GATE 2022 MT – Question 55
During solidification of a pure metal at undercooling 10 K, the critical-nucleus radius is ______ $\times10^{-9}$ m (one decimal place). Solid–liquid interface energy is 0.177 J/m$^2$, melting point 1356 K, and latent heat per volume $1.88\times10^9$ J/m$^3$.
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 25.1 to 25.9
Explanation
The volumetric driving force is $|\Delta G_v|\approx L_v\Delta T/T_m$. Critical radius is $r^*=2\gamma/|\Delta G_v|=2(0.177)(1356)/(1.88\times10^9\times10)=25.53\times10^{-9}$ m. Requested coefficient: **25.5**.