Orientador: Luiz Fernando Zagonel / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T03:52:44Z (GMT). No. of bitstreams: 1 Ramos_Raul_M.pdf: 5673835 bytes, checksum: 005e134cbd8cbb241cbdf367a75f35a3 (MD5) Previous issue date: 2015 / Resumo: Eletrodos condutores transparentes (TCE) possuem grande importância para tecnologias de informação e geração de energia. O TCE mais eficiente na atualidade é o ITO (In2O3 dopado com Sn), que pode alcançar resistividades em torno de 2.10-4 ?cm e uma transmitância ótica de 80% a 90% na região do visível. Entretanto, a escassez dos recursos naturais de Índio e sua grande demanda sugerem a necessidade de materiais alternativos. O presente estudo tem por objetivo investigar as propriedades óticas, eletrônicas e estruturais de filmes finos de TiO2 (fase anatase) dopados com Nitrogênio. A deposição dos filmes foi feita por Deposição por Feixe de Íons (IBD) por bombardeamento de um alvo de titânio puro com íons de Ar+ em atmosfera de O2. Os filmes, com uma espessura de ?90 nm, foram depositados em substrato de quartzo amorfo (Herasil-1) a temperaturas de 400 ou 500°C. Depois, os filmes são dopados com implantação iônica, variando o tempo de 10 a 60 minutos, com feixe de íons misto a baixa energia de N2+ e H2+ com 150 eV e sob a mesma temperatura de crescimento. Após a implantação, medidas Hall indicam que a densidade de portadores majoritários nos filmes de anatase dopados com nitrogênio chegam até ?1019 cm?3 (enquanto filmes não dopados tem densidade de cargas de ?1012 cm?3). A resistividade dos filmes dopados chegam até 10?1 ?cm enquanto mantem boa transmissão ótica (>80%). De fato, dependendo do tempo de dopagem e da temperatura do substrato durante o processo, a transmissão de até 85% podem ser obtida em 550 nm com tal resistividade (?10?1 ?cm). Espectroscopia de fotoelétrons emitidos por raio-x (XPS) realizadas in situ mostram que a composição na superfície é compatível com TiO2?xNx com concentração de nitrogênio de até ? 20%. Difração de raio-x com ângulo de incidência rasante (GIXRD) confirmaram a estrutura cristalina anatase dos filmes antes e após a implantação iônica à baixa energia (150 eV). Este estudo indica que é possível dopar a amostra anatase com nitrogênio através do uso de um feixe de íons de baixa energia. Tal abordagem é interessante por permitir um controle da concentração de dopantes (Nitrogênio através de um precursor gasoso) de forma mais controlada do que usualmente obtido por sputtering reativo / Abstract: Transparent conductive electrodes (TCE) have great importance for information and energy technologies. The most efficient TCE is currently the ITO (Sn-doped In2O3), which may have a resistivity lower than 2·10?4 ?cm and an optical transmittance of 80% to 90% in the visible region. However, the scarcity of natural resources of Indium and its great demand suggests the need of alternative materials. The present study aims to investigate the optical, electronic and structural properties of thin films of TiO2 (anatase phase) doped with nitrogen. The films deposition is made by Ion Beam Deposition (IBD) by bombarding a pure titanium target with Ar+ ions in O2 atmosphere to a thickness of about 90 nm. The films are deposited on an amorphous quartz substrate (Herasil-1) at 400 or 500 °C. Afterwards, the films are doped by ion implantation with low-energy ion beam mixed of N2+ and H2+ at 150 eV and under the same temperature of the growth for times ranging from 10 to 60 minutes. After implantation, Hall measurements indicated that the majority carrier density in the nitrogen doped anatase films reaches up to ? 1019 cm?3 (while the undoped films have a carrier density of ? 1012 cm?3). The resistivity of the doped films is as low as 10?1 ? cm while maintaining good optical transmission. Indeed, depending on the doping time and substrate temperature, transmission of up to 90% could be obtained at 550 nm with this resistivity. X-ray photoelectron spectroscopy (XPS) performed in situ shows that the surface composition is compatible with N:TiO2?x with nitrogen concentrations of up to ? 20%. Small angle x-ray diffraction measurements (SAXRD) confirmed the anatase crystal structure of the films before and after the low energy ion implantation. This study indicates that it is indeed possible to dope anatase thin films with nitrogen by low energy ion beam. This approach is interesting for allowing a greater control of doping concentration with respect to what is usually obtained by reactive sputtering / Mestrado / Física / Mestre em Física / 2013/118682-8 / CAPES

É grande o interesse em combinar as propriedades mecânicas e elétricas de diferentes materiais poliméricos. Neste trabalho, filmes de Borracha Natural com camadas superficiais condutoras de polianilina (PANI) são preparados e caracterizados por diferentes técnicas. A PANI dopada foi depositada em ambos os lados do filme de borracha por polimerização química \"in situ\" da anilina a temperatura ambiente. O processo da polimerização da PANI \"in situ\" foi otimizado variando a concentração dos reagentes químicos com o objetivo de se obter uma camada de PANI com espessura desejada, boa adesão na borracha e que produzisse também aumento da condutividade elétrica na superfície. As amostras obtidas são caracterizadas usando-se Microscopia Eletrônica de Varredura, Microscopia Óptica, Difratometria de raios-X, análise por Calorimetria Diferencial de Varredura, análise Termo-Dinâmico-Mecânica, análise Termogravimétrica, Espectroscopia no FT-IR, Ensaio Mecânico e condutividade elétrica na superfície e no volume dos filmes preparados. Os resultados mostram que os filmes produzidos são do tipo multicamadas, pois não há uma interpenetração da PANI na borracha. A melhor condutividade e uniformidade é obtida com filmes preparados com três deposições, atingindo a ordem de 10-7 S/cm / The combination of properties of different polymeric materials in one sample is of great interest. In this work natural rubber films covered with a layer of conductive polyaniline (PANI) were prepared and studied by means of several experimental techniques. The doped PANI layer was deposited onto both rubber films surfaces by the \"in situ\" polymerization technique. The polymerization of PANI was performed at room temperature and the deposition process was optimized in order to obtain a PANI layer with an adequate thickness, good adhesion to the rubber and to promote the increase of its surface electric conductivity. Samples were characterized employing the scanning electron microscopy, optical microscopy, X-ray diffractometry, differential scanning calorimetry, thermo gravimetric analysis, dynamic mechanical thermal analysis, mechanical analysis and surface/volume electric conductivity. Results showed that the formed films consisted of a PANI layer that did not penetrated in the rubber. The better uniformity of deposition and maximum electric conductivity of the order of 10-7 S/cm was obtained on films that were prepared by deposition of three PANl layers

The continued growth of the optoelectronics industry and the emergence of wearable and flexible electronics will continue to place an ever increasing pressure on replacing ITO, the most widely used transparent conducting electrode (TCE). Among the various candidates, graphene shows the highest optical transmittance in addition to promising electrical transport properties. The currently available large-scale synthesis routes of graphene result in polycrystalline samples rife with grain boundaries and other defects which limit its transport properties. Chemical doping of graphene is a viable route towards increasing its conductivity and tuning its work function. However, dopants are typically present at the surface of the graphene sheet, making them highly susceptible to degradation in environmental conditions. Few-layers graphene (FLG) is a more resilient form of graphene exhibiting higher conductivity and performance stability under stretching and bending as contrasted to single-layer graphene. In addition FLG presents the advantage of being amenable bulk doping by intercalation. Herein, we explore non-covalent doping routes of CVD FLG, such as surface doping, intercalation and combination thereof, through in-depth and systematic characterization of the electrical transport properties and energy levels shifts. The intercalation of FLG with Br2 and FeCl3 is demonstrated, showing the highest improvements of the figure of merit of TCEs of any doping scheme, which results from up to a five-fold increase in conductivity while maintaining the transmittance within 3% of that for the pristine value. Importantly the intercalation yields TCEs that are air-stable, due to encapsulation of the intercalant in the bulk of FLG. Surface doping with novel solution-processed metal-organic molecular species (n- and p-type) is demonstrated with an unprecedented range of work function modulation, resulting from electron transfer and the formation of molecular surface dipoles. However, the conductivity increases compared modestly to intercalation as the electron transfer is limited to the uppermost graphene layers. Finally, a novel and universal multi-modal doping strategy is developed, thanks to the unique platform offered by FLG, where surface and intercalation doping are combined to mutually achieve high conductivity with an extended tunability of the work function. This work presents doped-FLG as a prospective and versatile candidate among emerging TCEs, given the need for efficient and stable doping routes capable of controllably tuning its properties to meet the criteria of a broad range of applications.

This diploma thesis deals with creation of transparent conductive layers on glass substrate, which serve as underlay for electrochromic layers. Zinc acetate dissolved in methane and distilled water serves as basis of solution. We are searching for optimal amount of either Fluor or Boron in depositted solutions to achieve best transparency and layer conductivity.

This work aims to investigate the vapor sensing behavior of conductive polymer composites (CPCs). In connection with the protection of the environment and human beings, sensing of different kinds of chemical vapors is of increasing importance. At the moment, four kinds of vapor sensors are widely investigated and reported, namely semiconducting metal oxide sensors (MO), conjugated polymer sensors, carbonaceous nanomaterial based sensors, and CPC based sensors. Due to their unique component systems, the different sensor types are based on different sensing mechanisms resulting in different potential application ranges. In consideration of cost and processability, CPC based vapor sensors are promising owning to their low cost, excellent processability, and designable compositions. In terms of vapor sensing behavior of CPC sensors, the interaction between the polymer and the organic vapor is a decisive factor in determining the sensing performance of CPCs. Ideally, the chosen polymer matrix should be able to swell without dissolving during vapor exposure so that the conductive network within the matrix can be disconnected, giving rise to the resistance change of CPCs. In some reported cases, polymers such as PLA and polycaprolactone (PCL) are degradable polymers, which are not durable when being exposed to environmental conditions for a long time. Therefore, it is necessary to make sure whether the selected polymers are resistive to vapors or not. There are two options for the polymer selection. One is to select a polymer that is only swellable in a specific or few organic solvents; another one is to select a polymer that is swellable to a variety of solvents. Since CPC sensors are used for detecting as many as possible hazardous chemicals to human beings or environment, the second case is more desired because of its broader window of detection. The solubility parameter is effective to characterize the interaction of polymers and organic solvents/vapors, which was firstly proposed by Charles Hansen. Initially, the Hansen solubility parameter (HSP) was used to predict the compatibility between polymer partners, chemical resistance, permeation rates, and even to characterize the surface of fillers. Liquids with similar solubility parameter (δ) are miscible, and polymers will dissolve in solvents whose δ is similar to their own value. This behavior is recognized as “like dissolves like”. Based on the description above, CPCs that can be used as liquid/vapor sensor materials should meet the following two requirements: 1) the chosen polymer should be swellable to vapors; 2) the CPCs as sensor materials have to be electrically conductive. Therefore, the relationship between conductive network and vapor sensing behavior of CPCs was investigated from the following aspects: 1) According to the previous studies, CB/polymer composites exhibit poor reversibility in cyclic vapor sensing tests because of the susceptible conductive network formed by CB particles. Thus, there is a need to improve the reversibility and increase the relative resistance change (Rrel) of CPCs. MWCNTs, as 1-dimensional carbon fillers with high aspect ratio, have excellent electrical and mechanical properties. Therefore, a hybrid filler system (MWCNT and CB) was utilized and incorporated in polycarbonate (PC) via melt compounding. PC was selected as the polymer matrix of CPCs because it showed high affinity with many commercial organic solvents/vapors as well as high and fast volume change upon organic solvents/vapors. In order to discuss the effect of conductive network formation on the vapor sensing behavior of PC/MWCNT/CB composites, two MWCNT contents were selected, which were lower and higher than the electrical percolation threshold of the PC/MWCNT composites. In the following, three CB contents were selected for the mixtures with MWCNT. The conductive networks composed of either MWCNT or hybrid CB/MWCNT are compared. The morphology of CPCs with different hybrid filler ratios was observed and investigated using SEM and OM. Moreover, to quantify the vapor sensing behavior of CPCs, some organic solvents were chosen and characterized by Flory-Huggins interaction parameter to demonstrate the polymer-vapor interaction. Afterwards, the cyclic vapor sensing was applied to illustrate the vapor sensing behavior of CPCs with different conductive network formations. 2) At moment, the filler dispersion is still a big challenge for MWCNT filled polymer composites due to the fact that the strong Van der Waals force among nanotubes makes them easily to entangle with each other resulting in the formation of agglomerates. A good filler dispersion state is desirable to achieve CPCs with low φc and. In order to reduce the φc of CPCs, immiscible polymer blend systems are introduced, which can have different blend microstructures by adjusting the polymer component ratios. In the second section, an immiscible polymer blend system based on two amorphous component, namely PC and polystyrene (PS), was chosen aiming to explain the influence of the blend morphology on the sensing performance of CPCs. PC/PS blends with different compositions filled with MWCNT were fabricated by melt mixing. The selective localization of MWCNTs in the blends was predicted using the Young’s equation. Moreover, the composite morphology, filler dispersion, and distribution were characterized by SEM and TEM. In the following, three kinds of CPCs ranging from sea-island structure to co-continuous structure were selected for the cyclic sensing measurement. The relationship between composite microstructure and resulting vapor sensing behavior was evaluated and discussed. 3) The poor reversibility of CPCs towards good solvent vapors is still a problem that hinders the cyclic use of CPC sensor materials. As an important class of polymer, crystalline polymers are rigid and less affected by solvent penetration because of the well-arranged polymer chains. Therefore, the effect of polymer crystallinity on the vapor sensing behavior of CPCs is imperative to be studied. In the third section, poly(lactic acid) (PLA), a semi-crystalline polymer, was selected to melt-mixed with PS and MWCNTs with the aim to improve the sensing reversibility of CPCs towards organic vapors, especially good solvent vapors. Thermal annealing was utilized to tune the PLA crystallinity and the polymer blend microstructure of CPCs. The electrical, morphological, and thermal behavior of CPCs after different thermal annealing times is discussed. In the following, the effect of crystallinity on the vapor sensing behavior of the CPCs was studied in detail. Besides, the different sensing performances of the CPCs towards different vapors resulted from the selective localization of MWCNTs and increased polymer matrix crystallinity were investigated and compared. 4) As discussed for the amorphous polymer blends and crystalline polymer blends and their vapor sensing behavior. The comparison of compact and porous structure of CPCs is going to be studied. In the fourth section, studies to further improve the sensing performance and to find out the exact sensing mechanism of CPCs were performed. Therefore, poly(vinylidene fluoride) (PVDF), a solvent resistive polymer, was chosen to be melt-mixed with PC and MWCNTs. In order to compare the MWCNT dispersion and localization in the blends, three kinds of PCs with different molecular weights were selected; hence, the viscosity ratio of immiscible blends was varied. Rheological, morphological, and electrical properties of CPCs were characterized. After that, the cyclic sensing and long-term immersion tests of CPCs towards different vapors were carried out to evaluate the vapor sensing behavior of compact CPCs with different blend viscosity ratios. Moreover, porous CPC sensors were prepared by extracting the PC component. The same sensing protocols were also applied to these porous sensor materials. The sensing mechanisms between compact CPC sensor and porous CPC sensor were compared and investigated.

Microbial electrosynthesis (MES) has recently emerged as a novel biotechnology platform for value-added product generation from waste CO2 stream. Integrating MES technology with renewable energy sources for both CO2 valorization and renewable energy storage is regarded as one type of artificial photosynthesis and a perfect example of circular bioeconomy. However, several challenges remain to be addressed to scale-up MES as a feasible process for chemical production, which include enhanced production rate, reduced energy consumption and excellent resistance to external fluctuations. To fill these knowledge gaps, different in-depth approaches were proposed in this dissertation by optimizing the cathode architecture, CO2 flow rates and utilizing efficient photoelectrode to improve MES performance and stability. A novel cathode design, made of conductive hollow fiber membrane, was developed in this dissertation to improve CO2 availability at MES cathode surface via direct CO2 delivery to chemolithoautotrophs through the pores in the hollow fibers. By modifying the hollow fiber surface with carbon nanotubes (CNTs), higher bioproduct formation was achieved with excellent faradaic efficiencies, which could be attributed to the improved surface area for bacterial adhesion and the reduction of cathodic electron transfer resistance. Since CO2 flow rate from industrial facilities typically varies over time, this hollow-fiber architecture was also applied to test the resistance of MES systems to CO2 flow rate fluctuation. Stepwise increase of CO2 flow rates from 0.3 ml/min to 10 ml/min was tested and the effect of CO2 flow rate fluctuations was evaluated in terms of biochemical generation and microbial community. MES was further integrated with renewable energy supply for both energy storage and CO2 transformation into biofuels and biochemicals. Stable MES photoanode, based on molybdenum-doped bismuth vanadate deposited on fluorine-doped tin oxide glass (FTO/BiVO4/Mo), was prepared for efficient solar energy harvesting and overpotential reduction for oxygen evolution reaction (OER), which contributed to one of the highest solar-to-biochemical conversion efficiencies ever reported for photo-assisted MES systems. The applied nature of this dissertation with fundamental insights is of great importance to bring MES one step closer to full-scale applications and enable MES technology to be economically more viable for renewable energy storage and CO2 valorization.

The transparent conductive oxide (TCO) SnO2:Ta is developed as a selectively solar-transmitting coating for concentrated solar power (CSP) absorbers. Upon covering with an antireflective layer, a calculated absorptivity of 95% and an emissivity of 30% are achieved for the model configuration of SnO2:Ta on top of a perfect black body (BB). High-temperature stability of the developed TCO up to 1073 K is shown in situ by spectroscopic ellipsometry and Rutherford backscattering spectrometry. The universality of the concept is demonstrated by transforming silicon and glassy carbon from non-selective into solar-selective absorbers by depositing the TCO on top of them. Finally, the energy conversion efficiencies of SnO2:Ta on top of a BB and an ideal non-selective BB absorber are extensively compared as a function of solar concentration factor C and absorber temperature TH. Equal CSP efficiencies can be achieved by the TCO on BB configuration with approximately 50% lower solar concentration. This improvement could be used to reduce the number of mirrors in a solar plant, and thus, the levelized costs of electricity for CSP technology.

Electrification of transportation could be one pathway into sustainability since the electricity production can originate from renewable and low carbon energy sources. Electrifying the road could also reduce the battery dependence and further increase the vehicle efficiency in sense of energy consumption and load capacity when thinking of storage of electric energy in vehicle batteries. Not only is the Electric Road System (ERS) a rather new concept, it also raises concerns about consequences on health, safety, environment and public acceptance. The aim of this master thesis, within the logistics domain, is to interdisciplinary investigate the concept of electrified roads and to define potential blockers and in various extents investigate their feasibility. The potential blockers are assessed at a system level meaning that the depth of analysis of each aspect depends on the amount of data available and the relative importance according to the experts. Given the limits of research time, points that require more investigation have been indicated. This study will have a focus on freight vehicles since that is the vehicle considered to lack alternative solution towards decarbonization. The areas chosen for a closer analysis are health, safety and environment. The information available regarding the ERS impact on those areas is very limited even though they seem to constitute crucial factors for gaining the public acceptance. By investigating energy usage and CO 2 emissions in different phases of the ERS, the feasibility of the environment is assessed. Investigating the Electromagnetic Fields (EMF) produced by the inductive on-road charging technology, part of the ERS, approaches the possible health effects of ERS. Health effects of particles and pollutants are also touched upon. Accidents involving Electric Vehicles (EVs) and the transportation of dangerous goods through ERS will also be analyzed in the safety chapter. Ongoing projects and available technologies are used and taken into consideration throughout the study. Feedback from the industry and people involved with the ERS concept contribute in defining the fields facing significant uncertainties. In the last part, two scenarios are being analyzed in the sense of testing the feasibility of the inductive on-road charging in city logistics and for the big city triangle. This study has its base in literature reviews and interviews with experts within the industry. The different ERS technologies are still under development why many specific parameters are confidential. This poses some unintentional limits to this study in the sense of difficulty drawing specific conclusions. Therefore factors such as commercialization of the vehicle, health, safety and development time remain uncertain. Others such as environmental impact seem to benefit from the ERS, while others motivates the introduction of ERS such as the battery manufacturing.

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13240号 / 論工博第4178号 / 新制||工||1720(附属図書館) / (主査)教授 木本 恒暢, 教授 藤田 静雄, 教授 山田 啓文 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Après l'agriculture, l'industrie textile a engendré un important problème de pollution de l'eau car la plupart des produits chimiques provenant de ces industries sont hautement toxiques et affectent directement ou indirectement la santé humaine. La pollution électromagnétique (EM) est un autre problème important qui détériore les performances et la durée de vie des objets électroniques et nuit également à la santé humaine. Dans ce contexte, la nature fibreuse inhérente des nanomatériaux cellulosiques et leurs propriétés mécaniques remarquables, associées à une biocompatibilité et à une ressource durable, offrent un potentiel énorme en tant que composant dans les membranes de filtration de l'eau et les atténuateurs de micro-ondes verts. L'objectif principal de cette thèse est de fabriquer des objets fonctionnels à base de nanofibres de cellulose pour la filtration de l'eau et la suppression des micro-ondes. La méthode présentée dans ce manuscrit décrit un nouveau matériau absorbant à partir de nanofibres de cellulose par l'intermédiaire d'une méthode non solvatée utilisant l'acide de Meldrum comme agent d'estérification pour l'absorption de colorants toxiques. Cette innovation offre une nouvelle plate-forme pour le traitement de surface des nanofibres de cellulose utilisant une technologie verte sans solvant. Classiquement, les métaux ont été utilisés pour protéger les ondes électromagnétiques, mais sont fortement indésirables en raison de leurs inconvénients tels que des poids plus élevés, une nature corrosive et une difficulté de traitement en formes complexes. Les nano- papiers, à base de cellulose conductrice, peuvent offrir une solution verte à ce problème. La cellulose rendue conductrice présente une efficacité de blindage totale de plus de 20 B. Il s’agit d’une plate-forme efficace pour développer des atténuateurs verts respectueux de l'environnement. / After agriculture, the textile dyeing and finishing industry has generated a large water pollution problem as most of the chemicals coming from these industries are highly toxic and directly or indirectly affect human health. Another important issue is the Electro Magnetic (EM) pollution which deteriorates the performance and life of electronic gadgets and also adversely affects the human health. In this context, cellulose nanomaterial’s inherent fibrous nature and remarkable mechanical properties combined with low cost, biocompatibility and sustainable source, suggest huge potential as a component in water filtration membranes and green microwave attenuators in future. The main objective of this thesis is to fabricate cellulose nanofibers based functional constructs for clean water and microwave suppression. The presented unique method to produce novel absorbent material from cellulose nanofibers via non-solvent assisted method using Meldrum’s acid as an esterification agent for absorption of toxic dyes from water has not been addressed till date. This finding offers a new platform for the surface treatment of cellulose nanofibers using solvent free green technology. Conventionally, metals were used to shield EM waves but are highly undesirable due to their inherent drawbacks such as higher weights, corrosive nature and difficulty of processing into intricate shapes. Conductive cellulose nanopapers can offer a potential green feasible solution to this problem. The presented conductive cellulose nanopapers with an effective total shielding effectiveness of > 20 B will be a promising candidate for commercial device applications and will be an effective platform for developing eco-friendly green based attenuators.