Practical melting temperature

To work within a reasonable and practical melting temperature range, at or below 1200°C, it is necessary to operate within a restricted region within the following boundaries of an idealised ternary... 

Practical melting temperature is not the melting temperature associated with the crystal-liquid phase transition (Chapter 5) but the worldiig temperature. 

Creep. The phenomenon of creep refers to time-dependent deformation. In practice, at least for most metals and ceramics, the creep behavior becomes important at high temperatures and thus sets a limit on the maximum appHcation temperature. In general, this limit increases with the melting point of a material. An approximate limit can be estimated to He at about half of the Kelvin melting temperature. The basic governing equation of steady-state creep can be written as foUows ... 

As described in Sect. 1, the relevant length scales and time scales are a serious problem for any simulation of polymer melts [12,16-20] and, as discussed, a polymer coil has structures on different distance scales (Fig. 1.2) [17] and relaxations on different time scales. A brute force approach, consisting of a simulation of fully atomistic models of a sufficiently large system over time scales for which thermal equilibration could be reached at practically relevant temperatures, is totally impossible. Useful progress requires a different approach. 

In practice, we take two samples the hrst comprises material whose origin and purity we know is good. The second is fresh from the laboratory bench it may be pure and identical to the first sample, pure but a different compound, or impure, i.e. a mixture. We take the melting point of each separately, and call them respectively Tmelt, pure) nnd Tnieit, unknown) know for sure that the samples are different if these two melting temperatures differ. 

This imphes that for a given lamellar thickness, the melting temperature and the crystallization temperature should be the same. In practice, this is not observed. 

For practical purposes, within the NN frame the ionic strength dependence can be taken into account in the estimate of the free energy and of the melting temperature by using empirical equations with numerical prefactors. Such equations display a leading logarithmic dependence on salt concentration which reproduces the experimental observations well and allows simple and reliable calculations [3, 15]. 

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