2.4. Membrane characterizations
The morphological structure of as-prepared membranes was observed by
scanning electron microscope (SEM, S-4800, Hitachi, Japan). The samples
were prepared for cross-sectional observation by freeze-fracturing the
membranes in liquid nitrogen. About 2.5 nm-thick platinum layer was
coated on the surface of samples before observation using a coater
(JFC-1600, JEOL, Japan). The elemental composition of the samples was
determined by the energy dispersion spectrum (EDS) of SEM. X-ray
diffraction (XRD) spectra was acquired by XRD meter (Ultima IV, Rigaku,
Japan) with a Cu-Kα source at 40 kV and 30 mA. The d -spacing of
the membranes could be calculated from XRD spectra by
\(d=\lambda/(2sin\theta)\) (1)
where d is d -spacing (nm), λ is wavelength
(λ = 0.15 nm), θ is incidence angle (degree). Moreover,
surface hydrophilicity was determined by contact angle meter (DSA30,
Kruss, Germany).