[en] Full text: New soft polymer membranes have been developed for hydrogen fuel cells using a dry plasma process similar to that presently used in the microelectronics industry. The main advantages of plasma-produced membranes over membranes produced using wet chemistry such as Nafion are: a micrometric thickness and a very highly cross-linked structure resulting in good chemical and thermal stability. In order to optimise the plasma produced membranes, we need to establish correlations between the plasma parameters used during deposition, the micro-structural characteristics and the proton transport properties. The structures of Nafion and other proton conducting membranes have previously been studied using small and wide angle neutron and x-ray scattering (SANS and SAXSIWAXS). These studies have provided insight into the size, shape and distribution of the hydrated regions, as well as the degree of cross-linking. While a number of physical property measurements have been performed on plasma produced proton conducting membranes, their structure has not previously been studied using small or wide angle x-ray or neutron scattering techniques. We have carried out preliminary SAXS and WAXS investigations on our novel plasma polymerised membranes, with Nafion as a comparison. This data confirms that the structure of the plasma polymerised membranes is significantly different to that of Nafion. For example, in the SAXS and WAXS measurements: the Nafion ionomer peak is absent in the plasma film; nafion has a Q-1 dependency at low Q, indicating a rodlike morphology. The plasma film has I-Q-2.5, indicating a more dense film; the plasma film WAXS peaks are at higher Q than Nafion.

[en] Optimising the properties of catalysts for industrial processes requires a detailed knowledge of their structure and properties on multiple length scales. Synchrotron light sources are ideal tools for characterising catalysts for industrial R and D, providing data with high temporal and spatial resolution, under realistic operating conditions, in a non-destructive way. Here, we describe the different synchrotron techniques that can be employed to gain a wealth of complementary information, and highlight recent developments that have allowed remarkable insight to be gained into working catalytic systems. These techniques have the potential to guide future industrial catalyst design. (authors)

[en] An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO₃ at temperatures above the Curie point (T_C) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above T_C. The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above T_C, while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm⁻¹) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.

[en] Large electric-field-induced strain in piezoelectric ceramics is a primary requirement for their actuator applications. This macroscopic strain is generated from both intrinsic lattice strain and extrinsic domain switching and/or phase transformations. Among these contributions, non-180° ferroelectric domain switching can generate a large electric-field-induced strain due to the change in orientation of the coupled spontaneous strain. However, the large fraction of non-180° ferroelectric domain switching is a one-time effect during electrical poling. Here, we show that electric-field-induced non-180° ferroelectric domain switching in the microstructurally engineered material BaTiO_3–KNbO_3 (BT–KN) is largely reversible. In situ high energy X-ray diffraction showed approximately 95% reversibility in the switched fraction of non-180° ferroelectric domains during unipolar cycling. This reversibility is hypothesised to be due to the unique grain boundary structure of this material, where ferroelectric domain walls do not interact strongly with grain boundary defects. The domain switching behaviour of core–shell BT–KN has been contrasted with that of polycrystalline BaTiO_3 and commercial lead zirconate titanate Pb(Zr,Ti)O_3. The large and reversible non-180° ferroelectric domain switching of core–shell BT–KN offers a distinctive strain response. The results indicate a unique family of large strain lead-free materials based on enhanced reversible non-180° ferroelectric domain switching can be developed for future actuator applications