The contact between graphite and alkane causes superconductivity at room temperature.

What is it about?

Most researchers who specialize in materials with zero electrical resistance, that is, superconductors, are searching for materials that exhibit superconductivity at room temperature (~300K). However, many researchers are skeptical about the existence of such substances. This paper presents the possibility of causing superconductivity at room temperature under atmospheric pressure by combining materials that are readily available. In 1911, Kamerlingh Onnes discovered that mercury becomes a superconductor at temperatures below 4.2 K. Since then, we have had to wait for Bednorz and Müller to discover high-temperature cuprate superconductors in 1986 until the superconducting transition temperature exceeds 40 K. After that, the transition temperature rose sharply in a short period, and in 1993 the superconducting transition temperature rose to 133K due to the discovery of the cuprate superconductor (HgBa2Ca2Cu3Ox), but the transition temperature then stopped rising. On the other hand, hydrides with superconducting transition temperatures close to or above room temperature have been found under ultra-high pressures above 200 GPa. However, the only way to generate static pressure in this ultrahigh-pressure region is to use a diamond anvil high pressure device which has an extremely small high-pressure chamber (≪0.1mm3). Therefore, even if the state of room temperature superconductor is realized by using ultra-high pressure, its industrial application is almost impossible. I studied the chemical properties of the basal surface of graphite in the air, using a scanning tunneling microscope in air, ultra-high-vacuum scanning tunneling microscope, Raman scattering measurement, and temperature programmed desorption (TPD). During this research, I came up with a material composition in which superconductivity may occur at room temperature under atmospheric pressure. It is a mixture obtained by contacting an alkane (chain saturated hydrocarbon) with a graphite surface. To confirm this, a Teflon tube was packed with small thin flakes obtained by peeling from highly oriented pyrolytic graphite (HOPG), and n-octane was further injected to form a ring, and the joint was fixed with a glass tube. It was confirmed by an optical microscope that the HOPG flakes packed in the Teflon tube were in contact at the joint. Then, using electromagnetic induction, a circular current was passed through this ring. In addition, this ring-shaped Teflon container was placed in a jar with a screw lid (capacity: ∼50 ml) together with n-octane (∼1ml) and stored at room temperature for 50 days. After this storage, the ring axial magnetic field due to the current flowing through the ring was measured along the ring central axis in a permalloy double magnetic seal box, using a Hall element. This measurement showed that the ring current was maintained for more than 50 days without attenuation. The ring current I at each time after the ring current is generated in the coil is expressed by the formula I = I0exp (–Rt / L) of exponential decay. Here, I0, t, R, and L are the initial ring current value, the elapsed time after the ring current is generated, the resistance of the coil, and the self-inductance of the coil, respectively. The radius of the Teflon tube ring and the inner diameter of the tube are 0.8 cm and 0.096 cm, respectively. Therefore, the dimensions of the graphite flakes and octane mixture ring packed in this Teflon ring tube are ring outer diameter 1.696 cm, ring inner diameter 1.504 cm, and ring wire diameter 0.096 cm. The self-inductance L of the coil of this dimension is 3.16 × 10^–8 [H] = [Ωs]. For a copper ring of the same size, the electrical resistivity of copper is 1.68 x 10^–6 Ω cm, so R = 1.167 x 10^–3 Ω. Therefore, it can be seen by using the above exponential decay equation that the ring current is attenuated to about 1/10^16 in 1 ms after the ring current is generated. Furthermore, based on the experimental results, assuming that the ring current induced in the graphite flakes and n-octane mixture packed in the Teflon ring tube decreased to 99% in 50 days (4.32 × 10^6 [s]), the resistance of the mixture can be obtained by using the exponential decay equation. The resistance is calculated to be 7.36 × 10^–17Ω. When this resistance R is converted into resistivity, it becomes 1.065 × 10^–19Ωcm. Thus, the resistivity of the mixture of graphite flakes and n-octane packed in the Teflon tube can be estimated to be smaller than 1/10^13 of the resistivity of copper. Therefore, the experimental results suggest that the mixture obtained by contacting the graphite surface with an alkane becomes superconducting at room temperature under atmospheric pressure.

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Photo by Kaspars Eglitis on Unsplash

Photo by Kaspars Eglitis on Unsplash

Why is it important?

The method of achieving superconductivity at room temperature under atmospheric pressure presented in this paper is surprisingly simple: just bring the graphite surface into contact with chain saturated hydrocarbons (alkanes). However, while graphite is a material that has been known for quite some time, it still has some mysteries, and therefore it may not be easy to understand the mechanism by which superconductivity occurs. As a result, many experts cannot find a basis and may feel that the experiments presented are unbelievable. However, recently I have shown that the combination of graphene and n-hexane or n-heptane exhibits the perfect diamagnetism, which is one of the characteristics of superconductors, at room temperature under atmospheric pressure (arXiv: cond-mat/1801.09376) Moreover, more recently, Armen Gulian has observed ideal diamagnetism by dropping n-heptane onto graphene using more precise experimental equipment (Mod Phys Lett B 34, 2050415 (2020)). These results are another strong evidence that the mixture obtained by contacting the graphite surface with n-alkane is a superconductor at room temperature under atmospheric pressure. Therefore, this study is the first to show a method of creating a superconducting state at room temperature under atmospheric pressure. Thus, it provides important insights for many researchers to carry out additional tests and further advanced research.

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