Magnesium diboride (MgB2) is known as a promising superconductor due to its high transmission temperature. Similarly to single-wall carbon nanotube, unique characteristics would be seen if a nanotube structure of MgB2 having a unit-wall of Mg and B atomic bilayer is prepared. However, such MgB2 nanotubes have not ever been synthesized. In this article, formation mechanism of unit-wall MgB2 nanotube is elucidated by molecular mechanics calculation. From the viewpoint of energetic stability, the unit-wall will be curled up to form nanotube structure when MgB2 crystal is disassembled to an isolated unit-wall layer. An experiment using arc plasma in inert liquid was utilized to produce unit-wall MgB2 nanotubes. As a result, a single and multiunit-wall MgB2 nanotube was successfully synthesized. In this reaction field, the arc plasma may play a role to produce isolated MgB2 unit-wall fragment, and the cold cathode surface can contribute to preserve MgB2 nanotube structure.
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