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Effect of Aging Time on the Stability of Aqueous Y‐α‐SiAlON Precursor Powder Suspensions
Author(s) -
Pereira Catarina,
Olhero Susana,
Ferreira José M.F.
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.03621.x
Subject(s) - sialon , materials science , aqueous solution , sintering , ceramic , chemical engineering , hydrolysis , slip (aerodynamics) , rheology , composite material , mineralogy , chemistry , organic chemistry , physics , engineering , thermodynamics
A temporarily stable aqueous slip of Y‐α‐SiAlON precursors powders (Si 3 N 4 , Al 2 O 3 , Y 2 O 3 , and AlN powders) was successfully prepared using an AlN powder thermo‐chemically treated against hydrolysis (AlN‐TC). Aqueous suspensions of AlN‐TC and an Si 3 N 4 ‐based powders' mixture (Si 3 N 4 /Y 2 O 3 /Al 2 O 3 ) proved to have long‐term stability under separate deagglomeration by ball milling. However, the kinetic stability decreased when the two suspensions were mixed in the required proportion to obtain a precursor Y‐α‐SiAlON composition. This work aims at understanding better the aging phenomena and evaluating the feasibility of using aqueous processing to fabricate Y‐α‐SiAlON ceramics. The pH and rheological behavior of the suspensions were monitored along the time. The effects of drying conditions (room temperature or humidity‐controlled chamber) of slip‐cast samples on the crystalline phases and oxygen contents before and after sintering were evaluated. Drying under a moisture‐rich atmosphere favored hydrolysis of AlN and the appearance of β‐SiAlON as the main phase after sintering. The results allowed concluding that there is a time frame within which Y‐α‐SiAlON ceramics can be fabricated from aqueous suspensions.