Additive Manufacturing of Layered Nb-Al2O3 Composite Granules Based on Paste Extrusion
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsQuestion 1 In the introduction, the author explicitly states that 'producing stable conductors' is the main objective of this study. However, in the results and discussion sections of the paper, no experimental data on conductivity or resistivity are provided. The discussion section even clearly points out that 'conductivity was not achieved.'
Question 2 The author provides a very detailed characterization of the rheological properties (yield stress, thixotropy, etc.) (Figures 4 and 5), and based on this, chose a resting time of 2 days for printing. However, there is insufficient analysis of the correlation between these extensive rheological data and the macroscopic quality of the final printed samples.
Question 3 Regarding the sufficiency of evidence for the key conclusion that the layered structure inhibits Nb diffusion, this conclusion is one of the highlights of the paper, but relying solely on qualitative observations from SEM images makes the evidence appear weak. To strongly support the conclusion of 'diffusion inhibition,' more direct evidence of elemental distribution is needed.
Question 4 Regarding the mechanistic explanation of thermal shock performance, the author observed that after the third thermal shock, the elastic modulus tends to stabilize and attributed this to the formation of microcracks. Has there been any quantitative analysis of the microstructure of the samples after thermal shock (such as crack distribution, length, and orientation)? Has consideration been given to further optimizing thermal shock performance through controlling pore distribution or designing layered structures?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript presents an interesting and relevant contribution to the field of multimaterial paste extrusion for refractory composites, and the experimental programme is comprehensive. Nonetheless, the paper requires substantial revision to enhance clarity, conciseness, and overall structure. The introduction should conclude with a clear statement of the research gap, the underlying hypothesis, and the specific objectives of the work, as these elements are currently implicit rather than explicitly defined.
The Materials and Methods section would benefit from the inclusion of a schematic overview of the experimental workflow, outlining the sequence from mixing and printing to sintering, crushing, and characterization. Such a diagram would help the reader grasp the methodological logic more efficiently. In the Results section, the presentation is excessively dense. The use of summary tables for rheological parameters and printability metrics would improve readability, and figure captions should be revised to highlight the principal observations rather than merely describing the images.
The Discussion does not yet establish a sufficiently strong connection between the reported findings and potential industrial applications. A more explicit consideration of the applicability of the method, its limitations, and possible avenues for future development would substantially strengthen this section. The Conclusion is overly detailed and repeats information provided earlier in the manuscript; it should be condensed into a concise set of core messages emphasising the novelty, practical implications, and key outcomes of the study.
Several typographical errors (e.g., “usally” instead of “usually”, “scallable” instead of “scalable”) require correction, and notation for strain and stress should be standardised throughout. Readability would also benefit from reducing sentence length in several sections. The manuscript would be further strengthened by the addition of a graphical abstract summarising the overall process and main findings, as well as a comparison table situating the proposed method relative to conventional casting approaches.
Author Response
Please see attached PDF file.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsRegarding the presented article, I have only the following questions:
1. Why was a detailed rheological analysis performed only for pure Alâ‚‚O₃ paste and not for the Nb–Alâ‚‚O₃ composite paste?
2. To what extent is it possible to transfer rheological conclusions from the Alâ‚‚O₃ system to the Nb–Alâ‚‚O₃ system with a metallic phase?
3. Why are direct measurements of electrical conductivity not presented in the article, when electrical functionality is one of the main motivational goals of the work?
4. How significant is the improvement in the homogeneity of the aggregate composition compared to casting-based Nb–Alâ‚‚O₃ materials, when phase segregation during grinding still persists?
5. Why were the mechanical and thermal shock properties not tested on the Nb–Alâ‚‚O₃ composite material itself?
6. Is there a quantitative evaluation of the degree of preservation of the layered architecture in individual granular fractions after grinding?
7. What is the practical impact of the detected phase segregation of fine fractions on the functional properties of subsequent cast composites?
Author Response
Please see attached PDF file.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have adequately addressed the reviewers’ suggestions, and the manuscript is now suitable for publication.
