Quantifying the 3D Distribution of Pd Nanocatalysts Supported on Mesoporous Carbon for Furfural Hydrogenation

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A comparison of in- and ex-situ shear bands in metallic glass by transmission electron microsopy

Plastic deformation of metallic glasses performed at temperatures well below the glass transition proceeds via the formation of shear bands. In this contribution shear bands originating from in situ tensile tests of Al$_{88}$Y$_{7}$Fe$_{5}$ melt-spun ribbons conducted in a transmission electron microscope are compared with ones which had formed ex situ during cold rolling. The observed contrasts for shear bands generated in situ at the edges of thin electron-transparent foils are shown to be related to a meniscus-like foil thickness reduction. In comparison with ex situ samples, alternating contrast changes due to volume changes are missing and the shear band width is a factor of 15 larger. The meniscus-like shear band profile is accounted for by the thin foil allowing volume increase due to shear deformation to annihilate via the free surfaces of the thin foil and the sheared zones to widen.Comment: submitted to Scripta Materiali

MSLE: An ontology for Materials Science Laboratory Equipment. Large-Scale Devices for Materials Characterization

This paper introduces a new ontology for Materials Science Laboratory Equipment, termed MSLE. A fundamental issue with materials science laboratory (hereafter lab) equipment in the real world is that scientists work with various types of equipment with multiple specifications. For example, there are many electron microscopes with different parameters in chemical and physical labs. A critical development to unify the description is to build an equipment domain ontology as basic semantic knowledge and to guide the user to work with the equipment appropriately. Here, we propose to develop a consistent ontology for equipment, the MSLE ontology. In the MSLE, two main existing ontologies, the Semantic Sensor Network (SSN) and the Material Vocabulary (MatVoc), have been integrated into the MSLE core to build a coherent ontology. Since various acronyms and terms have been used for equipment, this paper proposes an approach to use a Simple Knowledge Organization System (SKOS) to represent the hierarchical structure of equipment terms. Equipment terms were collected in various languages and abbreviations and coded into the MSLE using the SKOS model. The ontology development was conducted in close collaboration with domain experts and focused on the large-scale devices for materials characterization available in our research group. Competency questions are expected to be addressed through the MSLE ontology. Constraints are modeled in the Shapes Query Language (SHACL); a prototype is shown and validated to show the value of the modeling constraints.Comment: Submitted to Materials Today Communicatio

In Situ Generated Shear Bands in Metallic Glass Investigated by Atomic Force and Analytical Transmission Electron Microscopy

Plastic deformation of metallic glasses performed at temperatures well below the glass transition proceeds via the formation of shear bands. In this contribution, we investigated shear bands originating from in situ tensile tests of Al88Y7Fe5 melt-spun ribbons performed under a transmission electron microscope. The observed contrasts of the shear bands were found to be related to a thickness reduction rather than to density changes. This result should alert the community of the possibility of thickness changes occurring during in situ shear band formation that may affect interpretation of shear band properties such as the local density. The observation of a spearhead-like shear front suggests a propagation front mechanism for shear band initiation here

Designing Structurally Ordered Pt/Sn Nanoparticles in Ionic Liquids and their Enhanced Catalytic Performance

Multimetallic nanoparticles (NPs) often exhibit enhanced catalytic properties that differ from their parent materials. Carefully exploring the structures of multimetallic NPs is a prerequisite for understanding the structure‐ and composition‐associated properties. Herein, intermetallic Pt/Sn NPs with tunable compositions are designed exploiting the beneficial properties of ionic liquids (ILs) in a one‐pot synthetic procedure. Metal salt precursors are reduced with triethylhydridoborate, whereby the cation of the triethylhydridoborate is adapted to the cation of the IL. Both the initial metal precursor ratio and the type of IL influence the structure of the NPs, with the effect of the IL being more pronounced. PtSn nanocrystals are obtained as phase pure products under optimized reaction conditions, whereby a microwave‐assisted approach leads to higher crystallinity. In the hydrogenation of α,β‐unsaturated aldehydes, the catalytic performance obviously depend on the NP composition. In bimetallic Pt/Sn NPs, higher Pt content leads to increased conversion, while increase in Sn increases selectivity to the cinnamic alcohol

Unveiling local atomic bonding and packing of amorphous nanophases via independent component analysis facilitated pair distribution function

Amorphous nanophases play a significant role for the properties of a variety of nanoscale heterogeneous materials. Experimental characterization of the atomic arrangement of the amorphous structure, including nanoscale structural variations, is one of the main challenges limiting the rational design of the materials. Here, an approach to characterize local bonding and atomic packing in complex nanomaterials is introduced. Building on scanning transmission electron microscopy (STEM) and pair distribution function analysis (PDF) to record local diffraction information with nanometer spatial resolution, we show that independent component analysis for “blind source separation” of mixed information due to projection effects in STEM-PDF, enables full separation of these signals. The unprecedented information allows determining the structure of individual nanoscale phases and identifying the compounds inside. We analyzed a FeZr/ZrO2 multilayer as proof of principle, and discovered differently coordinated FeOx in the interfacial region. The approach was applied to Fe25Sc75 nanoglass and revealed Fe–Fe bonding concealed in the Sc-rich matrix. Finally, analysis of a shear band in a deformed Cu/CuZr nanolaminate confirmed Cu enrichment and reduced medium-range order in the shear band

Direct Observation of Quadrupolar Strain Fields forming a Shear Band in Metallic Glasses

For decades, scanning/transmission electron microscopy (S/TEM) techniques have been employed to analyze shear bands in metallic glasses and understand their formation in order to improve the mechanical properties of metallic glasses. However, due to a lack of direct information in reciprocal space, conventional S/TEM cannot characterize the local strain and atomic structure of amorphous materials, which are key to describe the deformation of glasses. For this work, 4-dimensional-STEM (4D-STEM) is applied to map and directly correlate the local strain and the atomic structure at the nanometer scale in deformed metallic glasses. Residual strain fields are observed with quadrupolar symmetry concentrated at dilated Eshelby inclusions. The strain fields percolate in a vortex-like manner building up the shear band. This provides a new understanding of the formation of shear bands in metallic glass