Engineered Nanomaterials for Aviation Industry in COVID-19 Context: A Time-Sensitive Review
Round 1
Reviewer 1 Report
The paper reviews topics related to high-performance nanomaterials for aviation industry with respect to airframe structure, nanocoatings and electro-communication systems. The topic falls within the scope of the journal and might be of interest for its readers. My comments are shown below:
- Figures 3 and 4 present very basic information on carbon nanotube and nanocalys, respectively and can be removed.
- In table 2 information related to sensors is only partially related to aviation industry, while information related to biomedical application is not related to aviation industry at all.
- Only a limited part of the paper focuses on COVID-19 and only a very small number of papers are directly related to COVID-19. In that sense I do not find the title particularly matching the content of the manuscript.
- The authors should substantially reorganise and refocus their manuscript on recent advances in nanomaterials for aviation industry.
- Emphasis should be given to the underlying mechanisms of action.
- An extensive critical discussion on the advantages ad limitations of nanomaterials in the aviation industry would be welcome.
Author Response
The paper reviews topics related to high-performance nanomaterials for aviation industry with respect to airframe structure, nanocoatings and electro-communication systems. The topic falls within the scope of the journal and might be of interest for its readers. My comments are shown below:
Comment 1:
Figures 3 and 4 present very basic information on carbon nanotube and nanocalys, respectively and can be removed.
Response:
The reviewer’s suggestion has been acknowledged and the Fig 3 and Fig 4 are removed from the manuscript. The next numbering of the Figures has been changed accordingly in the caption and texts.
Comment 2:
In table 2 information related to sensors is only partially related to aviation industry, while information related to biomedical application is not related to aviation industry at all.
Response:
It is noted that Table 2 provides an overview of the previous research conducted in carbon nanotubes (CNTs) based polymer composites, while applications of nanomaterials to aviation industry are presented in Table 1.
Comment 3:
Only a limited part of the paper focuses on COVID-19 and only a very small number of papers are directly related to COVID-19. In that sense I do not find the title particularly matching the content of the manuscript.
Response:
Authors agree with the reviewer that only a handful of research work is available that connects COVID-19 with aviation industry. This exactly is the narrative of current paper that aims to educate the research community of new possible area of antiviral coatings to the interior of airplanes which may help to combat the current pandemic and also the future diseases.
Reviewer 2 Report
The authors have written the time-sensitive review of engineered nanomaterials to combat the effect of COVID-19 which should be interested for the upcoming research projects. The expectation was very high but it seems that this manuscript summarizes several nanomaterials and conclude that the sustain-able and robust research is required to develop antiviral nanomaterials and coatings to protect the airplanes' interior and to safeguard the passenger's trust. To me, an important question raised what about the safety of nanoparticles to the passengers ? It is known that the nanoparticles are not biocompatible. After careful reading, the question is still unanswered: what should we do to combat virus? Therefore, this manuscript is not suitable for the publication in MDPI Materials.
Author Response
Comment 4:
The authors should substantially reorganise and refocus their manuscript on recent advances in nanomaterials for aviation industry.
Response:
Authors would like to thank this reviewer for highlighting the need for further strengthening the focus on nanomaterials in aviation industry. As such, further revision has been made in this revised manuscript. In particular, the following sections have been extended by:
Section 3 (ENMs Properties and Applications):
“As compared to counterparts with microscale or larger grain structure, they have substantially better properties. This is especially evident for properties critical in aerospace applications, such as yield stress, structural rigidity, resistance to corrosion, and a low density to allow for significant structural weight reductions. Moreover, nanostructured metals have been shown to not only have improved properties and can be designed to have properties that are uncharacteristic for traditionally sized materials. A nanostructured titanium-nickel alloy, for example, exhibits superelasticity and high yield strength.
Magnesium alloys are much lighter than steel or aluminium; however, due to the high reactivity of magnesium, they are compromised due to their sensitivity to corrosion. A surface coating is the most widely used solution for the control of corrosion. However, manufacturers are well documented to be carcinogenic in their favoured chromium coatings. Silicon and boron oxides, as well as cobalt-phosphorous nanocrystals, are nanomaterials used as anticorrosion coatings as an alternative to chrome. Even so, an appropriate coating for aluminium, which is commonly used in aircraft structures due to its comparable performance to chromium, has yet to be developed, making it one of the sector's most significant needs. Aluminium’s heterogeneous surface makes it particularly susceptible to corrosion, which is accelerated by the presence of alloying elements and precipitates. Recent studies have demonstrated magnesium nanocomposites as an interesting candidate, though this research is still in its early stages, necessitating more thorough investigation. Nanocoatings are applied to mechanical components that are subjected to high temperatures and friction wear, such as turbine blades, in addition to preventing chemical corrosion. These tribological coatings can reduce friction coefficients and improve wear resistance, resulting in increased engine efficiency and reduced fuel consumption. As a potential friction modifying agent including carbides, nitrides, metals, and various ceramics, many nanostructure and nanoscale coating materials were proposed.”
Comment 5:
Emphasis should be given to the underlying mechanisms of action.
Response:
To address this comment, authors have now extended the section 5:
“The gaseous phase methods prevent the severity of nanomaterial organic impurity compared to the liquid phase processes, but they require the use of complex, low efficiency and high costs vacuum devices. The CVD method can produce ultra-fine materials of size less than 1μm utilizing gaseous phase chemical reaction. Nanomaterials from 10 to 100 nm can be generated by careful reaction control. The CVD process involves heating source such as a chemical fire, a plasma process, laser, or an electric furnace to perform the high-temperature chemical reaction. In the production of metal oxide or other types of materials, the thermal decomposition method was particularly useful as an industrial preferable synthesis method. A typical example of a liquid / liquid method is the chemical reduction of the metal ions whose primary benefit is the easy manufacturing of materials of various forms, such as nanorods, nanofilms and nanofillers. By changing the reducing agent, the dispersing agent, the reaction temperature and time it is possible to alter the shape and the size of the nanomaterials. It reduces the metal ions to their zero oxidation levels through chemical reduction. The method uses uncomplicated tools or instruments and can produce large amounts of nanomaterials for a limited period of time at low cost. Metal oxide nanomaterials were manufactured by the sole-gel process extensively. The hydrolysis, accompanied by polycondensation to a gel, converts a solution of a metal oxide into a sol. The wet process ensures that the nanomaterials are dispersed in comparison with the dry techniques [88-89].”
Comment 6:
An extensive critical discussion on the advantages and limitations of nanomaterials in the aviation industry would be welcome.
Response:
Authors have now added a new section ‘Advantages and Limitations of ENMs in Aviation’ in this revised paper.
Section 6 (Advantages and Limitations of ENMs in Aviation)
“ENMs promises the development of multifunctional materials which will help construct and keep aircraft, spacecraft and ships lighted, safer, smarter, and more effective. ENMs also enable many ways of improving transport infrastructure. The following are few worth mentioning Advantages and Limitations of ENMs in Aviation:
- As discussed above in the paper that the ENMs include structural parts of polymers nanocomposites; extreme powered rechargeable batteries, thermoelectrical materials for control of temperature; lower rolling tires; high efficacy and cost-effective sensors and electronics. In terms of improvement in high-performance, resilience and durability of aviation infrastructure ENMs made of aluminium, steel, copper, silicon and respective recycled formulations offers a great promise [91, 7-12].
- Another common issue in Aerospace vehicles is the surface deterioration of coatings because they are exposed to moisture, sunlight and oxygen. By adding different ENMs, the surface degradation can be reduced while retaining the necessary properties of the layer. With several wall-mounted CNT, TiO2, SiO2 ENMs and graphene, surface cracks decrease, UV degradation decreases and increases its lifespan. Inclusion of nanoclay to aircraft paints provides high fire retardant and also enables scratch resistant properties [91, 7-11].
- Aircraft engines are rendered excellent by including nanoclay and ZrO ENMs in the composite associated with Y2O3. The coating with nanofilms of engine parts facilitates self-cleaning and reduces friction. Comprehensive readings of different pressure and temperature are provided by Nanosensors and NEMS [91, 7].
- For the protection of critical aircraft components from electromagnetics, nanomaterials like single walled CNTs can be used.”
Limitations
- Although there are numerous advantages to nanocoatings compared to traditional coatings, some issues require further development. Main problems in nanocoatings are nanoparticles scattering and stability, pigments can lose color and ultra-fine particle hardness [91].”
Reviewer #2
The authors have written the time-sensitive review of engineered nanomaterials to combat the effect of COVID-19 which should be interested for the upcoming research projects. The expectation was very high, but it seems that this manuscript summarizes several nanomaterials and concludes that the sustain-able and robust research is required to develop antiviral nanomaterials and coatings to protect the airplanes' interior and to safeguard the passenger's trust. To me, an important question raised what about the safety of nanoparticles to the passengers? It is known that the nanoparticles are not biocompatible. After careful reading, the question is still unanswered: what should we do to combat virus? Therefore, this manuscript is not suitable for the publication in MDPI Materials.
Response:
Authors would like to thank this reviewer for bringing this insight into the context. It is to be noted that:
- Yes, the nanomaterials are not biocompatible! The focus of this review article is how the nanomaterials, when processed and applied through associated technologies, a) have enhanced properties; b) have potential to combat the COVID-19 interior to aviation.
- The way the information is presented in this paper is: first, the evidence of ENMs and improvement of properties was discussed; second, the ongoing research in further enhancing surface properties of aviation related components was thoroughly analysed; and finally, the potential of ENMs in tackling COVID-19, which is a time-sensitive research topic, was emphasized.
- Since the nanoparticles will not be exposed to surface without embodying them in a deposition technology, therefore the associated biocompatibility was not the focus of this paper.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The manuscript entitled "Engineered nanomaterials for aviation industry in COVID-19 context: a time-sensitive review" by Sunil et al presented a good information regarding the importance of aviation industry during COVID-19. Overall article is well defined and organized. Therefore, I have no further comments for improvements except below.
As article has been divided in several sections, if possible combine few parts and make the article little adequate for final publication.
Author Response
The manuscript entitled "Engineered nanomaterials for aviation industry in COVID-19 context: a time-sensitive review" by Sunil et al presented a good information regarding the importance of aviation industry during COVID-19. Overall article is well defined and organized. Therefore, I have no further comments for improvements except below.
As article has been divided in several sections, if possible, combine few parts and make the article little adequate for final publication.
Response:
Authors thank the reviewer for acknowledging the work presented in this manuscript. Authors have now reorganised the manuscript and have implemented the reviewer’s comments by omitting subsection numbering 3.2 from the manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I am not convinced that the title reflects the content of the manuscript, but other than that I am satisfied with the revisions.
Reviewer 2 Report
The review is improved based on reviewers comments, it is now clear what the aim of goal is, this manuscript is suitable for publication but I have doubt about the title of this manuscript. So the authors are advised to change the title
