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<p>SiC/SiC composites were fabricated using the liquid silicon infiltration (LSI) process. The SiC fibers used were coated with h-BN/SiC/h-BN/SiC interfacial layer that has 4 layers of multi-coating structure. This study analyzed and evaluated the effects of interfacial coating thickness on the mechanical properties and microstructure of ceramic matrix composites (CMCs). The coating thicknesses applied were thin: 300&#xa0;nm and thick: 2&#xa0;μm, with a uniform layer coated using the low-pressure chemical vapor deposition (LPCVD) process. SEM and EDS analyses revealed that boron dissolved in the infiltrated Si from h-BN, damaging the coating layer at high temperature. Consequently, for specimens with thin coatings, the h-BN layer was entirely damaged, failing to protect the fibers and resulting in a decrease in mechanical properties. In contrast, thicker coatings sufficiently prevent the damage from the molten Si, protecting the fibers and inducing a pull-out morphology on the fracture surface, thereby exhibiting excellent flexural strength of 624&#xa0;MPa. Additionally, the thickness of the coating layer affected the fiber volume fraction of the CMCs, with an increase in coating thickness resulting in a decrease in fiber volume fraction from 50 to 30%. However, despite the decrease in volume fraction, the mechanical properties improved, which is contrary to the typical behavior of fiber-reinforced composites.</p>

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Study on the characteristics of SiC/SiC composites with h-BN fiber interface coating fabricated by liquid silicon infiltration process with various coating thickness

  • 期刊论文

  • 发表日期：

    2025年1月28日

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  • Seul Hee Lee,
  • Seyoung Kim,
  • In-sub Han,
  • Hyung Joon Bang,
  • Soo-Hyun Kim,
  • Young-Hoon Seong

摘要

SiC/SiC composites were fabricated using the liquid silicon infiltration (LSI) process. The SiC fibers used were coated with h-BN/SiC/h-BN/SiC interfacial layer that has 4 layers of multi-coating structure. This study analyzed and evaluated the effects of interfacial coating thickness on the mechanical properties and microstructure of ceramic matrix composites (CMCs). The coating thicknesses applied were thin: 300 nm and thick: 2 μm, with a uniform layer coated using the low-pressure chemical vapor deposition (LPCVD) process. SEM and EDS analyses revealed that boron dissolved in the infiltrated Si from h-BN, damaging the coating layer at high temperature. Consequently, for specimens with thin coatings, the h-BN layer was entirely damaged, failing to protect the fibers and resulting in a decrease in mechanical properties. In contrast, thicker coatings sufficiently prevent the damage from the molten Si, protecting the fibers and inducing a pull-out morphology on the fracture surface, thereby exhibiting excellent flexural strength of 624 MPa. Additionally, the thickness of the coating layer affected the fiber volume fraction of the CMCs, with an increase in coating thickness resulting in a decrease in fiber volume fraction from 50 to 30%. However, despite the decrease in volume fraction, the mechanical properties improved, which is contrary to the typical behavior of fiber-reinforced composites.