Nanostructured Y sub 2 O sub 3; Synthesis and relation to microstructure and properties

Journal Article · Tue Oct 01 04:00:00 EDT 1991 · Scripta Metallurgica; (United States)

OSTI ID:5767344

Skandan, G; Hahn, H ^[1]; Parker, J C ^[2]

---

1. Dept. of Materials Science and Engineering, Rutgers State Univ. of New Jersey, Piscataway, NJ (US)
2. Nanophase Technologies Corp., Darien, IL (US)

It has been shown that a variety of nanostructured (n-) metal-oxide ceramics such as n-TiO{sub 2}, n-ZrO{sub 2}, n-Al{sub 2}O{sub 3}, n-ZnO and n-MgO can be produced using the inert gas condensation process. Amongst all the nanostructured oxides, the synthesis, microstructure, sintering, and mechanical properties of n-TiO{sub 2} have been studied the most extensively. The gas condensation preparation of nanostructured metal-oxide ceramics involves evaporation of metal nanoparticles, collection and post- oxidation. The original synthesis studies of n-TiO{sub 2} showed that in order to avoid formation of the many low oxidation state oxides in the Ti-O system, the post-oxidation had to be performed by rapidly exposing the Ti nanoparticles to pure oxygen gas. By doing so, the highest oxidation state and the most stable structure, rutile, was obtained. An undesired feature of this step is that the nanoparticles heat up to high temperatures for a brief period of time due to the exothermic nature of the oxidation. As a consequence, the particles with an average size of 12 nm tend to agglomerate into larger structures up to 50 nm. The agglomerated state of the powder is important since it determines the original density and pore size distribution after compaction, as well as the sintering characteristics and final microstructure of the bulk sample. As a consequence of the preparation procedure of n-TiO{sub 2} and the resulting agglomeration, the pore size distribution of n-TiO{sub 2} compacted at room temperature is very wide, with pore sizes ranging from 1 to 200 nm. Nevertheless, the n-TiO{sub 2} sinters at temperatures several hundred degrees lower than conventional coarse grained ceramics. From the previous results on n- TiO{sub 2} it is anticipated that better microstructures and properties can be achieved by reducing the agglomeration of nanostructured powders through a more controlled post- oxidation process.

• OSTI ID: 5767344
• Journal Information: Scripta Metallurgica; (United States), Journal Name: Scripta Metallurgica; (United States) Vol. 25:10; ISSN 0036-9748; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
AGGLOMERATION
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
HEXAGONAL LATTICES
MECHANICAL PROPERTIES
MICROSTRUCTURE
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
POWDERS
SIZE
SYNTHESIS
TEMPERATURE RANGE
TEMPERATURE RANGE 1000-4000 K
TRANSITION ELEMENT COMPOUNDS
VAPOR CONDENSATION
YTTRIUM COMPOUNDS
YTTRIUM OXIDES