|Spoluautoři JINDROVÁ Eliška, URBÁNEK Štěpán|
The most common allotropic modification of tin is white tin (β tin), which is thermodynamically stable from 13.2 °C to 161 °C. The allotropic modification grey tin (α tin) is thermodynamically stable below 13.2 °C. When pure white tin is structurally transformed to pure gray tin, it results in the total disintegration of pure tin objects and pure tin solders. We investigated the relationship between the temperature and the kinetics of both the structural transformation of β→α tin and the reverse transformation α→β tin. To accelerate the rate of the structural transformation of β→α tin, particles of the pure α tin were pressed by electromechanical machine LabTest 5.250SP1-VM into samples of pure β tin and stored at -60 °C, -40 °C and -20 °C. Particles of the pure α tin were stored at +60 °C, +40 °C and +20 °C to study the kinetics of the reverse transformation of α→β tin. The rates of structural and reverse transformation were determined by XRD analysis using a PAN analytical X’pert Pro diffractometer and by image analysis using Image J software. Our results suggest that temperature plays the main role in both types of transformation. Interestingly, whereas the literature often suggests that the structural transformation of β→α tin occurs most quickly from -40 °C to -50 °C, we found that it was quickest at -60 °C.The rate of α→β tin reverse transformation accelerates with increasing temperature.