ABSTRACT

The aluminium smelter at Hydro Sunndal has experienced problems with an unexpected increased loss of AlF3 from the electrolyte when using a certain quality of alumina. One hypothesis considered was that the fluoride loss was a direct result of unusually high HF formation when the quality was added to the cryolitic melt. This work has set out to study the HF formation potential of three different industrial alumina qualities. Alumina A was an alumina quality that worked well in the smelter. Alumina B was the alumina quality where the aforementioned drop in AlF3 was observed and alumina C, made by the same producer, controversially did not to exhibit the same loss at smelter. The present work has been divided into two parts: a characterisation section, where the aluminas have been characterised by techniques such as LOI, TGA, DSC and XRD, and an experimental section, where the industrial aluminas were added to a cryolitic melt. The HF formation and the corresponding H2O concentration were measured in-situ using a tunable diode laser during the alumina additions to the cryolitic melt. Through this work it has been found that both primary and secondary alumina A form less HF than alumina B and C. The LOI, TGA and XRD characterisation has shown that alumina B and C contain a substantial amount of gibbsite, whilst the gibbsite level in alumina A is negligible. A clear correlation between the quantity of moisture found through LOI characterisation and HF formation has been found. It has also been shown that all types of moisture found through LOI testing contribute to HF formation; both physisorbed and chemisorbed types, as well as structural hydroxyl. From the present work it cannot be explained why alumina B caused a drop in AlF3 in the electrolyte, whilst alumina C did not. One explanation postulated is that alumina C has better scrubber efficiency than alumina B. Examining this hypothesis has been outside the scope of this master work. If variations in scrubber efficiency for the two aluminas fail to explain the drop in AlF3, the solution may be found in parameters outwit the alumina quality e.g. weather conditions at the time of production or storage conditions at the calciner.

Si-nanowires are being introduced as an attempt to decrease the high recombination rate present in silicon based thin-film solar cells by employing radial pn-junctions instead of conventional planar pn-junctions. Previous publications have also shown an additional increase in the amount of absorbed light when covering a silicon-substrate in silicon nanowires which may result in a further increase in the total efficiency of a thin-film solar cell. Successful growth of Si-nanowires has earlier been performed by Chemical Vapour Deposition (CVD), employing gold (Au) as catalytic material. Au is a very stable catalytic material for nanowire growth but Au-residues are unwanted in solar cell applications, and the current experiment has therefore investigated aluminium (Al) as an alternative catalyst material. However, stable Al-catalysed growth has been proven to be difficult and is assumed to be mainly due to rapid oxidation of Al to Al2O3. Most of the nanowires were short, tapered and consisted of worm-like structures. Several unsuccessful in-situ NH3-based cleaning (CVD) processes were attempted. Tin (Sn) was also attempted as a protective coating for the Al-film in order to protect Al from exposure to air during sample transport, without any luck. As solar cells require both p-doped and n-doped sections in order to form pn-junctions, initial investigations were performed on the effect from the addition of dopant gases (B2H6 and PH3) on nanowire morphology. The addition of B2H6 to the gas flow seemed to have much larger effects than PH3 on the nanowire morphology compared to intrinsic nanowires. Both gases resulted in a continuous reduction in the average nanowire length with increasing dopant⁄SiH4 ratios, ultimately leading to a complete inhibition of nanowire growth. The highest usable dopant⁄SiH4 ratios before complete growth-inhibition were found to ~10^-3 for B2H6 and ~10^-1 for PH3. An undesirable tapering effect was also found when adding B2H6 to the gas-flow, resulting in radial growth of amorphous silicon on the nanowire walls already at the lowest dopant ratio (~10^-5). This may complicate the use of B2H6 as a dopant gas for p-type nanowires. Ignoring the fact that the addition of PH3 to the gas-flow reduces the nanowire growth rate PH3 may be assumed to be a good alternative for n-type doping of nanowires as no further effects on the nanowire morphology is observed. The actual implementation of dopant atoms into the nanowire structure may be determined by measuring the electrical resistivity in the nanowire, and a possible four-contact structure has been designed and partly optimized for this purpose. The contact structure has been designed in three layers where two of them are produced by photolithography while the smallest layer by electron-beam-lithography. Note that the structure has not been finalized because of time limitations. Some optimization of the four nanowire contacts remains as some final lift-off problems appeared, and is assumed to be related to either an incomplete development of the smallest features or an observed resist-bubbling because of high Titanium (Ti) deposition temperature. However, a robust three-point alignment procedure has been investigated and found useful for producing accurate contacts to single nanowires and leads to the conclusion of a promising structure.

The metabolic insertion of titanium into the biosilica frustules of the pennate diatom Pinnularia sp. and the centric diatom Coscinodiscus wailesii was explored in the present study. A total of five titanium incorporation experiments were conducted on Pinnularia, in addition to five control experiments. Titanium dissolved in HCl was co-delivered with silicate dissolved in NaOH to silicate replete and silicate deplete Pinnularia cultures over a 10 hour delivery period. Cell number, silicate and titanium concentration, Quantum Yield, Instantaneous Chlorophyll Fluorescence and pH was measured regularly throughout the experiments. The diatoms were left to consume the delivered silicate/titanium for 62 hours after delivery was completed before they were harvested and rinsed to remove the organic material. The resulting biosilica frustules were analyzed with (Scanning) Transmission Electron Microscopy to investigate the frustule structure, Inductively Coupled Plasma Mass Spectrometry to measure the elemental composition of the frustules and Energy Dispersive Spectroscopy to determine the location of the elements in the frustules. Quantum Yield measurements were conducted to obtain information about the Pinnularia photo system condition, and high Quantum Yield values were interpreted as an indication of a good overall physiological state of the cell. It was found that a combination of high Quantum Yield values and silicate depleted cultures produced the highest titanium content in the Pinnularia frustules (1.3 wt% relative to silicon). Furthermore, EDS analysis revealed that titanium was not evenly distributed throughout the biosilica frustule. The relative titanium content in the Pinnularia frustules was higher in the biosilica at the base of the large pores covering the frustule surface than in the biosilica between the pores. This was in accordance with findings reported in literature. The observed inhomogeneous distribution trend was found to apply also to phosphorous and iron present in the titanium-doped frustules. This observation has not been previously reported.Cell aggregation of the Pinnularia cultures was observed upon silicate/titanium addition. Based on results from control experiments there was reason to believe that the aggregation was triggered by titanium, but the explanation for this cellular response as well as its effect on titanium uptake and incorporation was not determined. Three titanium incorporation experiments were conducted in the proof on concept study on Coscinodiscus . Titanium dissolved in HCl and silicate dissolved in NaOH was co-delivered with a pipette once a day for three, five and seven days. On the day following the final addition, the diatoms were harvested and rinsed before they were analyzed in the same manner as Pinnularia. The experiments on Coscinodiscus revealed that metabolic insertion of titanium into the frustule biosilica was possible, but due to the small maximal titanium content achieved (0.03 wt% relative to silicon) and the slow growth rate, Coscinodiscus was not considered an optimal choice of diatom species for titanium incorporation purposes.It was not possible to rule out whether the frustule structure in any of the two species had been altered or impaired as a consequence of titanium exposure. Structural flaws were observed in frustules with and without titanium incorporated. A faint irregular pattern on the nanoscale was observed in Pinnularia frustules containing titanium. No such pattern was observed in titanium free frustules.The amount of boron measured in the frustule biosilica was higher than the regular dopant concentration in boron-doped silicon. The boron content in Pinnularia was found to be on average 0.1 wt% or 0.28 atomic % relative to Si, while the average in Coscinodiscus was nearly twice as high. Without further manipulation, this high boron natural boron concentration makes diatom frustules unusable for doped semiconductor purposes.Future work should involve reproduction of the obtained results with more replicates, as well as larger culture volumes and, in the case of Coscinodiscus in particular, longer time scale. Titanium uptake and incorporation studies should if possible be performed on single Coscinodiscus cells. Multiple continuous silicate starvation and titanium/silicate delivery cycles should be tested to determine if it is possible to incorporate titanium into a larger fraction of the culture population, as well as to increase the maximum amount of titanium incorporated into one frustule.Aggregation of Pinnularia diatoms should be further investigated to determine reason for the observed reaction, the effects on titanium uptake/incorporation and possible strategies to prevent it from occurring. Pinnularia frustules unexposed to titanium should be inspected in order to determine if the iron and phosphorous distribution pattern observed in the titanium-doped frustules is present in titanium-free frustules as well.A completely artificial culture medium and plastic cultivation containers should be applied to explore how the boron content of diatom frustules can be tailored by controlled delivery of boron to the culture medium.

Monolayer colloidal crystals are formed using silica- and polystyrene beads and used as templates in nanosphere lithography for creating various hexagonal periodic structures intended for light harvesting in crystalline silicon solar cells. Specifically, arrays of silver islands for plasmonic scattering, dimples for use as seeds in electrochemical etching, and silicon cylinders diffraction gratings are fabricated and investigated. Where suitable, optical measurements are done to complement the structural characterisation.

Sperre AS produserer i stor grad hele ROV konstruksjonen sin i aluminiumslegeringen AA6082-T6. Dette er et velegnet materiale for oppgava, men med noen mangler.Denne oppgava fokuserer på elektronikksylindrene til ROV-en, disse er per idag produsert i den ovennevnte aluminiumslegeringa. Man vil i framtida ned på store havdyp, ned mot 6000 meter. Når man skal så dypt vil disse elektronikksylindrene påføre konstruksjonen mye vekt og volum, både direkte pga større masse aluminium og indirekte ved at man trenger mye oppdriftsmateriale.Ved å benytte seg av kompositt og egna produksjonsmetode vil man kunne produsere samme tanken, med svært mye bedre egenskaper. I denne oppgava er det sett på metall-innerforing for spinning av kompositt på utsida og derfor oppnå ønska styrke, samt generelt design av sylinderen. Det er også foreslått design uten innerforing, men da produsert ved hjelp av kompositt-duk. Hvilket materiale som er best egna til innerforing og hvilken kompositt som har de beste egenskapene er også vurdert.Som deloppgave er det utført mekanisk testing på sveist aluminiumslegering for å verifisere DNV standardencite{DNV271}, samt vurdere om man ved forenkla varmebehandling kan gjenopprette noe av styrken til metallet.

The governing purpose of the thesis is to develop a chair concept based on a tilting mechanism called VAPAC. This chair concept has many potential ergonomic and environmental benefits that should be included and developed in the design. The report starts with an analysis of different segments within the chair market. Based on an evaluation, office chairs was chosen as the segment for the VAPA-Chair. Due to an interesting tilting idea suggested by the Supervisor/Concept originator, a test rig was built in order to try out a chair concept using straps for the tilting mechanism. This assignment was not originally one of the main tasks in the problem definition of this thesis . Due to curiosity and expectations for the idea, it was chosen to include this assignment in the thesis. A user survey reviled that this tilting idea offered an exciting and comfortable sitting experience. The concept using straps as tilting stringers was therefore developed further and important lengths and angles regarding the tilting mechanisms were settled. A problem occurred due to the risk of the chair tilting completely around if the user leans too much forwards or backwards in the chair. Making the stringers stiff so that they can withstand pressure when introduced to a load solved this problem. The tilting function was still the same as with the regular straps because the stringers were attached in joints, allowing the stiff straps to rotate freely. An Idea using turnbuckles as stringer was developed. This solution ensured the required stiffness as well as possibilities for height adjustment and a stop mechanism for the tilting. The terms “Ergonomic” and “Environmental friendly” is introduced, and important elements from these was set as requirements for the chair concept. Design sketches, doodling and brainstorming generated ideas for different concepts. Different functional concepts was introduced and evaluated as sub-parts of the chair. One concept was chosen for each part resulting in a holistic concept for the chair.The preliminary work results in a final concept, which is presented in the form of hand sketches and a 3D model using the program NX 7.5 Mechatronics . A lot of time was spent on modeling a simple and functional design with ergonomic and environmental friendly solutions.A material analysis was conducted regarding the bearing structure of the chair using the Life cycle analysis tool Eco-indicator 99. The analysis compared aluminum and steel. Due to low environmental impact using recycled aluminum, this material was chosen for the VAPA-Chair. A life cycle analysis was also conducted on the chair using the program CES Edupack. The analysis showed that the part of the chair’s lifecycle that impacts the environment the most, is the production of materials. Based on these results, it is recommended that the VAPA-Chair should focus on weight optimization of the chair and use as much recycled aluminum as possible in the production. Based on results from the report, a list of recommendations for further work is presented.

Bakgrunnen for denne oppgaven er et ønske fra tilhengerprodusenten Tysse om å utvikle en mer effektiv metode for å beregne levetid i forskjellige punkter på deres tilhengere. Dette skal gjøres ved å bruke strekklapper i stedet for destruktive metoder slik som brukes i dag. Motivasjonen er å spare tid og penger. Masteroppgaven er basert på prosjektoppgaven skrevet av samme studenter semesteret i forveien. Da masteroppgaven startet var teknologi og utstyr undersøkt og kjøpt inn. Masteroppgaven skal ta dette utstyret til en fungerende løsning. Dette kan i grove trekk deles inn i følgende punkter:•Tilpassing av måleutstyr•Materialtesting•Utvikling av framgangsmåteMåleutstyret var kjøpt og mottatt da masteroppgaven startet. Brokomplettering ble evaluert og en løsning ble valgt. Dette åpnet for feilsøking, og for å bli kjent med utstyret før testing av utstyret mot testriggen hos Tysse. Besøket bekreftet at valgt utstyr i prosjektoppgaven faktisk fungerte under forholdene. Kompletteringsenheter ble testet under realistiske forhold, noe som førte til utvikling av et nytt, mer robust design. Festemekanisme for måleutstyret mot tilhengeren ble prøvd ut sammen med fuktsikringen. Etter besøket hos Tysse ble det reservert tid i utmattingslaben der prøver av stålet i tilhengeren ble testet. Dette ble gjort for ytterligere å sikre realistiske resultater fra levetidsberegningene. Prøver ble maskinert, og materialstyrke ble funnet ved strekktesting. Strekktest og utmattingstest ble gjennomført basert på ISO standardene ISO 6892 og ISO 1099. Estimert SN kurve ble sammenliknet med data fra utmattingstestene. Framgangsmåten for testing av tilhengere ble revurdert i masteroppgaven. Den eksisterende metoden fra prosjektoppgaven ble satt opp mot en ny og enklere løsning som skulle bli bedre tilpasset Tysse. Programvaren for bearbeiding av datamateriale ble videreutviklet og ferdigstilt. Brukermanual som beskriver framgangsmåten steg for steg ble utviklet.Sluttresultatet ble levert til Tysse i Bergen med demonstrasjon og opplæring av dem som skulle bruke systemet videre. Det ble også lagt fram et forslag til videreføring av systemet.

The report is written to show as to what extent test-driven development (TDD) and continuous integration (CI) can be used on KBE models and how a unit testing framework for KBE models can be developed.Test-driven development (TDD) and continuous integration (CI) has changed the way software is tested. Software testing was often a separate process at the end of a project. It is now being worked on during the entire development period. TDD and CI relies on unit tests. Unit tests are done by dividing the code into the smallest possible units and testing each of them independently. This master’s thesis asks how these practices can be used for testing knowledge based engineering (KBE) models.A unit testing framework for the Adaptive Modeling Language (AML), AUnit, has been developed. It is explained in detail and an introductory guide to using AUnit for testing KBE models in AML is included. AUnit was used to perform TDD and CI on different KBE models, both creating new models and testing existing ones. Testing KBE models differ to a large degree from testing regular object-oriented software. Different approaches for unit testing and TDD has been performed on several KBE models. It was concluded that the basic attributes in KBE models cannot be unit tested in a sensible way. This includes adding any superclasses and simple parameters like height and width. Without including these attributes, unit testing cannot fully be performed on KBE models using AUnit. However, the models can highly benefit from having unit tests for the logic in the model, which is where the most severe bugs will be. When the attributes are implemented in the model, test-driven development (TDD) can be performed on the models.Automatic continuous integration (CI) has been performed on a KBE model andthe basic principles of CI have been accounted for. CI for KBE models does notdiffer much from other software projects, so its focus is reduced.

Gjennom dette arbeidet, er nanomekaniske kompresjonsegenskaper undersøkt for tre forskjellige materialer: To stål legeringer og et renjern. Pillarer av varierende størrelse, fra diameter 100nm til 2um, er fabrikkert ved bruk av FIB (Focused Ion Beam) i NTNU nanolab, etterfulgt av kompresjonstesting. Hvorvidt størrelsen til pilarene påvirker de mekaniske egenskapene, er gjennomgående undersøkt for alle tre materialene, med spesielt hovedvekt på en-krystall renjern. «Small is stronger» er et velkjent utsagn i micro skala verden, og er diskutert videre her for hvert materiale. F70 er en arktisk multifase ståltype, hvorpå lokale egenskaper i korngrense og matrix er undersøkt. Lokale soner i dette stålet er korngrenser bestående av MA-partikler (Martensitt og rest-Austenitt) og matriksen som består av fraksjoner av bainitt, martensitt, feritt og rest-austenitt. Stålet er varmebehandlet i to sykluser for å simulere ICCGHAZ i sveisesoner, hvorpå avkjølingshastigheten i temperatureintervallet fra T=800 - 500°C er satt til 5 sekund for en prøve, og 10 sekund for en annen prøve. Avkjølingshastigheten avgjører således de bruddmekaniske egenskapene, som er undersøkt ved nanomekanisk kompresjons testing. Pilar størrelsen er 250nm, 450nm og 1um. Resultatet indikerer at 5 sekunds prøven utviser høyere styrke og seighet. Størrelseseffekten er ikke fremtredende før en kritisk pilar diameter på 250nm er nådd. Dette stålet er undersøkt som en del av prosjektet Arctic Materials Group på SINTEF.Et to-fase stål bestående av martensitt korn i en matriks av feritt er undersøkt som en del av EU-prosjektet ved NTNU. To forskjellige prøver er undersøkt, hvorpå forskjellen skyldes legeringsinnhold av 0.05wt% Nb i den ene prøven, og ingenting i den andre. Legeringselementet øker både duktile egenskaper og styrken, på grunn av finfordelte utfellinger av karbider og redusering av kornvekst. Single-slip orienteringen (5 2 11) i feritt fasen er i hovedfokus, men martensitt fasen er også undersøkt. Fra resultatene kan det konkluderes med at innhold av Nb hever styrken og duktiliteten til materialet markant. Pillar diameter testet er 500nm og 1um. Størrelseseffekten kan ikke påvises eller avkreftes, da det ikke er undersøkt nok pillar størrelser til å trekke en absolutt konklusjon. Tre forskjellige orienteringer av 99.998% rent bcc-Jern er undersøkt: Multi-slip orientering (111) og (110), sammen med en single-slip orientering (235). Hovedfokuset ligger i å undersøke størrelseseffekten av en-krystall bcc-Fe, og om effekten av single-slip i forhold til multi-slip systemer påvirker resultatene. Kompresjons testing avslører at det er en fremtredende størrelseseffekt tilstede i alle tre orienteringer. Styrken til (111) orienteringen er høyere jevnt over sammenlignet med de to andre orienteringene, selv om størrelseseffekten er mest fremtredende i (235). Den økte styrken som de minste pillarene utviser, er således ikke påvirket av mengden av tilgjengelige slip-systemer. En beskrivende ligning for størrelses-effekt sensitiviteten er τ = D-n, hvor størrelsen på n indikerer sensitiviteten. For dette renjernet ligger verdien av n i samme området som for fcc metaller, altså en markant størrelseseffekt. Skjønt, er deformasjons mekanismen i fcc og bcc grunnleggende forskjellige. Den observerte styrke økningen, konkluderes å være forårsaket av atermale prosesser, eller ved skru-dislokasjoners grad av mobilitet. Pillar størrelsen varierer fra 100nm, 500nm, 1um og 2um. Det kan derfor konkluderes med at det er en sterk størrelse effekt i bcc-Fe. For å kunne forstå de lokale egenskapene i komplekse mikrostrukturer, er det først og fremst avgjørende å forstå deformasjonsmekanismen i rene en-krystaller. En god teori for plastisk deformasion på sub-mikro nivå er fremdeles ikke fremkommet og validert både eksperimentelt og data simulert. Når dette skjer, kan man være i stand til å forstå effekten av komplekse gitterstrukturer og legeringsinnhold, på nanomekaniske plastiske egenskaper. Med andre ord, man må tilnærme seg problemet fra en bottom-up perspektiv. Koblingen mellom datasimuleringer og eksperimentell testing på sub-mikronivå, må gjøres sterkere. Inntil dags dato, er mye av dette universet fremdeles uutforsket, og kun mindre forstått. Derfor kan du bruke denne oppgaven som ditt springbrett inn i verden av nanoskalerte materialeventyr!