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<p>Porous silicon nitride (Si<sub>3</sub>N<sub>4</sub>) ceramics have garnered significant attention in the aerospace industry due to their excellent mechanical strength, thermal insulation, and dielectric properties. In this study, highly porous and low-density <i>α</i>-Si<sub>3</sub>N<sub>4</sub> ceramics were successfully fabricated using a combination of the Isobam gel casting and adding pore-forming agent, with polymethyl methacrylate (PMMA) as the pore-forming agent. Debinding and low-temperature sintering were performed in air in a muffle furnace, without nitrogen protection, to retain the α-phase while limiting oxidation. The rheological behavior of the Si<sub>3</sub>N<sub>4</sub> slurry was systematically investigated under varying Isobam, solid content, and PMMA content conditions. Additionally, the effects of sintering temperature on phase composition and the influence of different PMMA contents on the mechanical, thermal, and dielectric properties were evaluated. The results demonstrated that with increasing PMMA content, the flexural strength, thermal conductivity, and dielectric constant of the porous ceramics exhibited a decreasing trend. After sintering at 1100&#xa0;°C, the Si<sub>3</sub>N<sub>4</sub> ceramics containing 30 wt% PMMA achieved a porosity of 70.71%, with a thermal conductivity as low as 0.15 W/(m·K), a dielectric constant of 2.24, and a dielectric loss tangent below 0.005. Despite the increase in porosity leading to a reduction in mechanical strength, the ceramics retained a flexural strength of 5.15&#xa0;MPa. The combination of the Isobam gel casting and adding pore-forming agent enabled the fabrication of α-Si<sub>3</sub>N<sub>4</sub> ceramics with outstanding thermal insulation and dielectric properties, highlighting their promising potential for aerospace applications.</p>

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Porous Si3N4 ceramics with high-performance thermal insulation and dielectric properties via gel casting and using pore-forming agents

  • 期刊论文

  • 发表日期：

    2026年1月29日

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  • Chen Zhang,
  • He Yang,
  • Wei Wu,
  • Xiaopei Wu,
  • Takashi Goto,
  • Jinyong Zhang,
  • Honglian Dai

摘要

Porous silicon nitride (Si3N4) ceramics have garnered significant attention in the aerospace industry due to their excellent mechanical strength, thermal insulation, and dielectric properties. In this study, highly porous and low-density α-Si3N4 ceramics were successfully fabricated using a combination of the Isobam gel casting and adding pore-forming agent, with polymethyl methacrylate (PMMA) as the pore-forming agent. Debinding and low-temperature sintering were performed in air in a muffle furnace, without nitrogen protection, to retain the α-phase while limiting oxidation. The rheological behavior of the Si3N4 slurry was systematically investigated under varying Isobam, solid content, and PMMA content conditions. Additionally, the effects of sintering temperature on phase composition and the influence of different PMMA contents on the mechanical, thermal, and dielectric properties were evaluated. The results demonstrated that with increasing PMMA content, the flexural strength, thermal conductivity, and dielectric constant of the porous ceramics exhibited a decreasing trend. After sintering at 1100 °C, the Si3N4 ceramics containing 30 wt% PMMA achieved a porosity of 70.71%, with a thermal conductivity as low as 0.15 W/(m·K), a dielectric constant of 2.24, and a dielectric loss tangent below 0.005. Despite the increase in porosity leading to a reduction in mechanical strength, the ceramics retained a flexural strength of 5.15 MPa. The combination of the Isobam gel casting and adding pore-forming agent enabled the fabrication of α-Si3N4 ceramics with outstanding thermal insulation and dielectric properties, highlighting their promising potential for aerospace applications.