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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Solvent Effects And Ionic Interactions In Polyaniline Systems

Ghosh, Soumyadeb 05 1900 (has links) (PDF)
No description available.
22

Conductive Polymers Derived Heteroatom Doped Carbon Catalysts forOxygen Reduction Reaction

Honorato, Ana Maria Borges 22 January 2021 (has links)
No description available.
23

Formation Mechanism and Thermoelectric Energy Conversion of Titanium Dioxide Nanotube Based Multi-Component Materials and Structures

Su, Lusheng 25 November 2013 (has links)
No description available.
24

Design and development of advanced electro-active clay/polymer hybrid materials for environmental applications

Kiari, Mohamed 07 March 2023 (has links)
La hibridación de minerales arcillosos con polímeros conductores recibe gran interés por diferentes aplicaciones potenciales, incluida la remediación ambiental. Esta tesis contiene tres partes del estudio, en primer lugar, estudia y compara las propiedades electroquímicas de dos arcillas diferentes, montmorillonita (Mont) y diatomita (Diat), y sus respectivos materiales híbridos arcilla/PEDOT-PSS en medio H2SO4. Los materiales híbridos se prepararon por electropolimerización de EDOT en presencia de PSS. Se analizaron las propiedades físico-químicas y electroquímicas de ambas arcillas mediante diferentes técnicas, y se investigó la influencia de las propiedades de la arcilla en la electropolimerización y la electroactividad de los híbridos arcilla/PEDOT-PSS resultantes. En concreto, la sonda redox Fe2+/Fe3+ y la oxidación de diclofenaco, como contaminante emergente farmacéutico modelo, se utilizaron para probar la capacidad de transferencia de electrones y la respuesta oxidativa, respectivamente, de los híbridos arcilla/PEDOT-PSS. Los resultados demuestran que, a pesar de su baja conductividad eléctrica, el Mont es un material electroactivo en sí mismo con una buena capacidad de transferencia de electrones. Por el contrario, el Diat no muestra electroactividad. La hibridación con PEDOT generalmente mejora la electroactividad de las arcillas, pero las propiedades de la arcilla afectan la eficiencia de electropolimerización y la electroactividad de los híbridos, por lo que Mont/PEDOT muestra propiedades electroquímicas mejoradas. Se demuestra que los híbridos de arcilla/PEDOT-PSS exhiben capacidad de oxidación de diclofenaco y sensibilidad a la concentración de diclofenaco. Se sintetizaron diferentes materiales híbridos a base de arcilla en un solo paso mediante polimerización química de EDOT en presencia de la arcilla sin o con nanofibras de carbono (CNF). Estos materiales fueron caracterizados con diferentes técnicas y estudiados por su potencial aplicación en la remoción de diclofenac y Radium, contaminantes emergentes modelo, del agua. Para ello se analizó la termodinámica y cinética de adsorción de diclofenaco y radio sobre los diferentes materiales. En el caso del Diclofenaco, los resultados obtenidos indican que el método de síntesis propuesto permite producir fácilmente los materiales híbridos con rendimientos del 80 - 90 %. La caracterización de estos materiales muestra que la estructura mesoporosa y alta área superficial (ca. 250 m2/g) de la arcilla no se ve afectada de forma notable por su combinación con PEDOT y/o los CNFs. La termogravimetría indica que se han obtenido materiales híbridos con alrededor del 10 % en peso de PEDOT sin y con 4 y 8 % en peso de CNF. La combinación de SEM con XPS y FTIR señala que PEDOT se ha cultivado con éxito alrededor de partículas de arcilla. La comparación de las isotermas de adsorción de diclofenaco indica que la hibridación con PEDOT mejora en gran medida la capacidad de adsorción de la arcilla. La adsorción de la isoterma resultante muestra la adsorción más alta con CNF y Clay/PEDOT con 340 mg/g y 220 mg/g respectivamente. Los datos de equilibrio se aplicaron a dos modelos de isoterma, y los resultados obtenidos sugirieron que la adsorción se siguió mejor con el modelo de Langmuir para Clay/PEDOT y Clay, con una capacidad máxima de adsorción de monocapa de 227,01 mg/g y 20,44 mg/g respectivamente. Por el contrario, fueron mejor ajustados por el modelo de Freundlich para el resto de los materiales, indicando adsorción heterogénea y la posibilidad de formación de multicapas en estos casos. Los datos cinéticos obtenidos para la adsorción se ajustaron mejor a una ecuación de velocidad de pseudo segundo orden para todos los materiales, con una capacidad máxima de adsorción en equilibrio de 18,24 mg/g para Clay/PEDOT. Este hallazgo sugiere que la adsorción se estaba produciendo a través del mecanismo químico. En el caso del Radio, se sintetizaron diferentes materiales híbridos a base de arcilla en un solo paso mediante polimerización química de EDOT y anilina en presencia de arcilla sin o con nanofibras de carbono (CNF). Estos materiales fueron caracterizados con diferentes técnicas y estudiados por su potencial aplicación en la remoción de radio del agua. Para este propósito, se utilizó una muestra de salmuera, recolectada de la salida de la mina subterránea, para probar la remoción de radio. El estudio que se realizó y se detalla en el documento muestra una gran eficacia en la eliminación de radio de las muestras de agua. La característica de los materiales se realizó mediante XRD, TG, FE-SEM, fluorescencia de rayos X y análisis de adsorción-desorción de N2. Los experimentos demostraron que arcilla/PEDOT, arcilla/PEDOT/10 % CNF y arcilla/PANI tienen una eficiencia de eliminación de radio significativamente menor. El uso de arcilla y arcilla que ha sido alterada químicamente por polímeros y nanofibras de carbono es una forma potencial de eliminar el radio del agua. El uso de un material híbrido a base de arcilla es una opción potencial para eliminar el radio del agua. El estudio realizado y detallado en el documento examinó una variedad de nanofibras de carbono y polímeros a base de arcilla (PEDOT, PANI), ya que algunos de ellos muestran una gran eficacia para eliminar el radio de las muestras de agua. La característica de los materiales se realizó mediante XRD, TG, FE-SEM, fluorescencia de rayos X y análisis de adsorción-desorción de N2. Para las pruebas de remoción de radio, se utilizó una muestra de salmuera, recolectada de la salida de una mina subterránea. Los experimentos demostraron que arcilla/PEDOT, arcilla/PEDOT/10 % CNF y arcilla/PANI tienen una eficiencia de eliminación de radio significativamente menor.
25

The Investigation of Inorganic Co Based ReRAM Devices and Organic Cu Doped PANI-CSA Top Electrode Based ReRAM Devices

Li, Yanlong January 2020 (has links)
Recently, the resistance switching random access memory (ReRAM) in several MIM systems has been studied extensively for applications to the next generation non-volatile memory (NVM) devices and memristors since the scaling of conventional memories based on floating gate MOSFETs is getting increasingly difficult. ReRAM is being considered one of the most promising candidates for next generation non-volatile memory due to its relatively high switching speed, superior scalability, low power consumption, good retention and simple fabrication method. Cu/TaOX/Pt resistive switching device is a very good candidate due to its well performance and well characterization. However, since platinum (Pt) acting as the inert electrode is not economical efficient for industrial production, a compatible replacement of Pt is highly desirable. The device property of Co based resistive switching devices has been explored in this work. Compared with Pt devices, electric characterization of the fabricated Cu/TaOX/Co devices exhibits very similar FORM, SET and RESET voltages for Cu conductive filaments. However, for the oxygen vacancy (VO) filament the Co device has a significant smaller FORM, SET and RESET voltages of VO filament, which can be partly attributed to the work function difference between Pt and Co of 1.35 V and partly to the impaired integrity properties of Co vs Pt inert electrode. The limit of SET-RESET operations is mainly due to the geometrical shape of the Cu conductive filament is more cylindered rather than Cone-like shape as well as the high Joules heat dissipation. What’s more, ReRAM is also the most promising candidate for a flexible memory, as a variety of materials can be used both inorganics, organics and even hybrid nanocomposites. Besides inorganic ReRAM device, we also fabricated an organic ReRAM device with the structure Cu doped PANI-CSA/O-AA/Al. We have manufactured ReRAM based on Cu-doped PANI-CSA polymer electrode, O-AA as the polymer solid electrolyte and Al as the bottom electrode for the first time. This polymer device shows a significantly lower forming voltage than inorganic ReRAM devices such as Cu/TaOX/Pt. Our results also demonstrate that our organic ReRAM is a promising candidate for inexpensive candidate for inexpensive and environmentally friendly memory devices. We have demonstrated that the FORM operation of the polymer devices depends on the concentration of Cu+ ions as well as the thickness of the polymer electrode. / M.S. / Although the scaling of conventional memories such as volatile dynamic random access memory (DRAM) and non-volatile flash technology is becoming increasingly difficult, new types of non-volatile memories, such as resistive switching memories, have recently attracted the attention of both industry and academia. Resistive switching memory is considered as the next generation non-volatile memory because of its excellent scalability, high switching speed, simple structure and low power consumption. What’s more, ReRAM is also a promising candidate for a flexible memory, as a variety of materials can be used both inorganics, organics and even hybrid nanocomposites. ReRAM shows unique nanoionics based filamentary switching mechanism. Besides the nonvolatile memory applications, resistive switching devices implement the formation of a memristor, which is the fourth basic electrical component and can be used for neuromorphic computing. First, we report the device property of Co based resistive switching devices with a structure of Cu/TaOX/Co layers. The I-V characteristics of the manufactured Cu/TaOX/Co devices shows very similar FORM, SET and RESET voltages for Cu conductive filaments compared with Pt device. However, the Co device has a significant smaller FORM, SET and RESET voltages for oxygen vacancy (VO) filaments, which can be partly attributed to the work function difference between Pt and Co of 13.5 eV and partly to the impaired integrity properties of Co vs Pt inert electrode. The main reason for the limit of SET-RESET operations is that high Joules heat dissipation. With high Joules heat accumulation, the maximum switching cycles of Co devices is up to 8 times, while in the case of Pt cases, it is almost unlimited. Secondly, we fabricated an organic ReRAM device with the structure Cu-doped PANI-CSA/O-AA/Al. Cu-doped PANI-CSA polymer electrode has been introduced for the first time as the top polymer electrode of a ReRAM device. Compared to inorganic ReRAM device, this polymer device can be operated at a significantly lower forming voltage than inorganic devices such as Cu/TaOX/Pt. We have demonstrated that our organic ReRAM is a promising candidate for environmentally friendly and flexible memory devices. Our results demonstrate the FORM operation of the polymer devices depend on the concentration of Cu+ ions as well as the thickness of the polymer top layer.
26

Synthesis and electrochemical characterisation of conducting polyaniline-fly ash matrix composites.

Mavundla, Sipho Enos. January 2005 (has links)
<p> <p>&nbsp / </p> <p align="left">&nbsp / </p> <p>&nbsp / </p> </p> <p align="left">The aim of this study was to produce useful composite materials from fly ash, a major waste product of coal combustion from power plants. Polyaniline-fly ash (PANI-FA) composites were prepared by in situ polymerisation of aniline in the presence of Fly Ash (FA) by two slightly different methods. In one case polystyrene sulphonic acid (PSSA) was used as a stabilizer and in another case the starting materials (aniline and FA) were aged before oxidation. The aging procedure formed nanotubes that have cross-sectional diameters of 50-110 nm. The other procedure produced nanotubes with a diameter of 100-500 nm and the length of up to 10&mu / m. The presence of metal oxides and silica in FA were responsible for the formation of nanorods in PANI-PSSA-FA.. The formation of the composites was confirmed by UV-Vis and FTIR. The UV-Vis showed maximum absorbance at 330-360 nm ( due to &pi / -&pi / * transition of benzoid rings) and 600-650 nm(due to charge transfer excitons of quinoid rings), which are characteristics of emaraldine base. The electrochemical analysis of the composites showed that the composites were conductive and electroactive. The Cyclic Voltammetry of PANI-PSSA-FA showed three redox couples which are characteristics of sulphonated PANI. The morphology of the composites was studied by Scanning Electron Microscopy (SEM) and showed that our methods gave composites with improved homogeneity as compared to other reported methods. Thermo Gravimetric analysis (TGA) showed that the presence of FA in the composites improves the thermal stability of the composites by up to 100 0C.<br /> &nbsp / </p>
27

Electrochemical Studies Of PEDOT : Microscopy, Electrooxidation Of Small Organic Molecules And Phenol, And Supercapacitor Studies

Patra, Snehangshu 04 1900 (has links)
Following the discovery of electronic conductivity in doped polyacetylene, various studies on conducting polymers have been investigated. These polymers are essentially characterized by the presence of conjugated bonding on polymer backbone, which facilitates formation of polarons and bipolarons as charge carriers. Poly(3,4-ethylenedioxythiophene) (PEDOT) is an interesting polymer because of high electronic conductivity, ease of synthesis and high chemical stability. Electrochemically prepared PEDOT is more interesting than the polymer prepared by chemical routes because it adheres to the electrodes surface and the PEDOT coated electrodes can directly be used for various applications such as batteries, supercapacitor, sensors, etc. A majority of the studies described in the thesis are based on PEDOT. Studies on polyanthanilic acid and reduction of hydrogen peroxide on stainless steel substrate are also included. Chapter 1 provides an introduction to conducting polymers with a focus on synthesis, electrochemical characterization and applications of PEDOT. In Chapter 2, microscopic and impedance spectroscopic characterization of PEDOT coated on stainless steel (SS) and indium tin oxide (ITO) coated glass substrates are described. Electrosynthesis of PEDOT is carried out on SS electrodes by three different techniques, namely, potentiostatic, galvanostatic and potentiodynamic techniques. The SEM images of PEDOT prepared by the galvanostatatic and potentiostatic routes indicate globular morphology. However, it is seen that porosity increases by increasing the current or the potential. In the cases of both galvanostatic and potentiostatic routes, the oxidation of EDOT to form PEDOT takes place continuously during preparation. However, in the case of potentiodynamic experiment between 0 and 0.9 V vs. SCE (saturated calomel electrode), the formation of PEDOT occurs only when the potential is greater than 0.70 V. During multicycle preparation to grow thicker films of PEDOT, formation of PEDOT takes place layer by layer, a layer of PEDOT being formed in each potential cycle. PEDOT prepared in the potential ranges 0-0.90 V and 0-1.0 V show globular morphology similar to the morphology of the galvanostatically and potentiostatically prepared polymer. If prepared in the potential ranges 0-1.1 V and 0-1.2 V, the PEDOT films have rod-like and fibrous morphology. This is attributed to larger amount of PEDOT formed in each cycle in comparison with lower potential ranges and also to partial oxidation of PEDOT at potentials ≥ 1.10 V. PEDOT is also electrochemically prepared on ITO coated glass substrate. Preparation is carried out under potentiostatic conditions in the potential range between 0.9 and 1.2 V. Atomic force microscopy (AFM) studies indicate a globular topography for PEDOT films prepared on ITO coated glass plates. The height and width of globules increase with an increase in deposition potential. The PEDOT coated SS electrodes are subjected to electrochemical impedance spectroscopy studies in 0.1 M H2SO4. The Nyquist plot of impedance consists of a depressed semicircle, which arises due to a parallel combination of the polymer resistance and double-layer capacitance (Cdl). Impedance data are analyzed. Studies on electrooxidation of methanol, formic acid, formaldehyde and ethanol on nanocluster of Pt and Pt-Ru deposited on PEDOT/C electrode are reported in Chapter 3. Studies on electrooxidation of small molecules are important in view of their promising applications in fuel cells. Films of PEDOT are electrochemically deposited on carbon paper. Nanoclusters of Pt and bimetallic Pt-Ru catalysts are potentiostatically deposited on PEDOT/C electrodes. Catalysts are also prepared on bare carbon paper for studying the effect of PEDOT. The presence of PEDOT film on carbon paper allows the formation of uniform, well dispersed nanoclusters of Pt as well as Pt-Ru catalysts. TEM studies suggest that the nanoclusters of about 50 nm consist of nanoparticles of about 5 nm in diameter. Electrooxidation of methanol, formic acid, formaldehyde and ethanol are studied on Pt-PEDOT/C and PtRu-PEDOT/C electrodes by cyclic voltammetry and chronoamperometry. The data for oxidation of these small organic molecules reveal that PEDOT imparts a greater catalytic activity for the Pt and Pt-Ru catalysts. Results of these studies are described in Chapter 3. In Chapter 4, PEDOT is coated on SS substrate to investigate phenol oxidation. Studies on electrochemical oxidation of phenol are interesting because it is important to remove phenol from contaminated water or industrial effluents. Deactivation of the anode due to the formation and adsorption of polyoxyphenylene on its surface is a common problem for a variety of electrode materials, during phenol oxidation. Investigations on suitable anode materials, which can undergo no or moderate poisoning by polyoxyphenylene, are interesting. In the present study, it is shown that the electrooxidation rate of phenol is greater on PEDOT/SS electrodes than on Pt. Deactivation of PEDOT/SS electrode is slower in relation to Pt. The oxidation of phenol on PEDOT/SS electrode occurs to form both polyoxyphenylene and benzoquinone in parallel. Cyclic voltammetry of phenol oxidation is studied by varying the concentration of phenol, sweep rate and thickness of PEDOT. Ac impedance studies indicate a gradual increase in polymer resistance due to adsorption of polyoxyphenylene during multi sweep cyclic voltammetry. This investigation reveals that PEDOT coated on a common metal or alloy such as SS is useful for studying electrooxidation of phenol, which is generally studied on a noble metal based electrodes. Electrochemically prepared PEDOT is used for supercapacitor studies and the results are presented in Chapter 5. Generally, electronically conducting polymers possess high capacitive properties due to pseudo-faradaic reactions. PEDOT/SS electrodes prepared in 0.1 M H2SO4 are found to yield higher specific capacitance (SC) than the electrodes prepared from neutral aqueous electrolyte. The effects of concentration of H2SO4, concentration of SDS, potential of deposition and nature of supporting electrolytes used for capacitor studies on SC of the PEDOT/SS electrodes are studied. Specific capacitance values as high as 250 F g-1 in 1 M oxalic acid are obtained during the initial stages of cycling. However, there is a decrease in SC on repeated charge-discharge cycling. Spectroscopic data reflect structural changes in PEDOT on extended cycling. Self-doped PANI is expected to possess superior electrochemical characteristics in relation to PANI. The self-doping is due to the presence of an acidic group on the polymer chain. However, self-doped PANI is soluble in acidic solutions against insolubility of PANI. In the present study, poly(anthranilic acid), PANA, is encapsulated in porous Nafion membrane by chemical and a novel electrochemical methods. PANA present in solid form in Nafion membrane does not undergo dissolution in acidic solutions. The methods of preparation and various electrochemical, optical and spectroscopic characterizations studies of PANA-Nafion are described in Chapter 6. Electroreduction of H2O2 is studied on sand-blasted stainless steel (SSS) electrode in an aqueous solution of NaClO4 and the details are reported in Chapter 7. The cyclic voltammetric reduction of H2O2 at low concentrations is characterized by a cathodic peak at -0.40 V versus standard calomel electrode (SCE). Cyclic voltammetry is studied by varying the concentration of H2O2 in the range from 0.2 mM to 20 mM and the sweep rate in the range from 2 to 100 mV s-1. Cyclic voltammograms at concentrations of H2O2 higher than 2 mM or at high sweep rates consist of an additional current peak, which may be due to the reduction of adsorbed species formed during the reduction of H2O2. Amperometric determination of H2O2 at -0.50 V vs. SCE provides the detection limit of 5 μM H2O2. A plot of current density versus concentration has two linear segments suggesting a change in the mechanism of H2O2 reduction at concentrations of H2O2 ≥ 2 mM. From the rotating disc electrode study, diffusion co-efficient of H2O2 and rate constant for reduction of H2O2 are evaluated. Thus, stainless steel, which is inexpensive and a common alloy, is useful for studying electrochemical reduction of H2O2 and also for analytical application. This work is initiated to study the reduction of H2O2 on PEDOT/SS electrodes. As a result of preliminary experiments, it is found that PEDOT does not exhibit any influence on the kinetics of H2O2 reduction. Therefore studies conducted using bare stainless steel are included in this chapter. Results of the above studies are described in the thesis.
28

Electrochemical Studies Of Polyaniline And Some Of Its Applications

Mondal, Sujit Kumar 01 1900 (has links)
The studies reported in the thesis deal with surface modification of non-platinum metals by coating with electronically conducting polymers, namely, polyanilne (PANI) and polypyrrole (PPY). The oxidation of Г/I2, hydroquinone/quinine and [Fe(CN)6]3-/ [ Fe(CN)6]4-are studied by cyclic voltammetry and chronoamperometry experiments. It has been shown tht the redox reactions, which do not occur on bare stainless steel electrode, occur through electron-transfer mediated by conducting polymers. The effect of heating of polyaniline (PANI) at 80 0C on its electrochemical activity is studies. Although the thermogravimetric analysis indicates that PANI is stable at temperatures up to about 250 0C and it undergoes decomposition at higher temperatures, its intrinsic redox electrochemical activity decreases with duration of heating at a temperature as low as 80 0C . The polymer completely loses its electrochemical activity. The decrease in lectrochemical activity of PANI is attributed to an irreversible loss of water molecules. The reaction order for degradation of PANI is found to be close to unity, and a value of 1.63 X 10-4 s-1 is obtained for the rate constant. The deactivated PANI does not recover its electrochemical activity even after a prolonged treatment in acidic electrolytes. The electrodeposition of PANI is carried out by galvanostatic, potentiostatic and potentiodynamic methods. The impedance data reflect a marked difference between the PANI deposited by static and dynamic methods. Furthermore, the impedance parameters vary with the sweep rate used in potentiodynamic method. Electrochemical impedance spectra of the electrodes are analyzed using a transmission line model consisting of two rails of finite resistances. Electrochemical deposition of polyaniline (PANI) is carried out on a porous carbon substrate for supercapacitor studies. PANI deposited at 100 mV s-1 sweep rate by potentiodynamic technique on porous carbon substrate is found to possess superior capacitance properties. Capacitance values as high as 1600 F g-1 are obtained and PANI coated carbon electrodes facilitate charge-discharge current densities as hgh as 45 mA cm-2 (19.8 A g-1 ). Electrodes are found to be fairly stable over a long cycle-life, although there is some capacitance loss during the initial stages of cycling. Electrooxidation of ascorbic acid on polyaniline is studied in a fuel-cell. Ascorbic acid (H2A) is employed as fuel and polyaniline (PANI) as the catalyst. H2A is an environmentally and biologically friendly molecule. The catalyst, namely PANI does not consist of any platinum group metal, and at 70 0C , a maximum power density of 4.3 mW cm-2 is obtained at a current density of 15 mA cm-2 . Also, studies on anodically deposited RuO2 for capacitor applications are reported. Cathodic deposition of RuO2 generally produces a mixture of Ru and RuO2 . On the other hand, the anodic depsotion on SS substrates is found to produce RUO2 which is characterized with high power supercapacitance properties. A capacitance value of 274 F g-1 is obtained at a current density of 20mA cm-2 .
29

Synthesis and electrochemical characterisation of conducting polyaniline-fly ash matrix composites.

Mavundla, Sipho Enos. January 2005 (has links)
<p> <p>&nbsp / </p> <p align="left">&nbsp / </p> <p>&nbsp / </p> </p> <p align="left">The aim of this study was to produce useful composite materials from fly ash, a major waste product of coal combustion from power plants. Polyaniline-fly ash (PANI-FA) composites were prepared by in situ polymerisation of aniline in the presence of Fly Ash (FA) by two slightly different methods. In one case polystyrene sulphonic acid (PSSA) was used as a stabilizer and in another case the starting materials (aniline and FA) were aged before oxidation. The aging procedure formed nanotubes that have cross-sectional diameters of 50-110 nm. The other procedure produced nanotubes with a diameter of 100-500 nm and the length of up to 10&mu / m. The presence of metal oxides and silica in FA were responsible for the formation of nanorods in PANI-PSSA-FA.. The formation of the composites was confirmed by UV-Vis and FTIR. The UV-Vis showed maximum absorbance at 330-360 nm ( due to &pi / -&pi / * transition of benzoid rings) and 600-650 nm(due to charge transfer excitons of quinoid rings), which are characteristics of emaraldine base. The electrochemical analysis of the composites showed that the composites were conductive and electroactive. The Cyclic Voltammetry of PANI-PSSA-FA showed three redox couples which are characteristics of sulphonated PANI. The morphology of the composites was studied by Scanning Electron Microscopy (SEM) and showed that our methods gave composites with improved homogeneity as compared to other reported methods. Thermo Gravimetric analysis (TGA) showed that the presence of FA in the composites improves the thermal stability of the composites by up to 100 0C.<br /> &nbsp / </p>
30

Desenvolvimento e caracterização de dispositivos luminescentes híbridos

Biscuola, Marco Aurélio [UNESP] 18 December 2006 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-18Bitstream added on 2014-06-13T20:53:29Z : No. of bitstreams: 1 biscuola_ma_me_rcla.pdf: 2829290 bytes, checksum: 4f1c3c8a080dce0360b3e6c8d278b78c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As novas tecnologias para a construção de telas e displays têm permitido reduzir o consumo de energia, o peso e a espessura, como também melhorar a eficiência e flexibilidade se comparado aos antigos monitores de CRTs e até mesmo aos atuais displays de cristal líquido. Dentre estas novas tecnologias destacam-se as que utilizam materiais orgânicos (OLED) ou orgânicos poliméricos (PLED) não somente por suas possibilidades de aplicações industriais, mas também por permitirem o desenvolvimento das ciências básica e aplicada. Seguindo uma linha alternativa, propomos, neste trabalho, um novo compósito híbrido, resultante da combinação de uma fase polimérica e uma fase inorgânica, que, do nosso ponto de vista também poderá contribuir para o desenvolvimento dessa nova geração de displays e telas. Este compósito é formado pela blenda de um polímero condutor dopado, a PANI (polianilina) ou POMA (poli(o-metóxi anilina)), e um polímero isolante, o P(VDF-TrFE) poli(vinilideno-co-trifluoretileno), na qual micro partículas de Zn2SiO4:Mn (SZF) foram adicionadas. Para o desenvolvimento desse novo compósito, estudamos cada um de seus elementos constituintes, notadamente quanto ao seu modo de preparo, características morfológicas e propriedades elétricas. Como resultado final, obtivemos dispositivos constituídos de uma única camada do compósito híbrido depositado por espalhamento sobre um substrato de ITO/FTO, acrescido, ainda, de um eletrodo de alumínio depositado por evaporação. Para a caracterização destes dispositivos foram realizadas medidas de condutividade elétrica, luminescência (L) e fotoluminescência (PL). Os compósitos PANI/P(VDF-TrFE)/SZF 05/95/80 e POMA/P(VDF-TrFE)/SZF 25/75/80 com condutividade elétrica da ordem de 10-3 S/m foram os que melhor se adequaram para a construção dos dispositivos. Os espectros de L e PL apresentaram um pico em ? = 538... . / New technologies recently applied to the fabrication of organic screens and displays have allowed the manufacture of lighter, thinner monitors in comparison to either the conventional cathodic rays tube (CRTs) or the liquid crystal displays (LCDs). In addition, displays based on organic materials (the so-called organic light emitting displays (OLEDs and the polymeric light emitting displays - PLEDs) may exhibit improved efficiency and flexibility. The organic displays have attracted attention of a number of research groups aimed at investigating the potential applications of these new devices in the electronic industry. In this study, a new hybrid composite comprising an inorganic phase dispersed in a polymeric matrix was investigated as a possible candidate material for displays fabrication. The continuous, organic phase was a blend containing a conducting polymer, viz. polyaniline (PANI) or its derivative poly(o-methoxyaniline) (POMA) and an insulating polymer, P(VDF-TrFE) (Poly(viny1idene fluoride- trifluorethylene)). Micro particles of Zn2SiO4:Mn (SZF) was added to the polymeric phase as the luminescent, active material. Luminescent devices were fabricating using a conventional trilayer architecture in which a thin film of the hybrid composite was deposited between two conducting electrodes. As the anode electrode we used either Indium-TinOxide (ITO) or Fluorine-Tin-Oxide (FTO)-covered glass plates. Evaporated aluminum was used as the cathode electrode. The material/device characterization was carried out using electric conductivity, luminescence (L) and photoluminescence (PL) measurements. PANI/P(VDFTrFE)/ SZF (05/95)/80 and POMA/P(VDF-TrFE)/SZF (25/75)/80 composites compositions presented the best performance, with electric conductivity of ca. 10-3 S/m. Luminescence and photoluminescence measurements revealed that both devices exhibited an emission band centered at 538 nm... (Complete abstract, click electronic address below).

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