Browsing by Author "Fréchette, Van Derck"

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    Fracture of glass in the presence of H2O
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1985) Fréchette, Van Derck
    Direct examination of crack-generated surfaces has shown that the stress intensity values conventionally calculated require correction if slow crack growth in glass is to be understood quantitatively. The effect of water in diminishing the strength of glass and in lowering the stress required to run a crack at a particular velocity in the slow growth range has been well documented [1]. However, the models chosen to represent the observed effects quantitatively have been incomplete. It is the present purpose to review certain aspects that have been reported already [2 to 3] and to present additional results and considerations.
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    Was Libyan Desert Glass formed by a sol-gel process?
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1989) McPherson, Donald M.; Pye, L. David; Fréchette, Van Derck; Mortsea, Mary
    Despite extensive research for nearly five decades, the origin of Libyan Desert Glass remains a puzzle. It is suggested that this glass was made by a low-temperature, chemical process known to have produced other natural glasses, such as opal. This new genesis is based upon a periodic void spacing observed in this material and irreversible changes that occur upon heating, especiahy crystallization and consolidation. These features are seemingly irreconcilable with a melt-derived origin for Libyan Desert Glass, but are consistent with a low-temperature chemical mode of formation.