Yong-Gang Yang

Macroporous ‘bubble’ graphene film via template-directed ordered-assembly for high rate supercapacitors

A three-dimensional bubble graphene film, with controllable and uniform macropores and tailorable microstructure, was fabricated by a facile hard templating strategy and exhibit extraordinary electrochemical capacitance with high rate capability (1.0 V s(-1)).

Chemically derived graphene-metal oxide hybrids as electrodes for electrochemical energy storage: pre-graphenization or post-graphenization?

The introduction of a secondary phase is an efficient and effective way to improve the electrochemical performance of graphene towards energy storage applications. Two fundamental strategies including pre-graphenization and post-graphenization were widely employed for graphene-based hybrids. However, there is still an open question of which way is better. In this contribution, we investigated the differences in the structure and electrochemical properties of pre- and post-graphenized graphene-SnO2 hybrids. The pre-graphenization is realized by synthesis of thermally reduced graphene and subsequent impregnation of SnO2, while the post-graphenization is realized by introducing a Sn-containing phase onto GO sheets followed by chemical reduction. The pre-graphenization process provides a large amount of pores for ion diffusion, which is of benefit for loading of SnO2, fast ion diffusion for supercapacitors, and higher capacity for Li-ion batteries, but poor stability, while the post-graphenization process offers compact graphene and good interaction between the SnO2 and graphene, which provides stable structure for long term stability for supercapacitor and Li-ion battery use.

Effect of Air Gap on Morphology of Polyacrylonitrile Triangular Fiber

Polyacrylonitrile triangular fiber was prepared by the technique of dry-jet wet spinning. In order to study the effect of air gap on the morphology of triangular nascent fiber, various air gap distances ranging from 3 to 7 mm were studied. The cross-section of triangular nascent fiber was observed through an optical microscope, the surface of the fiber was examined with an atomic force microscopy, and its pore structure by mercury porosimetry. The results showed that the profile degree decreased with the increase of air gap distance; the surface tension was a key factor that affected the deformation of the cross-sectional shape of triangular nascent fiber. In addition, surface roughness of triangular nascent fiber, with the growth of air gap distances, increased first and then decreased. An abrupt change of the surface roughness of the fiber may have resulted from that of polymer contents on the surface of the dope stream in the air gap. Furthermore, the pore volume in the triangular nascent fiber decreased with the increase of air gap distance. This may be attributed to change of the total polymer content of the dope stream in air gap.Polyacrylonitrile triangular fiber was prepared by the technique of dry-jet wet spinning. In order to study the effect of air gap on the morphology of triangular nascent fiber, various air gap distances ranging from 3 to 7 mm were studied. The cross-section of triangular nascent fiber was observed through an optical microscope, the surface of the fiber was examined with an atomic force microscopy, and its pore structure by mercury porosimetry. The results showed that the profile degree decreased with the increase of air gap distance; the surface tension was a key factor that affected the deformation of the cross-sectional shape of triangular nascent fiber. In addition, surface roughness of triangular nascent fiber, with the growth of air gap distances, increased first and then decreased. An abrupt change of the surface roughness of the fiber may have resulted from that of polymer contents on the surface of the dope stream in the air gap. Furthermore, the pore volume in the triangular nascent fiber decreased with the increase of air gap distance. This may be attributed to change of the total polymer content of the dope stream in air gap.

A Theoretical Rod Model for Investigating the Polyacrylonitrile Copolymer Coagulation Process

A theoretical rod model for investigating the polyacrylonitrile (PAN) copolymer coagulation process was presented in this work. The mass transfer rate and coagulation rate under different coagulation conditions were obtained using this method. An optical microscope with image transfer software was employed to observe the coagulation boundary of the filament. The results showed that the coagulation rate decreased continuously with the increase of bath concentration. However, with the increase of the bath concentration, the mass transfer rate decreased at the beginning of the coagulation, and as the t1/2 increased, the weight loss was greater when the bath concentration was higher. Moreover, the coagulation rate and mass transfer rate increased with the increase of the coagulation temperature, and the coagulation was most moderate when the bath temperature was 50°C.