Qiao Ang, To Theany, Stepniewska Malwina, Tao Haizheng, Calvez Laurent, Zhang Xianghua, Smedskjaer Morten M, Yue Yuanzheng
Department of Chemistry and Bioscience, Aalborg University, DK-9220 Aalborg, Denmark.
Phys Chem Chem Phys. 2021 Aug 12;23(31):16923-16931. doi: 10.1039/d1cp02213j.
Revealing the deformation mechanism of brittle materials under sharp contact loading (indentation) is important for their applications since this knowledge is crucial for identifying the origin of flaw and scratch formation on their surfaces. As a newly emerged glass family, metal-organic framework (MOF) glasses have not been studied concerning the mechanism of their indentation-induced deformation. Here, we explore this mechanism for ZIF-62 glass (a typical MOF glass system). The fractions of densification and shear flow during indentation were determined by atomic force microscopy, while the elastic deformation was measured via nanoindentation. The results show that ZIF-62 glass deforms primarily through densification and elastic deformation under the sharp contact loading. Significant pile-ups around indents were not observed, indicating that no or limited shear flow occurs in the glass during indentation. This behavior could be attributed to three structural factors, namely, high free volume, easily densified glass structure, and limited translational mobility of structural units.
揭示脆性材料在尖锐接触载荷（压痕）下的变形机制对其应用很重要，因为这一知识对于确定其表面缺陷和划痕形成的起源至关重要。作为一种新出现的玻璃家族，金属有机框架（MOF）玻璃尚未针对其压痕诱导变形的机制进行研究。在此，我们探索ZIF-62玻璃（一种典型的MOF玻璃体系）的这一机制。通过原子力显微镜确定压痕过程中致密化和剪切流动的比例，同时通过纳米压痕测量弹性变形。结果表明，ZIF-62玻璃在尖锐接触载荷下主要通过致密化和弹性变形发生变形。未观察到压痕周围有明显的堆积现象，这表明玻璃在压痕过程中没有或仅有有限的剪切流动。这种行为可归因于三个结构因素，即高自由体积、易于致密化的玻璃结构以及结构单元有限的平移迁移率。
