Fabrication of transparent [gamma]-Al[sub 2]O[sub 3] from nanosize particles

Journal Article · Mon Aug 01 00:00:00 EDT 1994 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1994.tb07104.x· OSTI ID:7155155

Gallas, M R; Hockey, B; Pechenik, A; Piermarini, G J ^[1]

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1. National Inst. of Standards and Technology, Gaithersburg, MD (United States). Materials Science and Engineering Lab.

The compaction and heat-treatment behavior of nanosize [gamma]-Al[sub 2]O[sub 3] powder (average diameter = 20 nm) was studied. A diamond anvil high-pressure cell was used to compact the powder at pressures up to 3 GPa, both in air at room temperature and under liquid nitrogen, followed by pressureless heat treatment at 800 C. For all conditions studied, the fabricated compacts were optically transparent. X-ray diffraction confirmed retention of the [gamma]-phase. The compacts were also characterized before and after heat treatment by microhardness measurements and by transmission electron microscopy. For both ambient and cryogenic compaction, sample hardness increased with pressure, and heat treatment resulted in about a 50% increase in hardness independent of the initial green-state value. Samples compacted in LN[sub 2] were significantly harder (up to 9.6 GPa) than those compacted in air. TEM examination revealed a random-dense-packed particle structure and interconnected porosity; interstitial void dimensions, however, were always less than the average particle diameter (20 nm). Observed effects on the increase in hardness could not be explained by microstructural changes normally attributed to increased compaction pressure or heat treatment, most notably densification. Alternative explanations are proposed.

• OSTI ID: 7155155
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 77:8; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
FABRICATION
HARDNESS
MICROSTRUCTURE
COMPACTING
EXPERIMENTAL DATA
HEAT TREATMENTS
PARTICLE SIZE
ALUMINIUM COMPOUNDS
CHALCOGENIDES
DATA
INFORMATION
MECHANICAL PROPERTIES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
SIZE
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360203 - Ceramics
Cermets
& Refractories- Mechanical Properties