Affordable price, high abundance of magnesium and high densities of hydrogenin the Mg-based hydrides attract interest to these hydrides tailored for hydrogenand energy storage applications. Ternary La-Mg-Ni hydrogen storage alloys withcomposition La3-xMgxNi9 (x = 0.8-1.2) form a new class of the materials for thenegative electrodes in Ni-Metal Hydride (MH) batteries. The electrochemical dischargecapacity of such alloys reaches 400 mAh/g which is 25 % greater than thatof the commercial AB5-type based electrodes, 315 mAh/g. The La3-xMgxNi9alloys crystallize with trigonal PuNi3 type of crystal structure. Magnesium replaceslanthanum to form the hybrid LaNi5 + Laves phase structures and favorablychanges the thermodynamics of the metal-hydrogen interactions allowingimproved performance of the advanced metal hydride battery electrodes.Differences in melting temperatures of lanthanum, nickel and easily evaporatingmagnesium and a complexity of the phase equilibria in the La-Mg-Ni systemcause difficulties in synthesis of the battery electrode alloys with controlled Mgcontent and a desired phase-structural composition.In present work a La2MgNi9 alloy was in focus. Its successful synthesis hasbeen achieved from the alloy melts containing 0-30 % of overstoichiometric Mgas compared to La2MgNi9 by use of Rapid Solidification performed at variousquenching rates, with a copper wheel rotation speed of 3.1, 10.5 and 20.9 m/s.They were analyzed by synchrotron X-ray diffraction (SR XRD) including in situstudies in hydrogen gas performed at Swiss-Norwegian Beam Lines at ESRF,Grenoble, and by Scanning Electron Microscopy (SEM) with electron probemicroanalysis (EPMA). Pressure-Composition-Temperature isotherms, hydrogenabsorption-desorption cycling and measurements of the electrochemical chargedischargeperformances were employed to characterize hydrogenation behaviorsof the studied alloys. These studies showed that the melt spinning of the alloycontaining 30 % weight excess of Mg quenched using wheel spin speed of 400 RPMallowed obtaining the most homogeneous sample with the optimal microstructureand phase-structural composition corresponding to the formation of La2MgNi9with the highest yield.Variations in magnesium content and selection of optimal conditions for the RapidSolidification process provide complementary possibilities in improving propertiesof the studied La-Mg-Ni alloys as hydrogen storage and battery electrodematerials and provide a possibility to upscale production of the battery alloys.This work was performed at Institute for Energy Technology and at Departmentof Materials Science and Engineering, NTNU.

The most active catalyst for oxygen evolution in PEM water electrolysis is ruthenium oxide. Its major drawback as a commercial catalyst is its poor stability. In a mixed oxide with iridium, ruthenium becomes more stable. However, it would be favorable to find a less expensive substitute to iridium. In this work, the dissolution potential and lifetime of mixed oxides containing ruthenium and tantalum are investigated. In order to effectively determine what effects tantalum and particle size have on stability, only a small amount of tantalum is used, and the catalysts are supported by antimony doped tin oxide, ATO. This leads to a very small particle size, and makes it possible to investigate small amounts of catalyst where little new surface is made available during degradation.Catalysts were prepared with the normal polyol method by reducing RuCl3 and TaCl5 in ethylene glycol, EG, before the metal particles were deposited on the ATO support. The catalysts were investigated electrochemically with cyclic and linear voltammetry. Furthermore, the lifetime of four catalysts were determined by chronoamperometry at 1.455V vs. RHE. The compositions and loading of catalyst on the support were determined by energy dispersive x-ray spectroscopy (EDS) and the particle sizes were measured with transmission electron microscopy (TEM).In one synthesis, the reduction time and temperature were increased from 3 hours at 170◦C to 4 hours at 190◦C in order to increase the reduction rate. While this had no effect on the Ta composition, the catalyst got a fraction of amorphous phase not found in any of the other catalysts. The amorphous Ru0.9Ta0.1O2 particles had the largest particle size and the highest stability of the ones investigated. 10wt% water was added to the synthesis of an ATO-RuO2 catalyst in order to increase the particle size, but no significant effect was observed. Larger RuO2 particles and amorphous Ru0.9Ta0.1O2 particles were obtained by collecting them as unsupported catalysts.The addition of tantalum has a negative effect on the catalytic activity. When Ta is present, the dissolution potential of Ru at around 1.45V is slightly increased, but the degradation rate is increased above 1.49V. A large particle size in RuO2 has a significant positive effect on stability.

Alkaline water electrolysis need a catalyst with low overpotential and high current densitiy for oxygen evolution in order to be a commercial viable hydrogen source in the future. Finding and establishing a correlation between electrocatalytic activity and charge carrier density will help towards finding an optimum catalyst for this purpose. Such comparisons have been made using theoretical values for charge carrier density, but the aim of this work is to use charge carrier data from experimental values.Five powders of La<sub>1-x</sub>Sr<sub>x</sub>CoO<sub>3</sub> (with compositions x = 0, 0.25, 0.5, 0.75, 1) were synthesized by solid-state synthesis and sintered to pellets. The pellet surfaces were investigated in alkaline solution (pH = 13) by cyclic voltammetry, polarization and impedance measurements. Polariza- tion curves with Tafel lines and Mott-Schottky plots were established. The powders and pellet surfaces were investigated by XRD, SEM, EDS, AFM and light microscope.The polarization curves revealed a volcanic behavior with an increase in catalytic activity from x = 0 up to x = 0.75 and then decreasing. The charge carrier density increased with increasing strontium doping. The resulting comparison gave figure 34. Surface investigation revealed much porosity. Because of corrosion, the surface area increased with measuring, and finding the real surface area and the roughness proved to be problematic.A volcanic behavior of the charge carrier density and electrocatalytic activity relationship were observed. Finding roughness factor values by measuring double layer capacitance measured by the cyclic voltammetry method and dividing by the nominal capacitance for a flat surface proved to be unsuccessful. Better synthesis and sintering procedures of pellets are needed to increase the density of the samples in order to decrease the roughness and the effect of corrosion.

Optimalization of PLD deposition of YSZ for micr-SOFC electrolyte applications by varying deposition pressure and target-substrate distance.Substrate used was Si-based chips and wafers (large area PLD), and the substrate temperature was held at 600. Dense films were obtained at 20 mTorr.

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.