Material scientists develop porous Si₃N₄ ceramics with uniform, fine structures
phys.org
Tsinghua University Press
More information: Yuanyuan Liu et al, Synergistic promotion of dielectric and thermomechanical properties of porous Si3N4 ceramics by a dual-solvent template method, Journal of Advanced Ceramics (2024). DOI: 10.26599/JAC.2024.9220962
Provided by Tsinghua University Press
Citation: Material scientists develop porous Si₃N₄ ceramics with uniform, fine structures (2024, September 20) retrieved 21 September 2024 from https://phys.org/news/2024-09-material-scientists-porous-ceramics-uniform.html
Summary
Here is a summary of the key points from the research on porous Si3N4 ceramics:
- Researchers developed porous Si3N4 ceramics with uniform, fine structures using a dual-solvent templating and freeze-casting method.
- The method uses a mixture of tert-butyl alcohol and camphene as solvents/templates to precisely control pore size and structure.
- Key findings:
- 56% porosity achieved
- High mechanical properties: 95 MPa flexural strength, 132 MPa compressive strength
- Low thermal conductivity: 4.2 W·K-1·m-1
- Low and stable dielectric constant (~3.3) and loss (1.0-4.0 x 10-3) up to 1100°C
- As the ratio of camphene to tert-butyl alcohol increased:
- Pore structure changed from prismatic to spherical
- Pore size initially decreased then increased
- Optimal 1:2 ratio produced smallest, most uniform pores
- The uniform spherical pore structure improved mechanical properties while smaller pores reduced thermal conductivity.
- Rod-shaped Si3N4 grains facilitated crack deflection, enhancing toughness.
- The material shows promise as a high-temperature wave-transparent ceramic for aerospace applications like radomes and antenna windows.
- This method offers better control over microstructure compared to conventional techniques, allowing synergistic enhancement of dielectric and thermomechanical properties.
- Researchers developed porous Si3N4 ceramics with uniform, fine structures using a dual-solvent templating and freeze-casting method.
- The method uses a mixture of tert-butyl alcohol and camphene as solvents/templates to precisely control pore size and structure.
- Key findings:
- 56% porosity achieved
- High mechanical properties: 95 MPa flexural strength, 132 MPa compressive strength
- Low thermal conductivity: 4.2 W·K-1·m-1
- Low and stable dielectric constant (~3.3) and loss (1.0-4.0 x 10-3) up to 1100°C
- As the ratio of camphene to tert-butyl alcohol increased:
- Pore structure changed from prismatic to spherical
- Pore size initially decreased then increased
- Optimal 1:2 ratio produced smallest, most uniform pores
- The uniform spherical pore structure improved mechanical properties while smaller pores reduced thermal conductivity.
- Rod-shaped Si3N4 grains facilitated crack deflection, enhancing toughness.
- The material shows promise as a high-temperature wave-transparent ceramic for aerospace applications like radomes and antenna windows.
- This method offers better control over microstructure compared to conventional techniques, allowing synergistic enhancement of dielectric and thermomechanical properties.
Radomes for Hypersonic Vehicles
These porous Si3N4 ceramics show promising potential for use as radome materials on hypersonic platforms. Here's why:
1. High-temperature performance: The materials maintain stable dielectric properties up to 1100°C, which is crucial for hypersonic applications where extreme temperatures are encountered.
2. Low dielectric constant and loss: The porous Si3N4 ceramics exhibit a low dielectric constant (~3.3) and low dielectric loss (1.0-4.0 x 10-3), which are essential for radome materials to ensure minimal interference with electromagnetic waves.
3. Mechanical strength: With a flexural strength of 95 MPa and compressive strength of 132 MPa, these ceramics possess the mechanical robustness needed to withstand the extreme forces experienced during hypersonic flight.
4. Thermal insulation: The low thermal conductivity (4.2 W·K-1·m-1) helps protect internal components from the intense heat generated during hypersonic flight.
5. Tailorable properties: The dual-solvent templating method allows for precise control over pore size and structure, enabling optimization of the material's properties for specific hypersonic applications.
6. Thermal shock resistance: The uniform pore structure and rod-shaped Si3N4 grains contribute to improved thermal shock resistance, which is critical for rapid temperature changes experienced in hypersonic flight.
7. Low density: The high porosity (56%) results in a lower overall density, which is beneficial for weight reduction in aerospace applications.
These characteristics address many of the key challenges faced in developing radome materials for hypersonic platforms, including high-temperature stability, electromagnetic transparency, mechanical strength, and thermal management. However, it's important to note that further testing under actual hypersonic conditions and scaling up of production would likely be necessary before these materials could be implemented in real-world hypersonic platforms.
1. High-temperature performance: The materials maintain stable dielectric properties up to 1100°C, which is crucial for hypersonic applications where extreme temperatures are encountered.
2. Low dielectric constant and loss: The porous Si3N4 ceramics exhibit a low dielectric constant (~3.3) and low dielectric loss (1.0-4.0 x 10-3), which are essential for radome materials to ensure minimal interference with electromagnetic waves.
3. Mechanical strength: With a flexural strength of 95 MPa and compressive strength of 132 MPa, these ceramics possess the mechanical robustness needed to withstand the extreme forces experienced during hypersonic flight.
4. Thermal insulation: The low thermal conductivity (4.2 W·K-1·m-1) helps protect internal components from the intense heat generated during hypersonic flight.
5. Tailorable properties: The dual-solvent templating method allows for precise control over pore size and structure, enabling optimization of the material's properties for specific hypersonic applications.
6. Thermal shock resistance: The uniform pore structure and rod-shaped Si3N4 grains contribute to improved thermal shock resistance, which is critical for rapid temperature changes experienced in hypersonic flight.
7. Low density: The high porosity (56%) results in a lower overall density, which is beneficial for weight reduction in aerospace applications.
These characteristics address many of the key challenges faced in developing radome materials for hypersonic platforms, including high-temperature stability, electromagnetic transparency, mechanical strength, and thermal management. However, it's important to note that further testing under actual hypersonic conditions and scaling up of production would likely be necessary before these materials could be implemented in real-world hypersonic platforms.
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