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Register a new userSpace Charge Influence on the Angle of Conical Spikes Developing on a Liquid-Metal Anode
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The influence of the space charge of ions emitted from the surface of a conical spike on its shape has been studied. The problem of the calculation of the spatial distributions of the electric field, ion velocity field, and the space charge density near the cone tip has been reduced to the analysis of a system of ordinary differential equations. As a result of numerical solution of these equations, the criterion of the balance of the capillary and electrostatic forces on the conic surface of a liquid-metal anode has been determined. It has allowed us to relate the electrical current flowing through the system, the applied potential difference and the cone angle. We have compared the results of our calculations with available experimental data concerning emission from the surface of pure liquid gallium (Ga), indium (In), tin (Sn), and some liquid alloys, such as Au+Si, Co+Ge, and Au+Ge. On the basis of the proposed model, explanations have been given for a number of specific features of the emissive behavior of different systems.
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Cherenkov radiation (CR) generated by a charge moving through a hollow conical target made of dielectric material is analyzed. We consider two cases: the charge moves from the base of the cone to its top (``straight cone) or from the top to the base (``inverted cone). Unlike previous papers, a nonzero shift of the charge trajectory from the symmetry axis is taken into account which leads to generation of asymmetric CR. The most interesting effect is the phenomenon of ``Cherenkov spotlight which has been reported earlier for axially symmetric problems. This effect allows essential enhancement of the CR intensity in the far-field region by proper selection of the targets parameters and charge velocity. Here we describe the influence of charge shift on CR far-field patterns paying the main attention to the ``Cherenkov spotlight regime. Influence of variation of the charge speed on this phenomenon is also investigated.
The influence of morphology on the optical properties of silver nanoparticles is studied. A general relationship between the surface plasmon resonances and the morphology of each nanoparticle is established. The optical response is investigated for cubes and decahedrons with different truncations. We found that polyhedral nanoparticles composed with less faces show more surface plasmon resonances than spherical-like ones. It is also observed that the vertices of the nanoparticles play an important role in the optical response, because the sharpener they become, the greater the number of resonances. For all the nanoparticles, a main resonance with a dipolar character was identified as well as other secondary resonances of less intensity. It is also found that as the nanoparticle becomes more symmetric, the main resonance is always blue shifted.
The initial modulation in the scheme for Coherent electron Cooling (CeC) rests on the screening of the ion charge by electrons. However, in a CeC system with a bunched electron beam, inevitably, a long-range longitudinal space charge force is introduced. For a relatively dense electron beam, its force can be comparable to, or even greater than the attractive force from the ions. Hence, the influence of the space charge field on the modulation process could be important. If the 3-D Debye lengths are much smaller than the extension of the electron bunch, the modulation induced by the ion happens locally. Then, in that case, we can approximate the long-range longitudinal space charge field as a uniform electric field across the region. As detailed in this paper, we developed an analytical model to study the dynamics of ion shielding in the presence of a uniform electric field. We solved the coupled Vlasov-Poisson equation system for an infinite anisotropic electron plasma, and estimated the influences of the longitudinal space charge field to the modulation process for the experimental proof of the CeC principle at RHIC.
Silicon is a promising candidate for negative electrodes due to its high theoretical specific capacity (~3579 mAh g-1) and low lithiation potential (~0.40 V vs Li). However, its practical applications in battery have been inhibited by the large volume change (~400%) induced by Li+-insertion into Si lattices. Here, we attempt to resolve this issue at a fundamental level, and report for the first time a novel liquid metal (LM)-mediated spontaneous repairing conductive-additive-free Si anode for Li-ion battery. The fluidity of LM ensures the eternal contact between Si and the conducting-network during its repeated electrochemical reactions. The as-prepared nano-composite of LM/Si leads to superior performances as characterized by high capacity utilization (2300 mAh g-1 at 500 mA g-1), long-term stability (968 mAh g-1 after 1500 charge-discharge cycles at 8 A g-1 with 81.3% retention), high rate capability (360 mAh g-1 at 20 A g-1, equivalence of 55 C, or full charge/discharge in 65 seconds), and, in particular, an extra-ordinarily high initial coulombic efficiency (95.92%), which is not only the highest reported for Si to the best of our knowledge, but also higher than the mature graphitic carbon anodes. The unique approach described in this work not only resolves the basic stress challenges faced by the promising but often problematic alloy-type materials; in broader context it also provides a universal inspiration to all electrode materials whose electric properties suffer from extreme mechanic upheavals induced by the electrochemical strains during the cell reactions.
A study of the relation between the electrostatic charge density at a point on a conducting surface and the curvature of the surface (at that point) is presented. Two major scientific literature on this topic are reviewed and the apparent discrepancy between them is resolved. Hence, a step is taken towards obtaining a general analytic formula for relating the charge density with surface curvature of conductors. The merit of this formula and its limitations are discussed.
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