Showing papers by "Wei-Li Song published in 2016"

Unusual continuous dual absorption peaks in Ca-doped BiFeO3 nanostructures for broadened microwave absorption

Abstract: Electromagnetic absorption materials have received increasing attention owing to their wide applications in aerospace, communication and the electronics industry, and multiferroic materials with both polarization and magnetic properties are considered promising ceramics for microwave absorption application. However, the insufficient absorption intensity coupled with the narrow effective absorption bandwidth has limited the development of high-performance multiferroic materials for practical microwave absorption. To address such issues, in the present work, we utilize interfacial engineering in BiFeO3 nanoparticles via Ca doping, with the purpose of tailoring the phase boundary. Upon Ca-substitution, the co-existence of both R3c and P4mm phases has been confirmed to massively enhance both dielectric and magnetic properties via manipulating the phase boundary and the destruction of the spiral spin structure. Unlike the commonly reported magnetic/dielectric hybrid microwave absorption composites, Bi0.95Ca0.05FeO3 has been found to deliver unusual continuous dual absorption peaks at a small thickness (1.56 mm), which has remarkably broadened the effective absorption bandwidth (8.7-12.1 GHz). The fundamental mechanisms based on the phase boundary engineering have been discussed, suggesting a novel platform for designing advanced multiferroic materials with wide applications.

A general model of dielectric constant for porous materials

Abstract: For eliminating the limits in the classical models, here we establish a general model for precisely predicting dielectric constant of porous materials. In this model, dielectric constant is independent on pore shapes when the pore size is far smaller than electromagnetic wavelengths; however, it depends on the porosities and correlation between the open pore direction and wave propagation direction. The structure factor β in the effective dielectric formula is 1 and 3 for through-hole and closed-pore materials, respectively. The experimental results are in good agreement with the model, suggesting a favorable tool for predicting dielectric properties of porous materials.

Confined Porous Graphene/SnOx Frameworks within Polyaniline-Derived Carbon as Highly Stable Lithium-Ion Battery Anodes.

Abstract: Tin oxides are promising anode materials for their high theoretical capacities in rechargeable lithium-ion batteries (LIBs). However, poor stability usually limits the practical application owing to the large volume variation during the cycling process. Herein, a novel carbon confined porous graphene/SnOx framework was designed using a silica template assisted nanocasting method followed by a polyaniline-derived carbon coating process. In this process, silica served as a template to anchor SnOx nanoparticles on porous framework and polyaniline was used as the carbon source for coating on the porous graphene/SnOx framework. The synthesized carbon confined porous graphene/SnOx frameworks demonstrate substantially improved rate capacities and enhanced cycling stability as the anode materials in LIBs, showing a high reversible capacity of 907 mAh g–1 after 100 cycles at 100 mA g–1 and 555 mAh g–1 after 400 cycles at 1000 mA g–1. The remarkably improved electrochemical performance could be assigned to the uniq...

Fabrication of micro-fine spherical Ti–6Al–4V alloy powders based on hydrogen decrepitation and plasma spheroidisation

Abstract: A novel process was developed for scalable fabrication of micro-fine spherical Ti–6Al–4V alloy powders. The hydrogenation-treated Ti–6Al–4V alloy ingot was mechanically crushed into particles and then sieved into three size grades. The powders were separately sent through the radio frequency (RF) argon plasma system for spheroidisation. The fabrication process and powder characteristics were investigated. The results indicate the alloy ingot upon hydrogenation treatment can be efficiently crushed into fine particles with size of 5–76 μm. During RF plasma processing, the powders are found to be greatly refined due to hydrogen decrepitation with subsequent transformation into spherical morphology. The effect of hydrogen decrepitation on particle refinement is impaired with decreasing particle size of feed powders. The spherical powders exhibit a narrow particle size distribution and the average size is in the range of 8.2–27.9 μm. The spheroidised powders mainly consist of β-Ti and TiH1.5.