Arrhenian equation

Two mathematical expressions, the Arrhenian equation and the Vogel-Fulcher-Tamman equation, are commonly used to express the temperature dependence of the viscosity of glass forming melts. At one extreme, we find that the viscosity can often be fitted, at least over limited temperature ranges, by an Arrhenian expression of the form ... 

Determination of nucleation rate curves by traditional methods is discussed in Chapter 2. These studies are usually very time-consuming and tedious. A faster, easier method for determination of a pseudo-nucleation rate curve was developed by Marotta, et al, based on DSC measurements of nucleated glasses. Their method is also based directly on the JMA equation, with the assumption that the temperature dependence of the rate is given by an Arrhenian equation. The final expression derived using their assumptions indicates that ... 

The constant A is tjQ, and T and To are temperamres (°C). The VFT equation provides a good fitting of data over a wide range of temperamres. Anyhow, near the lower end of the transformation region, it should be used with caution because the activation energy of viscosity AE ) is almost constant and hence viscosity values may be overestimated. When To 0, then the VFT equation changes to the Arrhenian equation, i.e.. 

Equation (1.29) permits the determination of the cooling-rate dependence of the glass-transition temperature for metallic glasses that have viscosities given by the modified VFT relation with the free volume given by eq. (1.13), rather than exhibiting an Arrhenian dependence. Thus,... 

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