Viscosity of glass-forming liquids

8 An Angell plot of the dependences of the viscosities of a series of liquids on their reduced temperature T/Tg, defining strong (Arrhenian) and fragile (VFT) liquids (from Busch (2000) courtesy of TMS). 

Mg65Cu25Yio are intermediate between those of fragile and strong liquids and demonstrate their sueeess in retarding crystallization. 

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TABLE 21.3 Crystallization Velocities and Viscosities of Glass-Forming Liquids ... 

Mauro JC, Yue Y, Ellison AJ, Gupta PK, Allan DC (2009) Viscosity of glass-forming liquids. Proc Natl Acad Sd 106 19780-19784... 

Cook, R.L., Herbst, C.A. King, Jr., H.E. (1993). High- iessuie viscosity of glass-forming liquids measured by the centrifugal force diamond anvil viscometer. J. Phys. Chem., 97, 2355-2361. 

In equation (3.01), A and B are empirical constants, Vocc is the volume occupied by the constituent particles and v/ is the free volume. In equation (3.02), r]a, C and To are constants. VTF equation implies that viscosities of glass forming supercooled liquids are non-Arrhenius and To is the temperature which linearizes the data of the non-Arrhenius plot. Cohen and Turnbull (Cohen and Turnbull, 1959 Turnbull and Cohen, 1961,... 

Roessler, E., Hess, K.-U., and Novikov, V. N. (1998) Universal representation of viscosity in glass forming liquids, J. Non-Cryst. Solids 223, 207-222. 

The functional dependence of viscosity on temperature has been measured in a large number of glass-forming liquids, and phenomenologically it has been... 

Stickel, F, Fischer, E. W., and Richer , R., Dynamics of glass-forming liquids 11. Detailed comparison of dielectric relaxation, dc-conductivity, and viscosity data, J. Chem. Phys., 104, 2043-2055 (1996). 

Viscous Flow of Glasses Forming Liquids Experimental Techniques for the High Viscosity Range... 

In this chapter we summarize the viscous flow behavior of glass forming liquids and discuss the main experimental techniques for viscosity determinations in the upper range. 

Glasses, like metals, are formed by deformation. Liquid metals have a low viscosity (about the same as that of water), and transform discontinuously to a solid when they are cast and cooled. The viscosity of glasses falls slowly and continuously as they are heated. Viscosity is defined in the way shown in Fig. 19.7. If a shear stress is applied to the hot glass, it shears at a shear strain rate 7. Then the viscosity, ij, is defined by... 

The solidity of gel electrolytes results from chain entanglements. At high temperatures they flow like liquids, but on cooling they show a small increase in the shear modulus at temperatures well above T. This is the liquid-to-rubber transition. The values of shear modulus and viscosity for rubbery solids are considerably lower than those for glass forming liquids at an equivalent structural relaxation time. The local or microscopic viscosity relaxation time of the rubbery material, which is reflected in the 7], obeys a VTF equation with a pre-exponential factor equivalent to that for small-molecule liquids. Above the liquid-to-rubber transition, the VTF equation is also obeyed but the pre-exponential term for viscosity is much larger than is typical for small-molecule liquids and is dependent on the polymer molecular weight. 

Glass-Forming Liquids II. Detailed Comparison of Dielectric Relaxation, DC-Conductivity and Viscosity Data. 

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