Zeynep Ilhan

Improving Plasma-Sprayed Yttria-Stabilized Zirconia Coatings for Solid Oxide Fuel Cell Electrolytes

Using a D-optimal design of experiments, the influences of feedstock powder and plasma gases on deposition efficiency, gas tightness, and the electrochemical behavior of vacuum plasma-sprayed yttria-stabilized zirconia for solid oxide fuel cell electrolytes were examined. In-flight particle temperature and velocity, measured by online particle diagnostics, were correlated with plasma and deposit properties. Electrochemical testing of cells was performed to determine the influence of gas tightness and microstructure of electrolyte deposit on cell behavior.

Development of porous anode layers for the solid oxide fuel cell by plasma spraying

This article focuses on the development of the anode layer for solid oxide fuel cells by plasma spraying. The composite (cermet) anode, developed by thermal spraying, consisted of nickel and yttria-stabilized zirconia (YSZ). The effect of different plasma-spraying technologies on the microstructure characteristics and the electrochemical behavior of the anode layer were investigated. Coatings were fabricated by spraying nickel-coated graphite or nickel oxide with YSZ using a Triplex II plasma torch under atmospheric conditions as well as a standard F4 torch under atmospheric or soft-vacuum conditions. The investigations were directed to have an open microporous structure, higher electrical conductivity, and catalytic activity of anode deposits. Porosity was investigated by measuring the gas permeability. Scanning electron microscopy and x-ray diffraction technologies were applied to examine the morphology, microstructure, and composition of the layers. Electrical conductivity measurements were carried out to determine the ohmic losses within the anode layer. The most promising layers were analyzed by measuring the electrochemical behavior to obtain information about catalytic activity and performance.

IDEAL-Cell, Innovative Dual mEmbrAne fueL-Cell: Fabrication and Electrochemical Testing of First Prototypes

The IDEAL-Cell concept is based on the junction between a PCFC anode/electrolyte section and a SOFC cathode/electrolyte section, through a mixed proton and oxide ion conducting porous ceramic membrane, operating in the temperature range 600-700°C. Recombination of ions takes place within the junction, or central membrane (CM), and water vapor is evacuated through open porosity. The first results on the fabrication of multilayered samples reproducing the IDEAL-Cell structure are reported here, together with electrochemical tests carried out on selected samples in order to evaluate the performances of the chosen materials and to demonstrate the feasibility of this innovative concept of fuel cell.

Improving Stochiometery and Processing of LSCF Oxygen Electrode for SOFC

New stochiometries of La1-xSrxCo0.2Fe0.8O3-a (LSCF) for the oxygen electrode of SOFC were developed. The functional layers were manufactured by atmospheric plasma spraying (APS) using TriplexPro gun. Processing of LSCF was optimized for high gas permeability and low decomposition of the powder with focus on high production rates. Studies on microstructure using optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction (XRD) were linked to plasma spray parameters. As a critical factor for decomposition the dwell time of the particles inside the plasma was identified. Functional layers had an improved porosity of about 20 vol%. At 800°C, power densities of above 640 mW/cm² at 0.7 V were recorded with H2/air

Nanostructured Composite Cathodes by Suspension Plasma Spraying for SOFC Applications

In the metal supported SOFCs (MS-SOFCs), conventional sintering route for cathode layer appears problematic due to excessive oxidation of metal support in air at sintering temperatures and degradation of perovskites during sintering in low oxygen partial pressures. The novel process of suspension plasma spraying (SPS), capable of producing a wide variety of coating structures and compositions without any post-deposition sintering, is developed and evaluated in detail for the fabrication of cathode layers for MS-SOFCs. Composite cathodes of LSCF and CGO were developed and the influence of different cathode microstructures on fuel cell performance was examined. Four exemplary cathode coatings have been created, ranging from partially dense with small pores to highly porous layers preserving submicronic agglomerated structures. These cathode coatings have been tested on equal half-cells made of the same anode and electrolyte. The best performing microstructure had a power density of 798 mW/cm2 at 800°C. Microstructural differences could be attributed to different behavior and performance of the coatings.

Towards Understanding the Dual Membrane Fuel Cell (IDEAL-Cell) Using a Metallic Central Membrane

This work presents results of a measurement setup which was constructed for understanding the performance contributions of the individual compartments and reactions taking place in the patented concept of IDEAL-Cell (described in detail in(1)). By inserting a third measurement point at the central membrane of an ideal cell it was possible to measure the cell in three different modes corresponding to hydrogen, oxygen compartment and the full cell. Recorded maximum power densities of (~4, ~7, 11, 16) mW/cm² at (600, 650, 700, 750) °C in H2-O2 atmosphere respectively were observed which were similar to the values of proof of concept ideal cell samples tested so far. Moreover in this setup it was possible to record higher maximum power densities for the hydrogen (proton conducting) compartment which was (~14, 22, 33*, ~38*) mW/cm² at (600, 650, 700, 750) °C.