• Dechang Jia

      Articles written in Bulletin of Materials Science

    • A novel method for preparation of hollow and solid carbon spheres

      Boyang Liu Dechang Jia Jiancun Rao Qiangchang Meng Yingfeng Shao

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      Hollow and solid carbon spheres were prepared by the reaction of ferrocene and ammonium carbonate in a sealed quartz tube at 500°C. The morphology and microstructure of the product were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The carbon spheres are amorphous and their diameters range from 0.8–2.8 𝜇m. The shell thickness of the hollow carbon spheres is not uniform and ranges from 100–180 nm. It is suggested that ammonium carbonate is crucial for the formation of carbon spheres and its amount also influences the morphology of the product. The method may be suitable for large scale preparation of carbon spheres.

    • Effects of fibre content on mechanical properties and fracture behaviour of short carbon fibre reinforced geopolymer matrix composites

      Tiesong Lin Dechang Jia Meirong Wang Peigang He Defu Liang

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      Geopolymer matrix composites reinforced with different volume fractions of short carbon fibres (Cf/geopolymer composites) were prepared and the mechanical properties, fracture behaviour and microstructure of as-prepared composites were studied and correlated with fibre content. The results show that short carbon fibres have a great strengthening and toughening effect at low volume percentages of fibres (3.5 and 4.5 vol.%). With the increase of fibre content, the strengthening and toughening effect of short carbon fibres reduce, possibly due to fibre damage, formation of high shear stresses at intersect between fibres and strong interface cohesion of fibre/matrix under higher forming pressure. The property improvements are primarily based on the network structure of short carbon fibre preform and the predominant strengthening and toughening mechanisms are attributed to the apparent fibre bridging and pulling-out effect.

    • Effect of heat treatment temperature on microstructure and electrochemical properties of hollow carbon spheres prepared in high-pressure argon

      Boyang Liu Yun Zhou Dechang Jia Pengjian Zuo Yingfeng Shao Jingwei Zhang

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      Heat treatment was carried out between 800 and 1200°C to investigate its effects on the microstructure and electrochemical properties of the hollow carbon spheres (HCSs) prepared in high-pressure argon. Samples were characterized by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy and N2 adsorption–desorption isotherms. The graphitization of the HCSs was improved with increase of heat treatment temperature. Mesopores of 𝑐𝑎. 4 nm in diameter were created on the HCSs after the heat treatment. The results of electrochemical performance measurements for the HCSs as anode material for lithium ion batteries indicate that the discharge capacity of the HCSs is improved after heat treatment at 800°C compared with the as-prepared HCSs and have a maximum value of 357 mAh/g and still retains 303 mAh/g after 40 cycles. However, the discharge capacity of the HCSs decreases and the cycling performance is improved with the increase of heat treatment temperature.

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