Surface passivation of MgAl2O4 spinel powder by chemisorbing H3PO4 for easy aqueous processing
authors Olhero, SM; Ganesh, I; Torres, PMC; Ferreira, JMF
nationality International
journal LANGMUIR
abstract A stoichiometric MgAl2O4 spinel (MAS) powder was synthesized by heat treating at 1400 degrees C for 2 h a compacted mixture of alpha-Al2O3 and calcined caustic MgO, followed by crushing and milling. The surface of this powder was then passivated against hydrolysis with H3PO4 and Al(H2PO4)(3) in an ethanol solution. The as-passivated powder could then be dispersed in water using tetramethylammonium hydroxide (TMAH) and an ammonium salt of poly(acrylic acid) (Duramax D-3005) as dispersing agents and gelcast to form green consolidates with relatively high strength (> 15 MPa). The good dispersing behavior of the passivated powder in water was confirmed by the low viscosity of its suspension containing 41-45 vol % solids, demonstrating the viability of replacing organic solvents by water in colloidal processing of MAS-based ceramics. The Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and energy dispersive X-ray (EDAX) studies revealed that only negligible amounts of phosphate ions at the Surface are required to effectively protect the powder from reacting with water.
issn 0743-7463
year published 2008
volume 24
issue 17
beginning page 9525
ending page 9530
digital object identifier (doi) 10.1021/la801300m
web of science category Chemistry, Multidisciplinary; Chemistry, Physical; Materials Science, Multidisciplinary
subject category Chemistry; Materials Science
unique article identifier WOS:000258722100054
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journal impact factor 3.557
5 year journal impact factor 3.702
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