Superconducting Characteristics of a Carbon/N-Alkane Mixture above Room Temperature

Abstract

Abstract The search for superconductors with higher critical temperatures is an important research topic. Currently, superconductivity above room temperature (20°C) has only been observed under very high pressures (above 200 GPa). In this study, the resistance of a pitch-based carbon fiber/n-alkane (n-CkH2k+2, k = 8, 9, 10, 12, 13, and 16) mixture in a heated Teflon tube was measured using a two-terminal measurement system to confirm the presence of a superconducting phase at temperatures above room temperature and at ambient pressure. The results showed that the resistance suddenly increased at temperatures between 367.77 and 504.24 K (Tincrease) and that the amount of change in resistance at Tincrease varied by two orders of magnitude between the samples. Measurements and calculations showed that n-alkanes did not reach their boiling point at Tincrease, indicating that this rapid increase in resistance was a property of the mixture. The extremely large range of resistance of the mixture above Tincrease was due to the variation in the aspect ratios of the pitch-based carbon fibers inserted into the Teflon tubes. However, these large variations were not observed at temperatures below Tincrease, suggesting that n-alkanes dramatically reduce the resistance of the mixture at temperatures below Tincrease. The sudden increase in resistance at Tincrease and the alkane effect support the hypothesis that Tincrease is the critical temperature for superconductivity and indicates the existence of superconductors with critical temperatures above 500 K at ambient pressure.