The study, published in Frontiers in Electronics, is the culmination of a testing campaign that began in the CANDO project, an effort to implant micro-LEDs in the brain for optogenetic control of neural activity. That application demanded a transparent, biocompatible encapsulant, which ruled out metal cans and pointed toward silicone rubber. But the team, led by first author Ahmad Shah Idil, was pessimistic at the outset. Silicone is famously permeable to water vapor, and the group expected that moisture would reach the chip surface, hydrate the thin protective passivation layers, and cause insulation breakdown within months. Instead, the passivation and the silicone together proved essentially flawless over thousands of days of brutal aging.

The test vehicles were interdigitated comb capacitors fabricated in a standard AMS 0.35 micrometer CMOS process, the same foundry technology used for countless commercial chips. Each comb consisted of 1,450 aluminum fingers just 1 micrometer wide, separated by half-micrometer gaps, covered by 1.6 micrometers of silicon oxide and silicon nitride passivation. Two deliberate design additions were baked into the layout: a perforated metal shield layer in the top metallization above the combs, connected to the substrate, and a double-layer wall of vias forming a reinforced seal ring around the active area. The shield would buy time if the passivation ever dissolved, while the dense via wall was intended to block lateral water penetration and stop cracks propagating from the diced chip edge.

Encapsulation followed a deceptively simple but carefully controlled recipe. Chips were wire-bonded to ceramic adaptors, ultrasonically cleaned, then treated with air plasma for ten minutes to generate a high density of hydroxyl groups on every exposed surface. Within five minutes of plasma activation, the samples were cast in NuSil MED-6015, a platinum-cured, optically clear, two-part medical silicone, degassed in a vacuum centrifuge and cured at 150 degrees Celsius. The plasma step is critical: it creates chemical anchoring sites so the silicone bonds to the chip rather than merely sitting on it. Because liquid water cannot condense in a void-free, well-bonded silicone layer, even a water-vapor-saturated encapsulant prevents the ionic conduction that drives corrosion.

Forty-five samples were then sealed in test tubes of phosphate-buffered saline and loaded into the team’s custom Accelerated Life Testing Apparatus, which monitored every sample by electrochemical impedance spectroscopy. Four batches ran at 47, 67 and 87 degrees Celsius, roughly two to three times physiological temperature, under either a continuous 5-volt DC bias, representing a worst-case always-on implant power supply, or a biphasic plus-minus 5-volt waveform typical of stimulator outputs. Spectra were recorded daily at first, then weekly and finally monthly for up to 1,587 days. A failure was defined as a 10 percent drop in impedance magnitude at the lowest measured frequency, 10 millihertz, where any water bridging the combs would betray itself as a shunt path.

Not one of the 45 samples failed that way. The characteristic signature of an insulation failure, a broad collapse of impedance across the spectrum as the dielectric hydrates, never appeared in any batch. About 84 percent of the samples remained electrically stable for the entire run, and many looked pristine under the microscope, with no corrosion, no delamination and no measurable change in their impedance or phase. Even at 87 degrees Celsius, where degradation accelerated dramatically, the changes were confined to the interconnects and the encapsulant itself, not the protected active area. The authors attribute this to three factors working together: the redundant shield metal, the near-insolubility of modern oxide-nitride passivation, and the exceptional adhesion of plasma-treated MED-6015, which companion work suggests also blocks the reactive oxygen species produced by the body’s foreign-body response.

The failures that did occur tell their own story. Eleven samples developed faults, nearly all of them open circuits at the gold wire bonds on the aluminum bond pads, including two infant failures on day zero and day two that pointed to sub-optimal manual bonding rather than aging. Two samples leaked at the test apparatus bung, and one delaminated at the ceramic adaptor, producing a 1-megaohm leakage path. Visible corrosion appeared on aluminum pads and lead-tin solder joints in a majority of samples, worsening sharply with temperature, yet crucially, corrosion never correlated with electrical degradation. Twenty-one samples showed visual corrosion with perfectly stable impedance, and no sample showed impedance changes without visible corrosion, indicating that pad corrosion precedes any functional decline, if decline comes at all.

Weibull survival analysis of the two DC-biased batches at 67 and 87 degrees yielded characteristic lives of roughly 51.5 and 12.5 years respectively, though the authors caution against naive extrapolation, because the shape parameters below one reflect the scarcity of failures and the Arrhenius acceleration model could not be verified with only two usable temperature points. Most telling were the failure modes that never emerged even in the harshest batch: cracks and shear voids in the silicone, blistering at anodic pads driven by local acidification and oxygen evolution, and yellowing of the rubber appeared only at 87 degrees, suggesting artifacts of the extreme test conditions rather than realistic threats at body temperature.

The team’s conclusions reshape how chip-scale implants should be designed. If the active area is this robust, future failure will likely come from interconnects, so replacing the gold-on-aluminum ball bond, the acknowledged weak point, with gold-bumped pads, aluminum wire, or under-bump metallization stacks becomes the priority. The double wall-of-vias, which apparently prevented any edge-driven water ingress at negligible silicon area cost, should become standard in implant designs. The group deliberately avoided projecting a specific lifetime at 37 degrees Celsius, but the evidence points in one direction: a thoroughly cleaned, plasma-treated chip in well-bonded medical silicone can survive years of hostile soak testing that vastly exceeds anything the body will deliver.

Open questions remain before these findings translate into clinical devices. Phosphate-buffered saline does not replicate the hydrophobic constituents of interstitial fluid, and silicones are known to absorb lipids over long periods, potentially altering their mechanics and adhesion in ways this test could not capture. There is also a practical tension: if validation takes five years, the chip technology tested may already be obsolete, meaning implant designers must pin down which passivation, metallization and layout features actually matter and carry those across process generations. Still, as the longest and most comprehensive study of its kind, and the first to demonstrate a scalable, foundry-compatible route to encapsulated CMOS implants, this work makes a soft, silicone-armored brain chip look less like a lab curiosity and more like the default architecture for the next generation of neurotechnology.

Subject of Research: Long-term accelerated aging of plasma-enhanced silicone-encapsulated CMOS integrated circuits for active implantable neurotechnology

Article Title: On the stability of CMOS ICs with plasma-enhanced silicone encapsulation for active implantable neurotechnology: 4.3 years of accelerated life testing

Article References: Shah Idil, A., Lamont, C., Nanbakhsh, K., Mazza, F., Giagka, V., Constandinou, T. G., Vanhoestenberghe, A., & Donaldson, N. D. N. (2026). On the stability of CMOS ICs with plasma-enhanced silicone encapsulation for active implantable neurotechnology: 4.3 years of accelerated life testing. Frontiers in Electronics, 7, Article 1788559. https://doi.org/10.3389/felec.2026.1788559

Image Credits: AI Generated

DOI: 10.3389/felec.2026.1788559

Keywords: CMOS, silicone encapsulation, implantable devices, neurotechnology, accelerated life testing, PDMS, wire bonds, passivation, biocompatibility, bioelectronics, electrochemical impedance spectroscopy, hermetic packaging

Photoelectrochemical water splitting is the process at the heart of this advance. In such a system, a photoanode absorbs sunlight and uses the resulting energetic charge carriers to tear water molecules apart, releasing hydrogen at a cathode. Quantum dots, nanoscale semiconductor crystals just a few nanometers across, are attractive candidates for the light-absorbing layer because their bandgaps can be tuned by size and composition, and because they absorb light with exceptional strength. Yet the highest-performing quantum dots in the literature have almost invariably depended on cadmium or lead, toxic heavy metals whose regulated status has hindered any realistic path toward large-scale deployment of quantum-dot-based solar fuels.

Eco-friendly alternatives drawn from the I–III–VI semiconductor family, such as copper indium sulfide and copper indium selenide, have emerged as appealing substitutes. Their chemistry, however, is far more complicated than that of binary cadmium chalcogenides. With three cation species and a chalcogenide component to juggle, these multinary crystals are prone to forming native defects, and the most damaging among them are anion vacancies, empty sites where a sulfur or selenium atom should sit. These vacancies act as traps that capture charge carriers before they can contribute to water splitting, degrading both photocurrent and stability. Controlling their formation without sacrificing the environmental advantages of the material has therefore been one of the field’s most stubborn challenges.

The DGIST-led team approached the problem from the composition itself. They synthesized a series of five CuIn(S₁₋ₓSeₓ)₂ quantum dot compositions spanning the full range from pure sulfide to pure selenide, carefully holding particle size and cation stoichiometry constant so that any differences in performance could be attributed to the sulfur-to-selenium ratio alone. Their hypothesis was that a carefully chosen mixed-chalcogenide composition could relieve strain in the crystal lattice and thereby reduce the thermodynamic drive to form anion vacancies. The work, published on September 1, 2026, in the open-access journal eScience (DOI: 10.1016/j.esci.2025.100518), reveals that the optimal point lies precisely at an equimolar balance.

Structural characterization told the story with unusual clarity. Transmission electron microscopy confirmed that all five compositions formed uniform particles of approximately 4.3 nanometers, ruling out size effects. X-ray diffraction showed that the equimolar composition, CuIn(S₀.₅Se₀.₅)₂, exhibited the lowest tetragonal lattice distortion of the series, an indication of minimal crystal strain. Extended X-ray absorption fine structure (EXAFS) analysis added a second layer of evidence: the 1:1 composition displayed higher coordination numbers for both copper and indium bonds, meaning that a larger fraction of the cation sites had their full complement of neighboring chalcogen atoms and fewer vacant anion sites existed in the lattice.

Electron paramagnetic resonance (EPR) spectroscopy provided the most direct confirmation of the defect argument. The technique, which is sensitive to unpaired electrons associated with vacancy defects, showed that the equimolar quantum dots contained the lowest concentrations of both sulfur and selenium vacancies of any composition in the series. The consequence of this cleaner crystal structure was visible in the material’s electronic properties. Time-resolved photoluminescence measurements revealed significantly extended carrier lifetimes, and the hole concentration in the optimized dots nearly doubled compared with the pure sulfide quantum dots. In photoelectrochemical terms, more carriers being generated, surviving longer, and reaching the interface translates directly into more efficient water splitting.

When the team assembled the optimized quantum dots into working devices, the results were striking. The researchers sensitized titanium dioxide (TiO₂) photoanodes with the CuIn(S₀.₅Se₀.₅)₂ quantum dots, protected the assembly with combined zinc sulfide (ZnS) and silicon dioxide (SiO₂) passivation layers, and measured a photocurrent density of 15.1 milliamperes per square centimeter at 0.6 volts versus the reversible hydrogen electrode. That figure stands as a record for heavy-metal-free quantum dot systems, bringing the eco-friendly platform into territory previously dominated by cadmium- and lead-based materials. In the photoelectrochemical cell, photogenerated electrons travel to the cathode for hydrogen evolution while holes are consumed by the electrolyte, and the engineered dots shuttle that charge with unprecedented efficiency for a heavy-metal-free system.

Efficiency alone, however, does not make a practical solar fuel technology, and the second half of the team’s result addresses durability. The dual passivation strategy, layering both ZnS and SiO₂ over the quantum dot sensitizer, proved critical for keeping the device alive under operating conditions. The passivated photoanodes maintained Faradaic efficiency above 80 percent for more than six hours of continuous operation, demonstrating that the catalytic activity of the quantum dots survives prolonged illumination and water exposure. For any photoelectrochemical system contemplating industrial relevance, sustained operational stability is as decisive a metric as peak photocurrent, and the passivation scheme offers a concrete, transferable pathway to achieving it.

The research team emphasized that the most exciting aspect of the study is how a seemingly simple adjustment, balancing sulfur and selenium at the atomic scale, resolves what has long been considered the Achilles’ heel of eco-friendly quantum dots. According to the authors, the approach turns an intrinsic weakness of multinary chemistry into a strength, proving that these materials can perform on par with their toxic counterparts without compromising environmental safety. Beyond the performance benchmark itself, they argued, the work establishes a fundamental design principle for defect engineering in multinary quantum dots, one that could accelerate the transition toward sustainable hydrogen energy technologies by giving materials designers a compositional lever to pull rather than relying on post-synthetic fixes.

The implications reach well beyond hydrogen production. Composition-driven defect control of the kind demonstrated here could benefit quantum-dot solar cells, photodetectors, and light-emitting devices, all of which depend on minimizing trap states to preserve charge transport or emission quality. The ability to achieve high efficiency without cadmium or lead opens the door for large-scale deployment in renewable energy infrastructure, particularly in regions pursuing decentralized hydrogen production systems where ease of manufacturing and environmental safety carry extra weight. The research was supported by the National Research Foundation of Korea, the Ministry of Trade, Industry and Energy, and the Korea Institute for Advancement of Technology. As the solar fuels community continues its search for materials that are simultaneously efficient, stable, and safe, this study suggests that sometimes the answer lies not in inventing new compounds but in finding the precise atomic ratio at which an existing one stops sabotaging itself.

Subject of Research: Defect-engineered CuIn(S1-xSex)2 quantum dots for photoelectrochemical solar hydrogen production

Article Title: Tuning sulfur and selenium mix unlocks record solar hydrogen from eco-friendly quantum dots

Article References: Tuning sulfur and selenium mix unlocks record solar hydrogen from eco-friendly quantum dots. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: quantum dots, solar hydrogen, photoelectrochemical water splitting, anion vacancies, chalcogenide, CuIn(S,Se)2, defect engineering, heavy-metal-free, photocurrent, passivation, DGIST, eScience

The team’s central finding is sobering for anyone hoping the Cantor alloy would shrug off caustic environments indefinitely. Using a battery of electrochemical techniques, the researchers showed that the passive film, the nanometer-thin oxide layer that acts as the alloy’s chemical armor, becomes progressively less stable and less protective as the NaOH concentration rises. In dilute alkaline solutions, the alloy exhibited lower corrosion current densities and lower passive current densities, together with higher interfacial impedance, all classic signatures of a robust, well-behaved barrier layer. As the hydroxide concentration increased, those protective metrics deteriorated in lockstep, indicating that the film thins, dissolves more readily, or conducts charge more easily under the harshest conditions tested. The work was conducted under short-term, room-temperature conditions, an important caveat that frames the results as a controlled electrochemical snapshot rather than a long-term service-life prediction.

Methodologically, the study is a tour of the modern corrosion-science toolkit. Potentiodynamic polarization swept the alloy’s potential to measure how much current it draws as it anodically dissolves or passivates, revealing the width and quality of the passive region. Electrochemical impedance spectroscopy probed the film’s resistance to charge transfer by applying small alternating-voltage perturbations across a range of frequencies, effectively fingerprinting the barrier layer’s electrical character. Cyclic polarization, in which the potential is driven upward and then reversed, was used to assess susceptibility to localized breakdown such as pitting, by looking for hysteresis between the forward and reverse scans. Finally, Mott-Schottky analysis exploited the semiconductor-like behavior of the passive film itself, measuring how its capacitance changes with applied potential to infer the density and type of electronic defects, donors or acceptors, within the oxide. Defect-rich passive films are generally more vulnerable, because point defects provide pathways for aggressive ions and metal dissolution.

Complementing the electrochemistry, the researchers examined the corroded surfaces with scanning electron microscopy and energy-dispersive X-ray spectroscopy. What they found was a spatial correlation that will resonate with anyone who has studied powder-metallurgy materials: localized surface attack clustered around microstructural heterogeneities containing sulfides and oxides that sit along prior particle boundaries, the seams where powder particles fused together during hot isostatic pressing. These boundary regions, enriched in second-phase particles and impurities inherited from the powder feedstock, appear to be the weak links in an otherwise uniform five-element matrix. The authors are careful, however, not to overclaim: their measurements establish an association between attack sites and these heterogeneities, but they do not determine the exact site or sequence in which corrosion initiates. Distinguishing whether the sulfide inclusions dissolve first and undermine the surrounding film, or whether the film breaks first and exposes the inclusions, remains an open question for future work.

That honesty extends to the chemistry of the passive film itself. The study did not directly determine the film’s composition or the valence states of its constituent elements, so the authors confine any discussion of chromium- and manganese-containing surface species to literature-informed interpretation rather than measured fact. This is a meaningful distinction in the high-entropy alloy field, where a long-standing hypothesis holds that preferential oxidation of chromium, the same element that protects stainless steels, enriches the passive film in stable chromium oxides and hydroxides. Manganese, by contrast, has often been cast as the Cantor alloy’s Achilles heel, because manganese oxides tend to be more soluble and less protective, potentially creating defects in the film. The new results are consistent with such a picture, in which film quality degrades under increasingly caustic conditions, but the authors correctly note that confirming the roles of specific elements requires direct surface spectroscopy, such as X-ray photoelectron spectroscopy, which was not part of the present measurements.

Why does alkalinity matter so much? In acidic and neutral environments, the Cantor alloy has frequently been compared, sometimes favorably, to 304 stainless steel, and prior studies have documented its passivation behavior in sulfuric acid and in carbonate-bicarbonate solutions. Strongly alkaline media change the thermodynamic and kinetic rules of the game. Hydroxide ions participate directly in the dissolution equilibria of many transition-metal oxides, and amphoteric oxides such as those of chromium can dissolve as soluble hydroxo complexes at high pH. At the same time, alkaline environments are industrially ubiquitous: caustic brines flow through chlor-alkali plants, pulp and paper mills, alumina refineries, and numerous waste-treatment streams, and concentrated hydroxide electrolytes are central to alkaline water electrolysis and several battery chemistries. A structural or functional alloy that must survive in these settings cannot be evaluated only in seawater or dilute acid, which makes the present concentration-resolved study a practical addition to the literature.

The manufacturing route adds another layer of significance. Hot isostatic pressing, or HIP, consolidates metal powders by simultaneously applying high temperature and inert-gas pressure, producing dense components with near-wrought quality and complex near-net shapes. For high-entropy alloys, whose constituent elements span a wide melting range, HIP offers a route to large, crack-free bodies that are difficult to cast homogeneously. But powder routes carry their own risks: absorbed gases, surface oxides on the powder particles, and trace sulfur contamination can survive consolidation and decorate the prior particle boundaries. The new study’s observation that localized corrosion associates with sulfide- and oxide-bearing heterogeneities along those boundaries is a direct warning that powder cleanliness and consolidation parameters are not merely mechanical concerns. They are corrosion concerns, because a single vulnerable boundary thread can seed pits that compromise an entire component.

The authors are equally candid about the limits of attribution. Because no cast, wrought, or differently consolidated reference material was examined in parallel, the measured corrosion performance cannot be ascribed to hot isostatic pressing itself. This is a point of genuine scientific discipline in a field where processing comparisons are often made across studies with different powder lots, particle sizes, and test protocols. Prior work has shown that fabrication route matters: comparisons between selective laser melting and casting, between spark plasma sintering and other routes, and between annealed and as-built conditions have all revealed measurable shifts in corrosion behavior, often traceable to grain size, residual stress, segregation, and inclusion populations. A rigorous head-to-head comparison of HIP-consolidated Cantor alloy against cast and wrought counterparts in the same NaOH solutions would be the natural next experiment, and the present study lays the electrochemical groundwork for it.

What emerges from the full picture is a nuanced portrait of a famous material under a demanding class of conditions. The hot isostatically pressed CrMnFeCoNi alloy does form a passive film in sodium hydroxide, and in dilute solutions that film performs respectably, with low dissolution currents and high impedance. But the armor is not invincible: it weakens as hydroxide concentration climbs, and it fails locally where sulfide and oxide heterogeneities interrupt the boundary network left over from powder consolidation. The study also connects to a broader design conversation in the field, where strategies such as cathodic modification to enrich chromium in the oxide layer, deliberate control of nonmetallic inclusions, and passivation pretreatments have all been explored as ways to harden the passive film of CoCrFeMnNi-family alloys. For engineers weighing high-entropy alloys against conventional stainless steels and nickel alloys for alkaline service, the message is neither a rejection nor an endorsement, but a map: the alloy’s corrosion fate in caustic media is governed jointly by solution concentration and by the microstructural fingerprints of how it was made. As high-entropy alloys move from laboratory curiosities toward real components in energy and chemical industries, studies of this kind, precise about what was measured and honest about what was not, are exactly the evidence base that responsible deployment will require.

Subject of Research: Electrochemical corrosion and passivation behavior of hot isostatically pressed CrMnFeCoNi high-entropy alloy in sodium hydroxide solutions

Article Title: Corrosion and passivation behavior of hot isostatically pressed CrMnFeCoNi high-entropy alloy in NaOH solutions

Article References: Guo, S., Liu, J., Ju, D., Chen, Z., Yue, C., Ma, H., & Wu, Z. (2026). Corrosion and passivation behavior of hot isostatically pressed CrMnFeCoNi high-entropy alloy in NaOH solutions. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13865-8

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13865-8

Keywords: high-entropy alloys, CrMnFeCoNi, Cantor alloy, corrosion, passivation, sodium hydroxide, hot isostatic pressing, electrochemical impedance spectroscopy, Mott-Schottky analysis, localized corrosion, prior particle boundaries, passive film

The team, led by Lamei Zhang and corresponding author Xiaoyu Cai, used a cold metal transfer WAAM system, a variant of the technique that keeps heat input low and reduces spatter and residual stress. Their feedstock was a 1.2-millimetre nickel-aluminium bronze wire deposited onto a 5-millimetre substrate, building single-pass multilayer walls measuring 200 by 6 by 65 millimetres. The innovation lay in how the titanium was introduced. Rather than pre-alloying the wire, the researchers prepared ethanol solutions containing 50-nanometre titanium powder at concentrations of 0.03, 0.05, and 0.1 weight percent, ultrasonically dispersed them, and brushed the solution onto each layer between deposition passes. Once the ethanol evaporated, the next arc pass remelted the surface, dissolving the nanoparticles directly into the molten pool. This in-situ strategy merges manufacturing and modification into a single integrated process, sidestepping the need for separate post-print heat treatments that have historically been the main tool for homogenising WAAM bronzes.

The results revealed a strikingly non-monotonic relationship between titanium content and grain structure, one that defies the simple intuition that more refinement agent always means finer grains. At 0.03 weight percent titanium, the opposite of refinement occurred: average grain size ballooned to 75.2 micrometres, nearly double the 39.1 micrometres of the unmodified printed alloy, and columnar grains proliferated. The explanation lies in a nucleation threshold. Using classical solidification theory, the team calculated that at this low loading, roughly 65 percent of the titanium particles dissolve in the ferociously hot arc molten pool, dropping the effective nucleation site density below the critical value of about 2 times 10 to the 12 per cubic centimetre. With too few active nucleants and a solute drag force far too weak to impede grain boundary migration, the surviving particles could not arrest growth, and the microstructure coarsened.

At 0.05 and 0.1 weight percent, however, the physics flipped decisively. Enough titanium particles survived the thermal assault to push nucleation density past the threshold, triggering prolific heterogeneous nucleation that shattered the coarse columnar regime. Average grain sizes plummeted to 17.3 and 21.6 micrometres respectively. The team also invoked Zener pinning theory, showing that the calculated limiting grain size of about 20.6 micrometres at 0.05 weight percent, after applying a particle distribution correction, matches the measured 17.3 micrometres remarkably well. Electron backscatter diffraction added another dimension: the strong (100) crystallographic texture of the low-titanium sample, with a pole density peak of 7.13, weakened dramatically to 3.13 and then 2.91 as titanium content rose, signalling grains oriented far more randomly and uniformly through the build.

Crucially, transmission electron microscopy confirmed that the titanium did not create any new phases or disrupt the alloy’s delicate multiphase constitution. The printed bronze retained its characteristic alpha matrix, martensitic beta-prime phase, spherical kappa-II precipitates, lamellar kappa-III precipitates, and coffee-bean-shaped kappa-IV iron-rich particles. Energy-dispersive spectroscopy showed the titanium dissolving predominantly into the alpha matrix at concentrations matching the added amounts, while the lamellar kappa-III phase shrank in axial size as titanium content climbed. This means the modification works through grain refinement, solid-solution strengthening, and dislocation pinning rather than by interfering with the thermodynamics of precipitation, preserving the corrosion advantages inherent to conventional nickel-aluminium bronze chemistry.

The mechanical consequences were substantial. Hardness rose by 6 to 8 percent across all titanium-modified samples, reaching peaks near 195.6 HV0.3 compared with 181.2 HV0.3 for the unmodified deposit, and remained remarkably uniform along the build height because each Vickers indentation samples many grains and phases at once. More importantly, tensile testing in both longitudinal and transverse directions showed that the strength-orienting effects of columnar growth had been tamed. The 0.1 weight percent titanium alloy delivered the best overall package: a longitudinal ultimate tensile strength of 718.2 megapascals, up from 664.2 megapascals in the as-deposited alloy, with a yield strength of 372.5 megapascals and 28 percent elongation. The gap between testing directions narrowed to within experimental error, evidence that mechanical anisotropy, the Achilles heel of printed metals, had been effectively suppressed.

Fractography told a coherent mechanistic story. The 0.03 weight percent sample, cursed with coarse columnar grains and a preferred crack path, failed in a quasi-cleavage brittle mode in the transverse orientation, posting the lowest elongation at 20 percent and a yield strength scatter of plus or minus 33.4 megapascals that betrayed deep microstructural heterogeneity. In contrast, the higher-titanium alloys fractured in a ductile, dimpled fashion even in transverse specimens. Pores and cracks in all samples originated at hard precipitate phases and then extended into the alpha matrix, but the refined and spheroidised precipitate morphology in the 0.1 weight percent alloy improved resistance to crack propagation without altering the fundamental initiation mechanism.

Corrosion performance, arguably the decisive metric for marine service, tracked the microstructural improvements with impressive fidelity. After 21 days of immersion in 3.5 weight percent sodium chloride solution, the 0.1 weight percent titanium alloy showed the lowest corrosion rate at 0.167 grams per square metre per day, with mass loss stabilising near 3 milligrams. Its corrosion product layer thinned to 1.83 micrometres, compared with 2.43 and 2.15 micrometres for the lower-titanium variants, and its corrosion interface was straight and uniform, indicating stable passivation. Electrochemical testing confirmed the trend: corrosion current density fell 15.6 percent to 8.49 microamperes per square centimetre, corrosion potential shifted positively by 4.34 millivolts, and the open-circuit potential stabilised in just 18 seconds, the fastest of any sample, reflecting rapid formation of a dense passive film. X-ray diffraction identified the protective products as aluminium oxide and cuprous oxide, the same chemistry that makes bronze a marine workhorse, but now deployed across a finer, more homogeneous microstructure that lengthens the path corrosive ions must travel.

What makes this study resonate beyond one alloy system is the demonstration that microalloying can break the traditional trade-off in which improving one property degrades another. Previous composition tweaks to nickel-aluminium bronze, whether raising nickel content, adjusting the aluminium-to-nickel ratio, or adding tin or chromium, typically boosted strength at the expense of ductility or corrosion behaviour. Here, the coordinated action of grain refinement, precipitate morphology optimisation, and texture weakening allowed strength, ductility, and corrosion resistance to rise together, a synergy the authors connect to the broader concept of escaping performance trade-offs through multi-microstructural feature cooperation. For naval architects and offshore engineers, the practical message is that a titanium addition of 0.05 to 0.1 weight percent, applied during printing rather than after, offers a low-cost route to printed bronze components that could finally match or exceed their cast and forged ancestors, opening the door to large, complex, corrosion-proof marine hardware built directly at the arc.

Subject of Research: Titanium nanoparticle microalloying of wire-arc additive manufactured nickel-aluminium bronze

Article Title: Effect of low-level Ti microalloying on the microstructure, mechanical properties, and corrosion behaviour of WAAM-processed nickel-aluminium bronze

Article References: Zhang, L., Cai, X., Song, B., Dong, B., Lin, S., & Khoshnaw, F. (2026). Effect of low-level Ti microalloying on the microstructure, mechanical properties, and corrosion behaviour of WAAM-processed nickel-aluminium bronze. Advanced Materials Joining, 1(1), Article 17. https://doi.org/10.1007/s44500-026-00016-x

Image Credits: AI Generated

DOI: 10.1007/s44500-026-00016-x

Keywords: nickel-aluminium bronze, wire arc additive manufacturing, titanium nanoparticles, microalloying, grain refinement, corrosion resistance, mechanical properties, cold metal transfer, heterogeneous nucleation, marine engineering, texture weakening, passivation