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1 2010

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HRTEM nanostructural evolution of onion-like spheres in polyacrylonitrile fibres during stabilization and carbonization

Wen Y., Li H., Peng G., Yang Y., Liu L.

Materials Science Poland

2010

Vol. 28, No. 2

479--490

Ultrathin sections of polyacrylonitrile (PAN) fibre samples in the stabilization and carbonization stages were studied using high-resolution transmission electron microscopy. Supplementary analyses by the Fourier transform infrared, X-ray diffraction, thermogravimetry mass spectroscopy and elemental analysishave also been done. Results showed that the PAN fibres contained nanosized crystallites embedded in a continuous amorphous matrix. Amorphous onion-like spherical structures were also observed and their structural evolution was investigated. During the stabilization and carbonization process, the outer layers of the onion-like spheres gradually changed from an orderly layered structure into a disordered, dense structure due to cyclization and cross-linking reaction. During carbonization, the onion-like spheres became more dense and compact due to the merging of the ring structures. After carbonization, the onion-like spheres in the PAN fibres eventually turned into dense and amorphous domains of carbon fibres.