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Orientador: Elidiane Cipriano Rangel / Banca: José Daniel Biasoli de Mello / Banca: Lúcia Vieira Santos / Banca: Roberto Martins de Souza / Banca: Steven Frederick Durrant / O programa de Pós graduação em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi da UNESP / Resumo: Neste trabalho foi investigado o efeito protetivo produzido pela deposição de um filme de Carbono Amorfo Hidrogenado (a-C;H) sobre a a superfície de uma ferramenta de conformação coberta com Nitreto de Titânio (TiN). A força necessária para conformar o material é relativamente alta, em torno de algumas toneladas. Os Filme de a-C;H foram aplicados com o objetivo de reduzir o atrito entre as superfícies da ferramentas de conformação e do material a ser conformado, podendo também gerar um ganho pela redução ou eliminação da lubrificação aplicada na fita na forma de fosfato de zinco ou de óleo de repuxo. As amostras foram construídas a partir do aço Ferramenta AISI M2, através dos processos de usinagem mole, tratamento térmico, retifica a lapidação com subseqûente aplicação da camada de TiN através do processo PVD (Physical Vapor Deposition). Também foi utilizado como subtrato discos de aço AISI M2 sem a camada TiN. As amostras foram inicialmente limpas em um processo de lavagem po ultra-som e subseqüentemente por uma procedimento a plasma. Os filmes foram depositados utilizando-se plasmas de baixas temperaturas de misturas de hidrocarbonetos e gases nobres. Foi utilizada a técnica híbrida de implantação iônica e deposição por imersão em plasmas (IIDIP), aplicando-se pulsos de alta tensão negativa à amostras para promover a deposição mediante a implantação iônica. Neste caso, o acetileno (C2H2) diluído em argônio foi utilizado como mistura precursora da formação do filme. Foi investigado o efeito da amplitude dos pulsos de polarização e da pressão dos gases do plasma nas propriedades dos filmes. As espectroscopias no infravermelho e Raman foram empregadas para se avaliar a composição química e a microestrutura dos filmes. Verificou-se nos espectros de infravermelho que... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this study, the protective effect by the application of a Hydrogenated Amorphous Carbon (a-C;H) film on the surface of a forming tool containing a titanium nitrite (TiN) layer was investigated. The required force to forming the material is relatively high, around a few tons. The a-C;H films were applied to reduce the friction coefficient between the surface of the forming tool and the raw material, also generating the possibility of the reduction or olimination of the lubrication applied to the tape surface in the form of zinc phosphate and drawing oil. The samples were produced from AISI M2 steel, using soft machining processes, heat treatment, grinding and polishing with subsequent application of the IiN layer by PVD (Physical Vapor Deposition). To permit comparison, AISI M2 steel without the TiN layer was also used as a substrate. The samples were initially cleaned in ultrasonic baths ans subsequently by plasma ablation. Low temperature plasmas of hydrocarbon and noble gas mixtures were used to deposit the films. The hibrid technique of plasma immersion ion implantation and deposition (PIIID) was used, applying high voltage negative pulses to the samples to promote deposition under ion bombardment. Acetylene (C2H2) diluted in argon was used as the gas mixture for film formation. The effect of the pulse magnitude and plasma pressure on the properties of the films, were studied. Infrared and Raman spectroscopies were employed to evaluate the film chemical composition and microstructure. Via the infrared spectra was observed a decrease in the C-H and O-H band intensities with increasing pulse magnitude, but a rise in the gas pressure caused the intensity of C-H bands to increase. Raman spectra of all the films exhibited strong photoluminescence, indicating a significant hydrogen content. The receptivity on the films to water... (Complete abstract click electronic access below) / Mestre

Partially hydrogenated oil (PHO) has no longer GRAS status. However, PHO is one of the important ingredients in bakery and confectionary industry and therefore the food industry is seeking for an alternative fat to replace PHO. Waxes have shown promise to fulfill that demand because of its easy availability and cheap in price. Waxes with high melting points (> 40 °C) help in the crystallization process when mixed with low melting point oils. A crystalline network is formed in this wax/oil crystallization process where liquid oil is entrapped in wax crystal network. A new material is formed which is neither completely solid nor completely liquid; it’s called semisolid material. This wax/oil semisolid material is formed physically; there are no chemical processes or treatments involved. This material has a potential use in the lipid industry due to its resemblance to the properties of commercial margarine or similar lipids. BW has shown softer crystalline network formation compared to SFW and RBW. It is understood that presence of higher wax ester in SFW and RBW leads to stronger crystalline material formation. Blending waxes of different chemical composition (e.g. BW: wax ester, hydrocarbon, fatty acids, di-esters, hydroxyl esters. RBW: 100% wax ester) shows differences in physical characteristics at different blending proportions. HIU technology helps in delaying phase separation of crystals in low concentration (0.5 and 1% wt. basis) of wax/oil system. Our overall wax crystallization study has shown that there are different physical characteristics of wax/oil semi-solid system based on different parameters and processing conditions such as wax concentration, wax and oil type, cooling rate, storage temperature, high intensity ultrasound. The hypothesis of this dissertation is that chemical composition of waxes and vegetable oils and also processing conditions affect wax crystallization and physical properties of wax/oil materials.

Abstract Silicon carbide is a versatile material amenable to variety of applications from electrical insulation to surface passivation, diffusion-barrier in optoelectronic and high-frequency devices. This research presents a fundamental study of a-SiC:H films with variable stoichiometries deposited using novel technique, DC saddle-field plasma-enhanced chemical-vapour deposition, a departure from conventional RF PECVD commonly used in industry. DCSF PECVD is an alternative technique for low temperature large area deposition. Stoichiometric a-SiC:H obtained by fine-tuning precursor gas mixture. Annealing up to 800oC showed no significant change in elemental composition; particularly indicating thermal stability at stoichiometry. Ellipsometry showed wide range of optical gaps whose maximum surpasses values reported in literature. Refractive index measured and change in values studied as function of increasing carbon content in the films. Also attainment of very smooth surface morphology for stoichiometric a-SiC:H films reported. Surface roughness of 1 nm rms demonstrated for films grown at temperature as low as 225oC.

Abstract Silicon carbide is a versatile material amenable to variety of applications from electrical insulation to surface passivation, diffusion-barrier in optoelectronic and high-frequency devices. This research presents a fundamental study of a-SiC:H films with variable stoichiometries deposited using novel technique, DC saddle-field plasma-enhanced chemical-vapour deposition, a departure from conventional RF PECVD commonly used in industry. DCSF PECVD is an alternative technique for low temperature large area deposition. Stoichiometric a-SiC:H obtained by fine-tuning precursor gas mixture. Annealing up to 800oC showed no significant change in elemental composition; particularly indicating thermal stability at stoichiometry. Ellipsometry showed wide range of optical gaps whose maximum surpasses values reported in literature. Refractive index measured and change in values studied as function of increasing carbon content in the films. Also attainment of very smooth surface morphology for stoichiometric a-SiC:H films reported. Surface roughness of 1 nm rms demonstrated for films grown at temperature as low as 225oC.

Made available in DSpace on 2014-06-11T19:30:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-22Bitstream added on 2014-06-13T19:47:02Z : No. of bitstreams: 1 martinatti_jf_me_bauru.pdf: 2350679 bytes, checksum: a1dd65245ad53ffe2624e08e4b7e9587 (MD5) / Neste trabalho foi investigado o efeito protetivo produzido pela deposição de um filme de Carbono Amorfo Hidrogenado (a-C;H) sobre a a superfície de uma ferramenta de conformação coberta com Nitreto de Titânio (TiN). A força necessária para conformar o material é relativamente alta, em torno de algumas toneladas. Os Filme de a-C;H foram aplicados com o objetivo de reduzir o atrito entre as superfícies da ferramentas de conformação e do material a ser conformado, podendo também gerar um ganho pela redução ou eliminação da lubrificação aplicada na fita na forma de fosfato de zinco ou de óleo de repuxo. As amostras foram construídas a partir do aço Ferramenta AISI M2, através dos processos de usinagem mole, tratamento térmico, retifica a lapidação com subseqûente aplicação da camada de TiN através do processo PVD (Physical Vapor Deposition). Também foi utilizado como subtrato discos de aço AISI M2 sem a camada TiN. As amostras foram inicialmente limpas em um processo de lavagem po ultra-som e subseqüentemente por uma procedimento a plasma. Os filmes foram depositados utilizando-se plasmas de baixas temperaturas de misturas de hidrocarbonetos e gases nobres. Foi utilizada a técnica híbrida de implantação iônica e deposição por imersão em plasmas (IIDIP), aplicando-se pulsos de alta tensão negativa à amostras para promover a deposição mediante a implantação iônica. Neste caso, o acetileno (C2H2) diluído em argônio foi utilizado como mistura precursora da formação do filme. Foi investigado o efeito da amplitude dos pulsos de polarização e da pressão dos gases do plasma nas propriedades dos filmes. As espectroscopias no infravermelho e Raman foram empregadas para se avaliar a composição química e a microestrutura dos filmes. Verificou-se nos espectros de infravermelho que... / In this study, the protective effect by the application of a Hydrogenated Amorphous Carbon (a-C;H) film on the surface of a forming tool containing a titanium nitrite (TiN) layer was investigated. The required force to forming the material is relatively high, around a few tons. The a-C;H films were applied to reduce the friction coefficient between the surface of the forming tool and the raw material, also generating the possibility of the reduction or olimination of the lubrication applied to the tape surface in the form of zinc phosphate and drawing oil. The samples were produced from AISI M2 steel, using soft machining processes, heat treatment, grinding and polishing with subsequent application of the IiN layer by PVD (Physical Vapor Deposition). To permit comparison, AISI M2 steel without the TiN layer was also used as a substrate. The samples were initially cleaned in ultrasonic baths ans subsequently by plasma ablation. Low temperature plasmas of hydrocarbon and noble gas mixtures were used to deposit the films. The hibrid technique of plasma immersion ion implantation and deposition (PIIID) was used, applying high voltage negative pulses to the samples to promote deposition under ion bombardment. Acetylene (C2H2) diluted in argon was used as the gas mixture for film formation. The effect of the pulse magnitude and plasma pressure on the properties of the films, were studied. Infrared and Raman spectroscopies were employed to evaluate the film chemical composition and microstructure. Via the infrared spectra was observed a decrease in the C-H and O-H band intensities with increasing pulse magnitude, but a rise in the gas pressure caused the intensity of C-H bands to increase. Raman spectra of all the films exhibited strong photoluminescence, indicating a significant hydrogen content. The receptivity on the films to water... (Complete abstract click electronic access below)

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It has been debated that among all the renewable energy alternatives, only solar energy offers sufficient resources to meet energy demands. Silicon thin film solar cells are at the frontier of commercial solar technology. Hot wire chemical vapour deposition (HWCVD) is the technique of choice for silicon thin film deposition due to the absence of ion bombardment and its independence toward geometry or electromagnetic properties of the substrate, as seen by plasma enhanced chemical vapour deposition (PECVD). With the implementation of nanostructures in a multi-band gap tandem solar cell, considerable improvement has been achieved over the single junction solar cells. Defect assisted tunnelling processes at the junctions between individual solar cells in a tandem structure solar cell largely affect the efficiency of these solar cells. In this contribution, the investigation toward the improvement of silicon thin films for tandem solar cell application is initiated. This study reports on the effects of hydrogen dilution and deposition time on six silicon thin films deposited at six specific deposition regimes. The thin film properties are investigated via X-Ray diffraction analysis, Raman spectroscopy, Fourier transform infra-red spectroscopy, elastic recoil detection analysis, scanning and transmission electron microscopy and UV-visible spectroscopy. This investigation revealed the dominating etching effect of atomic hydrogen with the increase in hydrogen dilution and a bonded hydrogen content (CH) exceeding 10 at.% for each of the six thin films. The optically determined void volume fraction and static refractive index remain constant, for each thin film, with the change in CH. A new deposition procedure, utilising the deposition conditions of the previously investigated thin films, is performed by HWCVD to deposit two silicon thin films. This deposition procedure involved either increasing (protocol 1) or decreasing (protocol 2) hydrogen dilution during deposition. Structural and optical variation with depth was observed for the dynamically deposited silicon thin films, with nano-voids existing across the entire cross section and bond angle variations which are indicative of good structural order. The optical absorption curves differ for the two silicon thin films whereas the optical density remains constant for both. / >Magister Scientiae - MSc

>Magister Scientiae - MSc / This study reports on the effects of hydrogen dilution and deposition time on six silicon thin films deposited at six specific deposition regimes. The thin film properties are investigated via X-Ray diffraction analysis, raman spectroscopy, fourier transform infra-red spectroscopy, elastic recoil detection analysis, scanning and transmission electron microscopy and UV-visible spectroscopy. This investigation revealed the dominating etching effect of atomic hydrogen with the increase in hydrogen dilution and a bonded hydrogen content (CH) exceeding 10 at.% for each of the six thin films. The optically determined void volume fraction and static refractive index remain constant, for each thin film, with the change in CH

Nesta tese discorremos sobre crescimento e caracterização de filmes finos de carbeto de silício amorfo hidrogenado (a-Si1-xCx:H) crescidos por deposição química de vapor assistida por plasma (PECVD). Os filmes foram depositados a partir de misturas de silano, metano e hidrogênio, no regime de plasma faminto por silano. Amostras depositadas nessas condições possuem uma maior concentração de ligações Si-C, ou seja, melhor coordenação entre átomos de Si e C, com menor quantidade de ligações C-Hn e Si-H, apresentando um conteúdo de hidrogênio da ordem de 20 at.%, e baixa densidade de poros. Foram analisadas e correlacionadas diversas propriedades dos filmes depositados, explorando-se a potência de rf e a diluição da mistura gasosa em hidrogênio, de forma a melhorar a ordem química, estrutural e morfológica na fase sólida. A composição dos filmes foi determinada por retroespalhamento de Rutherford e espectrometria de recuo frontal. Enfatizou-se a análise dos diferentes tipos de ligações químicas existentes no material por espectrometria no infravermelho por transformada de Fourier, o estudo das propriedades estruturais por espectroscopia de absorção de raios X na borda K do silício, e das propriedades morfológicas analisando-se os perfis de espalhamento de raios X a baixo ângulo para diferentes ligas depositadas. Foram também realizadas medidas de dureza e de microscopia eletrônica para uma amostra estequiométrica, de forma a complementar os demais dados obtidos. Filmes estequiométricos depositados nessas condições apresentam entre 80 e 90% do total de suas ligações entre átomos de Si e C e dureza Vickers de 33 GPa. Tratamentos térmicos entre 600 ºC e 1000 ºC, realizados em atmosfera inerte de N2, mostraram que filmes stequiométricos são mais estáveis frente à absorção de oxigênio. / In this work we discuss the growth and characterization of amorphous hydrogenated silicon carbide thin films (a-Si1-xCx:H) deposited by plasma enhanced chemical vapor deposition (PECVD). It was used a gaseous mixture of silane, methane and hydrogen, at the silane starving plasma regime. Samples grown at these conditions and with a very low silane flow have a larger concentration of Si-C bonds, that is, better coordination among Si and C atoms, with smaller amount of C-Hn and Si-H bonds, presenting a hydrogen content of about 20 at.%, and low density of pores. Material’s properties were correlated for the deposited films, exploring the rf power and hydrogen dilution of the gaseous mixture, aiming to improve the chemical, structural and morphological order in the solid phase. The composition of the films was determined by Rutherford backscattering and forward recoil spectrometry. The Fourier transform infrared spectrometry analysis studied the chemical bonding inside the material, X-ray absorption spectroscopy at the silicon K edge the structural properties in samples as-grown and after thermal annealing, and small angle X-ray scattering was used for the morphological characterization. The hardness was measured and transmission electron microscopy micrographs were taken for a stoichiometric sample, in order to complement the obtained data. Stoichiometric films presented a very high chemical order, having between 80 and 90% of their bonds formed by Si and C atoms and Vickers hardness of 33 GPa. Annealing processes between 600 ºC and 1000 ºC, performed in an inert N2 atmosphere, showed that stoichiometric films are more stable against oxygen absorption.