Formation of a Superconducting Mixture of β-Mo₂C Nanoparticles and Carbon Nanotubes in an Amorphous Matrix of Molybdenum Compounds by the Pyrolysis of a Molybdenum Derivative of a Carboranylenesiloxane

A pyrolytic treatment (to 1000 °C) of the organometallic reaction product of the thermo-oxidatively stable carboranylenesiloxane, 1, and cyclopentadienylmolybdenum tricarbonyl dimer, Cp 2 Mo 2 (CO) 6, was discovered to yield nanoparticles of Mo 2 C concomitantly with carbon nanotubes in an amorphous matrix of Mo compounds. X-ray diffraction studies revealed that the Mo 2 C nanoparticles possess the hexagonal phase. A peak fit analysis using a Gaussian distribution function of the X-ray diffraction data revealed that 80% of the total molybdenum units in the mixture exist as β-Mo 2 C nanoparticles. The presence of the carbon nanotubes dispersed in the amorphous matrix was determined by both X-ray diffraction and high-resolution TEM analyses. The pyrolytic residue was determined to be superconducting with a critical temperature ( T c ) of 8 K. A comparative analysis of T c value of the residue and the reported individual T c values of the various components in the residue (β-Mo 2 C, carbon nanotubes, and some possible Mo compounds) pointed to β-Mo 2 C as the most probable cause for the superconductivity in the residue.