Comparison of focused ion beam versus nano-scale X-ray computed tomography for resolving 3-D microstructures of porous fuel cell materials

• Published in: Journal of power sources Vol. 241; pp. 608 - 618
• Main Authors: Wargo, E.A., Kotaka, T., Tabuchi, Y., Kumbur, E.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2013; Elsevier
• Subjects: Applied sciences; Computation; Computed tomography; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Focused ion beam; Fuel cells; Microstructure; Nanocomposites; Nanomaterials; Nanostructure; Nanotomography; Polymer electrolyte fuel cell; Porous materials; Three dimensional; Tomography; Transport properties; X-ray; X-rays; Nanotomography; X-ray; Computed tomography; Microstructure; Polymer electrolyte fuel cell; Focused ion beam; Polymer electrolytes; Polymer solid electrolyte; X ray; X Ray tomography; Porous material; Focused ion beam technology; Nanometer scale; Miniaturization; Proton exchange membrane fuel cells; Solid electrolyte fuel cells; Comparative study; Fuel cell
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.04.153

Focused ion beam-scanning electron microscopy (FIB-SEM) and nano-scale X-ray computed tomography (nano-CT) have emerged as two popular nanotomography techniques for quantifying the 3-D microstructure of porous materials. The objective of this study is to assess the unique features and limitations of FIB-SEM and nano-CT in capturing the 3-D microstructure and structure-related transport properties of porous fuel cell materials. As a test case, a sample of a micro-porous layer used in polymer electrolyte fuel cells is analyzed to obtain 3-D microstructure datasets using these two nanotomography techniques. For quantitative comparison purposes, several key transport properties are determined for these two datasets, including the porosity, pore connectivity, tortuosity, structural diffusivity coefficient, and chord length (i.e., void size) distributions. The results obtained for both datasets are evaluated against each other and experimental data when available. Additionally, these two techniques are compared qualitatively in terms of the acquired images, image segmentation, and general systems operation. The particular advantages and disadvantages of both techniques are highlighted, along with suggestions for best practice. •Unique features and limitations of FIB-SEM and nano-CT techniques are compared.•A sample of MPL used in PEFC is selected for characterization and comparison.•Acquired images, segmentation and resulting 3D reconstructions are analyzed.•Structure-related properties calculated from these 3D datasets are compared.•Several items for consideration are highlighted to promote best practices.