Silicon undergoes oxidation at room temperature, causing a formation of an oxide layer on its surface. Gaining knowledge about the oxide layer formed during ageing, is valuable with regards to production of high quality ceramics, Si3N4, especially with for the slip casting process.In this work silicon powders were exposed to humid air at different temperatures for different periods of time. From the XPS analysis, the oxygen and hydroxide content were found to be higher for powders aged at higher humidity compared to powder aged at lower humidity. This was verified by the estimated oxide thickness, which was larger for powder aged at higher humidity. No obvious difference could be observed for short and long ageing time in low humidity atmosphere. Results from Raman spectroscopy showed a more amorphous powder after storage in humid air. A clear shift and broadening of the crystalline silicon peak were observed for powders exposed to air at low and high humidity. The powders aged in humid air were further reacted with water at pH 9.4 and temperature of 60°C. The onset time for hydrogen evolution was observed to be later for samples exposed longer times to humid air. This indicates that the reactivity of the powder decreases as the oxide layer formed during ageing develops. The amount of hydrogen evolved seemed to be dependent on the hydrogen evolution time rather than the time of exposure to humid air. This was verified by the surface area, which was about the same for all samples, showing only a slightly decrease for increasing exposure time. The oxygen content measured was linearly related to the surface area for the main section of the samples. Higher hydroxide content seemed to catalyse the aqueous oxidation reacting, resulting in an earlier onset time for hydrogen evolution and a higher hydrogen flow. This was stated by a higher surface area and higher oxygen content for these samples.Powder thermally treated, at 300 °C and 900 °C, were also investigated. XPS analysis showed a thicker oxide layer for powder treated at 900 °C. No hydrogen was formed in the aqueous oxidation of powder treated at 300 °C. This was verified by a low surface area.Regarding the slip casting of silicon powders, a defect free green body can be obtained by reducing the hydrogen formation. Based on the results found, this can be obtained by the formation of a passivation oxide layer on the particle surface, formed during ageing of the powders in humid atmosphere before processing.Higher humidity and longer ageing time seems to affect the development of the oxide layer formed on the surface more than low humidity and short ageing time. To minimise the hydrogen formation, it is crucial to be able to control the hydroxide concentration in the aqueous oxidation accurately.

I dette prosjektet er en barnevugge blitt designet. Vuggen tar utgangspunkt i en vippemekanisme utviklet av Terje Rølvåg ved Institutt for Produktutvikling og Materialer på NTNU. Målet med prosjektet har vært å utforme en estetisk og funksjonell vugge tilpasset vippemekanismen. Mekanismen skal bidra til å roe barnet ved hjelp av vugging ved optimal frekvens.Det ble uført en enkel segmentanalyse hvor ulike brukergrupper og forretningsideer ble drøftet før et utvalgt konsept ble videreført. Dessuten ble det foretatt et litteratursøk for å underbygge tidligere undersøkelser som antydet en frekvens på 1-1,5 Hz som optimal vuggefrekvens for babyer.Basert på det valgte konseptet ble kundekrav og -interesser identifisert for å kunne lage en adekvat kravspesifikasjon. Forskjellige løsninger er presentert før ett av designene ble tatt videre og modellert i NX.Forskjellige sikkerhetsstandarder ble gjennomgått for å sikre optimal kvalitet på sluttproduktet. Det endelige designet er basert på gjeldende sikkerhetsstandarder for vugger samt funn fra brukeranalysen.Prosjektet resulterte i fire ulike designforslag. Det vil være opp til veileder eventuelt å føre et av disse designene videre.

Denne masteroppgaven har tatt for seg undersøkelser av stål designet for lavtemperaurappliksjoner ved bruk av elektronmikroskop i kombinasjon med diffraksjon av tilbakespredte elektroner (Electron Backscatter Diffraction - EBSD). Målet med oppgaven var å bruke EBSD-teknikken i kombinasjon med in situ deformasjon og en spesiallaget kaldfinger for å kunne studere materialene ved lave temperaturer. To ulike stål ble undersøkt; et smidd finkornet strukturelt stål (F70) og et varmvalset supermartensittisk rustfritt stål (Supermartensitic Stainless Steel - SMSS).F70-stålet ble sveisesimulert for å oppnå en mikrostruktur tilsvarende interkritisk grovkornet HAZ (Heat Affected Zone). Dette ble gjort ved en tosykel sveisesimulering. Prøvestaver av materialet ble varmet opp med en ønsket makstempertur på Tp1= 1350°C og Tp2= 780°C. For å undersøke effekten av ulike avkjølingshastigheter ble halvparten av prøvestavene avkjølt med Dt8/5 = 5 sekund, og den andre halvparten med Dt8/5 = 15 sekund. Ved sveising av stål kan det dannes lokale sprø soner som martensitt/austenitt-faser (MA-faser). Bilder tatt i lysmikroskop viser at strukturen til sveisesimulert F70-stål består av martensitt og noe bainitt. MA-faser er lokalisert langs korngrensene.EBSD-teknikken krever at materialet på forhånd gjennomgår en tilfredsstillende prøvepreparering for å gi gode resultater. Det var tidligere etablert en tilfredsstillende prepareringsteknikk for SMSS. I denne oppgaven ble to ulike prepareringsmetoder testet på sveisesimulerte prøver av F70-stål, som er et forholdsvis nytt materiale. Metodene som ble testet var ionesputtering og elektropolering. Preparerte prøver ble undersøkt med EBSD for å analysere kvaliteten på prepareringen. Det viste seg at MA-fasene reagerte annerledes på prepareringen enn resten av strukturen, og det var derfor vanskelig å få disse fram på EBSD-skann. De to prepareringsmetodene ga også forskjellige utfall for andel austenitt (g-fase) i stålet. Da det i hovedsak er MA-fasene som er interessante ved in situ undersøkelser ble det besluttet å ikke gjennomføre disse på F70-stålet, da en tilfredsstillende preparering må etableres først. Ved bruk av EBSD-teknikken kan orienteringsdataene som lagres behandles i programvaren TSL OIM Analysis 5.32, som tilbyr ulike renseoperasjoner. Grain CI Standarization gir alle punktene i et korn, innenfor en gitt vinkeltoleranse, samme CI-verdi som den maksimale CI-verdien funnet blant punktene i dette kornet. Det er også mulig å legge på et CI-filter som fjerner alle punkter med en CI ≤ 0,05, og erstatter disse med svarte eller grå piksler. Effekten av disse to operasjonene ble undersøkt på et EBSD-skann av SMSS tatt ved romtemperatur, uten noe form for deformasjon. Renseoperasjonene førte til at 8,1 % av alle punkter ble fjernet. 3,8 % av disse var av g-fasen, som utgjør kun 17,3 % av skannet før renseoperasjonene ble benyttet. Punkter som fjernes ligger i hovedsak i forbindelse med korngrenser eller øyer av restaustenitt. For SMSS som inneholder rundt 20 vol.% restaustenitt i opprinnelig (dvs. interkristisk glødet) tilstand, ble det gjennomført undersøkelser av deformasjonsindusert fasetransformasjon ved bruk av in situ strekktesting med påfølgende EBSD karakterisering. Undersøkelsene ble utført ved romtemperatur og -80°C. Et spesiallaget strekkbord ble montert på SEM (Scanning Electron Microscope) stagen med prøven fastmontert, og en kaldfinger ble brukt for å kjøle ned prøven. EBSD karakteriseringen ble foretatt uten deformasjon og ved 1, 2, 3 og 4 % forlengelse. En sammenligning av resultatene ved romtemperatur og -80°C ble deretter utført. Det ble konkludert med at øyer av restaustenitt transformeres til martensitt som følge av plastisk deformasjon i større grad ved -80°C, som følge av høyere termodynamiske drivkrefter for reaksjonen. Ved romtemperatur var det mulig å verifisere at martensitten som ble dannet oppfyller Kurdjomov-Sachs kriteriet som beviser at den er korrekt indisert. Dette var vanskelig å verifisere for lavtemperatursforsøkene, da skannene har en mye lavere kvalitet.

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.

This thesis is a feasibility study of the possible application of magnesium alloys forfuture magnesium-ion batteries. It investigates dierent alloys and characterizesthem with respect to internal resistance, overpotentials and the reversibility of theelectrochemical reaction. SEM and EDS studies of used electrodes have also beencarried out. It has been showed that alloys, easier to handle and at a fraction of thecost, can be used with equal or better performance than pure Mg. The seeminglysuperior alloy, AZ61 exhibits a coloumbic eciency close to 100%, at higher chargerates than pure Mg.

K0:485Na0:485Li0:03Nb0:8Ta0:2O3 powder has been prepared by spray pyrolysis ofaqueous solutions of K/Na/Li nitrates mixed with water soluble Nb and Ta precursors.The as-prepared ceramic powder was calcined at 600 °C to remove any organic residuesafter the spray pyrolysis process. Different milling methods for the calcined powderswere attempted, revealing dry planetary milling to be the most suitable milling method.The powders were characterised using scanning electron microscopy. A complete millingprocess was developed based on sufficient destruction of the egg-shell like agglomerates from the spray pyrolysis process, avoidance of flake formation and reproducibility.Sintering was attempted using three different sintering methods, all using the reverse crucible method to limit the amount of alkali evaporation. An optimal temperature range was found for each of the three, achieving densities in the range of 94-97%. The microstructure of the different samples was explored by polishing the samples and investigating the surfaces by scanning electron microscopy. It was found that the average grain sizes were in the range of a few microns, with large variations in the broadness of the grain size distribution when comparing different sintering methods. For two of the three sintering methods a standard deviation of less than 0.3 micron is reported. An EDS analysis was performed, and it was found that all the samples demonstratecompositional homogenity.Dielectric testing was performed on the samples sintered using the three differentsintering methods. Polishing of the sample surfaces and storage in dessicators had tobe performed in order to avoid moisture influence and achieve reproducibility. Thepiezo- and ferroelectric effect was observed for all the different sintering methods, along with coercive fields in the range of 669 - 889 Vmm and remnant polarizations in the range of 16 - 29 C/cm2 , depending on the sintering method used. A strictly monotonic relationship between average grain size and the coercive field was identified. The normalized strain d*33 was found to be in the range of 230 - 330 pm/V , after poling using an electric field of 4 kVmm at 100 °C. It is argued that on the basis of the present results,K0:485Na0:485Li0:03Nb0:8Ta0:2O3 has potential as a leading candidate for environmentally friendly ferroelectric materials, and spray pyrolysis seems an excellent choice of synthesis method.

High quality surface passivation is important for the reduction of recombination losses in solar cells. In this work, the passivation properties of amorphous hydrogenated silicon nitride for crystalline silicon solar cells were investigated, using electrical characterization, lifetime measurements and spectroscopic ellipsometry. Thin films of varying composition were deposited on p-type monocrystalline silicon wafers by plasma enhanced chemical vapor deposition (PECVD). Highest quality surface passivation was obtained for silicon-rich thin films, where a surface recombination velocity of 30 cm/s was obtained after a heat treatment corresponding to the industrial contact firing process. Electrical characterization of the interface between silicon nitride and silicon was performed by capacitance and conductance measurements. Several challenging aspects related to the interpretation of these measurements were investigated in detail, including charging and discharging, leakage currents, and frequency dependent capacitance.

Multiferroic materials combine two or more ferroic orders such as ferroelectricity, ferromagnetism and ferroelasticity. They have a great interest for the development of the next generations of digital electronic memory devices. Bismuth ferrite has shown to posess both ferroelectric and magnetic order at room temperature, which makes it both scientifically and comercially interesting.The negative impact on the environment by using lead in mass-produced units has made development of lead-free piezoelectric materials for use in sensors, actuators and transducers prioritized and samarium substituted bismuth ferrite has shown to posess a piezoelectric response high enough to be considered for commercial applications. In this project work, 10mol% samarium substituted bismuth ferrite, Bi_{0.9}Sm_{0.1}FeO_{3}, powders have been synthesized using a wet-chemical method and calcined to a range of temperatures to achieve a range of nanocrystalline sizes in the powders. These powders has been investigated using X-ray diffraction (XRD), Rietveld refinement and differential scanning calorimetry (DSC). The powders have also been milled, pressed and sintered to pellets for ferroelectric and piezoelectric testing. The crystal structure was found to belong to the R3c group as for bismuth ferrite, BiFeO_{3}, but the unit cell geometry is changed slightly, and the ferroelectric polarizability is lowered in the case of samarium substitution. This fact is interesting regarding piezoelectricity by thereby increasing the ability to achieve a higher piezoelectric response. No results were achieved from ferroelectric and piezoelectric measurement due to the conductivity found in the sintered pellets were too high, probably due to secondary sillenite phases found in the material. There has been found a finite size effect of a decrease in unit cell volume and tetragonality, of which the decrease in volume is contradictory to the expectations. There is also clear finite size effects on the decrease of cooperative displacement of cations, a measure for the polarization, and for the lowering of the ferroelectric phase transition temperature. The finite size effect for the ferroelectric phase transition has not been reported before. The magnetic phase transition temperature also show a decrease as a clear finite size effect. A linear relationship between electric polarization and magnetic ordering has also been observed in this project. The results from this project contributes to the understanding of material properties of BiFeO_{3} and derived compositions by an investigation of substitution effects and finite size effects. The results presented here motivates further research on these materials.

A carbon powder containing carbon nanocones was used as an anode material in lithium ion batteries. The powder was also treated in different ways, chemically, with microwaves, and with heat. The carbon powder was tape casted onto copper before being assembled into batteries with lithium metal as the counter electrode. The batteries were characterized by measuring the capacity during cycling. X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the powders and casts. Fourier transformed infrared spectroscopy (FTIR) was done to both the carbon powder and the used anode material.The solid electrolyte interface (SEI) was characterized and found to contain components like ce{(CH2OCO2Li)2}, ce{Li2CO3}, and ce{ROCO2Li}. These are in accordance with what would be expected from results in the literature. SEM was used to find surface orientation of the basal and edge planes, and XRD was used to find the crystallinity.parThese results showed that more graphitized powders were better with emphasis on irreversible capacity. The treated carbon nanocone powders had higher capacity than the graphitized ones, but also higher irreversible capacity.

In this report, 10 at% lanthanum was introduced to the perovskite structure of bismuth ferrite at the expense of bismuth through a modified Pechini wet chemical method. Green body powders were calcined at several temperatures, and the lattice parameters for each size were found by Rietveld refinement of X-ray powder diffraction data. The parameters displayed strong size-dependent properties, and the rhombohedral distortion from the cubic structure was reduced by decreased particle size. With decreasing crystallite size, the Néel temperature decreased and the cooperative cationic displacement (s - t) showed size dependence at crystallite sizes below 30 nm. A size-dependency was also observed in the Curie temperature.