2 research outputs found
Growth of Cuprous Oxide Particles in Liquid-Phase Synthesis Investigated by X‑ray Laser Diffraction
Cuprous oxide (Cu<sub>2</sub>O) particles obtained by surfactant-assisted
liquid-phase synthesis have cuboid shapes but the internal structures
are difficult to be visualized by electron microscopy. Herein, we
investigated the internal structures of numerous individual Cu<sub>2</sub>O particles with submicrometer dimensions by X-ray diffraction
imaging (XDI) using X-ray free-electron laser (XFEL) pulses. The reconstructed
two-dimensional electron density maps, which displayed inhomogeneous
internal structures, were divided into five classes characterized
by the positions and shapes of high and low electron density areas.
Further analysis of the maps in each class by a manifold learning
algorithm revealed that the internal structures of Cu<sub>2</sub>O
particles varied in correlation with total electron density while
retaining the characteristics within each class. On the basis of the
analyses, we proposed a growth mechanism to yield the inhomogeneity
in the internal structures of Cu<sub>2</sub>O particles in surfactant-mediated
liquid-phase synthesis
Controlled Terahertz Birefringence in Stretched Poly(lactic acid) Films Investigated by Terahertz Time-Domain Spectroscopy and Wide-Angle X‑ray Scattering
We
report a correlation between the dielectric property and structure
of stretched polyÂ(lactic acid) (PLA) films, revealed by polarization-sensitive
terahertz time-domain spectroscopy and two-dimensional (2D) wide-angle
X-ray scattering (WAXS). The experiments evidence that the dielectric
function of the PLA film becomes more anisotropic with increasing
draw ratio (DR). This behavior is explained by a classical Lorentz
oscillator model assuming polarization-dependent absorption. The birefringence
can be systematically altered from 0 to 0.13 by controlling DR. The
combination of terahertz spectroscopy and 2D WAXS measurement reveals
a clear correlation between the birefringence in the terahertz frequency
domain and the degree of orientation of the PLA molecular chains.
These findings imply that the birefringence is a result of the orientation
of the PLA chains with anisotropic macromolecular vibration modes.
Because of a good controllability of the birefringence, polymer-based
materials will provide an attractive materials system for phase retarders
in the terahertz frequency range