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Zinc selenide is a wide bandgap II-VI semiconductor. The minimum bandgap at £F point (zone center) is direct and has a room temperature value of 2.67eV, corresponding to the blue region of the visible spectrum (464nm). Molecular beam epitaxy (MBE) is an ultra high vacuum technique used for the growth of semiconductors. The molecular beam epitaxy system used for the growth of semiconductors . The molecular beam epitaxy system used for growth of the II-VI semiconductor layers is described in detail in Chapter 2. Chapter 3 describes the substrate preparation procedure and growth of ZnSe epitaxial layers. Last, information from characterization technique has been used to analysis the quality of the layers and hence determine referred growth conditions.

<p>This work describes how a fatty acid methyl ester (FAME) derived from a vegetable oil can be introduced as reactive diluent in a solvent-borne thermally cured coil-coating system. The evaluated reactive diluent, rape seed methyl ester (RME), has been evaluated both in a fully formulated clear coat system and via model studies.</p><p>A reactive diluent is a compound that acts as a solvent in the liquid paint, lowering the viscosity, and chemically reacts into the final film during cure. Introduction of a reactive diluent derived from vegetable oil give a more environmental compliant coating since a renewable material is incorporated in the coating and the amount of traditional solvent can be decreased. These positive environmental factors have increased the industrial interest.</p><p>The fully formulated clear coat studies describes how addition of reactive diluent affects rheological properties of the wet paint, film formation, incorporation, and final film properties in a hydroxyl-functional polyester/melamine coil-coating system. The coating were cured under industrial coil-coating cure conditions and analyzed with Raman, carbon-14 dating, extraction, dynamic mechanical analysis, and visually observed. Viscosity measurement of the wet paint show that RME works as a diluent. RME increase the mobility in the system enhancing the film formation process and occurrence of defect-free films. The incorporation of RME could not be confirmed by Raman analysis. However, carbon-14 dating did indicate the presence of RME that could not be extracted from the films. The appearance and mechanical properties of the films were also significantly affected by addition of RME. Dynamic mechanical analysis of the free standing films showed that the final film properties were affected by oven temperature, choice of co-solvent, and flash-off period.</p><p>Model studies were performed to further clarify how RME chemically can react through transesterification with the hydroxyl-groups of the polyester. RME and its two main components methyl oleate and methyl linoleate were reacted with primary alcohols with and without tertiary hydrogen both under low temperature (110, 130, 150, 170°C) and industrial cure conditions. The transesterification reaction was monitored with 1H-NMR and real time IR. Evaporation and side reactions, e.g. oxidation, are competing factors with the transesterification reaction. The fatty acid structure affects the conversion as a higher amount of unsaturations triggers higher degree of oxidation. The study also showed that reaction time and temperature affects the transesterification conversion, degree of side reactions, and catalyst choice.</p>

This work describes how a fatty acid methyl ester (FAME) derived from a vegetable oil can be introduced as reactive diluent in a solvent-borne thermally cured coil-coating system. The evaluated reactive diluent, rape seed methyl ester (RME), has been evaluated both in a fully formulated clear coat system and via model studies. A reactive diluent is a compound that acts as a solvent in the liquid paint, lowering the viscosity, and chemically reacts into the final film during cure. Introduction of a reactive diluent derived from vegetable oil give a more environmental compliant coating since a renewable material is incorporated in the coating and the amount of traditional solvent can be decreased. These positive environmental factors have increased the industrial interest. The fully formulated clear coat studies describes how addition of reactive diluent affects rheological properties of the wet paint, film formation, incorporation, and final film properties in a hydroxyl-functional polyester/melamine coil-coating system. The coating were cured under industrial coil-coating cure conditions and analyzed with Raman, carbon-14 dating, extraction, dynamic mechanical analysis, and visually observed. Viscosity measurement of the wet paint show that RME works as a diluent. RME increase the mobility in the system enhancing the film formation process and occurrence of defect-free films. The incorporation of RME could not be confirmed by Raman analysis. However, carbon-14 dating did indicate the presence of RME that could not be extracted from the films. The appearance and mechanical properties of the films were also significantly affected by addition of RME. Dynamic mechanical analysis of the free standing films showed that the final film properties were affected by oven temperature, choice of co-solvent, and flash-off period. Model studies were performed to further clarify how RME chemically can react through transesterification with the hydroxyl-groups of the polyester. RME and its two main components methyl oleate and methyl linoleate were reacted with primary alcohols with and without tertiary hydrogen both under low temperature (110, 130, 150, 170°C) and industrial cure conditions. The transesterification reaction was monitored with 1H-NMR and real time IR. Evaporation and side reactions, e.g. oxidation, are competing factors with the transesterification reaction. The fatty acid structure affects the conversion as a higher amount of unsaturations triggers higher degree of oxidation. The study also showed that reaction time and temperature affects the transesterification conversion, degree of side reactions, and catalyst choice. / QC 20101117

Solvent-borne thermally cured coil-coating resins contain large amounts of volatile organic solvents in order to obtain suitable flow for film application. This work describes how the expensive and environmental hazardous volatile organic solvent content of a solvent-borne thermally cured polyester/melamine coil-coating system can be reduced by introduction of fatty acid methyl esters (FAMEs) as reactive diluents and modification of the polyester binder resin. The evaluated reactive diluents, two rape seed methyl esters (RMEs), two linseed oil methyl esters (LMEs), and a tall oil methyl ester (TOME) have been evaluated both in a fully formulated clear-coat system and via model studies. Viscosity measurements of wet paint mixtures showed that formulations with hyperbranched polyester binder hold lower viscosity than conventional polyester binder resins and that FAME works as a diluent. Fully formulated clear-coats were cured under simulated industrial coil-coating cure conditions and in a convection oven at lower temperatures respectively. FAME increases the mobility of the system enhancing the film formation process. Free-standing clear-coat films were analyzed with Raman, carbon-14 dating, extraction, dynamic mechanical analysis, and visual observation. Incorporation of FAME could not be confirmed by Raman analysis. However, carbon-14 dating indicated the presence of FAME that could not be extracted from the films. The mechanical properties of the films were also affected by the addition of FAMEs, oven temperature, choice of co-solvent, and flash-off period. Conventional film characterization tests on substrate supported coatings indicated that binder resin structure and cure conditions affect the final film properties. Model studies were performed to clarify how FAME can chemically react through transesterification with the hydroxyl-groups of the polyester. The transesterification reaction between different FAMEs and primary alcohols with and without tertiary hydrogen was monitored with 1H-NMR and real time IR. Evaporation and side reactions, e.g. alkene reactions, are competing factors to the transesterification reaction. The study showed that fatty acid structure, reaction time, and temperature affect the transesterification conversion, degree of side reactions, and choice of catalyst. A pigmented fully formulated polyester/melamine formulation with a reactive diluent was cured at full scale in an industrial coil-coating production facility. Evaluation of the final film properties showed that the coating fulfills the specification of conventional polyester/melamine coil-coating systems. / QC 20100817

Deposition of thin films is one of the most widespread applications used for the changes of surface properties of various materials. This diploma thesis is focused on diagnosing of thin film generated by a PECVD technique. The capacitively coupled RF discharge at low pressure was used for the thin films deposition using tetrafluoromethane (CF4) with addition of hydrogen (H2) as a precursor. The aim of the work was the search of optimal conditions for a hydrophobic thin layer preparation on the surface of polymer NOA. The depositions were performed in continuous and pulsed mode with different duty cycle. The discharge was monitored using optical emission spectroscopy and in situ mass spectrometry. Thin films structure and properties were characterized using water contact angle measurements, X-ray photoelectron spectroscopy, infrared spectroscopy and optical ellipsometry. The influence of varying power, gas mixture composition and discharge mode were investigated. Water contact angle was the highest for a deposition in a continuous mode. Decomposition processes inside the reactor were observed by using mass spectrometry and optical emission spektrokopie. X-ray photoelectron spectroscopy provided information about the chemical bonds represented on the surface of sample. These were mainly C – C/C – H, C – O, O = C - O groups for sample without layer. Other chemical bonds were observed after the deposition. These were mainly C – CF, CF2 and CF3 groups. The film thickness of about 8,2 nanometers was measured by optical ellipsometry. The obtained results may be used as a fundament for further more advanced study of plasma chemically prepared thin fluorocarbon films and their properties.

In dieser Arbeit wurde eine systematische Untersuchung der Abscheidung von TiO2 mittels reaktiver Ionenstrahlzerstäubung von einem metallischen Ti-Target sowie von einem keramischen TiO2-Target durchgeführt. Der Einfluss der Prozessparameter, d.h. der Ionensorte, der Ionenenergie, des Einfalls- und Emissionswinkels sowie des Targetmaterials, auf die Eigenschaften der Sekundärteilchen und der TiO2-Schichten wurde untersucht. Der Ionenstrahl wurde mit einer Faradaysonde, einem Gegenfeldanalysator und einem energieselektiven Massenspektrometer charakterisiert. Das Massenspektrometer wurde auch zur Untersuchung der Massen- und Energieverteilung der Sekundärionen eingesetzt. Mit SDTrimSP simulierte Energieverteilungen der Sekundärteilchen zeigten eine gute Übereinstimmung mit den gemessenen Energieverteilungen der Sekundärionen. Die TiO2-Schichten wurden mittels Ellipsometrie, Röntgendiffraktometrie, -reflektometrie, Rutherford-Rückstreu-Spektrometrie und Rasterkraftmikroskopie untersucht. Eine Verringerung des Streuwinkel führte zu einer Erhöhung der Sekundärteilchenenergien, resultierend daraus wurde eine verstärkte Implantation von Primärteilchen, eine Oberflächenglättung sowie eine systematischen Änderung der Massendichte und folglich der optischen Eigenschaften beobachtet. Die Ionenenergie und das Targetmaterial spielten dabei eine untergeordnete Rolle. / A systematic investigation of the reactive ion beam sputter deposition of TiO2 from a metallic Ti and a ceramic TiO2 target was performed. The influence of the process parameters, i.e. the ion species, ion energy, ion incidence angle, emission angle, and the target material, on the properties of the secondary particles and the TiO2 films was investigated. The ion beam was characterized with a Faraday probe, a retarding potential analyzer, and an energy-selective mass spectrometer. The mass spectrometer was also used to determine the mass and energy distribution of the secondary ions. The experimentally obtained energy distributions were compared to the energy distributions of the secondary particles that were simulated with SDTrimSP. A good agreement was found. The TiO2 films were investigated by spectroscopic ellipsometry, X-ray diffraction, X-ray reflectivity, Rutherford backscattering spectrometry, and atomic force microscopy. Reducing the scattering angle lead to an increase of the secondary particle energies, resulting in an enhanced implantation of primary particles, surface smoothing, and a systematic change of the mass density and consequently of the optical properties. The ion energy and the target material had a minor influence.

The main objective of this thesis is the study of the optical and optoelectronic properties of organic semiconducting materials. At the beginning of this thesis is shown the growing interest in these materials and their practical application. The theoretical part presents the current state of knowledge of studied problematic related to optical phenomena and the transport of charge carriers in organic semiconductors, photochormic phenomena of reversible molecular switch and charge transfer in DNA biopolymeric matrix. Experimental section, which consists of selected author’s publications, includes study of the charge transport, photochromic reversible switching and the role of dopant in pi-conjugated organic polymer system. Conductive and semiconductive characteristics of the DNA biopolymer have been aslo studied. Conductive and photoconductive techniques together with measurement of the optical characteristics have been used for organic semiconductors characterization.

There is growing demand for a more efficient use of polymers that originate from renewable feedstocks due to the depleting supply of fossil fuels, based on economic and environmental reasons. As a result, lignin has attracted renewed interest as a resource for various bioproducts. Lignin is a natural biopolymer with a high carbon content and is composed of aromatic moieties, with a high level of polar functionalities. This makes it a unique precursor for certain high-value applications, such as in biofuels, bioplastics, composite materials, carbon fibers and activated carbons and as a source of phenolic monomers and fine chemicals. Industrial lignins are formed as byproducts of pulping processes (such as kraft, sulfite or alkaline pulping) or result from the biorefining process, where carbohydrates are used for sugar production. Lignin’s intrinsic structure is significantly modified during the processing of lignocellulose, resulting in the formation of more diverse, condensed and less reactive raw materials. Since molecular mass and polydispersity are the most important parameters affecting the chemical reactivity and thermal properties of lignin, additional process steps to improve the quality of crude technical lignins, including kraft lignin, are needed. Solvent extraction is a potentially useful technique for further improving the polydispersity of technical lignins. This work summarizes the impact of solvent fractionation on the chemical structure, antioxidant activity, heating value, and thermal and sorption properties of industrial hardwood and softwood kraft lignins. The purpose was to understand the correlation between certain structural features in the lignin fractions and their properties to select the appropriate solvent combinations for specific applications of lignin raw materials. Four common industrial solvents, namely, ethyl acetate, ethanol, methanol and acetone, in various combinations were used to separate both spruce and eucalyptus kraft lignins into fractions with lower polydispersities. Gel-permeation chromatography analysis was used to evaluate the efficiency of the chosen solvent combination for lignin fractionation. The composition and structure of the lignin material were characterized by elemental analysis, analytical pyrolysis (Py-GC/MS/FID) and 31P NMR spectroscopy. The thermal properties of the lignin samples were studied by thermogravimetric analysis. Proximate analysis data (ash, volatile components, organic matter and fixed carbon) were obtained through the direct measurement of weight changes during the analysis, while the high heating values (in MJ/kg) were calculated according to equations suggested in the literature. The sorption properties of fractionated kraft lignins were studied with respect to methylene blue dye. Additionally, lignin fractions with different molecular weights (and therefore various chemical structures) that were isolated from both softwood and hardwood kraft lignins were incorporated into a tunicate cellulose nanofiber (CNF)-starch mixture to prepare 100% bio-based composite films. The aim was to investigate the correlation between lignin diversity and film performance. The transmittance, density and thermal properties of the films were investigated, as were their mechanical properties, including the tensile stress and Young’s modulus. This part of the study addressed the importance of lignin diversity on composite film performance, which could be helpful for tailoring lignin applications in bio-based composite materials based on the material’s specific requirements.