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Alumina/Epoxy Interpenetrating Phase Composite Coatings: I, Processing and Microstructural Development
Author(s) -
Craig Bradley D.,
Francis Lorraine F.
Publication year - 1998
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.1151-2916.1998.tb02745.x
Subject(s) - materials science , epoxy , composite material , curing (chemistry) , microstructure , ceramic , composite number , coating , flexural strength , porosity , amorphous solid , chemistry , organic chemistry
Interpenetrating phase composite (IPC) coatings consisting of continuously connected Al 2 O 3 and epoxy phases were fabricated. The ceramic phase was prepared by depositing an aqueous dispersion of Al 2 O 3 (0.3 μm) containing orthophosphoric acid, H 3 PO 4 , (1–9.6 wt%, solid basis) and heating to create phosphate bonds between particles. The resulting ceramic coating was porous, which allowed the infiltration and curing of a second‐phase epoxy resin. The effect of dispersion composition and thermal processing conditions on the phosphate bonding and ceramic microstructure was investigated. Reaction between Al 2 O 3 and H 3 PO 4 generated an aluminum phosphate layer on particle surfaces and between particles; this bonding phase was initially amorphous, but partially crystallized upon heating to 500°C. Flexural modulus measurements verified the formation of bonds between particles. The coating porosity (and hence epoxy content in the final IPC coating) decreased from ∼50% to 30% with increased H 3 PO 4 loading. The addition of aluminum chloride, AlCl 3 , enhanced bonding at low temperatures but did not change the porosity. Diffuse reflectance FTIR showed that a combination of UV and thermal curing steps was necessary for complete curing of the infiltrated epoxy phase. Al 2 O 3 /epoxy IPC coatings prepared by this method can range in thickness from 1 to 100 μm and have potential applications in wear resistance.