The National Institute for Materials Science succeeded in realizing superconductivity in fullerene nanowhiskers, which are a nanosized carbon material that is lightweight and has a fine fibrous shape. This is a giant step toward the birth of lightweight, flexible superconducting materials.
The National Institute for Materials Science succeeded in realizing superconductivity in fullerene nanowhiskers, which are a nanosized carbon material that is lightweight and has a fine fibrous shape. Among the conventional superconducting materials, superconductors with comparatively high superconducting transition temperatures were mainly intermetallic compounds or ceramics, and those were often heavy, hard materials.
Critical current density of the developed fullerene nanowhisker superconductor (5K). The critical current density remains constant over a wide range of field intensities, showing that this material has excellent superconducting properties.
The NIMS team succeeded for the first time in the world in realizing superconductivity in a fullerene-based material by adding potassium to fullerene nanowhiskers, which are a nano-sized thread-like substance that can be synthesized from fullerenes, and heat-treating the resulting nanowhiskers. Even when the material manifests superconductivity, it retains its fine, fibrous structure. Furthermore, substantially 100% of the specimen material becomes a superconductor with heat treatment for one day. From the results of magnetization measurements, the superconducting transition temperature is approximately 17K. The critical current density is extremely high, at 10^5 Amps per square centimeter, even in a magnetic field, and the decrease in the critical current density accompanying increased field strength is slight. From these results, it is clear that this is an outstanding superconducting material.
Many materials with high superconducting transition temperatures, beginning with high temperature superconductors, MgB2, etc. are hard and brittle, and a high level of technology was necessary to process those materials into wire form, for example, for superconducting electrical wire. However, because the fullerene nanowhisker superconductor obtained in this research is lightweight, has a fine fiber-like shape from the initial stage, and maintains that fine, fibrous shape even after the appearance of superconductivity, it is considered that superconducting materials with diverse forms, such as a bundled fiber form, cloth-like form, and the like will be produced in the future. Thus, this achievement is a great advance toward the realization of lightweight, flexible superconductors.