# Analysis of Nucleation and Glass Formation by Chip Calorimetry
## 3 Results and Discussions
### Stable La-Based MG
Similar to the analyses process for the delay time confirmation method in part (1) for Al-based MG and in part (2) for La-based MG, the onset value of the \(T_{g}\) with the annealing time \(t_{a}\) can be plotted as shown in Figure 5b. From Figure 5b, with the increase of \(t_{a}\) at 200 \({}^{\circ}\)C, one break point time appears at 33.7 s. Before and after 33.7 s, the evolution paths of \(T_{g}\) with \(t_{a}\) follow two different paths corresponding to the structural relaxation and the composition effect. Meanwhile, the isothermal method was also applied to measure the delay time for Mg\({}_{65}\)Cu\({}_{25}\)Gd\({}_{10}\) MG sample at 200 \({}^{\circ}\)C. As shown in Figure 5c, at 200 \({}^{\circ}\)C, when the annealing time increases to about 35 s, the exothermic peak corresponding to the primary crystallization appears. The time of 35 s is the delay time at 270 \({}^{\circ}\)C, which is very close to the experimental data of 33.7 s based on the evolution of the glass transition \(T_{g}\) with the annealing time \(t_{a}\). Figure 4: (**a**) A series of Flash DSC heat flow curves corresponding to different annealing times ranging \(t_{a}\) from 1 to 50 s at 270 \({}^{\circ}\)C for La\({}_{60}\)Ni\({}_{15}\)Al\({}_{25}\) MG; (**b**) plot of \(T_{g}\) and \(t_{a}\) at 270 \({}^{\circ}\)C (\(t_{1}\) and \(t_{2}\) are two selected annealing times before and after the break point of 22.5 s); (**c**) the isothermal test for La\({}_{60}\)Ni\({}_{15}\)Al\({}_{25}\) MG at 270 \({}^{\circ}\)C; and (**d**) XRD patterns for annealed samples corresponding to the annealing times of \(t_{1}\) and \(t_{2}\). To confirm if the delay time of the experimental breakpoint time by Flash DSC corresponds to the onset time for primary crystallization, two annealing time points were selected before and after the break point time, \(t_{1}\) (30 s) and \(t_{2}\) (40 s). XRD tests for these two annealed samples were conducted. The corresponding XRD patterns corresponding to the annealing times of \(t_{1}\) and \(t_{2}\) are shown in Figure 5d. One can see that at 200 \({}^{\circ}\)C, the sample with the annealing time of 30 s before the breakpoint time are still amorphous without any crystals; in contrast, for the samples with the annealing time of 40 s after the breakpoint time, one sharp crystallization peak is observed. Thus, the above results show that the break point time of 33.7 s is actually the delay time at 200 \({}^{\circ}\)C for the stable Mg\({}_{65}\)Cu\({}_{25}\)Gd\({}_{10}\) MG.  
the primary crystallization appears. The time of 6.3 s is the delay time at 50 \({}^{\circ}\)C, which is very close to the experimental data of 6.6 s based on the evolution of the glass transition \(T_{g}\) with the annealing time \(t_{a}\). By selecting three annealing time points before (\(t_{1}\), 6 s) and after the break point (\(t_{2}\), 8 s), the XRD tests for these two annealed samples were conducted. The annealed samples before and after break point are respectively amorphous and crystalline in Figure 6d, which confirms the delay time at 50 \({}^{\circ}\)C for the PBT sample. Based on the previous research [28,29], for amorphous polymer materials, with the increase of the annealing time, the crystalline phase gradually grows and the ordering degree within polymer increases. Considering that the polymer is one single composition, the break point for \(T_{g}\)-\(t_{a}\) plot in amorphous PBT in Figure 6b corresponds to the transition from the relaxation effect to the ordering effect. Based on the above results and discussions in parts (1)-(4), the experimental method to determine the delay time for primary crystallization based on the chip calorimetry is an effective method for various amorphous materials, which provides a good opportunity to investigate the nucleation and crystallization behaviors in glassy materials.