Improved transparency and hardness in α-alumina ceramics fabricated by high-pressure SPS of nanopowders
journal contributionposted on 14.10.2016, 10:46 by Shaghayegh Ghanizadeh, Salvatore Grasso, Prabhu Ramanujam, Vaidhy VaidhyanathanVaidhy Vaidhyanathan, J.G.P. Binner, Peter M. Brown, Judah Goldwasser
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 minutes. These samples offered in-line transmittance values of up to ~80% and microhardness values of 22 GPa.
- Mechanical, Electrical and Manufacturing Engineering