Enhancing Structural, Mechanical, and Radiation-Shielding Properties of Al-B₄C Hybrid Composites

Comments 1: [In this manuscript, the author presented the microstructural and mechanical features of B4C/Al composites doping with Sm2O3. Notable improvements on relative density, hardness and wear resistance were achieved with promoting the volume fraction of Sm2O3. Shielding properties of neutron and gamma-ray were also discussed with Monte Carlo simulations. Sm2O3 was considered as a strong binder with which the porosity was effectively reduced. The results and conclusions are meaningful for designing of shielding materials and enhancing properties of Al matrix composites.

This is a well-organized manuscript that only needs a few minor revisions prior to publication. For instance:

The mechanisms through which Sm2O3 addition reduces porosity should be thoroughly discussed - specifically why and how.]

Response 1: Thank you for your valuable observation. In response, we have expanded the discussion of the mechanism by which Sm₂O₃ acts as a binder and reduces porosity. Specifically, we explained that due to its good distribution and small particle size, Sm₂O₃ can fill interstitial voids in the Al-B₄C matrix, contributing to a more compact microstructure. Additionally, Sm₂O₃ exhibits better interfacial compatibility with Al compared to B₄C, which improves particle bonding and reduces void formation during sintering.

[Revised text location: Page 8, Paragraph 2, Lines 270-288.]

Comments 2: [A clear determination is needed regarding whether enhanced shielding properties are primarily attributable to reduced porosity or the Sm2O3 addition itself.]

Response 2: Thank you for this insightful comment. To address this point, we clarified in the revised manuscript that while reduced porosity does contribute to improved attenuation behavior by limiting radiation scattering, the primary improvement in shielding is due to the intrinsic high cross-section of Sm₂O₃, especially for fast neutrons and gamma rays. Thus, the enhanced shielding performance is largely attributed to Sm₂O₃’s material properties rather than solely the densification effect.

[Revised text location: Pages 8 and 9, Paragraph 2, Lines 283-288.]

Comments 1: [The study on the properties of Al-BC hybrid composites presents interesting findings with potential applications in structural, mechanical, and radiation shielding materials. The experimental methodology, which involves high-energy ball milling and sintering, is well-documented, and the results indicate notable improvements in mechanical and shielding properties due to Sm₂O₃ reinforcement. However, there are several issues that need to be addressed before the manuscript can be recommended for acceptance:

The first paragraph of the introduction contains an excessive amount of background information. It is recommended that the focus be shifted more directly toward the research objectives, with irrelevant details trimmed to enhance clarity.

Response 1: Thank you for this valuable suggestion. We have revised the first paragraph of the introduction to make it more concise and directly relevant to the research objectives. Redundant or overly general background information was removed to enhance clarity and focus. The revised version now emphasizes the motivation behind using Sm₂O₃ in Al-B₄C composites and its relation to sustainability and shielding performance. [Changes made in the manuscript: Introduction section, Page 1, Paragraph 1]

Comments 2: [In the experimental section (lines 112–113 and 143–146), additional details regarding the key parameters for the XRD measurements (e.g., scanning step, voltage, current) should be provided. Furthermore, the exact conditions and setup for the electrochemical testing should be clearly specified.]

Response 2: Thank you for this helpful remark. We have expanded the experimental section by including the specific parameters used in the XRD measurements, such as the scan range, step size, voltage, and current. Additionally, the setup conditions for the electrochemical corrosion tests have been clarified, including the scan rate, reference and counter electrodes, and test duration. [Changes made in the manuscript: Page 4, Paragraphs 2 and 3, lines 111-120 and 139-150 of the Experimental Section.]

Comments 3: [In Table 3, the sixth column (Icorr) currently displays inconsistent significant figures. This column should be revised to ensure a consistent and appropriate number of decimal places.]

Response 3: Thank you for noting this inconsistency. The I_corr values in Table 3 have been revised to display uniform significant figures, ensuring consistency across the dataset.

[Change applied: Table 3, Section 3.4, Page 15.]

Additionally, as Reviewer 3 suggested that this table may be redundant since the same data is presented in Figure 12b, so we have removed Table 3 to reduce redundancy and improve clarity.

Comments 4: [The conclusion section is overly descriptive of the characterization methods used. It is suggested that this section be streamlined to focus only on the primary findings and broader implications of the study, avoiding unnecessary repetition of the techniques employed.]

Response 4: Thank you for this constructive feedback. We have revised the conclusion section to make it more concise, focusing solely on the key findings and the broader implications of the study. Descriptions of characterization methods have been removed to avoid redundancy.

[Change applied: Conclusion Section, Page 18.]

Comments 5: [While the results on neutron and gamma-ray attenuation are promising, a brief explanation of the physical mechanisms behind the observed changes due to Sm₂O₃ addition would strengthen the scientific contribution of this work.]

Response 5: We appreciate this insightful comment. We have expanded the discussion to include a more detailed explanation of the physical mechanisms underlying the observed improvements in radiation shielding. Specifically, we clarified that the improved gamma-ray and fast neutron attenuation is attributed to Sm₂O₃'s high atomic number (Z = 62) and high density, which enhance interaction probabilities via Compton scattering and neutron inelastic scattering. Meanwhile, a partial decrease in thermal neutron shielding is due to the reduced boron content, as boron-10 is the primary element responsible for thermal neutron absorption.

[Change applied: Section 3.5, Page 17, lines 442-454.]

Comments 1: [The disadvantages of the work include a huge imbalance between text and graphic information. The number of figures (about 15) and the number of panels in the complex figures exceeds all accepted standards. The abundance of drawings and panels with visual information makes this work very difficult to read and blurry. It is recommended to reduce the number of figures by half, and the number of panels in complex figures by 2-3 times.]

Response 1: Thank you for pointing this out. We fully agree with this observation. Accordingly, we have reduced the total number of figures from 15 to 9 and consolidated several individual images into composite figures. The number of panels in each figure has also been significantly reduced for clarity. The revised figures are listed below:

ü  Figures 4-7 have been merged, keeping only representative images from None, 5Sm₂O₃, and 9Sm₂O₃ samples.

ü  Figures 9, 10, 12-15 (histogram data) were grouped into two comprehensive plots.

ü  Figure 8 was completely removed for clarity and redundancy.

ü  Figure 11 was trimmed to include only three representative samples: 0, 3, and 9% Sm₂O₃.

ü  These changes improve readability and focus the visual data on the most critical results.

[Changes made in revised Figures 4-9, Sections 3.1 to 3.5]

Comments 2: [There is no need to provide data for composites of all compositions; it is sufficient to provide data for composites with the highest or average contents of samarium oxide. This applies to figures 4, 5, 6 and 7.]

Response 2: We appreciate this constructive suggestion. In line with your recommendation, we revised Figures 4, 5, 6, and 7 to present data for only three representative compositions: 0% (None), 5% Sm₂O₃ (midpoint), and 9% Sm₂O₃ (maximum). This adjustment improves the overall clarity and streamlines the presentation without compromising the scientific content.

[Changes made in Figures 4-7, Sections 3.1 to 3.3.]

Comments 3: [There is also no need to provide distribution maps of all elements (Al, B, C, Sm, O) in the composites. It is possible to limit ourselves to the maps of only two elements critical for the analysis or to show only three panels in the figures: SEM, Al + B + C together, SmL.]

Response 3: Thank you for this helpful note. We have revised the EDX mapping figures accordingly. Now, only three panels are presented: (1) SEM image, (2) combined map of Al + B + C, and (3) Sm distribution. These revisions reduce visual overload and focus the discussion on key compositional elements critical to the interpretation of results.

[Changes made in Figure 5, Section 3.1]

Comments 4: [All figures with histograms (Figures 9, 10, 12-15) should be combined into complex 1-2 figures.]

Response 4: We appreciate this recommendation. All histogram-type graphs have been integrated into two composite figures to minimize space and improve clarity. These include gamma and neutron shielding metrics (Figure 9) and mechanical performance data.

[Changes made in Figures 6 and 9, Sections 3.3 and 3.5.]

Comments 5: [Figure 11 should contain only 3 panels for samples: zero Sm2O3, 3Sm2O3, 9Sm2O3.]

Response 5: Agreed. We revised Figure 11 to include only three panels corresponding to 0, 3, and 9% Sm₂O₃ samples, as suggested.

[Changes made in revised Figure 7, Section 3.3]

Comments 6: [Figure 12a should be deleted as not necessary for this work taking into account its title. Table 3 should be deleted from section 3.4 because similar information contains in Figure 12b.]

Response 6: Thank you for your observation. Table 3 has been removed from the manuscript. The information they provided was either repetitive or not critical to the central findings.

[Changes made in Section 3.4, and removed elements are reflected in the updated table]

Comments 7: [All artistic representations of elements and devices in Figures 1 and 2 must be removed. The drawing must be presented as a block diagram without artistic elements.]

Response 7: We completely agree. Figures 1 and 2 have been redesigned using academic black-and-white block diagrams with no artistic icons or illustrations. This ensures clarity and complies with the journal’s graphical standards.

[Changes made in revised Figures 1 and 2.]

Comments 8: [Figure 8 is difficult to read, it is unclear what individual morphological structures depict on the resulting composite image. There are no inscriptions. The bonding mechanism between different particles is also not clear.]

Response 8: Thank you for your comment. To avoid confusion and improve overall readability, Figure 8 has been removed. Additionally, a more detailed explanation of particle bonding and microstructural improvements was integrated into the discussion section to ensure clarity.

[Figure 8 removed, revisions in Section 3.1 and 3.2.]

Comments 9: [Reading the article I realized that experiments with penetrating radiation passing through composites were not done, and instead everything was limited to Monte Carlo simulations. If so, then such simulations are not very interesting in the context of studying the realistic mechanical and structural properties of composites.]

Response 9: Thank you for this critical insight. We clarified in the manuscript that the radiation shielding results were derived using MCNP6.2 Monte Carlo simulations and that these simulations served to complement the experimental evaluations. To ensure transparency and properly set expectations, we revised the Materials and Methods section to indicate that no experimental radiation transmission tests were conducted explicitly. Additionally, we revised the relevant part of the Discussion (Section 3.5) to emphasize that the shielding performance interpretation is based solely on simulation results. This change provides readers with a more accurate understanding of the methodology and scope of our conclusions.

[Changes made in: Materials and Methods, Page 5, Lines 194-199; Discussion Section 3.5, Page 18, Lines 461–463.]

Comments 10: [Each paragraph of conclusions should not simply list what was done or measured in the article, but articulate what new unique results were obtained during this study. At the same time, there is no need to put too much emphasis on the data of mathematical modeling and calculations. The conclusions and the abstract to the article should be rewritten.]

Response 10: Thank you very much for this important observation. Both the Abstract and Conclusion sections were rewritten to clearly emphasize the novel outcomes of the study, including (i) the dual functional improvement from Sm₂O₃ reinforcement in terms of mechanical and shielding properties, (ii) the microstructural enhancement and porosity reduction revealed via SEM-EDX, and (iii) the observed trade-offs between thermal and fast neutron shielding linked to composition. We have significantly reduced emphasis on simulation and focused more on experimentally observed phenomena.

[Changes made in: Abstract section and Conclusions (Section 4), Page 18, Lines 461–491.]