Lists, reliquaries and angels in the music and the modern world/ Tombeau pour New York

Umberto Eco states that the list is the origin of culture, a way of making infinity comprehensible. Lists and catalogues are a way of creating order though history. I am currently, as a composer, working on a piece for choir using a list of angels as its text. Lists of angels deal with infinity, the list as such converges the three different monotheistic religions under the same roof. In my research I have tried to create a short overview of the history of lists in music, along with the musical presentation of angels in music - a subject that has fascinated many composers. Composers of last century such as Arnold Schoenberg, Oliver Messiaen and Karlheinz Stockhausen, to mention just a few, dealt with the representation of the angelic and divine in their music. Their different religious backgrounds suggested different strategies in their works dealing with angelic subjects

Reformering av naturgas för fastoxidbränsleceller

This work studies the reforming of natural gas for use in solid oxide fuel cells (SOFC). The aim of the thesis was to construct a reformer feeding reformate gas to a SOFC test station. The reformer should be able to operate in steam reforming, catalytic partial oxidation and anode off-gas recycling mode and in a wide temperature and gas flow range. SOFCs are seen as one of the promising energy conversion technologies. A variety of hydrocarbons are suitable as fuels, but it is often sensible to use a pre-reformer which convert the fuel into a hydrogen-rich gas stream. The thesis literature part gives an detailed overview of fuel cells and reforming methods. The experimental work covers the construction process, including dimensioning of the reformer according to the specifications of the test station and reactor design to optimise heat transfer. A precious metal catalyst was chosen for the reformer. Methods for avoiding carbon formation were studied. In addition, a Comsol Multiphysics computer simulation was constructed to demonstrated the couplings between heat and mass transfer and chemical reactions in the reformer. The performance of the reformer was tested in all reforming modes. The gas composition of product gas was analysed by gas chromatography and compared to calculated equilibrium values. Additionally, the catalyst stability was tested in a 190 hour long test run in steam reforming. All measured gas compositions matched closely with the calculated values. The identified deviations were small and to no harm in practical use. The heat transfer in the reactor was considered optimal and the operator can control the outlet gas temperature by setting the furnace to the targeted temperature. No signs of degradation were seen in the stability test. According to this study, the performance of the reformer is optimal in a wide operation range and this reformer design is suitable to be used in fuel cell research

Kiinteäoksidipolttokennoston komponenttien ja karakterisointimenetelmien kehitys

The public defence will be organised via Zoom on 4.12.2020 12:00 – 16:00. Here is the link to the event: https://aalto.zoom.us/j/68124888950Solid oxide fuel cells (SOFCs) are a promising technology to reduce energy-related carbon dioxide emissions and combat climate change. Benefits include high efficiency, low emissions and flexibility in fuel choice. However, market penetration is delayed by higher cost levels compared to conventional energy production methods and further development is needed. This thesis focuses on selected development needs: protective coatings for metallic interconnects to migitigate chromium migration, hybrid compressible stack sealing materials, and characterization methods to replicate stack conditions. Stack characterization should be performed with methods that replicate the real operation conditions as closely as possible, including fuels and reforming conditions. A fuel feeder for a SOFC test station was constructed for pre-reforming of natural gas, with the aim of being a versatile research tool. The fuel feeder was able to operate with several reforming techniques and in a wide temperature and gas flow range. The outlet gas composition can be predicted by the outlet gas temperature. Other developed characterization tools include a measurement method to determine fuel utilization and temperature distributions in stacks in situ with electrochemical impedance spectroscopy. The method was demonstrated on a real stack and its results were in accordance with analysis based on cell voltage measurements. The characterization method could aid in validating stack design. Manganese-cobalt oxide coatings for metallic interconnects were developed and characterized with a novel measurement method that replicates the stack conditions. The developed method offers the same contacting materials, electrical contacts, chemical interactions and chromium migration mechanisms as in stacks. Additionally, the setup enables post-test analysis of chromium migration through the coating with the same sample. Mn-Co oxide coatings deposited with various techniques were evaluated with respect to area specific resistance (ASR), coating microstructure and chromimum retention. Coatings deposited with physical vapour deposition (PVD) showed lowest ASR and a high chromium retention. These could be applied as such in stacks. The best performing coatings were found to be dense and well adhered to the substrate. Hybrid seals with a compressible core and surface glass layers were developed and tested in stacks. The seal material showed lower leak rates at lower compressible stress than uncoated compressible seals. It was found that the leak rate through hybrid compressible seals depends mainly on gas composition instead of overpressure and is mostly diffusive by nature. Interactions between hybrid seals and stack components were studied in an in situ stack test. No significant material interactions were found and the developed material was considered to be suitable for SOFCs. The results have been commercialized by Flexitallic Ltd.Kiinteäoksidipolttokennot (SOFC) ovat lupaava teknologia energiatuotannon hiilidioksidipäästöjen vähentämisessä ja ilmastonmuutoksen torjumisessa. Sen etuja ovat korkea hyötysuhde, vähäiset päästöt ja monipuolisuus polttoainevalinnassa. Käyttöönottoa haittaa korkeampi hintataso perinteiseen energiantuotantoon verrattuna ja lisäkehitystä tarvitaan. Väitöskirja keskittyy valittuihin kehitystarpeisiin: metallisten virtauskanavalevyjen suojapinnoitteisiin kromihöyrystymisen vähentämiseksi, kokoonpuristuviin kennoston hybriditiivisteisiin ja todenmukaisia käyttöolosuhteita jäljitteleviin karakterisointimenetelmiin. Kennoston karakterisointi tulisi suorittaa menetelmillä, jotka jäljittelevät todellisia käyttöolosuhteita, mukaan lukien polttoaine ja sen esikäsittely. Työssä kehitettiin SOFC testiasemaan maakaasun esireformeri, tarkoituksena toimia monipuolisena tutkimusvälineenä. Esireformeri toimi eri reformointimenetelmillä ja laajalla lämpötila- ja kaasunvirtausalueella. Tuotekaasun koostumus voidaan määritellä ulostulolämpötilan perusteella. Toinen kehitetty karakterisointimenetelmä on sähkökemialliseen impedanssispektroskopiaan perustuva in situ mittausmenetelmä kennoston lämpötila- ja polttoaineen käyttöastejakauman määrittämiseen. Menetelmää käytettiin kennostokarakterisoinnissa ja tulokset olivat yhteensopivat kennojännitteiden perusteella tehdyn analyysin kanssa. Menetelmää voi käyttää apuna kennostorakenteiden tutkimuksessa. Työssä kehitettiin metallisten virtauskanavalevyjen mangaani-kobolttioksidisia suojapinnoitteita. Nämä karakterisoitiin uudenlaisella mittausmenetelmällä, joka jäljittelee kennosto-olosuhteita. Kehitetty menetelmä sisältää samat kontaktimateriaalit, sähköiset kontaktit, kemialliset reaktiot sekä kromin siirtymismekanismit kuin kennostossa. Lisäksi menetelmä mahdollistaa testin jälkeisen analyysin kromin kulkeutumisesta pinnoitteen läpi samaa näytettä hyödyntäen. Eri pinnoitusmenetelmillä tehtyjä Mn-Co-oksidipinnoitteita arvoitiin pinnoitteen pinta-alanormalisoidun resistanssin (ASR), mikrostruktuurin ja kromihöyrystymisen ehkäisykyvyn perusteella. Fysikaalisella kaasufaasipinnoituksella (PVD) tehdyillä pinnoitteilla oli alhaisin ASR ja nämä ehkäisivät kromihöyrystymistä. Pinnoitteet sopisivat sellaisenaan SOFC kennostoihin. Parhaiten toimivat pinnoitteet todettiin olevan tiheitä ja hyvin kiinnittyneitä substraattiin. Työssä kehitettiin ja testattiin hybriditiivisteitä, jotka koostuvat kokoonpuristuvasta ytimestä jonka pinnoilla on lasikerros. Tiivistemateriaalin vuototaso oli alhaisemmilla puristuspaineilla alempi kuin pinnoittamattomien kokoonpuristuvien tiivisteiden vuototaso. Hybriditiivisteissä vuototason todettiin olevan pääsääntöisesti kaasukompositiosta riippuva ylipaineen sijaan ja vuodon olevan diffuusiivista. Hybriditiivisteen ja kennostomateriaalien välistä vuorovaikutusta tutkittiin in situ kennostokokeella. Merkittäviä vuorovaikutuksia ei havaittu ja tiiviste todettiin sopivan SOFC käyttöön. Flexitallic Ltd on kaupallistanut tulokset