Design and use of a flow cell for observing evolving solid-fluid interfaces in a scanning electron microscope

The development of a flow cell dedicated to the direct observation of the interaction between a fluid (the fluid being a gas or a liquid) and a solid in a scanning electron microscope is reported. This fluid flow cell has two main differences and advantages compared with existing devices. Firstly, it has been designed to allow direct observation of complex corrosion, dissolution, nucleation and/or growth processes taking place at solid materials surface. Secondly, the fluid circulates continuously in the cell maintaining constant chemical conditions thanks to the renewal of the fluid in contact with the solid. An electron-transparent SiN_x window is used to isolate the interior of the flow cell from the vacuum of the SEM chamber. The surface of the sample is observed by recording images in backscattered electron mode. The contrasts observed in this mode are in good agreement with the results of Monte-Carlo simulations of electron trajectories and backscattered electron emissions carried out on model systems. Monte-Carlo simulations are used to determine the operating limits of the flow cell.