@article{ChenMuellerLebedevetal.2019,
  author    = {Chen, Cong and M{\"u}ller, Bernd Randolf and Lebedev, Oleg I. and Giovannelli, Fabien and Bruno, Giovanni and Delorme, Fabian},
  title     = {Effects of impurities on the stability of the low thermal conductivity in Fe2TiO5 ceramics},
  series = {Materials characterization},
  volume    = {149},
  journal   = {Materials characterization},
  publisher = {Elsevier},
  address   = {New York},
  issn      = {1044-5803},
  doi       = {10.1016/j.matchar.2019.01.021},
  pages     = {111 -- 117},
  year      = {2019},
  abstract  = {The stability of the low thermal conductivity in Fe2TiO5 pseudobrookite ceramics has been studied. An increase in thermal diffusivity is observed after only three cycles of measurement. X-ray refraction shows an increase in the mean value of specific surface after the thermal diffusivity measurements. By using scanning electron microscopy and high-angle annular dark-field scanning transmission electron microscope equipped with energy dispersive Xray spectroscopy, we observe a segregation of Ca- and F-rich nanocrystals at grain boundaries after three cycles of thermal diffusivity measurement. Therefore, impurities seem to be more efficient to scatter phonons as point defects in the pseudobrookite lattice rather than as nanocrystals at pseudobrookite grain boundaries. This emphasizes the importance of precursor purity and the influence of redistribution of impurities on thermoelectric properties: stability of micro-/nano-structures is a key point, and repeated thermoelectric measurements may allow detecting such metastable micro-/nano-structures and producing stable and reliable data.},
  language  = {en}
}
@article{MuellerCooperLangeetal.2017,
  author    = {M{\"u}ller, B. R. and Cooper, R. C. and Lange, A. and Kupsch, Andreas and Wheeler, M. and Hentschel, M. P. and Staude, A. and Pandey, A. and Shyam, A. and Bruno, Giovanni},
  title     = {Stress-induced microcrack density evolution in beta-eucryptite ceramics},
  series = {Acta materialia},
  volume    = {144},
  journal   = {Acta materialia},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {1359-6454},
  doi       = {10.1016/j.actamat.2017.10.030},
  pages     = {627 -- 641},
  year      = {2017},
  abstract  = {In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics.},
  language  = {en}
}
@article{ChenMuellerPrinzetal.2020,
  author    = {Chen, Cong and M{\"u}ller, Bernd R. and Prinz, Carsten and Stroh, Julia and Feldmann, Ines and Bruno, Giovanni},
  title     = {The correlation between porosity characteristics and the crystallographic texture in extruded stabilized aluminium titanate for diesel particulate filter applications},
  series = {Journal of the European Ceramic Society},
  volume    = {40},
  journal   = {Journal of the European Ceramic Society},
  number    = {4},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0955-2219},
  doi       = {10.1016/j.jeurceramsoc.2019.11.076},
  pages     = {1592 -- 1601},
  year      = {2020},
  abstract  = {Porous ceramic diesel particulate filters (DPFs) are extruded products that possess macroscopic anisotropic mechanical and thermal properties. This anisotropy is caused by both morphological features (mostly the orientation of porosity) and crystallographic texture. We systematically studied those two aspects in two aluminum titanate ceramic materials of different porosity using mercury porosimetry, gas adsorption, electron microscopy, X-ray diffraction, and X-ray refraction radiography. We found that a lower porosity content implies a larger isotropy of both the crystal texture and the porosity orientation. We also found that, analogous to cordierite, crystallites do align with their axis of negative thermal expansion along the extrusion direction. However, unlike what found for cordierite, the aluminium titanate crystallite form is such that a more pronounced (0 0 2) texture along the extrusion direction implies porosity aligned perpendicular to it.},
  language  = {en}
}