Ultra-fine ceramic powders, particularly the nano-sized powders,
have aroused increasing attention due to their unique
functional properties and significance in ceramic processing.
Various recently developed wet chemical methods have been
demonstrated to be handy and effective techniques to prepare
high-quality ultra-fine powders. However, multifarious anions
or/and cations in the solution need to be removed after synthesis
of the powder precursors. Nano-sized particles tend to form
large agglomerates due to their small grain size, large specific surface
area and strong surface physicochemical interaction (Sung,
Choi, Kim, & Kim, 2000). Traditional techniques used for washing
and removing the residual ions, such as the plate-and-frame
filter and centrifugal separation, are based on unidirectional flux
through the filtration medium. The compact filtration cake not only
blocks the filter fabric, leading to rapid reduction in filtration rate,
but also encapsulates impurity ions, that is, time-consuming and
highly cost-ineffective. Washing with the use of a membrane, as
a cross-flow separation devise for nano-sized powder preparation,
has recently been recognized to be a novel and effective technique
with unique characteristics and promise for extensive applications