Sintering behavior and morphology control of porous Al2O3‐SiO2 ceramics for radome applications. Issue 5 (2nd May 2022)

• Record Type: Journal Article
• Authors: Ren, Yuhan; Zhang, Biao; Shao, Junda; Ye, Jian; Liu, Qiang; Gao, Ye; Zhang, Haoqian; Zhong, Zhaoxin; Wang, Yang; Ye, Feng
• Is Part Of: International journal of applied ceramic technology. Volume 19:Issue 5(2022)
• Page Start: 2489
• Page End: 2499
• Publication Date: 2022-05-02
• Subjects: Al2O3‐SiO2‐system -- porous mullite ceramics -- dielectric properties -- radome application; Ceramics -- Periodicals; Ceramics -- Technological innovations -- Periodicals; 620.1405
• DOI: 10.1111/ijac.14078
• Languages: English
• ISSNs: 1546-542X

Abstract

Abstract: Ceramics from porous Si3 N4 and its derivatives SiAlON and Si2 N2 O were once considered the most promising high‐temperature wave‐transmitting materials. However, their large‐scale application in the field of radomes is greatly restricted due to their poor oxidation resistance, high preparation costs, and expensive raw materials. Therefore, the development of low‐cost porous oxide ceramics remains of significant interest to the field of high‐temperature wave transmission. Surprisingly, mullite ceramics, which are representative of the Al2 O3 ‐SiO2 ‐system of ceramics, are ultra‐low‐cost materials with the potential to replace ceramics from Si3 N4 and its derivatives. In this paper, integrated porous Al2 O3 ‐SiO2 ‐system ceramics were successfully prepared for load‐bearing/wave‐transmitting applications, using inexpensive calcined kaolin and alumina powder as the main raw materials. Calcined kaolin can provide seeds for the growth and development of mullite crystals in the ceramic system. High‐strength and high‐porosity ceramics were obtained with the mullite morphology controlled through the molar ratio of Al2 O3 to SiO2 and the resulting content of mullite seeds. With increasing of mullite seed content, the length and radial width of mullite whiskers with "interlocking structure" gradually change from rod‐shaped "long and thick" to needle‐like "short and thin." The prepared porous Al2 O3 ‐SiO2 ceramics have high flexural strength, fracture toughness, and good dielectric properties.