Preparation of Cross-Sectional Membrane Samples for Scanning Electron Microscopy Characterizations Using a New Frozen Section Technique

Hongyun Ren; Xian Zhang; Yi Li; Dandan Zhang; Fuyi Huang; Zixing Zhang

doi:10.3390/membranes13070634

Preparation of Cross-Sectional Membrane Samples for Scanning Electron Microscopy Characterizations Using a New Frozen Section Technique

Membranes (Basel). 2023 Jun 29;13(7):634. doi: 10.3390/membranes13070634.

Authors

Hongyun Ren^{1

2}, Xian Zhang^{1

2}, Yi Li³, Dandan Zhang^{1

2}, Fuyi Huang^{1

2}, Zixing Zhang^{1

2}

Affiliations

¹ Center of Analytical Instrument, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
² Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
³ School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China.

Abstract

Characterization of the cross-sectional morphologies of polymeric membranes are critical in understanding the relationship of structure and membrane separation performances. However, preparation of cross-sectional samples with flat surfaces for scanning electron microscopy (SEM) characterizations is challenging due to the toughness of the non-woven fabric support. In this work, a new frozen section technique was developed to prepare the cross-sectional membrane samples. A special mold was self-designed to embed membranes orientationally. The frozen section parameters, including the embedding medium, cryostat working temperature, and sectioning thickness were optimized. The SEM characterizations demonstrated that the frozen section technique, using ultrapure water as the embedding medium at a working temperature of -30 °C and a sectioning thickness of 0.5 µm, was efficient for the preparation of the membrane samples. Three methods of preparation for the cross-sectional polymeric membranes, including the conventional liquid nitrogen cryogenic fracture, the broad ion beam (BIB) polishing, and the frozen section technique were compared, which showed that the modified frozen section method was efficient and low cost. This developed method could not only accelerate the development of membrane technology but also has great potential for applications in preparation of other solid samples.

Keywords: embedding medium; embedding mold; frozen section technique; polymeric membrane; preparation of membrane cross-sections; scanning electron microscopy.

Grants and funding

This work was funded by the Experimental Techniques and Methods Innovation Project of the Nanjing Regional Centre for Large Scale Instruments for Earth Resources and Environment, Chinese Academy of Sciences (Y8I0771E10).