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

Abstract

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.

Authors:
; ; ;  [1]
  1. National Inst. of Standards and Technology, Gaithersburg, MD (United States). Materials Science and Engineering Lab.
Publication Date:
OSTI Identifier:
7155155
Resource Type:
Journal Article
Journal Name:
Journal of the American Ceramic Society; (United States)
Additional Journal Information:
Journal Volume: 77:8; Journal ID: ISSN 0002-7820
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Gallas, M R, Hockey, B, Pechenik, A, and Piermarini, G J. Fabrication of transparent [gamma]-Al[sub 2]O[sub 3] from nanosize particles. United States: N. p., 1994. Web. doi:10.1111/j.1151-2916.1994.tb07104.x.
Gallas, M R, Hockey, B, Pechenik, A, & Piermarini, G J. Fabrication of transparent [gamma]-Al[sub 2]O[sub 3] from nanosize particles. United States. https://doi.org/10.1111/j.1151-2916.1994.tb07104.x
Gallas, M R, Hockey, B, Pechenik, A, and Piermarini, G J. 1994. "Fabrication of transparent [gamma]-Al[sub 2]O[sub 3] from nanosize particles". United States. https://doi.org/10.1111/j.1151-2916.1994.tb07104.x.
@article{osti_7155155,
title = {Fabrication of transparent [gamma]-Al[sub 2]O[sub 3] from nanosize particles},
author = {Gallas, M R and Hockey, B and Pechenik, A and Piermarini, G J},
abstractNote = {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.},
doi = {10.1111/j.1151-2916.1994.tb07104.x},
url = {https://www.osti.gov/biblio/7155155}, journal = {Journal of the American Ceramic Society; (United States)},
issn = {0002-7820},
number = ,
volume = 77:8,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 1994},
month = {Mon Aug 01 00:00:00 EDT 1994}
}