Search

Graphene materials have recently experienced rapid developments, but large-scale production of high-quality graphene is still desired. Electrochemical exfoliation method is considered as a promising approach to meet this requirement. Here we demonstrate a non-electrified electrochemical exfoliation method to produce high-quality graphene (NEEG) sheets. By direct electrochemical reaction between graphite powders and metallic Li in 1 M LiPF6/propylene carbonate electrolyte, continuous graphite exfoliation is achieved with a high yield of excess 80% without any consumption of electric energy. The as-prepared NEEG has high quality with few defects (ID/IG = 0.45), a high C/O ratio of 27.74 and excellent electronic conductivity of 102.5 S cm−1. As conductive additives in Li4Ti5O12 electrode for lithium ion batteries, NEEG contributes to higher capacity and initial coulombic efficiency than common thermally reduced graphene oxide. Given the advantages of NEEG, the non-electrified electrochemical exfoliation method is promising for the large-scale preparation of high-quality graphene sheets.

By combining the new superposition principle of linear elasticity used in discrete dislocation plasticity and the recently available solutions of the elastic displacement and stress fields due to a polygonal dislocation loop within an anisotropic homogeneous full-space, the anisotropic elastic fields induced by a 3D polygonal prismatic or a glide dislocation loop (PP(G)DL) in a bimaterial of finite thickness crystal films are obtained. The location and orientation of the PP(G)DLs with respect to the fixed reference coordinate system are arbitrary. Factors influencing the interface elastic fields, such as the size of the PP(G)DLs, the distance between the PP(G)DLs and the interface, the thickness of the layer containing the PP(G)DLs and lastly the mismatch of crystallographic orientation of the adjacent layers are investigated in detail. The present model has two distinct features of easy extensibility to planar or nonplanar multilayered polycrystalline models and the ease of numerical implementation for parallel programming.

Foundation for Innovative Research Team of Jimei University [2007A001]; Nature Scientific Fund in Fujian Province, China [B0110034]

ZnO and ZnO-Al2O3 thin films were prepared by dc magnetron sputtering and their structural, optical and electrical properties were studied comparatively. It is discovered that the ZnO-Al2O3 thin films remain transparent in a shorter wavelength range than the ZnO films, resulting from the increase of their band gap. Their resistivity decreases by seven orders of magnitude, which is caused by doping of Al to ZnO grains in the film. Preferential orientation of ZnO grains in the ZnO-Al2O3 thin films deteriorates because of the existence of Al2O3 impurity phase in the film.