<p>The structural and magnetic properties of Fe/Co (001) and Fe/V (001) superlattices have been investigated. The thin film structures were deposited on MgO (001) substrates using a four source ultra-high-vacuum based sputtering equipment.</p><p>Reflection high energy electron diffraction showed that the body-centered cubic phase of Co could be stabilized up to a thickness of about eight atomic monolayers. X-ray diffraction measurements confirmed that the Fe/Co superlattices were single-crystalline with a pure body-centered cubic structure. The crystalline quality and the interface profile were found to be strongly dependent on the growth temperature. Furthermore, the Fe/Co superlattices were also found to exhibit novel magnetic properties. The first order magnetic anisotropy constant for the body-centered cubic Co phase was determined to be negative with a magnitude of 110 kJ/m³. Magnetization and Mössbauer measurements showed that the Fe and Co magnetic moments in the superlattices were enhanced. Spin polarized neutron reflectometry proved that all the magnetic moments were collinear.</p><p>The interlayer exchange coupling and the giant magnetoresistance effect in Fe/V superlattices were also studied. The strength of the coupling was found to be dependent on the thickness of the Fe and the V layers. This was also true for the giant magnetoresistance effect. Mössbauer measurements showed that the V-on-Fe interfaces (V deposited on Fe) were more abrupt and less diffuse than the Fe-on-V interfaces. Finally, the lattice parameters of a series of different Fe/V superlattices were determined by x-ray diffraction. The experimental lattice expansion was found to be in good agreement with a simple theoretical model.</p>

The structural and magnetic properties of Fe/Co (001) and Fe/V (001) superlattices have been investigated. The thin film structures were deposited on MgO (001) substrates using a four source ultra-high-vacuum based sputtering equipment. Reflection high energy electron diffraction showed that the body-centered cubic phase of Co could be stabilized up to a thickness of about eight atomic monolayers. X-ray diffraction measurements confirmed that the Fe/Co superlattices were single-crystalline with a pure body-centered cubic structure. The crystalline quality and the interface profile were found to be strongly dependent on the growth temperature. Furthermore, the Fe/Co superlattices were also found to exhibit novel magnetic properties. The first order magnetic anisotropy constant for the body-centered cubic Co phase was determined to be negative with a magnitude of 110 kJ/m3. Magnetization and Mössbauer measurements showed that the Fe and Co magnetic moments in the superlattices were enhanced. Spin polarized neutron reflectometry proved that all the magnetic moments were collinear. The interlayer exchange coupling and the giant magnetoresistance effect in Fe/V superlattices were also studied. The strength of the coupling was found to be dependent on the thickness of the Fe and the V layers. This was also true for the giant magnetoresistance effect. Mössbauer measurements showed that the V-on-Fe interfaces (V deposited on Fe) were more abrupt and less diffuse than the Fe-on-V interfaces. Finally, the lattice parameters of a series of different Fe/V superlattices were determined by x-ray diffraction. The experimental lattice expansion was found to be in good agreement with a simple theoretical model.

In an attempt to develop a more cost-efficient material for solar   energy applications, nano-particles of nickel oxide composite in a silikatmatris manufactured with solar gelmethod and studied structurally by electron microscopy. Furthermore, the thin film optical properties characterized by Variable. Angel Spectroscopic Ellipsometry. Sol gelfilms suitability as a selective absorber surface is also analyzed by optical modeling. / I ett försök att utveckla mer kostnadseffektiva material för solenergitillämpningar har nanopartiklar av nickeloxid inbäddadats i en silikatmatris tillverkats med sol-gelmetoder och undersökts strukturellt med elektronmikroskopi. Vidare har de tunna filmernas optiska egenskaper karakteriserats med vinkelupplöst spektroskopisk ellipsometri. Sol-gelfilmernas lämplighet som en selektiv absorbatoryta har också analyseras genom optisk modellering.

High Voltage Direct Current (HVDC) bushings are insulated devices designed to facilitate the safe passage of electric current across an earthed barrier. Understanding air conductivity is of utmost importance in the design of HVDC components, which is determined by ion density and ion mobility. Previous research has indicated a correlation between air conductivity, air humidity and phenomena on HVDC surfaces. This thesis aims to investigate and elucidate how adsorbed water may contribute to air conductivity. To accomplish this objective, an experimental study is conducted employing ellipsometry to measure the water layer thickness as a function of relative humidity and applied voltage. The results exhibit a thickness consistent with prior studies in the absence of applied voltage, but reveal an altered thickness when voltage is applied. While definitive conclusions cannot be drawn from this thesis alone, the findings provide some support for the hypothesis from earlier research, suggesting the involvement of surface phenomena in air conductivity. The experimental procedure presented in this thesis can be further expanded and refined to gain a more comprehensive understanding of the surface reactions at play. This could further develop the understanding of the factors influencing air conductivity in HVDC systems and contribute to the advancement of design methodologies in this field.

Detta examensarbete initierades och handledes av Mellifiq, ett företag som arbetar med rening av luft och vatten, där en applikation är rening av köksfrånluft med ozon. Ozon förhindrar att fettpartiklar i frånluften ansamlas på väggarna i kanalen och värmeväxlaren, vilket leder till högre brandsäkerhet och mer effektiv användning av värmeväxlaren. Syftet med detta examensarbete var att öka förståelsen av reaktionen mellan ozon och ytan av fettpartiklarna. Tunna fettsyrafilmer ovanpå ett fast underlag användes som modellsystem för att representera ytan av en fettpartikel. Tre fettsyror undersöktes, en mättad fettsyra, fettsyra A, en enkelomättad fettsyra, fettsyra B, och en fleromättad fettsyra, fettsyra C. TIR Raman-spektroskopi användes för att analysera effekten på fettsyrafilmen vid exponering av torr luft, fuktig luft med en relativ fuktighet på 80 % och fuktig luft med en konstant ozonkoncentration. Effekten av ozon undersöktes även med kontaktvinkelmätningar på fettsyrafilmerna. Resultaten från TIR Raman visade att torr luft och fuktig luft (RH 80 %) inte hade någon effekt på fettsyrafilmen, oberoende av vilken typ av fettsyra som användes. När det gäller effekterna av exponering för ozon kunde inga effekter observeras på filmen av fettsyra A i vare sig TIR Raman eller kontaktvinkelmätningar. Därför kunde ingen reaktion mellan fettsyra A och ozon bekräftas vid den ozonkoncentration som användes och de exponeringstiderna som undersöktes. Däremot oxiderades de omättade fettsyrafilmerna av fettsyra B och C när de exponerades för ozon, vilket bekräftades av den snabba minskningen av C-C-dubbelbindningarna i TIR Raman-spektra. Oxidationen av dubbelbindningar i fettsyra B verkade visa en mer komplex kinetik, med en tvåstegsprocess kopplad till en förändring av antalet molekyler vid ytan. Filmerna bestående av fettsyra C visade sig förlora materia när de exponerades för ozon, vilket tyder på att korta flyktiga ämnen bildades under oxidationsprocessen. Denna effekt observerades inte för fettsyra B, där även om den spektrala formen i CH-sträckningsområdet ändrades, vilket bevisade närvaron av nya arter, förblev den totala mängden material i filmen ungefär konstant. Dessutom gav både fettsyra B och C upphov till nya karbonyl-C=O-sträckningstoppar i spektra efter ozonisering, vilket visar att aldehyder, estrar eller båda bildas under processen. Slutligen bekräftade kontaktvinkelmätningarna med en minskning av statiska vinklar att ytan på filmerna av fettsyra B och C förändrades efter ozonisering. / This master thesis project was initiated and managed by Mellifiq, a company that works with purification of air and water, where one application is purification of kitchen exhaust air with ozone. Ozone prevents fat particles in the exhaust air from accumulating on the walls in the duct and the heat exchanger, reducing fire safety concerns and making the use of the heat exchanger more effective. The aim of this master thesis project was to further understand the reaction between ozone and the surface of the fat particles. Thin fatty acid films on top of a solid support were used as model systems to represent the surface of a fat particle. Three fatty acids were investigated, a saturated fatty acid, fatty acid A, a monounsaturated fatty acid, fatty acid B, and a polyunsaturated fatty acid, fatty acid C. TIR Raman spectroscopy was used to analyze the effect on the fatty acid film as it was exposed to dry air, humid air with a relative humidity of 80 %, and humid air with a fixed ozone concentration. The effect of ozone was also investigated with contact angle measurements on the fatty acid films. The results from TIR Raman showed that dry air and humid air (RH 80 %) had no effect on the fatty acid film, independent of the type of fatty acid used. Regarding the effects of exposure to ozone, no effects could be observed on the fatty acid A field in either the TIR Raman or contact angle measurements. Therefore, no reaction between fatty acid A and ozone could be confirmed at the fixed ozone concentration used and exposure times investigated. In contrast, the unsaturated fatty acid films of fatty acid B and fatty acid C were oxidized when exposed to ozone, as confirmed by the rapid decrease of the C-C double bonds in the TIR Raman spectra. However, the oxidation of double bonds in oleic acid appeared to show more complex kinetics, with a two-step process linked to a change in the number density of molecules at the surface. Interestingly, the films consisting of fatty acid C were shown to lose matter when exposed to ozone, indicating that short volatile species were formed during the oxidation process. This effect was not observed for fatty acid B, where though the spectral shape in the C-H stretching region changed, proving the presence of new species, the overall amount of material in the film remained approximately constant. Moreover, both fatty acid B and C gave rise to new carbonyl C=O stretching peaks in the spectra after ozonation, showing that aldehydes, esters, or both are formed during the process. Finally, the contact angle measurements confirmed with a decrease in static angles that the surface of the fatty acid B and C films changed after ozonation.