Joining 3YSZ Electrolyte to AISI 441 Interconnect Using the Ag Particle Interlayer: Enhanced Mechanical and Aging Properties

Round 1

Reviewer 1 Report

The submitted manuscript “Joining YSZ Electrolyte to AISI 441 Interconnect Using the Ag Particle Interlayer: Enhanced Mechanical and Aging Properties” presents experimental results (SEM and TEM analyses and shear strength determination) on the joining between yttria stabilized zirconia and an interconnect (AISI441) via a silver particle interlayer, at different sintering temperatures. The significance of the results is considered relatively high. A minor revision is recommended based on the following questions and comments, as to improve the quality of the manuscript.

1. Would joining SOFC/SOEC electrode materials to the interconnect be possible by this method? Would there be some advantages in doing so, for the development of SOFC/SOEC technology? Would it be useful to include some comments on that in the manuscript? (as for future studies/developments).
2. Why was 3YSZ, instead of 8YSZ, chosen to work with? This information could be included. Could YSZ be replaced in the title with 3YSZ?
3. Do you consider that the Ag interlayer thickness has been optimized, not only for having good mechanical properties but for adequate electrical properties?
4. Could this preparation method be used with a field assisted sintering technology? Maybe if you consider mentioning it (and the potential advantages), a broader range of readers could be interested in your article.
5. When comparing the use of Ag nanopaste with the Ag particle interlayer, cost is mentioned to be a crucial point. Could you estimate the cost difference and include it?
6. I did not find a mention of figure S1 in the text (I may have missed it). Make sure all figures of the supplementary material are mentioned.
7. Would shear strength at operating temperatures be expected to have a similar trend to the one shown at room temperature?
8. Operation conditions might be different to just exposing materials to a reducing or oxidizing atmosphere. Some comments on that could improve your discussion.
9. Some typographical or wording errors were found and marked in the attached PDF.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Overall the paper is technically well written. The literature review/bibliography is updated and properly cited. Well-discussed results. However, the Abstract needs thorough revision. It is extremely hard for a reader to conceive the abstract. The abstract is the sketch of the whole manuscript. So, rewrite it. 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

I think the authors carried out interesting research on the brazing of the SOFC. I think this paper is qualified publishing in the journal with revision. I like the manner the authors prepared their samples and the TEM photos.

1. The authors should unify the font in their manuscript; some lines in the manuscript are seemingly larger than the others.
2. The authors chose 3YSZ at the ceramic material; is there any reason for choosing this? For the record, most electrolytes are made of 8YSZ because of the higher ionic conductivity, while 3YSZ is notable for its mechanical strength.
3. It seems that press before sintering is of great importance for the joint. The results acquired are based on small samples (5×5 mm). Would that be applicable on standard cells (usually 100×100 mm)? Would the press break the cell?
4. The authors tested the joint's stability at a flow rate of 6L/h (less than 2 sccm). Could the authors estimate the velocity of gas flow at the joint? My concern is that this flow rate might be too low to justify the joint’s stability. The flow in an actual fuel cell stack could “blow” away the silver at 800 °C.
5. Personally, I would recommend the authors delete the entire Sec.3.4. There is insufficient evidence proving that the joint is still strong enough for the fuel cell stack. It’s okay to leave it there. However, it does not add scientific value to the paper. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx