta tesi es descriuen en el capítol 2.
El Capítol 3 resumeix els resultats reportats en "Amino acid-based metal-organic nanofibers", J. Am. Chem. Soc. (2009). Aquí, es mostra la síntesi i caracterització de nanofibres de CP i gels construïts a partir de la coordinació d'amino àcids (L-o àcid D-aspàrtic, Asp) i ions metàl · lics (Cu (II) ions). Les nanofibres quirals de Cu(II)-Asp resultants s’han sintetitzat utilitzant tècniques de precipitació ràpida i de difusió lenta, amb les quals la longitud d’aquestes pot arribar fins a 1 centímetre.
En el capítol 4, les nanofibres de Cu(II)-Asp s'han utilitzat com a cas-escenari de prova per explorar la tècnica de microfluídica (més precisament flux laminar) com a nou mètode sintètic per tal d'aconseguir un control més precís sobre l’assamblatge d'ions metàl·lics amb AA. S’ha demostrat que, a diferència dels procediments sintètics comuns, aquesta aproximació permet la síntesi en paral·lel amb un eminent nivell sobre el control de la coordinació, facilitant la formació de 1-D PC ensamblats a escala nanomètrica. A més de les nanofibres de Cu(II)-Asp, l’ús de la microfluidica ha permès la síntesis d’un segon tipus de nanofibres fetes amb aminoàcids, Ag(I)-Cisteina (Cys). S’ha confirmat que aquestes nanoestructures no es poden obtenir amb mètodes tradicionals com el de la precipitació ràpida dels dos components. Aquests resultats s'inclouen en el manuscrit "Coordination polymer nanofibers generated by microfluidic synthesis", J. Am. Chem. Soc. (2011).
En un següent pas, el capítol 5 es centra en l'ús de les nanofibres de Ag (I)-Cys com a plantilles per tal de sintetitzar i acoblar NP inorgàniques en superestructures 1-D. En aquest capítol, primer es motra la síntesi de NPs de Ag2S ensamblades en 1-D exposant les nanofibres de Ag(I)-Cys sota un bombardeig d'electrons. A continuació, es mostra que aquestes plantilles sintetitzadades poden localitzar-se en posicions precises mitjançant la tecnologia de la microfluidica amb la incorporació de vàlvules de fluids microfabricades incorporades. La microfluídica permet orientar i localitzar la formació de les nanofibres de Ag (I)-Cys i a més, l'ús de vàlvules permet la immobilització de les fibres i poder utilitzar-les com a plantilles per a la síntesis de 1-D superestructures de NPs deAg. Aquestes superestructures s'han sintetitzat mitjançant la reducció (àcid ascòrbic) dels ions de Ag(I) que es troben dins de la plantilla. El nivell de control assolit amb la microfluídica ha permès que es puguin utilitzar més a fons aquestes superestructures de Ag NP com a segones plantilles per sintetitzar cristalls conductors de Ag (I)-tetracyanoquinodinmethane (TCNQ), permetent a més la mesura directe de les seves propietats de conductivitat. Tots aquests resultats estan inclosos en l'article presentat en el capítol 4 i en l'article titulat "Localized template growth of functional nanofibers from an metal-amino acid-supported framework in a microfluidic chip", ACS Nano 2014.
Finalment, en el capítol 6, s'ha incrementat la complexitat dels PCs de Ag(I) fets a partir d'aminoàcids amb pèptids per tal d’explotar les característiques inherents de reconeixement que tenen els pèptids. S'ha sintetitzat una nova classe de plantilles metall-pèptid, cristalls de Ag(I)-DLL similars a cintes, amb els quals s'ha demostrat que poden ser utilitzats com a doble plantilla per a la síntesi i assamblatge de dos tipus de NPs inorgàniques, unes sobre la seva superfície (cara del cristall) i les altres dins de les seves estructures internes. En aquestes plantilles, les capacitats d'auto-assamblatge i reconeixement dels pèptids, i la reducció selectiva dels ions Ag(I) a Ag s'han explotat simultàniament per tal de controlar el creixement i l'assamblatge de més complexos multicomposicionals de superestructures amb NP inorgàniques. S'ha demostrat que aquests cinturons Ag(I)-DLL poden ser utilitzats com a dobles plantilles per crear llargues (> 100 µm) i polimetàl·liques superestructures conductores de Ag@AgNP i compostos multifuncionals de NPs de Fe3O4@Ag combinant les propietats magnètiques i conductores dels dos tipus de NPs. Aquests resultats han estat reportats en el manuscrit titulat "“Dual-template” Synthesis of one-dimensional conductive NP superstructures from coordination metal-peptide polymer crystals", Small (2013).The present PhD Thesis has been dedicated to explore the coordination capabilities of amino acids and peptides to create novel nanoscale Coordination Polymers (CPs) in the form of nanofibers, and to use these nanofibers as (dual) scaffolds for the synthesis of superstructures made of inorganic nanoparticles (INPs). The use of CP nanofibers as dual scaffolds has taken advantage of the templating characteristics of CPs as well as the inherent recognition-template characteristics of the peptide that has been used to form the CP. In the first Chapter, we show a brief introduction to CPs, focusing on those constructed from biomolecules. This Chapter includes the review entitled "Metal–biomolecule frameworks (MBioFs)", Chem. Commun (2011), in which an extended, detailed description of this type of materials was reported. Then, the general objectives of this Thesis are described in Chapter 2. Chapter 3 summarizes the results reported in "Amino acid-based metal-organic nanofibers", J. Am. Chem. Soc.(2009). Here, we show the synthesis and characterization of CP nanofibers and gels built up from the coordination of amino acids (L- or D-aspartic acid, Asp) and metal ions (Cu(II) ions). The resulting chiral Cu(II)-Asp nanofibers have been synthesized using fast precipitation and slow diffusion techniques, from which their lenght could be extended up to 1 centimeter. In Chapter 4, Cu(II)-Asp nanofibers have been used as the test-case-scenario to explore microfluidics technology (more precisely, laminar flow) as a new synthetic approach to achieve precise control over the assembly of metal ions and amino acids. We have demonstrated that unlike common synthetic procedures, this approach enables parallel synthesis with an unprecedented level of control over the coordination pathway and facilitates the formation of 1D CP assemblies at the nanometer length scale. In addition to Cu(II)-Asp nanofibers, the use of microfluidics has allowed the synthesis of a second type of CP nanofibers made of amino acids Ag(I)-Cysteine (Cys) nanofibers. We have also confirmed that these nanostructures can not be synthesized with more traditional methods, such as fast mixing of both components. All these results are included in the manuscript entitled "Coordination polymer nanofibers generated by microfluidic synthesis", J. Am. Chem. Soc. (2011). In a next step, Chapter 5 focuses on the use of the Ag(I)-Cys nanofibers as templates to synthesize and assemble inorganic NPs into 1D superstructures. In this Chapter, we first show the synthesis of 1-D assemblies of Ag2S NPs by exposing the Ag(I)-Cys nanofibers to e-beam bombardment. We then show that this template synthesis can be localized at precise positions by using microfluidic technology with micro-engineered fluidic clamps incorporated. Microfluidics allows guiding and localizing the formation of Ag(I)-Cys nanofibers, whereas the use of clamps allows immobilizing these fibers and use them as templates to synthesize 1-D Ag NP superstructures. These superstructures have been synthesized via reduction (ascorbic acid) of the Ag(I) ions inside the scaffold structure. We anticipate that the level of control achieved with microfluidics has allowed us to further use these Ag NP superstructures as second templates to synthesize conductive Ag(I)-tetracyanoquinodinmethane (TCNQ) CP crystals, allowing also the direct measurement of their conductivity properties. All these results are included in the article presented in Chapter 4 and in the article entitled "Localized template growth of functional nanofibers from an metal-amino acid-supported framework in a microfluidic chip", ACS Nano 2014. Finally, in Chapter 6, we have increased the complexity of the Ag(I)-based CP from amino acids to peptides to exploit the inherent recognition-template characteristics of peptides. Here, we have synthesized a new class of metal-peptide scaffolds, Ag(I)-DLL belt-like crystals, that were proved to be used as dual-templates for the synthesis and assembly of two types of inorganic NPs, one on their surface (crystal face) and the other within their internal structures. In these CP scaffolds, the self-assembly and recognition capacities of peptides and the selective reduction of Ag(I) ions to Ag are simultaneously exploited to control the growth and assembly of more complex, multicompositional inorganic NP superstructures. We demonstrate that these Ag(I)-DLL belts could be applied as dual templates to create long (> 100 μm) conductive Ag@Ag NP superstructures and polymetallic, multifunctional Fe3O4@Ag NP composites that marry the magnetic and conductive properties of the two NP types. These results have been reported in the manuscript entitled "“Dual-template” Synthesis of one-dimensional conductive NP superstructures from coordination metal-peptide polymer crystals", Small (2013).
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Biber, Erkan. „Production And Characterization Of Nanofibers From Polycaprolactam And Ethylene-butyl Acrylate-maleic Anhydride Terpolymer Mixture“. Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611870/index.pdf.
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The impact strength of Nylon 6 was improved by adding Ethylene- n-Butyl acrylate- maleic anhydride (E-nBA-MAH) terpolymer with various concentrations from 0% (w/w) to 15% (w/w). The bare interaction energy between two polymers was investigated by using melting point depression approach utilizing both the Flory-Huggins (FH) theory and the Sanchez-Lacombe Equation of State (SL EOS).
The solution of the mixture was electrospun, and the effects of process parameters on the expected radii of nanofibers were investigated. The effects of process parameters such as polymer concentration in solution, electrical field, diameter of syringe needle, feed rate, and collector geometry on nanofibers were studied. The statistical analysis to relate these parameters on the diameter of nanofibers was carried out by using Johnson SB distribution.
The ratio of elastic modulus to viscosity coefficient of nanofibers was worked out by using AFM and combined viscoelastic models. The experiments were carried out on single fiber. The ratio came out to be a function of nanofiber diameter and terpolymer concentration.
Isothermal crystallization kinetics and WAXS diffraction patterns of blends revealed and also SEM images supported that after 5% addition of elastomeric terpolymer, the interaction between the components of the blend gets weaker. The elastic modulus of the blend with 5% of terpoymer was greater than that of the neat Nylon 6, but the elastic modulus decreased for the blends containing more than 5% terpolymer.
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Gois, Bruno Henrique de Santana. „Desenvolvimento e caracterização de nanofibras condutoras de poli(álcool vinílico) com poli(3,4-etilenodioxitiofeno):poli(estireno sulfonado) (PVA/PEDO:PSS) e polipirrol (PVA/PPy), obtidas por eletrofiação para aplicação em sensores /“. Bauru, 2020. http://hdl.handle.net/11449/192496.
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Orientador: Deuber Lincon da Silva AgostiniResumo: Neste trabalho foram produzidas nanofibras eletrofiadas constituídas de poli(álcool vinílico) (PVA) com poli(3,4-etilenodioxitiofeno):poli(estireno sulfonado) (PEDOT:PSS) (PVA/PEDOT:PSS) e nanofibras de poli(álcool vinílico) (PVA) com polipirrol (PPy) (PVA/PPy) com propriedades elétricas para utilização como sensores de gás. O PVA é um polímero isolante, solúvel em água com elevado peso molecular que lhe confere as características ideais para a produção de nanofibras, sendo este usado como polímero de suporte para os polímeros condutores PEDOT:PSS e PPy. Foram investigados o efeito das diferentes concentrações de PVA na produção das nanofibras eletrofiadas, onde a concentração de 6% apresentou os melhores resultados na formação de nanofibras. Também foram investigados a influência das concentrações de PEDOT:PSS e PPy na estrutura e propriedades das nanofibras eletrofiadas, através da análise morfológica e resistividade elétrica, no qual obteve-se a formação de nanofibras para todas as concentrações. Em seguida as nanofibras foram depositadas em eletrodos interdigitados para a realização das caracterizações elétricas e teste como sensor de gás, no qual comprovou-se a sensibilidade das nanofibras constituídas de condutor/isolante na presença de gás amônia (NH3).
Abstract: In this work were produced electrospunnanofibers of polyvinyl alcohol (PVA) with poly(3,4-ethylenedioxythiophene):poly(sulfonated styrene) (PEDOT:PSS) (PVA/PEDOT:PSS) and poly(vinyl alcohol) nanofibers (PVA) with polypyrrole (PPy) (PVA/PPy) with electrical properties for use as gas sensors. PVA is a high molecular weight water soluble insulating polymer which gives it the ideal characteristics for the production of nanofiber, which is used as a support polymer for the PEDOT:PSS and PPy conductive polymers. It wasinvestigated the effect of different PVA concentrations on the production of electrospunnanofibers, where the 6% concentration showed the best results in the formation of nanofibers. The influence of PEDOT:PSS and PPy concentrations on the structure and properties of nanofibers was also investigated, through morphological analysis and electrical resistivity, which obtained the formation of nanofibers for all concentrations. Then the nanofibers were deposited on interdigitated electrodes to perform the electrical characterization and test as a gas sensor, which proved the sensitivity of conductor / insulating nanofibers in the presence of ammonia gas (NH3).
Mestre
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Batlokwa, Bareki Shima. „Development of molecularly imprinted polymer based solid phase extraction sorbents for the selective cleanup of food and pharmaceutical residue samples“. Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1004967.
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This thesis presents the development of chlorophyll, cholic acid, aflatoxin B1 molecularly imprinted polymer (MIP) particles and cholic acid MIP nanofibers for application as selective solid phase extraction (SPE) sorbents. The particles were prepared by bulk polymerization and the nanofibers by a novel approach combining molecular imprinting and electrospinning technology. The AFB1 MIP particles were compared with an aflatoxin specific immunoextraction sorbent in cleaning-up and pre-concentrating aflatoxins from nut extracts. They both recorded high extraction efficiencies (EEs) of > 97 % in selectively extracting the aflatoxins (AFB1, AFB2, AFG1 and AFG2). High reproducibility marked by the low %RSDs of < 1% and low LODs of ≤ 0.02 ng/g were calculated in all cases. The LODs were within the monitoring requirements of the European Commission. The results were validated with a peanut butter certified reference material. The chlorophyll MIP on the other hand selectively removed chlorophyll that would otherwise interfere during pesticide residue analysis (PRA) from > 0.6 to <0.09 Au in green plants extracts. The extracted chlorophyll was removed to far below the level of ≥ 0.399 Au that is usually associated with interference during PRA. Furthermore, the MIP demonstrated better selectivity by removing only chlorophyll (> 99%) in the presence of planar pesticides than the currently employed graphitized carbon black (GCB) that removed both the chlorophyll (> 88%) and planar pesticides (> 89%). For the interfering cholic acid during drug residue analysis, cholic acid MIP electrospun nanofibers demonstrated to be more sensitive and possessing higher loading capacity than the MIP particles. 100% cholic acid was removed by the nanofibers from standard solutions relative to 80% by the particles. This showed that the nanofibers have better performance than the micro particles and as such have potential to replace the particle based SPE sorbents that are currently in use. All the templates were optimally removed from the prepared MIPs by employing a novel pressurized hot water extraction template removal method that was used for the first time in this thesis. The method employed only water, an environmentally friendly solvent to remove templates to ≥ 99.6% with template residual bleeding of ≤ 0.02%.
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GHOSH, MONOJ. „Fabrication of Inorganic Oxide Nanofibers Using Gas Jet Fiber Spinning Process and Their Applications in Photocatalytic Oxidation“. University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1478726324293037.
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Jayanty, Sharmila. „Negative Poisson’s Ratio Composites - Finite Element Modeling and Experiments“. University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1290137957.
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Bedford, Nicholas M. „Electrospun Fibers for Energy, Electronic, and Environmental Applications“. University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321299420.
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Fogelström, Linda. „Polymer Nanocomposites in Thin Film Applications“. Doctoral thesis, KTH, Ytbehandlingsteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12400.
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The introduction of a nanoscopic reinforcing phase to a polymer matrix offers great possibilities of obtaining improved properties, enabling applications outside the boundaries of traditional composites. The majority of the work in this thesis has been devoted to polymer/clay nanocomposites in coating applications, using the hydroxyl-functional hyperbranched polyester Boltorn® as matrix and montmorillonite clay as nanofiller. Nanocomposites with a high degree of exfoliation were readily prepared using the straightforward solution-intercalation method with water as solvent. Hard and scratch-resistant coatings with preserved flexibility and transparency were obtained, and acrylate functionalization of Boltorn® rendered a UV-curable system with similar property improvements. In order to elucidate the effect of the dendritic architecture on the exfoliation process, a comparative study on the hyperbranched polyester Boltorn® and a linear analogue of this polymer was performed. X-ray diffraction and transmission electron microscopy confirmed the superior efficiency of the hyperbranched polymer in the preparation of this type of nanocomposites. Additionally, an objective of this thesis was to investigate how cellulose nanofibers can be utilized in high performance polymer nanocomposites. A reactive cellulose “nanopaper” template was combined with a hydrophilic hyperbranched thermoset matrix, resulting in a unique nanocomposite with significantly enhanced properties. Moreover, in order to fully utilize the great potential of cellulose nanofibers as reinforcement in hydrophobic polymer matrices, the hydrophilic surface of cellulose needs to be modified in order to improve the compatibility. For this, a grafting-from approach was explored, using ring-opening polymerization of ε-caprolactone (CL) from microfibrillated cellulose (MFC), resulting in PCL-modified MFC. It was found that the hydrophobicity of the cellulose surfaces increased with longer graft lengths, and that polymer grafting rendered a smoother surface morphology. Subsequently, PCL-grafted MFC film/PCL film bilayer laminates were prepared in order to investigate the interfacial adhesion. Peel tests demonstrated a gradual increase in the interfacial adhesion with increasing graft lengths.QC20100621
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Yang, Xiaojiao. „Synthesis and Characterization of Hybrid Metal-Metallic Oxide Composite Nanofibers by Electrospinning and Their Applications“. Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1022/document.
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Nous présentons dans ce manuscrit l'élaboration par électrofilage (ES) de nanofibres hybrides métal/oxyde métallique (HMMOC) et leurs caractérisations physico-chimiques. Leurs utilisations dans le cadre d’applications de type « énergie » et « environnement » ont été évaluées. En particulier, la photocatalyse de nanofibres TiO2-Au pour la dégradation en solution aqueuse du bleu de méthylène et l’utilisation de nanofibres WO3-Au comme capteurs de gaz (VOCs) ont été examinées. En lien étroit avec les résultats obtenus sur l'évaluation des performances comme photocatalyseurs ou capteurs à gaz de ces nouvelles structures HMMOC, l'influence de nombreux paramètres a été étudiée : la concentration en ions aurique, la méthode utilisée pour introduire ces derniers à l’intérieur ou les déposer à la surface des nanofibres d’oxydes et finalement le traitement thermique. En effet, on peut soit mélanger directement, avant la procédure d’électrofilage, la solution contenant les ions aurique à la solution polymérique (composée de PVP, PAN, ou PVA contenant le précurseur d'oxyde métallique), soit déposer sous forme de goutte cette solution d’ions Au à la surface des nanofibres d’oxyde métallique une fois la procédure d’électrofilage effectuée. Quant au traitement thermique, il joue un rôle multiple puisqu’il permet à la fois, d’éliminer les composés organiques des solutions polymériques, participant ainsi à la structuration de la partie oxyde du HMMOC, mais aussi de réduire les ions Au sous forme de nanoparticules.Des résultats prometteurs en photocatalyse ont été obtenus sur des fibres optimisées de TiO2 contenant des nanoparticules d’Au de 10 nm (concentration en Au : 4 wt%). En effet, pour cet échantillon, on montre une dégradation 3 fois plus rapide du bleu de méthylène en solution aqueuse que celle obtenue sur les nanofibres de TiO2 de références et sur le catalyseur commercial P25. De la même manière, des nanofibres de WO3 décorées de nanoparticules d’Au de 10 nm, utilisées comme capteurs de gaz, permettent d’obtenir une réponse 60 fois plus importante que dans le cas de nanofibres de WO3 pure et en améliorant grandement la sélectivité par rapport au n-butanolWe present in this manuscript the elaboration by Electrospinning (ES) process of hybrid metal-metallic oxide composite (HMMOC) nanofibers (NFs), and their physical-chemical characterizations. Their applications, especially the photocatalysis of TiO2-Au composite NFs for photocatalytic degradation for methylene blue (MB) in an aqueous solution and WO3-Au composite NFs for gas sensing of the volatile organic compounds (VOCs) have been investigated. According to the performance evaluation results as photocatalyst or gas sensors, the influence of many parameters have been studied: gold ions concentration, the way to introduce them into or at the NFs surface, typically by mixing them into the polymeric solution (composed of PVP, PAN, or PVA with the metallic oxide precursor) before the ES process or by simple droplet deposition onto the NFs after ES process, and finally the annealing treatment. This latter plays an important role since it both removes the organic components of the polymeric solution, thus forming the metal oxide and in-situ participates to the Au reduction.Concerning the photocatalytic properties, an optimized HMMOC material based on TiO2 NFs including 10 nm Au nanoparticles (NPs) has been obtained and shows 3 times significantly improvement of MB degradation compared to pure TiO2 NFs and the commercial catalyst P25. For gas sensing elaboration, we have shown that a HMMOC material based on WO3 NFs decorated at their surface with 10 nm Au NPs can exhibit 60 times higher response and significantly improved selectivity toward n-butanol compared with pure WO3 NFs
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Subir, Kumar Biswas. „Optically Transparent Nanocellulose-Reinforced Composites via Pickering Emulsification“. Kyoto University, 2019. http://hdl.handle.net/2433/244562.
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