Fabrication of filamentary potassium-doped C60 superconductors by suspension spinning method

This paper describes the preparation of filamentary potassium-doped C-60 superconductors prepared by the suspension spinning method. Commercial C-60 powder was suspended in mixed poly(vinyl alcohol) solution of dimethyl sulfoxide and hexamethylphosphoric triamide (sample A). The viscous suspension was extruded as a filament into a precipitating medium of methyl alcohol and coiled on a drum. The filamentary sample was also prepared by the suspension spinning by using polyacrylonitrile solution of N,N-dimethylformamide (sample B). The samples were pyrolyzed to remove volatile components. Doping of potassium for the samples was prepared as following: At first, powder samples of nominal composition K6C60 was prepared by reaction Of C-60 with excess potassium. The K6C60 powder and filamentary sample with stoichiometric ratio of K3C60 were placed in Pyrex glass tubes and vacuum-sealed and heated at 250 degreesC for 36 h. SQUID measurement shows the superconductivity of sample B with T-c = 18 K. On the other hand, the superconductivity more than 2 K was not detected for sample A. (C) 2004 Elsevier B.V. All rights reserved.