arXiv subjects

Michael P. Short

Publications and source records attributed to Michael P. Short.

14 recordsLinked to original sources

arXiv2026

Anomalous bulk dealloying below the parting limit

Dealloying has been extensively studied both as a corrosion degradation mechanism in structural materials, including those used in nuclear, aerospace, or marine environments, and as a versatile method to fabricate porous materials for catalysts and other functional applications. Classical dealloying theory in aqueous environments predicts a critical reactive-element concentration (parting limit) for continuous selective dissolution at temperatures where bulk diffusion does not dominate; this threshold is commonly reported around 50~60 at.%. Yet recent studies show that molten salt environments can generate extensive bulk dealloying below this threshold. Despite the importance of this anomalous dealloying behavior in many energy systems and electrochemical applications, its fundamental origin remains elusive. Here, we address this critical gap, revealing a grain boundary (GB)-assisted bulk dealloying mechanism. Using three-dimensional (3D) reconstruction of the dealloyed regions correlated with crystallographic and elemental analyses, we directly map the 3D GB-void architecture and reveal that diffusion-induced recrystallization (DIR) generates a high-density GB network, which then promotes molten-salt infiltration and can drive bulk dealloying far-below the conventionally reported parting limit, producing a distinctive morphology reminiscent of discontinuous precipitation (DP). Understanding this dynamic GB-void interplay is crucial for the prediction and control of dealloying in complex electrochemical environments.

cond-mat.mtrl-sci↗

arXiv2026

Permeation behaviour of hydrogen isotopes in molten FLiBe (2LiF-BeF2): Identifying sources of uncertainty and associated measurement challenges

This paper presents results from systematic investigations conducted in the HYPERION facility to quantify permeabilities of hydrogen isotopes in FLiBe over a temperature range of 773K - 973K. To address the knowledge gap resulting from widely scattered transport parameters reported in the earlier studies, HYPERION experiments incorporate specific provisions to probe unsubstantiated assumptions, including a one-dimensional permeation, membrane surface coverage by the salt, and ideal wettability of the salt-metal interface. Suppression of the isotopic transport behaviour for metal-side charging highlights the permeation barrier characteristics of a bubble-laden Ni-FLiBe interface, impacting permeability by up to 77%. This work attempts to resolve this issue via salt-side charging and informs constraints on the permeant charging methodology for future studies. The initial insights from HYPERION experiments call into question the design choices and estimated transport properties in earlier works. This study provides a plausible explanation for the observed scatter in H/D/T transport in FLiBe.

physics.plasm-ph↗

arXiv2026

Accounting for the length-scale dependence of thermal diffusivity in 3C-SiC measured with transient thermal gratings

Pump-probe optical methods like transient grating spectroscopy (TGS) enable rapid, nondestructive thermoelastic property measurements. But, in phonon-dominated ceramics, they can underpredict bulk thermal diffusivity when long mean free path (MFP) phonons do not equilibrate over experimental length scales. We combine in situ TGS with Si4+ ion irradiation of CVD 3C-SiC (300 and 550C, 0.5-1 dpa) and density functional theory informed Boltzmann transport equation solutions to understand the origins of this offset. We show how the discrepancy between laser flash analysis (LFA) and TGS-measured thermal diffusivity varies with grain-boundary density, temperature, and defect concentration. We introduce a dimensionless suppression factor that accounts for this discrepancy and demonstrate its utility by using it to show an agreement between the thermal defect resistance of neutron irradiated 3C-SiC (measured using LFA) and ion irradiated 3C-SiC (measured using TGS). This theory-informed experimental framework enables quantitative, in situ tracking of ion irradiation damage induced thermal transport degradation in ceramics.

cond-mat.mtrl-sci↗

arXiv2026

Rapid Primary Radiation Damage Resistance Assessment of Precipitation-Hardened Cu Alloys

This study establishes a direct correlation between in situ irradiation-induced property changes measured by transient grating spectroscopy (TGS) and the resulting microstructural damage in Cu-Cr-Ta alloys. Thin films fabricated by physical vapor deposition were irradiated with 6.6 MeV Cu +3 ions up to 25 DPA, while TGS continuously monitored the evolution of surface acoustic wave (SAW) frequency and thermal diffusivity. Post-irradiation transmission electron microscopy (TEM) was used to quantify void formation as a metric of accumulated radiation damage. A pronounced decrease in SAW frequency was observed some seconds after the onset of irradiation, and it was found to correlate strongly with the final void density. Vacancy MEB calculations propose that the small decrease in SAW frequency is associated with the low population of mobile vacancies, promoting defect recombination and decreasing void formation. This relationship enables early prediction of relative radiation damage resistance within minutes of irradiation, substantially reducing the time required compared to conventional irradiation and postcharacterization routes, allowing rapid screening of multiple compositions. We were able to test this method with 3 compositions of the Cu-Cr-Ta system. More generally, this in situ approach provides an efficient pathway for accelerating the development of materials for radiation environments.

cond-mat.mtrl-sci↗

arXiv2026

Corrosion Evolution of T91 Steel in Static Lead-Bismuth Eutectic Under an Oxidising Environment

Understanding corrosion in liquid metal-cooled nuclear systems is essential in order be able to control it. While much literature exists detailing corrosion rates and mechanisms of structural materials in liquid metals, much still remains to be discovered in new regimes of temperature, chemistry, and impurity content. We focus on a less-studied set of conditions, specifically to investigate how liquid lead-bismuth eutectic (LBE) corrodes ferritic/martensitic steels under high-temperature oxidizing conditions. We find that the evolution of corrosion is determined by the formation of protection layer on the surface. The area without effective protection layer experiences oxidation along martensite grain boundaries, transitioning from intergranular attack to broader area corrosion as it progresses. The area a stable, coherent oxide scale will slow the corrosion process and then is oxidized along pre-austenite grain boundaries. Both chromium and oxygen diffusion play vital roles in this process. Most surprisingly, a layer of iron enriched body-centred cubic phase forms on the surface of LBE-corroded T91, contradicting previous studies, which reported only oxide-based surface layers.

cond-mat.mtrl-sci↗

arXiv2026

Real-time vacancy concentration evolution revealed via heavy ion irradiation experiments

We show that in situ ion irradiation transient grating spectroscopy (I3TGS) can be used to monitor the real-time evolution of vacancy concentration generated by self-ion radiation damage in Cu-based alloys. Surface acoustic wave (SAW) frequencies are shown, using a combination of theory and experiment, to reveal vacancy concentrations and their kinetics in real-time. These results are shown to agree with corresponding kinetic Monte Carlo simulations at similar temperatures and dose rates. These results suggest the utility of TGS as a non-contact, non-destructive tool for real-time defect monitoring.

cond-mat.mtrl-sci↗

arXiv2026

Detecting the Onset and Progression of Spinodal Decomposition using Transient Grating Spectroscopy

Spinodal decomposition can degrade corrosion resistance and embrittle materials. The ability to quickly, conclusively, and non-destructively detect the onset of spinodal decomposition before catastrophic materials degradation would represent a significant advance in materials testing. We demonstrate that spinodal decomposition can be detected in binary Fe-Cr alloys via modulus stiffening using in situ and ex situ transient grating spectroscopy (TGS). The key mechanistic insight is the non-linearity in elastic moduli as function of Cr content renders a spinodally decomposed Fe-Cr alloy stiffer than an equivalent solid solution for a certain range of initial chromium compositions. We confirm the presence of spinodal decomposition in the 36 at.% chromium alloy using differential scanning calorimetry (DSC), linked to known spinodal decomposition energetics, and show via atomistic simulations that elastic modulus stiffening is expected after spinodal decomposition in the 36 at.% chromium alloy. The results of this study suggest the potential use of TGS as a practical tool for non-destructive evaluation of key materials susceptible to such degradation.

cond-mat.mtrl-sci↗

arXiv2023

Long-Term Research & Design Strategies for Fusion Energy Materials

Fusion energy is at an important inflection point in its development: multiple government agencies and private companies are now planning fusion pilot plants to deliver electricity to the grid in the next decade. However, realizing fusion as a technically and economically viable energy source depends on developing and qualifying materials that can withstand the extreme environment inside a fusion power plant. This Perspective seeks to engage the broader materials science community in this long-term effort. We first outline the principal materials challenges and research opportunities for fusion. Next, we argue that fusion is distinct from other energy applications with respect to materials, not just in the magnitude and complexity of the technical challenges but also in the present level of uncertainty in materials design requirements. To address this, we finally propose a research framework based on an iterative co-evolution of materials science and fusion power plant design requirements.

cond-mat.mtrl-sci↗

arXiv2022

Revealing hidden defects through stored energy measurements of radiation damage

With full knowledge of a material's atomistic structure, it is possible to predict any macroscopic property of interest. In practice, this is hindered by limitations of the chosen characterisation techniques. For example, electron microscopy is unable to detect the smallest and most numerous defects in irradiated materials. Instead of spatial characterisation, we propose to detect and quantify defects through their excess energy. Differential scanning calorimetry (DSC) of irradiated Ti measures defect densities 5 times greater than those determined using transmission electron microscopy (TEM). Our experiments also reveal two energetically-distinct processes where the established annealing model predicts one. Molecular dynamics (MD) simulations discover the defects responsible and inform a new mechanism for the recovery of irradiation-induced defects. The combination of annealing experiments and simulations can reveal defects hidden to other characterisation techniques, and has the potential to uncover new mechanisms behind the evolution of defects in materials.

cond-mat.mtrl-sci↗

arXiv2022

One Dimensional Wormhole Corrosion in Metals

Corrosion is a ubiquitous failure mode of materials in extreme environments. The more localized it is, the more difficult it is to detect and more deleterious its effects. Often, the progression of localized corrosion is accompanied by the evolution of porosity in materials, creating internal void-structures that facilitate the ingress of the external environment into the interior of the material, further accelerating the internal corrosion. Previously, the dominant morphology of such void-structures has been reported to be either three-dimensional (3D) or two-dimensional (2D). Here, we report a more localized form of corrosion, which we call 1D wormhole corrosion. Using electron tomography, we show multiple examples of this 1D and percolating morphology that manifests a significantly high aspect ratio differentiable from 2D and 3D corrosion. To understand the origin of this mechanism in a Ni-Cr alloy corroded by molten salt, we combined energy-filtered four-dimensional scanning transmission electron microscopy (EF-4D-STEM) and ab initio density functional theory (DFT) calculations to develop a vacancy mapping method with nanometer-resolution, identifying a remarkably high vacancy concentration in the diffusion-induced grain boundary migration (DIGM) zone, up to 100 times the equilibrium value at the melting point. These vacancy supersaturation regions act as the precursors of wormholes, and lead to the asymmetrical growth of voids along GBs. We show that similar 1D penetrating corrosion morphologies could also occur in other materials or corrosion conditions, implying the broad impact of this extremely localized corrosion mechanism. Deciphering the origins of 1D corrosion is an important step towards designing structural materials with enhanced corrosion resistance, and also offers new pathways to create ordered-porous materials for functional applications.

cond-mat.mtrl-sci↗

arXiv2021

The dynamic evolution of swelling in nickel concentrated solid solution alloys through in situ property monitoring

Defects and microstructural features spanning the atomic level to the microscale play deterministic roles in the expressed properties of materials. Yet studies of material evolution in response to environmental stimuli most often correlate resulting performance with one dominant microstructural feature only. Here, the dynamic evolution of swelling in a series of Ni-based concentrated solid solution alloys under high-temperature irradiation exposure is observed using continuous, in situ measurements of thermoelastic properties in bulk specimens. Unlike traditional evaluation techniques which account only for volumetric porosity identified using electron microscopy, direct property evaluation provides an integrated response across all defect length scales. In particular, the evolution in elastic properties during swelling is found to depend significantly on the entire size spectrum of defects, from the nano- to meso-scales, some of which are not resolvable in imaging. Observed changes in thermal transport properties depend sensitively on the partitioning of electronic and lattice thermal conductivity. This emerging class of in situ experiments, which directly measure integrated performance in relevant conditions, provides unique insight into material dynamics otherwise unavailable using traditional methods.

cond-mat.mtrl-sci↗

arXiv2021

Measuring Very Low Radiation Doses in PTFE for Nuclear Forensic Enrichment Reconstruction

Every country that has made nuclear weapons has used uranium enrichment. Despite the centrality of this technology to international security, there is still no reliable physical marker of past enrichment that can be used to perform forensic verification of historically produced weapons. We show that the extremely low radioactivity from uranium alpha emissions during enrichment leaves detectable and irreversible calorimetric signatures in the common enrichment gasket material PTFE, allowing for historical reconstruction of past enrichment activities at a sensitivity better than one weapon's quantity of highly enriched uranium. Fast scanning calorimetry also enables the measurement of recrystallization enthalpies of sequentially microtomed slices, confirming the magnitude and the type of radiation exposure while also providing a detection of tampering and a method for analyzing field samples useful for treaty verification. This work opens the door for common items to be turned into precise dosimeters to detect the past presence of radioactivity, nuclear materials, and related activities with high confidence.

physics.ins-det↗

arXiv2020

Non-contact, non-destructive mapping of thermal diffusivity and surface acoustic wave speed using transient grating spectroscopy

We present new developments of the laser-induced transient grating spectroscopy (TGS) technique that enable the measurement of large area 2D maps of thermal diffusivity and surface acoustic wave speed. Additional capabilities include targeted measurements and the ability to accommodate samples with increased surface roughness. These new capabilities are demonstrated by recording large TGS maps of deuterium implanted tungsten, linear friction welded aerospace alloys and high entropy alloys with a range of grain sizes. The results illustrate the ability to view grain microstructure in elastically anisotropic samples, and to detect anomalies in samples, for example due to irradiation and previous measurements. They also point to the possibility of using TGS to quantify grain size at the surface of polycrystalline materials.

physics.app-ph↗

arXiv2019

Transient grating spectroscopy: An ultrarapid, nondestructive materials evaluation technique

Structure-property relationships are the foundation of materials science. Linking microstructure and material properties is essential for predicting material response to driving forces, managing in-service material degradation, and engineering materials for optimal performance. Elastic, thermal, and acoustic properties provide a convenient gateway to directly or indirectly probe material structure across multiple length scales. We review how using the laser-induced transient grating spectroscopy (TGS) technique, which uses a transient diffraction grating to generate surface acoustic waves (SAWs) and temperature gratings on a material surface, non-destructively reveals the material elasticity, thermal diffusivity, and energy dissipation on the sub-microsecond timescale, within a tunable sub-surface depth. This technique has already been applied to many challenging problems in materials characterization, from analysis of radiation damage, to colloidal crystals, to phonon-mediated thermal transport in nanostructured systems, to crystal orientation and lattice parameter determination. Examples of these applications, as well as inferring aspects of microstructural evolution, illustrate the wide potential reach of TGS to solve old materials challenges, and to uncover new science. We conclude by looking ahead at the tremendous potential of TGS for materials discovery and optimization when applied in situ to dynamically evolving systems.

physics.app-ph↗