Continuous α-Al2O3 fibers grown by seeding with in-situ suspension. Issue 10 (July 2020)

• Record Type: Journal Article
• Authors: Li, Xiangdong; Su, Xiaohui; Xiao, Hongrui; Chen, Lifu; Li, Siwei; Tang, Ming
• Is Part Of: Ceramics international. Volume 46:Issue 10(2020)Part A
• Page Start: 15638
• Page End: 15645
• Publication Date: 2020-07
• Subjects: α-Al2O3 fiber -- Seeding -- Densification -- Sintering; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2020.03.112
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: A highly stable α-Al2 O3 suspension with average particle size of ~30 nm was prepared via selective corrosion of co-precipitated α-Fe2 O3 /α-Al2 O3 mixture using hydrochloric acid solution. Using the in-situ α-Al2 O3 suspension as a seeding agent, continuous α-Al2 O3 fibers were achieved via sol-gel route. Effects of seeding and sintering on the densification behavior of the alumina fibers were investigated. Adding 1.5 wt.% of ultrafine α-Al2 O3 seeds enabled α-Al2 O3 to heterogeneously nucleate at a temperature as low as 700 °C, and the number of nucleation sites was high enough to eliminate the "vermicular" structures during the development of α-Al2 O3 from transient phases. By calcination at 1200 °C, α-Al2 O3 fiber with high density and equiaxed grains was directly obtained. A modified two-step sintering method could further result in α-Al2 O3 fibers attaining almost full density with the finer grain size down to ~100 nm. Doping with trace amounts of silica was found to slow down the grain boundary migration and suppress the abnormal grain growth of α-Al2 O3 .