Effect of Thiourea Containing Composite Additives on Nickel Electrodeposition in Ammoniacal Solution

Round 1

Reviewer 1 Report

The paper is accepted for publication as an original scientific paper.

This series of experiments summarizes an initial series of results. The
effect of thiourea and thiourea containing composite additives on nickel
electrodeposition from ammoniacal solution was investigated. The results
could be supplemented with Transmission Electonmicroscopy TEM results.

Author Response

Thank you very much for your comments!

Frankly speaking，there are obstacles for us to supplement with TEM results based on our current experimental conditions. In addition, the effect of additives on TEM results may not obvious and the lattice may hardly unchanged due to the extremely low dosage of additives.Therefor, it may be unnecessary to conduct the TEM test.

Reviewer 2 Report

The presented data are of low significance for the overall problem of Ni deposition.  

Please see the attachment for details.

Comments for author File: Comments.pdf

Author Response

Thank you very much for your comments!

Frankly speaking，it true that there was not enough in-depth study and new information in this manuscript about the effect of composite additives on nickel electrodeposition. However, some differences caused by composite additives have been found, which was beneficial for understanding the mechanisms and facilitating the rational design of additives for metal electrodeposition.

In the 1960s-1970s a very large number of studies were carried out on nickel electrodeposition mainly concentrated on acidic system, which has mature process technologyis at present. But few studies focus on ammoniacal solutions due to the complex nickel species and low current efficiency. It is no doubt that many factors (solution components, temperature, current density, additives. etc ) can effect the structure and the properties of nickel deposits. However, how additives affect the metal electrodeposition process is still controversial, and most of the explanations are based on the selective adsorption mechanism of additives, which is considered that the adsorption of additives depends on the surface shape of the electrode and is preferentially adsorbed at the protruding part or the part with high current density.

Cyclic voltammetry is one of the most widely used electrochemical methods in the study of electrodes. It has the characteristics of simple operation and intuitive spectrum analysis. According to the shape and peaks of cyclic voltammetry curves, the reversibility of electrode reaction, control steps of electrode process, electrode reaction process and adsorption or desorption of electroactive substances can be analyzed. As for potential measurements, stationary curves are more informative than cyclic voltammograms indeed. In this study, the cyclic voltammetry tests were done at least three times to obtain results with good agreement and the scanning rate was relatively slow at open circuit potential. The Tafel slope, cathodic transfer coefficient, exchange current density and surface coverage of additive can be obtained by linear scanning voltammetry (LSV).but I'm very sorry that we didn't finish the LSV test.

The Sharifker-Hills theory was described in detail in the article as we have calculated the apparent activation energy (much less than 40 kJ / mol) and confirmed that the electrode reaction is controlled by diffusion step in our previous work (https://doi.org/10.1007/s12598-017-0975-9). That value of diffusion coefficients mainly depends on temperature and depends weakly on the additives, which is consistent with our experimental results.

As a rule, additives lead to smoother surface as a result of their adsorption. In this work, we have obtained smoother nickel surface by adding composite additives and our work focuses more on synergistic effect of thiourea compounding with different types of additives rather than process parameters.

Author Response File: Author Response.pdf

Reviewer 3 Report

I have reviewed this paper three times already, and the authors still think that there is preferred orientation as shown by XRD, when there is not.

Also, Ni only exists in fcc.

The descriptions of the particles need tidying.

 

Comments for author File: Comments.pdf

Author Response

Thank you very much for your comments again!

I'm sorry, it's my fault that I have not understand the preferred orientation of the crystal plane enough. We have revised the manuscript again according to your opinions.

We have deleted the contents related to preferential orientation and texture coefficient.

In Section 3.3, "loose" means the way of the particles packed.

Reviewer 4 Report

Paper devoted to investigation of effect of thiourea containing composite additives on nickel electrodeposition in ammoniacal solution. This composite additives have an important influence on the process of  electrodeposition and the quality of metal deposited layer. I believe that  results of these studies are relevant, but there are the following comments on the paper:

1. In the introduction it is necessary to indicate that nickel is widely used as a matrix of composite electrochemical coatings and cite the following publications:

- Tseluikin V.N., Vasilenko E.A. Electrodeposition and properties of composite coatings based on nickel // Russian Journal of Applied Chemistry. 2011. V. 84, № 11. P. 2005 – 2007.

- Gobinda Gyawali, Bhupendra Joshi, Khagendra Tripathi, Soo Wohn Lee. Effect of ultrasonic nanocrystal surface modification on properties of electrodeposited Ni and Ni-SiC composite coatings // Journal of Materials Engeneerig and Performance. 2017. V. 26. P. 4462 – 4469.

- Lanzutti A., Lekka M., de Leitenburg C., Fedrizzi L. Effect of pulse current on wear behaviour of Ni matrix micro- and nano-SiC composite coatings at room and elevated temperature // Tribology International. 2019. V. 132, P. 50 – 61.

2. Conclusions should be made more specific and divided into several points.

Author Response

We have introduced that nickel is widely used as the matrix of composite electrochemical coatings and cited the publications proposed by the reviewer in the Introduction section. In addition, we have modified the conclusions according to the suggestions of the reviewer.

Round 2

Reviewer 2 Report

All accents are correctly made in the augmented text, which increased its informativeness.

Author Response

Thank you very much for your pertinent comments！It is my pleasure to have academic  exchange and communication with you from mind to mind.

Reviewer 3 Report

Although some corrections have been done, not all have been done. There is at least one part which is pure speculation and should be deleted.

Why do you keep insisting that the orientation of nickel changes, when it does not?

The paper should be written in the past tense, and in the third person.

Comments for author File: Comments.pdf

Author Response

Thank you very much for your pertinent comments! We have carefully revised the manuscript according to your attached scan. Here are some explanations to the doubts.

We have deleted the part which was pure speculation and revised the writing tense.

In Section 3.3, "loose" means particles packed in some areas, but not in some other areas. This can be explained by selective adsorption mechanism of additives. The adsorption of additives depends on the surface shape of the electrode. Actually, how additives affect the metal electrodeposition process is still controversial, most of the explanations are based on the selective adsorption mechanism, which considered that additives are preferentially adsorbed at the protruding part or the part with high current density and then inhibit the ion discharge process. Therefore, the discharge ion can only discharge in the concave points of the electrode surface, which result a smooth surface.

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 is an interesting paper, but there are several problems. In some places there appears to be no evidence for what is described in the text (see the attached scan). The microstructres are too small to see what is being written about them. The "preferred orientation" is misinterpreted, because the peak intensities are mostly due to the number of planes that give the peak. To have preferred orientation, the peak intensities need to be very different from those in the reference data. Measured values should be given ± standard deviation (else how can the reproducibility be assessed?).

Additionally, it is long-winded and should be written in the past tense. There are places where a reference should be given. There are also places which are not clear.

More details are given in the attached scan.

Comments for author File: Comments.pdf

Author Response

Thank you very much for your comments! We have carefully revised the manuscript according to your attached scan. Here are some explanations to the doubts.

1.Although the electrochemical tests were done at least three times, we just to obtain results with good agreement and take the experimental results with the highest agreement.

2.Generally, the “preferred orientation” is characterized by texture degree, the calculation method is supplemented in the experimental part of the revised manuscript, and the relevant literatures were cited. Sometimes, the crystal plane with the strongest diffraction peak may not the preferred orientation plane.

3. It cannot be denied that the microstructres are too small to see, but they can still reflect the differences between each other.

4.In part 3.2, you mentioned “How do you know they are 3D?”. There are 2D and 3D nucleation modes, which can be judged from the shape of the I-t curves directly.

5.Fig.7 is not the preferred orientation of nickel but the texture degree of crystal plane.

6. Most of values in the Tables were calculated according to the formulas and should not be given ± standard deviation.

Reviewer 2 Report

The paper under review deals with the research on effect of thiourea containing composite additives on nickel electrodeposition in ammoniacal solution. The results in the study are achieved via various experimental data. The article tackles an important issue which is suitable for Crystals. 

Comments:
1)    In my opinion, the novelty of the research is “hardly visible” (debatable). I think the Authors should indicate the novelty and provide a specific purpose and conclusions. The abstract and conclusions require changes.
2)    The authors were not able to fully explain some of the results obtained and plan further research and exploration of the topic. What kind of research are planned?

The paper is well prepared and written in good English. The article contains adequate and appropriately selected 28 literature items. In opinion of the reviewer the article needs minor correction/complete with data and provide a specific purpose and conclusions.

Author Response

Point: The paper under review deals with the research on effect of thiourea containing composite additives on nickel electrodeposition in ammoniacal solution. The results in the study are achieved via various experimental data. The article tackles an important issue which is suitable for Crystals.

 

Comments:

1)    In my opinion, the novelty of the research is “hardly visible” (debatable). I think the Authors should indicate the novelty and provide a specific purpose and conclusions. The abstract and conclusions require changes.

2)    The authors were not able to fully explain some of the results obtained and plan further research and exploration of the topic. What kind of research are planned?

 

The paper is well prepared and written in good English. The article contains adequate and appropriately selected 28 literature items. In opinion of the reviewer the article needs minor correction/complete with data and provide a specific purpose and conclusions.

 

Response :

 

(1)  Nickel electrodeposition from ammonia-containing solution is new systems and there are still many problems mentioned in the manuscript. Surface quality and performance is one of the  most important problems. In this work we assumed if by adding thiourea with three kinds of additives (CTAC, SDS and PEG 20,000), the deposits quality and performance would be modified because of their synergistic effect. Also the mechanism of composite additives were also studied.

(2) It is very difficult to study the action mechanism of micro additives under the existing technology and conditions. The explanation of additive mechanism can only be based on some existing theories and models. Next, we hope to combine optical technology (X-ray in situ imaging technology) to further explore the action mechanism of additives.

Author Response File: Author Response.pdf

Reviewer 3 Report

The objective of the paper, stated as the study on the introduction of composite additives in process of metal electrodeposition has been achieved so that the conclusion that these additives play an  important role in forming compact and  smooth nickel deposits proved to be adequate.

The paper is well structured, still some clarification would be required, as follows:

• explain the reason of choosing the additives mentioned (CTAC, SDS and PEG 20,000);
• it would be of benefit for the paper to show some images taken while experimenting;
• explain how the plotted graphs (Figure 2, 3, 4, 6) were obtained - was it a special data acquisition software or the regression curves for distinct experimental data, or what else ?

- Check English (for example, line 17 "(...) played a most important role"

Author Response

Point: The objective of the paper, stated as the study on the introduction of composite additives in process of metal electrodeposition has been achieved so that the conclusion that these additives play an  important role in forming compact and  smooth nickel deposits proved to be adequate.

The paper is well structured, still some clarification would be required, as follows:

• Explain the reason of choosing the additives mentioned (CTAC, SDS and PEG 20,000);

(2) It would be of benefit for the paper to show some images taken while experimenting;

(3) Explain how the plotted graphs (Figure 2, 3, 4, 6) were obtained - was it a special data acquisition software or the regression curves for distinct experimental data, or what else ?

 

Response :

(1) Thiourea is an additive widely used in the field of metal electrodeposition, and has a good effect on improving metal surface quality. CTAC, SDS and PEG 20,000 are three different types of additives. CTAC belongs to cationic additive, SDS belongs to anionic additive and PEG20000 belongs to non ionic additive. it was assumed that if by adding thiourea with these additives, the deposits quality and performance would be modified because of their synergistic effect.

(2) We have taken some images during nickel electrodeposition, but this paper mainly discussed the mechanism of additives and it may not be suitable to show those photos.

(3) The curves for Fig.2, 3, 6 were directly measured by the electrochemical workstation. The curves for Fig.4 were fitted according to Fig.3 and Eq. (4)–(5).

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Many corrections not done from before. Only the cosmetic corrections have been done. The samples do NOT show preferred orientation, as was pointed out in the previous review. There are still no standard deviations given in Table 1. Figure 5 is bad because the features descibed in the text are not clear, so do they even exist? The optical micrographs are a waste of space and should be deleted to make the SEM-SE images larger and clearer.

Comments for author File: Comments.pdf

Author Response

Thank you very much for your comments again! We have carefully revised the manuscript according to your points one by one. Please attach the files for details

Author Response File: Author Response.docx

Round 3

Reviewer 1 Report

Still not all the corrections have been done, form the review of the first submission. The texture is a serious misinterpretation, and an XRD textbook needs to consulted. The errors could be obtained by obtaining the standard deviations. Alternatively, the likely errors could be obtained from the likely differences in the formulae: this is shown in elementary physics textbooks.

Comments for author File: Comments.pdf