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Vapor-grown carbon fibers (VGCFs) have outstanding mechanical, thermal, and electric characteristics, and it has strong anisotropy. To take advantage of the enhanced properties, the orientation control of VGCFs should be important. In recent years, the orientational control of VGCFs by magnetic processing has received considerable attention. We have performed the magnetic processing of polymer composite films including VGCFs by using magnetic processing apparatus with permanent magnets (1 T) and superconductive magnet (10 T). We have studied the orientation of VGCFs along the thick-ness direction of the film. It was demonstrated that the oriented VGCFs/polymer composite films were successfully produced even by permanent magnets (1 T). The volume resistivity (Ω·cm) of the film (vertically oriented VGCFs, 1.0 wt %, 10 lim thickness) showed 3.2 × 1012 and 2.1 × 100 Ω·cm along surface and thickness direction, respectively. Vertically oriented VGCFs / polymer composite film could be utilized as an alternative material having anisotropic electric conductive property.

Carbon nanotube (CNT) /polymer composites have been expected for a promising application of CNT and have received considerable attention in fundamental studies. Recent progress of Carbon nanotube/polymer composites is reviewed from polymer material point of view for utilizing CNTs into polymer matrix.

Carbon fiber (CF) has outstanding mechanical, thermal, and electric characteristics, and it has strong anisotropy. To take advantage of the enhanced properties, the orientation control of CFs should be important. In recent years, the aligned carbon nanotube (CNT) /polymer composites have been produced by the application of high magnetic field. However, there are few reports about magnetically oriented CF/polymer composites. We have performed the magnetic processing of polymer composite films including CFs by using our magnetic processing machine (0.9 T) with permanent magnets, and a commercially available superconductive magnet (10 T). We have studied the orientation of CFs along the thickness direction of the film. The orientational distribution of CFs was analyzed by three dimensional optical microscope analysis in addition to X-ray diffraction. It was demonstrated that the oriented CF/polymer composite films were produced even by permanent magnets. The electric resistance of the film (vertically oriented CFs, 10wt.%), after magnetic processing (0.9T), was improved by the order of 109Ω·cm. It was also found that the film showed anisotropic electric property.

We have investigated the effect of dissolving organic polymers on the dispersion of VGCF (vapor-grown carbon fiber) TM in various organic solvents through optical microscope observation. VGCFTM as received had aggregated structure with particle shapes having a broad diameter distribution. We have used tetrahydrofran (THF), dimethylformamid (DMF), benzene (BZ), and dichloromethane (DCM) as organic solvents, and polycarbonate (PC), polystyrene (PS), and polymethylmethacrylate (PMMA) as organic polymers. After stirring VGCFTM in each organic solvent, most VGCFTM was remained as the aggregated particle structure which had similar structure as received. However, it was found that VGCFTM aggregated particles disappeared and were dispersed individually by dissolving organic polymers in the solvents after stirring for 30min. We have discussed the correlation between the polymer structures and the dispersion of VGCFTM. Furthermore, several drops of THF/PC solution containing individually dispersed VGCFTM, which was the best composition in the series of experiments which used four solvents and three polymers, was put on a cover glass, and THF was removed by spin coating, resulting in PC/VGCFTM thin film on the cover glass. PC was decomposed by heat treatment, and only dispersed VGCFTM whose both ends were clearly observed on the cover glass were finally obtained. Through measuring the length of VGCFTM by SEM with the help of an image analysis soft ware, the exact averaged length was determined.

Fundamental dispersion study of vapor-grown carbon fibers (VGCFs), which, as received, had an aggregated lump form, was performed using a series of ionic liquid, which is N-metyl-N'-alkyllimidazoliumtetrafluoroborate having different alkyl (CnH2n+1) chain length (n=2, 4, 6, 8). In situ optical microscope observation was carried out for the dispersion of a trace amount of VGCF in each ionic liquid, prepared by ultrasonic treatment and magnetic stirring. The degree of VGCF dispersion was improved when the alkyl chain length of ionic liquid became longer. The initial aggregated lump of VGCF still remained in the ionic liquid having the shortest alkyl chain (n=2), but completely disappeared in the ionic liquid having the longest alkyl chain (n=8).