Titanium Carbide Coating for Hafnium Hydride Neutron Control Rods: In Situ X-ray Diffraction Study
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
This paper deals with the phase transformation and hydrogen release at high temperature due to the TiC coating on HfHx samples using in-situ XRD measurement. I recommend that the authors need to do some revisions as below, to enhance usefulness and impact of the research contents.
0 Major comments
1) In figure 1, I can see that the Hf peak around 50° disappears in the region of about 200℃ to 600℃. The author needs to provide further explanation for the disappearance of the Hf peak in this region.
2) In Figures 4 and 9, Ti and Hf oxidize rapidly around 900 °C, showing an increase in the ratio of TiO2 to HfO2. The authors need to further explanation in the discussion what causes the oxides to form, and it would be better to add the vacuum condition at the chamber in the experimental details.
3) The author mentioned in the introduction part that HfHx have a tetragonal phase and a face-centered cubic phase depending on the x ratio. If so, the structural change of HfHx with temperature also affect the hydrogen release, so an explanation is needed.
4) In the introduction, the author mentioned that hafnium-based materials used in the nuclear reactors are tested up to 1400 °C. However, in this study, the author has tested to 900 °C. What is the reason for this? Also, a description of the system that the author is targeting and the operating temperature range should be written.
5) Since the application of HfHx is as a neutron absorber, TiC neutron absorption capacity is also important factor in this study. What is the effect of TiC on neutron absorption capacity?
0 Minor comments
1) It seems to be difficult to consider the thickness of TiC coating as a deposition condition in table 1. This needs to be corrected by the author, and it would be better to have an image to confirm that the coating thickness is 1.2 μm to help the reader’s understand.
2) In figure 4, 5, 9, 10, the black line (temperature line) should be labeled uniformly.
Comments on the Quality of English Language
Author Response
Dear Reviewer 1,
many thanks for your remarks. We improved our manuscript. All changes are highlighted by green in the re-submitted article.
Note 1) In figure 1, I can see that the Hf peak around 50° disappears in the region of about 200℃ to 600℃. The author needs to provide further explanation for the disappearance of the Hf peak in this region.
Reply 1) Thank you for your comment. It is In fact, the Hf peak (50°) is in the range from 200 to 600 ℃. Initially, the metallic hafnium has a low content in the samples and its intensity is extremely low (near background signal). When heating the samples, there is a slight increase in the intensities of other reflections. As a result of such low-intensity reflections become less noticeable in the overall diffraction pattern. So, we have added some description of the data in part 3.1 to avoid misinterpretation of the results.
Note 2) In Figures 4 and 9, Ti and Hf oxidize rapidly around 900 °C, showing an increase in the ratio of TiO2 to HfO2. The authors need to further explanation in the discussion what causes the oxides to form, and it would be better to add the vacuum condition at the chamber in the experimental details.
Reply 2) Thank you for your comment. We added the vacuum conditions in part 2.2., also we improved the Discussion part.
Note 3) The author mentioned in the introduction part that HfHx have a tetragonal phase and a face-centered cubic phase depending on the x ratio. If so, the structural change of HfHx with temperature also affect the hydrogen release, so an explanation is needed.
Reply 3) Thank you for your comment. According to XRD data, the x value in the initial HfHx sample was equal to ~1.7, which corresponds to δ hafnium hydride phase with cubic structure. Hydrogen was released from the sample under linear heating. The δ hafnium hydride phase partially decomposed and transformed into the δ′ phase with tetragonal structure. Thus, hydrogen release form the sample under heating is accompanied by the δ→ δ′ phase transition (transformation) caused by partial decomposition of the δ phase. It is well agreed with the Hf-H phase diagram [Dottor M., et al. "Experimental determination of the H–Hf phase diagram using in situ neutron diffraction." Journal of Alloys and Compounds 937 (2023): 168353.]. Similar regularities are observed for the 4 group elements of the transition metals. We have performed such studies for titanium and zirconium hydrides [Syrtanov, Maxim, et al. "Laboratory X-ray diffraction complex for in situ investigations of structural phase evolution of materials under gaseous atmosphere." Metals 10.4 (2020): 447; Syrtanov, Maxim S., et al. "Application of synchrotron radiation for In Situ XRD investigation of zirconium hydrides formation at gas-phase hydrogenation." Physics Procedia 84 (2016): 342-348]. Thus, hydrogen release under the influence of temperature stimulates phase transitions, not vice versa.
Note 4) In the introduction, the author mentioned that hafnium-based materials used in the nuclear reactors are tested up to 1400 °C. However, in this study, the author has tested to 900 °C. What is the reason for this? Also, a description of the system that the author is targeting and the operating temperature range should be written.
Reply 4) Thank you for your comment. The tests up to 1400 °C were performed for the metallic Hf. We clarified it in the article. Also we improved the Introduction part for better understanding of selection of test conditions.
Note 5) Since the application of HfHx is as a neutron absorber, TiC neutron absorption capacity is also important factor in this study. What is the effect of TiC on neutron absorption capacity?
Reply 5) Thank you for your comment. The thermal neutron absorption cross-section of TiC is equal to 5.8 b, so the coating with a thickness of 1 µm can not significantly modify neutron economy. More important that TiC is radiation-resistant material [https://doi:10.1016/0022-3115(88)90135-3; https://doi.org/10.1016/0022-3115(85)90243-0; https://doi.org/10.1016/j.vacuum.2023.112338] that indicates possible application of TiC coating in nuclear industry, e.g., protective coating for neutron control rods. We added some information about of TiC in Introduction part.
Note 6) It seems to be difficult to consider the thickness of TiC coating as a deposition condition in table 1. This needs to be corrected by the author, and it would be better to have an image to confirm that the coating thickness is 1.2 μm to help the reader’s understand.
Reply 6) Thank you for your comment. We added some information of coating deposition in part 2.1 for approving coating thickness and phase composition.
Note 7) In figure 4, 5, 9, 10, the black line (temperature line) should be labeled uniformly.
Reply 7) Thank you for your comment. We corrected the Figs. 4, 5, 9 and 10 for better view (it is Fig. 5, 6 and 10,11 in the revised paper).
Best wishes,
Dmitrii V. Sidelev
PhD., Associate Prof.
Tomsk Polytechnic University
phone: +7-3822-70-17-77 (add. 2518)
mob. phone: +7-983-238-71-79
Reviewer 2 Report
Comments and Suggestions for AuthorsRe.: Coatings, manuscript coatings-2730449-peer-review-v1.pdf
Title: TiC coating for HfHx neutron control rods: in situ XRD study
Authors: Dmitrii V. Sidelev1, Alexey V. Pirozhkov, Denis D. Mischenko and Maxim S. Syrtanov
General Statement
In the paper problems of implementation of TiC protective coatings for a hafnium hydrides that can moderate fast neutrons in nuclear installations has been discussed. The authors performed experimental investigations of the protective effects of TiC 1 micrometer layer at high temperature exposition by comparing hydrogen release for protected and unprotected core material samples. The research used advanced technologies for sample preparation, test performance and advanced methods for analyzing the results. The discussion of the results, in general, thoroughly describes problems with the high-temperature behaviour of the protective layer structures. The paper is well organised and presented, the problem is up to date, I have no reservations about the compatibility of this topic with the journal's profile. The general conditions for publication are met and the material is worth presenting to a wider audience of the scientific community.
However, I have reservations about one important detail of the presented results. For this reason, I believe that it is worth discussing the mentioned problem before publication. Because of that I recommend the work for publication after discussion, i.e. after major revision.
Major Comment
Re.: Fig 9 vs. Information provided in the Sample Preparation section
How it is possible for the TiC coating material to give 55 wt.% share (see Fig. 9) in 1 mm in thickness sample while the layer is just around 1 micrometer thick (comp. e.g. Table 1 data)? I don't think it was a calculation error, but rather an oversight in the description of the presentation of the results or the experiment itself.
Minor Suggestions
Re.: Figs. 4 and 9
It seems that diagrams present simplified discrete data at certain time spans. For this reason, you can notice non-physical bends in the curves that are not visible, for example, in Figure 5. It is obvious that the lines are linear interpolations between the calculation points. For that reason I recommend to provide also data points in order to signalize the problem of the data interpretation.
Re.: Eq. 1
It seems that by a mistake the core term of summation sign argument has been located in the superscript.
Author Response
Dear Reviewer 2,
many thanks for your remarks. We improved our manuscript. All changes are highlighted by green in the re-submitted article.
Note 1) Re.: Fig 9 vs. Information provided in the Sample Preparation section. How it is possible for the TiC coating material to give 55 wt.% share (see Fig. 9) in 1 mm in thickness sample while the layer is just around 1 micrometer thick (comp. e.g. Table 1 data)? I don't think it was a calculation error, but rather an oversight in the description of the presentation of the results or the experiment itself.
Reply 1) Thanks for your note. In the experiment of in situ XRD, the sample was positioned at such conditions that the incident radiation penetrated to a depth of ~2 microns (1-1.2 micron of TiC coating) and up to 1 micron of substrate material).
Note 2) Re.: Figs. 4 and 9. It seems that diagrams present simplified discrete data at certain time spans. For this reason, you can notice non-physical bends in the curves that are not visible, for example, in Figure 5. It is obvious that the lines are linear interpolations between the calculation points. For that reason I recommend to provide also data points in order to signalize the problem of the data interpretation.
Reply 2) Thanks for your note. We modified Fig. 4 and 9 (it is Fig. 5 and Fig. 10 in the revised paper).
Note 3) Re.: Eq. 1. It seems that by a mistake the core term of summation sign argument has been located in the superscript.
Reply 3) Thanks for your note. The equation (1) was corrected.
Best wishes,
Dmitrii V. Sidelev
PhD., Associate Prof.
Tomsk Polytechnic University
phone: +7-3822-70-17-77 (add. 2518)
mob. phone: +7-983-238-71-79
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article describes the role of TiC coating on high-temperature behavior of hafnium 9
hydrides in a vacuum. The content of the paper is reasonable, the results are clearly expressed, and it has the value of publication. However, there are still some problems that need to be modified and improved, as follows:
1. In the introduction, the main problems facing the application of HfHx in nuclear reactors can be clearly pointed out, as well as the Scientifc gaps that have not been solved by current research.
2. In the experimental part, HfHx sample preparation and TiC deposition parameter optimization should be supplemented to improve the experimental repeatability. In addition, supplementing the vacuum chamber gas composition analysis will make the results more reliable.
3.It is necessary to modify some statements that are not smooth to improve the language fluency. For example, line 69:“The second series of samples was coated by a TiC using a dual magnetron sputtering system (MS) equipped with Ti (99.95%) and C (99.9%) targets. The distance between both targets to samples was equal to 15 cm.”
Line 122:“Additionally to it, concentration of gases in the vacuum chamber was fixed using the quadrupole mass spectrometer during the high-temperature tests (at Tmax of 700 and 900 ℃).”
4.There are few references in the discussion section, which is suggested to be added.
5.Some parameters of formula (1) are not given units.
Comments on the Quality of English LanguageIt is necessary to modify some statements that are not smooth to improve the language fluency. For example, line 69:“The second series of samples was coated by a TiC using a dual magnetron sputtering system (MS) equipped with Ti (99.95%) and C (99.9%) targets. The distance between both targets to samples was equal to 15 cm.”
Line 122:“Additionally to it, concentration of gases in the vacuum chamber was fixed using the quadrupole mass spectrometer during the high-temperature tests (at Tmax of 700 and 900 ℃).”
Author Response
Dear Reviewer 3,
many thanks for your remarks. We improved our manuscript. All changes are highlighted by green in the re-submitted article.
Note 1) In the introduction, the main problems facing the application of HfHx in nuclear reactors can be clearly pointed out, as well as the Scientifc gaps that have not been solved by current research.
Reply 1) Thanks for your suggestion. We modified the introduction.
Note 2) In the experimental part, HfHx sample preparation and TiC deposition parameter optimization should be supplemented to improve the experimental repeatability. In addition, supplementing the vacuum chamber gas composition analysis will make the results more reliable.
Reply 2) Thanks for your suggestion. We added information about selection of deposition parameters of TiC coating in part 2.1.
Note 3) It is necessary to modify some statements that are not smooth to improve the language fluency. For example, line 69:“The second series of samples was coated by a TiC using a dual magnetron sputtering system (MS) equipped with Ti (99.95%) and C (99.9%) targets. The distance between both targets to samples was equal to 15 cm.”
Line 122:“Additionally to it, concentration of gases in the vacuum chamber was fixed using the quadrupole mass spectrometer during the high-temperature tests (at Tmax of 700 and 900 ℃).”
Reply 3) Thanks for your note. We corrected the text.
Note 4) There are few references in the discussion section, which is suggested to be added.
Reply 4) Thanks for your note. We improved discussion.
Note 5) Some parameters of formula (1) are not given units.
Reply 5) Thanks for your note. We added units for parameters of formula (1).
Best wishes,
Dmitrii V. Sidelev
PhD., Associate Prof.
Tomsk Polytechnic University
phone: +7-3822-70-17-77 (add. 2518)
mob. phone: +7-983-238-71-79
Reviewer 4 Report
Comments and Suggestions for AuthorsThe article is interesting. But it can not be published in current version. There are some questions required to be answered:
（1）The significance of this work should be described in the abstract.
（2） In the “Introduction”, the reasons for choosing TiC as a coating material need to be added for better understanding.
（3） The format of Table 1 needs to be adjusted. How to select the "Deposition parameters of TiC coating"? It should be described in article.
（4）The particle size of TiC powder needs to be shown in the article.
（5）It is suggested to add marks to the black curve in Figure 4
（6）Conclusions, it is recommended to express in paragraphs, such as (1), (2), (3)………
Author Response
Dear Reviewer 4,
many thanks for your remarks. We improved our manuscript. All changes are highlighted by green in the re-submitted article.
Note 1) The significance of this work should be described in the abstract.
Reply 1) Thanks for your suggestion. We modified the abstract.
Note 2) In the “Introduction”, the reasons for choosing TiC as a coating material need to be added for better understanding.
Reply 2) Thanks for your suggestion. We modified the introduction.
Note 3) The format of Table 1 needs to be adjusted. How to select the "Deposition parameters of TiC coating"? It should be described in article.
Reply 3) Thanks for your suggestion. We added information about selection of deposition parameters of TiC coating in part 2.1.
Note 4) The particle size of TiC powder needs to be shown in the article.
Reply 4) We used magnetron sputtering of solid Ti and C targets with a diameter of 90 mm and thickness of 8 mm. No any powder was used in this study.
Note 5) It is suggested to add marks to the black curve in Figure 4
Reply 5) Thanks for your suggestion. We corrected the Figure 4 (it is Fig. 5 in the revised paper).
Note 6) Conclusions, it is recommended to express in paragraphs, such as (1), (2), (3)………
Reply 6) Thanks for your suggestion. We modified the conclusions.
Best wishes,
Dmitrii V. Sidelev
PhD., Associate Prof.
Tomsk Polytechnic University
phone: +7-3822-70-17-77 (add. 2518)
mob. phone: +7-983-238-71-79
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsI have checked all of author's response about major revision, and many thanks for your faithful revision.
Reviewer 2 Report
Comments and Suggestions for AuthorsRe.: Coatings, manuscript coatings-2730449-peer-review-v2.pdf
Title: TiC coating for HfHx neutron control rods: in situ XRD study
Authors: Dmitrii V. Sidelev, Alexey V. Pirozhkov, Denis D. Mishenko and Maxim S. Syrtanov
General Statement
All my comments were taken into account. I accept the answers and these are the ones I expected. However, I have a request to change the caption of Figure 10. In my opinion, the caption of Figure 10 is not correct and it should be noted in the caption that the figure does not present the test results of the entire sample, but only of the coverage.
I also have trouble assessing linguistic correctness. It seems to me that after the changes were introduced, some minor stylistic errors appeared and that the text would be worth reviewing linguistically once again.
I accept the manuscript for publication after making minor corrections.
Comments on the Quality of English Language
I have no additional comments extept of this one provided within the review.
