Kinetics and mechanisms of crystal growth and diffusion in a glass-forming liquid

Abstract

Extensive data on the viscosity, covering 15 orders of magnitude, and crystal growth rate, covering seven orders of magnitude, of liquid diopside (CaO.MgO.2SiO(2)) were collected in a wide range of undercoolings from 1.10T(g) to 0.99T(m) (T(g) is the glass transition temperature and T(m) the melting point). The raw growth rate data were corrected for the increased interfacial temperature produced by the heat released during crystallization. A detailed analysis confirms that growth mediated by screw dislocations reasonably explain the experimental data in these wide ranges of temperatures and growth rates. Effective diffusion coefficients were calculated from crystal growth rates and from viscosity, and were then compared with measured self-diffusion coefficients of silicon and oxygen in diopside melt. The results show that oxygen and silicon control the diffusion dynamics involved in crystal growth and viscous flow. This study not only unveils the transport mechanism in this complex liquid, but also validates the use of viscosity (through the Stokes-Einstein or the Eyring equations) to account for the kinetic term of the crystal growth expression in a wide range of temperatures.

Correlation Between Molecular Mobility and Crystal Growth of Amorphous Phenobarbital and Phenobarbital with Polyvinylpyrrolidone and L‐proline

“…Again, as with nucleation kinetics, in the case of pure volume-diffusion controlled crystal growth, one should find a good correlation between crystal growth rate and a-relaxation. 30 In the case of surface-integration controlled crystal growth, one might assume that a-and brelaxations and specific interaction between bulk molecules and molecules at the growth site have individual contributions to the incorporation process. That is, a molecule has to be in same orientation (a-relaxation) and in same conformation (b-relaxation) as molecules in crystal lattice in order to incorporate to crystal lattice.…”

Relaxation Behavior of Ca-Based Bulk Metallic Glasses

“…[2] only if DT g is essentially independent of the heating rate, which is not always correct. [1,18] In general, use of the total relaxation time for the calorimetric glass transition, s cal g ¼ DT g =u, instead of u, is more appropriate, [19,20] and m c is calculated as the slope of log s cal g vs 1=T cal g reduced by T ref g :…”

“…[2][3][4] Almost all bulk metallic glasses show intermediate fragile behavior. [5] Slow kinetics of crystallization due to high viscosity/high relaxation time of supercooled liquid can also be important for enhancing the GFA of bulk metallic glasses.…”

8. Stress-induced Pore Formation and Phase Selection in a Crystallizing Stretched Glass

“…As in Section 8.2.3.2, we used l ≈ 2⋅ 10 −10 m (the size parameter of the diffusing building molecules, which is equivalent to the jump distance or the lattice parameter -parameters commonly employed in such kinetic analysis (see, e.g. [41,42])) and the viscosity of the diopside melt [25] well described by the following VFT equation J 0 , will not strongly affect the nucleation rate, the value J 0 = 10 41 s −1 m −3 has been used for the calculation [14]. In Fig.…”

“…In addition to the computed values of p(r), experimental data on the specific surface energy, σ , and viscosity, η , were taken from [25,28], respectively. These data al- lowed us to estimate the thermodynamic barrier for pore nucleation, W * , the nucleation rate I and then the function N(r) by employing CNT in the described way.…”