Multiscale and multimodal
imaging of material structures and properties
provides solid ground on which materials theory and design can flourish.
Recently, KAIST announced 10 flagship research fields, which include
KAIST Materials Revolution: Materials and Molecular Modeling, Imaging,
Informatics and Integration (M3I3). The M3I3 initiative aims to reduce
the time for the discovery, design and development of materials based
on elucidating multiscale processing–structure–property
relationship and materials hierarchy, which are to be quantified and
understood through a combination of machine learning and scientific
insights. In this review, we begin by introducing recent progress
on related initiatives around the globe, such as the Materials Genome
Initiative (U.S.), Materials Informatics (U.S.), the Materials Project
(U.S.), the Open Quantum Materials Database (U.S.), Materials Research
by Information Integration Initiative (Japan), Novel Materials Discovery
(E.U.), the NOMAD repository (E.U.), Materials Scientific Data Sharing
Network (China), Vom Materials Zur Innovation (Germany), and Creative
Materials Discovery (Korea), and discuss the role of multiscale materials
and molecular imaging combined with machine learning in realizing
the vision of M3I3. Specifically, microscopies using photons, electrons,
and physical probes will be revisited with a focus on the multiscale
structural hierarchy, as well as structure–property relationships.
Additionally, data mining from the literature combined with machine
learning will be shown to be more efficient in finding the future
direction of materials structures with improved properties than the
classical approach. Examples of materials for applications in energy
and information will be reviewed and discussed. A case study on the
development of a Ni–Co–Mn cathode materials illustrates
M3I3’s approach to creating libraries of multiscale structure–property–processing
relationships. We end with a future outlook toward recent developments
in the field of M3I3.
Precipitation strengthening has been the basis of physical metallurgy since more than 100 years owing to its excellent strengthening effects. This approach generally employs coherent and nano-sized precipitates, as incoherent precipitates energetically become coarse due to their incompatibility with matrix and provide a negligible strengthening effect or even cause brittleness. Here we propose a shear band-driven dispersion of nano-sized and semicoherent precipitates, which show significant strengthening effects. We add aluminum to a model CoNiV medium-entropy alloy with a face-centered cubic structure to form the L21 Heusler phase with an ordered body-centered cubic structure, as predicted by ab initio calculations. Micro-shear bands act as heterogeneous nucleation sites and generate finely dispersed intragranular precipitates with a semicoherent interface, which leads to a remarkable strength-ductility balance. This work suggests that the structurally dissimilar precipitates, which are generally avoided in conventional alloys, can be a useful design concept in developing high-strength ductile structural materials.
Capping ligands are crucial to synthesizing colloidal nanoparticles with functional properties. However, the synergistic effect between different ligands and their distribution on crystallographic surfaces of nanoparticles during colloidal synthesis is still unclear despite powerful spectroscopic techniques, due to a lack of direct imaging techniques. In this study, atom probe tomography is adopted to investigate the three-dimensional atomic-scale distribution of two of the most common types of these ligands, cetrimonium (C19H42N) and halide (Br and Cl) ions, on Pd nanoparticles. The results, validated using density functional theory, demonstrate that the Br anions adsorbed on the nanoparticle surfaces promote the adsorption of the cetrimonium cations through electrostatic interactions, stabilizing the Pd {111} facets. In contrast, the Cl anions are not strongly adsorbed onto the Pd surfaces. The high density of adsorbed cetrimonium cations for Br anion additions results in the formation of multiple-twinned nanoparticles with superior oxidation resistance.
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