Effect of Carbon Source on Microstructure and Mechanical Properties of Silicon Carbide Fabricated by Two-Step Reaction Sintering

Abstract

Reaction-bonded silicon carbide (RBSC) ceramics prepared by gel casting and two-step sintering were investigated. Three active carbon sources of petroleum coke (PC), carbon microspheres (MC), and nano-carbon black (CB) were compared in terms of slurry rheology, preform characteristics, sintered microstructure, and mechanical properties. With the active powders of PC and MC, the large particle size resulted in low density of the preform and un-uniform distribution of active carbon. CB addition yielded the highest slurry viscosity, the highest preform density, and the highest carbon density of 1.00 g·cm⁻³. The higher carbon density and more uniform active carbon translated into the highest SiC phase content and the lowest residual Si after sintering, attributed to the uniform active carbon distribution. A high-performance RBSC ceramic with a density of 3.12 g·cm⁻³, bending strength of 512 MPa, and Vickers hardness of 2386.6 HV was achieved. The corresponding phase composition was 94.28 vol.% SiC, only 2.22 vol.% residual Si, which is significantly lower than that of conventional RBSC. These results highlight the critical role of active carbon source selection in optimizing RBSC performance through microstructural refinement and residual phase control.

Keywords

Reaction bonded silicon carbide / Two-step sintering / Carbon sources / Bending strength

Statement of the Use of Generative AI and AI-Assisted Technologies in the Writing Process

During the preparation of this manuscript, the author(s) used DeepSeek to improve the language and readability of the text. All content was carefully reviewed and revised by the authors, who take full responsibility for the final content of the manuscript.

Author Contributions

Z.M.: Conceptualization, Methodology, Software, Data curation, Writing-original draft, Visualization, Investigation, Writing-review and editing. Y.L.: Funding acquisition, Writing-review and editing. X.P.: Validation, Resources. N.Z.: Investigation, Validation. J.Y.: Project administration, Funding acquisition, Supervision, Writing-review and editing. B.W.: Project administration, Funding acquisition, Supervision, Writing-review and editing. All authors have read and agreed to the published version of the manuscript.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Funding

This work was supported by the Shaanxi Innovation Capacity Support Program (Science and Technology Innovation Team, 2025RS-CXTD-027), Youth Innovation Team Project of Shaanxi Universities (23JP073), Key Research and Development Program of Shaanxi (No. 2024PT-ZCK-04), Shaanxi Province Qin Chuang Yuan “Scientist+Engineer” Team Construction Project (Nos. 2024QCY-KXJ-120, 2024QCY-KXJ-117).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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