Chengyang Wang

Preparation of activated carbon hollow fibers from ramie at low temperature for electric double-layer capacitor applications

Activated carbon hollow fibers (ACHFs) with high surface area were prepared from inexpensive, renewable ramie fibers (RFs) by a single-step activation method under lower temperature than that of other reports. The effects of activation conditions on the pore structure and turbostratic structure of ACHFs were investigated systematically. The results show that ACHFs surface area decreased but micropore volume and conductivity increased as the increase of activation temperature and activation time. The electrochemical measurements of supercapacitors fabricated from these ACHFs electrodes reveal that the electrochemical properties improved with the enhancing of activation degree. However, too high activation temperature can make the ion diffusion resistance increase. It suggests that pore structure and conductivity are as important as surface area to decide the electrochemical performances of ACHFs electrode materials. A maximum capacity of 287 F g(-1) at 50 mA g(-1) was obtained for the ACHFs electrode prepared under suitable conditions.

Structural Characteristics of Mesophase Spheres Prepared from Coal Tar Pitch Modified by Phenolic Resin

Abstract Mesocarbon microbeads (MCMB) were prepared from coal tar pitch modified by phenolic resin and from the same pitch modified by phenolic resin and hexamethylenetetramine at 440°C for Ih. By investigating the morphology of mesophase spheres and the structure of the MCMB carbonized at 1000°C for Ih using scanning electron microscope (SEM) and XRD, it was found that phenolic resin accelerated the formation and coalescence of mesophase spheres. Some of the obtained MCMB were bi- or tri-spheres with the distorted microtextural carbon layers. Hexamethylenetetramine in the pitch modified by phenolic resin accelerated the condensation of phenolic resin and consequently expedited the combination of mesophase spheres, which was proved by the formation of some tetra-spheres. Owing to the cross-linkage of the additives, MCMB with complex structure were obtained.

New mesoporous carbons prepared from pitch by simultaneous templating and carbonization

Mesoporous carbons with high surface area were successfully prepared from a pitch using MgO as a tem plate. The mixtures of the pitch and the MgO precursors (magnesium acetate and citrate) with different mass ratios in powder form were carbonized at 950℃ in nitrogen. The MgO was dissolved using a 1mol/L hydrochloric acid aqueous solution after carbonization and the porous carbons formed were isolated. The results indicated that most of the pores in the carbons were mesopores , which were generated as a result of the temp lating action of MgO formed by pyrolysis of the MgO precursors. The BET surface area of the carbons could reach up to 1295m^2/g although no activation was performed. The carbon yield was as high as 50% mass fraction when magnesium citrate was used as the MgO precursor.

A Novel Composite Electrolyte Based on CeO 2 for Low Temperature Solid Oxide Fuel Cells: A Novel Composite Electrolyte Based on CeO 2 for Low Temperature Solid Oxide Fuel Cells

A novel composite material based on mixture of samarium-doped ceria (SDC)-carbonate was studied as electrolyte in low temperature solid oxide fuel cells.The phase and microstructures of composite electrolyte were examined by XRD and SEM.The electrical conductivity was investigated by AC impedance spectroscopy at 400-700℃in different atmospheres.An abrupt change in the con- ductivity at about 500℃indicates that different mechanisms affect transfer in different temperature ranges.The conductivity increases with the carbonate fraction above 500℃.The conductivity in reduce atmosphere is higher than that in oxide atmosphere.An anode-supported fuel cell using SDC-carbonate as electrolyte was fabricated and tested.The result shows that all the composite electrolytes exhibit better performance than pure SDC electrolyte.The electrolyte with 20wt% carbonate can achieve the highest power density of 415mW·cm~(-2) and an open circuit voltage of 1.00V at 500℃.