Premium
Aqueous Processing and Stabilization of Manganese Zinc Ferrite Powders via a Passivation–Dispersion Approach
Author(s) -
Mandanas Michael M.,
Shaffer Walter,
Adair James H.
Publication year - 2002
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.1151-2916.2002.tb00427.x
Subject(s) - dispersant , isoelectric point , passivation , zinc , manganese , aqueous solution , oxalic acid , surface charge , materials science , oxalate , chemical engineering , zeta potential , colloid , dispersion (optics) , rheology , zinc ferrite , inorganic chemistry , chemistry , nanoparticle , metallurgy , composite material , nanotechnology , organic chemistry , physics , layer (electronics) , optics , enzyme , engineering
A dispersion scheme for aqueous processing of manganese zinc ferrite suspensions is presented. The addition of oxalic acid leads to the formation of a uniform negative charge on the surface such that a cationic polyelectrolyte, polyethyleneimine (PEI), adsorbs and provides electrosteric dispersion. At 0.5 w/w (weight percent with respect to the dry powder) oxalic acid addition, there is a relatively uniform negative surface charge (approximately −30 mV) within the suspension pH range investigated (3–10), eliminating the isoelectric point (pH ∼7.6) present for the as‐received metal oxide powder. At the addition of 0.5 w/w PEI on an oxalate‐treated surface, the surface charge is constant and positive (∼20 mV) through a wide pH range, ∼5–10. The resulting rheological data for passivation–dispersion of relatively high‐solids manganese zinc ferrite suspensions (∼80 wt%) demonstrate improved colloid stability with improved rheological properties. The resulting apparent viscosity and Bingham yield point is 0.01 Pa·s (12.0 cP) and 0.24 Pa (2.4 dynes/cm 2 ), respectively. A sulfonated napthalene‐based dispersant, typically used in industry, gives an apparent viscosity and Bingham yield point of 0.03 Pa·s (32 cP) and 3.1 Pa (31 dynes/cm 2 ), respectively.