Tensile deformation behavior of silicon ͑Si͒ wires with nanometer widths, synthesized by nanometer-tip contact and successive retraction, was studied by atomistic combined microscopy of high-resolution transmission electron microscopy/scanning probe microscopy. The elastic limit, Young's modulus, and strength of individual Si nanowires were investigated based on the mechanics of materials at an atomic scale. It was found that both Young's modulus and strength increased to 18± 2 and 5.0± 0.3 GPa, respectively. The elastic limit was 0.10± 0.02 and fracture strain was estimated to be 0.30± 0.01. Experimental results show that mechanical properties of Si wires transform due to size reduction from micrometer to nanometer scale.
We have developed a synthetic route
that uses sodium for the production
of intermetallic Pt5Ce nanoparticles (ca. 6 nm average
diameter) supported on carbon powder. Sodium melt was demonstrated
to reduce a powder mixture of PtCl2 and CeCl3 to form submicrometer Pt5Ce particles with the simultaneous
formation of NaCl. The NaCl–CeCl3 melt mixture and
Na melt were formed during heating, which led to a uniform reaction
between Pt and Ce, and the melt induced grain growth. The synthetic
procedures were then modified to supply sodium vapor to the vicinity
of the metal sources supported on carbon powder with an aim to suppress
grain growth. Pt5Ce nanoparticles were successfully formed
on the carbon support with high loading and dispersity.
Polymer/BaTiO3nanocomposites where the BaTiO3nanoparticles were isolated and uniformly dispersed by thick polymer shells, exhibited high reliability for dielectric breakdown strength.
A water-based
impregnation synthesis route was used to obtain carbon-supported
Pt–Ln (Ln: lanthanide metal) nanoparticles, which are expected
to be among the most active catalysts toward the oxygen reduction
reaction (ORR) but have previously been successfully prepared only
in environments without H2O or O2 because of
the strong oxophilicity of Ln. In the present work, a mechanistic
study of the formation of Pt–Ln nanoparticles was conducted
using Pt/C (Pt nanoparticles supported on carbon) and CeCl3 as starting materials, and the synthesized Pt–Ce/C particles
were characterized in terms of their microstructure and their electrocatalytic
activity toward the ORR. The results suggested that the impregnation-prepared
powder contained Pt, CeO2, and CeCl3 (or hydrated
CeCl3) and that these compounds transformed into Pt–Ce
and CeOCl when heated under flowing dilute H2 gas. Microstructural
analysis clarified that the obtained Pt–Ce nanoparticles (average
size: 5.5 nm) were of the intermetallic Pt5Ce phase (P6/mmm, CaCu5 type, a = 0.5368 nm, c = 0.4383 nm) and that
byproduct CeOCl was removed by successive washing. Carbon powders
supporting Pt5La, Pt5Sm, Pt–Gd (Pt5Gd and Pt2Gd), and Pt3Tb nanoparticles
were similarly obtained.
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