Control of continuous α-Al2O3 fibers by self-seeding and SiO2-Sol doping. Issue 9 (15th June 2019)

• Record Type: Journal Article
• Authors: Li, Xiangdong; Xu, Haonan; Wang, Qi; Li, Siwei; Xiao, Hongrui; Zhang, Li; Tang, Ming; Chen, Lifu
• Is Part Of: Ceramics international. Volume 45:Issue 9(2019)
• Page Start: 12053
• Page End: 12059
• Publication Date: 2019-06-15
• Subjects: α-Al2O3 fiber -- Self-seeding -- Doping -- Microstructure; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2019.03.101
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: The effects of self-seeding and SiO2 -sol doping on the sol–gel preparation of α-Al2 O3 fibers are investigated. Self-seeding induces heterogeneous nucleation of α-Al2 O3 from the precursor gels at a low temperature of 800 °C. Using transmission electron microscopy and X-ray diffraction analysis, the primary crystallite size ( d p ) of α-Al2 O3 in the seeded fibers is determined as ∼30 nm, which is much smaller than the size (∼50 nm) in the unseeded fibers. Moreover, self-seeding increases the γ-to-α transformation kinetics and lowers the transformation temperature by 175 °C. Heating at 1500 °C could sinter the self-seeded α-Al2 O3 fibers nearly to full density with a grain size of ∼1 μm. By doping with SiO2 sols, this final grain size can be decreased with suppression of the grain boundary migration, at the expense of increased phase transition temperature. Therefore, dense α-Al2 O3 fibers of submicron grains could be achieved by the combination of self-seeding and SiO2 -sol doping.