Formation of contact and multiple cyclic cassiterite twins in SnO-based ceramics co-doped with cobalt and niobium oxides.

Contact and multiple cyclic twins of cassiterite commonly form in SnO-based ceramics when SnO is sintered with small additions of cobalt and niobium oxides (dual doping). In this work, it is shown that the formation of twins is a two-stage process that starts with epitaxial growth of SnO on CoNbO and CoNbO seeds (twin nucleation stage) and continues with the fast growth of (101) twin contacts (twin growth stage). Both secondary phases form below the temperature of enhanced densification and SnO grain growth; CoNbO forms at ∼700°C and CoNbO at ∼900°C.

Interplay between crosslinking and ice nucleation controls the porous structure of freeze-dried hydrogel scaffolds.

Freeze-drying is a process of choice to texture hydrogel scaffolds with pores formed by an ice-templating mechanism. Using state-of-the-art microscopies (cryo-EBSD, μCT, CLSM), this work evidences and quantifies the effect of crosslinking and ice nucleation temperature on the porous structure of thin hydrogel scaffolds freeze-dried at a low cooling rate. We focused on a polysaccharide-based hydrogel and developed specific protocols to monitor or trigger ice nucleation for this study.

Twinning in SnO-based ceramics doped with CoO- and NbO: morphology of multiple twins revealed by electron backscatter diffraction.

Electron backscatter diffraction (EBSD) was used for the analysis of multiple cyclic twins in cassiterite (SnO), which form during sintering of SnO with small additions of CoO and NbO. Grain misorientation analysis has shown that about one third of all grains contain {101} twin boundaries (TBs). The majority of these grains are contact twins, whereas a small fraction of grains are multiple, mainly cyclic twins.

Mechanisms of pore formation in hydrogel scaffolds textured by freeze-drying.

Whereas freeze-drying is a widely used method to produce porous hydrogel scaffolds, the mechanisms of pore formation involved in this process remained poorly characterized. To explore this, we focused on a cross-linked polysaccharide-based hydrogel developed for bone tissue engineering. Scaffolds were first swollen in 0.

Investigation of nucleation processes during dynamic recrystallization of ice using cryo-EBSD.

Nucleation mechanisms occurring during dynamic recrystallization play a crucial role in the evolution of microstructures and textures during high temperature deformation. In polycrystalline ice, the strong viscoplastic anisotropy induces high strain heterogeneities between grains which control the recrystallization mechanisms. Here, we study the nucleation mechanisms occurring during creep tests performed on polycrystalline columnar ice at high temperature and stress (T=-5°C;σ=0.

Disclinations provide the missing mechanism for deforming olivine-rich rocks in the mantle.

Mantle flow involves large strains of polymineral aggregates. The strongly anisotropic plastic response of each individual grain in the aggregate results from the interactions between neighbouring grains and the continuity of material displacement across the grain boundaries. Orthorhombic olivine, which is the dominant mineral phase of the Earth's upper mantle, does not exhibit enough slip systems to accommodate a general deformation state by intracrystalline slip without inducing damage.