Introducing and Controlling Water Vapor in Gas-Cell Microscopy Experiments

K. A. Unocic, F. S. Walden, N. L. Marthe, W. C. Bigelow, L. F. Allard , 2019
Atmosphere tip and gas handling manifold
Image courtesy of Microscopy and Microanalysis

Abstract

The presence of water vapor is central to many materials applications (e.g., in steam generators, biomass-fired plants, turbine engines, fuel cells, and catalysts). The role of water vapor is of particular interest in the degradation of blades in turbines fired by coal-derived synthesis gas or hydrogen having a higher water vapor content than in conventional turbines. The presence of water vapor can substantially decrease the lifetime of the thermal barrier coatings protecting turbine blades by accelerating the oxidation rates. However, there is currently a lack of basic understanding of the degradation mechanisms and a lack of reaction kinetic data at the nanoscale level, which can substantially improve computational modeling for components lifetime predictions. Thus, in situ experiments could bridge this gap. Performing in situ STEM gas reactions with water vapor in a closed-cell MEMS-based specimen holder is challenging due to condensation of vapor along the narrow (<200μm) supply and return capillaries, and inside the reactor holder, since these lines cannot be effectively heated. We have developed methods and protocols to introduce, control, and quantify the amount of water vapor in a MEMS-based closed-cell in situ reactor system (Protochips AtmosphereTM) for studies focused on the effects of environmental exposure on high-temperature structural materials and catalysts.

Impact Statement

The authors developed methods and protocols to introduce, control, and quantify the amount of water vapor in a MEMS-based closed-cell in situ reactor system (Protochips AtmosphereTM) for studies focused on the effects of environmental exposure on high-temperature structural materials and catalysts.