As propriedades físico-químicas da superfície de pós cerâmicos desempenham um papel muito importante na obtenção de produtos cerâmicos de alta qualidade, elevada performance e confiabilidade. Estas propriedades estão relacionadas com as ligações químicas superficiais e suas interações com o meio. As superfícies dos óxidos geralmente contêm grupos hidroxilas adsorvidos e as suas modificações podem ser estudadas por espectroscopia de infravermelho. Neste trabalho, pós à base de SnO2 contendo íons Fe ou Mg foram preparados pela rota química derivada do método de Pechini. Os pós foram caracterizados quanto à sua morfologia e suas propriedades superficiais. Os resultados obtidos mostraram que os aditivos segregam na superfície e modificam as bandas de infravermelho correspondentes aos grupos hidroxilas adsorvidas superficialmente. Estas modificações causaram mudanças em propriedades macroscópicas como o ponto isoelétrico das suspensões aquosas e a área de superfície específica dos pós. Os estudos quanto à sinterização destes materiais foram feitos com pastilhas conformadas por pressão uniaxial e foram submetidas à sinterização por queima rápida, apresentando densificação em tempos muito curtos de tratamento térmico. (<1 min.) Observações microestruturais mostraram que a redução da porosidade neste sistema ocorre congruente com crescimento de grãos. O aumento da área de superfície específica dos pós com a elevação da porcentagem molar dos aditivos, bem como a densificação rápida do óxido de estanho pode estar relacionada com a redução das energias de superfície quando os aditivos estão segregados na superfície dos grãos. / Surface properties of ceramic powders frequently play an important role in producing high-quality, high-performance, and reliable ceramic products. These properties are related to the surface bond types and interactions with the surroundings. Oxide surfaces generally contain adsorbed hydroxyl groups and modifications in the chemical composition of the surface may be studied by infrared spectroscopy. In this work, SnO2 containing Fe or Mg ions were prepared by organic chemical route derived from Pechini’s method. The prepared powders were characterized by means of surface properties and morphology. Results demonstrated that the studied additives segregate onto the oxide surface and modify the hydroxyl IR bands of the adsorbed hydroxyl groups. These surface modifications change some macroscopic properties of the powder such as the isoelectric point (IEP) in aqueous suspensions and the final specific surface area. The sintering behavior of these materials was studied using pellets conformed by uniaxial pressing and the sintering was made by fast firing, showing quick densification with shorts periods of time (<1 min.). A porosity reduction congruent with grain growth is observed during microestructure characterization. Both, increase of the surface area with additive concentration and quick densification are supposedly due to the reduction of surface energy of the powders when additives segregate on the powder surface.

1 is a suitable material for thin-film gas sensors. Higher sensitivity could be achieved by platinum dopping of the layer. This work focuses on the optimalization of and thin film preparation by radio-frequency magnetron sputtering method. Subsequent analysis by means of XPS, AFM, SEM and XRD was carried out to determine physicochemical attributes of resulting layers. It appears that after the deposition, platinum within the layer is present in the metalic , as well as in the mixed chemical state. After the annealing process mixed state dominates over metalic state and after additional annealing platinum is present solely in oxidized form. Sensory response of layers for presence of hydrogen were examined on two different chip platforms (glass with chromium contacts and sapphire with platinum contacts). Contrary to expectations, the platinum dopped layers performed worse in comparison to the pure tin dioxide layers. This could be explained by the fact, that after annealing platinum within the layer was present mainly in the non-metalic form. Both and layers were more sensitive on sapphire platform, which could be associated with the crystal structure formed on its surface or with presence of metalic contacts.

Due to the increased awareness of living and industrial safety, carbon monoxide detectors must be geared towards better portability and sensitivity. Metal oxide semiconductor sensors should possess advantages such as heat and corrosion resistance, low cost materials, and ease of miniaturization. This thesis applied ball milled and powdered ZnO and SnO2 to manufacture into paste, then used the screen printing method deposited ZnO and SnO2 paste film and silver electrode on glass substrate. The influence on sensing film materials, temperature, time of heat treatment, and temperature of measurement was investigated. The samples were fabricated and measured by setting up self-measurement apparatus. The data was analyzed the changes of resistance under different air and carbon monoxide environments. This is followed by analysis of both surface topography and microstructure of the sensing film under OM and SEM. Experiment reveals that samples under different annealing process yield different surface morphology and micro structure while at the beginning of the heat treatment, epoxy evaporates from the sample brought about porous structure. Annealing at higher temperature sample will have more rough surface and better sensitivity in detecting carbon monoxide. After epoxy removed, heat treatment mechanism is then switched to sinter ZnO and SnO2 powders. the longer the samples are sintered, the lower the sensitive. Sensing films composited with ZnO and SnO2 will have better carbon monoxide sensitivity at 300oC but its sensitivity decays at a faster rate than samples working at 250 oC despite the slightly weaker sensitivity. Sensing films with pure ZnO will have higher sensitivity compared to pure SnO2 one. With the increase of SnO2 proportion, carbon monoxide sensitivities of detectors decreases, however, its life time can be improve significantly.

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This work have served as a preliminary work for a more extensiveresearch on antimony- and nickel-doped tin dioxide electrodes used forozone generation in electrolytic reactions. The target has been to test themanufacturing process of Sb/Ni-doped SnO2 with spin-coating techniqueand succeed to make electrodes for anodic ozone evolution and tocharacterize them. Electrode manufacturing was made using sol-gelfrom chloride salts of tin, antimony and nickel, which were applied to atitanium substrate through spin-coating. The substrates were spun todifferent thickness followed by drying and baking of the substrate. A setof electrodes with three layers were made just with spin-coating, additionallya set of electrodes with twenty layers were made with bothspin-coating and dip-coating. To characterize physical properties of theelectrodes, x-ray diffraction, scanning electron microscopy and transmissionelectron microscopy were conducted. Electrochemical measurementswere made in open beakers with a platinum cathode andsulphuric acid electrolyte using a galvanostatic measurement with afixed current. To measure the ozone evolution the optical absorbancedifference from the electrolyte compared to a clean electrolyte wasmeasured, this however only measures the amount of aqueous ozonepresent. Assembling of SnO2 electrodes for ozone evolution was successful.For the three-layered electrodes the absorbance readings wereinconclusive but with the twenty-layered electrodes there was a smell ofozone present within the electrolyte and absorbance reading of the dipcoatedelectrode presented a clear peak for ozone.

Submitted by Roberto de Aguiar Ramos Junior null (robeerto.aguiar.ramos@gmail.com) on 2018-04-03T14:25:40Z No. of bitstreams: 1 dissertaçao_final.pdf: 2202514 bytes, checksum: b29c60407d282d9848bdfc887c1a97c8 (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-04-04T19:31:40Z (GMT) No. of bitstreams: 1 ramosjunior_ra_me_bauru.pdf: 2202514 bytes, checksum: b29c60407d282d9848bdfc887c1a97c8 (MD5) / Made available in DSpace on 2018-04-04T19:31:40Z (GMT). No. of bitstreams: 1 ramosjunior_ra_me_bauru.pdf: 2202514 bytes, checksum: b29c60407d282d9848bdfc887c1a97c8 (MD5) Previous issue date: 2018-02-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho traz o estudo das propriedades óticas, elétricas e morfológicas do material TiO2 de forma individual e acoplado com SnO2 dopado com 4at%Sb, formando uma heteroestrutura. Tanto TiO2 quanto a heteroestrutura foram trabalhados na forma de filmes finos depositados pelo método sol-gel-dip-coating, e, no caso do TiO2 também foi relevante sua análise em forma de pós prensados (pastilhas). No que diz respeito ao SnO2:4%Sb, este trabalho traz uma revisão literária de suas principais propriedades, buscando apresentar um panorama geral, pois com isto pode-se entender melhor os fenômenos que ocorrem na heteroestrutura. Os resultados das pastilhas de TiO2 indicam uma transição parcial de fase anatase/rutilo para tratamentos térmicos entre 500ºC e 1000ºC, confirmadas pela fotoluminescência, que apresentou bandas relacionadas a fase anatase ou rutilo, dependendo do processamento utilizado. Filmes de TiO2 mostraram boa foto sensibilidade, com a corrente elétrica respondendo imediatamente à excitação independente da energia, além de um rápido decaimento com relação ao valor excitado. Fora isto, medidas de decaimento da corrente foto induzida, realizadas em atmosfera de O2, indicaram que o decaimento se torna ainda mais rápido na presença do gás, estando associado ao aprisionamento de portadores de carga pelas moléculas adsorvidas na amostra, além da recombinação dos pares elétron-buraco. Com relação à heteroestrutura, quando a condução ocorre preferencialmente no TiO2, a amostra apresenta resultados muito similares às dos filmes de TiO2, tendo uma rápida resposta à excitação com fonte de luz acima do bandgap do TiO2 e um rápido retorno para seu estado de equilíbrio, no escuro. Entretanto, em atmosfera gasosa, o decaimento se torna muito mais rápido, o que também está associado ao aprisionamento de portadores pelas moléculas adsorvidas de gás. Porém, o aumento na taxa com que isto acontece, está relacionado à formação da heteroestrutura e às compensações de carga na interface, que podem ocorrer quando a excitação utiliza comprimento de onda adequado. A configuração lado a lado da heteroestrutura mostrou emissão Poole – Frenkel para tensões maiores que 40V, e quando irradiada com luz que simula o espectro solar apresentou uma região de resistência negativa para algumas potências de excitação que pode estar ligada ao aprisionamento de elétrons na interface. Desta forma, este trabalho visa trazer uma contribuição importante à compreensão do mecanismo de transporte elétrico dos materiais estudados. Por fim, pode-se dizer que os materiais aqui estudados podem ser aplicados como sensores de gás ou dispositivos retificadores/amplificadores desde que seja escolhida a melhor configuração para a aplicação desejada. / This work presents a study of the optical, electrical and morphological characterization of TiO2 thin films, deposited individually or coupled with SnO2 doped with 4at%Sb, forming a heterostructure. Both sort of samples, TiO2 and the heterostructure were studied in thin film form, deposited by sol-gel-dip-coating, and, in the case of TiO2, it was relevant the analysis of samples also in the form of pellets form (pressed powders). With regards to SnO2:4%Sb, this work brings a literary revision of its principal properties, trying to present a general overview, for the better understanding of the phenomena that occur in the heterostructure. The results of TiO2 pellets indicates a partial anatase/rutile phase transition to thermal annealing between 500 and 1000ºC, confirmed by the photoluminescence that presented bands related to anatase or rutile, depending the utilized processing. TiO2 films showed fair photo-sensibility, with immediate response on the electric current to light excitation, independent on the utilized energy, along with fast decay in relation to the excited value. Moreover, photo-induced current decay measurements, performed in O2 atmosphere, indicated that the decay becomes faster in gas presence, being associated to charge carriers trapping by the adsorbed molecules on sample, besides the electron-hole recombination. Concerning the heterostructure, when the conduction occurs preferentially in TiO2 layer, the sample shows very similar results to the TiO2 films, with a fast response to light excitation above the TiO2 bandgap and fast return to the equilibrium state, in dark. However, in gas atmosphere, the decay becomes much faster, which is also associated to the carriers trapping by the gas adsorbed molecules. Nevertheless, the rate increase in this phenomenon is related to the heterostructure formation and the charge compensations at the interface, which may occur when appropriate wavelength is used for excitation. The side by side heterostructure sample showed a Poole – Frenkel emission to bias higher than 40V, and presented a negative resistance region to some irradiation power when illuminated with solar light that can be associated to electrons trapping at the interface. In summary, this work aims to bring a contribution related to the electric transport mechanism of the studied materials. The materials investigated here may be applied in gas sensors or rectifiers/amplifiers devices, according the sample configuration. / CAPES: 1578735

Submitted by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2016-01-06T17:51:26Z No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) Disserta??o Completa Times New Roman - Com Assinatura da Ban.pdf: 4476480 bytes, checksum: 309e034f51cd7605224651743ecee1cd (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2016-01-07T12:06:06Z (GMT) No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) Disserta??o Completa Times New Roman - Com Assinatura da Ban.pdf: 4476480 bytes, checksum: 309e034f51cd7605224651743ecee1cd (MD5) / Made available in DSpace on 2016-01-07T12:06:06Z (GMT). No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) Disserta??o Completa Times New Roman - Com Assinatura da Ban.pdf: 4476480 bytes, checksum: 309e034f51cd7605224651743ecee1cd (MD5) Previous issue date: 2012 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (Capes) / Filmes finos de di?xido de estanho dopados com antim?nio foram confeccionados pelo m?todo de deposi??o t?rmica sobre micro tela de a?o ASTM 316 objetivando a confec??o de anodos perme?veis a fluido para uso em reatores filtro-prensa. Os ?xidos nas formas de filmes suportados e de p? foram investigados pelas t?cnicas de energia dispersiva de raios-X (EDX), difratometria de raios-X (DRX) e microscopia eletr?nica de varredura (MEV). O estudo de EDX revelou que a raz?o efetiva Sb/Sn nos filmes ? maior que a nominal, enquanto que o DRX revelou que o SnO2 est? presente na forma da estrutura da cassiterita, que n?o h? presen?a de picos relacionados a ?xidos de antim?nio e que o aumento da concentra??o de Sb leva a uma diminui??o da cristalinidade dos filmes. O estudo de MEV revelou que os filmes apresentam estrutura compacta e n?o-porosa. A caracteriza??o eletroqu?mica dos anodos 316/Sb-SnO2 conduzida numa c?lula do tipo eletr?lito polim?rico s?lido (EPS) empregando-se a membrana Nafion? 117 da Dupont revelou a partir da voltametria c?clica e das curvas de polariza??o que o sobrepotencial para a rea??o de desprendimento de oxig?nio (RDO) aumenta com a concentra??o de antim?nio. O estudo envolvendo a an?lise da durabilidade dos anodos conduzido em condi??es galvanost?ticas (20 mA cm-2) revelou que a vida ?til do anodo aumenta com a concentra??o de Sb passando por um ponto de m?ximo. O anodo 316/Sb-SnO2 alojado em c?lula do tipo EPS na condi??o de ?zero-gap? e na aus?ncia de eletr?litos l?quidos foi aplicado na degrada??o eletroqu?mica do corante t?xtil Cibacron? Marinho F-4G considerado como poluente modelo. A cin?tica de descolora??o seguiu o modelo de pseudo-primeira ordem representativo do controle difusional atrav?s da microestrutura do ?nodo sob influ?ncia da turbul?ncia causada pelo desprendimento de oxig?nio. Foi verificada uma descolora??o superior a 90% e uma degrada??o do composto parental maior que 50% ap?s 3,5 h de eletr?lise. A an?lise das curvas cronopotenciom?tricas indicou que a desativa??o dos anodos ? fortemente influenciada pela disponibilidade dos radicais hidroxilas adsorvidos na superf?cie do eletrodo. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2012. / ABSTRACT Thin films of tin dioxide doped with antimony were prepared by the thermal decomposition method onto a stainless steel fine mesh (ASTM 316) in order to obtain a fluid permeable anode for application in filter-press reactors. Films and powders of Sb-SnO2 were investigated using the energy dispersive X-ray (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The EDX revealed that the effective Sb/Sn molar ratio in films is greater than the nominal composition, while the XRD has revealed that SnO2 is present in the crystalline form of the cassiterite structure. In addition, it was verified the absence of peaks accounted for the antimony oxides even for higher amounts of Sb, while the addition of Sb lead to a decrease in the film crystallinity. SEM images showed that the thin films are rather compact. The electrochemical characterization of the fluid permeable anode composed of 316/Sb-SnO2 was carried out in an SPE cell using the Nafion? 117 membrane as the electrolyte. Cyclic voltammograms and polarization curves showed the overpotential for the oxygen evolution reaction (OER) increases upon increasing the antimony concentration. The endurance test carried out under galvanostatic conditions (20 mA cm-2) has revealed that the anode service life increases upon increasing the Sb concentration passing through a maximum. The 316/Sb-SnO2 anode housed in an SPE cell in the zero-gap condition and in the absence of liquid electrolytes was applied on degradation of the Cibacron? Marinho F-4G dye, considered as the pollutant model. Discoloration kinetics was described by the pseudo-first order model describing the diffusion control across the anode microstructure under the influence of the turbulence caused by the OER. A discoloration percentage higher than 90% and a degradation percentage of the parental compound greater than 50% were both achieved after 3.5 h of electrolysis. Analysis of the chronopotentiometric curves indicated the anode deactivation is considerable effected by the availability of the hydroxyl radicals adsorbed on the anode surface.

Submitted by Miguel Henrique Boratto null (miguelhboratto@gmail.com) on 2018-03-24T19:01:03Z No. of bitstreams: 1 M H Boratto - Tese doutorado.pdf: 5163282 bytes, checksum: 63d587fd9642d9da4a7eb0173248c3e9 (MD5) / Approved for entry into archive by Maria Marlene Zaniboni null (zaniboni@bauru.unesp.br) on 2018-03-26T16:38:12Z (GMT) No. of bitstreams: 1 boratto_mh_dr_bauru.pdf: 5163282 bytes, checksum: 63d587fd9642d9da4a7eb0173248c3e9 (MD5) / Made available in DSpace on 2018-03-26T16:38:12Z (GMT). No. of bitstreams: 1 boratto_mh_dr_bauru.pdf: 5163282 bytes, checksum: 63d587fd9642d9da4a7eb0173248c3e9 (MD5) Previous issue date: 2018-02-09 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho compreende o estudo de óxidos semicondutores (Sb:SnO2 e TiO2) e isolantes (ZrO2) obtidos via sol-gel, e a investigação de suas propriedades, de modo a avaliar estes materiais como alternativa para aplicação em dispositivos eletrônicos, tais como Capacitor Metal-Isolante-Metal (MIM), transistores de filmes finos (TFT) e memristores. Os filmes finos de SnO2 foram obtidos através de duas soluções com diferentes tempos de envelhecimento. Os filmes finos de ZrO2 também foram obtidos a partir de duas soluções, produzidas por dois métodos distintos, não-alcoóxido e polimérico. A deposição dos filmes finos foi realizada por dip- e spin-coating, e as caracterizações foram realizadas através das técnicas de DRX, AFM, MEV, Microscopia Confocal, EDX, RBS, TG/DSC, Espectroscopia no espectro UV-Vis, Voltametria Cíclica e Espectroscopia de Impedância, afim de melhor compreender as relações entre propriedades morfológicas e estruturais dos filmes e suas propriedades elétricas. As características de filmes finos de Sb:SnO2 e ZrO2 foram analisadas em dispositivos TFT e MIM, respectivamente. Alternativamente, TiO2 foi acoplado ao Sb:SnO2 e juntos foram aplicados em memristores devido às propriedades elétricas da junção destes semicondutores. Os resultados das análises dos diferentes tipos de dispositivos eletrônicos investigados neste trabalho são discutidos considerando suas diversas características, e são também propostas opções de possíveis melhorias para tais dispositivos tornarem-se comparáveis aos estados-da-arte já existentes. / This work comprises the study of oxide semiconductors (Sb-doped SnO2 and TiO2) and insulating materials (ZrO2) obtained by sol-gel, and the investigation of their properties, aiming to evaluate these materials as alternative for application in electronic devices, such as Metal-Insulator-Metal (MIM) capacitors, Thin Film Transistors (TFT), and Memristors. The SnO2 thin films were obtained by two solutions with different aging times. The ZrO2 thin films were also obtained by two solutions, synthesized from two distinct methods, non-alkoxide and polymeric. The thin film deposition occurred mainly by dip- and spin-coating techniques, and the characterizations were performed through the techniques of XRD, AFM, SEM, Confocal Microscopy, EDX, RBS, TG/DSC, UV-Vis Spectroscopy, cyclic voltammetry and Impedance spectroscopy, in order to better understand the relations between the morphological and structural properties of these films and their electrical properties. The properties of Sb:SnO2 and ZrO2 thin films were analyzed in TFT and MIM devices, respectively. Alternatively TiO2 was coupled with Sb:SnO2 and applied to Memristors due to the electrical properties of this semiconductor junction. The analysis and results of the different devices investigated in this work are discussed considering their several characteristics, and it is also suggested options for possible enhancements for these devices become comparable to existent state-of-the-art devices.

Nowadays, low carbon economy becomes a significant topic over the world. Due to the decreasing amount of fossil energy source and the worsening environmental pollution, traditional energy sources should be transferred to renewable energy sources. A transition to renewable energy will require radical changes to systems and technologies for energy storage. Lithium ion (Li-ion) batteries are now considered as the most important electrochemical energy source for portable devices, electrical vehicles and expected to be used in grid electrical energy storage. Beside on Li-ion batteries, sodium ion (Na-ion) batteries are another promising energy source, which have the advantages in cost, safety and environmental factors, and they could be used for stationary energy storage systems and large vehicles. Tin-based nanocomposites are promising to replace the traditional graphite for Li-ion batteries to achieve a higher battery performance. In 2005, Sony Corporation launched the first Sn-based anode Li-ion batteries (Nexelion) to obtain a 50% increase in volumetric capacity over the conventional battery, which marked Li-ion batteries to enter into a new cutting edge. However, Sn-based materials faced with challenges. The battery performance was limited by a low cycling life and low rate performance, and methods should be devised to overcome these shortcomings. In this thesis, SnO2-based nanocomposites, including the graphene-SnO2, the carbon-coated graphene-SnO2 and the carbon-coated nanostructured SnO2 have been prepared and investigated as anodes for Li-ion and Na-ion batteries. The microstructure, electrochemical performances and even the degradation mechanisms have been investigated as the effects for different composite materials. Chapter 4 reports an amorphous carbon coated graphene-SnO2 composite which exhibited an enhanced cycling stability. In previous researches, the performance enhancements of that type of materials were commonly attributed to the carbon coating enhancing the electronic conductivity. However, it is found that the carbon coating deeply relates to the microstructure stability of the active materials, the performance enhancement can be attributed to the enhancement of structural stability. Chapter 5 reports same composites with various graphene to amorphous carbon mass ratios. In this chapter, we try to find out the optimized composition and understanding the different roles of graphene and amorphous carbon in that type of composites. It is found that an optimised graphene to carbon mass ratio can effectively enhance the structural stability and the electrode conductivity. Chapter 6 reports a carbon-coated flower-like nanostructured SnO2 for Na-ion battery application, which has been demonstrated to have a high reversible capacity and high rate performance. The carbon coating is found to help in the formation of a high quality solid electrolyte interface (SEI) layer on the surface of the active materials. These researches focus on modifying SnO2 and SnO2-based materials by carbon coating technologies, which aim to develop novel electrode materials to obtain a better battery performance for Li-ion and Na-ion batteries.