An Experimental Investigation of the Tribological Performance and Dispersibility of 2D Nanoparticles as Oil Additives
Round 1
Reviewer 1 Report
In this study, the authors approached an interesting research of the tribological performance of nanofluids. The most interesting part is the aged lubricants to explore the re-usage of degraded lubricants by doping of nanomaterials. I also want to value the bibliographic work of the paper.
However, there are major and minor changes to be addressed before publication.
Major comment.
In page 15, lines 482-484. "it is possible to conclude that the formation of oxide layers on the surface decrease the coefficient of friction (COF) but increases wear in the form of oxides when the lubricant has degraded". I understand that the geometry of the disk is an additional difficulty to further explore this statement. But, I encourage the authors to carry out further experiments by means of SEM (including EDX) or profilometry of the disk. At least EDX of the wear debris can be helpful.
Minor comment.
The authors comment that the viscosity changes with shear rate. I agree that this kind of nanofluids usually present a non-Newtonian behavior. However, this is easy to prove and measure. Why the authors have not tested the viscoelasticity of the lubricants?
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper deals with an experimental investigation of the tribological performance and dispersibility of 2D nanoparticles as Oil Additives. Four distinct nanomaterials graphene, rGO, hBN, and MoS2 were studied. Having been investigated by the authors, enhanced wear volume and reduced friction were obtained. The results are good. But I think there are still some areas in the paper that need to be improved before final acceptance of the paper.
1. It can be seen that the authors have devoted a lot of energy to drawing Figure 1. However, the figure is too small to be readable. Like Figure 1 (i), the details of the specific friction test cannot be clearly seen.
2. The author chooses four kinds of nanomaterials (graphene, rGO, hBN, and MoS2) as the research object. Which material has the best effect?
3. How many times were the friction tests repeated in each group? This relates to the reliability of the wear data.
4. There are some errors or irregularities in the English expression of the paper, which need to be corrected carefully.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have answered my comments almost successfully. The non-Newtonian behavior found in the three samples is worthy to further exploration. There are Newtonian and non-Newtonian regions, which should be ascribed to the formation of a three-dimensional network of the nanomaterials into the oil. These network might be disrupted by the shear stress. Since there are three several regions, probably there are small aggregates or moieties of nanoparticles which are firstly disrupted and domains with completely disperse nanoparticles forming a gel-like structure which is disrupted at higher shear rates. I recommend to add the viscosity curve of the pristine oil to see if the nanofluids finally reach its value of viscosity. I also re-recomend to try to fit the results according to the usual viscoelastic models I suggested in my previous review. Since there are several regions in the viscosity curves, it will be necesary to fit each regions instead of the whole curve.
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
The revised paper can be accepted.
Author Response
We would like to express our heartfelt gratitude for accepting the manuscript entitled "An Experimental Investigation of the Tribological Performance and Dispersibility of 2D Nanoparticles as Oil Additives."
Thank you for taking the time to read our work.
