Preparation and Energy Release Properties of nB@F2603@CL-20 Microspheres by Electrospray

Round 1

Reviewer 1 Report

Journal:  Metals

Title: Preparation and energy release properties of nB@F2603@CL-20 microspheres by electrospray

Manuscript ID: metals-1926302

In this work the authors prepared (nB@F2603@CL-20) microspheres with energy release properties that enhance ignition and combustion. Voltage and propulsion rate are principal parameters to control the sphericity of the formed structures. The microspheres’ physical and chemical composition were characterized using SEM, EDX and XRD. The thermal reaction properties were studied using TG-DSC-MS, oxygen bomb calorimeter, laser ignition and volume combustion cell test. Samples were tested using CO2 laser and a high-speed camera to study the ignition delay time and combustion time of the microspheres.  The hydrophobicity and corrosion resistance of the structures were also studied.  I found this work very interesting and worthy of publication.  However, the authors should address the following comments before this is published.

1. Figure 2 represents an SEM image of (a-b) nB@F2603 and (c-d) nB@CL-20 microspheres. On page 4 the authors claim that the structures have a monodisperse size distribution. Fig. 2a and Fig.2c is of low resolution and is hard to conclude that.  Additionally, it would be ideal if the authors could provide a histogram of the structures to support that or add higher resolution TEM of the structures.

2.  Can the authors elaborate on the selected voltage used for the electrospray?  

3. It would be interesting if the authors can add a TEM or SEM image of the starting materials (the boron nanoparticles as purchased). These TEM or SEM images can be added to Fig. 2 or Fig.3. 

4. The hydrophobicity of the synthesized materials is very interesting, and I understand that this can be a study by itself.  From the authors’ discussions it is not quite clear why it makes these materials hydrophobic. Is the “high energy” present in the microspheres or the “fibrous structure” formed or does if vary at the various applied voltages that create the hydrophobic property in this material?   It would also be interesting if the authors could indicate if the hydrophobicity of these materials are due to surface functional groups.

     X. Dai et al, Science Advances 2018;4:eaaq0919

S. Liu et al. Journal of Materials Chemistry A (2018) 28:13769-13777

D. Merchan-Breuer et al. Carbon Letters (2021) 31:389–406

 

5. Figure 9 shows phonographs/results of the ignition delay time and combustion time of the microspheres tested using CO2 laser and a high-speed camera. It compares n-B, nB@F2603, and nB@F2603@CL-20. The authors should be complemented for this very careful experimentation to obtain those results.  It is mentioned that this is conducted in a “constant volume combustion cell”, the authors should add a few additional lines regarding the combustion cell. For instance, it is a customized build or off the shelf device, etc.

Author Response

Thanks for your review. In response to your comments， we have made changes to the manuscript. Please find it in attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript reports on the preparation of nB@F2603@CL-20 microspheres with an average size of 9 mm by electrospray technique. Their combustion performance was studied by TG-DSC-MS, an oxygen bomb calorimeter, laser ignition, and a volume combustion cell test. The apparent activation energy of thermal decomposition was determined by the Flynn-Wall-Ozawa method. The stability in terms of hydrophobicity and corrosion resistance of the structure was also studied. The results are interesting and worthy a publication in Metals. A minor revision is required.

·         Was the composition of nB@F2603@CL-20 microspheres optimized? Why was “320 mg n-B, 40 mg CL-20, and 40 mg F2603” chosen for preparation?

·         Figures 4, 5(d), 6, 7, 8, and 10 are obviously low quality. Legends, labels, curves, etc. are very difficult if not impossible to see and read. They need to be improved. Larger scale markers and bolder squares and arrows should be added to the SEM figure.

·         Figure 2 (a) is not informative. Labeling XRD reflections of crystalline phases could improve the situation, or bar chart of the main XRD peaks for CL-20 phases may be added.

·         Do the combustion properties of CL-20 depend on its crystal form (e, b)?

·         Lines 204-205: “… maximum exothermic rate at 231.6°C. The DSC curves show that the maximum exothermic peak of CL-20 decomposition is at 237.3°C …” Other temperatures are indicated on Figure 6.

·         Lines 205-206: “…which is slightly lower than the peak temperature of pure CL-20.” References are required.

·         Caption of Figure 6: “(a) DSC, (b) TG and (c) DTG curves of n-B, nB@F2603 microspheres, nB@F2603@CL-20 223 microspheres, and F2603.” F2603 is not presented on figure 6.

·         Why Flynn-Wall-Ozawa’s method was chosen for obtaining the values of activation energies? Were the calculations performed by standard Kissinger method?

·         The citation for Figure 7 is absent from the text.

Author Response

Thank you for your comment. In response to your comments, we have made changes to the manuscript. Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Journal:  Metals

Title: Preparation and energy release properties of nB@F2603@CL-20 microspheres by electrospray

Manuscript ID: metals-1926302

 

It seems to me that the authors did not take the time or put enough effort to address my comments. The Authors should use the positive reviews from a reviewer to improve/enhance the quality of the manuscript.  For instance, “the authors claim that the structures have a monodisperse size distribution”; however, the added SEM images contradict that statement. To me, it seems that the structures have a polydisperse size distribution.  In Figure 4, one of the added TEM/images is out of focus. In their response to hydrophobicity comment, the Authors commented that “…the assembled composite microspheres have a certain hydrophobicity due to the formation of a special fibrous structure.”. No evidence (SEM/TEM, etc.) to support that statement is presented in revised version.

 

I leave to the discretion of the Editor to accept or reject this manuscript.

Author Response

Thanks for your review. In response to your comments, we have made changes  to the manuscript. Please find it in attachment.

Author Response File: Author Response.pdf