101,009 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
Scaling of nuclear modification factors for hadrons and light nuclei
The number of constituent quarks (NCQ-) scaling of hadrons and the number of
constituent nucleons (NCN-) scaling of light nuclei are proposed for nuclear
modification factors () of hadrons and light nuclei, respectively,
according to the experimental investigations in relativistic heavy-ion
collisions. Based on coalescence mechanism the scalings are performed for pions
and protons in quark level, and light nuclei and He for
nucleonic level, respectively, formed in Au + Au and Pb + Pb collisions and
nice scaling behaviour emerges. NCQ or NCN scaling law of can be
respectively taken as a probe for quark or nucleon coalescence mechanism for
the formation of hadron or light nuclei in relativistic heavy-ion collisions.Comment: 6 pages, 6 figure
Sensitivity of neutron to proton ratio toward the high density behavior of symmetry energy in heavy-ion collisions
The symmetry energy at sub and supra-saturation densities has a great
importance in understanding the exact nature of asymmetric nuclear matter as
well as neutron star, but, it is poor known, especially at supra-saturation
densities. We will demonstrate here that the neutron to proton ratios from
different kind of fragments is able to determine the supra-saturation behavior
of symmetry energy or not. For this purpose, a series of Sn isotopes are
simulated at different incident energies using the Isospin Quantum Molecular
Dynamics (IQMD) model with either a soft or a stiff symmetry energy for the
present study. It is found that the single neutron to proton ratio from free
nucleons as well as LCP's is sensitive towards the symmetry energy, incident
energy as well as isospin asymmetry of the system. However, with the double
neutron to proton ratio, it is true only for the free nucleons. It is possible
to study the high density behavior of symmetry energy by using the neutron to
proton ratio from free nucleons.Comment: 11 Pages, 9 Figure
Conditions for Nondistortion Interrogation of Quantum System
Under some physical considerations, we present a universal formulation to
study the possibility of localizing a quantum object in a given region without
disturbing its unknown internal state. When the interaction between the object
and probe wave function takes place only once, we prove the necessary and
sufficient condition that the object's presence can be detected in an initial
state preserving way. Meanwhile, a conditioned optimal interrogation
probability is obtained.Comment: 5 pages, Revtex, 1 figures, Presentation improved, corollary 1 added.
To appear in Europhysics Letter
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