Nano-crystalline FeOOH particles （5-10 nm） have been uniformly mixed with electric matrix of single-walled carbon nanotubes （SWNTs） for forming FeOOH/SWNT composite via a facile ultrasonication method. Directly using the FeOOH/SWNT composite （containing 15 wt% SWNTs） as anode material for lithium battery enhances kinetics of the Li＋ insertion/extraction processes, thereby effectively improving re- versible capacity and cycle performance, which delivers a high reversible capacity of 758 mAh.g-1 under a current density of 400 mA.g-1 even after 180 cycles, being comparable with previous reports in terms of electrochemical performance for FeOOH anode. The good electrochemical performance should be ascribed to the small particle size and nano-crystalline of FeOOH, as well as the good electronic conductivity of SWNT matrix.
Conducting supporters of purified single-walled carbon nanotubes（SWNTs） and graphene oxide（GO）were used to confine pomegranate-structured Sn O2 nanospheres for forming SnO-GO-SWNT composites.As anode material for lithium ion batteries（LIBs）, this composite exhibits a stable and large reversible capacity together with an excellent rate capability. In addition, an analysis of the AC impedance spectroscopy has been used to confirm the enhanced mechanism for LIB performance. The improved electrochemical performance should be ascribed greatly to the reinforced synergistic effects between GO and SWNT networks, and their enhanced contribution of the conductivity. These results indicate that this composite has potential for utilization in high-rate and durable LIBs.
Based on Monte Carlo simulations,the effect of structural configuration on the hysteresis behavior and tunneling magnetoresistance(TMR) of composite nanoparticles with ferromagnetic(FM) core/anti-ferromagnetic(AFM) shell is investigated.The simulated results indicate that the coercive field(H c) of composites increases with the decreasing ratio of core-radius(r core) to shell-radius(r shell).When the ratio of r shell to r core is approaching 4:3,H c decreases with increasing AFM thickness.In addition,TMR is found to increase with the decreasing ratio of r core to r shell,resulting from the enhancement of resistance changes in disordered AFM shell.
The structural stability, vibrational and magnetic properties of hydrogen doped ZnO:Co have been studied by first-principles calculations based on density functional theory. Bond-center(BC) sites were identified to be most stable sites for hydrogen, the corresponding vibrational frequencies including anharmonic contributions were calculated. Its magnetic properties were investigated as well. The calculated results reveal that hydrogen could induce the change of electronic transfer, leading to a decrease of magnetic moment. However, the magnetic coupling between Co atoms is greatly strengthen. The results simulated by Monte Carlo method indicate that hydrogen can induce the Curie temperature to increase from 200 to 300 K.
