Enhanced Mechanical Properties of Al2O3 Nanoceramics via Low Temperature Spark Plasma Sintering of Amorphous Powders

• Published in: Materials Vol. 16; no. 16; p. 5652
• Main Authors: Zhang, Dongjiang, Yu, Rui, Feng, Xuelei, Guo, Xuncheng, Yang, Yongkang, Xu, Xiqing
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 17.08.2023; MDPI
• Subjects: Al2O3 nanoceramics; Aluminum; Aluminum oxide; amorphous; Bend strength; Ceramics; Composite materials; Crack propagation; Diamond pyramid hardness; Fracture toughness; Free energy; Grain size; Graphite; Hot pressing; Low temperature; low temperature sintering; Mechanical properties; Metastable state; Nanoparticles; NMR; Nuclear magnetic resonance; Particle size; Plasma sintering; Polycrystals; Shear strain; Sintering (powder metallurgy); Spark plasma sintering; Temperature; Transgranular fracture; United States > US; China; Japan
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16165652

In this work, Al2O3 nanoceramics were prepared by spark plasma sintering of amorphous powders and polycrystalline powders with similar particle sizes. Effective comparisons of sintering processes and ultimate products depending on starting powder conditions were explored. To ensure near-full density higher than 98% of the Al2O3 nanoceramics, the threshold temperature in SPS is 1450 °C for polycrystalline Al2O3 powders and 1300 °C for amorphous powders. The low SPS temperature for amorphous powders is attributed to the metastable state with high free energy of amorphous powders. The Al2O3 nanoceramics prepared by amorphous powders display a mean grain size of 170 nm, and superior mechanical properties, including high bending strength of 870 MPa, Vickers hardness of 20.5 GPa and fracture toughness of 4.3 MPa∙m1/2. Furthermore, the Al2O3 nanoceramics prepared by amorphous powders showed a larger dynamic strength and dynamic strain. The toughening mechanism with predominant transgranular fracture is explained based on the separation of quasi-boundaries.