Improved transparency and hardness in α-alumina ceramics fabricated by high-pressure SPS of nanopowders
journal contributionposted on 14.10.2016 by Shaghayegh Ghanizadeh, Salvatore Grasso, Prabhu Ramanujam, Vaidhy Vaidhyanathan, J.G.P. Binner, Peter M. Brown, Judah Goldwasser
Any type of content formally published in an academic journal, usually following a peer-review process.
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