scholarly journals Resolving atomic SAPO-34/18 intergrowth architectures for methanol conversion by identifying light atoms and bonds

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Boyuan Shen ◽  
Xiao Chen ◽  
Xiaoyu Fan ◽  
Hao Xiong ◽  
Huiqiu Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Methanol Conversion ◽  
Real Space ◽  
Zeolite Catalysts ◽  
Structure Property ◽  
Synthesis Conditions ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Micro Structures ◽  
Catalytic Performances

AbstractThe micro-structures of catalyst materials basically affect their macro-architectures and catalytic performances. Atomically resolving the micro-structures of zeolite catalysts, which have been widely used in the methanol conversion, will bring us a deeper insight into their structure-property correlations. However, it is still challenging for the atomic imaging of silicoaluminophosphate zeolites by electron microscopy due to the limits of their electron beam sensitivity. Here, we achieve the real-space imaging of the atomic lattices in SAPO-34 and SAPO-18 zeolites, including the Al–O–P atoms and bonds, by the integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM). The spatial distribution of SAPO-34 and SAPO-18 domains in SAPO-34/18 intergrowths can be clearly resolved. By changing the Si contents and templates in feed, we obtain two SAPO-34/18 catalysts, hierarchical and sandwich catalysts, with highly-mixed and separated SAPO-34 and SAPO-18 lattices respectively. The reduced diffusion distances of inside products greatly improve the catalytic performances of two catalysts in methanol conversion. Based on the observed distributions of lattices and elements in these catalysts, we can have a preliminary understanding on the correlation between the synthesis conditions and structures of SAPO-34/18 intergrowth catalysts to further modify their performances based on unique architectures.

TEM/STEM Characterization of Rapidly Solidified Aluminum Alloys

1985 ◽  
Vol 43 ◽  
pp. 30-31
Author(s):  
R. J. Kar ◽  
T. P. McHale ◽  
R. T. Kessler
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Alloys ◽  
High Strength ◽  
Advanced Materials ◽  
Structure Property ◽  
Aerospace Applications ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Rapidly Solidified

Low-density and high strength-type rapidly solidified (RST) aluminum alloys offer promise for structural aerospace applications. At Northrop, as part of a continuing program to establish structure-property relationships in advanced materials, detailed transmission electron microscopy (TEM)/scanning transmission electron microscopy (STEM) of candidate RST aluminum-lithium (Al-Li) and high strength (7XXX-type) aluminum-copper-magnesium-zinc (Al-Cu-Mg-Zn) alloys is routinely performed. This paper describes typical microstructural features that we have observed in these alloys.Figure 1 illustrates the microstructure of an inert-gas atomized RST Al-Li-Cu-Mg-Zr alloy. Frequently the grain boundaries are decorated with continuous or semi-continuous stringers of oxide that are relatively opaque to the incident electron beam. These have been identified to be Al-,Mg-, and Li- containing oxides present on powder particle surfaces prior to consolidation, and which have not been adequately broken up and dispersed by post-consolidation processing. The microstructures of these alloys are generally characterized by unrecystallized grains and equiaxed sub-grains pinned by fine (0.2μm) precipitates. These have been identified to be Al3Zr dispersoids using a combination of selected area diffraction/energy-dispersive x-ray (SAD/EDX) methods.

Possibility of an integrated transmission electron microscope: enabling complex in-situ experiments

2021 ◽  
Vol 56 (9) ◽  
pp. 5309-5320
Author(s):  
Khalid Hattar ◽  
Katherine L. Jungjohann
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Extreme Environments ◽  
Structure Property ◽  
Multispectral Data ◽  
Transmission Electron ◽  
Holistic Understanding ◽  
In Situ Experiments ◽  
Scanning Transmission

Abstract Multimodal in-situ experiments are the wave of the future, as this approach will permit multispectral data collection and analysis during real-time nanoscale observation. In contrast, the evolution of technique development in the electron microscopy field has generally trended toward specialization and subsequent bifurcation into more and more niche instruments, creating a challenge for reintegration and backward compatibility for in-situ experiments on state-of-the-art microscopes. We do not believe this to be a requirement in the field; therefore, we propose an adaptive instrument that is designed to allow nearly simultaneous collection of data from aberration-corrected transmission electron microscopy (TEM), probe-corrected scanning transmission electron microscopy, ultrafast TEM, and dynamic TEM with a flexible in-situ testing chamber, where the entire instrument can be modified as future technologies are developed. The value would be to obtain a holistic understanding of the underlying physics and chemistry of the process-structure–property relationships in materials exposed to controlled extreme environments. Such a tool would permit the ability to explore, in-situ, the active reaction mechanisms in a controlled manner emulating those of real-world applications with nanometer and nanosecond resolution. If such a powerful tool is developed, it has the potential to revolutionize our materials understanding of nanoscale mechanisms and transients. Graphical Abstract

scholarly journals Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM): From Scanning Nanodiffraction to Ptychography and Beyond

2019 ◽  
Vol 25 (3) ◽  
pp. 563-582 ◽  
Author(s):  
Colin Ophus
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Real Space ◽  
Contrast Imaging ◽  
Strain Mapping ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractScanning transmission electron microscopy (STEM) is widely used for imaging, diffraction, and spectroscopy of materials down to atomic resolution. Recent advances in detector technology and computational methods have enabled many experiments that record a full image of the STEM probe for many probe positions, either in diffraction space or real space. In this paper, we review the use of these four-dimensional STEM experiments for virtual diffraction imaging, phase, orientation and strain mapping, measurements of medium-range order, thickness and tilt of samples, and phase contrast imaging methods, including differential phase contrast, ptychography, and others.

Modeling Atomic-Resolution Scanning Transmission Electron Microscopy Images

2007 ◽  
Vol 14 (1) ◽  
pp. 48-59 ◽  
Author(s):  
Scott D. Findlay ◽  
Mark P. Oxley ◽  
Leslie J. Allen
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Real Space ◽  
Visual Interpretation ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Analysis Technique ◽  
Scanning Transmission

A real-space description of inelastic scattering in scanning transmission electron microscopy is derived with particular attention given to the implementation of the projected potential approximation. A hierarchy of approximations to expressions for inelastic images is presented. Emphasis is placed on the conditions that must hold in each case. The expressions that justify the most direct, visual interpretation of experimental data are also the most approximate. Therefore, caution must be exercised in selecting experimental parameters that validate the approximations needed for the analysis technique used. To make the most direct, visual interpretation of electron-energy-loss spectroscopic images from core-shell excitations requires detector improvements commensurate with those that aberration correction provides for the probe-forming lens. Such conditions can be relaxed when detailed simulations are performed as part of the analysis of experimental data.

scholarly journals A Review of Grain Boundary and Heterointerface Characterization in Polycrystalline Oxides by (Scanning) Transmission Electron Microscopy

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 878
Author(s):  
Hasti Vahidi ◽  
Komal Syed ◽  
Huiming Guo ◽  
Xin Wang ◽  
Jenna Laurice Wardini ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Experimental Studies ◽  
Atomic Scale ◽  
Polycrystalline Materials ◽  
Structure Property ◽  
Ceramic Oxides ◽  
Structure Property Relationships ◽  
Transmission Electron ◽  
Scanning Transmission

Interfaces such as grain boundaries (GBs) and heterointerfaces (HIs) are known to play a crucial role in structure-property relationships of polycrystalline materials. While several methods have been used to characterize such interfaces, advanced transmission electron microscopy (TEM) and scanning TEM (STEM) techniques have proven to be uniquely powerful tools, enabling quantification of atomic structure, electronic structure, chemistry, order/disorder, and point defect distributions below the atomic scale. This review focuses on recent progress in characterization of polycrystalline oxide interfaces using S/TEM techniques including imaging, analytical spectroscopies such as energy dispersive X-ray spectroscopy (EDXS) and electron energy-loss spectroscopy (EELS) and scanning diffraction methods such as precession electron nano diffraction (PEND) and 4D-STEM. First, a brief introduction to interfaces, GBs, HIs, and relevant techniques is given. Then, experimental studies which directly correlate GB/HI S/TEM characterization with measured properties of polycrystalline oxides are presented to both strengthen our understanding of these interfaces, and to demonstrate the instrumental capabilities available in the S/TEM. Finally, existing challenges and future development opportunities are discussed. In summary, this article is prepared as a guide for scientists and engineers interested in learning about, and/or using advanced S/TEM techniques to characterize interfaces in polycrystalline materials, particularly ceramic oxides.

scholarly journals Real space crystallography of a complex metallic alloy: high-angle annular dark-field scanning transmission electron microscopy of o-Al4(Cr,Fe)

2014 ◽  
Vol 47 (3) ◽  
pp. 1026-1031 ◽  
Author(s):  
Roberto Gaspari ◽  
Rolf Erni ◽  
Yadira Arroyo ◽  
Magdalena Parlinska-Wojtan ◽  
Julia Dshemuchadse ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Real Space ◽  
Dark Field ◽  
High Angle ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) has been performed along the low-index zone axes of the o-Al4(Cr,Fe) complex metallic alloy to obtain a real-space representation of the crystal structure and to elucidate the material's inherent structural disorder. By comparing experiments with multislice STEM simulations, the model previously suggested by X-ray diffraction is further refined to provide a new set of positions and occupancies for the transition metal atoms.Pmnbis suggested as the new space group for the o-Al4(Cr,Fe) phase. A nonperiodic layer-type modulation, averaged out in bulk diffraction methods, is detected, corroborating the need for complementing bulk diffraction analysis with real-space imaging to derive the true crystal structure of Al4(Cr,Fe).

The Formation and Utility of Sub-Angstrom to Nanometer-Sized Electron Probes in the Aberration-Corrected Transmission Electron Microscope at the University of Illinois

2010 ◽  
Vol 16 (2) ◽  
pp. 183-193 ◽  
Author(s):  
Jianguo Wen ◽  
James Mabon ◽  
Changhui Lei ◽  
Steve Burdin ◽  
Ernie Sammann ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Real Space ◽  
Dark Field ◽  
Atomic Scale ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractWe evaluate the probe forming capability of a JEOL 2200FS transmission electron microscope equipped with a spherical aberration (Cs) probe corrector. The achievement of a real space sub-Angstrom (0.1 nm) probe for scanning transmission electron microscopy (STEM) imaging is demonstrated by acquisition and modeling of high-angle annular dark-field STEM images. We show that by optimizing the illumination system, large probe currents and large collection angles for electron energy loss spectroscopy (EELS) can be combined to yield EELS fine structure data spatially resolved to the atomic scale. We demonstrate the probe forming flexibility provided by the additional lenses in the probe corrector in several ways, including the formation of nanometer-sized parallel beams for nanoarea electron diffraction, and the formation of focused probes for convergent beam electron diffraction with a range of convergence angles. The different probes that can be formed using the probe corrected STEM opens up new applications for electron microscopy and diffraction.

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