No abstract

Paramagnetic odd‐fluorinated fullerenes have been observed and characterized by electron spin resonance (ESR), revealing evidence that the fluorination process is inhomogeneous and that these species are not very stable. It is suggested, therefore, that the only method of stabilizing odd fluorinated fullerenes would be to capture the fluorine inside the C60 cage. The relative stability of the various fluorinated fullerenes is discussed.

We report on ESR and electric conductivities of BBB and BBL ladder polymers with emphasis on the former. Both the ESR and the electrical conductivities are strongly anisotropic suggesting that the polymer backbones are plannar. The ESR data implies the existence of two different types of spin species. The hyperfine spectrum of one of these species is analyzed in terms of a Spin Hamiltonian and anisotropic transferred hyperfine interaction with the 14N nuclei (I = 1). We found that “annealing” the BBB and BBL films to high temperatures, To, increase the spin susceptibility for To ≤ 850K (BBB). However annealing to To ≥ 900K results in a dramatic reduction in the spin susceptibility and dramatic incise in the conductivity. The room temperature in-plane conductivity of annealed samples at To ≥ 900K exceeds σ = 1 Ω−1 cm−1. This high intrinsic conductivity is probably associated with the formation of cross-linked condensed aromatic structure. The 'phase transition” temperature to this structure is higher by 50K for BBB compared to BBL. The conductivity versus temperature of annealed samples (700K ≤ To) can be described by the onisotropic version of Mott's law for variable range hopping. We demonstrate that the anisotropic conductivity is due to the anisotropic localization lengths (ξ∥ and ξ⊥) of the wave function of the localized states.

cannot be considered in isolation. In contrast, the individual steps of overall production must be adapted to one another. Thus the powder properties determine the suitability of the powder for a specific molding technique. That means that the developer of high-performance ceramics must be given the opportunity, as early as possible, to scale up his work in order to be able to incorporate the processing steps into the materials development with the help of parallel (and particularly nondestructive) testing methods.

Structure and property characterization of low-k dielectric porous thin films determined by x-ray reflectivity and small-angle neutron scattering AIP Conf. Combined surface Brillouin scattering and x-ray reflectivity characterization of thin metallic filmsWe demonstrate that high quality thin films of fullerenes (C& and fluorinated fullerenes can be prepared from solution by the spin coating technique on float glass or silicon wafers. The films were characterized by x-ray reflectivity and diffuse x-ray scattering. A systematic study of films of different thicknesses allows estimation of the distance between the fullerenes spheres to be 10.9 f 1 A in our Cc0 films. The C6e film-air surface is very smooth. Annealing in air above 90 "C leads to an irreversible increase of the film thickness, which is attributed, at present, to oxidation.