Structural Optimization, Fabrication, and Corrosion Behaviors of Biodegradable Mg-Nd-Zn-Zr Alloy Hemostatic Clip
Round 1
Reviewer 1 Report
Notes on the article of Lin Mao, Xin Zheng, Yongji Tian, Yiling Shi, Xiaochen Zhang, Chengli Song “Structural optimization, fabrication, and corrosion behaviors of biodegradable Mg-Nd-Zn-Zr alloy hemostatic clip”
The paper reports results of creation and studying of the hemostatic clip with the transverse tooth from Mg-Nd-Zn-Zr alloy. The authors determined the optimal parameters of hemostatic clip. In addition, the authors conducted a study plastic strains of the Mg alloy clips and other similar features. The authors also conducted a study of the microstructure of the clips of their corrosion behavior. However, a big drawback of the work is the weak level of microstructure research. Despite this, the results of this article have the high importance for research of magnesium alloys in medicine. This report сan be published after revisions that are listed below:
1) Why are deformation parameters (temperature, degree of deformation) not given? This complicates the evaluation of the obtained results.
2) The authors do not give details of the study of the microstructure at all. It is necessary to measure the grain size and the width of the twins. In addition, the authors mention the presence of particles Mg12Nd. How did the authors know that they are in the structure of the alloy? If the extrusion temperature is high, they may not precipitate. If they are in the structure of the alloy, it is necessary to indicate their volume fraction. What is the difference in microstructure at different points of the clip (Fig. 5)?
3) Why do the authors say that the pH values for a closed clip are higher than for an opened one? According to Figure 6b, the values are the same. In addition, the authors state that the corrosion medium was changed every 24 hours. At the moment of changing the medium, the pH value should have dropped sharply. From this point of view, the graph in Figure 6b looks doubtful.
4) The authors state: «We can see that the corrosion rate of the closed Mg alloy clip is about 0.118 mg∙cm-2∙day-1, which is higher than that obtained from the opened clip (0.094 mg∙cm-2∙day-1).» Since the degradation rates are given without taking into account the error, this statement is doubtful.
5) Figure 7. It would be nice to provide a full photo of the clip after testing for corrosion resistance.
6) For all calculated parameters, it is necessary to provide the value of the experimental error.
7) Authors should correct typos:
- P.1, L19/20. It is written: «(0.118 "mg·" 〖"cm" 〗^"-2" 〖"·day" 〗^"-1" ) corroded slightly 19 faster than the opened ones (0.094 "mg·" 〖"cm" 〗^"-2" 〖"·day" 〗^"-1" )». Should be written: «(0.118 mg·cm-2∙day-1) corroded slightly 19 faster than the opened ones (0.094 mg·cm-2∙day-1)».
- P.3, L100. It is written: «finite element analysis of Mg alloy clip». Should be written: «Finite element analysis of Mg alloy clip».
Comments for author File: 
Comments.pdf
Author Response
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Reviewer 2 Report
1. Please explain how to achieve the optimal design. As understood, there is no optimization procedure, but one of them in Table 1 has the relatively low stress through parameter study.
2. Please explain why TS is better than NS and FS.
3. According to Fig 6, there is no big difference in immersion results between closed and opened clips. Why did the closed clips corrode slightly faster than the opened ones?
4. How did you come to the conclusion that no signs of cracking appear on the closed Mg alloy clip, indicating that the Mg alloy performs excellent resistance to stress corrosion cracking in artificial plasma?
Author Response
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Round 2
Reviewer 1 Report
The authors revised the article in detail. It should be accepted in the current version.
Author Response
We thank the reviewer for reviewing the manuscript.
Reviewer 2 Report
1. As far as I understood, there is yet no optimazation procedure for clip design. This is just parameter study, and one of them has a lower stress. That is, one of them is an advanced design.
2. There is no backgroud and proper references for twins of Mg alloy to deteriroate corrosion resistance.
Author Response
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