Abstract
Cryo-based atom probe tomography has been applied to directly reveal the water-solid interface and hydrated corrosion layers making up the nanoscale porous structure of a corroded borosilicate glass in its native aqueous environment. The analysis includes morphology and compositional mapping of the inner gel/glass interface, isolation of a tomographic sub-volume of the tortuous water-filled gel, and comparison of the gel structure with simulations. The nanoscale porous structure is qualitatively consistent with that of the molecular dynamics simulation, enabling in greater confidence in both interrogations. Comparison of the gel/glass interface between desiccated and cryogenically preserved samples reveals consistently abrupt B dissolution behavior and quantitative differences in the apparent H ingress into the glass. These comparisons give some guidance to future experimental approaches to understanding glass corrosion behavior. More broadly, the cryogenic preservation and 3D visualization of the native water/solid structure in 3D at the nanoscale has direct relevance to a wide range of materials systems beyond glass science.
Highlights
The liquid-solid interface plays an essential role in many phenomena encountered in biological, chemical, and physical processes relevant to both fundamental and applied science; corrosion is one major globally-relevant area of science that has a profound socioeconomic impact
Two successful APT specimens were produced from this single particle; one of which targeted the bulk solid water/outer gel interface and is described in a separate method-focused manuscript[5], and one which targeted the hydrated nanoporous inner gel/pristine glass interface and is the subject of the work presented here
APT analysis of water-solid and highly porous layers (OG) must utilize cryogenic specimen preparation routes as preservation of the native water is inherent to their analyses
Summary
The liquid-solid interface plays an essential role in many phenomena encountered in biological, chemical, and physical processes relevant to both fundamental and applied science; corrosion is one major globally-relevant area of science that has a profound socioeconomic impact. Following work by our group to develop both the hardware[4], and specimen handling and preparation protocols of cryogenically-cooled specimens[5], the work here reports on local atom-by-atom composition gradients within a water-filled nanoporous corroded glass using cryogenic atom probe tomography (cryo-APT) Using these newly developed cryogenic tools reveals surprising insights into the corroded glass structure and corrosion processes that were previously unobtainable by conventional microscopy approaches. We report solid and dissolved ion composition gradients across the outer gel (OG)/inner gel (IG)/glass interface regions, as well as map the 3D nanoscale porous structure of the inner gel We anticipate that this cryo-based specimen preparation and analysis approach can be further applied to the study of liquid-solid chemistry within nano-confined geometries and buried interfaces. An extension of the work presented here can be applied to map ionic and macromolecular gradients across liquid-solid interface of biological membranes; hydrated phases within bio and geominerals; ionic distributions across liquid-solid interface within nano-confined volumes such as crack tips or advanced battery materials
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