Fabrication and characterization of Si ₃ N ₄ whisker‐reinforced SiO ₂ ceramic for radome materials

Abstract

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.

Electromagnetic wave absorption properties of hot‐pressed Si3N4‐SiC ceramic nanocomposites

“…9,10 It should be noted that SiC (especially nanosized SiC) is an excellent high-temperature electromagnetic wave absorption (EMA) agent, [11][12][13][14][15] and Si 3 N 4 is an excellent high-temperature electromagnetic wave transparent material. [16][17][18] Therefore, Si 3 N 4 -SiC ceramic nanocomposites have the potential to be high-temperature structural-EMA integrated materials. So far, the majority of EMA studies for Si 3 N 4 -SiC ceramic nanocomposites have concentrated on high-porous forms such as foams, 19 aerogels, 20,21 and felts, 22 whereas studies on the EMA properties of high-density ceramic nanocomposites are scarce.…”

“…It should be noted that SiC (especially nanosized SiC) is an excellent high‐temperature electromagnetic wave absorption (EMA) agent, 11–15 and Si 3 N 4 is an excellent high‐temperature electromagnetic wave transparent material 16–18 . Therefore, Si 3 N 4 ‐SiC ceramic nanocomposites have the potential to be high‐temperature structural‐EMA integrated materials.…”