Scholarly Works, Materials Science and Engineering (MSE)

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Perspective on descriptors of mechanical behaviour of cubic transition-metal carbides and nitrides
Kindlund, Hanna; Ciobanu, Theodora; Kodambaka, Suneel; Ciobanu, Cristian V. (Taylor & Francis, 2024-05-31)
Cubic rocksalt structured transition-metal carbides, nitrides (TMC/Ns), and related alloys, are attractive for a wide variety of applications, notably as hard, wear-resistant materials. To-date, valence electron concentration (VEC) is used as a good indicator of stability and mechanical properties of these refractory compounds. In this perspective, we argue for the need of electronic descriptors beyond VEC to explain and predict the mechanical behaviour of the cubic TMC/Ns. As such, we point out that descriptors that highlight differences between constituents, along with semi-empirical models of mechanical properties, have been underused. Additionally, it appears promising to partition VEC into contribution to ionic, covalent, and metallic bonds and we suggest that such partition could provide more insights into predicting mechanical properties in the future.
Differential thermal analysis of the crystallization kinetics in perlite-based nanocrystalline glass-ceramics
Grigoryan, Lyova; Petrosyan, Petik; Asryan, Levon V.; Knyazyan, Nikolay; Petrosyan, Stepan (Institute of Rock Structure and Mechanics, AS CR, 2024-09-01)
A glass-ceramic material containing nanosized crystallites is synthesized based on the natural volcanic material perlite. Using the differential thermal analysis (DTA) method, the effect of Na2SiF6 (a crystallization catalyst from the fluoride group) on the glass crystallization properties is studied. The characteristic glass-transition temperature Tg, peak crystallization temperature Tp, as well as the crystallization activation energy (Ec) and Avrami index (n) are determined in terms of the catalyst content in the initial composition. A decrease in the nucleation agent content is shown to increase Tg, Tp, and Ec. The effect of the crystallization catalyst content on the crystallization mechanism and glass mechanical properties is discussed.
Lasers with double asymmetric barrier layers: Direct versus indirect capture of carriers into the lasing ground state in quantum dots
Hammack, Cody; Asryan, Levon V. (Wiley, 2024-12-19)
Static and dynamic characteristics of a quantum dot (QD) laser with double asymmetric barrier layers – an advanced type of semiconductor laser – are studied. Both direct and indirect capture of carriers into the lasing ground state in QDs is considered. The intradot relaxation of carriers, which controls the laser characteristics in the case of only indirect capture, is shown to not be a significant factor in the case of both direct and indirect capture. In the latter case, both the output optical power and modulation bandwidth are considerably increased.
Reversible Ferroelectric Polarization Modulation of Chiral Molecular Ferroelectrics by Circularly Polarized Light
Wang, Zhongxuan; Wang, Qian; Quan, Lina; Ren, Shenqiang (Wiley, 2025-01-21)
The optical modulation of ferroelectric polarization constitutes a transformative, non-contact strategy for the precise manipulation of ferroelectric properties, heralding advancements in optically stimulated ferroelectric devices. Despite its potential, progress in this domain is constrained by material limitations and the intricate nature of the underlying mechanisms. Recent studies have achieved efficient regulation of ferroelectric polarization and thermal conductivity in chiral ferroelectric thin films through the application of left- and right-handed circularly polarized light (LCP and RCP). Differential absorption of circularly polarized light (CPL) induces nonequilibrium carrier dynamics, generating distinctive interfacial electrostatic fields that enable precise control of ultrathin ferroelectric films. For (R)-BINOL−DIPASi and (S)-BINOL−DIPASi (C26H26O2Si), polarization changes surpass 23%, exhibiting opposite response under LCP and RCP excitation. In R chiral films, remnant polarization decreases from 1.05 µC cm−2 under LCP to 0.85 µC cm−2 under RCP, whereas in S chiral films, polarization increases from 0.85 µC cm−2 under LCP to 0.98 µC cm−2 under RCP. This reversible modulation facilitates reliable switching between ON and OFF states, presenting the potential of chiral ferroelectric materials for flexible, high-speed integrated photonic sensor technologies.
Magnet-in-ferroelectric crystals exhibiting photomultiferroicity
Wang, Zhongxuan; Wang, Qian; Gong, Weiyi; Chen, Amy; Islam, Abdullah; Quan, Lina; Woehl, Taylor J.; Yan, Qimin; Ren, Shenqiang (National Academy of Sciences, 2024-04-16)
Growing crystallographically incommensurate and dissimilar organic materials is fundamentally intriguing but challenging for the prominent cross-correlation phenomenon enabling unique magnetic, electronic, and optical functionalities. Here, we report the growth of molecular layered magnet-in-ferroelectric crystals, demonstrating photo-manipulation of interfacial ferroic coupling. The heterocrystals exhibit striking photomagnetization and magnetoelectricity, resulting in photomultiferroic coupling and complete change of their color while inheriting ferroelectricity and magnetism from the parent phases. Under a light illumination, ferromagnetic resonance shifts of 910 Oe are observed in heterocrystals while showing a magnetization change of 0.015 emu/g. In addition, a noticeable magnetization change (8% of magnetization at a 1,000 Oe external field) in the vicinity of ferro-to-paraelectric transition is observed. The mechanistic electric-field-dependent studies suggest the photoinduced ferroelectric field effect responsible for the tailoring of photo-piezo-magnetism. The crystallographic analyses further evidence the lattice coupling of a magnet-in-ferroelectric heterocrystal system.
Large exchange-driven intrinsic circular dichroism of a chiral 2D hybrid perovskite
Li, Shunran; Xu, Xian; Kocoj, Conrad A.; Zhou, Chenyu; Li, Yanyan; Chen, Du; Bennett, Joseph A.; Liu, Sunhao; Quan, Lina; Sarker, Suchismita; Liu, Mingzhao; Qiu, Diana Y.; Guo, Peijun (Nature Portfolio, 2024-03-22)
In two-dimensional chiral metal-halide perovskites, chiral organic spacers endow structural and optical chirality to the metal-halide sublattice, enabling exquisite control of light, charge, and electron spin. The chiroptical properties of metal-halide perovskites have been measured by transmissive circular dichroism spectroscopy, which necessitates thin-film samples. Here, by developing a reflection-based approach, we characterize the intrinsic, circular polarization-dependent complex refractive index for a prototypical two-dimensional chiral lead-bromide perovskite and report large circular dichroism for single crystals. Comparison with ab initio theory reveals the large circular dichroism arises from the inorganic sublattice rather than the chiral ligand and is an excitonic phenomenon driven by electron-hole exchange interactions, which breaks the degeneracy of transitions between Rashba-Dresselhaus-split bands, resulting in a Cotton effect. Our study suggests that previous data for spin-coated films largely underestimate the optical chirality and provides quantitative insights into the intrinsic optical properties of chiral perovskites for chiroptical and spintronic applications.
Acoustic Sensing Fiber Coupled with Highly Magnetostrictive Ribbon for Small-Scale Magnetic-Field Detection
Dejneka, Zach; Homa, Daniel; Theis, Logan; Wang, Anbo; Pickrell, Gary (MDPI, 2025-01-30)
Fiber-optic sensing has shown promising development for use in detecting magnetic fields for downhole and biomedical applications. Coupling existing fiber-based strain sensors with highly magnetostrictive materials allows for a new method of magnetic characterization capable of distributed and high-sensitivity field measurements. This study investigates the strain response of the highly magnetostrictive alloys Metglas^® 2605SC and Vitrovac^® 7600 T70 using Fiber Bragg Grating (FBG) acoustic sensors and an applied AC magnetic field. Sentek Instrument’s picoDAS interrogated the distributed FBG sensors set atop a ribbon of magnetostrictive material, and the corresponding strain response transferred to the fiber was analyzed. Using the Vitrovac^® ribbon, a minimal detectable field amplitude of 60 nT was achieved. Using Metglas^®, an even better sensitivity was demonstrated, where detected field amplitudes as low as 3 nT were measured via the strain response imparted to the FBG sensor. Distributed FBG sensors are readily available commercially, easily integrated into existing interrogation systems, and require no bonding to the magnetostrictive material for field detection. The simple sensor configuration with nanotesla-level sensitivity lends itself as a promising means of magnetic characterization and demonstrates the potential of fiber-optic acoustic sensors for distributed measurements.
Spinel oxide enables high-temperature self-lubrication in superalloys
Zhang, Zhengyu; Hershkovitz, Eitan; An, Qi; Liu, Liping; Wang, Xiaoqing; Deng, Zhifei; Baucom, Garrett; Wang, Wenbo; Zhao, Jing; Xin, Ziming; Moore, Lowell; Yi, Yao; Islam, Md Rezwan Ul; Chen, Xin; Cui, Bai; Li, Ling; Xin, Hongliang; Li, Lin; Kim, Honggyu; Cai, Wenjun (Nature Research, 2024-11-20)
The ability to lubricate and resist wear at temperatures above 600 °C in an oxidative environment remains a significant challenge for metals due to their high-temperature softening, oxidation, and rapid degradation of traditional solid lubricants. Herein, we demonstrate that high-temperature lubricity can be achieved with coefficients of friction (COF) as low as 0.10-0.32 at 600- 900 °C by tailoring surface oxidation in additively-manufactured Inconel superalloy. By integrating high-temperature tribological testing, advanced materials characterization, and computations, we show that the formation of spinel-based oxide layers on superalloy promotes sustained self-lubrication due to their lower shear strength and more negative formation and cohesive energy compared to other surface oxides. A reversible phase transformation between the cubic and tetragonal/monoclinic spinel was driven by stress and temperature during high temperature wear. To span Ni- and Cr-based ternary oxide compositional spaces for which little high-temperature COF data exist, we develop a computational design method to predict the lubricity of oxides, incorporating thermodynamics and density functional theory computations. Our finding demonstrates that spinel oxide can exhibit low COF values at temperatures much higher than conventional solid lubricants with 2D layered or Magnéli structures, suggesting a promising design strategy for selflubricating high-temperature alloys.
Heat Treatment Effect on the Corrosion Resistance of 316L Stainless Steel Produced by Laser Powder Bed Fusion
Sangoi, Kevin; Nadimi, Mahdi; Song, Jie; Fu, Yao (MDPI, 2025-01-04)
This study explores the effect of heat treatment on the microstructural characteristics and corrosion resistance of 316L stainless steels (SSs) produced via laser powder bed fusion (L-PBF), focusing on anisotropic corrosion behavior—a relatively less explored phenomenon in LPBF 316L SSs. By systematically analyzing the effects of varying heat treatment temperatures (500 °C, 750 °C, and 1000 °C), this work uncovers critical correlations between microstructural evolution and corrosion properties. The findings include the identification of anisotropic corrosion resistance between horizontal (XY) and vertical (XZ) planes, with the vertical plane demonstrating higher pitting and repassivation potentials but greater post-repassivation current densities. Furthermore, this study highlights reductions in grain size, dislocation density, and melt pool boundaries with increasing heat treatment temperatures, which collectively diminishes corrosion resistance. These insights advance the understanding of processing–structure–property relationships in additively manufactured metals, providing practical guidelines for optimizing thermal post-processing to enhance material performance in corrosive environments.
Optimization of Zn Leaching Recovery from Tire Rubber and High-Purity ZnO Production
Li, Shiyu; Tran, Thien Q.; Ji, Bin; Brand, Alexander S.; Zhang, Wencai (Springer, 2024-12-18)
Waste tire rubber is regarded as a potential source for Zn recovery and recycling. In this study, the occurrence of modes of Zn was first characterized by an electron probe microanalyzer (EPMA), and the result indicated both ZnO and ZnS were present in the tire rubber. The Zn leaching recovery was optimized by response surface methodology, and temperature was identified as the most significant variable. The highest recovery of over 98% was obtained at 90 °C for 400 min when using 2.0 mol/L HNO3 as the lixiviant. After that, the Zn-containing leach liquor was subjected to solvent extraction for further separation and purification using bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) and 2-ethylhexylphosphonic mono-2-ethylhexyl (PC88A) as extractants. Various parameters, such as equilibrium pH, extractant concentration, and organic-to-aqueous (O/A) ratio, were investigated to maximize the Zn extraction while minimizing the contamination of impurities. The result indicated that 0.1 mol/L Cyanex 272 exhibited a higher separation factor for Zn over major impurities compared to PC88A under the same conditions. To produce the high-purity ZnO, the Zn-loaded organic phase was subjected to stripping tests, and over 92% of Zn was stripped out with trace amounts of impurities. Finally, the pH value of the stripped solution was increased to precipitate Zn, and a final ZnO product with a purity of over 99% was obtained. This study provided a reference for waste tire rubber management and utilization.
Stabilizing milk-derived extracellular vesicles (mEVs) through lyophilization: a novel trehalose and tryptophan formulation for maintaining structure and Bioactivity during long-term storage
Dogan, Alan B.; Marsh, Spencer R.; Tschetter, Rachel J.; Beard, Claire E.; Amin, Md R.; Jourdan, L. Jane; Gourdie, Robert G. (2025-01-13)
Extracellular vesicles (EVs) are widely investigated for their implications in cell-cell signaling, immune modulation, disease pathogenesis, cancer, regenerative medicine, and as a potential drug delivery vector. However, maintaining integrity and bioactivity of EVs between Good Manufacturing Practice separation/filtration and end-user application remains a consistent bottleneck towards commercialization. Milk-derived extracellular vesicles (mEVs), separated from bovine milk, could provide a relatively low-cost, scalable platform for large-scale mEV production; however, the reliance on cold supply chain for storage remains a logistical and financial burden for biologics that are unstable at room temperature. Herein, we aim to characterize and engineer a freeze-dried, mEV formulation that can be stored at room temperature without sacrificing structure/bioactivity and can be reconstituted before delivery. In addition to undertaking established mEV assays of structure and function on our preparations, we introduce a novel, efficient, high throughput assay of mEV bioactivity based on Electric Cell Substrate Impedance Sensing (ECIS) in Human dermal fibroblast monolayers. By adding appropriate excipients, such as trehalose and tryptophan, we describe a protective formulation that preserves mEV bioactivity during long-term, room temperature storage. Our identification of the efficacy of tryptophan as a novel additive to mEV lyophilization solutions could represent a significant advancement in stabilizing small extracellular vesicles outside of cold storage conditions.
Chain-length-controllable upcycling of polyolefins to sulfate detergents
Munyaneza, Nuwayo Eric; Ji, Ruiyang; DiMarco, Adrian; Miscall, Joel; Stanley, Lisa; Rorrer, Nicholas; Qiao, Rui; Liu, Guoliang (Springer Nature, 2024-11-18)
Escalating global plastic pollution and the depletion of fossil-based resources underscore the urgent need for innovative end-of-life plastic management strategies in the context of a circular economy. Thermolysis is capable of upcycling end-of-life plastics to intermediate molecules suitable for downstream conversion to eventually high-value chemicals, but tuning the molar mass distribution of the products is challenging. Here we report a temperature-gradient thermolysis strategy for the conversion of polyethylene and polypropylene into hydrocarbons with tunable molar mass distributions. The whole thermolysis process is catalyst- and hydrogen-free. The thermolysis of polyethylene and polyethylene/polypropylene mixtures with tailored temperature gradients generated oil with an average chain length of ~C14. The oil featured a high concentration of synthetically useful α-olefins. Computational fluid dynamics simulations revealed that regulating the reactor wall temperature was the key to tuning the hydrocarbon distributions. Subsequent oxidation of the obtained α-olefins by sulfuric acid and neutralization by potassium hydroxide afforded sulfate detergents with excellent foaming behaviour and emulsifying capacity and low critical micelle concentration. Overall, this work provides a viable approach to producing value-added chemicals from end-of-life plastics, improving the circularity of the anthropogenic carbon cycle.
Ensuring Melt Track Width Consistency and Crack-Free Conditions Using Interpass-Temperature-Dependent Process Parameters for Wire-Arc-Directed Energy-Deposited Inconel 718
Jimenez, Xavier A.; Song, Jie; Fu, Yao; To, Albert C. (MDPI, 2024-06-28)
Melt track width can vary in a wire-arc-directed energy-deposited material (DED) using a constant set of process parameters, leading to a lower-quality build. In this work, a novel framework is proposed that uses the data from the process parameter development stage to create optimized process parameters for a target layer width at different interpass temperatures without hot cracking. Inconel 718 is used as the model material since it is known to suffer from hot cracking during DED processing. In the proposed framework, a process window containing a few sets of process parameters (torch travel speed and wire feed rate) is established for crack-free deposition of Inconel 718, and these parameters are used to create a small database. A linear regression model is then employed to generate interpass-temperature-specific optimized process parameters for a target melt track width. The results demonstrate that the proposed approach can reduce the melt track width variation in the deposited walls from 12% to 3% error on average under different printing conditions. It also demonstrates that interpass temperature (IPT) can be used as a controlled variable and the optimized process parameters as initial values when applying control techniques to the process.
T-DOpE probes reveal sensitivity of hippocampal oscillations to cannabinoids in behaving mice
Kim, Jongwoon; Huang, Hengji; Gilbert, Earl T.; Kaiser C., Arndt; English, Daniel Fine; Jia, Xiaoting (Nature Research, 2024-02-24)
Understanding the neural basis of behavior requires monitoring and manipulating combinations of physiological elements and their interactions in behaving animals. We developed a thermal tapering process enabling fabrication of low-cost, flexible probes combining ultrafine features: dense electrodes, optical waveguides, and microfluidic channels. Furthermore, we developed a semi-automated backend connection allowing scalable assembly. We demonstrate T-DOpE (Tapered Drug delivery, Optical stimulation, and Electrophysiology) probes achieve in single neuron-scale devices (1) highfidelity electrophysiological recording (2) focal drug delivery and (3) optical stimulation. The device tip can beminiaturized (as small as 50 μm) tominimize tissue damage while the ~20 times larger backend allows for industrial-scale connectorization. T-DOpE probes implanted in mouse hippocampus revealed canonical neuronal activity at the level of local field potentials (LFP) and neural spiking. Taking advantage of the triple-functionality of these probes, we monitored LFP while manipulating cannabinoid receptors (CB1R; microfluidic agonist delivery) and CA1 neuronal activity (optogenetics). Focal infusion of CB1R agonist downregulated theta and sharp wave-ripple oscillations (SPWRs). Furthermore, we found that CB1R activation reduces sharp wave-ripples by impairing the innate SPW-R-generating ability of the CA1 circuit.
Understanding the Impact of Fuel on Surfactant Microstructure of Firefighting Foam
Islam, Rezawana; Lattimer, Brian Y. (Springer Link, 2024-05-01)
Aqueous film-forming foam is being phased out due to the environmental impacts of fluorinated surfactants contained in the firefighting foams. To develop an environmentally friendly firefighting foam, it is important to understand the factors controlling the firefighting performance of surfactants. Fuel transport through foam has been considered as a dominant mechanism for foam collapse. Therefore, the impact of fuels (heptane, octane and trimethylbenzene (TMB)) on surfactant microstructure was studied for three different types of surfactants (Capstone, Glucopon, and siloxane) that have applications in firefighting foam. Multiple techniques were used to identify the microstructure and interfacial properties of surfactants with and without exposure to liquid fuel. The ignition time of fuel vapor through foam and solubility of fuel through liquid surfactant solution were measured as well. This work shows fuel solubility has an impact on the surfactant microstructure and interfacial properties. In addition, fuel solubility and vapor pressure affect the ignition time of fuel vapors.
Magnetic Field Sensing via Acoustic Sensing Fiber with Metglas® 2605SC Cladding Wires
Dejneka, Zach; Homa, Daniel; Buontempo, Joshua; Crawford, Gideon; Martin, Eileen; Theis, Logan; Wang, Anbo; Pickrell, Gary R. (MDPI, 2024-04-10)
Magnetic field sensing has the potential to become necessary as a critical tool for long-term subsurface geophysical monitoring. The success of distributed fiber optic sensing for geophysical characterization provides a template for the development of next generation downhole magnetic sensors. In this study, Sentek Instrument’s picoDAS is coupled with a multi-material single mode optical fiber with Metglas^® 2605SC cladding wire inclusions for magnetic field detection. The response of acoustic sensing fibers with one and two Metglas^® 2605SC cladding wires was evaluated upon exposure to lateral AC magnetic fields. An improved response was demonstrated for a sensing fiber with in-cladding wire following thermal magnetic annealing (~400 °C) under a constant static transverse magnetic field (~200 μT). A minimal detectable magnetic field of ~500 nT was confirmed for a sensing fiber with two 10 μm cladding wires. The successful demonstration of a magnetic field sensing fiber with Metglas^® cladding wires fabricated via traditional draw processes sets the stage for distributed measurements and joint inversion as a compliment to distributed fiber optic acoustic sensors.
A Meta-Analysis of the Effect of Moisture Content of Recycled Concrete Aggregate on the Compressive Strength of Concrete
Cho, Sung-Won; Cho, Sung Eun; Brand, Alexander S. (MDPI, 2024-04-22)
To reduce the environmental impact of concrete, recycled aggregates are of significant interest. Recycled concrete aggregate (RCA) presents a significant resource opportunity, although its performance as an aggregate in concrete is variable. This study presents a meta-analysis of the published literature to refine the understanding of how the moisture content of RCA, as well as other parameters, affects the compressive strength of concrete. Seven machine learning models were used to predict the compressive strength of concrete with RCA, including linear regression, support vector regression (SVR), and k-nearest neighbors (KNN) as single models, and decision tree, random forest, XGBoost, and LightGBM as ensemble models. The results of this study demonstrate that ensemble models, particularly the LightGBM model, exhibited superior prediction accuracy compared to single models. The LightGBM model yielded the highest prediction accuracy with R² = 0.94, RMSE = 4.16 MPa, MAE = 3.03 MPa, and Delta RMSE = 1.4 MPa, making it the selected final model. The study, employing feature importance with LightGBM as the final model, identified age, water/cement ratio, and fine RCA aggregate content as key factors influencing compressive strength in concrete with RCA. In an interaction plot analysis using the final model, lowering the water–cement ratio consistently improved compressive strength, especially between 0.3 and 0.4, while increasing the fine RCA ratio decreased compressive strength, particularly in the range of 0.4 to 0.6. Additionally, it was found that maintaining moisture conditions of RCA typically between 0.0 and 0.8 was crucial for maximizing strength, whereas extreme moisture conditions, like fully saturated surface dry (SSD) state, negatively impacted strength.
Noncovalently particle-anchored cytokines with prolonged tumor retention safely elicit potent antitumor immunity
Niu, Liqian; Jang, Eungyo; Chin, Ai Lin; Huo, Ziyu; Wang, Wenbo; Cai, Wenjun; Rong, Tong (American Association for the Advancement of Science, 2024-04-19)
Preclinical studies have shown that immunostimulatory cytokines elicit antitumor immune responses but their clinical use is limited by severe immune-related adverse events upon systemic administration. Here, we report a facile and versatile strategy for noncovalently anchoring potent Fc-fused cytokine molecules to the surface of size-discrete particles decorated with Fc-binding peptide for local administration. Following intratumoral injection, particle-anchored Fc cytokines exhibit size-dependent intratumoral retention. The 1-micrometer particle prolongs intratumoral retention of Fc cytokine for over a week and has minimal systemic exposure, thereby eliciting antitumor immunity while eliminating systemic toxicity caused by circulating cytokines. In addition, the combination of these particle-anchored cytokines with immune checkpoint blockade antibodies safely promotes tumor regression in various syngeneic tumor models and genetically engineered murine tumor models and elicits systemic antitumor immunity against tumor rechallenge. Our formulation strategy renders a safe and tumor-agnostic approach that uncouples cytokines’ immunostimulatory properties from their systemic toxicities for potential clinical application.
Predicting Ion Sequestration in Charged Polymers with the Steepest-Entropy-Ascent Quantum Thermodynamic Framework
McDonald, Jared; von Spakovsky, Michael R.; Reynolds, William T. (MDPI, 2024-03-01)
The steepest-entropy-ascent quantum thermodynamic framework is used to investigate the effectiveness of multi-chain polyethyleneimine-methylenephosphonic acid in sequestering rare-earth ions (Eu³⁺) from aqueous solutions. The framework applies a thermodynamic equation of motion to a discrete energy eigenstructure to model the binding kinetics of europium ions to reactive sites of the polymer chains. The energy eigenstructure is generated using a non-Markovian Monte Carlo model that estimates energy level degeneracies. The equation of motion is used to determine the occupation probability of each energy level, describing the unique path through thermodynamic state space by which the polymer system sequesters rare-earth ions from solution. A second Monte Carlo simulation is conducted to relate the kinetic path in state space to physical descriptors associated with the polymer, including the radius of gyration, tortuosity, and Eu-neighbor distribution functions. These descriptors are used to visualize the evolution of the polymer during the sequestration process. The fraction of sequestered Eu³⁺ ions depends upon the total energy of the system, with lower energy resulting in greater sequestration. The kinetics of the overall sequestration are dependent on the steepest-entropy-ascent principle used by the equation of motion to generate a unique kinetic path from an initial non-equilibrium state.
Microstructures and Corrosion Properties of Wire Arc Additive Manufactured Copper–Nickel Alloys
Song, Jie; Jimenez, Xavier A.; To, Albert C.; Fu, Yao (MDPI, 2024-02-14)
The 70/30 copper–nickel alloy is used mainly in critical parts with more demanding conditions in marine settings. There is a need for innovative methods that offer fast production and cost-effectiveness in order to supplement current copper–nickel alloy manufacturing processes. In this study, we employ wire arc additive manufacturing (WAAM) to fabricate the 70/30 copper–nickel alloy. The as-built microstructure is characterized by columnar grains with prominent dendrites and chemical segregation in the inter-dendritic area. The aspect ratio of the columnar grain increases with increasing travel speed (TS) at the same wire feed speed (WFS). This is in contrast with the equiaxed grain structure, with a more random orientation, of the conventional sample. The sample built with a WFS of 8 m/min, TS of 1000 mm/min, and a track distance of 3.85 mm exhibits superior corrosion properties in the 3.5 wt% NaCl solution when compared with the conventional sample, as evidenced by a higher film resistance and breakdown potential, along with a lower passive current density of the WAAM sample. The corrosion morphology reveals the critical roles played by the nickel element that is unevenly distributed between the dendrite core and inter-dendritic area.

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