Jiazheng Wang

Cu–Ge core–shell nanowire arrays as three-dimensional electrodes for high-rate capability lithium-ion batteries

We demonstrate the synthesis of three-dimensional Cu–Ge core–shell nanowire array electrodes by directly depositing Ge on the surface of pre-synthesized Cu nanowire arrays via an rf-sputtering method. When used as anodes of lithium-ion batteries, the Cu–Ge nanowire arrays display a high capacity of 1419 mAh g−1 at 0.5 C after 40 cycles and 734 mAh g−1 at 60 C after 80 cycles, which is better than planar electrodes. The improved performance can be attributed to the good electrical contact, fast electron transport and good strain accommodation of the nanowire array electrodes. The effect of the thickness of Ge layer on the electrochemical performance of the three-dimensional electrodes has also been investigated.

Synthesis of nanoporous three-dimensional current collector for high-performance lithium-ion batteries

We demonstrate the synthesis of Cu nanoporous three-dimensional current collector via a simple template-assisted method. Silicon, germanium and tin are selected as the anode materials to illustrate the enhanced performance. When tested as electrodes in lithium-ion batteries, they all show high reversible capacity with excellent rate performance. The three-dimensional nanostructure allows for good accommodation of the volume change and ensures a large surface area contact with active material and enhances the conductivity, which should be responsible for the enhanced performance.

Investigation of tin penetration at bottom surface of float borosilicate glasses

Abstract Tin penetration at the bottom surface of float borosilicate glasses was studied. The changes of tin penetration depth with different reaction temperatures and times were studied by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The results showed that tin penetration layer could not be observed until 850°C. The tin penetration depth increased with increasing reaction temperature from 850 to 950°C, while it decreased with further increasing temperature from 950 to 1050°C. X-ray photoelectron spectroscopy (XPS) was employed to study the mechanism of the decrease occurred from 950 to 1050°C. The coexistence of Sn0 and Sn2+ ions and the changes of relative concentration ratio between them in the tin penetration layer were investigated by XPS.

Cavitation study of a pump-turbine at turbine mode with critical cavitation coefficient condition

To study the cavitation phenomenon of a pump-turbine at turbine mode when it ran at the critical cavitation coefficient condition, a high-head model pump-turbine was disperse using hexahedron grid. Three dimensional, steady cavitating flow was numerically studied using SST k-ω model. It is confirmed that ZGB cavitation model and SST k-ω model are useful ways to study the two-phase cavitation flow in pump-turbine. Mass flow inlet and pressure outlet were specified at the casing inlet and draft tube outlet, respectively. The static pressure was set according to the cavitation coefficient. The steady cavitating flows at critical cavitation coefficient condition were analysed. The cavitation area in the runner was investigated. It was found that the pressure of the suction on the blade surface was decreasing gradually with the decrease of the cavitation coefficient. In addition, the vortex flow in the draft tube was observed at the critical cavitation coefficient. It was found that the vortex flow appeared at the center of the draft tube inlet with the decreasing of the cavitation coefficient. Compared with the experimental data, the simulation results show reasonable agreement with the experimental data.