Ideal Glasses Research Articles

Flow via dislocations in ideal glasses

Dislocation lines with variable Burgers vectors can exist in glasses and there is now experimental evidence for this, especially in metallic glasses. The kinematics and dynamics of their motion is discussed. It is suggested that dilatance at the core of a moving dislocation determines the viscous drag that acts on it in an ideal glass; and, this is discussed in terms of free-volume theory. Defect debris in the wake of a moving dislocation is also considered. The advantages of using dislocation theory for describing the flow of glasses are outlined.

Ideal Semiconducting Glasses

Ideal Semiconducting Glasses

Transient electrical behavior of glass membranes Part. III. Experimental

Responses of commercial pH-sensitive and other cation-sensitive glass membranes have measured under application of voltage pulse steps and a.c. currents. Responses have been found to be independent of solution environment pH, alkali metal and magnitude of exciting signal over a wide range. Variations of response with temperature have been noted. The membranes acting as linear systems, respond in agreement with the theoretical predictions and verify the essential correctness of fixed site membrane theory applied to membrane transients. A range of behavior from ideal film-free pH glasses to highly hydrated film coated glass electrodes have been observed to test the extreme cases of the theory. Time constants and double-layer capacitances have been tabulated.

Transient electrical behavior of glass membranes: Part. III. Experimental

Summary Responses of commercial pH-sensitive and other cation-sensitive glass membranes have measured under application of voltage pulse steps and a.c. currents. Responses have been found to be independent of solution environment pH, alkali metal and magnitude of exciting signal over a wide range. Variations of response with temperature have been noted. The membranes acting as linear systems, respond in agreement with the theoretical predictions and verify the essential correctness of fixed site membrane theory applied to membrane transients. A range of behavior from ideal film-free pH glasses to highly hydrated film coated glass electrodes have been observed to test the extreme cases of the theory. Time constants and double-layer capacitances have been tabulated.

Oxide Glasses in Light of the “Ideal Glass” Concept: I, Ideal and Nonideal Transitions, and Departures from Ideality*

This two‐part paper develops a basis for discussing glass properties which has features in common with standard “actual vs. ideal” treatments of physicochemical behavior, by defining thermodynamically an ideal state for the glass and discussing the states of the actual glasses in terms of their “departures from ideality.” The glass transition, which freezes the state of the actual glass, is seen as the consequence of the progress of the liquid toward the ideal state, which, for kinetic reasons, is unattainable. The single complexion limit of the Gibbs‐DiMarzio treatment for chain polymers and a minimum volume zero excess entropy condition related to random close packing for simple liquids are seen as complimentary descriptions of the ideal state, which also sets the thermo‐dynamic low‐temperature limit to the liquid state. Glasses formed from simpler molten salt and concentrated aqueous solution systems appear to approach the ideal state and thus provide a behavior pattern against which departures from ideality in the more complex silicate and borate glasses of practical interest may be assessed. In part I general aspects of the problem posed by the glass transition phenomenon are discussed, a dynamic interpretation for simple glasses in terms of the state of phonon excitation of the glassy solid is conjectured, and the concepts of ideal and nonideal (practical) glasses and glass transitions are elucidated from consideration of thermodynamic and kinetic factors involved in the volume relaxation of liquids toward the glassy state. Attention is given to units for describing departures from ideality to permit comparisons among different systems. The limited data for inorganic glasses are examined. Departures from ideality, as usually found in the physicochemical comparison of “actual” with “ideal” behavior, are attributable to specific interactions among the particles of the system, but magnitudes also depend on heat capacity changes. The former factor reaches a maximum in vitreous SiO2 which thus may be one of the least ideal of glasses.