A Wind Tunnel Test of the Anti-Icing Properties of MoS2/ZnO Hydrophobic Nano-Coatings for Wind Turbine Blades
Round 1
Reviewer 1 Report
The manuscript ID: coatings-2255584 entitled: „A Wind Tunnel Test on Anti-icing Property of MoS2/ZnO Hydrophobic Nano coating for Wind Turbine Blades” describes the using of MoS2/ZnO and MoS2 as a passive anti-icing material for wind turbine blades.
The manuscript is interesting but the authors should to take into consideretion the followings:
· Whole manuscript presents the nano-anti-icing coating prepared by hydrothermal method and liquid phase method (MoS2/ZnO; MoS2) by ingnoring the presence of PDMS.
· The coated blade was realized by sprayed the suspension obtained by mixed PDMS with nanomaterials based on MoS2/ZnO or MoS2.
· GFRP blade uncoated has a CA of 62.3°.
· What will be the CA if GFRP blade will be coated with PDMS without nanomaterials?
· It is well known that PDMS is a hydrophobic materials with CA>100 and the authors do not discuss nothing about this important property.
· By inserted MoS2/ZnO or MoS2 nano materials in PDMS the properties of the resulted material depend in a great measure of the characteristics of PDMS.
· The authors do not present the hydrophobic properties of the blade coated with only PDMS and then to compare the properties of the materials with PDMS/MoS2/ZnO and PDMS/MoS2.
· PDMS has around 37-38% silicone and the XPS was used to determine the surface chemical composition. The authors evidenced the presence of Mo, O, S and Zn, but nothing about Silicone.
· How much is the rugosity of the uncoated blade and to the coated blade surface with MoS2/ZnO and MoS2, respectively?
· At lines 261-262, the authors wrote: „This change can be attributed to the difference in because the thermal conductivity between the ice layer the GFRP blade (2.2 W/(m·K) vs. 0.42 W/(m·K))”. What means?
· At lines 301-304: “……the MoS2 nanomaterial is a hydrophobic coating, and the water droplets flow downward under the combined action of airflow and gravity, but do not reach the superhydrophobic state”. Which are the optimization conditions to realize the “superhydrophobic state”?
Author Response
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Reviewer 2 Report
The paper presents detailed studies of MoS2/ZnO coatings to prevent the formation of ice structures on the surface of wind turbine blades. The authors describe in detail the procedure for preparing the coatings, as well as the results of various tests, such as determination of hydrophobicity, measurement of ice adhesion strength, and chemical stability of the coatings. However, for the effective long-term operation of coatings, the following factors are of significant importance. These are the mechanical strength of the coating and the adhesion strength of the coating to the turbine blade material. During operation, the coating of turbine blades can be under the influence of 1) different mechanical effects, and 2) stress-strain effects due to changes in the linear dimensions of the blade under temperature variations. If the coating is easy torn, there is no meaning to use it in practice to protect the blades. It is desired that the authors also discuss in the paper issues related to the mechanical strength and stability of the tested coatings.
Author Response
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Reviewer 3 Report
Dear authors, see the attached file
Comments for author File: Comments.docx
Author Response
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Reviewer 4 Report
This research dealt with anti-icing property of MoS2/ZnO nanomaterials on the wind mill blades. It is a useful research for the applications in the cold regions. The over view of the results shows that the sample coated with ZnO only is missing in terms of characterization and performance. There are general terms without specific values such as surface roughness, surface area etc need to be mentioned. The manuscript need to be modified majorly based on the below comments.
1.Intro, line 54: The info about graphene is not required for this research. Also detail more about MoS2 for the present similar research done by others. Why MoS2 and ZnO combination was chosen for this research. For the super hydrophobic coatings which exhibit excellent property whether MoS2 or ZnO?.
2.For real time application, how come the hydrothermal method would help coating of nanomaterials on the large blades?.
3.Line 70: contact angle (CA), line 201: mention the full form of SA.
4.What is the purpose of adding Lithium hydroxide for preparing ZnO?. Usually simple alkali such as KOH, NaOH are used. Also mention the concentration of solutions in Molarity.
5.When coating the NMs solution with spray gun whether the coating was uniform all over the surface and exhibit uniform thickness?.
6.Sec. 3.2: mention the analysis conditions such as applied energy, distance etc in each instrumentation.
7.Fig. 3 caption: not XPS image, it is XPS spectra.
8.Fig.8: Icing wind tunnel test situation.
9.Wherever possible, provide the results of only ZnO coatings in FESEM, anti-icing properties etc.
10.Line 193: what is the specific surface area of the prepared materials?.Also, what do you mean by hilly nano-rough structure?; line 218: mention the surface roughess values measured using AFM. If you did not analyse, you need to modify the statements.
11. Fig. 6: include the error bars.
Author Response
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Round 2
Reviewer 1 Report
The authors gave detailed comments and solved the arisen questions.
Some minor observation:
At question: PDMS has around 37-38% silicone and the XPS was used to determine the surface chemical composition. The authors evidenced the presence of Mo, O, S and Zn, but nothing about Silicone.
and the response was: "The author did not analyze pdms in the xps analysis, because pdms only act as adhesives in hydrophobic coatings and are not the main research object of this paper. XPS analysis was conducted to demonstrate successful synthesis of MoS2 and MoS2/ZnO."
The response of the authors is not real because the PDMS is not adhesive and by XPS it is analyze the surface composition. In the manuscript the authors wrote (lines110-113):
“….. 1 g of the PDMS mixture was added to 50 mL n-hexane while stirring at room temperature for 10 min. An equivalent mass of MoS2/ZnO nanomaterials was added and stirred for 30 min to form a uniform mixed suspension, which was then evenly sprayed ……..” Thus, PDMS is an equivalent mass of MoS2/ZnO !
XPS analysis was used to see the surface composition not the synthesis of MoS2 and MoS2/ZnO and usually, XPS analysis is used to quantify elements present on the surface, their chemical states, and relative concentrations.
If the authors will analyze the relative concentration of the elements of the surface the Silicone will be present in a concentration of some level.
Author Response
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Reviewer 3 Report
The manuscript was revised as requested and can be published in the present form
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Reviewer 4 Report
The revised version is not carefully addressed the comments raised by this reviewer. For example, comments 2 and 9 were answered with totally irrelevant answers. Thus it cannot be accepted in the present form. The editor is requested to take the final decision of the manuscript after the revision.
Author Response
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