Microstructure and Mechanical Properties of Unidirectional, Laminated Cf/SiC Composites with α-Al2O3 Nanoparticles as Filler

Abstract

The effects of an α-Al2O3 nanoparticle filler in the SiC matrix on the mechanical properties and failure mechanism of the unidirectional, laminated carbon fiber-reinforced SiC composites were investigated in this work. First, α-Al2O3 nanoparticles were added to the carbon fiber bundles using a slurry impregnation method, and then the Cf/SiC composite with an α-Al2O3 nanoparticle filler (Cf/SiC-Al2O3) was fabricated using a precursor infiltration and pyrolysis method. The microstructure of the Cf/SiC-Al2O3 composite showed chemical compatibility between the α-Al2O3 and the pyrolysis SiC. The Cf/SiC-Al2O3 composite with a low porosity of ~6.67% achieved a good flexural strength of 629.3 MPa and a good fracture toughness of 25.2 MPa·m1/2. The interlaminar shear strength of the Cf/SiC-Al2O3 composite was 11.7 MPa. The SiC-Al2O3 matrix also presented a considerable Young’s modulus of 138.2 ± 8.66 GPa and hardness of 10.3 ± 1.03 GPa. Further analysis indicated that the good mechanical properties with the addition of an α-Al2O3 filler were not only related to the dense matrix and the improvement of the mechanical properties of the matrix. They also originated from the thermal residual compressive stress in the SiC matrix close to the α-Al2O3 nanoparticles caused by the thermal expansion mismatch, which could reflect and close the cracks in the matrix. The findings of this study provide more methods for designing new composites exhibiting a good performance.

Lowering the synthesis temperature of α‐Al2O3 by increasing the content of pentacoordinate aluminum in the precursors

“…These attributes make it possible to produce ceramics with higher density, indicating substantial development potential. 10,11 However, the high activation energy barrier for the formation of α-Al 2 O 3 necessitates high calcination temperature often surpassing 1200 • C. Such elevated calcination temperature results in abnormal grain growth and significant powder aggregation, leading to an undesirable increase in α-Al 2 O 3 particle size and a pronounced loss of specific surface area. These challenges curtail the broader application of α-Al 2 O 3 .…”

“…The significance of α‐Al 2 O 3 is further underscored when it possesses a larger specific surface area and smaller particle size, leading to enhanced catalytic activity, improved hydrothermal stability, and higher fracture toughness. These attributes make it possible to produce ceramics with higher density, indicating substantial development potential 10,11 . However, the high activation energy barrier for the formation of α‐Al 2 O 3 necessitates high calcination temperature often surpassing 1200°C.…”