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Spherulitic Crystal Growth Velocity in Selenium Supercooled Liquid
Year: 2016
Type of publication: článek v odborném periodiku
Name of source: Crystal Growth & Design
Publisher name: American Chemical Society
Place: Washington
Page from-to: 5811-5821
Titles:
Language Name Abstract Keywords
cze Sférolitický krystalový růst v podchlazeném tavenině selenu Sférolitický růst v podchlazené tavenině selenu byl měřen metodou IČ mikroskopie za izotermních podmínek od teploty Tg až po tání. Závislost získané rychlosti růstu sférolitů na teplotě byla proložena na základě kombinace základních růstových modelů. krystaly; sklotvorná tavenina; krystalizační kinetika; amorfní selen
eng Spherulitic Crystal Growth Velocity in Selenium Supercooled Liquid The spherulitic crystal growth velocity in selenium supercooled liquid has been measured by infrared microscopy in isothermal conditions for rapidly heated samples of a-Se from temperatures well below T-g. These data are compared and analyzed along with previously published data obtained on samples quenched from a temperature well above the melting point. The spherulites grew linearly over a course of time that corresponds to crystal growth controlled by crystal-liquid interface kinetics. The crystal growth velocity data obtained for these two different thermal histories can be described by the normal growth model for moderate supercoolings (Delta T <60 K). The screw dislocation growth provides a better description for larger supercoolings (Delta T > 90 K) that is also consistent with morphological observations. However, the prediction based on this model still significantly deviates for intermediate supercoolings. It is shown that all experimental data in the whole temperature range (T-g < T < T-m) can be described by a combined approach including both these models, taking into account actual viscosity scaling of crystal growth eta(-1). The kinetic information captured in the DSC curve is analyzed, providing evidence that the non-isothermal crystallization process can be described by the Johnson-Mehl-Avrami model. Two distinct regions characterized by different values of apparent activation energy were found. The transition between these regions coincides with morphological changes of spherulitic crystals and other properties. These regions are characterized by distinct apparent activation energies whose values are consistent with those obtained from microscopic measurement of crystal growth velocity. extended-chain crystals; glass-forming liquids; crystallization kinetics; amorphous selenium

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