Influence Mechanism of (NH₄)₂SO₄ on the Composition and Structure of Fe-Co Alloys

Round 1

Reviewer 1 Report (New Reviewer)

I suggest  large changes of the paper

i) a lighter text more direct and clear

ii) large improvemend  of  english a text form (lot ot errors, missing spaces...)

iii) an improvemend of figure quality (see comments).  Some figures do not appear coherent to me or I dindn't understand. 

iv) a reduction of the figure numbers could favor a more clear message.

v) more details and car can be put to XRD analysis  (see comments).

Comments for author File: Comments.pdf

Author Response

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Reviewer 2 Report (New Reviewer)

The authors have carried out an important work concerning the co-electrodeposition of an FeCo alloy on a metallic Ti substrate. They studied in particular the role played by the presence of (NH₄)₂SO₄ in solution in this phenomenon of electrodeposition. The article as it is written presents a lot of anomaly in both form and font. It can therefore only be accepted for publication after a major revision. Authors should respond clearly to the remarks below.

1. Cite other works on the catalytic effect of (NH₄)₂SO₄ for the electrodeposition of FeCo alloys (in Introduction).

2. It is necessary to develop in the form of explanatory diagrams the experimental condition part (electrochemical cell, etc.)

3. Indicate why the choice of 0.5mV/s as potential sweep rate

4. Also indicate the reason for choosing the potential -1.2 V/SCE and the pH 2.5.

5. In figures 1a-7a add:

In X axis: Potential E (V/SCE)

In Y axis: cathodic current density |Ic| (mA/cm²)

6. In figures 1b – 7b add: Y axis: cathodic current density |Ic| (mA/cm2)

where |Ic| represents the absolute value of the cathodic current density.

7. In figure 1b, represent a linear variation of |Ic| as a function of C_Fe²⁺ specifying the corresponding correlation coefficient (in accordance with the text).

8. Idem for the variations shown in Figures 2b, 3b, 4b and 5b (two linear variations in the case of Figures 2b, 3b, 4b) and also Figures 10a, 10b and 10c.

9. What happens when we represent in figure 2-b Ln (|Ic|) as a function of 1/T.

10. Idem represent Ln (|Ic| ) as a function of C_Co²⁺/ (C_Co²⁺₊ C_Fe²⁺).

11. The values of the standard potentials of the pairs (Co²⁺/Co) and (Fe²⁺/Fe) cannot alone explain the co-electrodeposition of Co and Fe on the metal surface. You have to use the Nernst equation. Explain further.

12. Equation 1 must be written correctly

13. Give the references of equation 1 and also the comments of figure 8.

14. The morphology and microstructure of the electrodeposited FeCo alloy is not clearly visible by SEM examination. It is therefore necessary to propose other images and to use the SEM/EDS coupling to carry out specific analyzes to detect structural defects of the FeCo alloy.

15. Bibliographic references must be completed and written according to the instructions of the journal coating (for example ref. 5)

Author Response

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Round 2

Reviewer 1 Report (New Reviewer)

I'm not specialist of the field  but to my opinion, this paper even after revision and significant improvement, doesn't deserve publication.
I even noticed  that some requested correction have not been taken into acocunt. Scientific argmentation about XRD is still missing.

Comments for author File: Comments.pdf

Author Response

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Reviewer 2 Report (New Reviewer)

 

Dear Editor

After reading the manuscript reviewed by the authors, I found that my remarks below were not taken into consideration. The manuscript in its current state still requires major revision.

With the best regard

Remarks

- Cite other works on the catalytic effect of (NH4)2SO4 for the electroplating of FeCo alloy.  

 - Indicate why the choice of 0.5mV/s as potential sweep rate.

- Also indicate the reason for choosing the -1.2 V/SCE potential and the 2.5 pH.

- In figures 1a – 7a add:

X-axis: Potential E (V/SCE)

Y-axis: cathodic current density |Ic| (mA/cm²)

- In figures 1b – 7b add:

- Y-axis: cathodic current density |Ic| (mA/cm²) where |Ic| represents the absolute value of the cathodic current density.

- In figure 1b, a linear variation of |Ic| as a function of CFe²⁺ specifying the corresponding correlation coefficient (in agreement with the text).

-idem for the variations shown in Figures 2b, 3b, 4b and 5b (two linear variations in the case of Figures 2b, 3b, 4b) and also Figures 10a, 10b and 10c.

- What happens when we represent in the figure 2-b Log(|Ic|) as a function of 1/T.

- idem for representing Log(|Ic| ) as a function of C_Co²⁺/ (C_Co²⁺+ C_Fe²⁺).

- The values of the standard potentials of the pairs (Co^2+/Co) and (Fe²⁺/Fe) cannot alone explain the co-electrodeposition of Co and Fe on the metallic surface. You have to use the Nernst equation. Explain further.

- Equation 1 must be written correctly

- Give the references of equation 1

- Give the references for the comments of figure 8

Author Response

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Round 3

Reviewer 2 Report (New Reviewer)

The manuscript is markedly improved. 90% of my remarks have been taken into consideration. I therefore give my favorable opinion for publication of this work in the journal Coating.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This manuscript focuses on Fe-Co films synthesised by electrodeposition, in particular on the effect of iron, cobalt, and ammonium sulphate concentrations in the electrolyte on the current density and film characteristics. While I do agree that the topic is interesting and fits the scope of the journal, I have some serious questions regarding the manuscript. In my opinion this manuscript requires an extensive make over. Here are my major concerns and comments to the authors for improvement:

1.     The use of units should be consistent across the manuscript, namely for magnetic induction and coercive force.

2.     The authors do not mention how was compositional analysis performed.

3.     Since titanium promptly forms titanium oxide, how was the surface pre-treated/activated prior to electroplating?

4.     How was the polarisation potential range selected?

5.     The authors state that higher Fe²⁺ concentration (or temperature) increases the deposition rate of Fe but process efficiency should have been measured and considered to conclude that, instead of relying on current density values alone.

6.     The authors observe that small additions of ammonium sulphate reduce current density, whereas higher amounts increase current density. A plausible explanation should be given instead of just describing the results.

7.     Similarly, it is said that higher Co²⁺/(Fe²⁺+Co²⁺) ratios can speed up the co-electrodeposition, but no explanation is given for the underlying reasons.

8.     Why are the potentials positive in Fig.8?

9.     How was the Co concentration in the film measured? How about other elemental species such as oxygen, for instance? No description is made in the Experimental section.

10.  Fig.8a and 8b have the exact same legend.

11.  What is the ion ratio used in i_Co2+/(Fe2++_Co2+)?

12.  The ion ratio axis values in Fig.9a makes no sense considering the concentrations used to prepare the electrolyte.

13.  The authors state on p.11 §1, that current density decreases with increasing potential when Co and Fe are co-electrodeposited. Why is that? From Fig. 6a and 7a it can be seen an increase in current density with more cathodic potentials, independent of ion ratios and the use of ammonium sulphate.

14.  Why is 40 mA/cm² a suitable value? Why not above this value? The explanation given does not seem reasonable.

15.  The XRD results of the Fe and Co films alone should be presented.

16.  Higher magnification SEM images should be provided to qualitatively evaluate film morphology. Also, cross sectional images should be provided to evaluate film structure and thickness, which authors state to be 10 µm in the Abstract only, but do not mention how it was measured.

17.  A careful proofreading should be employed. There are several syntax and orthography errors along the manuscript.

18.  As a final remark, the manuscript lacks discussion of the results. Also, no comparison is made with the literature.

Author Response

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Reviewer 2 Report

The manuscript required following revision:

1. The novelty of the work is missing in the introduction section. Explain it properly.

2. Improve language throughout the manuscript.

3. Improve the introduction based on the following reference on nanomagnetic materials: 

(1. Chapter: Crystal Structures and Properties of Nanomagnetic Materials, ByMirza H. K. Rubel, M. Khalid Hossain, Fundamentals of Low Dimensional Magnets; 

2. Chapter 2 - Classification and properties of nanoparticles, 2022, Pages 15-54, Book: Nanoparticle-Based Polymer Composites)

Author Response

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Reviewer 3 Report

Referee Report

on paper “ Mechanism of (NH₄)₂SO₄ on the Composition and Structure of Fe-Co Alloys “ (coatings-2006353) by authors Yan Wu, Xue Qiao and Wei Wang submitted to Coatings

 

This is interesting and useful paper. It reports the preparation and investigation of the structure and electrochemical performance of the flat Fe-Co film with 10μm successfully prepared by electrodeposition with a non-toxic sulfate solution. The results indicated that the increase of Fe²⁺ and Co²⁺ concentration is benefits to get higher depositing rate. The increase of temperature can speed up the deposition rate of Fe²⁺, and 50°C is a suitable temperature to prepare Fe deposit layer with a flat surface. The increasing the ratios of Co²⁺/(Fe²⁺+Co²⁺) can speed up the co-electrodeposition process of Fe²⁺ and Co²⁺. Secondly, the results of EDS show that Co content in the film is linear increased with the ratios of Co²⁺/(Fe²⁺+Co²⁺) in the solution increases. The Co content in the film is gradually increasing with the rise of the current density. As the concentration of (NH₄)₂SO₄ increases, the content of Co in the film decreases gradually. The obtained experimental results are reliable without any doubts. However, I have some questions and additions. I would like to note a few points to improve the paper before it can be published:

1.    All the motivation should be deleted from the Abstract.

2.    The authors should give examples in 1. Introduction of the formation of thin films by sputtering technique:

(1). K.K. Kadyrzhanov, D.I. Shlimas, A.L. Kozlovskiy, M.V. Zdorovets, Research of the shielding effect and radiation resistance of composite CuBi₂O₄ films as well as their practical applications, J. Mater. Sci.: Mater. Electron. 31 (2020) 11729–11740. https://doi.org/10.1007/s10854-020-03724-w.

(2). S.A. Sharko, A.I. Serokurova, N.N. Novitskii, V.A. Ketsko, M.N. Smirnova, A.H. Almuqrin, M.I. Sayyed, S.V. Trukhanov, A.V. Trukhanov, A new approach to the formation of nanosized gold and beryllium films by ion-beam sputtering deposition, Nanomaterials 12 (2022) 470. https://doi.org/10.3390/nano12030470.

3.    For metal and alloy composite samples the stoichiometry is particularly important. The deviation from stoichiometry and appearance of the oxygen anions can lead to a change in the charge state of the cations, which in turn will greatly change the electronic parameters. That will seriously affect the practical application of the materials obtained. What is the oxygen stoichiometry of prepared samples? It is well known that the complex transition metal compounds easily allow the oxygen excess and/or deficit:

(3). S.V. Trukhanov, A.V. Trukhanov, A.N. Vasiliev, A.M. Balagurov, H. Szymczak, Magnetic state of the structural separated anion-deficient La_0.70Sr_0.30MnO_2.85 manganite, J. Exp. Theor. Phys. 113 (2011) 819-825. https://doi.org/10.1134/S1063776111130127.

(4). A. Kozlovskiy, K. Egizbek, M.V. Zdorovets, M. Ibragimova, A. Shumskaya, A.A. Rogachev, Z.V. Ignatovich, K. Kadyrzhanov, Evaluation of the efficiency of detection and capture of manganese in aqueous solutions of FeCeO_x nanocomposites doped with Nb₂O₅, Sensors 20 (2020) 4851. https://doi.org/10.3390/s20174851.

This should be discussed in 3. Results and discussion.

4.    The authors should give examples in 1. Introduction of the formation of thin films by other techniques:

(5). A.L. Kozlovskiy, M.V. Zdorovets, Synthesis, structural, strength and corrosion properties of thin films of the type CuX (X = Bi, Mg, Ni), J. Mater. Sci.: Mater. Electron. 30 (2019) 11819-11832. https://doi.org/10.1007/s10854-019-01556-x.

(6). T.I. Zubar, T.I. Usovich, D.I. Tishkevich, O.D. Kanafyev, V.A. Fedkin, A.N. Kotelnikova, M.I. Panasyuk, A.S. Kurochka, A.V. Nuriev, A.M. Idris, M.U. Khandaker, S. V. Trukhanov, V.M. Fedosyuk, A.V. Trukhanov, Features of galvanostatic electrodeposition of NiFe films with composition gradient: influence of substrate characteristics, Nanomaterials 12 (2022) 2926. https://doi.org/10.3390/nano12172926.

5.    The proposed 6 papers should be inserted in References.

 

The paper should be sent to me for the second analysis after the moderate revisions.

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Round 2

Reviewer 1 Report

Comment 1: The use of units should be consistent across the manuscript, namely for magnetic induction and coercive force.

Author reply: Indeed, we corrected that and the revised portions are marked with red text in the paper. And others, we understand magnetostriction properties include magnetostriction coefficient and magnetic induction, and the internal stress is the manifestation of coercive force.

R1 reply 1: This was not corrected. Authors use both ‘emu/g’ and ‘T’ for magnetic induction and use both ‘A/m’ and ‘oe’ for coercive force. Authors should select one unit for each property and use it consistently across the manuscript.

Comment 2: The authors do not mention how was compositional analysis performed.

Author reply: We have added that in 2.1. Electrochemical measurements, “The composition and content of the film were analysed by Energy Dispersive Spectrometer (EDS).”

R1 reply 2: Ok.

Comment 3: Since titanium promptly forms titanium oxide, how was the surface pre-treated/activated prior to electroplating?

Author reply: Before that, we soaked it in an acid solution for 10 seconds, which including sulfuric acid, nitric acid, etc.

R1 reply 3: Authors should include that procedure in the Experimental section.

Comment 4: How was the polarisation potential range selected?

Author reply: The initial potential is open-circuitpotential+30mV, and the termination potential is before the limiting current density is reached.

R1 reply 4: Ok.

Comment 5: The authors state that higher Fe²⁺ concentration (or temperature) increases the deposition rate of Fe but process efficiency should have been measured and considered to conclude that, instead of relying on current density values alone.

Author reply: Indeed, we have added the part of electrodeposition rate as follows:

In order to understand the role of (NH₄)₂SO₄ clearly, the effect of (NH₄)₂SO₄ concentration on the electrodeposition rate of Fe-Co alloy was explored as shown in the Fig.8. And the Current efficiency η of Fe-Co alloy was calculated according to equation (1). It can be found that the current efficiency of co-deposition of Fe-Co alloy without (NH₄)₂SO₄ is lower, and (NH₄)₂SO₄ can improve the current efficiency to a certain extent, but considering the influence of (NH₄)₂SO₄ on hydrogen evolution reaction and internal stress, the amount of (NH₄)₂SO₄ should not be too much and it is applicable about 0.18 mol·L^-1.

R1 reply 5: Ok.

Comment 6: The authors observe that small additions of ammonium sulphate reduce current density, whereas higher amounts increase current density. A plausible explanation should be given instead of just describing the results.

Author reply: We are sorry for not making it clear, we believe that a small amount of (NH₄)₂SO₄ adsorbed on the current surface and hindered the hydrogen evolution reaction at the initial stage, so the current density decreased. However, large amounts of (NH₄)₂SO₄ can promote the deposition of metal ions, so the current density increases. And we have added these in the paper.

R1 reply 6: What is the basis for these claims? No references are cited to support this, not in here nor anywhere in the Discussion section.

Comment 7: Similarly, it is said that higher Co²⁺/(Fe²⁺+Co²⁺) ratios can speed up the co-electrodeposition, but no explanation is given for the underlying reasons.

Author reply: We have added the description as follows: “Because the standard electrode potential of Co²⁺ is -0.277V, while the standard electrode potential of Fe²⁺ is -0.440V, so Co²⁺ with more positive potential is preferentially deposited. Therefore, increasing the concentration of Co²⁺ can speed up the co-electrodeposition process.”

R1 reply 7: Ok.

Comment 8: Why are the potentials positive in Fig.8?

Author reply: They are our mistakes, and we have corrected them in the paper.

R1 reply 8: Ok.

Comment 9: How was the Co concentration in the film measured? How about other elemental species such as oxygen, for instance? No description is made in the Experimental section.

Author reply: We have added that in 2.1. Electrochemical measurements, “The composition and content of the film were analysed by Energy Dispersive Spectrometer (EDS).”

R1 reply 9: You still did not measure oxygen content across the film thickness.

Comment 10: Fig.8a and 8b have the exact same legend.

Author reply: We feel sorry and have corrected them.

R1 reply 10: Ok.

Comment 11: What is the ion ratio used in i_Co2+/(Fe2++_Co2+)?

Author reply: We conducted co-deposition experiments with 0.12M Fe²⁺ and 0.06M Co²⁺. In this part, we used this ratio to analyse and compare the results with co-deposition process.

R1 reply 11: The ratio is, thus, 0.33. Compare this number with the axis values on Fig.9a.

Comment 12: The ion ratio axis values in Fig.9a makes no sense considering the concentrations used to prepare the electrolyte.

Author reply: These may be not very significant here, but will help us analyse the hydrogen evolution reaction in the next work, and it's a part of our basis work.

R1 reply 12: It still does not make any sense ratios between 20 and 80. You should correct this.

Comment 13: The authors state on p.11 §1, that current density decreases with increasing potential when Co and Fe are co-electrodeposited. Why is that? From Fig. 6a and 7a it can be seen an increase in current density with more cathodic potentials, independent of ion ratios and the use of ammonium sulphate.

Author reply: Fig.7b is compared with Fig.3b and Fig.5b, we believe that a small amount of (NH₄)₂SO₄ adsorbed on the current surface and hindered the hydrogen evolution reaction at the initial stage, so the current density decreased. However, large amounts of (NH₄)₂SO₄ can promote the deposition of metal ions, so the current density increases. And we have added these in the paper.

R1 reply 13: It still does not explain why. No references are mentioned to support this.

Comment 14: Why is 40 mA/cm² a suitable value? Why not above this value? The explanation given does not seem reasonable.

Author reply: We have corrected the expressions as: “We can see that the Co wt.% in the film linearly gets higher with the increasing current density before 40 mA/cm², and the Co wt.% in the film is significantly slower after 40 mA/cm². In our solution, if the best magnetic properties need 34wt.% Co, according to this regular, the composition of what we want can be controlled by 40 mA/cm².”

R1 reply 14: Why do 34 wt.% of Co give the best magnetic properties? References should be provided. Also, the description made is confusing. It would clearer to state that 40 mA/cm² produces films with 34 wt.% Co which is the desired composition for best properties, instead.

Comment 15: The XRD results of the Fe and Co films alone should be presented.

Author reply: It can be seen in the new Fig.11.

R1 reply 15: There are no XRD patterns for individual Fe and Co films in Fig. 11.

Comment 16: Higher magnification SEM images should be provided to qualitatively evaluate film morphology. Also, cross sectional images should be provided to evaluate film structure and thickness, which authors state to be 10 µm in the Abstract only, but do not mention how it was measured.

Author reply: Indeed, and high magnification SEM micrograph is used to claim flat surface deposit (from 2000x to 20000x). The thickness is measured by the thickness meter with high precision (0.1μm), which have added in 2.1. Electrochemical measurements. The cross section has been provided to evaluate film structure and thickness, and the excess in the picture is caused by scissors when cutting the film.

R1 reply 16: It is not clear what is seen in Fig.13b. The image is just grey.

Comment 17: A careful proofreading should be employed. There are several syntax and orthography errors along the manuscript.

Author reply: Thank you for your warning. We checked the grammar and spelling in the manuscript carefully.

R1 reply 17: There are still instances requiring proofreading.

Comment 18: As a final remark, the manuscript lacks discussion of the results. Also, no comparison is made with the literature.

Author reply: We have added discussion of the results and literatures, and the revised portions are marked with red text in the paper.

R1 reply 18: No reference is presented, no previous work cited, anywhere in the Discussion section. Authors should discuss their results and compare them with the literature. Also, should always cite the claims they made which are not directly derived from their results.

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Reviewer 2 Report

Dear authors,

In the experiment, the 2.2 section can be shown first, and then the 2.1 section. Resolutions of each figure are recommended improve to and Axes title texts of all figures are small (bigger font sizes are suggested).    

Author Response

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Reviewer 3 Report

Referee Report

on paper “ Mechanism of (NH₄)₂SO₄ on the Composition and Structure of Fe-Co Alloys “ (coatings-2006353-v2) by authors Yan Wu, Xue Qiao and Wei Wang submitted to Coatings

 

This paper has been well corrected and it can be reccomended.

Comments for author File: Comments.doc

Author Response

Thanks for your help!

Round 3

Reviewer 1 Report

Comment 11: What is the ion ratio used in i_Co2+/(Fe2++_Co2+)?

Author reply: We conducted co-deposition experiments with 0.12M Fe²⁺ and 0.06M Co²⁺. In this part, we used this ratio to analyse and compare the results with co-deposition process.

R1 reply 11: The ratio is, thus, 0.33. Compare this number with the axis values on Fig.9a.

Author reply: Yes, we should do that: “The relation between i_Co²⁺_{/ (Co}²⁺_{+ Fe}²⁺₎ and Co wt.% in the film without (NH₄)₂SO₄ is shown in Fig. 9 (a). It can be found that with the potential shifts negatively, the current density in Fe²⁺ solution increases more than that in Co²⁺ solution, so the i_Co²⁺_{/( Co}²⁺_{+ Fe}²⁺₎ decreases gradually. The ion ratio used in i_Co²⁺_/(Fe²⁺_+Co²⁺₎ is 33.3%. It can be seen the i_Co²⁺_/(Co²⁺_{+ Fe}²⁺₎ is significantly lower than the Co wt.% in the film (more than 35wt.%). The results show that Fe²⁺ promotes the deposition of Co²⁺ in the solution without (NH₄)₂SO₄. The relation between i_Co²⁺_/(Co²⁺_{+ Fe}²⁺₎ and Co wt.% in the film with (NH₄)₂SO₄ is shown in Fig. 9 (b). It can be found that with the potential shifts negatively, the current density in Co²⁺ solution bigger than that in Fe²⁺ solution, and the i_Co²⁺_{/ (Co}²⁺_{+ Fe}²⁺₎ is significantly larger than the Co wt.% in the film. The results show that the (NH₄)₂SO₄ inhibits the deposition of Co²⁺.”

R1 reply 2: The chart in Fig.9a is the same as the chart in Fig.9b. Authors should correct this.

Comment 12: The ion ratio axis values in Fig.9a makes no sense considering the concentrations used to prepare the electrolyte.

Author reply: These may be not very significant here, but will help us analyse the hydrogen evolution reaction in the next work, and it's a part of our basis work.

R1 reply 12: It still does not make any sense ratios between 20 and 80. You should correct this.

Author reply: Got it. We have corrected as: “The effect of the concentration of Co²⁺ in the solution on the content of Co in the film is shown in Fig. 10 (a). It can be found the Co wt.% in the film is linear increased with the concentration of Co²⁺ in the solution increases. The result indicates no anomalous depositing behaviour occurs in the solution composition, which is different from Fe-Ni alloy film.”

R1 reply 2: The caption of Fig.10a reads: “Effect of the ratios of Co2⁺/(Fe2⁺+Co2⁺) in the solution on the content…”. Authors should correct this.

Comment 15: The XRD results of the Fe and Co films alone should be presented.

Author reply: It can be seen in the new Fig.11.

R1 reply 15: There are no XRD patterns for individual Fe and Co films in Fig. 11.

Author reply: It can be seen in the new Fig.11.

R1 reply 2: I meant the XRD data acquired for single Fe and Co films alone, not the PDF pattern.

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