| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2004: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The present candidates for the storage application of high pressure fluid are carbon nanotubes. First of all, we examined the mechanical strength of carbon nanotubes to know a capability for storage of high-pressure fluids. Then, we conducted in-situ X-ray diffraction experiments under high pressure using a diamond anvil cell (DAC) combined with x-ray from synchrotron radiation. No interlayer interaction such as sp^3 hybridization that could lead to hexagonal diamond in graphite was observed under compression up to 52 GPa. Furthermore, despite the history of non-hydrostatic compression, electron microscopic observation revealed that the structure remained nested tubular. This reversibility suggests the nanotubes have strong durability on non-hydrostatic compression under extreme pressures.
Next, we tried to make experiments of gas loading to the nanotubes under pressure. In advance, a gas loading system was built for the purpose of controlling the pressure in loading gas into DAC. After
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loading argon into the sample chamber, where nanotubes sample was placed, the pressure applied up to 6 GPa. The sample was heated to 1000 K by a CO_2 laser. The heated sample was recovered at ambient condition, and then analyzed by a scanning electron microscope equipped with EDAX detector. A very small amount of argon was detected. However, the detected potion was inhomogeneous due to temperature gradient by the laser heating. Thus we change the experiments from the laser heated DAC to the hot isostatic pressing (HIP) apparatus. A large amount of sample can be kept at the 800-1000 deg C under 300 MPa argon pressure for 10 hrs in this apparatus. Several samples of open and closed end multi-walled nanotubes, bundled single-walled nanotubes, and fullerene are treated in this apparatus at the same condition. The recovered samples are carefully examined by analytical transmitted electron microscopes (ATEM and STEM). According to the EDX mapping of argon in the samples, a large amount of argon are only detected from the bundled single walled carbon nanotubes. Hence, we can conclude that argon can be trapped in an interstitial position of bundled single-walled nanotubes. Less
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