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Microphase-separated structures in poly(styrene-block-isoprene) (SI) block copolymer thin films were investigated by transmission electron microtomography (TEMT). The SI block copolymer showed cylindrical microdomains in the bulk state. Several block copolymer thin films with different thicknesses were prepared by spin-coating and were extensively annealed before the TEMT experiments. Intriguingly, although the cylindrical morphology orienting parallel to the substrate was observed in most of the cases, spherical microdomains were found at certain film thicknesses. The thickness dependence was investigated using a computer simulation based on the self-consistent-field theory, producing a morphological phase diagram based on minimizing free energy. We find that the distortion of the hexagonal lattice of the cylindrical microdomains caused the morphological transition to the spherical microdomains.

Microphase-separated structures of a poly(deuterated styrene-block-2-vinylpyridine) (dPS-b-P2VP) block copolymer in thin films were studied by neutron reflectivity (NR) and transmission electron microtomography (TEMT). The dPS-b-P2VP block copolymer shows a cylindrical morphology in the bulk state. The block copolymer was spun-coated on a Si substrate, which was extensively annealed (170 °C for 14 days) before the NR experiments. The annealed thin film showed a featureless NR profile, the reflectivity monotonically decreased with the increasing scattering vector along the depth direction of the thin film, qz. The portion of the dPS-b-P2VP block copolymer thin film used in the NR experiment was examined by TEMT, from which a three-dimensional (3D) morphology of the block copolymer thin film was successfully obtained. The 3D image clearly showed that the microphase-separated structure inside the thin film had a cylindrical morphology with some order along the depth, but almost no in-plane order. In order to...

The Fuel Cell Electrode (FCE), consisting of platinum particles or platinum alloy particles supported on carbon substrates, is one of the key components in the polymer electrolyte fuel cells (PEFCs). In order for the detailed characterization, it is crucial to determine three-dimensional (3D) morphologies of Pt nanoparticles on carbon substrates (Pt/C). In this communication, 3D structures of Pt/C with two different kinds of substrates have been examined using a nano-scale 3D imaging technique, transmission electron microtomography. It was found that the TEC10V50E had Pt catalytic nanoparticles located only at the substrate surface, while the TEC10E50E showed Pt nanoparticles both inside and at the surface of the carbon substrate.

The polymer fuel cell electrode (PFCE), consisting of platinum particles or platinum alloy particles supported on carbon particles and proton-conducting ionomer binder, is one of the most important components in the fuel cell. The three-dimensional (3-D) imaging technique is important for the precise characterization of the carbon-supported catalysts and the electrode. In this study, the Pt particles as the catalysts supported on different kinds of carbon particles were examined by transmission electron microtomography (TEMT) to obtain the first 3-D structure of the carbon-supported catalyst and to then evaluate the significant parameters that should allow characterization of the catalyst, i.e., the Pt nanoparticles supported on high-surface area carbons. To obtain quantitative 3-D images of the catalysts that contain extremely small Pt particles on the order of a few nanometers in diameter, a special sample preparation technique was developed for the TEMT experiments. As a result, the spatial resolution of ca 0.5 nm was achieved for the first time. On the basis of such very quantitative 3-D images, a series of 3-D image analysis algorithms were developed and used to evaluate significant structural parameters, e.g., the size and spatial distribution of the Pt particles on the carbon substrate, the “degree of embeddedness” of Pt into the carbon support, and the effective surface area of the catalyst per unit volume. These morphological parameters are useful in characterizing fuel cell catalysts and may be significant in studying the degradation mechanisms of catalysts during operation if they are examined before and after the operation. Keywords: catalysts; fuel cell; Pt particles; 3-D; transmission electron microtomography

The high resolution Transmission Electron Microtomography (TEMT) for characterization of grains in a Cu sub-100nm line was firstly reported. A new sample preparation method was developed for obtaining TEM projections from the tilted sample from −90 to +90 degrees. A Cu grain structure was become clear by the 3D TEMT. Furthermore grooving at the surface and micro voids of a few nm were found at the grain boundaries.