Sample Preparation Methodologies forIn SituLiquid and Gaseous Cell Analytical Transmission Electron Microscopy of Electropolished Specimens

Abstract

In recent years, an increasing number of studies utilizing in situ liquid and/or gaseous cell scanning/transmission electron microscopy (S/TEM) have been reported. Because of the difficulty in the preparation of suitable specimens, these environmental S/TEM studies have been generally limited to studies of nanoscale structured materials such as nanoparticles, nanowires, or sputtered thin films. In this paper, we present two methodologies which have been developed to facilitate the preparation of electron-transparent samples from conventional bulk metals and alloys for in situ liquid/gaseous cell S/TEM experiments. These methods take advantage of combining sequential electrochemical jet polishing followed by focused ion beam extraction techniques to create large electron-transparent areas for site-specific observation. As an example, we illustrate the application of this methodology for the preparation of in situ specimens from a cold-rolled Type 304 austenitic stainless steel sample, which was subsequently examined in both 1 atm of air as well as fully immersed in a H2O environment in the S/TEM followed by hyperspectral imaging. These preparation techniques can be successfully applied as a general procedure for a wide range of metals and alloys, and are suitable for a variety of in situ analytical S/TEM studies in both aqueous and gaseous environments.

Correlative Microscopy: Elucidating the Mechanisms of SCC in Structural Alloys in PWR Environments

“…Using "thick" (250-300 nm) "hybrid" [4] specimens with the Protochips Atmosphere in situ system, it was possible to generate comparable DIGM to that observed in bulk ex situ samples [5]. Finally, by exposing stressed 4 pt.…”

Application of In Situ Liquid Cell Transmission Electron Microscopy in Corrosion Studies: A Critical Review of Challenges and Achievements

“…Taking into account these concerns, a hybrid sample preparation procedure dedicated to liquid cells has recently been established 69,70 . In this methodology, which is comprised of three basic steps, electropolished TEM thin-foil disks are initially prepared.…”

“…(c) Attaching the micromanipulator to the area of interest to be freed by milling off supporting material, (d) positioning the specimen above the window, (e) cutting off the micromanipulator and welding the specimen to the liquid cell by organometallic Pt deposition. Reprinted from Zhong et al,69 with permission from Cambridge University Press.…”

Practical Aspects of Electrochemical Corrosion Measurements During In Situ Analytical Transmission Electron Microscopy (TEM) of Austenitic Stainless Steel in Aqueous Media

“…This is due, in part, to traditional methodology of preparing TEM specimens which begins with a bulk (nonelectron transparent) sample and ends with thin (electron transparent) areas whose periphery is surrounded by a bulk rim (Kestel, 1986). To facilitate this study, a hybrid preparation protocol was developed, which employs a combination of both electrochemical polishing and FIB extraction, the details of this hybrid technique are described elsewhere (Zhong et al, 2016). The base material for this work was cold-rolled Type 304 stainless steel (SS) ( Table 1), which was mechanically thinned to~100 µm in thickness before punching out 3 mm diameter discs.…”

“…The disc specimens were then electropolished in 20% HClO 4 -80% CH 3 OH at −33°C and 20 V, as is typical for conventional plan-view TEM studies. From the plan-view specimens, site-specific extraction of an electron-transparent thin area was accomplished using an FEI Quanta 3D Dual Beam FIB (FEI Company) (Zhong et al, 2016). Hybrid specimens were then Figure 2.…”