Effects of Spiral Magnetic Field on Structures Transformation and Macrosegregation of Sn-Pb Alloy

The effect of spiral magnetic field （SMF） on the solidification process of Sn-20 wt.%Pb hypoeutectic alloy was studied in this work. The temperature distribution and the macrosegregation together with the eutectic lamellar spacing during solidification were measured under different magnetic fields. The results indicate that the compositions in the top and bottom portions of the sample are nearly the same and the segregation phenomenon is basically eliminated by SMF at an exciting current of 125 A. The morphology of the primary phase transforms from coarse dendrite to rosette or ellipsoidal equiaxed crystal and the spacing of the eutectic lamellar increases from 1.6 to 3.9 μm when the exciting current increases from 0 to 125 A. Moreover, if the exciting current is high enough, the forced fluid flow caused by SMF will enhance the process of transition from lamellar eutectic structure to anomalous rod-like one.

One-step synthesis of carbon-coated monocrystal molybdenum oxides nanocomposite as high-capacity anode materials for lithiumion batteries

Benefitting from higher specific capacities,acceptable cost,nontoxicity and unique crystal structures,the molybdenum oxides have been studied as the anode materials for lithium ion batteries(LIBs).Herein,a direct current(DC)arc-discharge plasma technique has been developed to in-situ synthesize carboncoated monocrystal molybdenum oxides((MoO3NRs/MoO2NPs)@C)nanocomposites,using coarse MoO_(3) bulk as the raw material and methane(CH4)gas as the carbon source.It is indicated that crystallographic traits of MoO_(3) and MoO2 nuclei give rise to an anisotropic growth of monocrystal MoO3 nanorods(NRs)along<100>direction and an isotropic growth of monocrystal MoO_(2) nanoparticles(NPs).The carbon shells on MoO3/MoO2 nanostructures are generated from the absorption of carbon atoms in surrounding atmosphere or the release of supersaturated carbon atoms in MoeOeC solid solution.Unique constitution and pseudo-capacitive behavior of(MoO3NRs/MoO2NPs)@C bring merits to excellent cycling performance and rate capability,i.e.a remarkable specific capacity of 840 mAh·g^(-1) after 100 cycles at a current density of 0.1 Ag^(-1) and a retained capacity of 210 mAh·g^(-1) at 6.4 A g^(-1).This work has offered a simple and efficient approach to fabricate the carbon-coated molybdenum oxides nanostructures for promising anode materials of LIBs。