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What is a SOFC..?
Solid Oxide Fuel Cell (SOFC) is an electrochemical conversion device that
produces electricity directly from oxidizing a fuel at a higher
In a SOFC, the electrolyte is a solid ceramic material. The anode and cathode
are made from special inks that coat the electrolyte. Unlike other types of
fuel cells, no precious metals, corrosive acids, or molten materials are required
Application in stationary power, marine power or Aircraft APUs
If a SOFC operates continuously a long period then it has a long operating life,
unless parts of the fuel cell would break down so often due to the higher
How SOFC Operates..?
CH4+ H2O = 3H2 +CO
CH4 + CO2 = 2H2 +2CO
In a typical SOFC,
Efficiency is about 60%
Operating temperature is about 1,000°C.
Output is up to 100 kW
Formulation of slurry for anode
a) Solvent as distilled water
b) Solvent as propanol
Formulation of slurry for electrolyte
Zirconia grinding medium in the form of balls were used
to mill the slurry and disperse agglomerations.
Ball milling machine was used for proper mixing of the
slurry with Zirconia balls
Removing bubbles using a vacuum chamber
a) Air bubbles in slurry foam
b) Removing air bubbles by vacuum chamber
Having bubbles may cause to form defected and non
uniform casted layers
Tape casting steps
1) Tape caster is placed above the film carrier
2) Gap between film carrier and the casting plate is set
to desired value
3) An amount of slurry is poured to the glass plate
4) Pipet edge is kept as close as to the film carrier
in order to minimize the formation of air bubbles
5) Tape caster is pushed slowly and
steadily along the guided width of the glass plate
Tape casting contd..
Tape casted layers
a) Nio-Ysz layer without vacuuming
b) Ysz layers with vacuuming
To check high temperature properties of the tape casted samples
3x3 cm2 samples on the
Colored ceramic plates; NiO
Samples with powder beds
First few test runs, sintering was unsuccessful
Ceramic plates showed sign of reactivity towards NiO-YSZ samples
A thin flat powder bed of YSZ was laid between the sample and the
Carbolite Muffle Furnace (CMF)
Carbolite Muffle Furnance
Sintering programme in the CMF
Removing additives in non-violent way under low temperature conditions, prevents
any formation of cracks, rapid gas expansions, etc.
Results and discussion
Results on tape casting
a) Unsuccessfully sintered Nio-Ysz
b) Sintered YSZ layer at 14000C
Microstructure of NiO-YSZ layer
before sintering observed
through optical microscope
Microstructural observation of
sintered NiO-YSZ through SEM
Microstructural analysis and validation
Microstructural analysis using Atomic Force Microscope (AFM) will help to study
the degree of dispersity, particle size, porosity and the tendency of agglomeration.
Possible to control the mechanical strength and conductivity of anode.
Substrate tests to obtain desired V-I characteristic, thermal and
The samples are hydrogen thermal reduced in the test furnace in a temperature
about 800 °C and voltage is measured against variable current.
Optimizing slurry composition
Performance of different slurry compositions for better thermal stability and
Conductivity as a function of volume of Ni
Foreign additives; Cu, Zn
It is required to modify, test and repeat the slurry samples in an iterative
manner to obtain an optimized composition
Optimum Sintering Temperature (OST) has to be decided based on
grain size, and boundaries
Eg: OST is changed with the volume of % Ni : 1400 0C for 40% Ni
Adjustable tape casting device is a well designed apparatus for low cost
tape casting ,allowing to control the thickness of anode and electrolyte
down to a desired value.