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Author:Patakangas, Janne
Title:Material synthesis, cell preparation and characterization of low temperature solid oxide fuel cells
Matalan lämpötilan kiinteäoksidipolttokennojen materiaalien synteesi, kennojen valmistus ja karakterisointi
Publication type:Master's thesis
Publication year:2011
Pages:65 + [10]      Language:   eng
Department/School:Teknillisen fysiikan laitos
Main subject:Ydin- ja energiatekniikka   (Tfy-56)
Supervisor:Lund, Peter
Instructor:Lund, Peter
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  118   | Archive
Keywords:band gap
EIS
I-V
LTSOFC
SDC
SEM
TEM
XRD
EIS
energia-aukko
IV
LTSOFC
SDC
SEM
TEM
XRD
Abstract (eng): The objective of this work was material synthesis, cell preparation and characterization of low temperature solid oxide fuel cells (LTSOFC).
The thesis is part of a TEKES financed project that aims at developing inexpensive LTSOFCs for energy production in buildings.

A mixture of carbonates and samaria doped ceria (SDC) nanoparticles was studied as an LTSOFC electrolyte, while a mixture of the electrolyte and metal nanoparticles was studied as a possible electrode.
The materials were prepared through different material compositions and synthesis methods, and were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and band gap measurements.

LTSOFC unit cells were pressed from the powder materials using a self-made equipment with a pressing temperature up to 600 °C.
The prepared unit cells were characterized by I-V and impedance measurements with a self-made equipment and by transmission electron microscopy (SEM).

The XRD and TEM measurements indicate that the electrolyte syntheses produced SDC particles with a diameter of several tens of nanometers and that samaria was doped into the ceria structure.
Carbonates formed an amorphous structure but did not produce the desired carbonate shell around the SDC particles.
The band gap measurements indicate that the SDC based materials had the same indirect band gap as ceria.

The I-V and impedance measurements reveal that the carbonate phase increased fuel cell performance and that the electrolyte syntheses and unit cell preparation methods affect greatly the conductivity of the electrolyte.
On the contrary, differences in the electrode syntheses did not have a large effect on the fuel cell performance.
The SEM cross section images reveal also that sintered cells had a dense electrolyte while the electrolyte in unsintered cells was porous.
Cells that had been pressed at room temperature and sintered in an oven at 600 °C displayed the highest efficiency, and the maximum power density achieved with these materials was 450mW/cm2 at 510 °C.
Abstract (fin): Työn tarkoituksena oli matalan lämpötilan kiinteäoksidipolttokennojen (LTSOFC) materiaalien synteesi, kennojen valmistus ja karakterisointi.
TEKES rahoitteisen projektin päämääränä on tuottaa halpoja LTSOFC kennoja rakennuksien energiatuotantoa varten.

Karbonaatin sekä nanopartikkelisen, samariumoksidilla seostetun ceriumoksidin (SDC) seosta tutkittiin mahdollisena LTSOFC elektrolyyttinä.
Elektrolyytin sekä nanopartikkelisen metallin yhdistelmää tutkittiin mahdollisena elektrodina.
Erilaisten materiaalikoostumusten ja valmistustapojen vaikutusta materiaalien ominaisuuksiin tutkittiin röntgensädediffraktio- (XRD), transmissioelektronimikroskooppi- (TEM) ja energia-aukkomittauksilla.
LTSOFC kennojen valmistamisessa käytettiin itsetehtyä laitteistoa, jonka prässäyslämpötila ulottui aina 600 °C asteeseen asti.
Toista itse tehtyä laitteistoa käytettiin kennojen I-V ja impedanssitutkimuksissa, jonka lisäksi käytetyistä kennoista otettiin pyyhkäisyelektronimikroskooppilla (SEM) poikkileikkauskuvia.

XRD ja TEM mittaukset osoittavat, että valmistettujen elektrolyyttipartikkelien koko oli kymmeniä nanometrejä ja että samarium oli sitoutunut ceriumoksidirakenteeseen.
Karbonaatit myös muodostivat amorfisen rakenteen, mutta karbonaattipäällysteisiä SDC -partikkeleita ei syntynyt.
Lisäksi ceriumoksidin epäsuora energia-aukko vastasi myös SDC -pohjaisille materiaaleille mitattua energia-aukkoa.

I-V ja impedanssimittaukset paljastavat karbonaatin lisäämisen parantaneen LTSOFC:n suorituskykyä sekä elektrolyytin valmistustapojen vaikuttaneen suuresti elektrolyytin johtavuuteen.
Toisaalta erot elektrodien valmistuksessa eivät aiheuttaneet suurta muutosta kennojen suorituskykyyn.
SEM kuvien perusteella elektrolyytti oli tiivis sintratuissa kennoissa, kun taas sintraamattomissa elektrolyytti oli huokoinen.
Paras suorituskyky saatiin huoneenlämmössä prässätyillä, uunissa 600 °C asteessa sintratuilla kennoilla maksimitehotiheyden ollessa 450mW/cm2 510 °C asteessa.
ED:2011-09-23
INSSI record number: 42801
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