DBC SANS diffractometer DN-2

1. neutron source DBC SANS diffractometer DN-2 • high Q-resolution SANS • fully asymmetric diffraction geometry • => 1-d PSD can be employed • tunable resolution (10-4 - 10-3 Å-1) • absolute calibration: direct beam • automatic mode holder 1-d

2. Characterizing nanoporous material from Ni-base superalloy CMSX4 NPL_1007: R. Gilles (TU Muenchen), D. Mukherji (TU Braunschweig), local contact P. Strunz • 1. self-assembly of γ’ precipitates in superalloys during thermo-mechanical exposure – rafting • 2. selective phase dissolution using electrochemical etching • => nanoporous material (fine open porosity, regularity) • Prospective applications: separation processes, catalytic substrate, miniature heat exchangers, gas permeable membranes • fabrication optimization (electrolyte, mode, potential): the pore-depth dependence on the etching time? Saturation (increasingly difficult transport)? • Technique: high-resolution SANS

3. Etching time 0 h 4 h 6.5 h 14 h 48 h SANS for galvanostatic etching Depth evolution with time white: γ-phase; gray: γ'-precipitates; black: pores Models (optimum fit) • The depth evolution with etching time determined • The galvanostatic mode of γ-phase dissolution visibly faster • Dissolution very significantly decelerated approximately after 24 hours of the galvanostatic etching (saturation at ≈330 μm) • Pore volume fraction increase (due to <100% selectivity of etching) For details see: P.Strunz, D.Mukherji, O.Näth, R.Gilles, J.Rösler, Physica B (2006) 385, 626-629