Lian Chen

Synthesis of β-Ga2O3 nanorods

Abstract β-Ga 2 O 3 nanorods with diameters of 10–60 nm were synthesized through a simple gas reaction method and were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The SEM image showed that most of the nanorods were straight. XRD, SAED and HRTEM indicated that the nanorods were monoclinic Ga 2 O 3 single crystals.

Advanced nanocrystalline Zr-based AB2 hydrogen storage electrode materials for NiMH EV batteries

The metallurgical microstructure, crystal-structure and electrochemical properties of Laves phase Zr-V-Mn-Ni system alloys (modified with Ti, Co, Sn, etc.) were investigated systematically in the present paper. Conventional polycrystalline Zr-based alloys, which consist of cubic C15 Laves phase, hexagonal C14 Laves phase and non-laves phase (such as Zr7Ni10, Zr9Ni11, Zr(NiMn)Sn-0.35), show the highest discharge capacity of 342 mAh g(-1) (at 60 mA g(-1) charge-discharge current), which decreases by 7.8% after 300 cycles. Amorphous phase alloys in melt-spun alloys exhibit poor electrochemical properties. Advanced nanocrystalline C15-Laves single-phase alloys were prepared by completely crystallizing the melt-spun amorphous Zr1-xTix[(NiVMnCo)(1-nu)Sn-nu](2+alpha) alloys. These alloys have a special microstructure composed of high-density interface phase and random-oriented grains varying from several nanometres to several dozens of nanometres. It was found that these materials had high discharge capacity (the maximum capacity is up to 379 mAh g(-1)) and long cycle life (the capacity only decreases 3% after 300 cycles). The maximum discharge capacities were found in the metallurgical microstructure and crystal-structure in Zr-based AB(2) alloys. The maximum discharge capacity increases in regular nanocrystalline/C15-Laves single-phase>polycrystalline/multi-phase (Laves and non-laves)>comorphous state/C15-Laves single-phase. It was shown that the complete crystallization method from amorphous solids is an effective way to greatly improve the electrochemical performance of Zr-based AB(2) hydrogen storage electrode materials, which is not only significant for academic research but also valuable for practical applications in the NiMH battery system for pure electric vehicles (PEV) and hybrid electric vehicles (HEV)

Microstructure, electrochemical performance and gas-phase hydrogen storage property of Zr0.9Ti0.1[(Ni,V,Mn)(0.95)Co-0.05](alpha) laves phase alloys

A series of Zr0.9Ti0.1 [(NiVMn)(0.95)Co-0.05](alpha) alloys were prepared by vacuum induction melting to investigate the relationship between the composition and the electrochemical performance of AB, alloys. It was shown that the electrochemical capacity is improved, but the cycle life is reduced, when increasing the content of Mn and decreasing that of Ni in the alloys, keeping the contents of the other elements constant. The electrochemical capacity is increased, but the high-rate capability deteriorated with the increasing level of the V and the decrease of Ni in the alloys. The effects are attributed to the electro-catalyzing effect of Ni, the dissolution of Mn into the alkaline solution and the change of hydrogen affinity resulting from the substitution of V for Ni

Modification of a rapidly solidified hydrogen storage electrode alloy by ball-milling with Co3Mo

Rapidly solidified hydrogen storage alloys were reported to have good cycle life, but they are very difficult to activate, especially for AB(2) type alloys. In this study, a Zr0.9Ti0.1 (Ni0.57V0.1Mn0.28Co0.05)(2.1) alloy was prepared by melt-spinning followed by ball-milling with Co3Mo additive in order to improve its kinetic characteristics. The experimental results showed that the alloy exhibited a much improved activation performance as well as electrochemical capacity after 2 hours milling. Cyclic voltammetry and electrochemical impedance experiments also showed that ball-milling of the alloy with Co3Mo could improve the surface activation property to a great extent. This can be attributed to the catalytic effect of Co3Mo, which had a much closer contact to the alloy powders after ball-milling, on the hydrogen oxidation. However, long time milling could decrease the capacity gradually due to the further amorphization of the ahoy

Electrochemical performance of Sn-substituted, LaNi5-based rapidly solidified alloys

Sn-substituted, LaNi5-based rapidly solidified alloys with low Co content, La(1-x)A(x)Ni(4.25)Co(0.5)Sn(0.25)(A=La, Nd, Ce,and x=0.2),were prepared by melt-spinning. The microstructure of the as-spun alloys was observed with SERI and the element distribution of the as-spun and annealed alloys was analyzed by EDX. It is found that the as-spun alloys had fine grains. However, there was Sn segregation in the grain boundaries of the as-spun alloys. XRD patterns show that for the as-spun alloys the lattice strain could be alleviated through vacuum annealing. The electrochemical performance of the as-spun and heat-treated alloys was investigated. It is found that the Ce-containing as-spun alloy had a cycle Life more than 300 cycles. After heat-treatment, the electrochemical performance of the Ce-free alloys could be further improved, which is attributed to the alleviation of the lattice strain and the change of Sn distribution

Improved thermal stability of TbF3-coated sintered Nd–Fe–B magnets by electrophoretic deposition

Using electrophoretic deposition (EPD) method, the impact of TbF3 diffusion on the coercivity, microstructure and thermal stability of sintered Nd–Fe–B magnets with different rare earth (RE) content was investigated. In the diffused magnets with the RE content of 34 wt.%, the maximum coercivity about 28.12 kOe with less than 1.44 wt.% Tb was achieved, the coercivity temperature coefficient (β) was improved to -0.50 %/°C from -0.58 %/°C within the temperature interval 25-160 °C, and the maximum operating temperature further increased to about 160 °C. It suggested that TbF3 diffused magnets had much superior thermal stability than the annealed samples. This was attributed to the formation of the Tb-rich (Nd, Tb)2Fe14B phase in the outer region of the matrix grains and the improved Nd-rich grain boundary phase after TbF3 diffusion.

Enhanced corrosion resistance of sintered NdFeB magnets by diffusion of Co film prepared by direct current magnetron sputtering deposition

In this study, the Co films were prepared by direct current (DC) magnetron sputtering deposition onto the substrates of sintered NdFeB magnets (N46) which were made by conventional powder metallurgy route. Magnetic properties, grain boundary and corrosion resistance were observed for the heat treated magnets. Highly accelerated stress test, energy-dispersive X-ray spectroscopy, SEM, TEM and electron back-scattering pattern method were employed to study the surface morphology and grain boundary phase modification by Co diffusion on the surface of the magnets.