Ancient Jian wares are famous for their lustrous black glaze that exhibits unique colored
patterns. Some striking examples include the brownish colored “Hare's Fur” (HF) strips and
the silvery “Oil Spot” (OS) patterns. Herein, we investigated the glaze surface of HF and OS
samples using a variety of characterization methods. Contrary to the commonly accepted
theory, we identified the presence of ε-Fe2O3, a rare metastable
polymorph of Fe2O3 with unique magnetic properties, in both HF and OS
samples. We found that surface crystals of OS samples are up to several micrometers in size
and exclusively made of ε-Fe2O3. Interestingly, these
ε-Fe2O3 crystals on the OS sample surface are organized in a
periodic two dimensional fashion. These results shed new lights on the actual mechanisms and
kinetics of polymorphous transitions of Fe2O3. Deciphering
technologies behind the fabrication of ancient Jian wares can thus potentially help
researchers improve the ε-Fe2O3 synthesis.
Stress transfer within double‐walled nanotubes (DWNTs) in a composite is followed from stress‐induced Raman band shifts. It is shown that the Raman G′ band is split into two components, one from each wall. It is found that only the G′ component from the outer wall shifts with stress, and that this will limit the ability of multiwalled nanotubes to reinforce composites.
Encapsulated C 70 molecules packed in single-walled carbon nanotubes display different orientations depending on the nanotube radius. We present x-ray scattering data obtained on a powder of nanotubes filled with C 70 molecules. Analytical expressions for calculating the diffraction diagram taking into account fullerene orientations are developed. The comparison between calculations and experiments allows us to conclude that the change from the lying to standing orientation-corresponding to the molecule long axis parallel and perpendicular to the tube axis, respectively-takes place when nanotubes reach a diameter of about 1.42 nm. Energy calculations are performed using a Lennard-Jones ͑6-12͒ potential, leading to a calculated reorientation diameter in good agreement with that determined experimentally.
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