Holistic Characterization of MgO-Al₂O₃, MgO-CaZrO₃, and Y₂O₃-ZrO₂ Ceramic Composites for Aerospace Propulsion Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The analysis of the microstructure performance relationship of three different ceramic systems is insufficient, and the manuscript only describes the test results. Most of the time, authors are telling readers about the consistency between experimental results and literature results. The biggest feature of this article is that it conducted more systematic experimental tests and collected more experimental results, but this led to the loss of scientific significance of the article. In addition, there are also many display errors in the citation of references, such as,

line500，Error! Reference source not found. 

line519，Error! Reference source not found.

line558，Error! Reference source not found.

line537，Error! Reference source not found.

Author Response

Dear Reviewer,

Thank you for your comments and concerns pointed out. 

Please find attached the rebuttal related to your review.

Sincerely,

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this work, the authors prepared MgO-Al2O3, MgO-CaZrO3, Y2O3- ZrO2 ceramic composites and pressed using uniaxial pressing and heat treated through conventional sintering process and studied their density, thermal and mechanical properties. The experimental section should be explained clearly. In addition, there are some minor comments which need to be addressed by authors before possible publications in MDPI ceramics journal.

1.      Please check line 211 in the results and discussion section. The references are not placed properly in this manuscript. Please check.

2.      Fig. 1b – please highlight the gray and white regions and mention what are those materials.

3.      What are the ratios of materials added to prepare MA, MCZ and YSZ. I mean the contents of ceramics in MA and all the cases. It is not available in the materials and methods section.

4.      I do not understand why the author wants to mix c-YSZ, t-YSZ and m-YSZ and study their properties. How to compensate thermal expansion mismatch of monoclinic phase during cooling phase?

5.      How the author achieved more than 95% density through conventional sintering process without applying any load during sintering process. Also, the size of particles used for sintering also high. Please recheck the density calculation.

6.      CTE calculation can be affected by porosity present in the system. How to compare CTE of three materials with different density.

7.      Conclusion should be written briefly.

8.      Why the authors stopped thermal diffusivity calculation at 700°C. is it due to laser flash instrument limitations? If this material is proposed for high temperature applications, this data would be incomplete. Similarly, CTE calculation also stopped at 950°C.

Author Response

Dear Reviewer,

Thank you for your comments and concerns pointed out. 

Please find attached the rebuttal related to your review.

Sincerely,

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1.      Introduction is too long , authors should decrease it and also they should clearly mention the novelty and motivation of the research, measured properties for these 3 ceramic are available in literature and market for industrial application

2.      Why did authors select these 3 ceramics?

3.      Authors should add higher magnification for MA and YSZ in figure 1

4.      Please add SEM image of hardness indentation for all the samples

5.      Please add compressive strength and fracture toughness of samples

6.      It would be nice to study the fracture surface of samples after flexural trough the SEM

Author Response

Dear Reviewer,

Thank you for your comments and concerns pointed out. 

Please find attached the rebuttal related to your review.

Sincerely,

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for submitting your revised version.

Reviewer 3 Report

Comments and Suggestions for Authors

rejected