Mechanical Characterization of Solid Oxide Fuel Cells and Sealants

 4-2
. 
(
a)
), resulting in a thin-layer geometry similar as in SOFC stacks. Crofer22APU 
was used as joining partner with surface preparation equivalent to the stack application. The 
sealant materials were dispensed by screen printing to the steel bar surface. Specimens’ 
dimensions were 50 mm × 6 mm × 4 mm, sealant thicknesses after joining were between 200 ± 
15, 250 ± 15 and 350 ± 25 μm. The necessary heat treatment was applied during joining. The as-
sintered state corresponds to a holding time of 10 h at 850°C. Heating and cooling rates were 5 
K/min.
 
Additional thermal treatments (500h at 800°C for H-Ag or 100h and 1000h at 850°C for 
H-F) were carried out after joining to achieve a state representative for long term stack operation. 
The tensile-loaded specimen surfaces were fine-grinded with 4000-grit abrasive papers before 
the mechanical test. 
Figure
4-2
.
(
b)
shows a schematic and some real specimens after fine 
grinding. 
Figure 4-2: (a) In-house joining jig, (b) schematic and actual head-to-head specimens 
after fine grinding. 

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Experimental 
59 
(3) Torsion test specimens 
Joined plate specimens were designed for the torsion test. Similar as in the case of the head-to-
head specimen, two steel plates (Crofer22APU) were joined by screen printed sealants. 4 kg 
(~40N) load was applied during joining at 850°C for 10 h. The annealed state sealant was 
prepared with further heating treatment (additional 90 h at 850°C). The dimension of the 
specimen was ~30 x 30 x 5.5 mm
3
and the diameter of the circular joining region 25 mm. The 
thickness of sealant layer was ~ 250 mm, corresponding to the typical thickness used in a SOFC 
stack.  
Figure