In situ observation of the pressure-induced amorphization of siliceous faujasite.

Zeolites are formed from rigid tetrahedral aluminosilicate units corner-linked to form rings which are in turn fully corner-linked to form larger units, resulting in open structures with large pores and often cavities. When subjected to pressure, zeolites can undergo pressure-induced amorphization and the resulting amorphous form has a structure and physical properties that are different from amorphous forms (often glasses) produced more conventional routes. It is the aim of this experiment to evaluate the changes in zeolite structure (i.e., the progressive loss of long-range order) up and to the point of amorphization at pressures of 2.2 GPa. This in situ experiment will use a completely siliceous zeolite, which lacks aluminium and charge balancing cations and is also water-free. High pressure neutron diffraction data will be collected in two geometries, transverse detector banks will be used to collect data to high values of scattering vector, which will be used to monitor the progressive collapse of the zeolite while low Q data will be collected using longitudal banks to determine the topology and porosity retention in the high-pressure amorphous form.

沸石(Zeolites)由刚性四面体铝硅酸盐单元经顶角连接形成环，这些环再通过完全顶角连接构成更大的结构单元，最终形成带有大孔隙与空腔的开放骨架结构。当受到压力作用时，沸石可发生压力诱导非晶化，其生成的非晶态产物的结构与物理性质，均不同于通过常规制备路径（通常为玻璃化途径）得到的非晶态材料。本实验旨在评估沸石在2.2 GPa压力下直至非晶化临界点的结构变化，即长程有序性的逐步丧失过程。本次原位实验将采用纯硅沸石，该沸石不含铝与电荷平衡阳离子，且无水。实验将通过两种几何构型采集高压中子衍射数据：采用横向探测器阵列采集高散射矢量区间的数据，用于监测沸石的逐步坍塌过程；同时采用纵向探测器阵列采集低Q区间的数据，以确定高压非晶态产物的骨架拓扑结构与孔隙保留情况。