Preparation of spherical α‐Al2O3 nanoparticles by microwave hydrothermal synthesis and addition of nano‐Al seeds. Issue 9 (4th May 2022)

• Record Type: Journal Article
• Authors: Wang, Zhiyuan; Mai, Zenghui; Wu, Yixiao; Wang, Ying; Cao, Zhenzhen; Li, Mingliang; Fan, Bingbing; Shao, Gang; Wang, Hailong; Xu, Hongliang; Zhang, Rui; Lu, Hongxia
• Is Part Of: Journal of the American Ceramic Society. Volume 105:Issue 9(2022)
• Page Start: 5585
• Page End: 5597
• Publication Date: 2022-05-04
• Subjects: kinetics mechanism -- mechanical properties -- microwave hydrothermal technique -- nano‐Al seeds -- spherical α‐Al2O3 nanoparticles; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.18524
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: Due to their special appearance, spherical α‐Al2 O3 nanoparticles play an important role for obtaining high‐performance structural and functional ceramics. However, there are still problems such as easily agglomerates to form worm‐like structures at high temperatures and difficult availability of spherical nanoparticles. In this study, spherical α‐Al2 O3 nanoparticles with high dispersion were prepared by a combination of a microwave hydrothermal method and an addition of nano‐Al particles as seeds. First, spherical amorphous alumina precursors were synthesized by the microwave hydrothermal method at 100°C for 30 min using Al2 (SO4 )3 ·18H2 O, Al(NO3 )3 ·9H2 O, and urea, as raw materials, and then spherical α‐Al2 O3 nanoparticles with a diameter of about 66 nm were acquired after calcined the precursor at 1050°C for 90 min by adding nano‐Al seeds, which reduced the calcination temperature by 50°C and holding time by 30 min compared to that without seeds. Kinetic analysis shows that 5 wt.% nano‐Al seeds can reduce the activation energy of crystalline transition of γ‐Al2 O3 to α‐Al2 O3 from 516.51 to 474.37 kJ/mol. Moreover, the microscopic mechanism of nano‐Al particles as seeds was investigated. The characterizations of sintering properties show that spherical α‐Al2 O3 nanoparticles facilitate the acquisition of uniform microstructure for resulting ceramic and the fracture modes include both intergranular and transgranular fractures.