2.5.1. Characterization of membrane structure
The morphology of the membrane surfaces was characterized using a
Gemini500 (Zeiss, Germany) SEM instrument. The cross-sectional
morphology of the membranes was analyzed using a SU8220 (Hitachi, Japan)
SEM apparatus. The chemical structure of the thin surface layers was
studied using a Nicolet FTIR (Thermo Scientific, USA) spectrometer in
attenuated total reflectance (ATR) mode. The cross-sections of the
TFN-(Zr/Ti) membranes were further investigated using a JEM-2010 (JEOL,
Japan) transmission electron microscopy (TEM) device. To prepare the
membrane samples for TEM analysis, we embedded them in E44 epoxy resin.
Subsequently, 100 nm thick sections of the membranes that were cut using
an EM UC7 (Leica, Germany) ultramicrotome were transferred to a TEM
grid. The roughness of the membrane surfaces was measured using a
MultiMode V (Veeco, USA) atomic force microscopy (AFM) instrument.