2009, Calvimontes, A., Grundke, K., Müller, A., Stamm, M.

For a comprehensive study of Sheet Moulding Compound (SMC) surfaces, topographical data obtained by a contact-free optical method (chromatic aberration confocal imaging) were systematically acquired to characterise these surfaces with regard to their statistical, functional and volumetrical properties. Optimal sampling conditions (cut-off length and resolution) were obtained by a topographical-statistical procedure proposed in the present work. By using different length scales specific morphologies due to the influence of moulding conditions, metallic mould topography, glass fibre content and glass fibre orientation can be characterized. The aim of this study is to suggest a systematic topographical characterization procedure for composite materials in order to study and recognize the influence of production conditions on their surface quality. © 2009 by the authors.

2021, Hensling, Felix V. E., Dahliah, Diana, Dulal, Prabin, Singleton, Patrick, Sun, Jiaxin, Schubert, Jürgen, Paik, Hanjong, Subedi, Indra, Subedi, Biwas, Rignanese, Gian-Marco, Podraza, Nikolas J., Hautier, Geoffroy, Schlom, Darrell G.

We have studied the growth of epitaxial films of stannate pyrochlores with a general formula A2Sn2O7 (A = La and Y) and find that it is possible to incorporate ∼25% excess of the A-site constituent; in contrast, any tin excess is expelled. We unravel the defect chemistry, allowing for the incorporation of excess A-site species and the mechanism behind the tin expulsion. An A-site surplus is manifested by a shift in the film diffraction peaks, and the expulsion of tin is apparent from the surface morphology of the film. In an attempt to increase La2Sn2O7 conductivity through n-type doping, substantial quantities of tin have been substituted by antimony while maintaining good film quality. The sample remained insulating as explained by first-principles computations, showing that both the oxygen vacancy and antimony-on-tin substitutional defects are deep. Similar conclusions are drawn on Y2Sn2O7. An alternative n-type dopant, fluorine on oxygen, is shallow according to computations and more likely to lead to electrical conductivity. The bandgaps of stoichiometric La2Sn2O7 and Y2Sn2O7 films were determined by spectroscopic ellipsometry to be 4.2 eV and 4.48 eV, respectively. © 2021 Author(s).

2010, Calvimontes, A., Grund, K., Müller, A.

For a comprehensive study of Sheet Molding Compound (SMC) surfaces, topographical data obtained by chromatic confocal imaging were submitted systematically for the development of a profile model to understand the formation of cavities on the surface. In order to qualify SMC surfaces and to predict their coatability, a characterization of cavities is applied. To quantify the effect of surface modification treatments, a new parameter (Surface Relative Smooth) is presented, applied and probed. The parameter proposed can be used for any surface modification of any solid material. © 2010 by the authors.

2016, Waske, A., Lovell, E., Funk, A., Sellschopp, K., Rack, A., Giebeler, L., Gostin, P.F., Fähler, S., Cohen, L.F.

First order magnetocaloric materials reach high entropy changes but at the same time exhibit hysteresis losses which depend on the sample’s microstructure. We use non-destructive 3D X-ray microtomography to understand the role of surface morphology for the magnetovolume transition of LaFe11.8Si1.2. The technique provides unique information on the spatial distribution of the volume change at the transition and its relationship with the surface morphology. Complementary Hall probe imaging confirms that on a morphologically complex surface minimization of strain energy dominates. Our findings sketch the way for a tailored surface morphology with low hysteresis without changing the underlying phase transition.