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Hydrolysis and Dispersion Properties of Aqueous Y 2 Si 2 O 7 Suspensions
Author(s) -
Sun Ziqi,
Zhu Xinwen,
Li Meishuan,
Zhou Yanchun,
Sakka Yoshio
Publication year - 2009
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.1551-2916.2008.02860.x
Subject(s) - polyacrylic acid , colloid , isoelectric point , hydrolysis , dispersant , chemistry , polyethylenimine , aqueous solution , flocculation , steric effects , dispersion (optics) , suspension (topology) , polymer , adsorption , chemical engineering , inorganic chemistry , organic chemistry , transfection , biochemistry , physics , mathematics , homotopy , pure mathematics , optics , gene , enzyme , engineering
The dispersion of aqueous γ‐Y 2 Si 2 O 7 suspensions, which contain only one component but have a complex ion environment, was studied by the introduction of two different polymer dispersants, polyethylenimine (PEI) and polyacrylic acid (PAA). The suspension without any dispersant remains stable in the pH range of 9–11.5 because of electrostatic repulsion, while it is flocculated upon stirring due to the readsorption of hydrolyzed ions on the colloid surface. However, suspensions with 1 dwb% PEI exhibit greater stability in the pH range of 4–11.5. The addition of PEI shifts the isoelectric point (IEP) of the suspensions from pH 5.8 to 10.8. Near the IEP (pH IEP =10.8), the stability of the suspensions with PEI is dominated by the steric effect. When the pH is decreased to acid direction, the stabilization mechanism is changed from steric hindrance to an electrosteric effect little by little. PAA also has the effect of reducing the hydrolysis speed via a “buffer effect” in the basic pH range, but the lack of adsorption between the highly ionized anionic polymer molecules and the negative colloid particle surfaces shows no positive effect on hydrolysis of colloids and on the stabilization of Y 2 Si 2 O 7 suspensions.