Phase Transition of Nb3Sn during the Heat Treatment of Precursors after Mechanical Alloying
Round 1
Reviewer 1 Report
The manuscript describes a thermal process developed to obtain superconducting Nb3Sn, and the authors say:
“We report a simple and time-saving synthesis technique of Nb3Sn, which proceeds through the mechanical alloying method, followed by a short-term heat treatment. Through mechanical alloying, Nb, Sn, and Cu powders were mixed and alloyed, and the precursors were synthesized by high-energy ball milling of the as-blended powders. Then, the precursors were heat treated to form Nb3Sn.”
A similar paper however has already been published by the same authors, in Journal of Low Temperature Physics Volume 205, pages100–111 (2021), with the same message: “Herein, we report a simple and time-saving synthesis of Nb3Sn through the mechanical alloying method, followed by a short-time heat treatment cycle in which Nb, Sn, and Cu powders acted as raw materials.”. Moreover, the same results are presented with the only implementation of some XRD patterns at different temperatures, that however do not seem to add nothing substantial to the previous results. For these reasons, it is not clear to me what is the novelty of the present manuscript. Neither the Introduction nor the Results and Discussion Section put the reader in condition of clearly understanding the novelty of the presented results. A scheme or a table that could help the reader to follow the thermal procedure is also missing.
The second part of the manuscript on the magnetic measurements has to be rewritten in a correct way.
Figure 12 shows MT after 24h and 50h of heating treatment. Why? What is, if any, the difference? Or, if no difference, what the authors wish to prove? How the value of Tc has been evaluated? For the upper critical magnetic field Bc2 (improperly called “second” magnetic field) is not given any numeric evaluation, although its expression is given from the Werthamer-Helfand-Hohenberg theory.
In Figure 13 the vertical scale has to start from zero, the horizontal scale would be better if given in Tesla. The authors have to explain the difference between low field behavior and high field behavior, as well as explain the critical current density Jc (improperly called “magnetic” Jc) value of 30 000 A/cm2 at which field has been evaluated and why.
The values of the critical current density Jc are not compared to the values already obtained on bulk N3Sn.
In conclusion, the authors must explicitly declare what is the new message of this manuscript.
The References are in some cases missing (for instance, in the first sentence, the Matthias paper must be referenced) and not completely appropriated for contextualizing the argument in the framework of the existing huge literature on Nb3Sn. The authors may read the following papers and References therein:
A review of the properties of Nb3Sn and their variation with A15 composition, morphology and strain state, A Godeke 2006 Supercond. Sci. Technol. 19 R68
A review and prospects for Nb3Sn superconductor development, Xingchen Xu 2017 Supercond. Sci. Technol. 30 093001
The format of the References is random and does not include in many cases all the informations on the papers (Journal, Volume, pages, year).
The English is very poor.
Author Response
"Please see the attachment."
Author Response File: 
Author Response.docx
Reviewer 2 Report
Line 70 - please add information about the particle size
Line 71 - please provide the exact ratio or mass of each powder in grams
Line 72 - please add the conditions for high energy ball milling
Line 92 - please explain how it is possible to detect Sn with energy dispersive X- RAY spectroscopy and not X- RAY diffraction?
Line 94 - SEM images of the starting powders should also be included in the manuscript
Figure 2 is not readable
Figure 4 - in the XRD pattern Sn is visible and detected... The question is why the authors wrote the following sentence "The depth of X-ray diffraction (XRD) was not enough to penetrate the Nb shell"
Line 110 - "The selceted area electron diffraction pattern shown in the inset of Fig. 3a suggested that the products showed poor crystallinity" - In fact, SAED shows a "halo ring"; however, together with rings typical of nanocrystalline matrials... this means that the diffraction originates from the area where several crystals exist
Author Response
"Please see the attachment."
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
11) In my previous report I observed that a similar paper was already published by the authors, and that the novelty of the present manuscript was not declared. The situation has not changed, the authors do not mention their previous work and do not explain, neither in the manuscript nor in the cover letter, what new there is in the submitted work.
22) In the second part I asked to review several things, for instance how Tc has been evaluated, an estimation of Bc2, the scales in Fig. 13 (now Fig 14) to be changed. None of these requests were met.
33) The English has not been checked, the manuscript still contains many mistakes and imperfections.
For all these reasons, in my opinion the paper cannot be published.
Author Response
"Please see the attachment."
Author Response File: Author Response.docx
Reviewer 2 Report
Accept as it is.
Author Response
Thank you. We have checked the English carefully and the mistakes have been modified in the revised manuscript.
Round 3
Reviewer 1 Report
The paper has been improved enough and can now be published.
