Glass devitrification temperature

Waste-Form Stability. If they occur at all, solid state transformations in dry glass and UO2 matrices will be too slow under the temperature conditions of service to be observable in the laboratory at the same temperature. Here we need to extrapolate from high temperature laboratory conditions to low temperature service conditions. It will be desirable to develop an intimate knowledge of the processes of phase separation and devitrification of sodium borosilicate glasses at temperatures below the softening point by meticulous application of electron microscopic. X-ray crystallographic and other techniques. The glasses will contain inactive elements representative of the fission product... 

In the 1930s, Chamot and Mason defined the state of chemical microscopy (6) by detailing their work on the physical methods and chemical analysis involved with chemical microscopy. In the U.K. in 1954, Welch described a simple microscope attachment for the observation of high-temperature phenomena (7). The small, electrically heated thermocouple could hold a microscopic sample for single-crystal growth assays, melting-point determinations, and glass devitrification studies. 

From this equation one sees that the large-amplitude motion contributes fully in the liquid state (y = 0) and not at all in the glassy state (y = 7i/2). The glass transition temperature, defined at Ae temperature of half-vitrification or devitrification, occurs at y - tc/3. An example of the data treatment as indicated in Equation 8 is shown in Figure 1. 

It is essential to understand the molecular and thermodynamic properties that contribute to the solubility and stability of an ASD. The properties include glass transition temperature, fragility, molecular mobility, devitrification kinetics, and chemical interactions. A thorough understanding of aU of these aspects is imperative for a rational formulation strategy. 

The plotted according to the experimental data dependencies of elasticity modulus E on macromolecular entanglements cluster network density (Figs. 2.5 and 2.6) break down into two linear parts, the boundary of which serves loosely packed matrix glass transition temperature which is lower on about 50K of polymer glass transition temperature [50]. Below the value E is defined by the total contribution of both clusters and loosely packed matrix and above - only by clusters contribution. It becomes clear, if to taken into consideration, that above the elasticity modulus value of devitrificated loosely packed matrix has the order of 1 MPa [51], that is, negligible small. It is an extremely interesting the observation, that loosely packed matrix in the value E, determined by the plot E (v, ) extrapolation to = 0, is independent on temperature. Such situation is not occasional and deserves individual consideration. 

Let us note, that the indicated temperatures also correspond well to loosely packed matrix glass transition temperature of PS and PPO K, which is approximately by 50 K below than macroscopic [26]. This assiunes, that the crazing process at high temperatures for PC and PPO is due to mechanically devitrificated loosely packed matrix drawing facility (in which instable clusters, restricting this process, are absent) in craze fibrils. The Eqs. (1.9), (1.12) and (4.66) indicate unequivocally the cause of PS tendency to... 

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