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Water-based anti-corrosion coatings, which are environmentally-friendly replacements for organic solvent-based coatings, do not perform well enough for use in the most challenging corrosion environments. The high water absorption capacity of water-based latex films may reduce barrier performance by contributing to corrosive reactant/product transport. We seek to understand the coupled effects of water absorption and ion transport in hydrated latex films, and to propose mechanisms explaining these effects. Water absorption and ion transport in films immersed in deionized (DI) water were monitored by mass gain and electrical conductivity measurements, respectively. Despite very similar polymer compositions between films, large differences in water absorption and ion transport rates were observed and explained by percolating networks at latex particle boundaries which facilitate transport. A semi-continuum model with three-component diffusion and convection-like elastic relaxation supported the assumptions of the physical mechanisms governing water absorption and ion transport. The evidence of the coupled processes of water absorption and ion transport in hydrated latex films revealed in this study are useful for designing water-based coatings that provide high levels of corrosion resistance.

Data repository for "Multimodal Investigation Into Laser-welded Proton-irradiated Eurofer97", product of the project "The Effect of Radiation on Laser Welds for Fusion Applications".

We developed a modified embedded atom method (MEAM) potential for Fe-Cr-Si ternary systems. These alloys have superior corrosion and crack resistance, making them candidate materials for several engineering applications such as accident-tolerant fuel cladding. We used a multiobjective optimization approach to match Fe-Cr-Si's elastic constants, ground-state energies, and structural parameters with ab initio calculations. The potential has been parameterized by fitting to a set of literature values obtained using density functional theory (DFT) or experimental studies. The developed potential was used in molecular dynamics (MD) simulations to extract mechanical and thermal properties. We obtained the calculated elastic constants for Fe-Cr-Si binary interactions using the proposed potential, agreeing with ab initio calculations. Our calculated self-diffusion coefficient values and defect formation energy using this potential are in good agreement with the previous literature. Therefore, the developed potential can investigate the fundamental behaviors on an atomic scale under harsh conditions like elevated temperature and irradiation. This project is partly supported by DoE-ARPA-E OPEN (DE-AR0001066) and the NSF-CAREER under NSF cooperative agreement CBET-2042683.

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., Comment: main: 17 pages and 6 figures, supplemental: 25 pages and 16 figures

High entropy alloys (HEAs) are potential next-generation structural materials, yet accurate prediction of phase stability remains a challenge. We study two equimolar refractory high entropy alloys, NbMoTaTi–X (X = W, V). Ab initio calculations are performed to determine the vacancy exchange potential in both alloys. Results and experimental confirmation indicate that a zero/low vacancy exchange potential predicts phase instability in NbMoTaTiW, while elemental trends of the same predict segregation in single phase NbMoTaTiV. If these results hold true across other systems, vacancy exchange potential can serve as a rapid predictor of stability in the vast HEA compositional space.

The buildup of corrosion deposits, known as fouling, seriously hinders large-scale energy production. From nuclear power plants to geothermal reservoirs, fouling increases system pressure drops, impedes heat transfer, and accelerates corrosion, leading to derating and early failure. Here, we investigate the collodial interactions between multiple foulants and coated surfaces, with the aim of discovering principles for minimizing the adhesion of foulants to them. We hypothesize that matching the full refractive index spectrum of a coating to its surrounding fluid minimizes the adhesion of all foulants entrained within and that the Lifshitz theory is sufficient to predict which materials will be multi-foulant-resistant. First-principle calculations of Hamaker constants and refractive indices of six foulants on six coatings in water correlate well to direct measurements of adhesion by atomic force microscopy (AFM)-based force spectroscopy. Amorphous 2% fluorine-doped tin oxide, crystalline SiO2, CaF2, and Na3AlF6, which all nearly match the refractive index spectrum of water, successfully resisted adhesion of six diverse foulant materials in aqueous AFM measurements. The validation of this design principle may be expanded to design multi-fouling-resistant coatings for any system in which van der Waals forces are the dominant adhesion mechanism.

Nanostructured materials with amorphous intergranular films (AIFs) have demonstrated superior strength and ductility. Their radiation tolerance is expected to be high as the large fraction of interfacial volume efficiently sinks radiation-induced defects. Here we demonstrate how a crystalline-amorphous system (nanocrystalline Cu with Zr-doped AIFs) responds to continuous irradiation with molecular dynamics simulations. We propose a diffusion model that well characterizes the cascade-driven mixing process, and reveal that the spread of Zr distribution scales linearly with the damage level. The exceptional radiation resistance is attributed to the interfaces acting as sustainable defect sinks, Zr mixing into the bulk to enhance local defect annihilation due to solute-interstitial dragging, and Zr impeding radiation-enhanced grain growth by restraining AIFs from migration and maintaining interface stiffness. These findings suggest that AIF-engineered systems hold promise as highly radiation-tolerant materials with strong structural stability and self-healing capability under radiation damage.

As the potential applications of GaN and Ga2O3 are limited by the inadequacy of conventional doping techniques, specifically when uniform selective area p-type doping is required, the potential for transmutation doping of these materials is analyzed. All transmuted element concentrations are reported as a function of time for several common proton and neutron radiation sources, showing that previously published results considered a small subset of the dopants produced. A 40 MeV proton accelerator is identified as the most effective transmutation doping source considered, with a 2.25 × 1017 protons per cm2 fluence yielding net concentrations of uncompensated p-type dopants of 7.7 × 1015 and 8.1 × 1015 cm−3 for GaN and Ga2O3, respectively. Furthermore, it is shown that high energy proton accelerator spectra are capable of producing dopants required for magnetic and neutron detection applications, although not of the concentrations required for current applications using available irradiation methods.

Liquid lead (Pb)- and lead–bismuth eutectic (LBE)-cooled fast neutron reactors (Gen-IV LFRs) are one of the most technologically mature fission reactor technologies, due to their inherent safety, high power density, and ability to burn nuclear waste. Accelerator-driven systems (ADS), in particular, promise to address the issues of long-lived radiotoxic nuclear waste, emerging uranium ore shortages, and the ever-increasing demand for energy. However, the conditional compatibility of conventional structural materials, such as steels, with liquid Pb and liquid LBE is still an important concern for the deployment of these advanced nuclear reactor systems, making the environmental degradation of candidate structural and fuel cladding steels the main impediment to the construction of Gen-IV LFRs, including ADS. This article presents a comprehensive review of the current understanding of environmental degradation of materials in contact with liquid Pb and liquid LBE, with a focus on the underlying mechanisms and the factors affecting liquid metal corrosion (LMC) and liquid metal embrittlement (LME), which are the two most important materials degradation effects. Moreover, this article addresses the most promising LMC and LME mitigation approaches, which aim to suppress their adverse influence on materials performance. An outlook of the needed future work in this field is also provided.

Multimetallic layered composites (MMLCs) have shown an excellent potential for application under extreme environments, e.g., accident-tolerant fuel cladding, because of their low oxidation tendency and high corrosion resistance. Interfacial phases or complexions in nanocrystalline materials accelerate the annihilation of defects and enhance the radiation resistance of materials, making MMLCs with engineered interlayer phases compelling to deploy in extreme conditions. However, implementation of MMLCs in full capacity remained a challenge due to a lack of fundamental understanding of the underlying mechanisms governing the characteristics of the interface between the metallic layers. The precise role of interlayer phases in MMLCs and their interaction with defects, specifically under extreme conditions, is still unexplored. Pursuing atomistic simulations for various Inconel-Ni MMLCs model materials, we revealed accelerated defect mobility in interlayers with larger crystalline misorientation and the inverse relationship between the interface sink strength to the misorientation angle. Furthermore, we found a linear relation between interlayer misorientation angle with the density of radiation-induced defects and radiation enhanced diffusion. Finally, our results indicate that radiation-induced material degradation is accelerated by the higher defect formation tendency of MMLCs with a high-angle interlayer interface.

Accurate knowledge of molten salt thermophysical properties is crucial to optimize the efficiency, safety, and reliability of molten salt based energy applications. For molten fluorides, currently of high interest for fission and fusion reactors, data regarding these properties are either poor or non-existent. Thermal diffusivity and sound speed in particular play important roles in the modeling of a reactor’s steady state, transient, and accident scenarios. Fluoride salt-compatible property measurement systems have thus far been the bottleneck in accurately obtaining these properties. We present the design of an optical system optimized for molten fluoride salt thermophysical property measurement, along with characterization of its thermal performance. Demonstration of system capabilities is achieved through acquisition of sound speed and thermal diffusivity in lithium chloride (LiCl), showing excellent agreement with literature data.

Background In response to supply shortages caused by the COVID-19 pandemic, N95 filtering facepiece respirators (FFRs or “masks”), which are typically single-use devices in healthcare settings, are routinely being used for prolonged periods and in some cases decontaminated under “reuse” and “extended use” policies. However, the reusability of N95 masks is limited by degradation of fit. Possible substitutes, such as KN95 masks meeting Chinese standards, frequently fail fit testing even when new. The purpose of this study was to develop an inexpensive frame for damaged and poorly fitting masks using readily available materials and 3D printing. Results An iterative design process yielded a mask frame consisting of two 3D printed side pieces, malleable wire links that users press against their face, and cut lengths of elastic material that go around the head to hold the frame and mask in place. Volunteers (n = 45; average BMI = 25.4), underwent qualitative fit testing with and without mask frames wearing one or more of four different brands of FFRs conforming to US N95 or Chinese KN95 standards. Masks passed qualitative fit testing in the absence of a frame at rates varying from 48 to 94 % (depending on mask model). For individuals who underwent testing using respirators with broken or defective straps, 80–100 % (average 85 %) passed fit testing with mask frames. Among individuals who failed fit testing with a KN95, ~ 50 % passed testing by using a frame. Conclusions Our study suggests that mask frames can prolong the lifespan of N95 and KN95 masks by serving as a substitute for broken or defective bands without adversely affecting fit. Use of frames made it possible for ~ 73 % of the test population to achieve a good fit based on qualitative and quantitative testing criteria, approaching the 85–90 % success rate observed for intact N95 masks. Frames therefore represent a simple and inexpensive way of expanding access to PPE and extending their useful life. For clinicians and institutions interested in mask frames, designs and specifications are provided without restriction for use or modification. To ensure adequate performance in clinical settings, fit testing with user-specific masks and PanFab frames is required.

Prediction of material performance in fusion reactor environments relies on computational modelling, and will continue to do so until the first generation of fusion power plants come on line and allow long-term behaviour to be observed. In the meantime, the modelling is supported by experiments that attempt to replicate some aspects of the eventual operational conditions. In 2019, a group of leading experts met under the umbrella of the IEA to discuss the current position and ongoing challenges in modelling of fusion materials and how advanced experimental characterisation is aiding model improvement. This review draws from the discussions held during that workshop. Topics covering modelling of irradiation-induced defect production and fundamental properties, gas behaviour, clustering and segregation, defect evolution and interactions are discussed, as well as new and novel multiscale simulation approaches, and the latest efforts to link modelling to experiments through advanced observation and characterisation techniques. MRG, SLD, and DRM acknowledge funding by the RCUK Energy Programme [grant number EP/T012250/1]. Part of this work has been carried out within the framework of the EUROFusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. JRT acknowledges funding from the US Department of Energy (DOE) through grant DE-SC0017899. ZB, LY,BDW, and SJZ acknowledge funding through the US DOE Fusion Energy Sciences grant DE-SC0006661ZB, LY and BDW also were partially supported from the US DOE Office of Science, Office of Fusion Energy Sciences and Office of Advanced Scientific Computing Research through the Scientific Discovery through Advanced Computing (SciDAC) project on Plasma-Surface Interactions. JMa acknowledges support from the US-DOEs Office of Fusion Energy Sciences (US-DOE), project DE-SC0019157. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the US Department of Energy (DOE) under contract DE-AC05-76RL01830. YO and YZ were supported as part of the Energy Dissipation to Defect Evolution (EDDE), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under contract number DE-AC05-00OR22725. TS and TT are supported by JSPS KAKENHI Grant Number 19K05338.

Ion beams enable accelerated radiation exposure experiments, but traditional destructive post-irradiation examination techniques remain time-consuming. Here, measurements of thermal diffusivity are used to monitor microstructural changes in single crystal niobium irradiated with Si3+ ions up to 1.9 dpa (5.1 × 1015 ions/cm2). Changes in thermal transport are correlated to defect generation and clustering through dose-microstructure relationships. These measurements are made using transient grating spectroscopy (TGS), a multi-modal, non-destructive, rapid characterization technique. This work demonstrates that in this low-dose point defect clustering regime, direct measurements of thermal properties are a powerful tool for understanding irradiation-induced microstructure evolution.

Radiation-induced void swelling is a serious mode of degradation in nuclear structural materials. Much effort has been spent to predict swelling resistance, with the goal of increasing the void swelling incubation dose so as to postpone the consequences of radiation damage. However, this trial-and-error approach is highly inefficient due to the time- and resource-intensive nature of both experiments and physics-based multiscale simulations. In this work, as a first attempt, machine learning is applied to perform this prediction based on available experimental data. Of the multiple techniques applied, the gradient boosting ensemble method best predicts experimental onset doses for swelling in test datasets, and identifies the main contributing factors such as temperature, Fe and Cr content, and dose rate, which are consistent with established understanding. This work demonstrates the feasibility of machine learning to predict macroscale radiation effects based on material and environmental parameters, and has practical significance in guiding further material optimization for nuclear applications.

Mechanical tests of 12Cr18Ni10Ti (AISI 321 analogue: 10 Ni, 0.12 C, 0.5 Ti, 18 Cr, 1 MeV). The plastic instability stress and strain of the necking onset have been estimated. The results of three independent methods are in good agreement. The true local strain at the beginning of the necking process in the 12Cr18Ni10Ti steel has been established to decrease with increasing fluence, whereas the true plastic instability stress remains almost the same.

Atomistic simulations of radiation damage uncover how grain boundaries (GBs) migrate and coalesce under irradiation in bicrystalline Cu. Planar GB migration biased by defect cluster-mediated attraction first leads to slow and steady motion. Subsequently, adjoining GBs coalesce into curved surfaces, where curvature-driven migration with a velocity three orders of magnitude higher than that of a planar boundary dominates motion, triggering rapid grain growth. This study reveals the atomistic mechanisms of radiation-induced grain growth, and has practical implications towards engineering radiation-tolerant nanostructures.

A facility for continuously monitoring the thermal and elastic performance of materials under exposure to ion beam irradiation has been designed and commissioned. By coupling an all-optical, non-contact, non-destructive measurement technique known as transient grating spectroscopy (TGS) to a 6 MV tandem ion accelerator, bulk material properties may be measured at high fidelity as a function of irradiation exposure and temperature. Ion beam energies and optical parameters may be tuned to ensure that only the properties of the ion-implanted surface layer are interrogated. This facility provides complementary capabilities to the set of facilities worldwide which have the ability to study the evolution of microstructure in situ during radiation exposure, but lack the ability to measure bulk-like properties. Here, the measurement physics of TGS, design of the experimental facility, and initial results using both light and heavy ion exposures are described. Finally, several short- and long-term upgrades are discussed which will further increase the capabilities of this diagnostic.

Aside from the historical Molten Salt Reactor Experiment, a few in-reactor loops, and one electron irradiation/corrosion facility, dedicated facilities to test the combined effects of molten salt corrosion and irradiation on materials do not currently exist. A major gap therefore exists in rapid, reactor-relevant materials testing capabilities which, if remedied, would greatly hasten molten salt reactor development. We present a new accelerator-based facility for rapid, simultaneous testing of molten salt-facing materials utilizing a proton beam as the radiation source. Introducing proton irradiation to a molten salt corrosion system poses specific engineering concerns in sample and corrosion cell design, operational stability, integration with the accelerator beamline, and radiation safety. This paper describes how these requirements were fulfilled with confirmatory tests and results.

Accident-tolerant fuel (ATF) cladding with high oxidation resistance during severe accidents is of critical importance to light water reactor safety and sustainability. One newly proposed ATF cladding concept, a multi-metallic layered composite (MMLC), hinges upon the oxidation resistance of an outer Fe-Cr-Si layer on top of a Zr-based alloy, separated by barrier layers to avoid Fe-Zr eutectic formation. The initial oxidation resistance of three potential Fe-Cr-Si alloys was evaluated by exposing them to 1200 °C oxidizing steam for up to one hundred seconds, along with a Zr–Nb–Sn alloy as a reference. The oxidation resistance of Fe12Cr2Si and Fe16Cr2Si was poor, exhibiting a porous, incomplete multilayer oxide composed mainly of mixed Fe/Cr/Si spinels. However, Fe20Cr2Si showed excellent oxidation resistance due to a continuous amorphous SiO2 layer formed at the metal–oxide interface, followed by almost fully dense Cr2O3. This motivates the consideration of Fe-Cr-Si alloys as an additional ATF design choice, similar to FeCrAl alloys in performance and oxidation resistance mechanism.

A phase field model (HOGNOSE) has been developed to address the incomplete understanding of early stage irradiation-enhanced corrosion of Zircaloy-4 in pressurized water reactors (PWRs). HOGNOSE uses an effective charge density to represent space charge in the oxide, which is effectively removed under irradiation by iron doping after secondary phase particle amorphization. Accounting for the temperature and neutron flux dependence on amorphization and showing the large impact of doping on both electron and oxygen transport, HOGNOSE models irradiation-enhanced corrosion up to ten microns over 270–330 °C and prototypical PWR neutron fluxes.

To optimize the efficiency and safety of molten salt-based energy applications, accurate molten salt thermophysical property data are required. For molten fluorides, existing thermal conductivity results have large uncertainties and contradict the current theory by eliciting a positive temperature coefficient. Transient grating spectroscopy (TGS), a technique previously deemed reliable by the theoretical community, has been used to measure the thermal conductivity of fluorides (FLiNaK) for the first time. Results show a fairly flat but slightly increasing thermal conductivity as a function of temperature. The technique has been shown to not suffer from contributions from convection and radiation, an explanation used to discount the results of alternative experimental techniques. In addition to thermal conductivity, sound speed data as a function of temperature have also been obtained for the first time in FLiNaK. The use of accurate sound speed data in theoretical models of thermal conductivity provides better but not complete agreement with the results from TGS. The continued existence of a positive temperature coefficient highlights the need for new mechanistic proposals for why TGS, or current theoretical models, are unable to capture the correct temperature dependence for fluoride molten salt thermal conductivity.

An open-source and full-3D Monte Carlo simulation code, Mat-TRIM, was developed in MATLAB to study the primary knock-on atom (PKA) statistics along nanowires under ion radiation. It is based on TRIM/SRIM’s physics; however, compared to TRIM/SRIM, it enables us to properly handle the 3D geometry of a cylindrical nanowire and a planar source of ions. In this paper, we first discuss the mechanism of Mat-TRIM, followed by some validation examples. Then the distributions of ion density, PKA density, PKA total energy, and PKA average energy in nanowires are explored. Significant differences have been found between the slab and the nanowire simulations. The relative error of a 1D slab and the assumption of a point beam source can be more than 1000% when the nanowire is around 20 nm in diameter. In addition, collisions with electrons is demonstrated to be the dominant mechanism of energy loss in narrow nanowires. Our results reveal that full-3D simulations which correctly treat ion leakage at sample boundaries are necessary to properly simulate PKA production in nano-sized targets.

Tin and antimony are being investigated as potential additives to metallic fuel to control fuel-cladding chemical interaction (FCCI). A primary cause of FCCI is lanthanide fission products moving to the fuel periphery and interacting with the cladding. This interaction can lead to wastage of the cladding and, given enough time or burn-up, eventually to a cladding breach. The current study involves a microstructural characterization of as-cast and annealed U-10Zr-2Sn-2Sb and U-10Zr-2Sn-2Sb-4Ln, where Ln = 53Nd-25Ce-16Pr-6La, all in wt %, as alloys which could prevent FCCI. Scanning electron microscopy (SEM) analysis and X-ray powder diffraction indicates the additive-Zr compound in U-10Zr-2Sn-2Sb is Zr 5 (Sn,Sb) 3 , while the additive-Ln compound being formed in U-10Zr-2Sn-2Sb-4Ln is Ln 5 (Sn,Sb) 4 , with significantly more Sb than Sn (37 at. % versus 6 at. %, respectively). The bulk of the Sn, with a small amount of Sb, remained as Zr 5 (Sn,Sb) 3 precipitates. The potential benefits of a mixed additive system, along with relative stabilities of the intermetallic compounds, are discussed.

Transient grating spectroscopy (TGS), a non-contact ultrasonic materials analysis technique, is proposed to rapidly and indirectly assess relative void swelling resistance of multiple structural materials. Statistically significant changes in the frequency of probed surface acoustic waves (SAWs) suggest that newly developed steels containing nanosized precipitates show higher resistance to void swelling when compared to their simpler, commercial analogues. The higher reduction in SAW frequency seen in the simpler steels, proportional to porosity, indicates more void formation which is directly validated by TEM examinations. This example illustrates the minimum set of targeted TGS studies required to quickly and inexpensively rank materials by relative void swelling resistance, and hence, accelerate materials development and characterization.

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., Comment: 15 pages, 4 figures, 6 supplementary figures; accepted manuscript

After exposure to oxygen-poor (10^-13–10^-14 wt%) liquid lead-bismuth eutectic (LBE) at 500°C for 500 h, LBE penetrates more than one order of magnitude deeper in an FCC Al0.4CoCrFeNi high-entropy alloy (HEA) deco-rated with a network of BCC (Ni, Al)-rich intergranular (IG) precipitates than in a single-phase, FCC Al0.3CoCrFeNi HEA without the IG precipitate network. This deterioration of corrosion resistance is attributed to the energetic nature of the BCC/FCC interphase boundaries (IBs) and resultant IB wetting. The LBE ingress film selectively leaches nickel located at those low-indexed crystalline planes, resulting in phase transformation from FCC to BCC structure. National Natural Science Foundation of China, United States Department of Energy, Office of Nuclear Energy's Nuclear Energy University Program.

The effects of ionizing radiation on materials often reduce to "bad news." Radiation damage usually leads to detrimental effects such as embrittlement, accelerated creep, phase instability, and radiation-altered corrosion. This last point merits special attention. Elucidating synergies between radiation and corrosion has been one of the most challenging tasks impeding the deployment of advanced reactors, stemming from the combined effects of high temperature, corrosive coolants, and intense particle fluxes. Here we report that proton irradiation significantly and repeatably decelerates intergranular corrosion of Ni-Cr alloys in molten fluoride salt at 650C. We demonstrate this effect by showing that the depth of intergranular voids resulting from Cr leaching into the salt is reduced by the proton irradiation alone. Interstitial defects generated from proton irradiation result in radiation-enhanced diffusion, more rapidly replenishing corrosion-injected vacancies with alloy constituents, thus playing the crucial role in decelerating corrosion. Our results show that in industrially-relevant scenarios irradiation can have a positive impact, challenging our view that radiation damage always results in negative effects., Comment: 4 figures plus one supplementary figure, 11 pages in total

The current COVID-19 pandemic has led to a dramatic shortage of masks and other personal protective equipment (PPE) in hospitals around the globe [1]. One component of PPE that is in particular demand are disposable N95 face masks. To alleviate this, many methods of N95 mask sterilization have been studied and proposed with the hope of being able to safely reuse masks [2]. Two major considerations must be made when re-sterilizing masks: (1) the sterilization method effectively kills pathogens, penetrating into the fibers of the mask, and (2) the method does not degrade the operational integrity of the N95 filters.We studied Cobalt-60 (60Co) gamma irradiation as a method of effective sterilization without inducing mask degradation. Significant literature exists supporting the use of gamma radiation as a sterilization method, with viral inactivation of SARS-CoV reported at doses of at most 10 kGy [3], with other studies supporting 5 kGy for many types of viruses [4]. However, concerns have been raised about the radiation damaging the fiber material within the mask, specifically by causing cross-linking of polymers, leading to cracking and degradation during fitting and/or deployment [5, 6].A set of 3M 8210 and 9105 masks were irradiated using MIT’s 60Co irradiator. Three masks of each type received 0 kiloGray (kGy), 10 kGy and 50 kGy of approximately 1.3 MeV gamma radiation from the circular cobalt sources, at a dose rate of 2.2kGy per hour.Following this sterilization procedure, the irradiated masks passed a OSHA Gerson Qualitative Fit Test QLFT 50 (saccharin apparatus) [7] when donned correctly, performed at the Brigham and Women’s Hospital, in a blinded study repeated in triplicate. However, the masks’ filtration of 0.3 µm particles was significantly degraded, even at 10 kGy.These results suggest against gamma, and possibly all ionizing radiation, as a method of disposable N95 sterilization. Even more importantly, they argue against using the qualitative fit test alone to assess mask integrity.

This paper reports a new liquid metal embrittlement (LME) system in which a dual-phase Al0.7CoCrFeNi (equimolar fraction) high-entropy alloy (HEA) is embrittled by lead-bismuth eutectic (LBE) at 350 and 500 °C. At 350 °C, (Ni, Al)-rich BCC phase is embrittled, leading to intragrain cracking within this phase, while the predominant cracking mode changes to BCC/FCC phase boundary decohesion at 500 °C. At both temperatures, cracks are rarely seen in the (Co, Cr, Fe)-rich FCC phase, indicating that this phase is immune to LME. Furthermore, the results suggest a transition from an adsorption-dominated LME mechanism at 350 °C to a phase boundary wetting-dominated LME mechanism at 500 °C.