Ceramics with mixed ionic and electronic conductivity are being investigated for oxygen separation from air, intended for the production of syngas. Asymmetric membranes, consisting of a dense membrane co-sintered with a porous support are expected to achieve a high flux of oxygen and at the same time adequate strength. As the porous substrate is mainly intended for strength contribution, it is crucial that the flux of oxygen through the dense membrane is not limited by the flow of air through the porous substrate. An oxygen flux of 10 ml min-1 cm-2 should be achieved at operating temperatures (800-1000 °C) for the substrate to be commercially attractive. A biaxial strength of 34MPa has been obtained by similar porous substrates.Four different strategies for achieving high permeating substrates made by solid state La0.2Sr0.8Fe0.8Ta0.2O3-x have been evaluated. Pressed porous substrates were produced both with and without the use of pore formers. The most promising compositions with respect to porosity and permeability were tape casted and characterized with respect to porosity, permeability and strength.

Coin cells with lithium and graphite electrodes were assembled using different combinations of graphite material and electrolyte. Specifically, three commercially available graphite materials and five electrolyte compositions were studied. The cells were discharge-charge cycled with varying parameters in order to determine the performance of the graphite materials and electrolytes. Particularly, a temperature chamber was employed to cycle some cells at temperatures between 0 and 40°C to find the significance of the electrolyte composition and graphite material on the cell performance at these temperatures. The cycled cells were disassembled and samples from the graphite electrode soaked with electrolyte were prepared for thermal analysis, specifically differential scanning calorimetry (DSC). The thermal stability of the graphite electrodes and the influence from the graphite and electrolyte properties and the cycling parameters were analysed. In order to facilitate the interpretation of the results from discharge-charge cycling at different temperatures, DSC analysis from -80 to +50°C was performed on the pure electrolytes.Confirming previous studies, it was found that both the thermal stability and cycling performance were highly influenced by the properties of a solid electrolyte interphase (SEI), situated between the graphite surface and the electrolyte and formed during cycling. The three graphites were good substrates for stable SEI formation, exhibited by high thermal stability after being cycled at room temperature. After cycling with a temperature program, subjecting the cells to temperatures between 0 and 40°C, the thermal stability was generally reduced. This was attributed to increased SEI formation. The properties of both the electrolyte and graphite influenced the SEI and consequent thermal stability, though in different ways.The cell capacity was considerably reduced upon cycling at lower temperatures, such as 10 and 0°C. The results indicate that the electrolyte properties, particularly the viscosity and resulting conductivity, played the most important role in determining the cell performance. Low viscosity electrolyte components should be utilised, maintaining the electrolyte conductivity even at reduced temperatures. The graphite properties did not influence the cell performance at the temperatures studied. Advice is given on which electrolyte components should be avoided to build Li-ion cells performing acceptably at temperatures from 0 to 40°C.

High purity silicon material in solar cell fabrication constitutes 40% of the total cost for conventional solar cell production. One approach to reduce costs would be to use less of this expensive silicon by making thin film solar cells and use a cheaper substrate as mechanical carrier.In this work the main objective has been to manufacture silicon substrates from powder by hot-pressing. The effect of the sintering parameters has been characterized. A secondary objective was to look at the possibility to achieve larger grains by recrystallization.Samples processed by hot-pressing silicon powder of metallurgical grade with varying temperatures (1200-1375 °C), pressures (30-50 MPa) and sintering time (30-60 min) has been carried out. Halogen lamps were used for heat treatment for specific samples after hot-pressing. Microstructure and porosity were characterized using optical and electronic microscopy. EBSD was used to determine the grain size and grain orientation. The density was determined by Archimedes’ method. Resistivity was measured by a conductive probe.Densities higher than 90 % were obtained at high temperatures and pressures. The time conducted at maximum temperature during hot-pressing was not of vital importance with respect to density.The mean particle size of the powder was determined to ~20 μm, while hot-pressed samples had an average grain size of ~30 μm. The samples showed low resistivity due to high impurities of the silicon powder. High surface porosity was found for the less dense samples. Recrystallization was successfully achieved for the sample hot-pressed at 1350 °C, 30 MPa and 30 min, resulting in elimination of pores and significant grain growth from 31,83 to 56,96 μm.Characterizations of the hot-pressed samples are limited to the methods and techniques described above.

Hydrogen transport membranes have gained interest from industry as an alternative to pressure swing adsorption or cryogenic distillation, and are aimed to reduce cost, equipment size, energy consumption and waste generation. Doped strontium cerate stabilized with zirconium exhibit high proton conductivity and chemical stability and is therefore considered to be a promising material for hydrogen transport membranes.The purpose of the work was to investigate if phase pure strontium cerates, stabilized with zirconium and doped with thulium, ytterbium or yttrium, could be synthesized by the Pechini method, and if the membranes exhibited sufficient density. Determination of optimal calcination and sintering parameters was also important parts in the study.SrCe0.75Zr0.20M0.05O3-d, (M=Tm,Y,Yb) were synthesized via the Pechini method, followed by calcination, pressing of green bodies and sintering of dense membranes. Phase purity of powders and sintered membranes was examined by X-ray diffraction. Surface investigation and microstructure was investigated in a scanning electron microscope. Sintering behavior and thermal expansion coefficients was determined by dilatometry. Phase pure and dense orthorhombic perovskite structured SrCe0.75Zr0.20M0.05O3-d;, (M=Tm,Y,Yb) membranes, were obtained by powder calcination at 1000 C, followed by milling and conventional sintering at 1500-1600 C. SrCe0.75Zr0.20Tm0.05O3-d demonstrated the highest density of 98,6%, when sintered at 1500 C. Sintered membranes had a average grain size in the range from 3,2 – 4,9 um. Ball milling is concluded to be of vital importance to obtain sufficient density in the membranes.The membrane characterization is limited to the methods and techniques described above. Hydrogen flux across the membrane, total conductivity, stability in reducing atmosphere and thorough investigation of thermal properties are recommended for further work.

The main object was to investigate the effect of donors, thermal donors and defects on the lifetime on n-type Czochralsky (Cz) silicon. Cz is a technique for making monocrystals by dipping a monocrystalline seed into the melt, and pulling the ingot up as the melt solidifies. Samples were prepared by sawing, grinding and polishing. Copper decoration and preferential etching was done to reveal the defects. Resistivity measurements were performed to investigate the donor distribution. The lifetime and oxygen concentration was measured.The lifetime may be influenced by donors and traps. Traps may be metallic or non-metallic. Dopants and metal contaminants are usually Scheil distributed, which typically involves a relatively stable distribution in most part of the ingot, and a rapid increase in concentration close to the bottom. Metal contaminants may be introduced from the feedstock, and dopants (either n or p dopants) are added to the melt.Oxygen is dissolved from the crucible. The oxygen concentration typically decreases with increasing length, and is controlled by the rotation speed. This was confirmed by the interstitial oxygen measurements. The oxygen concentration showed no change after heat treatment, but the presence of oxygen in itself may contribute to produce lifetime reducing agents, such as precipitates and thermal donors. Thermal donors were found in the first 18cm of the ingot. Both the resistivity and lifetime measurements was used to calculate estimated lifetimes and donor concentrations, respectively. This estimated values were compared with the measured ones, revealing that the lifetime in the ingot was SRH dominated. Thermal donors were found to have less influence on the lifetime than the trapping. Oxygen precipitations may explain the low lifetime found in the center of the ingot up to about 30cm from the crown. Such precipitations are often gathered in defect bands in the sample. CDI of a Cu decorated sample revealed a pattern of different defect densities, which also showed up at the surface of the sample after preferential etching. An H- or L- band was believed to be situated here, which both consist of small oxygen precipitates. Defects arize as a funktion of the pulling parameters, and a low growth rate was connected to the low lifetime here. Indications of the presence of non-metallic traps were found throughout the ingot. However, oxygen precipitates could not explain the non-metallic traps that was found on the outside of the ingot, and the cause of these is therefore unknown. It is however likely that these traps may be connected to the pullrate/temperature gradient-ratio. Most likely metallic traps were also present. It is uncertain whether the non-metallic or metallic traps were the most important to the lifetime of this ingot, as the relative distribution of the two cannot be decided with certainty from the results in this thesis.Contrasts in CDI and steep curves using PCD measurements vs length plots were believed to be due to the lifetime degrading agent that changes the fastest. Metallic traps and the phosphorous dopant are known to be Scheil distributed, hence they appear transparent for the lifetime measurements in areas where the distribution is stable. Thermal donors and non-metallic traps are thus more likely to create contrast in the top parts of an ingot. However, it is not necessarily the phenomenon that causes the contrast that is the major lifetime degradation contributor.

I denne masteroppgaven ble det syntetisert iridiumbaserte katalysatorer på en bærerstruktur for oksygenutviklingsreaksjonen i en PEM vannelektrolysør, ved hjelp av en polyolmetode. Katalysatorpulverne ble karakterisert ved hjelp av både elektrokjemiske (syklisk voltammetri, polarisasjon og impedans), og fysiske metoder (SEM, TEM, BET, EDS, and XPS). I tillegg ble det konstruert en apparatur for måling av elektronisk ledningsevne, og denne ble benyttet for å sammenlikne den elektroniske ledningsevnen til to ulike bærermaterialer, antimondopet tinnoksid (ATO) og wolframoksid (WO3).Målet for arbeidet var å studere effekten som bruk av bærermaterialer og ulike synteseforhold har på de elektrokatalytiske egenskapene til iridiumbaserte katalysatorer på bærere.Resultatene fra dette arbeidet viser at av de to valgte bærermaterialene så har ATO de mest egnede egenskapene for bruk som bærermateriale i et elektrodesystem, i det at den elektroniske ledningsevnen var mye høyere og det spesifikke overflatearealet var større enn hos WO3. Karakterisering av de syntetiserte katalysatorene på ATO viser elektrokatalytiske egenskaper som er på samme nivå som, eller bedre enn, andre katalysatorer laget til samme formål. Forandringer gjort på synteseforholdene (pH og konsentrasjon av materialer) virket ikke å ha noen effekt av betydning på verken morfologi, partikkelstørrelse eller den katalytiske aktiviteten til katalysatorene.

By applying a texture to the front surface of solar cells, less light may be reflected and the incoming light may be given a longer path length inside the solar cell causing a better light absorbance for the solar cell. The textured layer is today made by etching with an acidic etch with a large part hydrogen fluoride. In the future a more environmental approach for creating textured solar cells may be favoured. There are many ways of creating textured surfaces, one of them are by imprinting the surface by a template, and remove the template when the process is completed.In this project the diatom species Coscinodiscus walesii and an undefined Coscinodiscus species were cleaned and processed for investigation. The work done can be divided into four tasks. The first was characterisation and investigation of the pore structure. The second were manufacturing and characterisation of gold for use as templates. The third were deposition and characterisation of thin films of silicon and silicon nitride on diatom frustules. The last part were to make structures are very similar to solar cells with diatom frustules incorporated into them.The diatom frustules were characterised by SEM and the pore structure were cut through with FIB to characterise the structure. There were structural differences between the two species. The Coscinodiscus walesii was grown in a cultivation chamber, and lacked the circular inner pore structure which the undefined Coscinodiscus species had. This was the only real difference between the two species.On the cultivated species were deposited a gold film, which a small rectangle were lifted off by a tungsten needle in FIB. The small rectangle were characterised with the SEM-column in a dual beam FIB. Pore structures down to 40 nm were replicated by the gold film lifted off the frustule. By depositing a relatively thick film of gold on a glass substrate covered with diatom frustules and dissolving the glass substrate and diatom frustules with hydrogen fluoride, a template were made with a replication of the diatom frustule pore structure.Silicon and silicon nitride were deposited on diatom frustules and characterised with FIB to investigate how those materials followed the frustule topography. A good conformity of films made of those materials was confirmed, and 4 different samples which were similar to solar cells were manufactured and characterised by light microscopy, SEM and FIB. Two samples were made to be similar to crystalline silicon solar cells. One had dried frustules on top of a silicon surface and the entire surface of the sample were coated with silicon nitride, a blue colour were observed in the entire surface and the silicon nitride had also been deposited on the diatom frustules. For the other sample similar to crystalline silicon solar cells another layer were deposited between the frustule and the silicon substrate. The double silicon layer made the sample surface yellow, the diatom frustules did not get darker due to a layer above and a layer beneath them. Only in some places where the frustules had loosened from the sample the sample were blue as the silicon nitride layer were the same as a single layer of silicon nitride. For the last two samples, thin film solar cell structures based on amorphous silicon deposited with PECVD were made. A sample there a aluminum coating were deposited on a glass substrate and diatom frustules were dried on top of the aluminum coating, afterwards a 5 µm thick film of amorphous silicon were deposited. SEM images showed that the film were distributed even across a diatom frustule and a light microscopy investigation showed that light were spread when it hit the diatom frustules, hence creating a longer mean path through the solar cell.

Stability and compatibility of the proton conducting electrolyte material La6WO12 with the potential cathode materials LaCoO3 and La2NiO4 were investigated by means of solid-solid diffusion couples. Reactivity studies were carried out at 1450 °C for various times. Reaction products were analysed by SEM and EDS. The study suggests a high reactivity between the electrolyte and the electrodes, which is detrimental for the fuel cell system.In the case of LaCoO3 as a cathode material a secondary phase of LaCo1-xWxO3 were formed at the interface and as precipitates in La6WO12. Theoretical models for both diffusion or interface controlled reactions failed to fit the experimental data. This failure is probably related to the reaction going towards equilibrium after a certain time, or poor connectivity between the materials. The solid- state reaction between La6WO12 and La2NiO4 showed formation of a composite layer of La2O3 and La6WO12 at the interface. The reaction kinetics of this product layer was diffusion controlled. In addition to the interface reaction, precipitates of La2O3 and La6WO12 were formed in the La2NiO4 phase.

I arbeidet med denne avhandlingen har det blitt utført et omfattende arbeid på ulike aspekter ved utviklingen av et monocoque chassis designet for å konkurrere i Formula Student. Analyse, dimensjonering og produksjon er hovedtema i denne oppgaven. Fokuset har ligget i å beskrive den tilnærmingen som brukes i designfasen, analyse og testing av lokaliserte laster på sandwichpaneler, samt utvikle en produksjonsprosess for chassiset. Alt av dimensjonering, analyse og testing er utført på sandwich paneler representativt for et monocoque chassis. Hovedfokuset har vært et racerbilchassis for Revolve NTNU, med tilhørende laster. Monocoque-chassiset er en selvbærende konstruksjon hvor hjuloppheng, girkasse, veltebøyler og andre innfestninger går direkte i chassiset som tar opp alle kreftene.Mye av arbeidet har blitt gjort i analyse og eksperimentell testing av lokaliserte laster på sandwich paneler med såkalte “inserts”, da dette er den mest brukte metoden for å overføre laster inn på et skjærsvakt sandwichpanel.Eksperimeter og testing har vært en stor del av denne avhandlingen. Den meste av teorien som er beskrevet og brukt i denne oppgaven er også basert på empiriske resultater. Mye av arbeidet har bestått av den faktiske produksjon av strukturen, og tilhørende måling og verifisering av strukturen.

Laerdal Medical lager dukker/pasientsimulatorer til medisinsk utdanning. Dette er meget avanserte dukker som i tiår har blitt anerkjent for sitt realistiske utseende og oppførsel. I den forbindelse ønsker bedriften å utvikle nye øyne som brukes i dukkene, slik at de blir enda mer virkelighetsnære. Denne oppgaven forsøker derfor å utvikle et fungerende konsept for Laerdal Medical, som innebærer at begge øynene har synkrone bevegelser i fire retninger (opp, ned, fram og tilbake), samt individuell åpning og lukking av øyelokk. I tillegg skal øynene ha iris som kan utvides og trekkes sammen. Hovedvekten av oppgaven handler om hvordan man kan lage en fungerende og funksjonell 3D-modell av konseptet, i henhold til hva Laerdal Medical ønsker. Modellen har blitt utviklet i tegneprogrammet NX, og det blir vist mange figurer underveis for å forklare hvordan de ulike delene og mekanismene settes sammen i modellen. Avslutningsvis gis en forklaring på hvordan det er tenkt at konseptet skal monteres, og hvilke materialer som kan brukes. Modellens bevegelser er testet ut, og det er gjort målinger for å se hvor stor plass modellen vil ta i dukkens hode.