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Choi S.,Korea Advanced Institute of Science and Technology | Jung D.S.,Korea Institute of Ceramic Engineering And Technology | Choi J.W.,Korea Advanced Institute of Science and Technology
Nano Letters | Year: 2014

A variety of silicon (Si) nanostructures and their complex composites have been lately introduced in the lithium ion battery community to address the large volume changes of Si anodes during their repeated charge-discharge cycles. Nevertheless, for large-scale manufacturing it is more desirable to use commercial Si nanoparticles with simple surface coating. Most conductive coating materials, however, do not accommodate the volume expansion of the inner Si active phases and resultantly fracture during cycling. To overcome this chronic limitation, herein, we report silicon oxycarbide (SiOC) glass as a new coating material for Si nanoparticle anodes. The SiOC glass phase can expand to some extent due to its active nature in reacting with Li ions and can therefore accommodate the volume changes of the inner Si nanoparticles without disintegration or fracture. The SiOC glass also grows in the form of nanocluster to bridge Si nanoparticles, thereby contributing to the structural integrity of secondary particles during cycling. On the basis of these combined effects, the SiOC-coated Si nanoparticles reach a high reversible capacity of 2093 mAh g-1 with 92% capacity retention after 200 cycles. Furthermore, the coating and subsequent secondary particle formation were produced by high-speed spray pyrolysis based on a single precursor solution. © 2014 American Chemical Society.

Huh S.H.,Korea Institute of Ceramic Engineering And Technology
Carbon | Year: 2014

A method for determining the number of layers (NL) or thickness (DGP) of multi-layer graphene (MLG) using X-ray diffraction (XRD) is reported for the first time. The XRD pattern showed clear variations in the full-width-at-half-maximum (FWHM) values of the (0 0 2) peak of crystalline MLG with NL = 3, 4, 5, 6, and 7. The large FWHM difference per layer and the instant measurement of large areas of MLG demonstrates that XRD is a powerful probe. The obtained linear plot of FWHM versus 1/DGP and the NL-dependent evolution of the interlayer distance (d002) toward the d002 of graphite are also discussed. © 2014 Elsevier Ltd. All rights reserved.

Chang H.S.,Korea Institute of Ceramic Engineering And Technology
Solar Energy Materials and Solar Cells | Year: 2011

We have investigated the effect of high-pressure pure hydrogen annealing (HPHA) for upgraded metallurgical grade (UMG)-silicon solar cell in order to obtain cost-effective high-efficiency cell using post-metallization anneal at a relatively low temperature. We have observed that high-pressure pure hydrogen annealing effectively passivated the defects and improved the minority carrier lifetime, series resistance and conversion efficiency. It can be attributed to significantly improved hydrogenation in high-pressure pure hydrogen process. This improvement can be explained by the enhanced hydrogenation of silicon solar cell with antireflection layer due to hydrogen re-incorporation. The results of this experiment represent a promising guideline for improving the high-efficiency solar cells by introducing an easy and low cost process of post-hydrogenation in optimized condition. © 2010 Elsevier B.V. All rights reserved.

Jeong B.-Y.,Korea Institute of Ceramic Engineering And Technology
Journal of Korean Institute of Metals and Materials | Year: 2012

The microstructure and texture of TiN coatings on a Ni-based super-alloy were characterized by the automated version of electron backscatter diffraction (EBSD), EBSD techniques were used to investigate the very fine TiN grain shape and crystal orientation. This study confirmed that EBSD techniques provide a very useful tool for characterization of coating materials. The TiN grains had a special texture, a {001}-fiber texture in the coating layer. It was also found that, in severe environments, the coating performance of equiaxial and randomly oriented TiN is superior to that with columnar structures. © 2012 The Korean Institute of Metals and Materials.

Korea Institute of Ceramic Engineering And Technology and Hyundai Motor Company | Date: 2013-12-30

A method for preparing graphene nanoplate (GNP) is provided and includes preparing expanded graphite (EG) and exfoliating, grinding, or cracking the expanded graphite to crack the EG induced by gas-phase-collision. A graphene nanoplate paste and a conductive coating layer formed of the graphene nanoplate paste are provided and are prepared by the method for preparing graphene nanoplate.

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