Simulation of FIB-SEM Images for Segmentation of Porous Microstructures

FIB tomography yields high quality 3D images materials microstructures at the nanometer scale combining serial sectioning using a focused ion beam with scanning electron microscopy (SEM). However, SEM images represent the projection of a slice of unknown thickness. In FIB tomography of highly porous media this leads to shine-through-artifacts preventing automatic segmentation of the solid component. To overcome these difficulties, we simulate the SEM process. Monte-Carlo techniques yield accurate results, but are too slow for FIB-SEM requiring hundreds of SEM images for one dataset. Nevertheless, a quasi analytic description of the specimen and acceleration techniques cut down the computing time by orders of magnitude, allowing the simulation of FIB-SEM data. Based on simulated FIB-SEM image data, segmentation methods for the 3D microstructure of highly porous media from the FIB-SEM data can be developed and evaluated. Finally successful segementation enables quantitati ve analysis and numerical simulations of macroscopic properties

Low pt thin cathode layer catalyst layer by reactive spray deposition technology

National Research Council Canada's Institute for Fuel Cell Innovation, NRC-IFCI, has been developing the Reactive Spray Deposition Technology (RSDT) process to optimize composite electrode layer formation and develop novel electrocatalysts and catalyst layers. The RSDT process provides the means necessary to develop the next generation of thin, low platinum or alloy catalyst layers for PEM MEA's. In order to best manage water distribution, mass transport and conductivity, the structure should be a gradient with controlled porosity and controlled distribution of both platinum and ionomer across the catalyst layer. The RSDT process allows good control of the platinum particle size as they are created directly from metal vapors, which prevents agglomeration in the catalyst layer. Additionally, it has the flexibility to build a gradient layer structure across a very thin film catalyst layer (<1 um). In our design, a platinum sub-layer (100 nm) was deposited directly on a Nafion\uae 117 membrane as a columnar structure. After the sub-layer, the platinum loading was reduced in a co-deposited layer of Pt-Nafion (ionomer)-carbon with the lowest loading closest to the GDL. The combined loading of both layers was <0.05mg/cm2 Pt with this approach. The manufactured catalyst layer has a performance of 0.65V at 1 A/cm2 with 0.05mg/cm2 Pt loading using pure oxygen.Peer reviewed: YesNRC publication: Ye