Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “functionally graded material”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Exact analytical solution of shear-induced flexural vibration of functionally graded piezoelectric beam

The priority of this paper is to obtain the exact analytical solution for free flexural vibration of FGPM beam actuated using the d{sub 15} effect. In piezoelectric actuators, the potential use of d{sub 15} effect has been of particular interest for engineering applications since shear piezoelectric coefficient d15 is much higher than the other piezoelectric coupling constants d{sub 31} and d{sub 33}. The applications of shear actuators are to induce and control the flexural vibrations of beams and plates. In this study, a modified Timoshenko beam theory is used where electric potential is assumed to vary sinusoidaly along the thickness direction. The material properties are assumed to be graded across the thickness in accordance with power law distribution. Hamilton's principle is employed to obtain the equations of motion along with the associated boundary conditions for FGPM beams. Exact analytical solution is derived thus obtained equations of motion. Results for clamped-clamped and clamped-free boundary conditions are presented. The presented result and method shell serve as benchmark for comparing the results obtained from the other approximate methods.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Modeling of Stress and Temperature Effects on Creep of Reduced Activation Ferritic-Martensitic Steel Alloy F82H (Tertiary Creep Modeling of RAFM Steel)

A Bayesian optimization procedure is presented for calibrating a multi-mechanism micromechanical model for creep to experimental data of F82H steel. Reduced activation ferritic martensitic (RAFM) steels based on are the most promising candidates for some fusion reactor structures. Although there are indications that RAFM steel could be viable for fusion applications at temperatures up to 600 °C, the maximum operating temperature will be determined by the creep properties of the structural material and the breeder material compatibility with the structural material. Due to the relative paucity of available creep data on F82H steel compared to other alloys such as Grade 91 steel, micromechanical models are sought for simulating creep based on relevant deformation mechanisms. As a point of departure, this work recalibrates a model form that was previously proposed for Grade 91 steel to match creep curves for F82H steel. Due to the large number of parameters (9) and cost of the nonlinear simulations, an automated approach for tuning the parameters is pursued using a recently developed Bayesian optimization for functional output (BOFO) framework [1]. Incorporating extensions such as batch sequencing and weighted experimental load cases into BOFO, a reasonably small error between experimental and simulated creep curves at two load levels is achieved in a reasonable number of iterations. Validation with an additional creep curve provides confidence in the fitted parameters obtained from the automated calibration procedure to describe the creep behavior of F82H steel at 600 °C. The model is further extended using a temperature dependent scaling law approach to simulate creep response between 550 °C and 650 °C. The efficacy of this extension is compared with the previously used scaling law approach for Grade 91 steel.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Genetic Variants of NPAT-ATM and AURKA are Associated With an Early Adverse Reaction in the Gastrointestinal Tract of Patients With Cervical Cancer Treated With Pelvic Radiation Therapy

Purpose: This study sought to associate polymorphisms in genes related to cell cycle regulation or genome maintenance with radiotherapy (RT)-induced an early adverse reaction (EAR) in patients with cervical cancer. Methods and Materials: This study enrolled 243 cervical cancer patients who were treated with pelvic RT. An early gastrointestinal reaction was graded using the National Cancer Institute Common Toxicity Criteria, version 2. Clinical factors of the enrolled patients were analyzed, and 208 patients were grouped for genetic analysis according to their EAR (Grade {<=}1, n = 150; Grade {>=}2, n = 58). Genomic DNA was genotyped, and association with the risk of EAR for 44 functional single-nucleotide polymorphisms (SNPs) of 19 candidate genes was assessed by single-locus, haplotype, and multilocus analyses. Results: Our analysis revealed two haplotypes to be associated with an increased risk of EAR. The first, comprising rs625120C, rs189037T, rs228589A, and rs183460G, is located between the 5' ends of NPAT and ATM (OR = 1.86; 95% CI, 1.21-2.87), whereas the second is located in the AURKA gene and comprises rs2273535A and rs1047972G (OR = 1.75; 95% CI, 1.10-2.78). A third haplotype, rs2273535T and rs1047972A in AURKA, was associated with a reduced EAR risk (OR = 0.42; 95% CI, 0.20-0.89). The risk of EAR was significantly higher among patients with both risk diplotypes than in those possessing the other diplotypes (OR = 3.24; 95% CI, 1.52-6.92). Conclusions: Individual radiosensitivity of intestine may be determined by haplotypes in the NPAT-ATM and AURKA genes. These variants should be explored in larger association studies in cervical cancer patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Carbon Ion Irradiation of the Rat Spinal Cord: Dependence of the Relative Biological Effectiveness on Linear Energy Transfer

Purpose: To measure the relative biological effectiveness (RBE) of carbon ions in the rat spinal cord as a function of linear energy transfer (LET). Methods and Materials: As an extension of a previous study, the cervical spinal cord of rats was irradiated with single doses of carbon ions at 6 positions of a 6-cm spread-out Bragg peak (16-99 keV/μm). The TD{sub 50} values (dose at 50% complication probability) were determined according to dose-response curves for the development of paresis grade 2 within an observation time of 300 days. The RBEs were calculated using TD{sub 50} for photons of our previous study. Results: Minimum latency time was found to be dose-dependent, but not significantly LET-dependent. The TD{sub 50} values for the onset of paresis grade 2 within 300 days were 19.5 ± 0.4 Gy (16 keV/μm), 18.4 ± 0.4 Gy (21 keV/μm), 17.7 ± 0.3 Gy (36 keV/μm), 16.1 ± 1.2 Gy (45 keV/μm), 14.6 ± 0.5 Gy (66 keV/μm), and 14.8 ± 0.5 Gy (99 keV/μm). The corresponding RBEs increased from 1.26 ± 0.05 (16 keV/μm) up to 1.68 ± 0.08 at 66 keV/μm. Unexpectedly, the RBE at 99 keV/μm was comparable to that at 66 keV/μm. Conclusions: The data suggest a linear relation between RBE and LET at high doses for late effects in the spinal cord. Together with additional data from ongoing fractionated irradiation experiments, these data will provide an extended database to systematically benchmark RBE models for further improvements of carbon ion treatment planning.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Perspectives on Designer Photocathodes for X-ray Free-Electron Lasers: Influencing Emission Properties with Heterostructures and Nanoengineered Electronic States

Here, the development of photoemission electron sources to specifically address the competing andnincreasingly stringent requirements of advanced light sources such as X-ray Free Electron Lasers (XFELs) motivates a comprehensive material-centric approach that integrates predictive compu- tational physics models, advanced nano-synthesis methods, and sophisticated surface science char- acterization with in situ correlated study of photoemission performance and properties. Related efforts in material science are adopting various forms of nanostructure (such as compositionally graded stoichiometry in heterostructured architectures, and quantum features) allowing for tailored electronic structure to control and enhance opto-electronic properties. These methods influence the mechanisms of photoemission (absorption, transport, and emission) but have not, as yet, been systematically considered for use in photocathode applications. Recent results and near-term op- portunities are described to exploit controlled functionality of nanomaterials for photoemission. An overview of the requirements and status is provided.

47 OTHER INSTRUMENTATION↗
NASA NTRS2015

Recent Developments on Autonomous Corrosion Protection Through Encapsulation

This paper concerns recent progress in the development of a multifunctional smart coating, based on microencapsulation, for the autonomous detection and control of corrosion. Microencapsulation has been validated and optimized to incorporate desired corrosion control functionalities, such as early corrosion detection and inhibition, through corrosion-initiated release of corrosion indicators and inhibitors, as well as self-healing agent release triggered by mechanical damage. While proof-of-concept results have been previously reported, more recent research and development efforts have concentrated on improving coating compatibility and synthesis procedure scalability, with a targeted goal of obtaining easily dispersible pigment-grade type microencapsulated materials. The recent progress has resulted in the development of pH-sensitive microparticles as a corrosion-triggered delivery system for corrosion indicators and inhibitors. The synthesis and early corrosion indication results obtained with coating formulations that incorporate these microparticles are reported. The early corrosion indicating results were obtained with color changing and with fluorescent indicators.

Autonomous↗
DOE OSTI2014

Magnetization curves of sintered heavy tungsten alloys for applications in MRI-guided radiotherapy

Purpose: Due to the current interest in MRI-guided radiotherapy, the magnetic properties of the materials commonly used in radiotherapy are becoming increasingly important. In this paper, measurement results for the magnetization (BH) curves of a range of sintered heavy tungsten alloys used in radiation shielding and collimation are presented. Methods: Sintered heavy tungsten alloys typically contain >90 % tungsten and <10 % of a combination of iron, nickel, and copper binders. Samples of eight different grades of sintered heavy tungsten alloys with varying binder content were investigated. Using a superconducting quantum interference detector magnetometer, the induced magnetic momentm was measured for each sample as a function of applied external field H{sub 0} and the BH curve derived. Results: The iron content of the alloys was found to play a dominant role, directly influencing the magnetizationM and thus the nonlinearity of the BH curve. Generally, the saturation magnetization increased with increasing iron content of the alloy. Furthermore, no measurable magnetization was found for all alloys without iron content, despite containing up to 6% of nickel. For two samples from different manufacturers but with identical quoted nominal elemental composition (95% W, 3.5% Ni, 1.5% Fe), a relative difference in the magnetization of 11%–16% was measured. Conclusions: The measured curves show that the magnetic properties of sintered heavy tungsten alloys strongly depend on the iron content, whereas the addition of nickel in the absence of iron led to no measurable effect. Since a difference in the BH curves for two samples with identical quoted nominal composition from different manufacturers was observed, measuring of the BH curve for each individual batch of heavy tungsten alloys is advisable whenever accurate knowledge of the magnetic properties is crucial. The obtained BH curves can be used in FEM simulations to predict the magnetic impact of sintered heavy tungsten alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Manufacturing of Monolithic Electrodes from Low-Cost Renewable Resources

Lignin, a low-cost, biomass derived precursor, was selected as an alternative for carbon based free standing anodes in Li-ion batteries. Industrially scalable melt-spinning and melt-blowing synthesis methods were developed at Oak Ridge National Laboratory that are compatible with industrially viable production. Engineering studies predict that LCFs can be manufactured at $3/lb using these technologies, which compares favorably to $12/lb for battery grade graphite. The physical properties of lignin carbon fibers, specifically the tunable electrochemical and thermal transport, are suitable for energy storage applications as both an active material and current collector. The elimination of inactive components in the slurry-coated electrodes was enabled by LCF processing parameters modifications to produce monolithic mats in which the fibers are electrically interconnected. These mats were several hundreds of micrometers thick, and the fibers functioned as both current collector and active material by virtue of their mixed ionic/electronic conductivities. The LCFs were coated onto copper current collectors with PVDF binder and conductive carbon additive through conventional slurry processing. Galvanostatic cycling of the LCFs against Li revealed reversible capacities greater than 300 mAh/g. The coulombic efficiencies were over 99.8%. The mats were galvanostatically cycled in half cells against Li. Specific capacities as high as 250 mAh/g were achieved approximately 17% lower than the capacities of the same fibers in slurries. However, there were no inactive materials reducing the practical specific capacity of the entire electrode construction. Lithiation and delithiation of the LCFs proceeded with coulombic efficiencies greater than 99.9%, and the capacity retention was greater than 99% over 100 cycles at a rate of 15 mA/g. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

McNutt, Nichiolas William↗
DOE OSTI2015

A prediction of dislocation‐free CdTe/CdS photovoltaic multilayers via nano‐patterning and composition grading

Abstract Defects in multilayered films have long been a performance‐limiting problem for the semiconductor industry. For instance, CdTe/CdS solar cell efficiencies have had significant improvement in the past 15years or more without addressing the problem of high misfit dislocation densities. Overcoming this stagnation requires a fundamental understanding of interfacial defect formation. Herein, we demonstrate a new first principles‐based CdTe bond‐order approach that enables efficient molecular dynamics to approach the fidelity of density functional theory. Stringent quantum‐mechanical verification and experimental validation tests reveal that our new approach provides an accurate prediction of defects that earlier methods cannot. Using this new capability, we show that misfit dislocations in CdTe/CdS multilayers can be significantly reduced via nano‐patterning and composition grading and more importantly, dislocation‐free multilayers naturally arise when the pattern dimension is reduced below 90nm. Our predictive methods are generally applicable to other materials, highlighting a rational approach towards low‐defect semiconductor films. Copyright © 2015 John Wiley & Sons, Ltd.

Zhou, Xiao Wang↗
DOE OSTI2016

Methodology for Estimating Thermal and Neutron Embrittlement of Cast Austenitic Stainless Steels During Service in Light Water Reactors

Cast austenitic stainless steel (CASS) materials, which have a duplex structure consisting of austenite and ferrite phases, are susceptible to thermal embrittlement during reactor service. In addition, the prolonged exposure of these materials, which are used in reactor core internals, to neutron irradiation changes their microstructure and microchemistry, and these changes degrade their fracture properties even further. This paper presents a revision of the procedure and correlations presented in NUREG/CR-4513, Rev. 1 (Aug. 1994) for predicting the change in fracture toughness and tensile properties of CASS components due to thermal aging during service in light water reactors (LWRs) at 280–330 °C (535–625 °F). The methodology is applicable to CF-3, CF-3M, CF-8, and CF-8M materials with a ferrite content of up to 40%. The fracture toughness, tensile strength, and Charpy-impact energy of aged CASS materials are estimated from known material information. Embrittlement is characterized in terms of room-temperature (RT) Charpy-impact energy. The extent or degree of thermal embrittlement at “saturation” (i.e., the minimum impact energy that can be achieved for a material after long-term aging) is determined from the chemical composition of the material. Charpy-impact energy as a function of the time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which are also determined from the chemical composition. The fracture toughness J-R curve for the aged material is then obtained by correlating RT Charpy-impact energy with fracture toughness parameters. A common “predicted lower-bound” J-R curve for CASS materials of unknown chemical composition is also defined for a given grade of material, range of ferrite content, and temperature. In addition, guidance is provided for evaluating the combined effects of thermal and neutron embrittlement of CASS materials used in the reactor core internal components. The correlations for estimating the change in tensile strength, including the Ramberg/Osgood parameters for strain hardening, are also described.

Chopra, O. K.↗
NASA NTRS2003

Educator Resource Center for NASA Langley Research Center

The goal of the ERCN is to provide expertise and facilities to help educators access and utilize science, mathematics, and technology instructional products aligned with national standards and appropriate state frameworks and based on NASA s unique mission and results. The NASA Langley s Office of Education has established the service area for this ERC to be the five states of Kentucky, North Carolina, South Carolina, Virginia and West Virginia. This educational grant activity is associated with NASA s Mission to inspire the next generation of explorers.. .as only NASA can. The communication of NASA s knowledge is the prime role of this ERC. Functioning as a dissemination system of instructional materials and support for pre-college education programs we have met the NASA Education ERCN Program's goal. The following ERCN objectives have been accomplished: Demonstrate and facilitate the use of NASA educational products and technologies in print, video and web based formats. Examples include but are not limited to NASA approved Educator s Guides with Activities based on national standards for appropriate subjects and grade levels. We have demonstrated the use videotape series in analogue format and the new digital video instructional systems along with the use of NASA TV. The promotion of web page based resources such as the new NASA Portal web and the ability to download print resources is continuously facilitated in workshops. This objective has been completed by educator contacts that include on-site visits, phone requests, postal mail requests, e-mail requests, fax requests and workshops offered.

Bridgford, Todd↗
DOE OSTI2017

Design, Fabrication, and Characterization of Graded Transition Joints

Dissimilar welds between austenitic and ferritic steels suffer from premature failure driven by interfacial stresses and material degradation, brought about by mismatch in the co-efficient of thermal expansion and carbon migration from ferritic steels to the interface, respectively. Tri-metallic transition joints using graded composition between ferritic and austenitic alloys are considered as a viable pathway to address this issue. However, hot cracking may occur during welding nickel alloys to stainless steel. This research attempts to reduce the hot cracking susceptibility of Inconel-82 alloys by functionally grading them with 316L. Optical and Electron microscopy showed extensive cracking in the graded regions. Calculations using Scheil-Gulliver techniques attributed the cracking to the expansion in the solidification range of Inconel-82. To circumvent solidification cracking another transition joint between SA 508 Gr 22 and SS-316L has been designed and fabricated with co-axial powder blown additive manufacturing using a SS 410-SS 316L grading. After fabrication, the joint was characterized using optical and scanning electron microscopy, wavelength dispersive spectroscopy, and electron back scattered and x-ray diffraction techniques. Characterization showed a successful transition joint with minor porosity. The measured composition gradients agree with the designed composition gradients. This study shows that 12-Cr steels could potentially be used to fabricate transition joints without any hot cracking.

42 ENGINEERING↗
DOE OSTI2011

Dose-Volume Analysis of Radiation Nephropathy in Children: Preliminary Report of the Risk Consortium

Purpose: To characterize kidney function in children and adolescents who had undergone radiation treatment that included parts of the kidney. Methods and Materials: Patients receiving radiotherapy during childhood or adolescence were prospectively registered in Germany's Registry for the Evaluation of Side Effects after Radiation in Childhood and Adolescence (RiSK). Detailed information was recorded regarding radiation doses at the organs at risk since 2001 all over Germany. Toxicity evaluation was performed according to standardized Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria. Results: Up to May 2009, 1086 patients from 62 centers were recruited, including 126 patients (median age, 10.2 years) who underwent radiotherapy to parts of the kidneys. Maximal late toxicity (median follow-up 28.5 months in 74 patients) was characterized as Grade 0 (n = 65), 1 (n = 7) or 2 (n = 2). All patients with late effects had received potentially nephrotoxic chemotherapy. A statistically significant difference between patients with and without Grade 1 toxicity, revealing higher exposed kidney volumes in patients with toxicity, was seen for the kidney volume exposed to 20 Gy (V20; p = 0.031) and 30 Gy (V30; p = 0.003). Conclusions: Preliminary data indicate that radiation-induced kidney function impairment is rare in current pediatric multimodal treatment approaches. In the future, RiSK will be able to provide further detailed data regarding dose-volume effect relationships of radiation-associated side effects in pediatric oncology patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2025

Thick graded interfaces increase wear resistance in Ti/TiN nanolayered thin films

Multilayered composites with nanoscale layer thickness incorporating titanium and titanium nitride (Ti/TiN) are used as a model system to study the effects of heterophase interface structure on elastic and plastic deformation, as well as wear behavior. Here, in this work, hardness, modulus, and wear rate under dry reciprocating sliding contact are quantified as a function of Ti-TiN heterophase interfacial nitrogen gradient thickness for Ti/TiN multilayers with 10–80 nm layer thickness. Hardness and modulus are found to be inversely proportional to layer thickness and independent of interface gradient for most specimens. Wear rate is found to be inversely proportional to interface gradient thickness at constant layer thickness, demonstrating that control of nanoscale interface structure is a valid approach to enhancing wear behavior. The materials studied in this work wear comparably or slower than other Ti- and TiN-based composites in the literature, providing a promising avenue for engineering wear-resistant materials for use in industrially relevant applications.

Graded interfaces↗
DOE OSTI2018

Lipophilic Polymethacrylate Ionic Liquids as Lubricant Additives

Despite the growing research field of polymeric ionic liquids used as materials for electrolytes and energy materials, catalysts, separation aides, and carbon materials, reports of lipophilic polymeric ionic liquids for lubricants are essentially nonexistent. Oil-miscible single molecule ionic liquids (ILs) are reported to perform well as neat lubricants and as additives in lubricating base oils. Here in this work, methacrylate type ionic liquid monomers containing ammonium or imidazolium cations and two different counter-anions were synthesized and used as comonomers to obtain functional poly(alkyl methacrylates) (PAMAs) as viscosity index improvers (VII) additives for lubricants. The structure of the IL, including the cation, the anion, and the spacer’s length separating the IL from the methacrylate group, plays an important role in the resulting polymer solubility in PAO (poly-alpha olefin), solution rheology, friction, and wear behavior. Depending on the IL structure, VIIs containing up to 20 % mol IL are soluble in PAO (grade 4), and demonstrate frictionandwear reduction, compared to a conventional oil-soluble PAMA. Notably, wear volume reduction of up to 80 % compared to the oil-soluble control poly(dodecyl methacrylate) is observed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Overview of advanced plasma-facing materials testing for Fusion Pilot Plants at DIII-D

Characterization and testing of advanced plasma-facing materials (PFMs) for Fusion Pilot Plants (FPP) is being conducted at the DIII-D National Fusion Facility through the ongoing two-year FPP Candidate Materials Thrust. Year one tested 17 novel materials utilizing the Divertor Materials Evaluation System (DiMES), with samples analyzed pre- and post-experiment via SEM, EDS, and confocal microscopy. Repeatable reference discharges were developed to ensure uniformity between experiments, including a new strike-point rastering scenario to provide more uniform heat/particle flux across DiMES during ELMing H-mode discharges. Various sample geometries and temperatures were used to achieve FPP-relevant conditions, including samples angled 10° towards the incident plasma flux and pre-heating up to 500 °C. The first exposure of liquid lithium (Li) capillary porous structures in a tokamak demonstrated uniform emission of Li vapor and suppression of Li droplets in H-mode when preheated to 350 °C. Dispersoid-strengthened W with 1 wt% TaC, TiC, and ZrC exposed to H-mode showed cracking and dispersoid ejection for all varieties except TiC, providing a clear down-selection. Ultra-high temperature ceramic materials TiB 2 and ZrB 2 showed minimal degradation under L-mode exposure. Silicon carbide (SiC) fiber composites showed arcing along edges, while CVD SiC remained pristine. Atmospheric plasma-sprayed W and SiC coatings endured H-mode exposure without macroscopic delamination; SiC exhibited granular ejection, while W showed increased outgassing. Additional W-based alloys were stress tested in H-mode, including Ni-based W heavy alloys, W f SiC f /W composites, W multi-principle element alloys, and functionally-graded W/SiC, to varying degrees of success.

DIII-D↗
DOE OSTI2023

SEMI-EMPIRICAL MODELING OF IRRADIATION-INDUCED DIMENSIONAL CHANGE IN H-451 NUCLEAR GRAPHITE

Nuclear graphite has been used as a moderator material in nuclear reactor designs dating back to the first reactor to reach criticality, Chicago Pile 1, in 1942. In addition, it is anticipated to be used in the conceptual Generation four (GenIV) Molten-salt reactors (MSRs) and the High-temperature gas-cooled reactors (HTRs). The macroscopic dimensional change observed in irradiated nuclear graphite is a property change of significant importance. Largely, volumetric change provides valuable insight into the in-service lifetime of graphite components used in nuclear reactors. The dimensional change behavior varies amongst each grade of nuclear graphite due to processing techniques and the resulting microstructure. In this work, historic data for nuclear graphite H-451 is revisited. A semi-empirical methodology is proposed to describe the dimensional change behavior as a function of temperature for nuclear graphite H-451. The turnaround dose, or when there is a reversal of the dimensional change from contraction to expansion, is proposed to be a thermally activated process and thus can be described by an Arrhenius model. On the atomic scale, H-451 is sp2-bonded carbon atoms with some degree of disorder regardless of orientation. Towards that end, the activation energy is assumed to be a constant irrespective of orientation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Antimicrobial properties of a multi-component alloy

High traffic touch surfaces such as doorknobs, countertops, and handrails can be transmission points for the spread of pathogens, emphasizing the need to develop materials that actively self-sanitize. Metals are frequently used for these surfaces due to their durability, but many metals also possess antimicrobial properties which function through a variety of mechanisms. This work investigates metallic alloys comprised of several metals which individually possess antimicrobial properties, with the target of achieving broad-spectrum, rapid sanitation through synergistic activity. An entropy-motivated stabilization paradigm is proposed to prepare scalable alloys of copper, silver, nickel and cobalt. Using combinatorial sputtering, thin-film alloys were prepared on 100 mm wafers with ≈50% compositional grading of each element across the wafer. The films were then annealed and investigated for alloy stability. Antimicrobial activity testing was performed on both the as-grown alloys and the annealed films using four microorganisms—Phi6, MS2, Bacillus subtilis and Escherichia coli —as surrogates for human viral and bacterial pathogens. Testing showed that after 30 s of contact with some of the test alloys, Phi6, an enveloped, single-stranded RNA bacteriophage that serves as a SARS-CoV-2 surrogate, was reduced up to 6.9 orders of magnitude (> 99.9999%). Additionally, the non-enveloped, double-stranded DNA bacteriophage MS2, and the Gram-negative E. coli and Gram-positive B. subtilis bacterial strains showed a 5.0, 6.4, and 5.7 log reduction in activity after 30, 20 and 10 min, respectively. Antimicrobial activity in the alloy samples showed a strong dependence on the composition, with the log reduction scaling directly with the Cu content. Concentration of Cu by phase separation after annealing improved activity in some of the samples. The results motivate a variety of themes which can be leveraged to design ideal antimicrobial surfaces.

36 MATERIALS SCIENCE↗