A novel technique for the measurement of the coating layer thickness of fine particles was developed in this work based on cross-sectioning of micrometre-sized single coated particles using focused ion beam (FIB) milling. This technique was tested on two batches of aerogel particles coated with thin coatings in a spouted bed. The FIB milling procedure consisted of two steps. First, the desired part of the coated particle was removed using a high ion beam current. The resulting cross-sectioned area was then polished using a lower ion beam current to make the cross-section clearly visible. The FIB milling process was controlled with simultaneous scanning electron microscopy (SEM). Afterwards, the coating layer thickness was evaluated using the SEM images.

The coating layer was successfully applied on the porous aerogel microparticles in the spouted bed. The coating uniformity of the highly porous particles increased with increasing sprayed coating solution amount, with up to 91% of the particle pores being covered. The FIB-cross-sectioning technique using an ion beam of 2.50 nA for the first milling and 0.43 nA for polishing of the surface resulted in successful generation of cross-sections of representative particles with a visible particle core and coating layer. A coating layer thickness of approximately 700 nm was achieved on particles with sizes of below 45 μm.

在这项工作中，基于使用聚焦离子束（FIB）铣削微米尺寸的单个被覆颗粒的横截面，开发了一种用于测量细颗粒的被覆层厚度的新技术。该技术已在两批在喷射床中涂有薄涂层的气凝胶颗粒上进行了测试。FIB铣削过程包括两个步骤。首先，使用高离子束电流除去涂覆颗粒的所需部分。然后，使用较低的离子束电流对所得的横截面区域进行抛光，以使该横截面清晰可见。FIB铣削过程由同时扫描电子显微镜（SEM）控制。之后，使用SEM图像评估涂层厚度。

将涂层成功地涂覆在喷出床中的多孔气凝胶微粒上。高度多孔的颗粒的涂层均匀性随喷涂溶液量的增加而增加，最多可覆盖91％的颗粒孔。FIB横截面技术使用的离子束在第一次研磨时为2.50 nA，在表面抛光时为0.43 nA，从而成功生成了具有可见粒子核和涂层的代表性粒子的横截面。在尺寸小于45μm的颗粒上获得了大约700 nm的涂层厚度。