Nakamura Nobutomo, Nakashima Shizuka, Ogi Hirotsugu
Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Sci Rep. 2019 Sep 6;9(1):12836. doi: 10.1038/s41598-019-49120-1.
Crystallization from amorphous solids is generally caused by activating phonons in a wide frequency range during heat treatment. In contrast, the activation of phonons in a narrow frequency range using ultrasonic treatment also causes crystallization below the glass transition temperature. These behaviors indicate that crystallization is related to the atomic motion in the glass state, and it is suggested that the activation of specific atomic motion can cause crystallization without increasing temperature. In this study, we observe nucleation and nuclei growth caused by mechanical oscillation in a hard-sphere colloidal glass and evaluate the effect of mechanical oscillation on the structural evolution in the early stage of the crystallization. Oscillation between 5 and 100 Hz is applied to the colloidal glass, and it is observed that the nucleation rate increases under the 70 Hz oscillation, resulting in formation of stable nuclei in a short amount of time. The nuclei growth is also accelerated by the 70 Hz oscillation, whereas increases in the nucleation rate and nuclei growth were not observed at other frequencies. Finally, activation of the diffusion-based rattling of particles by caging is considered as a possible mechanism of the observations.
非晶态固体的结晶通常是由热处理过程中在较宽频率范围内激活声子引起的。相比之下，使用超声处理在较窄频率范围内激活声子也会在玻璃化转变温度以下引起结晶。这些行为表明结晶与玻璃态中的原子运动有关，并且有人提出激活特定的原子运动可以在不升高温度的情况下导致结晶。在本研究中，我们观察了硬球胶体玻璃中由机械振荡引起的成核和核生长，并评估了机械振荡对结晶早期结构演变的影响。对胶体玻璃施加5至100赫兹的振荡，观察到在70赫兹振荡下成核速率增加，从而在短时间内形成稳定的核。70赫兹的振荡也加速了核的生长，而在其他频率下未观察到成核速率和核生长的增加。最后，通过笼蔽激活基于扩散的粒子晃动被认为是这些观察结果的一种可能机制。
