Xihai Jin

Fe2O3@SnO2 nanoparticle decorated graphene flexible films as high-performance anode materials for lithium-ion batteries

A flexible graphene film decorated with spindle-like Fe2O3@SnO2 nanoparticles was fabricated through vacuum filtration of Fe2O3@SnO2 and GO mixing solution, followed by thermal reduction. The core–shell structured Fe2O3@SnO2 nanoparticles were synthesized through a facile hydrothermal route, which avoided agglomeration of Fe2O3 and SnO2 nanoparticles and was beneficial for electrolyte diffusion. Microstructure characterizations showed that the spindle-like Fe2O3@SnO2 nanoparticles were uniformly dispersed between layered graphene nanosheets, forming a sandwich-like structure. The unique interleaved structure was favorable for lithium ion diffusion and electron transfer. As binder-free electrodes for lithium-ion batteries, the flexible Fe2O3@SnO2/GS films exhibited discharge and charge capacities of 2063 and 1255 mA h g−1 respectively, with an excellent cycling performance of 1015 mA h g−1 even after 200 cycles. The specific capacity of the Fe2O3@SnO2/GS electrode is higher than that of both Fe2O3/GS and SnO2/GS electrodes, indicating a positive synergistic effect of Fe2O3 and SnO2 on the improvement of electrochemical performance.

Lanthanum modified bismuth titanate prepared by a hydrolysis method

La-modified bismuth titanate ceramics with compositions of Bi4−xLaxTi3O12 (x = 0, 0.2, 0.5, 0.75) were fabricated using powders prepared by a hydrolysis method. It was found that the partial substitution of lanthanum for bismuth in the Bi4Ti3O12 lattice significantly influenced the crystallization behavior, IR characteristics, and sinterability of the powder, as well as the microstructure and the dielectric properties of the sintered ceramics. The formation of the Bi2Ti2O7 intermediate phase during the powder crystallization process was suppressed, and the IR bands corresponding to Ti–O stretching vibrations were shifted to higher wavenumbers in La-modified bismuth titanate. With an increase in the doping level of lanthanum, the sintering temperature was steadily elevated, while the grain growth speed was reduced; and the dielectric property measurement indicated a continuous decrease in the Curie temperature and dielectric loss.

Preparation of nanocrystalline-coated carbon nanotube/Ni0.5Zn0.5Fe2O4 composite with excellent electromagnetic property as microwave absorber

A combined precipitation-hydrothermal method was used to fabricate carbon nanotube/Ni0.5Zn0.5Fe2O4 ferrite composite powders. The phase, microstructure and electromagnetic properties of CNT/NiNi0.5Zn0.5Fe2O4 composites were investigated. After surface modification, The zeta potential value of CNTs could maintain at about -50mV when pH is higher than 8, which affords a suitable surface environment for in situ coating of NiNi0.5Zn0.5Fe2O4 nanocrystallines. With increasing CNTs content, the saturation magnetization of the composites is gradually reduced, while the complex magnetic permeability changes little. The complex dielectric constant of the composites is significantly increased when the concentration of CNTs approaches the percolation threshold value of 2 wt%. When CNTs content is 5 wt%, the reflection ratios are less than -10 dB within the frequency range 2-9 GHz, and the reflection ratios reach a minimum -32.5 dB at a frequency of about 3.9 GHz.

Microstructure and mechanical properties of NdAlO3/Al2O3 nanocomposite

Abstract NdAlO 3 /Al 2 O 3 nanocomposite was prepared by a coprecipitation method. It was found that the stabilizing effect of Nd 2 O 3 on γ-Al 2 O 3 rendered α-Al 2 O 3 form at higher temperature than usual. NdAlO 3 /Al 2 O 3 nanocomposite showed a much better sinterability than Al 2 O 3 , and the NdAlO 3 was exclusively rhombohedral in the sintered samples. SEM observation verified that NdAlO 3 strongly restricted Al 2 O 3 grain growth when the NdAlO 3 content was low, however, this effect decreased as the NdAlO 3 content was increased to 20 vol.%. Significant improvements in the mechanical properties of Al 2 O 3 were realized when it formed nanocomposite with an appropriate amount of NdAlO 3 .

Microstructure and mechanical performances of ZTA/LaAl11O18 composite prepared by a heterogeneous precipitation method

Abstract Al2O3 composite combinatively strengthened by ZrO2 and in situ formed LaAl11O18 was prepared by a heterogeneous precipitation method. The sintering temperature was significantly lowered in comparison with monolithic Al2O3. ZrO2 and LaAl11O18 inhibited Al2O3 grain growth, forming fine and uniform microstructure in the material. SEM showed that increasing numbers of Al2O3 and LaAl11O18 grains fractured transgranularly, because of the strengthened grain boundary by residual thermal stress. X-ray diffraction revealed that ZrO2 was exclusively in tetragonal symmetry (t-ZrO2) and did not transformed to m-ZrO2 under the fracture stress. The strength of the material was about 1 GPa, almost doubled over that of monolithic Al2O3.

Effects of Nb2O5 on the stability of t-ZrO2 and the mechanical properties of ZTM

Abstract In this paper, ZTM ceramics have been co-doped with Nb 2 O 5 and Y 2 O 3 . It is found that the alloying of Nb 2 O 5 into ZrO 2 makes t -ZrO 2 more unstable, resulting in an increase in the m -ZrO 2 content. Despite the very small change in microstructure, the mechanical properties of these materials are considerably improved. The results of this work suggest that enhanced microcrack toughening by m -ZrO 2 is the more significant cause of the improvement in mechanical performance.

The influence of the preparation method on the microstructure and properties of Al2O3/TiN nanocomposites

Abstract Al2O3/TiN nanocomposites were fabricated by hot pressing of powders prepared through ball milling (BM) and in-situ nitridation (PN) methods, respectively. And the mechanical and electrical properties as well as microstructure of the nanocomposites were studied. It was found that TiN showed a strong reinforcing effect in both materials. Due to the difference in the powder preparation method, the Al2O3/TiN nanocomposite from PN powder showed a finer TiN particle size and a more uniform microstructure than the nanocomposite from BM powder. As a result, the former material showed a superior electrical conducting behavior and better mechanical properties.