Reversible formation-melting of nano-crystals in supercooled oxyfluoride germanate liquids
Reversible formation-melting of nano-crystals in supercooled oxyfluoride germanate liquids
复制标题
过冷氟锗酸盐液体中纳米晶体的可逆形成-熔化
DOI：
10.1016/j.jeurceramsoc.2019.08.002
复制
发表时间：
2019
影响因子：
5.7
通讯作者：
Yue Yuanzheng
中科院分区：
文献类型：
--
作者：
Liu Hao;Qiao Ang;Gao Yongxiao;Tao Haizheng;Zhao Xiujian;Hu Yuebo;Yue Yuanzheng
纳米晶体在产生和影响玻璃材料的功能方面起着关键作用。因此，科学家们在澄清玻璃中纳米晶体形成的微观机制以获得所需类型的纳米晶体方面做出了相当大的努力。然而，在加热过程中的纳米晶体的相变还没有得到很好的理解。在这里，我们报告的发现，在加热-冷却循环过程中的氧氟锗酸盐玻璃中的纳米晶体的可逆熔融形成。使用差示扫描量热法（DSC），在玻璃进行DSC向上扫描至925-986 K之间的温度并随后冷却后，我们在加热过程中检测到925 K处的惊人吸热事件。基于拉曼光谱、X射线衍射和透射电子显微镜，吸热归因于纳米晶体BaGeF 6（约20 nm）的熔化。DSC向下扫描时，在890 K观察到一个激发响应，表明BaGeF 6纳米晶的重新形成。这表明BaGeF_6纳米晶的熔化-形成是一个典型的一级相变过程。
The nanocrystals play a critical role in generating and affecting functionalities of glass materials. Therefore, scientists have made considerable efforts in clarifying microscopic mechanisms of nanocrystal formation in glass to obtain the desired type of nanocrystals. However, the phase transitions of nanocrystals during heating have not been well understood. Here we report on a discovery of the reversible melting-formation of nanocrystals in an oxyfluoride germanate glass during heating-cooling circles. Using a differential scanning calorimetry (DSC), we detected a striking endothermic event at 925 K during heating, after the glass underwent a DSC upscan to a temperature between 925–986 K and subsequent cooling. Based on Raman spectroscopy, X-ray diffraction and transmission electron microscopy, the endotherm is attributed to the melting of nano-crystal BaGeF6(˜20 nm). An exothermal response was observed at 890 K during the DSC downscan, implying the re-formation of BaGeF6nano-crystals. This suggests that the melting-formation of BaGeF6nano-crystals is a typical first-order transition.