Gelcasting of alumina using urea-formaldehyde - II. Gelation and ceramic forming

Citation
K. Prabhakaran et C. Pavithran, Gelcasting of alumina using urea-formaldehyde - II. Gelation and ceramic forming, CERAM INT, 26(1), 2000, pp. 67-71
Citations number
10
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
CERAMICS INTERNATIONAL
ISSN journal
02728842 → ACNP
Volume
26
Issue
1
Year of publication
2000
Pages
67 - 71
Database
ISI
SICI code
0272-8842(2000)26:1<67:GOAUU->2.0.ZU;2-N
Abstract
A new aqueous gelcasting system for alumina was investigated. Concentrated (55 vol%) aqueous ceramic slurries dispersed using a mineral acid was gelle d by pH controlled condensation polymerisation of methylolurea monomers der ived from urea and formaldehyde. Gelation of the slurry occurred at ambient conditions during 30-80 min at pH 2.5-3. Humidity controlled drying of gel led bodies prepared using alumina of average particle size of 0.34 mu m yie lded green bodies with density of 57% (corrected for organic content) of th eoretical density and strength (by diametrical compression test) of 0.35 MP a at polymer content similar to 6% by weight of alumina. Debinderization of the green bodies was accomplished by pyrolysis in air below 350 degrees C. The relative density of the bodies sintered at 1550 degrees C for 2 h was 97% TD and the shrinkage during sintering was isotropic and averaged 14 to 16%. (C) 1999 Elsevier Science Ltd and Techna S.r.l. All rights reserved.