Modeling of temperature profiles in an environmental transmission electron microscope using computational fluid dynamics

Mortensen, Peter Mølgaard; Hansen, Thomas Willum; Wagner, Jakob Birkedal; Jensen, Anker Degn

doi:10.1016/j.ultramic.2014.12.007

Cited by 14 publications

(6 citation statements)

References 24 publications

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“…In the first instance, we can confirm the general agreement and synchronicity of the signals from the system-level Barocel gauge and the electron scattering from the specimen area gas column, as shown in S4 Fig . Within our measurement resolution, signals are well-synchronized and correlated, in agreement with previous computational fluid dynamics simulations [ 26 ]. The distinct measurement points are within a uniform, unobstructed pressure chamber in this case [ 26 ], and the previously noted poor correlation between specimen area pressure changes and RGA readings, was not an issue in this case.…”

Section: Resultssupporting

confidence: 88%

“…Within our measurement resolution, signals are well-synchronized and correlated, in agreement with previous computational fluid dynamics simulations [ 26 ]. The distinct measurement points are within a uniform, unobstructed pressure chamber in this case [ 26 ], and the previously noted poor correlation between specimen area pressure changes and RGA readings, was not an issue in this case. Thus, having validated the synchronicity between the pressure gauge and EELS readings, we can proceed with more quantitative analysis of electron scattering as a function of nominal pressure.…”

Section: Resultssupporting

confidence: 88%

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Water without windows: Evaluating the performance of open cell transmission electron microscopy under saturated water vapor conditions, and assessing its potential for microscopy of hydrated biological specimens

Cassidy¹,

Yamashita²,

Cheung³

et al. 2017

PLoS ONE

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We have performed open cell transmission electron microscopy experiments through pure water vapor in the saturation pressure regime (>0.6 kPa), in a modern microscope capable of sub-Å resolution. We have systematically studied achievable pressure levels, stability and gas purity, effective thickness of the water vapor column and associated electron scattering processes, and the effect of gas pressure on electron optical resolution and image contrast. For example, for 1.3 kPa pure water vapor and 300kV electrons, we report pressure stability of ± 20 Pa over tens of minutes, effective thickness of 0.57 inelastic mean free paths, lattice resolution of 0.14 nm on a reference Au specimen, and no significant degradation in contrast or stability of a biological specimen (M13 virus, with 6 nm body diameter). We have also done some brief experiments to confirm feasibility of loading specimens into an in situ water vapor ambient without exposure to intermediate desiccating conditions. Finally, we have also checked if water experiments had any discernible impact on the microscope performance, and report pertinent vacuum and electron optical data, for reference purposes.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 88%

Water without windows: Evaluating the performance of open cell transmission electron microscopy under saturated water vapor conditions, and assessing its potential for microscopy of hydrated biological specimens

Cassidy¹,

Yamashita²,

Cheung³

et al. 2017

PLoS ONE

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show abstract

“…The temperature measured by the thermocouple of the heating holder overestimates the true temperature at the position of the thin lamella [38,39]. This difference is influenced by the gas atmosphere and the conductivity of the support.…”

Section: Factors Affecting Eftem Resultsmentioning

confidence: 95%

Energy-filtered environmental transmission electron microscopy for the assessment of solid–gas reactions at elevated temperature: NiO/YSZ–H2 as a case study

et al. 2016

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A novel approach, which is based on the analysis of sequences of images recorded using energy-filtered transmission electron microscopy and can be used to assess the reaction of a solid with a gas at elevated temperature, is illustrated for the reduction of a NiO/ceramic solid oxide fuel cell anode in 1.3mbar of H2. Three-window elemental maps and jump-ratio images of the O K edge and total inelastic mean free path images are recorded as a function of temperature and used to provide local and quantitative information about the reaction kinetics and the volume changes that result from the reaction. Under certain assumptions, the speed of progression of the reaction front in all three dimensions is obtained, thereby providing a three-dimensional understanding of the reaction.

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“…Therefore, the molten phase will attain a varying composition through the industrial converter and across the individual catalyst pellets. In contrast, the gas cell employed in the electron microscope resembles a differential reactor with a gas composition close to that entering the microscope, , and the Raman cell is more closely described as a continuously stirred tank reactor. In the electron microscope, the total pressure is at the level of a few mbar, and in the Raman setup, the total pressure is 1 bar.…”

Section: Resultsmentioning

confidence: 99%

Vanadia-Based Catalysts for the Sulfur Dioxide Oxidation StudiedIn Situby Transmission Electron Microscopy and Raman Spectroscopy

et al. 2017

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The industrial production of sulfuric acid involves the oxidation of sulfur dioxide, which is catalyzed by a silica-supported phase consisting of V 2 O 5 species dissolved in a pyrosulfate melt with Na, K, and Cs added as promoters. As the molten phase is only present during the catalytic reaction and solidifies at room temperature, in situ studies are necessary to address the working state of the SO 2 oxidation catalyst. Here we combine transmission electron microscopy (TEM) and Raman spectroscopy to study in situ a vanadia-based SO 2 oxidation catalyst upon activation and reaction in an SO 2 / O 2 gas mixture. The observations reveal that the vanadia phase dynamically redistributes on the support upon heating in an SO 2 /O 2 mixture. Surprisingly, the vanadia phase can disperse into partially crystalline islands on convex surfaces of the silica support and into a molten state on concave areas of the support. The presence of Cs was found to lower the temperature for the pyrosulfate formation and stabilize vanadium in the active V V state by forming linked structures at low temperature. Combining these in situ studies with activity measurements leads to the proposal that the linked structures stabilize the catalyst in the active state.

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Modeling of temperature profiles in an environmental transmission electron microscope using computational fluid dynamics

Cited by 14 publications

References 24 publications

Water without windows: Evaluating the performance of open cell transmission electron microscopy under saturated water vapor conditions, and assessing its potential for microscopy of hydrated biological specimens

Water without windows: Evaluating the performance of open cell transmission electron microscopy under saturated water vapor conditions, and assessing its potential for microscopy of hydrated biological specimens

Energy-filtered environmental transmission electron microscopy for the assessment of solid–gas reactions at elevated temperature: NiO/YSZ–H2 as a case study

Vanadia-Based Catalysts for the Sulfur Dioxide Oxidation StudiedIn Situby Transmission Electron Microscopy and Raman Spectroscopy

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