Instantaneous formation of SiOx nanocomposite for high capacity lithium ion batteries by enhanced disproportionation reaction during plasma spray physical vapor deposition.

Nanocomposite SiOx particles have been produced by a single step plasma spray physical vapor deposition (PS-PVD) through rapid condensation of SiO vapors and the subsequent disproportionation reaction. Core-shell nanoparticles, in which 15 nm crystalline Si is embedded within the amorphous SiOx matrix, form under typical PS-PVD conditions, while 10 nm amorphous particles are formed when processed with an increased degree of non-equilibrium effect. Addition of CH4 promotes reduction in the oxygen content x of SiO x , and thereby increases the Si volume in a nanocomposite particle. As a result, core-shell nanoparticles with x = 0.46 as anode exhibit increased initial efficiency and the capacity of lithium ion batteries while maintaining cyclability. Furthermore, it is revealed that the disproportionation reaction of SiO is promoted in nanosized particles attaining increased Si diffusivity by two orders of magnitude compared to that in bulk, which facilitates instantaneous composite nanoparticle formation during PS-PVD.

Universal structure of two- and three-dimensional self-gravitating systems in the quasiequilibrium state.

We study a universal structure of two- and three-dimensional self-gravitating systems in the quasiequilibrium state. It is shown numerically that the two-dimensional self-gravitating system in the quasiequilibrium state has the same kind of density profile as the three-dimensional one, especially when null virial conditions are fulfilled. It is unveiled why the conditions are necessary for the universal structure by the envelope equation. We develop a phenomenological model to describe this universal structure by using a special Langevin equation with a distinctive random noise to self-gravitating systems. We find that the density profile derived theoretically is very consistent with results of observations and simulations.

Helical mechanoclinic deformation of main-chain chiral smectic elastomers.

The helical mechanoclinic deformation of a main-chain chiral smectic elastomer, which is prepared by a crosslinking reaction under twist deformation, is investigated. The twist deformation induces a layer tilt angle that depends on the handedness of twist. The layer tilt angle in the right-handedly twisted elastomer, of which the handedness is consistent with that of the helix in the SmC* phase of the non-crosslinked backbone polymer, is estimated to be up to 16° at room temperature, although that in the left-handedly twisted elastomer is less than several degrees. The experiments provide evidence of chiral coupling between tilt and twist for helical mechanoclinic deformation in the chiral smectic system.

Self-organized relaxation in a collisionless gravitating system.

We propose the self-organized relaxation process which drives a collisionless self-gravitating system to the equilibrium state satisfying local virial (LV) relation. During the violent relaxation process, particles can move widely within the time interval as short as a few free-fall times, because of the effective potential oscillations. Since such particle movement causes further potential oscillations, it is expected that the system approaches the critical state where such particle activities, which we call gravitational fugacity, is independent of the local position as much as possible. Here we demonstrate that gravitational fugacity can be described as the functional of the LV ratio, which means that the LV ratio is a key ingredient estimating the particle activities against gravitational potential. We also demonstrate that the LV relation is attained if the LV ratio exceeds the critical value b=1 everywhere in the bound region during the violent relaxation process. The local region which does not meet this criterion can be trapped into the presaturated state. However, small phase-space perturbation can bring the inactive part into the LV critical state.