Recent advances in the characterization of membrane morphology

• Recent advances in characterizing porous and dense membranes are reviewed.
• Newly developed SRμCT, SRnTXM and PAS techniques are introduced.
• Current challenges on membrane morphology characterization are described.

The characterization of membranes is important for membrane selection, membrane process diagnosis, and new membrane material design. Recent advances in membrane characterization techniques facilitate new membrane material design and accelerate the development of new applications of membrane technology. We divide this review into two main parts: porous membrane and dense membrane characterizations. In the first part, recent advances in the pore size and pore size distribution in porous membranes and in the in situ characterization of the three dimensional morphology of porous membranes are discussed. Newly developed characterization techniques, including nano-permporometry, evapoporometry, and synchrotron radiation X-ray tomography, are introduced. In the second part, recent advances in the characterization of the free volume and free volume distribution in dense membranes and membrane swelling effects. Newly developed characterization techniques such as positron annihilation spectroscopy and spectroscopic ellipsometry, are introduced.