Silica–Chitosan Composite Aerogels for Thermal Insulation and Adsorption
and Yizhao Li 1,2,*Round 1
Reviewer 1 Report
Cellulose fibers for making composite aerogels with SiO2 is not very expensive and quite comparable with chitosan. It is good attempt to make combined aerogels.
Preparation of aerogels is not very clearly described - in what media the reactions are performed?; what is the "low" temperature for freezing the samples?; why trimethyl chlorosilane and N,Ndimethylformamide is added?; why samples are degassed at very high temperature as 200C ?
All instrumentation must be described , similar as chemicals.
On Fig.1 is expecting to see images from CA, SA and SCA to compare. Usually SEM images are very bad to compare similar features.
On Page 4 line 125 and 126 is sentence " This structure is conducive to heat consumption in the process of heat transfer, which improves the heat insulation performance of the material" - what this means?
In several places would be better to have data collected into table - for example density and porosity data on Page 5; or thermal conductivity data on Page 7.
It is very hard to follow the thermal insulation tests - may-be visual schematic would be better. Information about these measurements and used equipment must be characterized better.
The hydrophobizity part is questinanable, because MTMS used in preparation of this aerogel is having CH3 group in structure and very often is used to increase hydrophobisity of silica aerogels ; this part needs better explanation, because there is no reaction of methylation during this aerogel preparation process.
How this calcination temperature at 800C characterises the thermal stability of material - from TGA is seen that it starts to degrade at around 250C?
What is "oil red reagent"? (Page 9- line 266 )
How is performed this cyclic adsorbance of the solven?
Author Response
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Reviewer 2 Report
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Reviewer 3 Report
The manuscript under review presents the preparation, characterization and insulation properties of silica-chitosan composite aerogels.
However, in my opinion the manuscript is not suitable for publication in this journal as there are no structure data nor even XRD to present the material is crystal.
Additionally, the work does not meet MDPY standards, as there are many mistakes in the experiments descriptions, interpretation of the results and even in methods chosen for the material characterization. The authors should generally rewrite the paper in order to emphasize the novelty in the idea, preparation and the material characterization and to support their issue for better insulation properties.
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Round 2
Reviewer 2 Report
Authors have made a great work and answered all the questions and suggestions. I recommend this paper for publication.
The only thing I would like to point out is that a deeper knowledge in the heat transfer mechanisms in aerogels could be adquired. I recommend these papers: https://doi.org/10.3390/gels9030220 and https://doi.org/10.3390/gels9030220
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Reviewer 3 Report
The manuscript is somehow improved, but not suitable for publication in this form, even more in this journal.
1. Correct the abstract, as the name of the instrument is nor suitable to place there, but the name of the method used. Specify in the abstract towards what is the high absorption capacity.
2. Lines 83- 86- not suitable for introduction.
3. 2.2 and 2.3 lines 106- 109 – repetition of the preparation.
4. Line-123- why 70K but not 77K what is the temperature of liquid nitrogen?
5. Barrett-Joyner-Halendar - Barrett-Joyner-Halenda is correct
6. Line- 147 small size of the prepared aerogels – small crystallites’ size, the aerogel cannot be small
7. Line 150 152 not photograph but micrograph
8. Lines 166-168 ”When the SiO2 content is low, the small amount of SiO2 particles cannot support the pore structure of SA- what this means as 2 not the concentration defines the pore structure” ? Incorrect interpretation
9. The accuracy of the BET specific surface area and pore volume cannot be as high with decimal digits for SSA and three decimal places for PV ( the apparatus shows its mathematical value, not the physical sense).
10. The types of adsorption isotherms and hysteresis loops according to IUPAC classification are not presented as these types define the pore structure of the materials
11. 226-237 incorrect
12. Fig 4 – mark the main commented bands on the spectra.
13. Correct the conclusion.
14. Bad English
Author Response
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Round 3
Reviewer 3 Report
The authors didn't understand some of my questions and recommendations, so didn't correct and improve these issues in the manuscript.
