Effect of Different Types of Pores on Thermal Conductivity of YSZ Thermal Barrier Coatings

Round  1

Reviewer 1 Report

The paper is very interesting but in my opinion, before publishing it needs some additional information.

1. line 47: The authors have written "to investigate the effect of pores on the thermal conductivity, by setting specific parameters as input" please add some more information about it.

2. table 1 the description in the table should be improved. What is the unit of current? A reader could understand that M1, M2 written in the table are the kind of spray parameters. The same notice could be written about the table 2 and 3.

3. line 94 there is written: "The specific heat (Cp) of coatings was determined according to the ASTM E1269-05 standard" please write more about it.

4. Figure 2 the description of ox axis is written with capital letters, but there is no need to do it.

5. table 6 the data written in the table are difficult to read with understanding. Xi is the temperature, so the standardization coefficient Pj is written for small-horizontal pores (%) for X1 temperature, and the standardization coefficient Pj for the next pores are given for different temperature?

6. the formula 6: the last sign >0 is written alone in the line

Author Response

Thanks for your comments which is of great help to my paper, I have wirtten my responses in the PDF.

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a very nicely written manuscript that is clear, concise and scientifically sound. The authors did a particularly good job in the introduction section to give a nice background so that the results and conclusions can be easily understood and put in context by readers both in and out of the field. With minor changes, I suggest that this manuscript be accepted for publication in Coatings.

Some minor language corrections need to be made:

1. Line 28 – Change to “partially stabilized BY zirconium”

2. Line 34 – Change to “structure THAT contains pores”

3. Line 148 – Change to “Ratios of THE 6 types”

4. Line 166-167 – Change to “The magnitude of THE standardization”

5. Line 97 – It says that the density was determined using the Archimedes’ principle. A bit more explanation here for people who are unfamiliar with the technique would be appreciated. If I understand correctly, a sample with known volume was placed into a liquid and the buoyant force was measured to calculate the mass allowing you to calculate the density? If so, I would recommend explaining how the volume was measured.

6. Lines 197-200 says “Coating regions with perfect contact are separated by horizontal pores, which of no contact arising from gas entrapped beneath spreading liquid droplets during coating formation. The heat flux restricted to conduction through the regions of true contact.”. I do not quite understand what is contacting what here. The term “true contact” is also not defined. The authors should consider rewording or adding a sentence or two to explain in more detail.  

7. Lines 202-203 say “Therefore, several studies have explored the effect of inter-lamellar pores.” This needs references.

8. The conclusion does a great job of summarizing the findings of the paper. I would suggest to the authors that they consider adding a sentence or two in this section about how the results impact the field or how the results can be used by others to improve these coatings.

Author Response

Thanks for your comments which is of great help to my paper, I have wirtten my responses in the PDF.

Author Response File: Author Response.pdf

Reviewer 3 Report

This is the work that describes effect of YSZ coating pores aspect ratio, orientation and area on thermal conductivity. 

Article is interesting and readable however I have got some comments:

1. Please explain in the abstract how the coatings were scanned? What do you mean by that?  - probably using SEM. So on, add information that pores were observed on the coatings' cross-section.

2. In Keywords add "APS"

3. Please explain me why the substrate was grinded away? (L83-84)

4. I do not understand why you refinement the structure by “Grinding part of the free-standing coatings and then sfiting over sieves” Please explain me why you used that procedure?

5. L119: Please explain in the material and methods section, how you measured “all about 5%”? The result derives form XRD analysis?

6. I think that section 3.2.1 heading should be “ Overall porosity and thermal conductivity”

7. Please move fig.2 after table 3 – according to the text given in L126-129.

8. It is not easy to read tables 4 and 5. Please improve the headings of the tables. What does the numbers 1-6 given in tab. 4 mean? – maybe “name or type of pores”? In tab.5 – what the numbers form 1 (%) to 6(%) mean – please add heading.

9. Can you comment/explain why they do not have obvious impact? L158-160

10. Please present the results of “multiple linear regression” in plot-form (if it is possible).

11. In L188 add word “thermal” resistance. 

12. fig 5: please provide the legend for arrows presented in fig 5. Also distinguish and mark in the fig. 5 the different types of pores discussed in your manuscript.

Author Response

Thanks for your comments which is of great help to my paper, I have wirtten my responses in the PDF.

Author Response File: Author Response.pdf

Round  2

Reviewer 1 Report

In my opinion, the article is ready to be published

Reviewer 3 Report

Thank you for your response. I accept your explanations and improvements.