Soy flour (SF), a by-product of the soybean oil extraction processing, was investigated for its application in soy-polypropylene composites for interior automotive applications. The emphasis of this work was the understanding of this new type of filler material and the contribution of its major constituents to its thermal stability and impact properties. For this reason, reference materials were selected to represent the protein (soy protein isolate (SPI)) and carbohydrate (soy hulls (SH)) constituents of the soy flour. Additional materials were also investigated: the residue obtained after the protein removal from the soy flour which was called insoluble soy (IS), and the remaining liquid solution after acid precipitation of the proteins, containing mostly sugars and minerals, which was called soluble sugar extract (SSE). Two treatments, potassium permanganate and autoclave, were analyzed for their potential to modify the properties of the soy composite materials. An acid treatment with sulfuric acid conducted on soy flour was also considered. The soy materials were studied by thermogravimetric analysis (TGA) under isothermal (in air) and dynamic (in nitrogen) conditions. SPI had the highest thermal stability and SSE the lowest thermal stability for the early stage of the heating process. Those two materials had the highest amount of residual mass at the end of the dynamic TGA in nitrogen. The two treatments showed minimal effect on the isothermal thermal stability of the soy materials at 200 ??C. A minor improvement was observed for the autoclave treated soy materials. Fourier transformed infrared (FTIR) spectroscopy indicated that the chemical surface composition differed according to type of the soy materials but no difference could be observed for the treatments within one type of soy material. Contact angle analysis and surface energy estimation indicated differences of the surface hydrophobicity of the soy materials according to type of material and treatment. The initial water contact angle ranged from 57 ?? for SF to 85 ?? for SH. The rate of water absorption increased dramatically after the autoclave treatment for IS and SPI. Both materials showed the highest increase in the polar surface energy fraction. In general, the major change of the surface energy was associated with change of the polar fraction. After KMnO4 treatment, the polar surface energy of SF, IS and SPI decreased while SH showed a slight increase after KMnO4 treatment. A relationship between protein content and polar surface energy was observed and seen to be more pronounced when high protein containing soy materials were treated with KMnO4 and autoclave. Based on the polar surface energy results, the most suitable soy materials for polypropylene compounding are SPI (KMnO4), SH, and IS (KMnO4) because their polar surface energy are the lowest which should make them more compatible with non-polar polymers such as polypropylene. The soy materials were compounded as 30 wt-% material loading with an injection moulding grade polypropylene blend for different combinations of soy material treatment and coupling agents. Notched Izod impact and flexural strength as well as flexural modulus estimates indicated that the mechanical properties of the autoclaved SF decreased when compared to untreated soy flour while the potassium permanganate treated SF improved in impact and flexural properties. Combinations of the two treatments and two selected (maleic anhydride grafted polypropylene) coupling agents showed improved impact and flexural properties for the autoclaved soy flour but decreased properties for the potassium permanganate treated soy flour. Scanning electron microscopy of the fractured section, obtained after impact testing of the composite material, revealed different crack propagation mechanisms for the treated SF. Autoclaved SF had a poor interface with large gaps between the material and the polypropylene matrix. After the addition of a maleic anhydride coupling agent to the autoclaved SF and polypropylene formulation, the SF was fully embedded in the polymer matrix. Potassium permanganate treated SF showed partial bonding between the material and the polymer matrix but some of the material showed poor bonding to the matrix. The acid treated SF showed cracks through the dispersed phase and completely broken components that did not bind to the polypropylene matrix. In conclusion, the two most promising soy materials in terms of impact and flexural properties improvement of soy polypropylene composites were potassium permanganate treated SF and the autoclaved SF combined with maleic anhydride coupling agent formulation.

O desenvolvimento e validação de métodos analíticos é um procedimento necessário quando um método não normalizado é utilizado por um laboratório de ensaios. A validação de métodos também é um requisito específico da norma ABNT NBR ISO/IEC 17025, que determina os requisitos gerais para a competência dos laboratórios de ensaio e calibração. O objetivo da validação é demonstrar que o método analítico, nas condições em que é executado, produz resultados com a exatidão requerida. O Laboratório de Corrosão, Proteção e Reciclagem de Materiais (LACOR), da UFRGS, tem o ensaio de determinação de metais por fluorescência de raios X, acreditado pelo CGCRE/INMETRO, conforme ABNT NBR ISO/IEC 17025. O ensaio é feito usando o método de espectrometria de fluorescência de raios X por dispersão de energia (EDXRF). Este método, contudo, não é normalizado e, portanto, o mesmo foi validado, neste trabalho de pesquisa, para atender a este requisito. A validação foi feita com base no documento orientativo DOQ-CGCRE-08 e no guia EURACHEM. Os parâmetros de validação, para o ensaio quantitativo por EDXRF, que foram calculados neste trabalho são: seletividade; limite de detecção (LD) e limite de quantificação (LQ); linearidade e faixa de trabalho; veracidade de medição (tendência, erro normalizado, Z-score e comparação com método de referência) e precisão (repetibilidade, precisão intermediária e reprodutibilidade). Além disso, foi desenvolvida uma metodologia de cálculo de incerteza de medição para o ensaio por EDXRF Os resultados obtidos neste estudo demonstram que o método EDXRF, usado na determinação de metais em aços, é um método não normalizado validado e compatível com os resultados obtidos com os métodos de referência: espectrometria de fluorescência de raios X por dispersão de comprimento de onda (WDXRF), fotométricos e espectrometria de absorção atômica (AAS). Inclusive, o WDXRF é um método de referência usado em muitas normas internacionais, que descrevem métodos de análise de aços por fluorescência de raios X, como ASTM E572 ou ASTM E1085. O estudo desenvolvido nesta dissertação permitiu que o LACOR mantivesse sua acreditação no ensaio de determinação de metais por fluorescência de raios X, na avaliação do CGCRE/INMETRO, no presente ano. Outros frutos deste trabalho foram a confecção das curvas de calibração do espectrômetro NITON XL3t GOLDD+ e a revisão do procedimento de ensaio, onde esses novos conhecimentos sobre a técnica EDXRF foram aplicados. Futuramente, este trabalho pode ser usado por outros pesquisadores para desenvolver estudos em outras matrizes metálicas, como cobre, alumínio, titânio ou níquel, e, também, em outras áreas de aplicação como jóias, reciclagem de materiais metálicos ou, até mesmo, para análise elementar de resíduos retidos em membranas de troca iônica. / The development and validation of analytical methods is a required procedure when a non-standard method is used by a testing laboratory. Method validation is also a specific requirement of the ABNT NBR ISO / IEC 17025, which determines the general requirements for the competence of testing and calibration laboratories. The purpose of validation is to demonstrate that the analytical method, under the conditions in which it is performed, produces results with the required accuracy. The Corrosion, Protection and Recycling Materials Laboratory (LACOR), at UFRGS, has the X-ray fluorescence metal analysis, accredited by CGCRE / INMETRO, according to ABNT NBR ISO / IEC 17025. The test is performed using Energy Dispersive X-Ray Fluorescence spectrometry, EDXRF method. This method, however, is not standardized; therefore, it was validated in this research to meet this requirement. The validation was based on the DOQ-CGCRE-08 document and the EURACHEM guide. The method performance calculated in this study for quantitative testing by EDXRF are: selectivity; limit of detection (LOD) and limit of quantification (LOQ); linearity and working range; trueness (bias, normalized error, Z-score and comparison with reference method) and precision (repeatability, intermediate precision and reproducibility). In addition, a measurement uncertainty calculation methodology was developed for the EDXRF testing The results obtained in this study demonstrate that the EDXRF method, used in the determination in the chemical analysis of steels, is a validated non-standard method and compatible with the results obtained with the reference methods: Wavelength Dispersive X-Ray Fluorescence spectrometry (WDXRF), photometric and atomic absorption spectrometry (AAS). In addition, WDXRF is a reference method used in many international standards, which describes analysis of steels by X-ray fluorescence spectrometry such ASTM E572 or ASTM E1085. The study developed in this dissertation allowed LACOR to maintain its accreditation in the test of metal by X-ray fluorescence analysis, in the CGCRE / INMETRO audit, this year. Other fruits of this work were the preparation of calibration curves of NITON XL3t GOLDD + spectrometer and complete revision of testing procedure, where this new knowledge about the EDXRF technique was applied. In the future, this work can be used by other researchers to develop studies in other base metals such as copper, aluminum, titanium or nickel, and also in other areas of application such as jewelry, recycling of metallic materials or even for analysis elemental residues retained in ion exchange membranes.

O desenvolvimento e validação de métodos analíticos é um procedimento necessário quando um método não normalizado é utilizado por um laboratório de ensaios. A validação de métodos também é um requisito específico da norma ABNT NBR ISO/IEC 17025, que determina os requisitos gerais para a competência dos laboratórios de ensaio e calibração. O objetivo da validação é demonstrar que o método analítico, nas condições em que é executado, produz resultados com a exatidão requerida. O Laboratório de Corrosão, Proteção e Reciclagem de Materiais (LACOR), da UFRGS, tem o ensaio de determinação de metais por fluorescência de raios X, acreditado pelo CGCRE/INMETRO, conforme ABNT NBR ISO/IEC 17025. O ensaio é feito usando o método de espectrometria de fluorescência de raios X por dispersão de energia (EDXRF). Este método, contudo, não é normalizado e, portanto, o mesmo foi validado, neste trabalho de pesquisa, para atender a este requisito. A validação foi feita com base no documento orientativo DOQ-CGCRE-08 e no guia EURACHEM. Os parâmetros de validação, para o ensaio quantitativo por EDXRF, que foram calculados neste trabalho são: seletividade; limite de detecção (LD) e limite de quantificação (LQ); linearidade e faixa de trabalho; veracidade de medição (tendência, erro normalizado, Z-score e comparação com método de referência) e precisão (repetibilidade, precisão intermediária e reprodutibilidade). Além disso, foi desenvolvida uma metodologia de cálculo de incerteza de medição para o ensaio por EDXRF Os resultados obtidos neste estudo demonstram que o método EDXRF, usado na determinação de metais em aços, é um método não normalizado validado e compatível com os resultados obtidos com os métodos de referência: espectrometria de fluorescência de raios X por dispersão de comprimento de onda (WDXRF), fotométricos e espectrometria de absorção atômica (AAS). Inclusive, o WDXRF é um método de referência usado em muitas normas internacionais, que descrevem métodos de análise de aços por fluorescência de raios X, como ASTM E572 ou ASTM E1085. O estudo desenvolvido nesta dissertação permitiu que o LACOR mantivesse sua acreditação no ensaio de determinação de metais por fluorescência de raios X, na avaliação do CGCRE/INMETRO, no presente ano. Outros frutos deste trabalho foram a confecção das curvas de calibração do espectrômetro NITON XL3t GOLDD+ e a revisão do procedimento de ensaio, onde esses novos conhecimentos sobre a técnica EDXRF foram aplicados. Futuramente, este trabalho pode ser usado por outros pesquisadores para desenvolver estudos em outras matrizes metálicas, como cobre, alumínio, titânio ou níquel, e, também, em outras áreas de aplicação como jóias, reciclagem de materiais metálicos ou, até mesmo, para análise elementar de resíduos retidos em membranas de troca iônica. / The development and validation of analytical methods is a required procedure when a non-standard method is used by a testing laboratory. Method validation is also a specific requirement of the ABNT NBR ISO / IEC 17025, which determines the general requirements for the competence of testing and calibration laboratories. The purpose of validation is to demonstrate that the analytical method, under the conditions in which it is performed, produces results with the required accuracy. The Corrosion, Protection and Recycling Materials Laboratory (LACOR), at UFRGS, has the X-ray fluorescence metal analysis, accredited by CGCRE / INMETRO, according to ABNT NBR ISO / IEC 17025. The test is performed using Energy Dispersive X-Ray Fluorescence spectrometry, EDXRF method. This method, however, is not standardized; therefore, it was validated in this research to meet this requirement. The validation was based on the DOQ-CGCRE-08 document and the EURACHEM guide. The method performance calculated in this study for quantitative testing by EDXRF are: selectivity; limit of detection (LOD) and limit of quantification (LOQ); linearity and working range; trueness (bias, normalized error, Z-score and comparison with reference method) and precision (repeatability, intermediate precision and reproducibility). In addition, a measurement uncertainty calculation methodology was developed for the EDXRF testing The results obtained in this study demonstrate that the EDXRF method, used in the determination in the chemical analysis of steels, is a validated non-standard method and compatible with the results obtained with the reference methods: Wavelength Dispersive X-Ray Fluorescence spectrometry (WDXRF), photometric and atomic absorption spectrometry (AAS). In addition, WDXRF is a reference method used in many international standards, which describes analysis of steels by X-ray fluorescence spectrometry such ASTM E572 or ASTM E1085. The study developed in this dissertation allowed LACOR to maintain its accreditation in the test of metal by X-ray fluorescence analysis, in the CGCRE / INMETRO audit, this year. Other fruits of this work were the preparation of calibration curves of NITON XL3t GOLDD + spectrometer and complete revision of testing procedure, where this new knowledge about the EDXRF technique was applied. In the future, this work can be used by other researchers to develop studies in other base metals such as copper, aluminum, titanium or nickel, and also in other areas of application such as jewelry, recycling of metallic materials or even for analysis elemental residues retained in ion exchange membranes.

O desenvolvimento e aplicação de métodos analíticos na avaliação das concentrações de metais nas frações dissolvida e lábil na bacia do rio Piracicaba são de relevante importância para o estudo do comportamento químico-ambiental desses metais e para seu monitoramento, devido ao impacto das atividades antropogênicas nessa bacia. A técnica de difusão em filmes finos por gradiente de concentração (DGT, do inglês diffusive gradients in thin-films), é uma promissora ferramenta analítica de amostragem, pois permite pré-concentração, análise temporal, remoção de interferentes, avaliação lábil e amostragem in situ. A quantificação dos metais pelas técnicas de fluorescência de raios X dispersiva em energia por reflexão total (TXRF, total reflection X-ray fluorescence analysis) para amostras líquidas e da fluorescência de raios X dispersiva em energia (EDXRF, energy dispersive X-ray fluorescence) para amostras sólidas, mostram-se interessantes devido ao caráter multielementar, simultâneo e não destrutivo da análise. Neste trabalho avaliou-se a DGT para a determinação de Cr, Mn, Co, Ni, Cu, Zn e Pb em águas naturais, utilizando-se como agente ligante a membrana de celulose P 81 e como meio difusivo, o papel cromatográfico 3 MM. Calcularam-se os fatores de eluição e coeficientes de difusão para estes metais. Estudou-se o efeito da substância húmica, em diferentes concentrações, no desempenho da DGT para esses metais, e os resultados foram comparados e concordantes com as frações livre e a ligada à matéria orgânica, calculadas pelo programa Visual MINTEQ. Compararam-se o agente ligante e o meio difusivo à base de celulose, utilizados neste trabalho, com os à base de gel de poliacrilamida, empregando-se o complexante Chelex-100. Avaliou-se a homogeneidade da retenção dos analitos e do grupo ligante fosfato sobre a superfície do agente ligante. Nesses ensaios utilizaram-se soluções sintéticas contendo os analitos em pH 5,5 e força iônica 0,05 mol L-1 (ajustados com NaNO3). As determinações foram realizadas por TXRF e EDXRF. Avaliaram-se os acoplamentos DGT-SRTXRF e da DGT-EDXRF para a determinação da fração lábil de Cr, Mn, Co, Ni, Cu, Zn e Pb em amostras de água da bacia do rio Piracicaba, através de imersão em laboratório e in situ. Esses resultados foram comparados com as concentrações dissolvidas desses metais determinados pela técnica de fluorescência de raios X por reflexão total com excitação por luz síncrotron (SRTXRF, synchrotron radiation total reflection X-ray analysis). Os valores de concentrações de Mn, Cu e Zn nas frações dissolvida e lábil foram comparados com os valores máximos estabelecidos pela legislação brasileira Nas amostragens in situ, nos cinco pontos de coleta, as concentrações de Mn dissolvido e lábil foram maiores que a concentração total máxima permitida para esse elemento. Os elmentos Cr, Co, Ni e Pb, nas amostras coletadas, apresentaram-se abaixo do limite de detecção das técnicas SRTXRF (dissolvido), DGT-SRTXRF (lábil) e DGT-EDXRF (lábil). Os limites de detecção para o Cr, Mn, Co, Ni, Cu, Zn e Pb foram de 2,2 a 10 \'mü\'g L-1 na SRTXRF, de 0,21 a 3,6 \'mü\'g L-1 e de 7,2 a 24 \'mü\'g L-1 na DGT-SRTXRF e DGT-EDXRF, respectivamente / Analytical methods evaluation for metal dissolved and labile fractions determination in Piracicaba river basin is notable for metal-behavior studies in this environment as well as their monitoring due to anthropogenic activities. The diffusive gradients in thin films (DGT) is a promising sampling technique because of its pre-concentration, time-integrated, matrix interference removal, labile evaluation and in situ analytical features. The analytical techniques total reflection X-ray fluorescence (TXRF) for liquid samples and energy dispersive X-ray fluorescence (EDXRF) for solid samples analysis are advantageous due to simultaneous, multielemental and non-destructive characteristics. In this work, it was evaluated the DGT technique for Cr, Mn, Co, Ni, Cu, Zn and Pb determination in freshwater, using P 81 cellulose membrane as bind agent and 3 MM chromatographic paper as diffusive layer. Elution factors and diffusion coefficients were calculated for these metals. The humic acids effect on DGT performance was assessed and compared to free and humic acid bound metal fractions estimated by Visual MINTEQ software, in which agreement results were found. The paper-based DGT and gel-based one with Chelex-100 as bind agent were compared. The metal retention and phosphate group homogenization on P 81 membrane bind agent surface was studied. For these tests it was utilized a synthetic solution these metals containing with pH and ionic strength adjust to 5.5 and 0.05 mol L-1 (NaNO3), respectively. It was used the TXRF and EDXRF techniques for these metal quantifications. The DGT-SRTXRF and DGT-EDXRF were assessed in order to determine Cr, Mn, Co, Ni, Cu, Zn and Pb labile fractions in batch and in situ in Piracicaba river basin freshwater samples. These results were compared to their dissolved fractions by synchrotron radiation total reflection X-ray analysis, SRTXRF. The dissolved and labile Mn, Cu and Zn concentrations levels were compared to maximum allowed set by Brazilian legislation. The dissolved and labile Mn concentrations were higher than the maximum allowed in all five samples in situ sampling. Cr, Co, Ni, and Pb concentrations were lower than their limits of detection for dissolved fractions (SRTXRF) and labile ones (DGT-SRTXRF and DGT-EDXRF). The detection limits for Cr, Mn, Co, Ni, Cu, Zn and Pb were from 2.2 to 10 \'mü\'g L-1 for SRTXRF, from 0.21 to 3.6 \'mü\'g L-1 and from 7.2 to 24 \'mü\'g L-1 for DGT-SRTXRF and DGT-EDXRF, respectively

Multi-metallic aerogels have recently emerged as a novel and promising class of unsupported electrocatalyst materials due to their high catalytic activity and improved durability for various electrochemical reactions. Aerogels can be prepared by a spontaneous one-step gelation process, where the chemical co-reduction of metal precursors and the prompt formation of the nanochain-consisting hydrogels, as a preliminary stage for the preparation of aerogels take place. However, detailed knowledge about the homogeneity and chemical distribution of these three-dimensional Pd-Pt aerogels at the nano-scale as well as at the macro-scale is still unclear to date. Therefore, we used a combination of spectroscopic and microscopic techniques to obtain a better insight into the structure and elemental distribution of the various Pd-rich Pd-Pt aerogels prepared by the spontaneous one-step gelation process. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-ray spectroscopy (EDX) were employed in this work to uncover the structural architecture and chemical composition of the various Pd-rich Pd-Pt aerogels over a broad length range. The Pd80Pt20, Pd60Pt40 and Pd50Pt50 aerogels showed heterogeneity in the chemical distribution of the Pt and Pd atoms inside the macroscopic nanochain-network. Features of monometallic clusters were not detected by EXAFS or STEM-EDX, indicating alloyed nanoparticles. However, the local chemical composition of the Pd-Pt alloys strongly varied along the nanochains and thus within a single aerogel. To determine the electrochemically active surface area (ECSA) of the Pd-Pt aerogels for applications in electrocatalysis, we used the electrochemical CO stripping method. Due to high porosity and extended network structure, the resulting values of the ECSA for the Pd-Pt aerogels were higher than that for a commercially available unsupported Pt black catalyst. We show that the Pd-Pt aerogels possess a high utilization of catalytically active centers for electrocatalytic applications based on the nanostructured bimetallic framework. Knowledge about the homogeneity and chemical distribution of the bimetallic aerogels can help to further optimize their preparation by the spontaneous one-step gelation process and to tune their electrocatalytic reactivity.

Multi-metallic aerogels have recently emerged as a novel and promising class of unsupported electrocatalyst materials due to their high catalytic activity and improved durability for various electrochemical reactions. Aerogels can be prepared by a spontaneous one-step gelation process, where the chemical co-reduction of metal precursors and the prompt formation of the nanochain-consisting hydrogels, as a preliminary stage for the preparation of aerogels take place. However, detailed knowledge about the homogeneity and chemical distribution of these three-dimensional Pd-Pt aerogels at the nano-scale as well as at the macro-scale is still unclear to date. Therefore, we used a combination of spectroscopic and microscopic techniques to obtain a better insight into the structure and elemental distribution of the various Pd-rich Pd-Pt aerogels prepared by the spontaneous one-step gelation process. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-ray spectroscopy (EDX) were employed in this work to uncover the structural architecture and chemical composition of the various Pd-rich Pd-Pt aerogels over a broad length range. The Pd80Pt20, Pd60Pt40 and Pd50Pt50 aerogels showed heterogeneity in the chemical distribution of the Pt and Pd atoms inside the macroscopic nanochain-network. Features of monometallic clusters were not detected by EXAFS or STEM-EDX, indicating alloyed nanoparticles. However, the local chemical composition of the Pd-Pt alloys strongly varied along the nanochains and thus within a single aerogel. To determine the electrochemically active surface area (ECSA) of the Pd-Pt aerogels for applications in electrocatalysis, we used the electrochemical CO stripping method. Due to high porosity and extended network structure, the resulting values of the ECSA for the Pd-Pt aerogels were higher than that for a commercially available unsupported Pt black catalyst. We show that the Pd-Pt aerogels possess a high utilization of catalytically active centers for electrocatalytic applications based on the nanostructured bimetallic framework. Knowledge about the homogeneity and chemical distribution of the bimetallic aerogels can help to further optimize their preparation by the spontaneous one-step gelation process and to tune their electrocatalytic reactivity.

A fairly new technology used to produce metallic components is powder metallurgy (PM). Among the advantages with this technique are decreased cost of production for complex-shaped parts, new alloys are made possible, reduced end processing, less material loss, and vibrational damping effects. The downside is the number of pores created which can alter the tribological properties of the material. The focus of this report is to investigate how lean PM steel behaves under tribological contacts.  Friction and wear will be investigated using a pin-on-disc setup to mimic the sliding part of a gear tooth mesh. Previous studies show that the amount of wear, and if the wear increases or decreases with increased density is dependent on the degree of porosity and the pore size. This means that the wear might be minimized by optimizing the number of pores in the material and their shape and size. The result of this study shows that the friction coefficient decreases with increasing density. The wear coefficient show signs of the same correlations but further tests are needed. The main wear comes from adhesive wear, with signs of abrasive wear. The amount of abrasive wear seems to increase with an increase in density, supporting previous studies claiming that pores can trap wear debris and decrease the number of abrasive particles in the contact.

Der hauptsächliche Bestandteil dieser Arbeit ist die Entwicklung einer kostengünstigen Methode zur Produktion von auf Silizium basierenden Dünnschicht-Solarzellen durch Sprühbeschichtung. Hier wird untersucht inwiefern sich diese Methode für die Herstellung großflächiger photovoltaische Anlagen eignet. Als Grundsubstanz für entsprechende Lacke werden Mischungen aus Organosilizium und nanokristallines Silizium verwendet. Eine Idee ist das Verwenden von Silizium-Kohlenstoff-Verbindungen als Si-Precursor (Cyclo-, Poly-, Oligo- und Monosilane). In jedem Fall, Organosilizium und Silizium- Nanopartikel, ist eine Umwandlung durch äußere Energiezufuhr nötig, um die Precursor-Substanz in photovoltaisch nutzbares Silizium umzuwandeln. Die Versuchsreihen werden mithilfe photothermischer Umwandlung (FLA-„flash lamp annealing“, einige 1 J/cm² bei Pulslängen von einigen 100 μs) unter N2-Atmosphäre durchgeführt. Zur Bereitstellung eines auf Laborgröße skalierten Produktionsprozesses wurden ein Spraycoater, eine Heizplatte, ein Blitzlampensystem und ein In-Line Ellipsometer in einem Aufbau innerhalb einer Glovebox unter N2-Atmosphäre kombiniert. Die Gewinnung von Proben und deren Charakterisierung fand in enger Zusammenarbeit mit den beiden Arbeitsgruppen der anorganischen Chemie und der Koordinationschemie an der TU-Chemnitz statt. Die eingesetzten Charakterisierungsmethoden sind Raman-Spektroskopie, Infrarotspektroskopie, Rasterelektronenmikroskopie, Transmissionselektronenmikroskopie, Elektronenbeugung, Röntgenbeugung, energiedispersive Röntgenspektroskopie, Rasterkraftmikroskopie und elektrische Charakterisierung wie die Aufnahme von Strom- Spannungs-Kennlinien und Widerstandsmessung per Vierpunktkontaktierung.

<div>In this thesis, the role of location-specific microstructural features in the fatigue performance of the safety-critical aerospace components made of Nickel (Ni)-base superalloys and linear friction welded (LFW) Titanium (Ti) alloys has been studied using crystal plasticity finite element (CPFE) simulations, energy dispersive X-ray diffraction (EDD), backscatter electron (BSE) images and digital image correlation (DIC).</div><div><br></div><div>In order to develop a microstructure-sensitive fatigue life prediction framework, first, it is essential to build trust in the quantitative prediction from CPFE analysis by quantifying uncertainties in the mechanical response from CPFE simulations. Second, it is necessary to construct a unified fatigue life prediction metric, applicable to multiple material systems; and a calibration strategy of the unified fatigue life model parameter accounting for uncertainties originating from CPFE simulations and inherent in the experimental calibration dataset. To achieve the first task, a genetic algorithm framework is used to obtain the statistical distributions of the crystal plasticity (CP) parameters. Subsequently, these distributions are used in a first-order, second-moment method to compute the mean and the standard deviation for the stress along the loading direction (σ_load), plastic strain accumulation (PSA), and stored plastic strain energy density (SPSED). The results suggest that an ~10% variability in σ_load and 20%-25% variability in the PSA and SPSED values may exist due to the uncertainty in the CP parameter estimation. Further, the contribution of a specific CP parameter to the overall uncertainty is path-dependent and varies based on the load step under consideration. To accomplish the second goal, in this thesis, it is postulated that a critical value of the SPSED is associated with fatigue failure in metals and independent of the applied load. Unlike the classical approach of estimating the (homogenized) SPSED as the cumulative area enclosed within the macroscopic stress-strain hysteresis loops, CPFE simulations are used to compute the (local) SPSED at each material point within polycrystalline aggregates of 718Plus, an additively manufactured Ni-base superalloy. A Bayesian inference method is utilized to calibrate the critical SPSED, which is subsequently used to predict fatigue lives at nine different strain ranges, including strain ratios of 0.05 and -1, using nine statistically equivalent microstructures. For each strain range, the predicted lives from all simulated microstructures follow a log-normal distribution; for a given strain ratio, the predicted scatter is seen to be increasing with decreasing strain amplitude and are indicative of the scatter observed in the fatigue experiments. Further, the log-normal mean lives at each strain range are in good agreement with the experimental evidence. Since the critical SPSED captures the experimental data with reasonable accuracy across various loading regimes, it is hypothesized to be a material property and sufficient to predict the fatigue life.</div><div><br></div><div>Inclusions are unavoidable in Ni-base superalloys, which lead to two competing failure modes, namely inclusion- and matrix-driven failures. Each factor related to the inclusion, which may contribute to crack initiation, is isolated and systematically investigated within RR1000, a powder metallurgy produced Ni-base superalloy, using CPFE simulations. Specifically, the role of the inclusion stiffness, loading regime, loading direction, a debonded region in the inclusion-matrix interface, microstructural variability around the inclusion, inclusion size, dissimilar coefficient of thermal expansion (CTE), temperature, residual stress, and distance of the inclusion from the free surface are studied in the emergence of two failure modes. The CPFE analysis indicates that the emergence of a failure mode is an outcome of the complex interaction between the aforementioned factors. However, the possibility of a higher probability of failure due to inclusions is observed with increasing temperature, if the CTE of the inclusion is higher than the matrix, and vice versa. Any overall correlation between the inclusion size and its propensity for damage is not found, based on inclusion that is of the order of the mean grain size. Further, the CPFE simulations indicate that the surface inclusions are more damaging than the interior inclusions for similar surrounding microstructures. These observations are utilized to instantiate twenty realistic statistically equivalent microstructures of RR1000 – ten containing inclusions and remaining ten without inclusions. Using CPFE simulations with these microstructures at four different temperatures and three strain ranges for each temperature, the critical SPSED is calibrated as a function of temperature for RR1000. The results suggest that critical SPSED decreases almost linearly with increasing temperature and is appropriate to predict the realistic emergence of the competing failure modes as a function of applied strain range and temperature.</div><div><br></div><div>LFW process leads to the development of significant residual stress in the components, and the role of residual stress in the fatigue performance of materials cannot be overstated. Hence, to ensure fatigue performance of the LFW Ti alloys, residual strains in LFW of similar (Ti-6Al-4V welded to Ti-6Al-4V or Ti64-Ti64) and dissimilar (Ti-6Al-4V welded to Ti-5Al-5V-5Mo-3Cr or Ti64-Ti5553) Ti alloys have been characterized using EDD. For each type of LFW, one sample is chosen in the as-welded (AW) condition and another sample is selected after a post-weld heat treatment (HT). Residual strains have been separately studied in the alpha and beta phases of the material, and five components (three axial and two shear) have been reported in each case. In-plane axial components of the residual strains show a smooth and symmetric behavior about the weld center for the Ti64-Ti64 LFW samples in the AW condition, whereas these components in the Ti64-Ti5553 LFW sample show a symmetric trend with jump discontinuities. Such jump discontinuities, observed in both the AW and HT conditions of the Ti64-Ti5553 samples, suggest different strain-free lattice parameters in the weld region and the parent material. In contrast, the results from the Ti64-Ti64 LFW samples in both AW and HT conditions suggest nearly uniform strain-free lattice parameters throughout the weld region. The observed trends in the in-plane axial residual strain components have been rationalized by the corresponding microstructural changes and variations across the weld region via BSE images. </div><div><br></div><div>In the literature, fatigue crack initiation in the LFW Ti-6Al-4V specimens does not usually take place in the seemingly weakest location, i.e., the weld region. From the BSE images, Ti-6Al-4V microstructure, at a distance from the weld-center, which is typically associated with crack initiation in the literature, are identified in both AW and HT samples and found to be identical, specifically, equiaxed alpha grains with beta phases present at the alpha grain boundaries and triple points. Hence, subsequent fatigue performance in LFW Ti-6Al-4V is analyzed considering the equiaxed alpha microstructure.</div><div><br></div><div>The LFW components made of Ti-6Al-4V are often designed for high cycle fatigue performance under high mean stress or high R ratios. In engineering practice, mean stress corrections are employed to assess the fatigue performance of a material or structure; albeit this is problematic for Ti-6Al-4V, which experiences anomalous behavior at high R ratios. To address this problem, high cycle fatigue analyses are performed on two Ti-6Al-4V specimens with equiaxed alpha microstructures at a high R ratio. In one specimen, two micro-textured regions (MTRs) having their c-axes near-parallel and perpendicular to the loading direction are identified. High-resolution DIC is performed in the MTRs to study grain-level strain localization. In the other specimen, DIC is performed on a larger area, and crack initiation is observed in a random-textured region. To accompany the experiments, CPFE simulations are performed to investigate the mechanistic aspects of crack initiation, and the relative activity of different families of slip systems as a function of R ratio. A critical soft-hard-soft grain combination is associated with crack initiation indicating possible dwell effect at high R ratios, which could be attributed to the high-applied mean stress and high creep sensitivity of Ti-6Al-4V at room temperature. Further, simulations indicated more heterogeneous deformation, specifically the activation of multiple families of slip systems with fewer grains being plasticized, at higher R ratios. Such behavior is exacerbated within MTRs, especially the MTR composed of grains with their c-axes near parallel to the loading direction. These features of micro-plasticity make the high R ratio regime more vulnerable to fatigue damage accumulation and justify the anomalous mean stress behavior experienced by Ti-6Al-4V at high R ratios.</div><div><br></div>

Der hauptsächliche Bestandteil dieser Arbeit ist die Entwicklung einer kostengünstigen Methode zur Produktion von auf Silizium basierenden Dünnschicht-Solarzellen durch Sprühbeschichtung. Hier wird untersucht inwiefern sich diese Methode für die Herstellung großflächiger photovoltaische Anlagen eignet. Als Grundsubstanz für entsprechende Lacke werden Mischungen aus Organosilizium und nanokristallines Silizium verwendet. Eine Idee ist das Verwenden von Silizium-Kohlenstoff-Verbindungen als Si-Precursor (Cyclo-, Poly-, Oligo- und Monosilane). In jedem Fall, Organosilizium und Silizium- Nanopartikel, ist eine Umwandlung durch äußere Energiezufuhr nötig, um die Precursor-Substanz in photovoltaisch nutzbares Silizium umzuwandeln. Die Versuchsreihen werden mithilfe photothermischer Umwandlung (FLA-„flash lamp annealing“, einige 1 J/cm² bei Pulslängen von einigen 100 μs) unter N2-Atmosphäre durchgeführt. Zur Bereitstellung eines auf Laborgröße skalierten Produktionsprozesses wurden ein Spraycoater, eine Heizplatte, ein Blitzlampensystem und ein In-Line Ellipsometer in einem Aufbau innerhalb einer Glovebox unter N2-Atmosphäre kombiniert. Die Gewinnung von Proben und deren Charakterisierung fand in enger Zusammenarbeit mit den beiden Arbeitsgruppen der anorganischen Chemie und der Koordinationschemie an der TU-Chemnitz statt. Die eingesetzten Charakterisierungsmethoden sind Raman-Spektroskopie, Infrarotspektroskopie, Rasterelektronenmikroskopie, Transmissionselektronenmikroskopie, Elektronenbeugung, Röntgenbeugung, energiedispersive Röntgenspektroskopie, Rasterkraftmikroskopie und elektrische Charakterisierung wie die Aufnahme von Strom- Spannungs-Kennlinien und Widerstandsmessung per Vierpunktkontaktierung.:I Bibliographische Beschreibung II Abkürzungsverzeichnis III Abbildungsverzeichnis IV Tabellenverzeichnis 1 Einleitung 1 2 Grundlagen 3 2.1 Dioden und Photodioden 3 2.1.1 Schottky-Dioden 3 2.1.1.1 Schottky-Kontakt oder Ohmscher Kontakt 3 2.1.1.2 Schottky-Barriere 3 2.1.1.3 Arbeitsweise der Schottky-Diode 5 2.1.1.4 Ladungstransport durch eine Schottky-Diode 6 2.1.2 Schottky-Photodioden 8 2.2 Solarzellen 9 2.2.1 Aufbau einer Solarzelle 10 2.2.2 Charakterisierung einer Solarzelle 10 2.3 Moderne Photovoltaik 12 2.4 Transparente leitfähige Oxide (TCO) 13 2.5 Ultraschalldüse und Sprühnebel 14 2.6 Blitzlampenbehandlung (FLA) 17 3 Methoden zur Charakterisierung 18 3.1 Fourier-Transformations-Infrarotspektroskopie (FTIRS) 18 3.2 Lichtstreuung an Materie 20 3.2.1 Raman-Spektroskopie 20 3.2.1.1 Klassische Deutung des Raman-Effektes 21 3.2.1.2 Quantenmechanische Deutung des Raman-Effektes 22 3.2.1.3 Räumlich eingeschränkte Phononen 23 3.3 Änderung der Lichtpolarisation an Materie 26 3.3.1 Fresnel-Formeln 26 3.3.2 Jones-Formalismus 27 3.3.3 Spektroskopische Ellipsometrie (SE) 27 3.4 Röntgenbeugung (XRD) 29 3.4.1 Kalibrierung des Einfallswinkels 31 3.4.2 Kristallitgröße 31 3.5 Elektronenmikroskopie (EM) 31 3.5.1 Transmissionselektronmikroskopie (TEM) 32 3.5.2 Rasterelektronenmikroskopie (SEM und EDX) 33 3.6 Rasterkraftmikroskopie (AFM) 34 4 Experimentelles 37 4.1 Prozessaufbauten 37 4.2 Messgeräte 39 4.3 Probenherstellung 40 4.3.1 Lösungen und Dispersionen 41 4.3.2 Sprühlack 41 4.3.3 Substratreinigung 42 4.3.4 Drop- und Spraycoating 42 4.3.4.1 Dropcoating und Rohrofenprozess 43 4.3.4.2 Sprühen und Blitzlampenbehandlung 43 4.4 Infrarotspektroskopie 46 4.4.1 DRIFT-Spektroskopie an Silizium-Nanopartikeln im MIR 47 4.4.2 DRIFT-Spektroskopie an Silizium-Precursoren im MIR 48 4.4.3 Transmissions- und Reflexionsspektroskopie an Si-Schichten im FIR 49 4.5 Lichtstreuung 49 4.5.1 Mie-Streuung an Silizium-Nanopartikeln 49 4.5.2 Raman-Streuung an Silizium-Precursoren und –Schichten 50 4.6 AFM an Silizium-Schichten 51 4.7 Elektronenmikroskopie 51 4.7.1 SEM und EDX an Silizium-Schichten und –Folien 52 4.7.2 TEM an Silizium-Nanopartikeln und –Folien 53 4.8 XRD an Silizium-Folien 54 4.9 Elektrische Messungen an Silizium-Schichten und –Folien 55 5 Ergebnisse und Diskussion 56 5.1 Silizium-Nanopartikel als Pulver 56 5.1.1 Dispersionen von Silizium-Nanopartikeln 56 5.1.2 Oxidationsgrad von Silizium-Nanopartikeln 58 5.1.3 Verteilung von Silizium-Nanopartikeln in getrocknetem Ethanol 61 5.2 Gesprühte Silizium-Nanopartikel 64 5.2.1 Ellipsmetrie als In-Line Prozessmethode im Spraycoating 64 5.2.2 Oberflächenrauheit von Schichten von Silizium-Nanopartikeln 66 5.2.3 Effekt des FLA auf Schichten von Silizium-Nanopartikeln 69 5.2.4 Simulationen zum Phonon-Confinement 74 5.3 Organosilizium als Silizium-Precursoren 80 5.3.1 Vorversuche: Zersetzung von Phenylsilanen im Rohrofen 80 5.3.2 Photothermische Zersetzung von Monosilanen durch FLA 82 5.4 Monosilane als Haftmittel zwischen Silizium-Nanopartikeln 89 5.4.1 Bestandteile des verwendeten Lacks 90 5.4.2 Filme hergestellt von Si-Nanopartikeln gemischt mit Si-Precursor 92 5.4.3 Folien hergestellt von Si-Nanopartikeln gemischt mit Si-Precursor 106 5.5 Realisierung von Diodenstrukturen 120 6 Zusammenfassung 124 Literaturverzeichnis Anhang