Filters

1994 - 199912000 - 20041

More filters

20242
Reset filters

Settings

Author: Conradt, Reinhard × Type: Article ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Thermodynamic approach to viscosity in the glass transition
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Conradt, Reinhard
    The glass transition is re-investigated by means of the formahsm of linear nonequilibrium thermodynamics. The process is treated for melts cooled down below their liquidus temperatures in terms of three events. These events are, in the order of decreasing temperature: by-passing of crystallization, freezing-in of stress relaxation, and freezing-in o f near-range structural relaxation. Conditions for the viscosity levels are derived at which each of these events is accomplished. The model is tested against data of five one-component, three simple binary and ternary, and three multicomponent systems. Within the scope of this test, it is confirmed that the model correctly describes the viscosity levels typical of the glass transition, as well as their dependence on the cooling rate. An explanation for the 10¹³dPa*s rule at Tg is included.
  • Thumbnail Image
    Item
    Experimental study on the effect of cullet and batch water content on the melting behavior of flint and amber container glass batches
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Dubois, Olivier; Conradt, Reinhard
    The melting behavior of two commereial flint and amber glass batches with varied cullet content (0, 40, 65 % and 0, 40, 76 %, respectively) and batch water additions (0 to 5 %) was investigated. The cullet was a blend of up to five industrial types and grades, including ground cullet. Local temperature, electrical conductivity, and thermal diffusivity were determined in 200 g scale tests as a function of temperature, while the vertical distribution of the former two properties was determined by 10 kg tests in 5 cm high batch piles charged on top of a pre-heated glass melt (7 kg). The set of methods applied was established as a service tool for the quantitative comparison of the batch-to-melt conversion of different batches in general. For the flint and amber glass batches investigated, cullet additions primarily improved the thermal behavior, with moderate versus high additions required for flint and amber, respectively. The silica dissolution in cullet-free batches was enhanced by batch water additions, but retarded again with increasing cullet eontent. The presence of phonolite besides batch water and cullet yielded especially negative results.