Improved transparency and hardness in α-alumina ceramics fabricated by high-pressure SPS of nanopowders. Issue 1 (January 2017)

• Record Type: Journal Article
• Authors: Ghanizadeh, Shaghayegh; Grasso, Salvatore; Ramanujam, Prabhu; Vaidhyanathan, Bala; Binner, Jon; Brown, Peter; Goldwasser, Judah
• Is Part Of: Ceramics international. Volume 43:Issue 1(2017)Part A
• Page Start: 275
• Page End: 281
• Publication Date: 2017-01
• Subjects: Nanocrystalline -- Alumina -- SPS -- Hot press -- Transparent; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2016.09.150
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Nanocrystalline alumina powder with an average crystallite size of ≤50 nm has been consolidated by spark plasma sintering (SPS) and hot pressing (HP) with a view to achieving dense, fine grained alumina bodies that display transparency. When as-synthesised powder was densified directly, excessive grain growth resulted from both the SPS and HP techniques and hence a large final grain size was observed. Attempts to improve the uniformity of the green microstructure prior to densification were unsuccessful when spray freeze dried granules were used, whether pre-pressed into a compact or not. The use of 53% dense slip cast green compacts, however, enabled final density of ~99.96% and a mean grain size of ~0.32 µm to be achieved when SPS conditions of 1200 °C and 500 MPa were applied for 20 min. These samples offered in-line transmittance values of up to ~80% and microhardness values of 22 GPa.