Researchers at Sun Yat-sen University have developed a novel method to create porous Si3N4 ceramics with uniform, fine structures, offering a game-changing solution for radar-transparent materials used in hypersonic aircraft.
Sun Yat-sen University researchers have constructed porous Si3N4 ceramics with an extremely uniform and fine structure for radar-transparent materials applied in hypersonic aircraft, by means of a novel method.
Opening up Porous Si3N4
Aircraft require critical elements like Radomes and wave transmissive antenna windows that serve the same purpose by protecting the radar antennas while maintaining uninterrupted communication. The lenses are currently based on ceramics (oxides and nitrides), which are the most commonly used material for wave-transmitting.
The Si3N4 ceramics with high melting point and excellent mechanical performance are great potential uses for the future hypersonic vehicle. Nevertheless, the poor dielectric and thermal insulation performances of dense Si3N4 ceramics killed their applicabilities for high-speed flight due to its requirements in ultra-high guidance accuracy and advanced thermal protection system.
Microstructural engineering can be used to optimize the dielectric, mechanical and thermal response of the wave permeable materials. Therefore, it is necessary to achieve porous Si3N4 ceramics in the application of radomes and antenna windows for hypersonic aircraft since they should withstand high temperature environment, as well as powerful thermal or mechanical shocks and also maintain small permittivity which is closely related to good radar performance.
Pioneer Pores Control
Striking the balance between excellent mechanical strength and efficient wave transmission has always presented a challenge, often necessitating novel design solutions to optimise both.
A group of material scientists from Sun Yat-sen University in China led by Dr. Zhilin Tian and Bin Li, 1 has recently unraveled a dual-solvent templating followed by freeze-casting strategy to fabricate porous Si3N4 ceramic featuring uniform fine structures (Fig. Such an approach provides strict regulation of pore structure and size — one of the most important factors in the characteristics high-temperature gassy transparent materials.
Problems with traditional methods include direct topic foaming, gel casting and organic template impregnation cannot meet the requirements of the pore uniformity, standardization. On the other hand, the new approach can easily convert anisotropic prismatic pores to isotropic spherical pores and this synergy towards mechanical, thermal and dielectric properties enhancement in porous Si3N4 ceramics.
Conclusion
The results of this research provide a foundational basis for future development in wave-transparent materials, providing great improvements to radome and antenna window designs for hypersonic aircraft. Developing a new high-toughness, temperature-resistant thermal protection material could enable an entirely new class of ceramics suitable for use by more heat-sensitive components at the surface or in the hot core of hypersonic vehicles, bringing with it built-in curvilinear throttling capability to mitigate excessive heating and making safe high-speed flight reachable.
