Microstructural and polytype evolution of reaction–formed SiC derived from recycled Si scrap via inverse two–step hot–press sintering

초록

Reaction–formed SiC (RFSC) derived from recycled Si scrap offers a cost–effective route to SiC ceramics, yet improving fracture toughness without deteriorating thermal conductivity remains challenging. Here, an inverse two–step (ITS) hot–press sintering strategy was introduced to separate an (Formula presented) –related initial growth state from the final densification stage. With increasing T1 and T2, the phase constitution evolved progressively from 3C–SiC toward hexagonal (Formula presented) –SiC polytypes, accompanied by a marked morphology transition from equiaxed to elongated grains. Consequently, the ITS–processed specimens achieved an indentation fracture toughness of up to 6.81 (Formula presented) 0.16 MPa m1/2, nearly twice that of the single–step counterparts, with thermal conductivity in the range of 91.5–98.5 W m−1∙K−1. These results show that process–path design, without external (Formula presented) –SiC seeding, offers an effective route to induce microstructural and polytype evolution in RFSC for SiC–based components used in extreme–environment applications. © 2026 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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