Improving in situ liquid SEM imaging of particles

Abstract

This work presents in situ imaging of synthesized boehmite (γ‐AlOOH) particles ranging from 20 to 100 nm, suspended in liquid, in a vacuum compatible microfluidic sample holder using a scanning electron microscopy (SEM) under the high vacuum mode and highlights the advantage of in situ liquid imaging of colloids. Nanometer‐sized boehmite particles in high‐level radioactive wastes at the Hanford site are known to be difficult to dissolve and cause rheological problems for processing in the nuclear waste treatment plant. Therefore, it is important to characterize boehmite particles and understand how they form aggregates in the liquid state. Several technical advancements are made to optimize in situ liquid SEM chemical imaging resulting in the improved ability to obtain secondary electron (SE), backscattered electron (BSE) images, and energy dispersive X‐ray spectroscopy (EDX) spectra. Moreover, our results show mixed particles could be studied and identified based on the particle shape and elemental composition using in situ SEM imaging and EDX. Thus, we provide a new and improved approach to observe the evolution of particle dispersion and stability in liquid under conditions similar to those in the waste tank.

Microscopic Techniques for the Analysis of Micro and Nanostructures of Biopolymers and Their Derivatives

“…However, limitations arising due to the lenses and the sample preparations restricts its working resolution to the order of 1-2 nm [112]. The SEM analysis can be carried out under high vacuum or low vacuum and even under wet conditions [113]. Samples for the analysis of SEM are typically frozen under liquid nitrogen and coated to avoid charging and metal shadowing or common deployment of negative staining for contrast enhancement [114].…”

In situ liquid SEM imaging analysis revealing particle dispersity in aqueous solutions

“…The solutions were mixed using Vortex for 1 min. The unadjusted pH of the stock solution is ~ 4.6 9 . Two factors, pH and ionic strength, were studied in this work.…”

“…Once the holes were prepared, a boehmite solution was injected into SALVI device and the two opening ends were sealed by polyetheretherketone union. During the process of taking SE images, the working distance (WD) was set to optimize the imaging results, ranging from several mm to approximately 10 mm 9 . The electron beam current varied from 0.47 nA to 0.55 nA, and the accelerating voltage varied from 5 kV to 10 kV to optimize image resolution.…”

Dynamic Imaging of Nanostructures in an Electrolyte with a Scanning Electron Microscope

“…However, these approaches involving condensed liquids and sealed capsules are less suitable for studying dynamic chemical and electrochemical processes because they either do not allow control over the chemical environment or lack important features required in electrochemistry such as continuous fluid flow and electrodes to apply an external bias voltage or to be used as a reference. While there are home-made LC-SEM systems that also incorporate flow (Yang et al, 2013;Kolmakov, 2016;Yu et al, 2019) or allow electrochemical measurements (Jensen et al, 2013;Jensen et al, 2014;Kolmakov, 2016;Velasco-Velez et al, 2020), these systems commonly utilize a single membrane window with a relatively large liquid reservoir underneath, which affects the final resolution due to the extended interaction volume of the primary electrons. The LC geometry used in TEM holders with a pair of top and bottom silicon nitride membranes has, to the best of our knowledge, not yet been reported.…”