Fused silica ceramic has become one of the most widely used radome materials in the world since the 1970s. But its poor mechanical properties restricted its application to some extent. To improve the mechanical properties of the fused silica ceramic and keep its characteristic for radome materials, silicon nitride (Si3N4) whisker‐reinforced fused silica ceramics were prepared by a slip‐casting method in the work. The influence of Si3N4 whisker contents on the properties of the slurry was studied, indicating that the preferable pH values of the slurry were 4–6 and whisker contents were 10 wt.%. The flexural strength of as‐prepared Si3N4w/SiO2 ceramic was about 74.35 MPa, exhibiting an increase of 7.75% over that of the pure silica sample. Its dielectric constant in the range from 8 to 12 GHz and tanδ under 10 GHz were, respectively, 3.37 and .0011. It is of great interest to find that Si3N4w/SiO2 has excellent oxidization resistance and its mass maintains even at 1270°C.

Fused silica ceramics are widely applied for radome materials, crucibles, and vanes, but the mechanical properties were deteriorated due to the cristobalite crystallization. The fused silica ceramics added with by β-Si 3 N 4 whiskers were prepared by a slip-casting method to retard the cristobalite crystallization. The influences of the sintering environments and the β-Si 3 N 4 whiskers on the microstructure and phase structure were investigated. The silanol (Si-(OH) n ) and oxygen vacancies (V O ) in the fused silica in formed in different conditions were studied by Fourier Transform Infra-Red (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the results indicated that the ball-milled produced a large amount of the silanol groups onto the surface of the fused silica particles. The fused silica heated in the vacuum created the maximum oxygen vacancies (24.2%) on the surfaces. Silanol groups reacted with the β-Si 3 N 4 whiskers, and the O atoms in the silanol groups were fixed into the bulk materials. And the crystallization kinetics and the activation energy of Si 3 N 4w /SiO 2 ceramics at the temperature ranging from 1200 to 1400 • C were calculated based on the JMA(Johnson-Mehl-Avrami) model. The activation energy of the fused silica ceramics with the addition of the β-Si 3 N 4 is 506.2 kJ/mol, increased by 23.6% than that of the pure fused silica ceramic.