Synthesis and Morphological Characterization of Electroless-Deposited Ni-P Coatings on Diamond Abrasives

Round 1

Reviewer 1 Report

Totally, this is an interesting paper. It can potentially be considered for publication after addressing the following minor issues. The adhesion of the coating results need to be provided and quantified in the article as that data is presented and ties together the results.

Comments for author File: Comments.pdf

Author Response

Please see attached.

Author Response File: Author Response.docx

Reviewer 2 Report

I'd like to congratulate the authors for the extensive research work reported in this paper. I recommend its publication. However, I believe this paper would benefit from some improvements. I will now only ask or comment questionable things or things that I do not understand/don't agree.

1) Line 27 - you state that "the work is beneficial to semiconductor..." but then throughout the paper there's no mention as to how your study can be applied for the benefit of semiconductor manufacturing. You should highlight that in results and discussion, where you see fit.

2) You performed sensitization/activation with the traditionally used tin/palladium. However, this has been more and more replaced by seeding the surface with other metals, even the metal to be plated, as catalyst. Have you tried that or considered that? It would be less expensive and more environment friendly.

3) Line 162 - "In, the optical images..." this sentence in incomprehensible

4) Line 169 - you can't deliver a paper where you state that you've mishandled samples. The reader can and will question the rest of the work. Please provide the missing images.

5) Figure 2  - what was the criteria to choose the angle? Was it random? Furthermore I found it difficult to agree with your comments on the images as the resolution is really low. Perhaps it would be better if you omit images for 20 and 60 minutes, or just one angle.

6) Lines 174 and 178 - "Figure V.1" I assumed you meant Figure 2. Please correct this.

7) Line 256 - I ask how is that possible that plating can proceed on the site where coating was peeled off? Do you know for sure if the catalyst cluster didn't come off with the coating?

8) Line 306-311 - That is indeed true, considering that the light position form the optical microscope was always on the same position, so that the incident lighting angle is the same.

9) Figure 4 - why isn't there an image for Ni:P1:1-30 min and Ni:P1:3 - 180 minutes???

10) Figure 5 - from which bath is this sample? You have to make that clear...also what is that feature inside the red box? Is that a fracture, film peeling off? The dark area without hemispheres is the diamond substrate? Again, this is not clear...

11) Figure 6 - Figure 3 shows the Pd catalysts as nanoparticles or clusters, yet in this figure you drew it as a layer and then you have independent nucleation sites. Whether the Pd catalyst is present in the form of a continuous layer is dependent on the sensitization duration. In your case, 2 minutes might not me enough time. Furthermore, the nucleation sites are the Pd nanoparticles/clusters. You should redraw this.

11) Line 363-366 - the thickness of the coating is not yet visible at this point. This sentence should be relocated after Figure 8.

12) Line 379-380 - the lower nucleation density is also due to less Pd catalyst being on the peeled off surface.

13) 3.2.3 Substrate Morphology - usually a black powder like substance, with low density, will appear floating in the bath. Has this been observed in your bath? This section should be complemented with some reference.

14) Line 439 - you observe a non-uniformity in the thickness which you attribute to X-Ray scattering making the edges look thicker. However that was not the justification you gave for thicker edges before (line 363-366). Then you state that the edges have less scattering effect. If this was to be true, then your standard deviation (please change de colour of the error bar, it is almost invisible) in the edges would be smaller than in other faces. Your coating thickness is not uniform for a lot of reasons that you yourselves have mentioned before: different nodular morphologies, deposition occurs while detachment of the film also takes place, hindering spots where the thickness will be different, deffects, rough and smooth faces...even the optical images leads one to "foresee" that the coating coverage doesn't happen at the same time for all the diamond faces.

15) Figure 10 - Ni:P=1:3 stops at 60 minutes, and also for the following graphs, why? I see an increasing trend, the plateau you mention is not visible. It might be visible from 180 minutes up, but not before. It looks like 1:3 ha reached a plateau, but we cannot conclude that has there is data points missing.

16) Line 466 -472: what I see here is the relationship between hypophosphite concentration at different deposition times. Nickel metal concentration is the same for every bath, the variable is the reducing agent and then Figure 12 and 13 follows the same principle: what you're measuring is the influence of hypophosphite concentration on the deposition rate and therefore on the amount of Ni species present in the bath. This chapter needs to be rewritten. It is ok up until Figure 11, but then the assumptions you make are wrong.

17) It would be welcome if you could stablish a correlation between failure and coating integrity. It is not straightforward for the reader that a rough substrate gives a good coating in terms of failure.

18) Line 563-569: "phosphorous content will decrease as the thickness of the coating increases". Phosphorous content depends on the concentration of reducing agent in the bath, not on the thickness of the coating. Do you have a reference for this affirmation?

19) 3.4.4. Failure Mechanism: I think you could explore here how you can use this information in favour of the possible application written in the abstract...

20) Conclusion:point 3...see my 16th comment

21) Bad written URLs in the literature: "doi:http://dx.doi.org/" --> "http://dx.doi.org/". Some of the links my PDF reader do not accept if I click on it. Please check.

Author Response

Please see attached. 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear authors, congratulations or your extensive and valuable work!