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Nano-alpha-Al2O3 by liquid-feed flame spray pyrolysis
R M Laine1, J C Marchal, H P Sun
1Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136, USA. talsdad@umich.edu
Nature Materials
|August 8, 2006
Summary
Liquid-feed flame spray pyrolysis efficiently converts transition alumina nanoparticles into highly dispersible alpha-alumina powders. These novel nano-alpha-alumina powders enable pressureless sintering to over 99.5% density with sub-micrometre grain sizes.
Area of Science:
- Materials Science
- Nanotechnology
- Ceramic Engineering
Background:
- Nanometre-sized transition (t)-aluminas are crucial for high-quality alumina ceramics.
- Current gas-phase production methods yield undesired delta, gamma, and theta phases, hindering the creation of nano/submicrometre-grained alpha-alumina.
- Polymorphism and high nucleation energy for alpha-alumina impede controlled grain size processing and densification.
Purpose of the Study:
- To develop a method for producing dispersible nano-alpha-alumina powders from nano-t-aluminas.
- To investigate the phase transformation and surface properties of the resulting nano-alpha-alumina.
- To evaluate the sinterability and final microstructure of ceramics produced from these powders.
Main Methods:
- Liquid-feed flame spray pyrolysis was employed to process nano-t-aluminas.
- Phase transformation and surface dehydration were analyzed.
- Pressureless sintering experiments were conducted on the produced powders.
Main Results:
- Liquid-feed flame spray pyrolysis converted nano-t-aluminas to 30-80 nm alpha-alumina powders with 50-85% phase transformation.
- The resulting alpha-alumina powders exhibited fully dehydrated surfaces.
- These powders achieved >99.5% density with final grain sizes ≤500 nm via pressureless sintering, without sintering aids.
Conclusions:
- Liquid-feed flame spray pyrolysis is an effective method for producing nano-alpha-alumina powders.
- The unique properties of these powders facilitate high-density sintering with controlled sub-micrometre grain sizes.
- This advancement offers a pathway for improved processing of advanced alpha-alumina components.
