Nano Archive

Formation of ultrafine and dense alpha-Al2O3 nanoparticles via kinetic phase change in a dynamic process

Liu, I-Lung and Shen, Pouyan and Chen, Shuei-Yuan (2010) Formation of ultrafine and dense alpha-Al2O3 nanoparticles via kinetic phase change in a dynamic process. Journal of Nanoparticle Research, 12 (8). pp. 2929-2940.

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Abstract

Ultrafine (5 nm) Al2O3 nanoparticles having a predominant alpha-type structure and with an internal compressive stress up to ca. 15 GPa were synthesized by pulsed laser ablation on Al target under a very high power density (1.8 x 10(12) W/cm(2)) with oxygen flow in vacuum. The ultrafine alpha-Al2O3 was alternatively formed from the minor gamma-Al2O3 nanocondensates upon electron irradiation. In such a case, the polymorphs follow a special crystallographic relationship [110](gamma)//[2 (1) over bar(1) over bar0](alpha); ((1) over bar1 (1) over bar//(0 (1) over bar 14)(alpha) with a mixed mismatch strain yet nonparallel close-packed planes indicating a reconstructive-type transformation. The formation of metastable alpha-Al2O3 in the dynamic processes can be rationalized by the kinetic phase change from the amorphous lamellar and/or gamma-Al2O3 depending on their free energy versus cell volume curves. The dense and ultrafine-sized Al2O3 polymorphs with a rather low minimum band gap of 3.7 eV shed light on their natural occurrence in dynamic settings and abrasive as well as catalytic/optoelectronic applications.

Item Type:Article
Subjects:Material Science > Nanostructured materials
ID Code:9928
Deposited By:CSMNT
Deposited On:26 Dec 2010 13:05
Last Modified:26 Dec 2010 13:05

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