Study on Adhesion Properties and Process Parameters of Electroless Deposited Ni-P Alloy for PEEK and Its Modified Materials
Round 1
Reviewer 1 Report
The manuscript submitted by Gao et al. shows an interesting approach based on surface roughness to increase the adsorption of conductive layers (Ni-P allowed in this study) onto the non-conductive PEEK polymer. The process is highly interesting, and efficient and has huge potential for industrial scalability. The figures and explanations are clear, with special mention of the work in the Figure 1 scheme. The work is worthy of publication in the journal after some adjustments. Overall, the novelty and motivation behind the different experiments need to be improved to understand better the work and the high impact in the scientific field. Some point-by-point comments are provided here:
1) Why shall we coat a non-conductive PEEK polymer to provide high surface conductivity? The motivation for doing this process should be very clear.
2) Electroless should be better defined to avoid confusing the reader. Maybe be more explicit and state in the text that the process is carried out without current/high energy, such as in electroplating.
3) The novelty of the work compared to similar literature should be stated in the abstract and the conclusions.
4) More information should be included regarding the PEEK molecular weight and grade.
5) Regarding the method to increase surface roughness, how experimentally scalable is this technique? Could other methods, such as sandblasting, be used as an alternative method to create controlled-surface roughness? Please, reflect on this. Some suggested literature to consider: https://doi.org/10.1039/D2MA00249C and DOI: 10.1039/D1RA05448A
6) The experimental work should be described clearly. For instance, in line 146, which constant rate was used? How was the damage to the coating evaluated before increasing the load?
7) Table 2 presents the different parameters tested. The authors did not evaluate time. Do the authors consider that time is not critical in this process, or is the motivation to choose these parameters from previous literature?
8) How sustainable is the process in terms of chemicals used? Can they be re-used? How expensive is the process?
9) Figure 4. Adding the particle size distribution of the different coating growth processes is important.
10) How is the data statistically evaluated? How many replicates were tested (see, for instance, figure 7)?
11) Do the authors consider evaluating surface area instead of roughness?
12) Which specific applications can be targeted for the materials produced?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
There are too many unclear and confusing formulations in the work. Furthermore, many claims are made that are not supported by experimental data. Interpretation of experimental data is done with some text containing electrochemical terms that are loosely used of which I am not convinced that all is correct. Furthermore, citing a paper (about the physics of ion collision and heavy ions !) that has got absolutely nothing to do with the topic discussed by the authors is not acceptable. From line 289 onwards, there is a lot of speculation, with text that gives me a strong suspicion to have been inspired on other literature sources. Proper explanations and critical data to support claims are missing !
Therefore, I advise to reject the paper.
Additional comments and suggestions can be found below:
Line 11-12
[The application effect of the plated parts is significantly impacted by the bonding strength between PEEK and coating, but there is currently little research on this topic.]
This Reviewer is inclined to disagree what that statement, more specifically the part [but there is currently little research on this topic.]. There is a lot of research that has been done about the adhesion strength of electroless metal deposits and polymeric material parts.
On line 40-41, the authors are making a comment: [They are widely used in aviation, medi- cal, energy, chemical, and other industries.] that might suggest there is a lot of research done, as I would assume that a process is not used in an industrial context if there is no deeper understanding on how it works and what the optimal process parameters are. The authors should rephrase the statement from the Abstract to be in line with state-of-the-art of the research field and reality.
Line 12
Sentence starting with [While the bonding...] should be rewritten. Starting a sentence with ‘while’ implies that an argument and counterargument are following, which is not the case here.
Line 104
[Profifiler]
Typo ?
[Profiler]
Section 2.3
When the authors are referring to ‘palladium’ in the activation, the correct symbol for the element is ‘Pd’ and not ‘Pa’
Line 108
[Electroless Ni-P alloy is an autocatalytic process]
Subject is missing in that line
[Electroless Ni-P alloy deposition is an autocatalytic process]
Line 109
[The process of electroless Ni-P alloy on the]
>
[The process of electroless Ni-P alloy deposition on the]
Table 2
[PH} > [pH]
Line 169
[were got]
Check English
Figure 3 caption
Although it can be inferred from the scale bars, it should be mentioned what the top and bottom row of the SEM images are (it is only mentioned in the text)
Line 197-198
[with each another]
Is that correct English ?
[with each other]
Line 230
[gravitation]
Is gravitation really a force to take into account ? Isn’t that only the case when the ‘coating’ is extremely loosely ‘adhering’ to the substrate, and it, therefore, matters whether the substrate held upside down or not ?
Line 234
[gravitation between atoms and molecules]
When reading this comment, it becomes clear the authors mean something different. I think the choice of the word ‘gravitation’ in this context is wrong and it should be avoided.
Line 233-234
[, the distance between the coating and the substrate was far]
The coating is in direct contact with the substrate. That is not far !
I think the part about ‘gravitation’ is not scientific, confusing, and simply wrong. This should be rewritten.
Line 248
[etching depth was too deep]
A ‘depth’ cannot be ‘deep’ ! Please reformulate
Figure 9 caption.
Although it can be inferred from the scale bars, it should be mentioned what the top and bottom row of the SEM images are.
Figure 11c
[PH] > [pH]
Figure 11a+b
It should be mentioned clearly in the text describing the figures, as well as in the caption what the value of the non-varied parameter is. Figure 11a: what is the hypophosphite concentration ? Figure 11b: what is the nickel concentration ?
Line 291-292
[on the one hand, the redox potential moves forward with the increase of nickel ion concentration in the solution]
Unclear, confusing formulation. Non-scientific. What is meant by ‘moves forward’ ? That is unclear. Does it become more positive or negative ? Please explain this properly, for instance in the Introduction.
Line 289-307
The authors should spend more effort to explain what goes on. The explanation of the results from Figure 11a + 11b seems to be heavily inspired by literature sources. ‘Free energy’ is loosely applied, it is not clear to the non-expert reader what is exactly meant.
Line 303
[The free energy moved in the negative direction]
This is stated as a fact. Please provide experimental data that supports this claim.
Line 289-291
[The variation of deposition rate with nickel sulfate concentration could be explained by the redox reaction potential [28]:]
Reference [28] as included by the authors has got nothing to do with the statement in that sentence. Furthermore, it has got nothing to do at all with electroless metal deposition, nor anything else in the manuscript.
[28]: {Statistical model description of particle multiplicities in heavy ion collisions} has got nothing to do with the present work. The words ‘metal’ ‘plating’ ‘deposition’ ‘electroless’ are not even mentioned in the work about the physics of particle production in heavy ion collisions.
Line 295-296
[The replenishment of this concentration difference is realized by the diffusion of ions in the plating solution to the liquid layer on the surface of the substrate. ]
Did the authors perform dedicated experiments to investigate this hypothesis ? Is there any proof this speculative comment is correct ?
Line 313-315
[When the concentration of sodium hypophosphite was lower than 30 g/L, the increase of sodium hypophosphite concentration led to an increase of total redox reaction potential]
Please provide experimental data that support the claim of a change in redox potential. Seems unfounded.
Line 316
[The free energy moved in the negative direction,]
Please provide experimental data to support this claim.
Line 319-320
[The free energy moved in the positive direction]
Please provide experimental data to support this claim.
Line 329-332
[When the pH reached a high value, the concentration of H+ decreased slowly with the increase of pH, while the concentration of OH increased sharply, inhibiting the positive reaction of reaction formula (3) and reducing the deposition rate. ]
Why would H+ concentration increase slowly and OH- concentration increase sharply ? These concentrations have a ‘coupled relation’.
What is a ‘positive reaction’ ?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The author have inversigated the adhesion properties of the Ni-P-fiber reinforced PEEK coating by varying the surface roughness, the article is well written and intersting, however the following issues have to be addressed.
1- Please change the title and use the new title including the word of adhesion properties.
2- In the second paraghraph of the introduction kindly remove discusing about chemical vapor deposition and physical vapor deposition which are not relevant to your topic. Instead the comparison between Ni-B and Ni-B coating is needed using the recent (less than 3 years) refrences related to adhesion and mechanical properties of these coatings should be added such as:
a) Yazdani, S., & Vitry, V. (2023). RSM models approach for optimization of the mechanical properties of electroless Ni-B-nanodiamond coating: An experimental and molecular dynamic simulation study. Surface and Coatings Technology, 452, 129133.
b) Yazdani, S., Chapon, P., Dupont, V., & Vitry, V. (2023). Role of CTAB surfactant on electroless Ni–B deposition and its mechanical and corrosion behaviour. Surface Engineering, 1-11.
c) Vitry, V., Hastir, J., Mégret, A., Yazdani, S., Yunacti, M., & Bonin, L. (2022). Recent advances in electroless nickel‑boron coatings. Surface and Coatings Technology, 429, 127937.
d) Tamilarasan, T. R., Rajendran, R., Sanjith, U., Rajagopal, G., & Sudagar, J. (2016). Wear and scratch behaviour of electroless Ni-P-nano-TiO2: Effect of surfactants. Wear, 346, 148-157.
3- Is there any specific reason for choosing the scratch load in this article not higher than 10 N?
4- Does the authors have tried to measure the hardness value of the coating?
5-Kindly rewrite the conclusion, and at the mention the application of your work
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
In this work, electroless plating is used to develop a Ni-P alloy coating upon the surface of PEEK and PEEK reinforced with glass or carbon fibers. In general, the manuscript is well written. The results are presented in clear way and various interpretations are provided to support the conclusions. Some information is missing in the experimental part and some minor revisions are needed in the Results section. Below are some more specific comments.
1. It would be better to revise Title and include the Ni-P alloy.
2. line 12. Please replace “while” with another more appropriate term.
3. Introduction. Aren’t there any other references for Ni-P alloy coated in polymeric materials? If yes, please include some more references.
4. Lines 100-101. The different roughness was achieved by the same solution (H2SO4+H3PO4) by exposing the samples for different times? What was the time? The procedure took place at room temperature without heating?
5. PaCl2 as well as the two acids, are not mentioned in section 2.1.
6. Table 2. What were the constant values of the other parameters ? For example when studying the effect of nickel sulfate concentration what was the pH, temperature etc?
7. Figure 6. Did the friction and microscopic observation approach give similar results regarding the adhesion force?
8. Lines 273-274 and Figure 10. What is the companion sample?
9. Line 327. Reaction formula 2 not reaction formula 5? Similarly line 332. Formula 3 not 5?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The revised version has answered the issues raised by the reviewers. For the last minor comment, I suggest the authors add the units for the molecular weight of the PEEK.
Reviewer 2 Report
The authors have revised the manuscript, taking into account the suggestions. The work can be accepted in its current form.
Reviewer 3 Report
The article has been well revised and it can be accepted in the present form.
