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 m1/2 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.