Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study investigates the effect of Ni in short-looped remanufactured NdFeB magnets.

Other contaminants like carbon, zinc and oxygen are reviewed from other publications. However, the authors have been flippant in these correlations and not fully appreciated the influence of other factors (e.g. rare earth content, manufacturing method etc.) 

Fig.2 has a missing vertical axis label.

Fig. 2 does not take into account the total rare earth (TRE) content of each group. TRE/O ratio is critical. For example, Sasaki 2013 14.6 at%(Nd,Pr), Minowa1991 16 at% (Nd,Dy) and Hartwig 2014 14.35 at% (Nd,Dy).

There is no need to duplicate compositional terms like "around 1 – 3 wt.% or 10,000 – 30,000 ppm of Cu" (throughout manuscript).

Copper is a beneficial element to sintered magnets. Some 0.2 wt.% is alloyed in for grain boundary modification. Section 2.3 is irrelevant.

Table 2 needs a Total Rare Earth row.

The statement about 'density ranged between 91% and 99% density, with no clear tendency to decrease or increase' is strange. Density will have a huge influence over remanence. Density is affected by many factors like oxygen and manufacturing parameters. More detail is required to support this statement.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The paper reports the Effects of contamination on the recyclability of NdFeB perma-

nent magnets via short loop processing: Review of common contaminants and study on Ni coating residues. In this article, the known effects of common contaminants (O, C, Ni, Cu, Zn) introduced due to product design choices, namely from coating material and adhesive residue, or a lack of corrosion protection, are reviewed. And the manuscript is up to the academic standard of recycling. However, the manuscript can be considered for publication in recycling.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have put in place a phenomenal descriptive introduction on the effect of contamination on the coercivity of Nd-Fe-B alloys. While the manuscript focuses on the effect of Ni as a contaminant on the magnetic properties, the extensive efforts of the authors to summarize the role of other contaminants such as O, C, Cu and Zn is sure to garner a lot of interest among readers (especially among new researchers). The authors are suggested a few minor modifications to improve the clarity in the manuscript.

 

1. Lines 41-42: The manuscript focuses on effects of Ni contamination, and the authors are thus suggested to reframe their question.
2. Lines 236-237: It may be unclear to readers whether the samples were digested in aqua regia or 5% nitric acid. The authors are suggested to reframe the sentence.
3. The authors are suggested to provide the quantity of samples used for the estimation of organic constituents in the samples.
4. In Table 1, the authors are suggested to provide the standard deviation values.
5. Line 246: Is there any basis based on which the different amounts of nickel powder are chosen? This information may be useful to the readers.
6. The authors are suggested to provide the SE images corresponding to Figures 5 and 6.
7. Can the authors elucidate the reason for high porosity in higher Ni containing samples in the Discussion section?

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The article “Effects of contamination on the recyclability of NdFeB permanent magnets via short loop processing” analyzes the impact of contaminants (O, C, Ni, Cu, Zn) on the recyclability of NdFeB permanent magnets in the HPMS short-loop recycling process. The topic of the paper is current and well defined. It addresses an issue that is becoming increasingly important in the context of the circular economy and the shortage of critical raw materials. It stands out for its original combination of a literature review with the authors' own research on the impact of nickel contamination. My comments to the authors:
1. It would be worthwhile to show a little more data on the reliability of the measurements.
2. The article concerns a single recycling cycle, so it would be good to check what happens after several such cycles.
3. It would also be useful to include a few sentences on how this research could be applied in industrial practice, i.e., whether such recycling is profitable and what the real technical limitations are.
4. Figure 2 is not announced in the text before its presentation.

Author Response

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Author Response File: Author Response.docx