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Core‒Rim Structures and Hierarchical Phase Relationship for Hot-Pressed ZrB 2‒SiC‒MC (M=Nb, Hf, Ta, W) Ceramics

51 Pages Posted: 1 Apr 2019 First Look: Preprint

See all articles by Dong-Li Hu

Dong-Li Hu

Shanghai University - School of Material Science and Engineering; Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

Hui Gu

Shanghai University - School of Material Science and Engineering; Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

Ji Zou

Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

Qiang Zheng

Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

Guo-Jun Zhang

Donghua University - State Key Laboratory for Modification of Chemical Fibers and Polymer Materials; Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

Abstract

Core‒rim structure emerges as a common microstructural feature of hot-pressed ZrB2‒SiC‒MC (M=Nb, Hf, Ta and W) ceramics. A combination of X-ray diffraction and microscopic analyses reveal that it originates from the re-distribution of transition-metals into their bi-solubility in the primary phase, hence turning the core‒rim structures into an intra-phase relationship. Solution‒reprecipitation process rationalizes their formation via a transient liquid-phase of Zr‒M‒B‒C‒(O). It dictates the special transformation process by enabling an exchange of metal with cores to reach the lower solubility and a transition to grow rims into higher solubility, driven by an over-saturation of boron in the liquid. A third and even higher solubility in the minor ZrC phase finalizes the liquid-phase sintering process, leading to hierarchical phase relationship. We propose further a scheme of g-point to syndicate the bi-solubility as solidus and liquidus limits of metal in ZrB2 phase, hence to schematize the coordinated evolution of multiphase microstructures. The core/rim boundaries can strengthen the ceramics by storing and re-distributing strain energy within the grains, which leaves the microstructure‒property relationship to renew and further optimize for UHTC.

Keywords: ZrB2-Based Ceramics, Core‒Rim Structures, Hierarchical Phase Relationship, Solution‒Reprecipitation Process, High-Temperature Flexural Strength

Suggested Citation

Hu, Dong-Li and Gu, Hui and Zou, Ji and Zheng, Qiang and Zhang, Guo-Jun, Core‒Rim Structures and Hierarchical Phase Relationship for Hot-Pressed ZrB 2‒SiC‒MC (M=Nb, Hf, Ta, W) Ceramics (March 23, 2019). Available at SSRN: https://ssrn.com/abstract=3358890

Dong-Li Hu

Shanghai University - School of Material Science and Engineering

149 Yanchang Road
SHANGDA ROAD 99
Shanghai 200072, Shanghai 200444
China

Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

1295 Dingxi Road
Shanghai, 200050
China

Hui Gu (Contact Author)

Shanghai University - School of Material Science and Engineering ( email )

149 Yanchang Road
SHANGDA ROAD 99
Shanghai 200072, Shanghai 200444
China

Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure ( email )

1295 Dingxi Road
Shanghai, 200050
China

Ji Zou

Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

1295 Dingxi Road
Shanghai, 200050
China

Qiang Zheng

Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

1295 Dingxi Road
Shanghai, 200050
China

Guo-Jun Zhang

Donghua University - State Key Laboratory for Modification of Chemical Fibers and Polymer Materials

Shanghai
China

Chinese Academy of Sciences (CAS) - State Key Laboratory of High Performance Ceramics and Superfine Microstructure

1295 Dingxi Road
Shanghai, 200050
China

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