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<p>Silicon carbide (SiC) is a promising ceramic for high-temperature applications but suffers from poor sinterability and brittleness. In this study, SiC/Al<sub>2</sub>O<sub>3</sub> composites were reinforced with 5 wt.%, 10 wt.%, and 15 wt.% Si<sub>3</sub>N<sub>4</sub>, SiAlON, and AlN, and fabricated by pressureless sintering at 1600°C, 1700°C, and 1800°C. The effects of additive type and content on densification, hardness, fracture toughness, flexural strength, and microstructure were systematically evaluated. Pure SiC exhibited limited performance, with relative density below 90% at 1600°C and flexural strength of only 360.2 MPa at 1800°C. The C-Al<sub>2</sub>O<sub>3</sub>(5)-SiAlON(5) sample achieved the highest densification and hardness at 1700°C. The C-Al<sub>2</sub>O<sub>3</sub>(5)-AlN(15) composite showed superior high-temperature performance, with a flexural strength of 550.9 MPa and fracture toughness of 4.68 MPa m<sup>1/2</sup> at 1800°C. Si<sub>3</sub>N<sub>4</sub> composites provided steady but moderate improvements, achieving a flexural strength of 455.1 MPa at 15 wt.%. SEM analysis confirmed that SiAlON and AlN refined the microstructure and promoted crack-deflection mechanisms. These findings highlight that additive type and concentration critically control the balance between densification and mechanical performance, with SiAlON most effective at intermediate temperatures and AlN at high temperatures.</p>

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Influence of Pressureless Sintering on the Densification Behavior and Mechanical Characteristics of Silicon Carbide Composites Containing Oxynitride Additives

  • 期刊论文

  • 发表日期：

    2026年6月26日

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  • Ibtihal Najm Abdullah,
  • Mahdi Ghassemi Kakroudi,
  • Mohammad Rezvani

摘要

Silicon carbide (SiC) is a promising ceramic for high-temperature applications but suffers from poor sinterability and brittleness. In this study, SiC/Al2O3 composites were reinforced with 5 wt.%, 10 wt.%, and 15 wt.% Si3N4, SiAlON, and AlN, and fabricated by pressureless sintering at 1600°C, 1700°C, and 1800°C. The effects of additive type and content on densification, hardness, fracture toughness, flexural strength, and microstructure were systematically evaluated. Pure SiC exhibited limited performance, with relative density below 90% at 1600°C and flexural strength of only 360.2 MPa at 1800°C. The C-Al2O3(5)-SiAlON(5) sample achieved the highest densification and hardness at 1700°C. The C-Al2O3(5)-AlN(15) composite showed superior high-temperature performance, with a flexural strength of 550.9 MPa and fracture toughness of 4.68 MPa m1/2 at 1800°C. Si3N4 composites provided steady but moderate improvements, achieving a flexural strength of 455.1 MPa at 15 wt.%. SEM analysis confirmed that SiAlON and AlN refined the microstructure and promoted crack-deflection mechanisms. These findings highlight that additive type and concentration critically control the balance between densification and mechanical performance, with SiAlON most effective at intermediate temperatures and AlN at high temperatures.