Study on Preparation and Flame-Retardant Mechanism of Cerium-Doped Mg-Al Hydrotalcite
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe paper is interesting and can be accepted after following MINOR contributions.
1- The introduction section can be extended, to do that look at: https://doi.org/10.1016/j.physb.2024.416732
2- For the deep interpretation of FT-IR look at https://doi.org/10.1016/j.physb.2024.416732
3- What specific hydrothermal conditions (temperature, duration, pH) were optimized to achieve the cerium-doped hydrotalcite structure?
4- At what doping level did cerium start to disrupt the hydrotalcite structure, and what could be the underlying mechanism? some explanation would be great.
5- Were any differences in the protective layer's composition observed with varying cerium doping levels?
Comments on the Quality of English LanguageThe language is good.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn this work, the authors reported the flame-retardant properties of epoxy (EP) composites with cerium-doped magnesium-aluminum hydrotalcite (MgAlCe-LDH). Layered structures of hydrotalcite improve the flame-retardant, smoke suppression properties by pyrolyzed water vapor and prevention of dripping. Suitable amount of intercalated cerium element catalyzes carbonization to form the carbon layer during surface combustion, isolating oxygen and heat penetration. The authors performed structural analyses of MgAlCe-LDH crystals, investigation of thermal properties of the hydrotalcites and their composites, spectral study of the gaseous products during thermal decomposition of composites. However, the lack of consistent evaluations using reference samples with excess cerium results in inadequate discussion of the negative effects of excess cerium. Some concerns ought to be given attention, as follows:
Comment 1:
To verify the description “the oxides formed by excess cerium and irregular sheets of hydrotalcite are agglomerated and deposited together” in Page 5 Line 173, I would recommend adding the SEM images of the MgAlCe-LDH with excess cerium (ex. C-7) to Figure 3. I would also like the authors to add the results of the composites with excess cerium to Table 7 and Figure 12 and 13 to clearly show the highest flame-retardant properties can be obtained from suitable amounts of cerium.
Comment 2:
While C-7 is employed as the comparison with excess cerium in the discussion of Figure 2 and 8-11, why C-8 is employed in Figure 2?
Comment 3:
In Table 5, the word “Carbon residue rate” is not suitable for the thermal degradation of inorganic materials (MgAl-LDH and MgAlCe-LDH) without epoxy resin.
Comment 4:
Despite the description “Observing the weight loss curve (Figure 8a), it can be seen that the composite material has three thermal weight loss stages.” in Page 10 Line 277, the thermal weight loss third stage can be divided into two stages (400-500 oC and after 550 oC). Figure 8a and 8b indicates that the small loss of the weight of C-5/EP after 550 oC allow the highest residual carbon rate of C-5/EP. I would like the authors to divide and discuss each thermal weight loss (400-500 oC and after 550 oC).
Comment 5:
Thermal decomposition (endothermic reaction) and combustion (exothermic reaction) is different. Only the peaks of endothermic reactions were observed in Figure 8c, indicating that the values in Figure 8b are residual carbon rate after the thermal decomposition rather than combustion. I am curious about whether C-5/EP still show the highest residual carbon rate (flame-retardant properties) after the combustion in Figure 11.
Comment 6:
The first appeared abbreviations should be defined. The author should define the “TNT” in Page 2 Line 69 and “LDH” in Page 2 Line 81.
If the authors have revised the paper according to the comments and answered my questions, I will support publication of the revised manuscript in this journal.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsIn the Author's Response, the authors responded appropriately to my Comments 1~4 and 6. However the authors said that they cannot understand Comment 5. I am sorry for confusing them． I would like to add the description to make the comment clear.
Comment 5
The terms of thermal decomposition and combustion have different meaning. Thermal decomposition is endothermic reaction to break the chemical bond by heat. Combustion is exothermic reaction to oxidize by oxygen. Only the peaks of endothermic reactions were observed in Figure 8c, indicating that the values in Figure 8b are residual carbon rate after the thermal decomposition rather than combustion. Therefore, Figure 8b indicates the high resistance to thermal decomposition of C-4/EP. To discuss the resistance to flame, I would like to know whether C-4/EP still show high residual carbon rate after combustion in the presence of oxygen.
If the authors have revised the paper according to the comments and answered my questions, I will support publication of the revised manuscript in this journal.
Author Response
Please see the attachmentAuthor Response File: Author Response.pdf
