Hydrogen Generation from Mg Wastes by Cold Rolling and Ball Milling by Hydrolysis Reaction: Elektron 21 (UNS-M12310) in Simulated Seawater
and Jean-Louis Bobet *
Round 1
Reviewer 1 Report
Application of magnesium based waste for hydrogen generation through oxidation by water is a promising topic. The manuscript under consideration reports some interesting experimental data on impact of various mechanical treatments on kinetics and overall hydrogen yield in this process. To be accepted for publication, minor revision can be recommended.
1. Excessive self-citation is observed in the list of references. Expanding the list of cited literature in the introduction and, especially, when discussing the results would be useful.
2. Table 1: accuracies in determining the given parameters should be specified.
3. Lines 106-108, 178: according the available phase diagrams, solubility of Nd and Gd in magnesium is very limited, much lower than 0.65 at%. In the studied concentration ranges, along with Mg solid solution, intermetallic compounds, not pure Nd and Gd, should coexist. Please correct the interpretation of XRD and EDS data.
4. Fig.3: I recommend to emphasize once again in the caption to the picture that salt solution was used instead of pure water. Moreover, comparison of the experimental data with previously reported for pure magnesium. Mg-based mixtures and alloys (including mechanical alloys) regarding their performance in hydrogen generation should be provided.
Author Response
We would like to thank the reviewer for the careful and thorough reading of this manuscript and for the thoughtful comments and constructive suggestions, which help to improve the quality of this manuscript. Please see the attachment for details.
Reviewer 1
Application of magnesium-based waste for hydrogen generation through oxidation by water is a promising topic. The manuscript under consideration reports some interesting experimental data on impact of various mechanical treatments on kinetics and overall hydrogen yield in this process. To be accepted for publication, minor revision can be recommended.
- Excessive self-citation is observed in the list of references. Expanding the list of cited literature in the introduction and, especially, when discussing the results would be useful.
Thank you for the remark, new references have been added to be more pertinent and some of them were deleted in order to reduce the self-citation.
- Table 1: accuracies in determining the given parameters should be specified.
|
EL21 |
EL21-BM |
EL21-CR7 |
EL21-CR15 |
Mg (according to ICSD n° 01-089-4894) |
|
|
a (Å) |
3.212 (3) |
3.218 (4) |
3.214 (4) |
3.213 (4) |
3.209 |
|
c (Å) |
5.203 (5) |
5.216 (7) |
5.208 (7) |
5.197 (7) |
5.210 |
|
(nm) |
36 (2) |
34 (3) |
30 (3) |
28 (3) |
|
|
(nm) |
32 (2) |
30 (3) |
34 (3) |
32 (3) |
|
We agree with the reviewer that the accuracy is an important point that should be added for these measurements. Thanks to this feedback, we were able to calculate and add in the publication the accuracy of the measurement (as shown on the table below).
- Lines 106-108, 178: according the available phase diagrams, solubility of Nd and Gd in magnesium is very limited, much lower than 0.65 at%. In the studied concentration ranges, along with Mg solid solution, intermetallic compounds, not pure Nd and Gd, should coexist. Please correct the interpretation of XRD and EDS data.
Thank you for pointing out this solubility problem. However, the solubility of Gadolinium and Neodymium in magnesium can be higher than 0,65at%: for instance, the solubility limit can be as high as 7.3at% for Mg-Nd and 14.1at% for Gd-Mg as shown on the following phase diagrams (depending on T of course):
That is why we can expect that Gadolinium or Neodymium should be included in the magnesium lattice. Nevertheless, as observed by EDS some traces of pure Gadolinium and Neodymium are still observed, these traces are due to the industrial synthesis method.
- I recommend to emphasize once again in the caption to the picture that salt solution was used instead of pure water. Moreover, comparison of the experimental data with previously reported for pure magnesium. Mg-based mixtures and alloys (including mechanical alloys) regarding their performance in hydrogen generation should be provided
As requested by the reviewer, the figure has been modified to be clearer for the reader that these experiments have all been done in salted water:” fig 3: Hydrogen generation kinetics and yield of EL21 after different mechanical treatment in salted water.”
As done from the point 1, new citations were added in order to provide a better comparison between those alloys and the EL21 alloy.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The article "Hydrogen generation from Mg wastes by cold rolling and Ball Milling by hydrolysis reaction: Elektron 21 (UNS-M12310) in simulated seawater" is devoted to studying the influence of mechanical treatment parameters on hydrogen generation kinetics and yield of EL21 alloy. The obtained results are significant from a practical point of view and can be used to solve the problem of storage and distribution of hydrogen. Separately, it should be emphasised that the research object is waste EL21 alloy in the form of chips obtained from machining. So, the proposed approach is a possible way to give them a second life as a hydrogen generator. Furthermore, the results of experimental research are clearly described and explained. Finally, the conclusions are neatly formulated. Therefore, I believe this article can be published in its present form.
Author Response
We would like to thank the reviewer for the careful and thorough reading of this manuscript and for the thoughtful comments and constructive suggestions, which help to improve the quality of this manuscript.
Reviewer 3 Report
The authors in this manuscript reported their studies on the hydrolysis performances of waste Mg metals modified by rolling and milling. It is an interesting topic and can be accepted for publication in Metals after addressing the following issues.
1.Abstract section, is the content of Mg, Nd, and Gd by weight or by molar?
2.Introduction section, the authors stated that “Currently, the most used method to produce hydrogen is catalytic steam reforming from natural gas for almost 95%”. The authors should check the accuracy of 95% since there are other hydrogen production methods.
3.The authors should explain what are “CryoR” and “CR”?
4.Line 178 and 197, I suggest the authors provide the EDS results of the samples to display the white particles corresponds to the rare earth.
Author Response
We would like to thank the reviewer for the careful and thorough reading of this manuscript and for the thoughtful comments and constructive suggestions, which help to improve the quality of this manuscript.
Reviewer 3
The authors in this manuscript reported their studies on the hydrolysis performances of waste Mg metals modified by rolling and milling. It is an interesting topic and can be accepted for publication in Metals after addressing the following issues.
1.Abstract section, is the content of Mg, Nd, and Gd by weight or by molar?
Thank you for noticing this lack of precision from our part, the content of Mg, Nd and Gd are indeed in weight%. This information has been added to be more precise. Line 37-38: “This alloy is composed of Magnesium (96wt%), Neodymium (2.6-3.1wt%) and gadolinium (1-1.7wt%)”.
2.Introduction section, the authors stated that “Currently, the most used method to produce hydrogen is catalytic steam reforming from natural gas for almost 95%”. The authors should check the accuracy of 95% since there are other hydrogen production methods.
Thanks to the reviewer pointing out this problem, the introduction has been modified to add more precision about the type of hydrogen production and its percentage: line 26-28 “Currently, the most used method to produce hydrogen is through the uses of fossil fuels (by different methods: catalytic steam reforming, coal gasification and partial oxidation) for almost 95% [4] or electrolysis for 5% [5].”
3.The authors should explain what are “CryoR” and “CR”?
We appreciate this feedback from the reviewer. These information are explained between the lines 65 to 67 but as you mentioned it is better to re-inform the reader about it in other part of the publication.
This information about CryoR is explained line 67: “For the cryogenic rolling (CryoR), the stainless plates are immerged inside liquid nitrogen for 10 minutes, then the sample is put between the plates and rolled”
The information about CR is also repeat several time in the revised version of the manusript
4.Line 178 and 197, I suggest the authors provide the EDS results of the samples to display the white particles corresponds to the rare earth.
We agree with the reviewer that the EDS results could be provided. However, we did not include these results because it may be complicated to put them in the publication since the Magnesium and Gadolinium peaks are mixed on the EDS results. Then, to not include unclear results, we decide to not include it in the revised version.
(Figures are in the attached file)
Author Response File: Author Response.pdf
