Tribological and Thermal Transport of Ag-Vegetable Nanofluids Prepared by Laser Ablation

Round 1

Reviewer 1 Report

Dear authors,

This version of the manuscript shows a remarkable improvement compared with the origina version.

Reviewer 2 Report

The response of the authors to my comments is satisfactory.

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 experimental study describing the preparation of vegetable oil stabilized silver nanofluid by pulsed laser ablation in liquid. Thermal and tribological performances of such nanofluid were evaluated. However, there are several serious shortcomings. Therefore, I cannot recommend the manuscript for publication.

 

The SEM results and DLS results are not consistent.

 

The authors prepared the silver nanoparticles in vegetable oil, which is without water. The term of ‘hydrodynamic size’ is not correct.

 

Authors only give the numbers of sizes from DLS measurements. Please provide the DLS results with curves and polydispersity index (PDI).

 

Since refractive index and viscosity of the medium are needed for the DLS measurements, the refractive index of the vegetable fluids should be provided in table 1.

 

References dealing with the equation (1) should be added.

 

The authors mentioned in ‘Introduction’ about the limited oxidation stability of vegetable oil, but no experiment was done according to this aspect.

 

The ‘Results’ in the ms. are about the procedures of thermal conductivity and tribological characterization, which should be part of the materials and methods section.

 

There is no ‘conclusion’ in this ms.

 

This ms. is very similar with ref. 1 (Tribological and Thermal Transport Performance of SiO2-Based Natural Lubricants. Lubricants 2019, 7, 71). Two many sentences were copied from ref.1 without change.

Reviewer 2 Report

The paper describes experimental data for the tribological and thermal transport performance of Ag-vegetable nanofluids. The effects are relatively modest probably because the concentrations of the Ag nanoparticles are extremely small; the authors should have plotted that data as a function of the Ag nanoparticle concentration rather than the laser ablation times, which is the more fundamental variable. They should also have explained the expected upper limit of this concentration to give an indication of the potential of the approach. The paper lacks a detailed discussion section that describes a fundamental interpretation of the data. Moreover, the paper has no conclusions.

Reviewer 3 Report

Vegetable-oil based nano-lubricants is a very interesting topic. In recent years, there has been growing concern on the use of petroleum-based lubricants. Vegetable oils possess high lubricity, high viscosity index, and low volatility which are excellent lubricating properties. Since the main drawback of vegetable oils is poor oxidation, much has been given in improving thermo-oxidation. In the present study, the authors prepared vegetable-based nano-lubricants by mixing Ag nanoparticles with three different vegetable oils. The Ag nanoparticles were synthesized using the Pulsed Laser Ablation in Liquid (PLAL) technique. Several analytical techniques were used to characterize the particles and the nano-lubricants. The thermal conductivity and tribological properties were determined. According to the results, it was found an improvement in the thermal conductivity and the tribological properties of the nano-lubricants due to the presence of the Ag nanoparticles.

Even though the paper presents good information, there are several flaws that should be attended. For example:

1. Lines 101 – 104: “Herein we show, through experimental studies, the effects of Ag nanostructures reinforcement by pulsed laser ablation technique dispersed within vegetable lubricants (soybean oil, sunflower oil and corn oil) to improve their thermal and tribological properties: thermal conductivity, COF, wear resistance and load-carrying capacity.”…….

The objective MUST be re-written. It seems that all the ideas are scrambled, and the authors failed in communicate the purpose of the study.

2. From the wide spectra of vegetable oils, why the authors are interested in study the effect of Ag nanoparticles on soybean, corn, and sunflower oils in particular?

3. The selection of these three vegetable oils should be justified in the introduction.

4. The paragraph from lines 106 to 111 should be included in the section 2.1 Nanofluids preparation.

5. Lines 119 – 120: “Laser pulse energy measured was 300 mJ/pulse and the ablation fluence at this distance was estimated as 2.4 J/cm2.”…..What technique was used to estimate this value?

6. Figure 1 should be moved to the results section.

7. Lines 134-135: “The images show spherical morphology for the silver nanoparticles in general”….This statement is not accurate. In my opinion, it is hard to say that silver nanoparticles are spherical in general, based on the SEM pictures shown. Furthermore, it is hard to see a difference between Figures 1a and 1b.

8. Lines 149-150: “The separation of the peaks was evaluated as 6.01 eV which is also in agreement with the results reported in literature.”….. Please include references.

9. Sections 2.3 and 2.4 describe analytical techniques and the results from the different analysis are included in the same paragraph. The results must be in presented in the results section.

10. Line 178: “3.1. Thermal conductivity characterization” ….paragraph from lines 179 to 186 belongs to section Materials and Methods.

11. The information between lines 188 and 202 belongs to the section Materials and Methods.

12. Lines 205-212: Results of the thermal conductivity and tribological properties are described but not discussed or compared with the literature. For example: What is the role of the particle size and the concentration in the enhancement of the thermal conductivity and the tribological properties? Why? A comprehensive explanation of the results is required.

13. Please include a Conclusions section.

14. A suggestion for the title: “Tribological and thermal transport performance of Ag-vegetable nanofluids prepared by laser ablation.”

15. The manuscript must be written in third person.

16. The authors need to improve the language of the manuscript, not only grammar but also the accuracy of statements and descriptions.