Optimization of secondary electron imaging of zeolite materials using in-lens techniques

Zeolites have been used in many more industrial applications; the most recent one that has caused a big revolution in control of NOx reduction is as selective catalytic reduction (SCR) catalysts to control auto emissions. The special porous structure lets the zeolite material suitable for selecting the molecules of certain size. Unfortunately, this porous property coupled with a charge imbalance imposed by Al-Si oxide ratios makes the zeolite electron-beam sensitive for characterization of its structure. SEM is a primary instrument used to observe and analyze the zeolites in industry. Secondary electron microscopy provides a critical and essential way to analyze the topographic information of the material surface. The secondary electron images illustrate the surface morphology, topography, particle shape and size. Because of the sensitivity of the zeolite, the low accelerating voltage secondary electron microscopy is preferred in order to preserve its original structure and crystallinity. The adjustable accelerating voltage of the electron gun in SEM makes it possible to choose an optimal low voltage to image the zeolite. [1]