44,331 research outputs found
The influence of compact and ordered carbon coating on solid-state behaviors of silicon during electrochemical processes
To address the issues of large volume change and low conductivity of silicon (Si) materials, carbon coatings have been widely employed as surface protection agent and conductive medium to encapsulate the Si materials, which can improve the electrochemical performance of Si-based electrodes. There has been a strong demand to gain a deeper understanding of the impact of efficient carbon coating over the lithiation and delithiation process of Si materials. Here, we report the first observation of the extended two-phase transformation of carbon-coated Si nanoparticles (Si/C) during electrochemical processes. The Si/C nanoparticles were prepared by sintering Si nanoparticles with polyvinylidene chloride precursor. The Si/C electrode underwent a two-phase transition during the first 20 cycles at 0.2 C, but started to engage in solid solution reaction when the ordered compact carbon coating began to crack. Under higher current density conditions, the electrode was also found to be involved in solid solution reaction, which, however, was due to the overwhelming demand of kinetic property rather than the breaking of the carbon coating. In comparison, the Si/C composites prepared with sucrose possessed more disordered and porous carbon structures, and presented solid solution reaction throughout the entire cycling process
A Critical Examination to the Unitarized Scattering Chiral Amplitudes
We discuss the Pad\'e approximation to the scattering amplitudes in
1--loop chiral perturbation theory. The approximation restores unitarity and
can reproduce the correct resonance poles, but the approximation violates
crossing symmetry and produce spurious poles on the complex plane and
therefore plagues its predictions on physical quantities at quantitative level.
However we find that one virtual state in the IJ=20 channel may have physical
relevance.Comment: 13 pages + 4 eps figures submit to Commun. Theor. Phy
Measuring the phonon-assisted spectral function by using a non-quilibrium three-terminal single-molecular device
The electron transport through a three-terminal single-molecular transistor
(SMT) is theoretically studied. We find that the differential conductance of
the third and weakly coupled terminal versus its voltage matches well with the
spectral function versus the energy when certain conditions are met.
Particularly, this excellent matching is maintained even for complicated
structure of the phonon-assisted side peaks. Thus, this device offers an
experimental approach to explore the shape of the phonon-assisted spectral
function in detail. In addition we discuss the conditions of a perfect
matching. The results show that at low temperatures the matching survives
regardless of the bias and the energy levels of the SMT. However, at high
temperatures, the matching is destroyed.Comment: 9 pages, 5 figure
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