Orientador: Celio Pasquini / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-06T01:48:01Z (GMT). No. of bitstreams: 1 Gonzaga_FabianoBarbieri_D.pdf: 2179229 bytes, checksum: 3032668f50c4141f4589cdc9b2ceda23 (MD5) Previous issue date: 2006 / Doutorado / Quimica Analitica / Doutor em Ciências

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Orientador: Célio Pasquini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-21T15:29:23Z (GMT). No. of bitstreams: 1 Vieira_FranciscoSenna_M.pdf: 2577567 bytes, checksum: 88e8b413d192407a39a0f0d341572223 (MD5) Previous issue date: 2012 / Resumo: A autoxidação de lipídeos é uma das principais causas de degradação de óleos e gorduras. Este processo gera uma série de compostos indesejáveis, tais como, peróxidos, hidroperóxidos e ácidos carboxílicos de cadeia curta. A determinação da estabilidade oxidativa de um óleo, é, portanto, essencial para estimar o tempo de prateleira - um parâmetro importante para a indústria alimentícia. Para quantificar o grau de oxidação de um óleo, uma série de parâmetros pode ser utilizada, como os índices de peróxido e de anisidina, o teor de dienos conjugados, dentre outros. Métodos acelerados foram desenvolvidos para a estabilidade oxidativa - uma medida da variação do grau de oxidação ao longo do tempo -, em particular o método Rancimat. Nele, uma amostra de cerca de 3 g de óleo e aquecida em temperaturas na faixa de 100-130 °C, e um fluxo de ar constante e passado através da amostra e carreado para um recipiente contendo água deionizada. O monitoramento da condutividade elétrica desta solução permite identificar o período de tempo necessário para que a taxa de formação de ácidos carboxílicos de cadeia curta se torne significativa. Este tempo é denominado tempo de indução (TI), e corresponde ao índice de estabilidade oxidativa (OSI - Oxidative Stability Index) do óleo. A espectroscopia de emissão no infravermelho próximo (NIRES), por outro lado, permite o monitoramento de hidroperóxidos, devido ao aumento e alargamento de uma banda em 2900 nm que ocorre ao longo do processo oxidativo. Neste trabalho foi desenvolvido e avaliado um fotômetro NIRES, dedicado para a determinação de estabilidade oxidativa. No método NIRES, uma amostra de 10 mL e aquecida a uma temperatura fixa (140 - 180 °C), sendo mantido um fluxo constante de ar purificado ao redor da amostra. A emissividade do óleo em 2850 e 2675 nm e continuamente monitorada com um detector de PbS, sendo a seleção dos comprimentos de onda realizada por dois filtros de interferência. A formação de hidroperóxidos ocasiona um aumento significativo da emissividade a 2850 nm, permitindo a determinação de TI de forma análoga ao método Rancimat.. O equipamento construído apresenta uma série de vantagens com relação ao método Rancimat, tais como: rapidez na análise, simplicidade operacional, menor consumo de amostra e a possibilidade de determinar a estabilidade oxidativa em temperaturas de fritura (140-180 °C). A precisão do método NIRES encontrada é equivalente à precisão do método Rancimat, e existe uma correlação entre eles (R = 0,90). / Abstract: Lipid autoxidation is the main cause of fats and oils deterioration. This process generates a series of undesirable compounds, such as hydroperoxides and low chain carboxylic acids. Thus, determination of oil fs oxidative stability is essential for estimation of the shelf life - an important parameter for the food industry. Several parameters are used for quantifying the degree of oxidation of an oil sample, such as the peroxide value, anisidine value, and conjugated dienes. Accelerated methods have been developed for measuring oxidative stability - the variation of the degree of oxidation with time -, particularly the Rancimat method. In this method, a constant air flow passes through a 3 g oil sample, heated at 110 - 130°C, and then is collected in a vessel containing deionized water. By monitoring the deionized water fs conductance, an induction time (IT) - which corresponds to the Oil Stability Index (OSI) - can be determined. On the other hand, near infrared emission spectroscopy (NIRES) allows the determination of IT by monitoring the formation of hydroperoxides. As the oil undergoes autoxidation, a band at 2900 nm becomes broader and more intense. In this work, a near infrared emission spectroscopy photometer, dedicated to determination of oxidative stability, has been developed and evaluated. In the NIRES method, a 10 mL oil sample is heated at a constant temperature (140 - 180 °C), and a purified air flow is maintained around the sample. The oil fs emissivity at 2675 and 2850 nm is continually monitored with a PbS detector, and the wavelengths are selected with two interference filters. Formation of hydroperoxides increases significantly the emissivity at 2900 nm, allowing the determination of IT in a way analogous to the Rancimat method. The developed equipment presents several advantages towards the Rancimat, including: faster analysis, lower sample consumption, operational simplicity, and the possibility of measuring oxidative stability at frying temperatures. Also, the method fs precision is equivalent to the Rancimat fs precision, and a correlation between them has been found (R = 0,90). / Mestrado / Quimica Analitica / Mestre em Química

Non-thermal plasma has a lot of ways for using in nowadays medicine. It presents many useful actions like charged particles, UV light, electric field, radicals, excited atoms and molecules. That complicated chemistry directs to uncountable synergistic interaction between cold plasma and biological systems, involve cells and tissues. This thesis is about effects of cold plasma to wound healing. Two different microwave plasma systems were used for the presented study. The first one was argon plasma torch generated by surface wave using the quartz capillary, the second one was plasma torch with reverse vortex argon flow. Diagnostics of plasma jet by optical emission spectroscopy shown the presence of active particles, which are responsible for a lot of impact of plasma treatment. Concentrations of active particles generated by plasma are dependent on conditions of plasma generation like power of generator and gas flow. For visual evidence of effects on skin caused by active particles was created simulation of skin tissue. Interaction between plasma jet and artificial skin tissue shown that UV light and temperature are not responsible for all observed effects which are noticed after plasma treatment. Some part of experiments was realized in collaboration with Medical University of Sofia in Bulgaria. The theory of positive effect to wound healing was supported by experiments based on treating artificially created wounds on laboratory mice by cold plasma. It was proved, that process of wound healing is significantly shorter after using plasma treatment in comparison with normal wound healing. Plasma treating of wound for 10 seconds in two consequent days seems like more effectively than application of plasma only one day. This Thesis was carried out as a part of international project PLASMABORDER that was supported by European commission under cohesion funds; programme INTEREG SK-CZ under contract No. 304011P709.

In order to elucidate the effects of nanostructuring on electron behavior in vanadium oxides, a suite of x-ray spectroscopy techniques was employed to comprehensively characterize the electronic structures of V2O5 and VO2 nanoparticles and compare them to their bulk counterparts. V2O5 and VO2 nanoparticle powders were characterized via PXRD, TEM, and HR-TEM to confirm size, purity, and crystallinity. Additionally, DSC and temperature-varied PXRD measurements on both VO2 samples confirmed the structural aspect of the monoclinic to rutile metal-insulator phase transition, and UV-Vis measurements allowed for Kubelka-Munk analysis on the V2O5 samples. XAS measurements enable the comparison of unoccupied conduction band states, while XES and RIXS measurements reveal occupied valence band states and the individual vanadium and oxygen PDOS below the Fermi level. XPS measurements of both core and valence band states both confirmed the valence band structure revealed by XES and also provide information on core-state energy levels. In the case of V2O5, the valence band O 2p states are upshifted in the nanoparticle sample, while the lowest V 3d conduction band states are unshifting but provide more available unoccupied states for excitation. These changes produce a shrunken bandgap in the V2O5 nanoparticles that is in line with much previous computational work, but unexpected from previous experimental results and defies the Moss-Burstein effect usually observed in V2O5. The resulting changes in band structure are attributed to a higher concentration of oxygen vacancy defects in the nanoparticle sample. Additionally, electron correlation effects in V2O5 nanoparticles are found to be enhanced relative to the bulk, likely due to added electron presence in the V 3d split-off band. In the case of VO2, dramatic changes in both the valence band and conduction band states are observed both below and above the structural phase transition temperature. These changes (lowered unoccupied conduction band states coupled with broadened and upshifted occupied valence band states) also lead to nanoparticle bandgap reduction and enhanced metallicity. The enhanced metallic nature of the VO2 nanoparticles is again attributed to the increased presence of surface oxygen vacancy defects, as well as a V2O3-like surface reconstruction. Additionally, electron correlation effects are found to be reduced in the VO2 nanoparticle samples relative to the bulk, unlike in the case of V2O5.

The main goal of this thesis was to study plasma generated by surface discharge and its application in volatile organic compound destruction. Introduction of this thesis deals with the issue of volatile organic compound. The term of volatile organic compound was defined and explained. Summary of the most important sources of volatile organic compound emissions and possible technics for their elimination was presented. This thesis drew attention on negative aspects of volatile organic compounds on human organism and on the whole environment. The problems of surface discharge and its possible application in various branches are known only few years therefore construction of plasma reactor itself was the first independent step of this work. The plasma reactor was consisted of electrode, which was created from the series of metal stripes each other separated by dielectric barrier. On the surface of the electrode, discharge was regulated and distributed. For the reason of technical limits experiment time was limited up to one minute. The experimental part describes reactor for surface discharge and other parts of apparatus in which degradation volatile organic compound was carried out. Nitrogen was used as carrier gas and it was mixed with air before entering into the reactor. Samples of compounds after degradation process were taken from reactor for the subsequent analysis. Analysis of the products proceeded in a gas chromatogram linked to mass spectrometer. The decomposition products were adsorbed in the SPME filaments or in sorption tubes. The decomposition products were analysed also through the mean of Testo 350 M/XL. This apparatus provided the information on the concentration of small molecules such as CO, H2, NO, NO2 and CxHy Hexane, cyclohexane and xylene were used as VOC examples. Analysis of GC-MS showed decomposition products of hexane, cyclohexane and xylene. The decomposition products were especially various alcohols, ketones, aldehydes and benzene compounds. The apparatus Testo 350 M/XL was unable to detect any CxHy, only large quantity of NO2. This thesis was further focused on possible factors which could have an influence on degradation of compounds, for example input power or different flow of oxygen. It was found that increasing power declined the removal efficiency. The maximum removal efficiency was 87 % for degradation of hexane at the lowest input power. Next part of this thesis was focused on diagnostics of plasma generated in the surface discharge form. The optical emission spectroscopy has been chosen as the best method for plasma characterisation. By this method, various important discharge parameters can be determined, e.g. vibration and rotation temperature. The obtained numeric value of rotation temperature was 840±80 K and vibration temperature was 1880±140 K. The obtained results may be used as a fundament for further study of VOC decomposition in surface discharge.

The present diploma thesis concerns the research of plasmachemical reduction of copper corrosion layers. The process was based on using low pressure hydrogen RF plasma in which copper samples are treated for several hours. Four series of copper corrosion layers were prepared in four different corrosion atmospheres. The first two were prepared using saturated vapors of HCl and ammonium acetate that affected copper samples for one week. The second two sets were prepared by samples dipping in HNO3 and H2SO4. EDX analysis confirms visual composition of corrosion layers – chlorides, nitrides and sulphate, respectively. The ammonium acetate produced no corrosion layers and thus this set of samples was omitted. The optical emission spectroscopy was used to find out reactions in a hydrogen RF discharge. At the first, a character of plasma without samples was taken by measuring in continuous and pulsed regime. The integral spectrum intensity (300-700 nm) and intensities of hydrogen atomic lines were observed in the dependences on hydrogen flow, power and duty cycle. After that copper samples were treaded under various conditions in continual and pulse regime, typically at pressure of 170 Pa, 200 W power and hydrogen flow rate of 10.2 ml/min. The integral OH radical spectral intensity in the range of 305 – 330 nm was used as a monitor of plasma treatment process. The experimental results showed that intensities of OH radical depended strongly on the corrosion layer kind as well as on the RF discharge mode. Reduction of corrosion layers treated in the pulsed regime was not so satisfactory then in the continuous regime probably due to lower temperature of sample during the treatment. The total supplied energy into the system was also lower in this case. The sample sputtering was observed during the reduction in continuous regime. It means the corrosion was successfully removed but the process was not stopped at that moment, so it is necessary to propose another additional monitoring process besides observing OH radicals. Our experimental results are the first step in the spread research of plasmachemical treatment of copper made archaeological artifacts.

The aim of this work is plasma diagnostic during the deposition of thin films based on organosilicone compounds. These layers have a wide range of applications mainly as protective coatings or intermediate phase in composites reinforced by glass fibers. The theoretical part of this work gives a basic fundaments of optical emission spectroscopy and mass spectroscopy and describes procedures for rotational, vibrational, and electron temperature calculations. The RF capacitive coupled discharge in configuration with planar electrodes was used with tetravinylsilane (TVS) organosilicone monomer in this study. The optical emission spectroscopy and mass spectroscopy were applied for the plasma diagnostics. The deposition process was carried out in continuous regime with applied power of 20, 25, 40, 50, 60, and 70 W, some experiments were done also in pulsed regime with duty cycle 1:1, 1:4 and 1:9 at fixed power of 50 W and 10 W when discharge was on. The atomic lines of hydrogen Balmer series and many rotational lines of molecular hydrogen were identified in the spectra. Besides them, the molecular bands of SiH, CH and C2 species were observed. The rotational temperature calculated from 0-0 CH band was in the range of 600 – 1000 K depending on the discharge conditions. The electron temperature in the range of 3600-7500 K was calculated from hydrogen atomic lines. In situ mass spectra collected simultaneously with optical emission spectra showed TVS monomer fragmentation increase with the increase of applied power in continuous regime. This result well correlated with OES in case of CH radical and hydrogen species, the other particles were mainly non-measurable by emission spectroscopy. The same results were also obtained with respect to the duty cycle parameter. The presented results clearly demonstrated the increase of monomer fragmentation with the increase of mean applied discharge power. Determination of prepared layer properties is a subject of other works and their relation to the plasma parameters will be a subject of further studies.

The main topic of this Diploma thesis is the application of low-pressure low-temperature hydrogen plasma for the treatment model samples of rusted brass. Plasmachemical treatment of metallic artifacts is a relatively new way how to remove corrosion of artifacts. The temperature of an object should not exceed 150 °C during the treatment. Corrosion layers were prepared in an ammoniac corrosion atmosphere. The corrosion formation took two weeks. Energy Dispersive X-ray Microanalysis has shown that the corrosion layer was formed by carbon, oxygen, copper, zinc, and lead. The corrosion layers were blue-colored with white crystals on the surface. Except those two colors, brown color was observed on corrosion layers, too. The plasma reactor was a quartz tube with outer copper electrodes and supplied by the RF source of 13.54 MHz. The reactive atomic hydrogen was formed in plasma discharge. This atomic hydrogen reacted with the corrosive layer containing oxygen. This reaction created an unstable OH radical, which emitted light in the region of 305–320 nm. This radiation was detected by the optical emission spectroscopy and it was applied as process monitoring quantity. Rotational temperature and intensity of OH radicals were determined from obtained data. The sample temperature was measured by thermocouple installed inside the sample volume. Rusted samples were treated by low-pressure low-temperature hydrogen plasma. 16 samples were treated at different conditions – plasma power was 100 W, 200 W, 300 W, and 400 W at continuous mode and pulse mode with duty cycle of 25 %, 50 %, and 75 %. The pressure was between 140–160 Pa at hydrogen flow rate of 50 sccm. Samples after plasmachemical treatment were grey colored with white crystals on their surface. Corrosion layers were removed by spatula. The corrosion layers of some samples were easy removable, some others were difficult. Energy Dispersive X-ray Microanalysis, which was carried out after the treatment of 2 selected samples (400 W, 50% pulse mode and 400 W, 75% pulse mode), showed different amounts of carbon, oxygen, copper, zinc, and lead compared to the rusted sample. Other elements in the treated layer were silicon, sulfur, chlorine, and fluorine.

This diploma thesis is focused to the plasma chemical reduction of model corrosion layers prepared on bronze samples. Bronze was the main material for production of the subjects in Bronze Age. First, it was very rare, and therefore was used only for making jewellery and other decorative subjects. Later, the objects of daily use and weapons were produced of bronze. These objects are found and it is necessary to restore him and preserve the cultural heritage for future generations. The research and the optimalization of plasmochemical reduction of model corrosion layers on bronze samples contributes to this. A metallographic grinder was used to create a defined surface, first with the sandpaper P 280 and then after sample 90 degree rotation with the sandpaper P 600. This ensured uniform surface at all bronze samples that is necessary to provide the same corrosion conditions. The grinded samples were washed by ethanol and dried by hot air stream. To prevent contact with the surrounding atmosphere and successive initiation of corrosion, the samples were stored in lockable polyethylene bags. This step was followed by the preparation of model corrosion layers. Hydrochloric and sulfuric acids were chosen as corrosive environments. Petri dish containing 20 ml of the selected acid was placed at the bottom of the desiccator. Samples were placed to the ceramic grate, over the dish, and they were corroded (in vapours of hydrochloric acid for 34 days and in vapours of sulfuric acid for 27 days). The corroded samples were treated using low-pressure hydrogen plasma excited by RF generator. Treatment of samples was carried out in quartz cylindrical reactor (length of 90 cm, inner diameter 9.5 cm) with copper electrodes placed outside. The pressure in the reactor was ranged around 160 Pa at hydrogen flow rate of 50 sccm during the experiments. The continuous and pulse modes (duty cycle of 25%, 50% or 75%) at peak power of 50–300 watts were used for the treatment of 90 minutes duration. The plasma treatment was monitored by optical emission spectroscopy of OH radical using compact Ocean Optics HR4000 spectrometer. Its integral intensity is proportional to the corrosion layer removal. The rotational temperatures of plasma were calculated using selected OH rotational lines, too. The sample temperature during the treatment was measured by thermocouple installed inside the additional non-corroded samples. The reduction of corrosion layer is successful when the maximum of relative intensity of OH radicals is produced and follow gradual decline. The samples which corroded in vapours of sulphuric acid and were treated in pulse modes with duty cycle of 25 % or with delivered power of 50 W has produced no maximum. To the remain samples the maximum although were observed, but reduced corrosion products on the surface were very cohesive. The maximum of relative intensity of OH radicals was observed at all samples corroded in vapours of hydrochloric acid. But there is problem with temperature of sample during experiment. The samples which layer of corrosion product was after experiment incoherent produced the layer of deposit tin. This effect formation at a higher temperature of sample during experiment and therefore with greater deliver energy.