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AI 2 O 3 Coatings as Diffusion Barriers Deposited from Particulate‐Containing Sol‐Gel Solutions
Author(s) -
Shaw Leon,
Abbaschian Reza
Publication year - 1995
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.1151-2916.1995.tb07980.x
Subject(s) - materials science , coating , sol gel , diffusion , intermetallic , chemical engineering , cracking , colloid , composite material , shrinkage , metallurgy , nanotechnology , alloy , physics , engineering , thermodynamics
A procedure for the formation of A1 2 O 3 coatings as diffusion barriers between ductile reinforcements (e.g., Nb and Ta) and intermetallic matrices (e.g., MoSi 2 and NiAl) is described. The coating technique involved sol‐gel processing of alumina ‐forming sols with the addition of submicrometer‐sized A1 2 O 3 particles. Cracking in the coatings, a typical shortcoming of alumina sol‐gel coating, was overcome by the addition of the fine particles into the sols. The surface charge of the A1 2 O 3 particles was adjusted to be the same as the AIO(OH) colloids in the sols and electrophoresis was used to codeposit A1 2 O 3 and AIO(OH) onto the surfaces of the reinforcements. The alumina gel derived from the sols acted as binder for the alumina particles, while the particles reduced the shrinkage of the sol‐gel coatings and promoted the formation of dense coatings. The thickness of the coatings could be easily controlled without cracking and the effectiveness of the coatings as diffusion barriers was improved substantially.