Lanthanum hexaluminate (LaAl11O18), which features easily cleavable atomic planes in the magnetoplumbite (MP) structure, is a good candidate material for the fiber/matrix interface in oxide/oxide-fiber-reinforced composite. Difficulties that are encountered when using sol-gel synthesis to produce this material include the high crystallization temperature and the occurrence of an intermediate phase. This paper presents a method to overcome these difficulties by introducing crystalline seeds into the LaAl11O18 sol during the fiber coating. Seed particles are deposited initially on the fibers via electrostatic forces. Then, the sol is dip-coated on the preseeded fibers, and the final LaAl11O18 coating is achieved via the use of heat treatments. The crystallization temperature can be reduced by at least 50°C, in comparison with that for the unseeded case, according to differential scanning calorimetry measurements, and no intermediate LaAlO3 phase is formed. The estimated seed numbers are on the order of 109 seeds/cm3 in the preseeded sol-coated fiber surfaces and 1011 seeds/cm3 in the 4-wt%-seeded gels. The crystallization and structure of the La1-xAl12-yO19-z MP phase in the 4-wt%-seeded gels that have been heated at 400° and 1200°C have been studied using powder neutron diffraction.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of the American Ceramic Society|
|State||Published - Jan 1 2000|
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Materials Chemistry