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Ulsan, South Korea

Jeong J.H.,University of Ulsan | Jung D.-W.,University of Ulsan | Kong B.-S.,KCC Central Research Institute | Shin C.M.,N Baro Technology Co. | Oh E.-S.,University of Ulsan
Korean Journal of Chemical Engineering | Year: 2011

A small amount of graphene nanosheets was added to commercial graphite as an anode active material in lithium ion batteries and its effects were examined through a variety of physical and electrochemical characterization techniques: FE-SEM, XRD, Raman, BET, and EIS. Compared to a commercial graphite electrode, a composite electrode containing 1 or 5 wt% graphene nanosheets showed higher reversible capacity and enhanced cyclability. This was attributed to the large surface area and low charge transfer resistance of the graphene nanosheets. © 2011 Korean Institute of Chemical Engineers, Seoul, Korea.

Choi J.T.,University of Ulsan | Kim D.H.,University of Ulsan | Ryu K.S.,University of Ulsan | Lee H.-I.,University of Ulsan | And 4 more authors.
Macromolecular Research | Year: 2011

Nanocomposites of thermoplastic polyurethane (TPU), which were prepared using two types of functionalized graphene sheets (FGS) of similar thickness but different sizes were examined. The percolation threshold of the nanocomposite was reduced, evidently by increasing the particle size of the FGS. This means that the FGS with a mean particle size of 8.3 ìm had a percolation threshold at 0.39 wt% in the nanocomposite of TPU, whereas it was 1.41 wt% when the FGS size was 2.4 ìm. The FGS enhanced the modulus of TPU through a reinforcing effect but both the tensile strength and elongation at break were reduced as the FGS content was increased. These effects of FGS on the tensile properties were more evident with a larger particle size of FGS. The morphology and thermal properties of the nanocomposites were also examined.

Kim S.C.,University of Ulsan | Lee H.-I.,University of Ulsan | Jeong H.M.,University of Ulsan | Kim B.K.,Pusan National University | And 2 more authors.
Macromolecular Research | Year: 2010

The effect of pyrene treatment on the dispersion, electric, and rheological properties of functionalized graphene sheets (FGS)/epoxy nanocomposites, was described. FGSs were dispersed in 100-fold of acetone containing the dissolved pyrene, and the mixture was sonicated at 330 W and 60 Hz for 1 h at room temperature. The results show that the dispersion of FGS is enhanced by treatment with pyrene, which causes a reduction in the percolation threshold to about 2 phr. The FGS images become more blurred after treatment with pyrene, which suggests that the dispersion of FGS in the epoxy matrix is enhanced by pyrene treatment. The complex viscosity increases as the FGS content is increased, and this increase is more evident as the amount of pyrene used for the treatment of FGSs is increased. Incomplete relaxation of dispersed FGS can be caused by physical congestion of highly anisotropic FGSs, which prevent free rotation in compliance with external dynamic shear.

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