In this study, the oxygen permeation and stability properties of disk shaped and asymmetric membranes, both of the composition La0.2Sr0.8Fe0.8Al0.2O3-δ were investigated. Strontium doped Lanthanum ferrite is an oxygen deficient mixed ionic electronic conducting perovskite related material. Co-doping with Aluminum enhances the stability of the system. Received precursor was ball milled and sieved to 250 µm. Phase purity was determined by means of X-ray diffraction. Further on particle size distribution and surface area data were collected by dynamic light scattering and nitrogen absorption (BET).Ceramic disks were fabricated by dry uniaxial dye pressing and sintered at different temperatures. Densities of green bodies were measured by geometric means to be approximately 40% of theor. and final densities were measured using Archimedes method. to be approximately 96% of theor. at a sintering temperature of 1230 °C for 2 h in air.Asymmetric membranes consist of a porous support and a dense functional layer. For preparation of porous supports the powder precursor was mixed with 30 wt-% carbon black and 3 wt-% ethyl cellulose. Supports were calcined at 950 °C and then dip coated with a stabilized suspension of La0.2Sr0.8Fe0.8Al0.2O3-δ in ethanol. After dip coating, membranes were pre sintered at 1100 °C, dip coated again and finally sintered at different temperatures. Visual densities were investigated by scanning electron microscopy. Final sintering parameters were 1230 °C for 2 h respectively. Furthermore, investigations on surface modification were carried out by wet chemical etching using 6M hydrochloric acid, resulting in a partly or complete dissolved functional layer.Oxygen flux of membranes was finally measured in a flux furnace with coupled gas chromatograph.Disk shaped membranes reached oxygen flux values up to 1.77 ml*min-1*cm-2 and asymmetric membranes up to 15.33 ml*min-1*cm-2. After flux measurements were completed, the membranes were checked for degradation by means of XRD and SEM/EDS. Both, disk shaped and asymmetric membranes were overall single phase but showed some morphological degradation.

The demand for high-performance Radio Frequency (RF) passive devices has been steadily increasing due to the growing complexity and sophistication of wireless communication systems. The Quality factor (Q-factor) is a key parameter for describing the signal losses and the energy efficiency of resonators. Previous studies have been done on the spin coating technique of intermediate coating, which presented some limitations in terms of 3D resonators. In this master thesis, we investigate the development of a intermediate layer using dip coating to enhance the Q-factor, i.e., the performance of RF passive devices. The dip coating method is applied to add a nano ceramic coating to the 3D structure as the intermediate layer between the resonator ceramic substrate and the conductive silver coating. After the fabrication process, the samples are observed under Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) and tested with Vector Network Analysis (VNA). Analysis and calculations are mainly conducted with the software Matlab and Gwyddion. The proposed technique improves the smoothness of the samples by 78.95%, and the Q-factor is tested to have a 20.87% enhancement using VNA. The results demonstrate that the intermediate layer with the dip coating technique significantly improves the performance of RF passive devices by reducing the roughness of the resonator surface. These findings open up new opportunities for the design and development of high-performance RF passive devices in various applications, including wireless communication systems, radar systems, and satellite communication. Further studies can be carried out to reduce defects during fabrication and to stabilize the performance of the silver coating. / Efterfrågan på högpresterande passiva RF-enheter har stadigt ökat på grund av den växande komplexiteten och sofistikeringen hos trådlösa kommunikationssystem. Q-faktorn är en viktig parameter för att beskriva signalförluster och energieffektivitet hos resonatorer. Tidigare studier har gjorts på spin coating-tekniken för intermediära beläggningar, vilket presenterade vissa begränsningar för 3D-resonatorer. I denna masteruppsats undersöker vi utvecklingen av ett intermediärt lager med hjälp av doppbeläggning för att förbättra Q-faktorn, det vill säga prestandan hos passiva RF-enheter. Doppbeläggningstekniken tillämpas för att lägga till en nanokeramisk beläggning på 3D-strukturen som intermediärt lager mellan resonatorns keramiska substrat och den ledande silverbeläggningen. Efter tillverkningsprocessen observeras proverna med SEM och AFM och testas med VNA. Analys och beräkningar utförs främst med programvaran Matlab och Gwyddion. Den föreslagna tekniken förbättrar provernas släthet med 78.95%, och Q-faktorn testas och visar en förbättring med 20.87% med hjälp av VNA. Resultaten visar att det intermediära lagret med doppbeläggningstekniken signifikant förbättrar prestandan hos passiva RF-enheter genom att minska ojämnheten på resonatorns yta. Dessa resultat öppnar upp nya möjligheter för design och utveckling av högpresterande passiva RF-enheter inom olika tillämpningsområden, inklusive trådlösa kommunikationssystem, radarssystem och satellitkommunikation. Ytterligare studier kan genomföras för att minska defekter under tillverkningen och stabilisera prestandan hos silverbeläggningen.

This work is about representation and existing. I’m fat and transmasculine. I’m looking for a reflection in my surroundings, culture, in media and art. I can’t find it, so I have to create it myself. Through materialising bodies in clay that describe what fat transmasculine people can look like I aim to give myself and people who are similar to me something we’re lacking. I claim my existence.

Gas turbine engine efficiency needs to be raised in order to decrease fuel consumption, greenhouse gas emissions, and expenses. Efficiency may be improved in two ways: by reducing engine weight and raising intake temperatures. At intake temperature, conventional nickel-based alloys are already on the verge of failure, meaning there is a need and demand of materials which can withstand higher temperatures. Silicon Carbide Ceramic Matrix Composites (SiC CMCs) are being investigated as a potential replacement for superalloys due to their superior physical properties, such as their low weight and high melting point (approximately one-third of superalloys' weight). However, using SiC CMCs has a serious disadvantage. The mass recession of the SiC is caused by the volatilization of silicon hydroxide, which is caused by oxidation and reactivity with water vapor under the working conditions of gas turbine engines. Therefore, a shielding layer is used to prevent oxidation of the SiC CMCs. This protective coating (EBC) goes by the name of Environmental Barrier Coating. Thermal spray techniques such as atmospheric plasma spray and suspension plasma spray, which employ powder as the feedstock, are used to deposit EBC on SiC CMCs. For EBC to perform well, the coating must be crystalline, reasonably thick to sustain harsh environment, and devoid of cracks. EBC was deposited in order to look at how the spray parameters affected the microstructure. SEM pictures were used to quantify the coating's porosity and the severity of the cracks. To investigate the production of thermally grown oxide (TGO) in the coating and substrate and check how EBCs perform under thermal cyclic fatigue loading, a thermal cyclic fatigue test was conducted. The XRD analysis is performed to ascertain the proportion of crystalline and amorphous phases in the coating, which unfortunately is still in the process to be completed. In the as-sprayed coating samples we can see that when there are more amount and larger pores, we see less number of cracks and vice versa. The effect of spray parameters can be seen on the coatings. Comparing to SPS trial 1, the SPS trial 2 coatings are denser with less number of cracks and has good adhesion. Still the SPS trial 2 coating did not achieve better microstructure in terms of density, and cracks compared to the APS coatings but further looking into the parameters, more desirable coatings can be achieved. After TCF testing, a layer of TGO was seen at the bond coat/topcoat interface, and there was no failure of the coating seen.