Navegando por Autor "Tuller, H. L."

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    Oxygen self-diffusion in a cordierite glass.
    (1998) Sabioni, Antônio Claret Soares; Zanotto, Edgar Dutra; Millot, F.; Tuller, H. L.
    Oxygen self-di€usion measurements determined below and above the glass transition temperature in a cordierite glass are reported. The di€usion experiments were performed by the solid±gas isotope exchange method using 18O as a tracer in H2±H2 18O and Ar/18O2 atmospheres. The 18O di€usion pro®les were established by secondary ion mass spectrometry (SIMS) after appropriate di€usion annealing. The oxygen di€usion coe cients changed at the glass transition temperature as expected. The atmosphere a€ected the oxygen di€usivity in agreement with other studies. The di€usion data were useful for comparisons with di€usion controlled process in the same glass. There is a di€erence between the activation enthalpies for crystal growth, viscous ¯ow, and oxygen self-di€usion. Hence, bond-breaking and molecular reorientation required for crystallization and the atomic transport mechanism involved in viscous ¯ow are not correlated in any obvious way to oxygen di€usion in cordierite glass. Ó 1998 Elsevier Science B.V. All rights reserved.