Category: Research Highlights

•In IRG-1, Luo, Xin, Rupert, and their students have discovered Ni activated sintering of MoNbTaW guided by a computed grain boundary “phase” (complexion) diagram. •This collaborative study made the first observation of solid-state activated sintering in a high-entropy alloy. •Grain boundary (GB) wetting was observed above the solidus line, implying subsolidus GB prewetting to promote…Continue Reading 2024 IRG-1: Discovery of Ni Activated Sintering of MoNbTaW Guided by a Computed Grain Boundary “Phase” Diagram

Grain boundaries often transition between different states, which has important implications for material stability as well as key properties such as strength and fracture resistance.  In this study, atomistic computer models were used to study grain boundary transitions in NbMoTaW, a complex concentrated alloy and a promising material for high temperature applications.  A compact equilibrium…Continue Reading 2024 IRG-1: Chemical complexity frustrates grain boundary transitions

•Heat treatment-induced phase transformation enhances the electronic conductivity of grain interior in entropy stabilized oxides (ESOs) by tuning grain defect chemistry, as second phases segregate to the grain boundaries (GBs). •This work demonstrates the potential to selectively grow second phases at GBs and in grains of ESOs with heat treatment, thereby tuning the electrical properties…Continue Reading 2024 IRG-1: Reversible Enhancement of Electronic Conduction caused by Phase Transformation and Interfacial Segregation in an Entropy Stabilized Oxide

Understanding phase stability of CoCrNi alloy is necessary to ensure that no detrimental phases form when held for long period of time during the potential application temperature •A long-term annealing at 450 °C for 350 hrs was employed to explore the phase stability in a severely deformed CoCrNi with high density of GBs to facilitate…Continue Reading 2024 IRG-1: Role of interfaces in phase decomposition in the CoCrNi alloy

§Refractory complex concentrated alloy (RCCA) exploration and development has been enabled by plasma arc melting (PAM) §Sources of interstitial impurities and variations in PAM are not well documented Key Findings: §Established understanding of the driving forces for interstitial impurity absorption §Interstitial impurities in the feedstocks §Residual gases in the PAM environment §Temperatures achieved during PAM…Continue Reading 2024 IRG-1: The sources and control of interstitial impurities during arc melting of refractory complex concentrated alloys

Our previous work revealed that the (Co,Cu,Mg,Ni,Zn)1-xNaxO system exhibits an electrically conductive layered grain boundary phase at high-temperature processing conditions (Figure A). This boundary phase is a P2 type NaxCoO2 layered structure that has not been reported for other promising high entropy oxides and allows for the intercalation of Na+ ions along the grain boundaries. To…Continue Reading 2024 IRG-1: Conductivity enhancement in sodium-doped multi-phase high entropy oxides

Grain boundaries (GB), which can significantly hinder Li-ion transport, are the bottleneck of improving solid electrolytes’ ionic conductivity. The atomic structure and electrostatic characteristics of GBs thus become pivotal areas of study in materials science. In this work, we use computations to study the element segregations at the GB structures of (Li0.375Sr0.4375)(Ta0.375Nb0.375Zr0.125Hf0.125)O3 (LSTNZH). The anti-site energies…Continue Reading 2024 IRG-1: Observation of Grain Boundary Electrostatic Characteristics in Perovskite Solid-State Electrolytes by Four-Dimensional Scanning Transmission Electron Microscopy

By increasing the sintering temperature to 1400 °C, the microstructure and chemical distribution of the HENA is significantly optimized. (Fig.1a-b, d-e) By introducing additive Zr into the HENA (sintered at 1400 °C), the microstructure and the compositional inhomogeneity can be further altered.  (Fig.1b-c, e-f) Statistical microhardness tests show that by increasing the sintering temperature or…Continue Reading 2024 IRG-1: Interplay of chemistry and structure in complex concentrated alloys

To design improved conductive and bio-compatible nanowires,we aim to understand their electronic structure and electron transfer mechanism, focusing on structure-property relationships. Over the last year, these calculations: •Elucidated the relationship between physical and electronic structure in the ACC dimer by combining DFT and machine learning (Fig 1a).1 Such a systematic understanding of structure-property relationship is necessary…Continue Reading 2024 IRG-2: Understanding the Microscopic Mechanisms Associated with Conductivity in Biological System from First-Principles

Certain peptides self-assemble fibers that exhibit long-range charge transport. Thermal fluctuations have been implicated as important in this emergent property.1 We adapted our interpretable machine learning (ML) platform2 to understand how thermal fluctuations in ACC-Hex peptide dimer nuclear structure influences electronic structure and therefore conductivity. •Combined large-scale DFT calculations of 103 peptide dimer snapshots together with ML…Continue Reading 2024 IRG-2: Machine learning-guided investigation of conductivity mechanisms in peptide assemblies