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Volume 2013 (2013)
- Issue 260 Pages 279-
- Issue 259 Pages 243-
- Issue 258 Pages 165-
- Issue 257 Pages 95-
- Issue 256 Pages 1-
Volume 2013, Issue 259
Displaying 1-4 of 4 articles from this issue
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Research Papers
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Fumihiko Tanaka, Daniel Wolverson, Tomonaga Okabe, Ian A. Kinloch, Rob ...Article type: Research Paper
2013 Volume 2013 Issue 259 Pages 243-247
Published: June 15, 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSWe have used UV-Raman spectroscopy to study the sp3 structure in polyacrylonitrile- and pitch-based carbon fibres with Young's modulus values in the range of 90-830 GPa. The composite microstructure of these carbon fibres comprises an amorphous carbon phase that transfers the load to a reinforcing graphite crystalline phase. The intensity ratio of the T, D and G Raman bands showed that the low modulus polyacrylonitrile-based carbon fibres (Young's modulus=200-300 GPa) contained 10-25% sp3 carbon, whereas the stiffer polyacrylonitrile-based carbon fibres (Young's modulus >350 GPa) contained ∼5% sp3 material. This result suggests that the proportion of sp3 carbon decreases as the amorphous structure is converted into a crystalline structure during the carbonization treatment, leading to the high performance fibres. This observation is consistent with our current understanding of the relationship between structure and mechanical properties in carbon fibres.View full abstractDownload PDF (600K) -
Katsumi Kamegawa, Keiko NishikuboArticle type: Research Paper
2013 Volume 2013 Issue 259 Pages 248-254
Published: June 15, 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSAn approach for manufacturing hollow carbon microparticles of various morphologies has been developed. The approach includes spray drying of an aqueous solution of lignin and inorganic compounds to prepare composite microparticles, followed by heat treatment, washing, and drying. The morphology of the carbon microparticles is greatly affected by the inorganic compound used and the added fraction of the inorganic compound to lignin, although the kind of lignin and its molecular weight have little effect on the morphology. The weight yield of carbon microparticles to the original lignin content is about 40%. Typical morphologies of carbon microparticles are (1) very thin and flexible spherical hollow carbon microparticles prepared by addition of lithium carbonate, and (2) hollow and porous carbon microparticles obtained by using sodium metasilicate in which carbon beads of about 10 nm are connected in a highly branched structure. Spherical hollow carbon microparticles with a bulk density of 0.015 g cm-3 are so flexible that their original spherical form is mostly recovered when returned to atmospheric pressure after compression at 100 MPa. The hollow and porous carbon microparticles obtained by heating at 1000 °C exhibit superior electrical conductivity compared with commercial conductive carbon nanoparticles, acetylene black and Ketjenblack.View full abstractDownload PDF (5097K) -
Akihiko Nagasaka, Takashi Miyawaki, Tateo Machida, Kyoichi Oshida, Wat ...Article type: Research Paper
2013 Volume 2013 Issue 259 Pages 255-260
Published: June 15, 2013
Released on J-STAGE: October 01, 2013
JOURNAL FREE ACCESSThe effect of vapor-grown carbon fiber (VGCF) content on the mechanical properties and abrasion resistance of a VGCF/polytetrafluoroethylene (PTFE) composite was investigated. A resin powder of PTFE of 50 µm in diameter was used as the matrix. The resin and VGCF were mixed by a blender mill with the VGCF content in the range 0-3 wt%. Tensile testing was performed on an Instron type tensile testing machine at a crosshead speed of 10 mm/min (strain rate: 6×10-3/s), using smooth and V-notched tensile specimens. Thermal conductivity (λ) was measured using the laser flash method. The coefficient of dynamic friction (μ′) was measured using the ball-on-disc method. The results show that the tensile strength of VGCF/PTFE composites was lower than that of the PTFE matrix and decreased as the VGCF content increased due to the weak bonding between the VGCF and PTFE matrix. The abrasion resistance of PTFE was enhanced by the addition of VGCF-H.View full abstractDownload PDF (1424K)
Recent Doctoral Theses
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Shinichiroh IwamuraArticle type: Recent Doctoral Thesis
2013 Volume 2013 Issue 259 Pages 263-265
Published: September 01, 2013
Released on J-STAGE: October 01, 2013
JOURNAL RESTRICTED ACCESSSilicon (Si) draws great attention as a candidate material for high-capacity negative-electrodes of next-generation lithium-ion batteries (LIBs) due to about 10 times larger capacity than that of graphite, which is widely used for negative electrodes in conventional LIBs. Si, however, has several serious problems which hinder its practical usage. The first problem is a limitation of charge/discharge rate due to lower electrical conductivity and lower reaction rate with lithium (Li) than those of graphite. In order to improve this problem, it is effective to decrease the particle size to the nano range and make composites with conductive materials like carbon. Second, the cyclability is very poor due to destructions of the electrode structure by Si's volume change during charge/discharge. In this thesis, we designed nano-structures of Si-containing electrodes having buffer “nano-spaces” around nanosized Si. And their properties as negative electrodes were evaluated. In each of the three chapters, three completely different kinds of “nano-spaces” were investigated: “nano-space” prepared around Si nanoparticles by a template method, dynamically transforming “nano-space” during charge/discharge cycle and “nano-space” formed by electrical Li extraction from eutectic Li–Si alloy. Considering their charge/discharge properties and structure changes, new guidelines for structure designs of Si-containing electrodes were proposed.View full abstractDownload PDF (371K)
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