Porous Si3N4-based ceramics with uniform pore structure originated from single-shell hollow microspheres.

Herein, the advantage of single-shell hollow microspheres on forming pores has been exploited to acquire porous ceramics with homogeneous microstructure, while the hollow microspheres also acted as reaction source. Dispersant reaction method has been applied to realize the perfect combination between microspheres and Si₃N₄ particles, which could be attributed to the repulsion between particles is weakened, particles agglomerate together and holding microspheres among them tightly. Owing to the normal distribution of hollow spheres and their single-shell structure, porous Si₂N₂O-Si₃N₄ ceramics with uniform pore distribution have been fabricated. The results show that the addition of silica hollow spheres contributes to the decrease in dielectric constant, since their porosity could be increased effectively and Si₂N₂O phase exhibiting low dielectric constant is generated. High-performance porous Si₃N₄ ceramics with porosity of 45.7% have been prepared through employing fly ash hollow microspheres, which possess flexural strength of 108.76 ± 6.25 MPa, fracture toughness of 1.78 ± 0.09 MPa m^1/2 and dielectric constant of 3.53. This strategy is proved to be a convenient, eco-friendly and effective method to synthesize ideal candidates for radomes. [ABSTRACT FROM AUTHOR]