The research addresses a waste stream that the study places at approximately 6–8 million tonnes of shrimp and crab shells worldwide each year, with only a small proportion used for animal feed or other applications. The authors describe discarded shells as a resource and environmental concern: degradation on land can consume soil nitrogen and release malodorous gases, while shell deposits offshore can contribute to sediment siltation and disturb benthic habitats. Shrimp shells are composite biomasses containing, typically, 20–30% chitin, 30–50% calcium carbonate and 15–25% structural proteins. Hydroxyl, acetamido and amino groups occur along chitin chains, while the shell’s layered structure can permit solvent penetration but also includes mineral material that may impede infiltration and reaction.

For the experiments, the team used a 4:1 weight ratio of polyethylene glycol 400 to glycerol. PEG 400 has low volatility and suitable viscosity, and the authors say it forms strong hydrogen-bonding interactions with chitin macromolecules. Blending it with glycerol was intended to improve swelling and infiltration of the chitin-rich feedstock. Shells from a nearby processing plant were dried at 105 °C, crushed to 60–80 mesh, dried again and ball-milled at 500 rpm for 30-minute cycles, with each cycle followed by a 60-minute standing period and the sequence repeated eight times. The resulting powder was combined with the liquefying agent in a stirred, refluxed three-necked flask. Sulfuric acid was added after the mixture reached its target temperature, and an ice bath terminated the reaction at the assigned time. Solid residues were vacuum-filtered, repeatedly washed with ethanol and dried at 105 °C to constant weight.

The optimization experiment examined four core process variables: reaction temperature, liquefaction time, liquid-to-solid ratio and catalyst dosage. Following single-factor experiments, the researchers adopted a four-factor, three-level Box–Behnken response-surface design and performed all experiments in triplicate. The design ranged from 160 to 180 °C, from 80 to 140 minutes, from a 12:1 to 16:1 liquid-to-solid ratio and from 6% to 8% catalyst. The response variable was the measured liquefaction rate. The resulting quadratic regression model was highly significant, with an F value of 19.76 and a p-value below 0.0001. It explained 95.18% of the observed variation in liquefaction rate, while the adjusted and predicted coefficients of determination were 0.9037 and 0.7744, respectively.

The model’s lack-of-fit test gave a p-value of 0.4811, which the authors interpreted as no significant lack of fit, and the coefficient of variation was 1.07%. The adequate-precision value was 16.31. Temperature and catalyst dosage were the strongest linear factors in the investigated domain, with p-values below 0.0001 for each. The liquid-to-solid ratio had a smaller but significant linear effect, with a p-value of 0.0076, while reaction time did not have a significant linear effect, with a p-value of 0.3015. All four factors had significant quadratic terms. Response surfaces showed that liquefaction could vary nonlinearly as temperature, time and other settings changed, and the paper states that excessively high or low values of the independent variables could hinder the process.

From the fitted response surface, the model predicted a theoretical optimum of 43.09% at 173.05 °C, a 14.67:1 liquid-to-solid ratio, 7.40% catalyst dosage and 107.90 minutes. The researchers rounded these values for practical control in the laboratory, using 173 °C, a 14:1 ratio, 7% catalyst and 108 minutes. Three parallel validation experiments produced a liquefaction rate of 42.35% ± 0.84%, corresponding to a relative prediction error of approximately 1.72% relative to the model optimum. The close result supports the response model within the tested design space. It does not establish that these settings are optimal for shell material with different composition, particle size, processing history or mineral content, because the experiments used shells collected from one nearby processing plant.

The kinetic experiments used the 14:1 liquid-to-solid ratio and 7% catalyst dosage while examining reaction temperatures from 150 to 180 °C. At each temperature, the liquefaction rate rose rapidly during the early stage, when shell material, catalyst and solvent had extensive contact. The increase then slowed as reactive components were consumed, and the measurements eventually approached a plateau. At the same reaction time, higher temperatures consistently corresponded to higher liquefaction rates. To fit the data, the researchers treated liquefaction as an irreversible bimolecular reaction under four assumptions: the liquefying-agent and catalyst concentrations remained effectively constant, the rate constant followed the Arrhenius relationship with temperature, and the reaction was irreversible. Because solvent was present in large excess, they reduced the rate equation to the changing solid fraction.

Linear fits of the kinetic data gave apparent reaction orders of 4.90 at 150 °C, 3.55 at 160 °C, 3.56 at 170 °C and 3.82 at 180 °C. The apparent rate constant increased monotonically across the four temperatures, from 0.0091 at 150 °C to 0.0173 at 160 °C, 0.0261 at 170 °C and 0.0305 at 180 °C. The authors interpret the varying apparent orders as evidence that shrimp-shell liquefaction is not a single elementary reaction but a complex, multistage process involving multiple structural transformations and intermediate stages. An Arrhenius fit of the rate constants against reciprocal absolute temperature yielded a correlation coefficient of 0.9708 and an activation energy of 64.52 kJ/mol.

The researchers then applied transition-state theory and the Eyring relationship to estimate apparent activation parameters. Gibbs free energy of activation was positive throughout the tested range, increasing from 121.39 kJ/mol at 150 °C to 122.04 kJ/mol at 160 °C, 123.43 kJ/mol at 170 °C and 125.71 kJ/mol at 180 °C; its average was 123.14 kJ/mol. Apparent activation enthalpy changed comparatively little, declining from 30.98 to 30.73 kJ/mol across the same range, with an average of 30.85 kJ/mol. Activation entropy was negative, ranging from −213.65 to −209.60 J/(mol·K) and averaging −211.66 J/(mol·K). The authors associate the negative value with increased order during activated-complex formation and possible solvation of intermediates by the excess polyols. They also interpret the relatively low activation enthalpy as consistent with simultaneous bond cleavage and new bond formation, rather than a process limited to breaking one biological macromolecular bond.

Taken together, the study characterizes shrimp-shell liquefaction in this mixed-solvent, sulfuric-acid system as a temperature-dependent multistage process. It supplies both an experimentally validated operating point and an apparent kinetic description: 173 °C, a 14:1 liquid-to-solid ratio, 7% catalyst and 108 minutes yielded 42.35% ± 0.84%, while the fitted activation energy was 64.52 kJ/mol. The scope remains laboratory-based and the measured rate primarily represents organic-biomass conversion because calcium carbonate dissolution was limited. The experiment did not test continuous or pilot-scale operation, solvent recovery, life-cycle impacts, varied commercial feedstocks or the performance of industrial products made from the liquefied material. Its principal result is therefore a quantified optimization and kinetic model for converting shrimp-shell powder under a controlled set of conditions.

Subject of Research: Optimization and chemical kinetics of shrimp-shell liquefaction using mixed polyols and sulfuric acid

Article Title: Kinetic analysis and parameter optimization of shrimp shell liquefaction

Article References: Zhang, J., Liu, X.-C., Chen, A., Zhang, H.-Y., & Zhang, Y.-C. (2026). Kinetic analysis and parameter optimization of shrimp shell liquefaction. Frontiers in Bioengineering and Biotechnology, 14, Article 1936936. https://doi.org/10.3389/fbioe.2026.1936936

Image Credits: AI Generated

DOI: 10.3389/fbioe.2026.1936936

Keywords: shrimp-shell waste, biomass liquefaction, polyethylene glycol 400, glycerol, sulfuric acid, response surface methodology, chemical kinetics, activation energy, transition state theory, marine biomass, Kinetic, analysis

The stakes could hardly be higher. China’s total carbon dioxide emissions have surpassed 20 billion tons, roughly 30.65 percent of the global total, and the steel industry alone accounts for about 15 percent of the country’s emissions. Within ironmaking, blast furnaces are responsible for around 70 percent of the sector’s CO2 output. Coke is indispensable in these furnaces because it serves simultaneously as reducing agent, heat source, carburizing agent, and structural support for the burden column, but producing it releases CO2, CO, SO2, and nitrogen oxides along the way. Finding ways to stretch every kilogram of metallurgical coke has therefore become a central goal of low-carbon ironmaking research.

Nut coke is the fraction of screened coke smaller than 25 millimeters that has traditionally been burned as simple fuel rather than charged into the furnace. In every other respect it is virtually identical to the larger metallurgical coke, which is why steelmakers in China, the United States, France, and Japan already consume it at rates of 20 to 50 kilograms per ton of hot metal. Earlier plant trials by Murao and colleagues showed that controlled distribution of small coke during burden charging increased the blast furnace permeability index by about 5 percent while improving gas utilization by roughly 0.4 percent, and operating data analyzed by Logachov’s team indicated that nut coke consumption could be raised to 40 kilograms per ton of hot metal without hurting furnace productivity, with one kilogram of coke briquettes replacing approximately 0.67 kilograms of conventional coke.

What previous laboratory work had largely overlooked, however, was the effect of nut coke particle size itself. Most co-reduction studies employed nut coke of 10 to 12.5 millimeters, leaving the size question unexamined. Jiang’s team set out to close that gap by testing three size fractions—5 to 10 millimeters, 10 to 15 millimeters, and 15 to 20 millimeters—mixed with sinter of 10 to 12.5 millimeters at addition ratios of 0, 2, 4, 6, and 8 percent. The sinter, supplied by a commercial steel company, contained 59.28 percent total iron and 11.17 percent FeO, with hematite as its primary mineral phase, while the nut coke carried 87.07 percent fixed carbon, a coke reactivity index of 23.4, and a coke strength after reaction of 71.32.

The isothermal reduction experiments were conducted at 900, 950, and 1000 degrees Celsius under a gas atmosphere of 70 percent nitrogen and 30 percent CO, with the reducing gas switched on after a protective nitrogen hold and the sample mass tracked continuously by a balance system. The results were unambiguous: the reduction index of the sinter climbed steadily as the nut coke addition ratio rose from 0 to 8 percent, and it fell as the particle size increased. At 900 degrees Celsius, sinter alone reached a reduction index of 80.41 percent, but with 8 percent of 5 to 10 millimeter nut coke the index rose to 85.55 percent. The same 8 percent addition of 10 to 15 millimeter and 15 to 20 millimeter nut coke yielded only 83.95 percent and 82.57 percent, respectively. The pattern held at 950 and 1000 degrees Celsius, where the finest fraction pushed the reduction index to 88.52 and 90.56 percent, confirming that the optimum condition in this system is 8 percent nut coke of 5 to 10 millimeters.

The mechanism behind these numbers is a two-part story of chemistry and physics. Chemically, CO strips oxygen from hematite in a stepwise cascade—Fe2O3 first becomes Fe3O4, then FeO, and finally metallic Fe—generating CO2 in the process. Nut coke counteracts the resulting loss of reducing potential through the Boudouard reaction, in which solid carbon reacts with CO2 to regenerate CO, sustaining the atmosphere needed to keep the iron oxides shrinking. Physically, sinter particles tend to adhere and agglomerate at elevated temperatures, choking the burden bed and creating stagnant zones where the reducing gas never reaches the ore. The mixed nut coke alleviates this agglomeration, improves bed permeability, and ensures more complete contact between gas and sinter. Intriguingly, the study suggests that larger nut coke improves permeability so well that the reducing gases flow through faster, shortening their residence time and actually limiting reduction—which may explain why coarser fractions underperform the finest ones.

To probe the kinetics, the researchers applied the classical unreacted core model to their thermogravimetric data, testing whether the reaction was limited by interfacial chemistry, by gas diffusion through the solid product layer, or by a mixture of both. External diffusion was ruled out because the gas velocity of 0.26 meters per second far exceeds the critical velocity of 0.05 meters per second for diffusion-controlled reactions. The interfacial chemical reaction model produced excellent linear fits, with coefficients of determination above 0.95, while the diffusion and mixed-control models performed poorly—demonstrating that the rate-limiting step is the chemical reaction at the oxide interface itself. The fitted rate constants also showed that sinter mixed with 5 to 10 millimeter nut coke reacted fastest, consistent with the reduction index measurements.

From the Arrhenius relationship between the rate constants and temperature, the team calculated apparent activation energies of 10.81, 10.48, and 10.89 kilojoules per mole for the three nut coke fractions at 8 percent addition, compared with 12.39 kilojoules per mole for sinter alone. These values are strikingly low next to previous reports: Jin and colleagues found 28.88 kilojoules per mole for sinter-coke systems, Mousa’s team reported 24 to 40 kilojoules per mole, and Bao’s work on iron carbon agglomerates reached 72.58 to 97.41 kilojoules per mole. The authors attribute the low values to the sinter’s superior reducibility, the narrow 900 to 1000 degree Celsius window used for the Arrhenius fit, and the extra CO regenerated by the Boudouard reaction, while noting that activation energy is strongly influenced by ore type, particle size, gangue composition, reducing atmosphere, and raw material properties.

Microstructural analysis backed up the macroscopic picture. X-ray diffraction of the reduced products showed Fe, FeO, and SiO2 as the dominant phases, while scanning electron microscopy with energy-dispersive spectroscopy revealed FeO progressively transforming into Fe, with iron phases crystallizing and growing into a dense network structure that coarsened as the temperature rose from 900 to 1000 degrees Celsius. The SEM images also confirmed the ranking of the mixtures, with the 5 to 10 millimeter fraction showing the most advanced reduction at every temperature.

For an industry under pressure to decarbonize, the message is practical and precise: when charging nut coke mixed with sinter, favor the smaller end of the size spectrum and push the addition ratio toward 8 percent. Doing so promotes efficient utilization of a coke fraction that would otherwise be wasted as fuel, partially replaces premium metallurgical coke, lowers ironmaking costs, and trims the carbon footprint of the most emissions-intensive step in steel production. As hydrogen metallurgy advances and blast furnaces evolve, understanding these coupled reduction behaviors at the particle scale will be essential groundwork for the furnaces of a low-carbon future.

Subject of Research: Isothermal reduction behavior and kinetics of sinter mixed with nut coke of varying particle sizes and addition amounts

Article Title: Reduction behaviors between sinter and nut coke with varying particle sizes and addition amounts

Article References: Jiang, X., Fan, K., Jiang, Y., He, L., Ai, M., Zheng, H., & Shen, F. (2026). Reduction behaviors between sinter and nut coke with varying particle sizes and addition amounts. Results in Engineering, 32, Article 113546. https://doi.org/10.1016/j.rineng.2026.113546

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.113546

Keywords: blast furnace, nut coke, sinter, ironmaking, reduction kinetics, Boudouard reaction, carbon emissions, activation energy, XRD, SEM-EDS, Reduction, behaviors

The team synthesized three compositions of silver-doped zinc oxide, written chemically as Zn(1-x)Ag(x)O with silver fractions x of 0.00, 0.02, and 0.04, using a straightforward co-precipitation route. Zinc acetate dissolved in distilled water was mixed with carefully measured amounts of silver acetate, then sodium hydroxide was added dropwise at a controlled rate while the solution was stirred at 60 degrees Celsius. After washing, drying, and annealing at 450 degrees Celsius, the powders were pressed into pellets and interrogated with X-ray diffraction, high-resolution transmission electron microscopy, infrared spectroscopy, and broadband dielectric spectroscopy spanning frequencies from 0.1 hertz to 20 megahertz and temperatures from 30 to 150 degrees Celsius.

X-ray diffraction confirmed that every sample retained the hexagonal wurtzite crystal structure of zinc oxide, with no detectable secondary phases even at the highest silver loading. Rietveld refinement of the diffraction data revealed a subtle but telling non-monotonic trend: at 2 percent silver the lattice parameters expanded slightly, consistent with larger silver ions replacing zinc ions in the crystal lattice, but at 4 percent the lattice parameters snapped back to nearly the undoped values. The researchers attribute this reversal to competing effects, including silver segregation at grain boundaries and defect clustering that counteracts the simple ionic-size substitution picture at higher concentrations.

Perhaps the most striking structural finding is that crystallite size and particle size move in opposite directions as silver content rises. The coherent crystalline domains grew from 22.83 to 25.91 nanometers, while the overall particle size measured by transmission electron microscopy shrank dramatically from about 122 nanometers for pure zinc oxide to roughly 47 nanometers at 4 percent doping. The explanation involves two competing mechanisms: silver incorporated at zinc sites promotes atomic rearrangement and reduces defects during annealing, allowing larger crystalline domains to form, while silver that segregates to particle surfaces acts as a barrier that prevents particles from clumping together. Dislocation density, micro-strain, specific surface area, and porosity all fell with increasing silver content, confirming that the dopant cleans up the crystal lattice even as it keeps the particles dispersed.

From the infrared spectra, the team extracted a battery of mechanical parameters that are rarely measured alongside electrical properties. The Debye temperature, a measure of the stiffness of atomic bonding, climbed from 610.87 to 632.47 kelvin with increasing silver content. Young’s modulus, shear modulus, bulk modulus, and hardness all rose in parallel, as did the longitudinal, shear, and mean elastic wave velocities. The researchers attribute these gains to the increased density, reduced porosity, and shortened metal-oxygen bond lengths that accompany silver substitution. All samples remained brittle in character, and the residual stress stayed tensile at roughly 0.195 to 0.198 gigapascals, essentially unchanged by doping.

On the electrical side, the dielectric constant and dielectric loss both increased with temperature and silver content, while the alternating-current conductivity climbed across the entire frequency range. The team identified the underlying conduction mechanism as correlated barrier hopping, in which charge carriers leap over energy barriers between localized defect sites in a correlated fashion. The frequency exponent extracted from the conductivity data fell between 0.05 and 0.55 and decreased with rising temperature, a signature that distinguishes correlated barrier hopping from competing models such as quantum mechanical tunneling. The binding energy associated with this hopping process ranged from 0.163 to 0.345 electronvolts and shrank as temperature or silver content increased.

Activation energy measurements told a similar story. Using the Arrhenius relation, the team found that the energy barrier for charge carriers dropped from as high as 0.68 electronvolts in pure zinc oxide down to 0.187 electronvolts in the most heavily doped sample, with the lowest values occurring at the highest frequencies. The interpretation is that silver introduces shallow impurity levels within the zinc oxide bandgap, raising the free carrier concentration and lowering the energy needed for electrons to hop between neighboring grains. At high frequencies, carriers are already oscillating with the applied field and require less additional energy to respond, further reducing the effective barrier.

Impedance spectroscopy, analyzed through Cole-Cole plots, revealed single semicircular arcs corresponding to parallel resistor-capacitor circuits for all samples. The impedance of grains, grain boundaries, and the total series resistance all decreased with increasing silver content or temperature, falling from as high as 100 million ohms down to roughly 2,000 ohms, while the effective capacitance rose from 0.005 to a remarkable 38.73 microfarads at 150 degrees Celsius for the 4 percent doped sample. That capacitance is about 28 times higher than what pure zinc oxide achieves at the same temperature, a combination of low series resistance and high capacitance that the researchers identify as ideal for supercapacitor electrodes, where energy dissipated in internal resistance must be minimized.

The most novel contribution of the study is the quantitative correlation analysis linking mechanical and electrical properties measured on the same batch of samples. Young’s modulus correlated strongly with the dielectric constant, with a coefficient of determination of 0.82, indicating that stronger interatomic bonding goes hand in hand with a stronger polarizable response. Hardness and alternating-current conductivity showed a moderate correlation of 0.66, while the relationship between porosity and effective capacitance was essentially perfect at 1.00, confirming that squeezing out pores is the dominant mechanism behind the capacitance boost. Particle size and activation energy correlated moderately at 0.50, reflecting the fact that smaller particles facilitate charge hopping.

Taken together, the results establish that the same microstructural features that make silver-doped zinc oxide mechanically robust, namely denser packing, fewer defects, and stronger bonds, also make it a better dielectric and conductor. The researchers suggest that the simultaneous enhancement of elastic moduli, hardness, dielectric constant, conductivity, and capacitance opens a path toward multifunctional oxide nanomaterials for advanced electronics, energy storage, and solar energy applications. While questions remain about the exact distribution of silver between substitutional sites, grain boundaries, and possible minor silver-rich clusters at higher doping levels, the work provides a comprehensive framework that other groups can now apply to related doped oxide systems, and it demonstrates that mechanical toughness and electrical performance need not be traded off against each other in nanoscale semiconducting oxides.

Subject of Research: Correlation between mechanical and dielectric properties of pure and silver-doped zinc oxide nanoparticles

Article Title: On the correlation between mechanical and electrical properties of pure and Ag doped ZnO nanoparticles

Article References: Mohamed, M., Ismail, Y. A. M., Bouzidi, M., Khan, Z. R., & Sedky, A. (2026). On the correlation between mechanical and electrical properties of pure and Ag doped ZnO nanoparticles. Scientific Reports, 16(1), Article 28493. https://doi.org/10.1038/s41598-026-67220-7

Image Credits: AI Generated

DOI: 10.1038/s41598-026-67220-7

Keywords: zinc oxide, silver doping, nanoparticles, dielectric properties, mechanical properties, correlated barrier hopping, impedance spectroscopy, elastic moduli, supercapacitors, wurtzite structure, activation energy, semiconductors

The work addresses a persistent headache in battery materials chemistry. Conversion-type anodes such as metal phosphides store sodium through a multi-step reaction in which sodium ions infiltrate the lattice, break metal–phosphorus bonds, and form sodium phosphide alongside metallic nanodomains. This mechanism unlocks capacities well beyond graphite intercalation chemistry, but it also subjects the electrode to enormous volume swings—often several hundred percent—that pulverize particles, sever electrical pathways, and delaminate conventional slurry-cast coatings from their current collectors. Metal phosphides also tend to have sluggish sodium-ion solid-state diffusion and moderate electronic conductivity, making the choice of crystal phase, morphology, and electrode architecture as important as the raw chemistry itself.

The Chinese team’s architecture attacks the structural fragility head-on. They grew the active material directly onto carbon cloth, a flexible woven carbon substrate that acts simultaneously as a binder-free support and an efficient current collector. Eliminating polymer binders and metal foils removes the interfaces where most conversion anodes fail, while the porous three-dimensional fabric gives the active phase room to breathe as it expands and contracts during cycling. But the truly novel element lies upstream of the electrochemistry, in the synthesis pretreatment itself. The authors loaded a nickel-based precursor onto the carbon cloth from either ethanol or water solution, then subjected both samples to an identical phosphating process driven by sodium hypophosphite (NaH₂PO₂), a common phosphorus source that decomposes to deliver reactive phosphorus species at moderate temperatures.

The divergence in results is striking. When ethanol served as the loading solvent, the phosphating reaction yielded hexagonal Ni₅P₄ (space group P6₃mc), a phosphorus-rich nickel phosphide considered attractive for alkali-ion storage. When water was the solvent, the same hypophosphite treatment predominantly produced Ni₂P₄O₁₂, a nickel phosphate containing oxygen retained from the aqueous processing environment. The researchers attribute this solvent-driven phase selection to the distinct chemical microenvironments created during precursor deposition. Ethanol’s reducing, less hydrolytic character appears to shift the local phosphorus chemical potential and steer intermediate formation pathways toward full phosphidation, whereas water promotes hydrolysis and oxidation pathways that trap oxygen in the final product. In effect, a decision made in the wet-chemistry stage—long before any electrochemical testing—determines which crystal structure emerges, which morphology forms, and ultimately how the electrode performs.

Both electrodes proved remarkably durable, belying the reputation of conversion materials for rapid fade. The Ni₅P₄@CC anode sustained a discharge-specific capacity exceeding 100 mAh g⁻¹ after 1000 cycles at a current density of 100 mA g⁻¹, and it recovered 92.8% of its capacity when rate-performance testing swung the current density from 50 up to 2000 mA g⁻¹ and back. The Ni₂P₄O₁₂@CC anode performed comparably, retaining 121.1 mAh g⁻¹ after 1000 cycles with a 92.2% rate recovery. While neither figure sets records in absolute capacity, the combination of four-figure cycle life, binder-free construction, and near-complete rate recovery signals electrodes engineered for stability rather than one-shot headline numbers—a trait that matters enormously for real-world grid storage, where sodium-ion chemistry is expected to make its commercial debut.

The deeper contribution of the study lies in its electrochemical kinetics analysis, which dissects why each phase behaves as it does. Using temperature-dependent measurements, the team extracted activation energies for the two competing steps that govern sodium storage: charge transfer across the electrode–electrolyte interface and solid-state diffusion of sodium ions through the crystal. Ni₅P₄ emerged as the kinetically more agile interactor at its surface, exhibiting a lower charge-transfer activation energy of 48.63 kJ mol⁻¹, meaning sodium ions face a smaller barrier when passing from the electrolyte into the electrode. That advantage comes at a price: Ni₅P₄ carries a higher solid-state diffusion barrier of 67.19 kJ mol⁻¹, so sodium atoms move more reluctantly once inside the bulk crystal.

What rescues Ni₅P₄ from its own diffusion penalty is a structural quirk. The compound offers interstitial sodium storage sites—voids in the lattice between the nickel and phosphorus sublattices—into which sodium ions can slip without needing to displace host atoms. Interstitial storage typically proceeds faster and with less lattice strain than substitutional insertion, effectively providing a kinetic bypass that compensates for the material’s elevated diffusion barrier. This interplay between interfacial kinetics, bulk transport, and storage-site geometry illustrates a broader lesson for the field: phase selection is not merely about capacity numbers but about the entire sodium-transport landscape, and small synthesis choices can reshape that landscape in measurable ways.

The transferability of the solvent-control principle may prove to be its most valuable feature. Hypophosphite phosphating is a workhorse technique across transition metal phosphide synthesis, used for cobalt, iron, tin, molybdenum, and copper phosphide electrodes in lithium, sodium, and even potassium-ion systems. If the same ethanol-versus-water logic applies across that family—and the authors position solvent selection as an effective and transferable strategy—it gives battery chemists a cheap, scalable dial for tuning phase purity, oxygen incorporation, and morphology without reformulating precursor chemistry or investing in exotic equipment. Because the pretreatment happens before phosphating, it slots neatly into existing synthesis workflows, and carbon cloth electrodes grown this way could suit flexible or structurally integrated battery formats where binder-free architecture is especially valuable.

The timing is favorable. Sodium-ion batteries are attracting renewed industrial investment because sodium is abundant, geopolitically unconstrained, and compatible with aluminum current collectors on both electrodes, trimming cost and weight. Nonaqueous liquid electrolytes for the technology have matured rapidly, and recent reviews of metal phosphide anodes highlight the family’s combination of high theoretical capacity and reasonable operating voltage as a key asset for next-generation cells. What has been missing is precise synthetic control over which phosphide phase forms and how it is anchored to the current collector—precisely the gap this study targets. By demonstrating that a solvent swap in a pretreatment step can dictate phase composition, morphology, and sodium-storage kinetics end to end, the Shenyang-based researchers have added a deceptively simple tool to the battery engineer’s kit, one that turns an ordinary bottle of ethanol into an instrument of crystal engineering.

The work, funded by the Basic Research Projects of the Liaoning Provincial Department of Education and the Doctoral Research Start-up Project of the Liaoning Provincial Natural Science Fund, was received in June 2026 and published on 13 October 2026. Its conclusions stop short of commercial claims—capacities of around 100 to 120 mAh g⁻¹ after 1000 cycles are modest by anode standards—but the study’s real legacy may be conceptual. It shows that in conversion-type battery materials, the boundary between synthesis chemistry and electrochemical performance is thinner than often assumed. Choose the right solvent at the pretreatment stage, and the crystal lattice, the diffusion pathways, the interfacial charge transfer, and the long-term cycling stability all follow. For a technology racing to displace lithium from the grid, that kind of upstream control could be worth far more than any single record-breaking electrode.

Subject of Research: Solvent-controlled synthesis of nickel phosphide anode materials and sodium-ion storage kinetics in sodium-ion batteries

Article Title: Solvent-controlled hypophosphite phosphating method for pretreatment: Structure and kinetics of nickel phosphide anode in sodium-ion batteries

Article References: Gong, H., Jin, J., Zhang, X., Zhou, L., Cheng, Z., & Du, T. (2026). Solvent-controlled hypophosphite phosphating method for pretreatment: Structure and kinetics of nickel phosphide anode in sodium-ion batteries. Ionics. https://doi.org/10.1007/s11581-026-07576-y

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07576-y

Keywords: sodium-ion batteries, nickel phosphide, Ni5P4, anode materials, hypophosphite phosphating, solvent control, carbon cloth, electrochemical kinetics, activation energy, energy storage, transition metal phosphides, binder-free electrode

The root of the decades-long scatter lies in an experimental trap that is easy to describe but fiendishly hard to escape. To measure how creep rate changes with temperature, researchers need to compare deformation at different temperatures. The traditional approach was to prepare several snow samples that were supposedly identical and test each one at a different temperature. The problem is that no two snow samples are ever truly identical. Snow is a two-phase material of sintered ice crystals and air, and its densification depends intimately on the spatial arrangement of the ice skeleton. Recent work by the same group showed that even a 5 percent difference in density between two samples, which is common in practice, can shift the strain rate by about 50 percent, equivalent to a temperature difference of roughly 4 degrees. Add to that the temperature fluctuations of typical cold rooms, which reach plus or minus 0.6 degrees Celsius due to defrost cycles and heating from X-ray sources, and the uncertainty swamps the signal being measured.

Védrine’s team solved the problem with an elegant inversion of the protocol: instead of comparing different samples at different temperatures, they tested the same sample at a sequence of temperatures. The centerpiece is a newly developed thermo-mechanical cell, a slim aluminium cylinder 20 millimeters in diameter with walls just half a millimeter thick so that X-rays can pass through. Two Peltier thermoelectric modules at the top and bottom of the cell control the sample temperature independently of the surrounding cold room, keeping temperature differences within the cell on the order of a thousandth of a kelvin, with absolute accuracy better than half a degree. A hollow piston applies a controlled load, a miniature load cell beneath the sample verifies that the force stays constant and that the piston moves without friction, and a laser sensor tracks the vertical displacement of the sample with a resolution of one micrometer. The entire assembly rotates inside an X-ray tomograph, which images the evolving microstructure every eight hours.

The experimental protocol was deliberately gentle. Natural snow collected in the field was stored for months at minus 20 degrees Celsius, where it matured into decomposing and fragmented precipitation particles, then sieved and sintered for at least two weeks. Five samples with initial densities between 278 and 320 kilograms per cubic meter were loaded with a stress of 1.25 kilopascals, comparable to the overburden of a 45-centimeter layer of snow of that density. Each experiment lasted five days and comprised five one-day temperature steps from minus 6 to minus 18 degrees Celsius in 3-degree increments. Because the applied stress was low, the samples deformed only slightly, with a mean final vertical strain of just 4 percent, keeping microstructural evolution to a minimum. Tomography confirmed that density changed by less than 4 percent and specific surface area by less than 7 percent over the whole test, meaning the ice framework remained essentially unchanged while the temperature varied.

One subtlety remained: even a small amount of densification causes geometric hardening, an increase in the reference stress of the ice matrix that slows creep even at constant temperature. To disentangle this effect from genuine temperature sensitivity, the team used a state-of-the-art snow viscoplastic model that describes strain rate as a function of stress, solid fraction, and a temperature-dependent prefactor. By dividing the measured strain rate by the mechanical component, they isolated the pure temperature response. The approach proved robust: neglecting geometric hardening entirely would have produced an activation energy about 10 percent too high, but within the physically meaningful range of model parameters the estimated temperature sensitivity varied by only 3 percent. Digital volume correlation applied to the tomographic images independently confirmed that the laser-based displacement measurements faithfully captured the bulk deformation of the samples.

The results are striking. When the corrected strain-rate prefactor is plotted against inverse temperature on a logarithmic scale, the data from all five samples collapse onto a single master curve, revealing a clear Arrhenius-type relationship, but with a kink. A single Arrhenius fit gives an apparent activation energy of 105 plus or minus 6 kilojoules per mole, yet it fails to capture a change in slope around minus 12 degrees. A two-regime fit is statistically preferred according to the Akaike Information Criterion and yields an activation energy of 126 plus or minus 6 kilojoules per mole above a transition temperature of minus 13 plus or minus 1 degree Celsius, and 51 plus or minus 18 kilojoules per mole below it. In other words, snow creeps far more readily per degree of warming near the melting point than in colder conditions, and the transition between the two behaviors is sharp.

Remarkably, this two-regime pattern mirrors what has long been known for polycrystalline ice. Classic creep studies of glacier ice dating back to Glen’s work in the 1950s reported activation energies of roughly 60 kilojoules per mole below minus 10 degrees and around 130 kilojoules per mole above, values that bracket the new snow measurements almost perfectly. This is intriguing because earlier research by Védrine and colleagues showed that ice inside snow does not deform like dense polycrystalline ice, since the pore network must accommodate the deformation and creep is dominated by basal glide, the sliding of crystal planes along their base. The authors caution that the apparent similarity may be partly deceptive. When they allowed the stress exponent to vary with temperature, following single-crystal measurements of basal slip reported by Jones and Brunet in 1978, the entire dataset could instead be described by a single effective activation energy of 78 plus or minus 6 kilojoules per mole, consistent with basal-slip creep. Part of the apparent bilinear behavior may therefore reflect a temperature-dependent stress exponent rather than a true change in the underlying deformation mechanism.

Whatever the microphysical explanation, the practical implications for snowpack modeling are immediate. The team compared their new parametrization with the settlement laws used in two widely deployed detailed snowpack models, Crocus and Snowpack. The Brun et al. 1992 formulation implemented in Crocus corresponds to an activation energy of about 62 kilojoules per mole, close to the new low-temperature value but far below the high-temperature one, and it exhibits the weakest temperature sensitivity of all. The Kojima 1975 law for fresh snow in Snowpack behaves similarly at low densities. Only the new parametrization captures two distinct temperature regimes. In simulations of a one-meter isothermal snowpack with an initial density of 100 kilograms per cubic meter, the differences matter: after seven days, a snowpack held at minus 20 degrees Celsius is predicted to be 20 to 34 percent taller than one at minus 6 degrees, depending on which law is used, and the new measurements generally imply faster compaction at low densities than either existing formulation predicts.

Accurate snow compaction is not a niche concern. Settlement rates shape snow stratigraphy, which in turn governs avalanche forecasting, estimates of snow water equivalent for hydrology and reservoir management, and even the interpretation of polar ice cores, where firn densification laws link trapped air to paleoclimate records. The study’s authors note that their experiments did not extend above minus 6 degrees Celsius, leaving open whether the creep rate accelerates nonlinearly as the melting point approaches, as often reported for polycrystalline ice, or whether a basal-slip-dominated material like snow behaves differently. They also emphasize that dedicated experiments are still needed to constrain how the stress exponent of basal slip varies with temperature. But the methodological lesson is already secure: by holding the microstructure fixed and letting only the temperature change, the Grenoble team has turned a seventy-year-old scatter plot into a coherent physical law, and given snowpack models their most rigorous temperature calibration to date.

Subject of Research: Temperature dependence of snow viscoplastic creep measured through controlled in-tomograph experiments

Article Title: Temperature sensitivity of snow viscoplasticity: Evidence from controlled creep experiments

Article References: Védrine, L., Brun, M., Bozon, M., Laurent, B., & Hagenmuller, P. (2026). Temperature sensitivity of snow viscoplasticity: Evidence from controlled creep experiments. The Cryosphere, 20(10), 5813-5828. https://doi.org/10.5194/tc-20-5813-2026

Image Credits: AI Generated

DOI: 10.5194/tc-20-5813-2026

Keywords: snow, viscoplasticity, creep, activation energy, Arrhenius law, snowpack modeling, X-ray tomography, ice mechanics, avalanche forecasting, The Cryosphere, Peltier temperature control, firn densification

The study, led by Yuri Galliano of the University of Genoa together with colleagues from Genoa, Roma Tre and Bologna, was published in the European Journal of Mineralogy. The researchers combined three high-temperature, in situ analytical techniques with equilibrium thermodynamic calculations to pin down the transformation. Their target reaction is deceptively simple: taranakite, with the formula K3Al5(PO3OH)6(PO4)2·18H2O, loses six water molecules to become francoanellite, K3Al5(PO3OH)6(PO4)2·12H2O. Both minerals share the same layered architecture of aluminophosphate sheets, but taranakite carries additional water arranged in hexagonal interlayers that strikingly resemble the structure of ordinary ice. Francoanellite lacks these interlayers entirely, with hydrogen bonds directly connecting the layers in their place.

To predict the temperature at which this reaction reaches equilibrium, the team turned to the polyhedral approach, a modelling technique that estimates the bulk thermodynamic properties of a mineral by summing the contributions of its individual cation coordination polyhedra. Using published temperature-dependent functions for the Gibbs free energy of the constituent oxide and water units, they calculated an equilibrium transformation temperature of 369.12 kelvin, equivalent to about 96 degrees Celsius. That figure might seem far removed from the cool, damp interiors of caves, and indeed it is. The real story, as the experiments revealed, lies not in equilibrium thermodynamics but in the remarkably low kinetic barrier of the reaction.

The experimental evidence came from three complementary probes. High-temperature X-ray powder diffraction, performed at the University of Padua, tracked the long-range crystal structure as the sample was heated step by step from room temperature to 438 kelvin. Taranakite reflections remained stable up to about 358 kelvin, above which they steadily weakened while the peaks of francoanellite grew, until francoanellite stood alone at 398 kelvin. The basal spacing of the layered structure contracted from roughly 15.85 angstroms to 13.80 angstroms, a direct signature of the disappearing water interlayers. Rietveld refinement showed that taranakite’s unit cell expanded slightly through ordinary thermal expansion before dehydration began, while the francoanellite cell shrank slowly until the material collapsed into an X-ray amorphous state above about 418 kelvin.

Infrared spectroscopy added a molecular-level view of the water loss. The FTIR spectra of taranakite are a complex convolution of phosphate, hydrogen phosphate, ammonium, hydroxyl and water vibrational modes, and the researchers followed how each family of bands evolved with temperature. The integrated absorbance of the water bending and stretching regions decreased gently up to about 363 kelvin, then changed slope in a way compatible with the onset of francoanellite formation, before accelerating dramatically above roughly 403 kelvin as the remaining crystallisation water was expelled and the structure amorphised. Crucially, the spectra showed that the transformation begins with the breaking of weak hydrogen bonds that tether the interlayer water molecules to the aluminophosphate layers, the weakest links in the structural chain.

Micro-Raman spectroscopy proved to be the most sensitive witness of the phase change. The symmetric stretching vibration of the phosphate units appears near 952 wavenumbers in taranakite and shifts to about 933 wavenumbers in francoanellite, positions that can even be converted into precise phosphorus-oxygen bond lengths of 1.559 and 1.565 angstroms, matching the structural models beautifully. By fitting these two peaks in spectra collected during heating, the team could watch taranakite fade and francoanellite emerge in real time. Better still, by holding the sample at fixed temperatures of 353, 358, 363 and 373 kelvin and recording spectra every few minutes, they turned their spectrometer into a kinetic instrument, measuring how fast the transformation proceeds at each temperature.

From those isothermal runs, the researchers extracted the activation energy of the dehydration using several kinetic approaches, including Avrami and Austin-Rickett plots and a model-free method known as time to a given fraction. Within the temperature window where the reaction behaves consistently, the activation energy came out at just 7.6 plus or minus 0.7 kilojoules per mole. That is astonishingly low. Comparable dehydration reactions in variscite, montmorillonite clays and zeolites all demand more than 30 kilojoules per mole. The reason, the authors explain, is that the water molecules being released are not part of cation hydration shells but sit loosely in interlayers, bound by weak hydrogen bonds with long oxygen-oxygen distances. Once those bonds break, the transformation is essentially topotactic: the aluminophosphate layers survive intact and only new hydrogen bonds between layers need to form, keeping the energy barrier minimal. The slope values from the kinetic plots, all below one, suggest the reaction is diffusion-controlled, with water molecules escaping parallel to the layers along the interlayer channels.

These numbers solve a long-standing puzzle about francoanellite’s rarity and origin. Direct measurements inside actively decomposing guano mounds, such as those in Mulu Cave in Borneo, show temperatures seldom exceeding 30 degrees Celsius, far below the calculated equilibrium temperature of 96 degrees. But because the kinetic barrier is so small, only a modest temperature rise sustained over long periods is needed to push the reaction forward. The heat released by the exothermic microbial oxidation of organic matter in guano-admixed sediments, accumulating over tens to hundreds of years, is a plausible trigger. The researchers also note that anthropogenic heat sources, such as the powerful halogen spotlights used in tourist caves like Castellana in Apulia, where francoanellite was first discovered in 1976, could contribute. Alternative pathways, including direct precipitation from percolating solutions or dissolution-recrystallisation driven by humidity swings, remain possible but are now less necessary to invoke.

The study carries practical warnings as well as scientific insights. Taranakite transforms into francoanellite within tens of minutes at temperatures as low as 358 kelvin, conditions easily reached during routine sample preparation for X-ray diffraction, where heating is sometimes used to drive off environmental moisture. Curators and researchers handling phosphate-bearing cave samples must therefore take special care to avoid inadvertently dehydrating their specimens and destroying the very mineralogical record they hope to study. Beyond Earth, the work resonates with planetary science: hydrated sulfates and iron phosphates confirmed in the Martian regolith may have undergone similar dehydration histories, and understanding the thermodynamics and kinetics of such reactions could help reconstruct the hydrologic and atmospheric evolution of the red planet. For now, the humble guano piles of Italian caves have once again proven that even the smallest, strangest mineral archives can rewrite our understanding of how minerals live, change and die.

Subject of Research: Thermodynamics and kinetics of the dehydration transformation of guano-derived taranakite into francoanellite in cave environments

Article Title: Dehydration reactions in guano-derived minerals: the taranakite-to-francoanellite transformation

Article References: Galliano, Y., Campomenosi, N., Bellatreccia, F., Belmonte, D., De Waele, J., & Carbone, C. (2026). Dehydration reactions in guano-derived minerals: the taranakite-to-francoanellite transformation. European Journal of Mineralogy, 38(3), 353-372. https://doi.org/10.5194/ejm-38-353-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-353-2026

Keywords: taranakite, francoanellite, bat guano, cave minerals, dehydration, phosphate minerals, X-ray diffraction, Raman spectroscopy, FTIR spectroscopy, thermodynamics, activation energy, mineralogy

The alloy in question, Mg-8wt.%Li, sits in a sweet spot of composition. Above roughly 8 percent lithium by weight, the material becomes dual-phase, containing both the hexagonal close-packed alpha phase typical of magnesium and the body-centered cubic beta phase that lithium stabilizes. That b.c.c. beta phase is the secret ingredient: it deforms far more readily than the hexagonal phase, endowing the alloy with ductility that no other magnesium alloy system can match. The Mg–Li family holds the record for elongation among all magnesium alloys, although its absolute strength remains modest, which is precisely why understanding and controlling its deformation mechanisms matters so much for lightweight structural applications.

To push the alloy into its most deformable state, the team turned to high-pressure torsion, a severe plastic deformation technique in which a disk of material is squeezed under a nominal pressure of 4 gigapascals while being twisted through five full turns. The process shears the microstructure into an ultrafine grain structure. Electron microscopy and transmission Kikuchi diffraction revealed that the extruded material, which started with grains of about 2.2 micrometers, was refined to an average spatial grain size of roughly 0.4 micrometers, with individual subgrains resolved in the range of 0.15 to 0.40 micrometers. The two phases became elongated and aligned with the torsion direction, a signature of the intense shear the disk experienced.

Miniature tensile specimens, cut from the disk mid-radius by electric discharge machining with a gauge cross-section of just 0.8 by 0.8 millimeters, were then pulled at room temperature across strain rates spanning from 10^-5 to 10^-3 per second. The results were striking. The peak stress varied dramatically with strain rate, a hallmark of high strain rate sensitivity, and the alloy exhibited large elongations at the slowest rates of 10^-4 and 10^-5 per second. This unusual increase in ductility at low strain rates, previously reported for similar alloys, is exactly the behavior that makes dual-phase Mg–Li alloys candidates for room-temperature superplasticity, a property normally reserved for ceramics and exotic superalloys at soaring temperatures.

Creep tests added another layer of intrigue. Under constant loads between 10 and 100 megapascals at room temperature, and at 373 kelvin under 10 and 25 megapascals, the creep rates steadily decreased as strain accumulated. Such decelerating creep is normally seen in coarse-grained metals at high temperature, where dislocation substructures build up during the initial stage of deformation, but that explanation should not apply to an ultrafine-grained material whose grains are already smaller than any stable subgrain size. The authors point to a recent study on ultrafine-grained aluminum that attributed similar behavior to strengthening by dynamic recovery, and they adopted the strain rate at 2 percent strain as representative of the as-processed state for further analysis.

The most consequential number to emerge from the creep experiments was the activation energy. Using the temperature dependence of the creep rate between room temperature and 373 kelvin, the team estimated activation energies of 64 kilojoules per mole at 25 megapascals and 77 kilojoules per mole at 10 megapascals. Both values fall well below the 135 kilojoules per mole for self-diffusion and the 92 kilojoules per mole for grain boundary diffusion in pure magnesium. The authors attribute this reduction to the large fraction of the b.c.c. beta phase, which has a lower melting temperature and correspondingly lower diffusion barriers. Reported grain boundary diffusion energies for related alloys, 65 kilojoules per mole for Mg-9%Li and 61 kilojoules per mole for Mg-8%Li-1%Zn, bracket the measurements, and the team settled on 75 kilojoules per mole for their modeling. The low activation energy is a clear signal that thermally activated mechanisms are at work even at room temperature.

To interpret these observations, the researchers deployed a two-pronged computational strategy. First, they applied a recently updated model for grain boundary sliding, the mechanism in which grains slide past one another along their boundaries, which is the canonical explanation for superplastic flow. The model treats the total flow stress as the sum of a threshold stress, capturing other strengthening contributions such as solid solutions, and a grain boundary sliding contribution that depends on shear modulus, temperature, grain size, Burgers vector and the grain boundary diffusion coefficient. A rectified linear function is used as a mathematical constraint to prevent the model from predicting negative stresses when thermal activation is strong. Second, they trained machine learning algorithms on 67 carefully curated data points from the literature, restricted to dual-phase Mg–Li alloys containing no alloying elements other than lithium, with lithium contents between 8 and 12 weight percent, to keep composition effects from contaminating the analysis.

The machine learning lineup included two black-box models, support vector regression and random forest, and two white-box symbolic regression models, one unconstrained and one constrained by dimensional consistency. The black-box models, evaluated with Shapley Additive Explanations, agreed that temperature is the dominant control on flow stress, that strain rate plays an intermediate role, and that grain size matters only marginally. On the training data the algorithms performed well, with mean absolute percentage errors ranging from 11.5 percent for the random forest to 35.3 percent for support vector regression. But when the models were asked to predict the new experimental data generated in this study, the black-box approaches collapsed, producing errors exceeding 250 percent, while the grain boundary sliding model and the dimension-constrained symbolic regression held their ground at roughly 35 percent error.

The deeper story emerged when the team plotted predicted flow stress against grain size, strain rate and temperature and compared the trends with experiment. The experiments revealed a fascinating crossover: for grains larger than about half a micrometer, refining the grains strengthens the alloy in classic Hall–Petch fashion, but below that threshold, further refinement actually softens it, the inverse Hall–Petch regime. Only the grain boundary sliding model captured this transition cleanly. The black-box models failed to reproduce the steep strain rate dependence of the flow stress, with support vector regression even predicting a physically implausible negative strain rate sensitivity at high rates. The dimension-constrained symbolic regression, guided by physically meaningful features such as the Zener–Holomon parameter and dimensionless groups derived from the grain boundary sliding equations, performed far better than its unconstrained counterpart, demonstrating that embedding physical knowledge into machine learning pays real dividends.

The take-home message resonates well beyond magnesium. Machine learning models are only as trustworthy as the data behind them, and with a sparse training set of 67 points, the black-box algorithms interpolated plausibly but extrapolated badly, especially outside the temperature and strain rate ranges they had seen. The century-old physics-based model, by contrast, reproduced every experimental trend once its activation energy was adapted to the dual-phase alloy. For engineers dreaming of lightweight magnesium–lithium components that can be superplastically formed at room temperature, the study offers both a validated design tool and a cautionary tale: in materials science, the white box and the physics still matter, and the smartest models are those that know the laws they are trying to learn.

Subject of Research: Deformation mechanisms and grain boundary sliding in ultrafine-grained dual-phase Mg–Li alloys processed by high-pressure torsion

Article Title: Analysis of deformation mechanism of dual-phase Mg–Li alloy, processed by high-pressure torsion, using experiments and machine learning

Article References: Carvalho, A. P., Edalati, K., & Figueiredo, R. B. (2026). Analysis of deformation mechanism of dual-phase Mg–Li alloy, processed by high-pressure torsion, using experiments and machine learning. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13355-x

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13355-x

Keywords: magnesium-lithium alloy, high-pressure torsion, grain boundary sliding, severe plastic deformation, machine learning, superplasticity, creep, activation energy, Hall-Petch, symbolic regression, ultrafine grains, flow stress

The material at the heart of the work, Li7PS6, is a lithium argyrodite that exists in two crystalline forms: a high-temperature phase and a low-temperature phase. The high-temperature version is traditionally produced by firing lithium sulfide and phosphorus pentasulfide together at 600 to 700 degrees Celsius, and it conducts reasonably well once hot. The low-temperature phase, by contrast, has historically been a poor performer, with reported ionic conductivity of roughly 1.6 × 10⁻⁶ S·cm⁻¹ at 40 degrees Celsius when made by conventional solid-state reaction. That figure places it far below the threshold needed for practical battery operation, which is why most researchers have either worked at high temperatures or turned to other argyrodite chemistries such as Li6PS5Cl.

The Vietnamese team, led by corresponding author Nguyen Huu Huy Phuc, approached the problem from two directions at once. First, they abandoned the furnace entirely in favor of liquid-phase synthesis. A suspension of Li3PS4 was prepared by stirring lithium sulfide and phosphorus pentasulfide in tetrahydrofuran at 50 degrees Celsius for 24 hours. Adding more lithium sulfide dissolved in ethanol then triggered an immediate reaction that produced a yellowish solution, which was evaporated at about 90 degrees Celsius under reduced pressure and heat-treated at only 200 degrees Celsius for one hour. The result was phase-pure low-temperature Li7PS6, and remarkably, its ionic conductivity at 25 degrees Celsius measured 2.3 × 10⁻⁵ S·cm⁻¹, roughly ten times higher than the same phase prepared by solid-state reaction.

The second lever was chemical substitution. The researchers first ball-milled lithium sulfide and aluminum sulfide into a Li3AlS3 glass ceramic, then introduced controlled amounts of this dopant precursor into the ethanolic reaction mixture. The target composition, Li7−4xAlxP1−xS6−3x, embodies a simple charge-balance logic: each trivalent Al³⁺ ion that replaces a pentavalent P⁵⁺ ion in the crystal lattice must be accompanied by the removal of four lithium ions and three sulfide ions to keep the structure electrically neutral. Four compositions were prepared, spanning x values of 0, 0.1, 0.2 and 0.3, and all were handled in an argon-filled glove box with oxygen and moisture levels held below 1 ppm and 0.1 ppm respectively, reflecting the acute sensitivity of sulfide electrolytes to air.

Proving that the aluminum actually entered the crystal structure, rather than sitting in an inert second phase, required a battery of characterization techniques. X-ray diffraction patterns for the samples with x equal to 0.1 and 0.2 showed the signature of low-temperature Li7PS6 with no trace of the Li5AlS4 crystal that would betray undissolved dopant. Rietveld refinement against the structural model of the related argyrodite Li7Zn0.5SiS6 confirmed a tetragonal lattice in the I4/m space group, and revealed that the a and b lattice axes and the unit-cell volume grew steadily with aluminum content while the c axis stayed nearly constant. Scanning electron microscopy with energy-dispersive spectroscopy showed the electrolyte forming nanoparticles tens of nanometres across that agglomerate into secondary particles tens of micrometres wide, with aluminum uniformly dispersed throughout. Raman spectroscopy added further confirmation: the PS4³⁻ vibrational peaks shifted slightly to lower wavenumbers in the doped samples, a shift previously observed when P⁵⁺ is replaced by lower-valent cations in related argyrodites.

The doping story had a clear limit, however. At x equal to 0.3, the diffraction patterns revealed a mixture of both the low-temperature and high-temperature phases, and the Raman spectrum showed the isolated Li–S and Al–S peaks of unreacted Li3AlS3. Together these observations mark the solubility ceiling of aluminum in the low-temperature argyrodite lattice, and they explain why the highest doping level did not produce the best conductor. Crystalline content, calculated from the ratio of refined peak area to total diffraction profile area, ranged from 57 to 71 percent across the series, but the team found that conductivity did not track crystallinity, indicating that the crystal structure itself, rather than the amorphous fraction, governs lithium transport.

The electrical measurements delivered the headline result. Alternating-current impedance spectroscopy, performed on pellets pressed at 570 MPa with carbon paper blocking electrodes, gave room-temperature ionic conductivities of 2.3 × 10⁻⁵, 1.2 × 10⁻⁴, 7.4 × 10⁻⁵ and 3.2 × 10⁻⁵ S·cm⁻¹ for x equal to 0, 0.1, 0.2 and 0.3 respectively. The sweet spot at x equal to 0.1 represents a fivefold improvement over the undoped liquid-phase material and roughly fifty times the conductivity of solid-state-prepared low-temperature Li7PS6. The activation energy for conduction fell from 0.526 eV in the undoped sample to 0.368 eV at x equal to 0.1, the lowest of the series, before rising again at higher doping levels where parasitic phases appeared. Direct-current polarization confirmed that the material is a genuine ionic conductor: its electronic conductivity, measured at 1.8 × 10⁻⁸ S·cm⁻¹, is nearly four orders of magnitude below its ionic conductivity, a prerequisite for suppressing self-discharge in a real cell.

Perhaps the most scientifically valuable part of the study is the dissection of why the doped material conducts better. Using the Jonscher universal dielectric response to extract the lithium hopping frequency from the impedance data, the team separated total conductivity into two factors: how easily lithium ions jump between sites, and how many mobile charge carriers exist in the first place. The activation energy for hopping migration plummeted from 0.479 eV in undoped Li7PS6 to just 0.122 eV at x equal to 0.1, while the activation energy for mobile-ion formation rose from 0.223 to 0.321 eV. In other words, aluminum substitution makes each individual lithium jump dramatically easier, at the modest cost of slightly reducing the population of mobile carriers, and the mobility gain wins decisively. Dielectric loss analysis told the same story from a different angle: the migration energy extracted from the temperature dependence of the loss peaks was smallest for x equal to 0.1, and the characteristic migration time of the doped samples lengthened by about an order of magnitude relative to the undoped material, signaling a shift from short-range to long-range lithium diffusion.

Practical stability was not neglected. A symmetric lithium cell built with the x equal to 0.1 composition, cycled at a current density of 0.1 mA·cm⁻² with one-hour charge and discharge steps, ran for more than 100 cycles without any severe increase in overvoltage, indicating that the aluminum-doped electrolyte is reasonably stable in direct contact with lithium metal. Taken together, the results sketch a compelling recipe for next-generation solid electrolytes: a low-temperature, solution-based synthesis that avoids energy-hungry firing and the phase segregation it causes, combined with a precisely tuned aliovalent substitution that flattens the energy landscape for migrating lithium ions. If the same strategy transfers to other argyrodite systems, the manufacturing bottleneck that has kept solid-state batteries confined to laboratories may become considerably easier to break.

Subject of Research: Aluminum-doped argyrodite-type Li7PS6 solid electrolytes synthesized by wet-chemical routes and their lithium-ion conduction dynamics

Article Title: Li-ion dynamics and relaxation in wet-chemical synthesized argyrodite-type Li7−4xAlxP1−xS6−3x solid electrolyte

Article References: Quang, V. A., Toan, T. V., Tu, T. A., Ty, N. M., Anh, L. T., Anh, L. T. Q., & Phuc, N. H. H. (2026). Li-ion dynamics and relaxation in wet-chemical synthesized argyrodite-type Li7−4xAlxP1−xS6−3x solid electrolyte. Discover Electrochemistry, 3(1), Article 32. https://doi.org/10.1007/s44373-026-00120-7

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00120-7

Keywords: solid-state batteries, argyrodite, Li7PS6, solid electrolyte, ionic conductivity, aluminum doping, liquid-phase synthesis, lithium-ion hopping, impedance spectroscopy, activation energy, sulfide electrolyte, Rietveld refinement

The material at the heart of the study is a non-equiatomic high-entropy alloy with the composition 35Nb25V25Ti10Al5Zr, expressed in atomic percent. High-entropy alloys, first introduced to the materials world in 2004, break with the classical metallurgical tradition of building alloys around a single dominant element. Instead, they blend four or more principal elements in substantial proportions, producing a chaotic atomic landscape that can yield extraordinary combinations of strength, ductility, and radiation tolerance. In this case, the researchers deliberately chose niobium, vanadium, titanium, aluminum, and zirconium in unequal proportions, tuning the recipe to stabilize a single body-centered cubic crystal structure while exploring how that structure responds to hydrogen exposure at temperatures relevant to reactor operation.

To interrogate the alloy’s behavior, the team built a custom Sievert’s apparatus, a laboratory instrument that measures how much hydrogen gas a sample absorbs under controlled temperature and pressure. Experiments were conducted across a temperature window of 450 to 600 degrees Celsius, a range that brackets the operating conditions many advanced reactor concepts would impose on structural components. The measurements revealed a striking pattern: hydrogen uptake peaked in the 500 to 550 degree Celsius range, with absorption falling off both below and above that band. This temperature dependence offers practical guidance for any future deployment, since it defines the thermal regime in which the alloy interacts most strongly with hydrogen in its environment.

Perhaps the most technically revealing part of the study is the kinetic analysis, in which the researchers fitted their absorption data to classical solid-state reaction models. At 600 degrees Celsius, the hydrogen absorption followed clean first-order kinetics, meaning the rate of uptake scaled directly with the amount of hydrogen still available to be absorbed, a signature of a single dominant rate-limiting step. At the lower temperatures of 450 to 550 degrees Celsius, however, the behavior was more nuanced: an initial first-order stage gave way to what materials scientists call contraction-type kinetics, in which the reaction front progressively shrinks as it consumes an outer shell of available material. This two-stage behavior suggests that different physical processes govern hydrogen entry at different stages of exposure, a detail that will matter enormously for engineers trying to predict component lifetimes.

From the temperature dependence of the initial first-order stage, the team extracted an apparent activation energy of 59.68 kilojoules per mole. That single number is a thermodynamic fingerprint: it confirms that hydrogen ingress in this alloy is a thermally activated process, requiring atoms to surmount an energy barrier as they dissociate, penetrate the surface, and diffuse into the bulk. Knowing the activation energy allows researchers to extrapolate absorption rates to temperatures and timescales far beyond what can be measured in the laboratory, which is exactly the kind of predictive power needed when qualifying materials for reactors designed to operate for decades.

The structural evidence is where the story becomes genuinely exciting for nuclear applications. Using X-ray diffraction and scanning electron microscopy, the researchers examined the alloy after hydrogen charging at every test temperature. In conventional zirconium cladding alloys, such analysis would typically reveal hydride phases, the brittle compounds responsible for embrittlement and delayed hydrogen cracking. In the new high-entropy alloy, no hydride phases appeared at any temperature tested. The single-phase body-centered cubic structure survived hydrogen absorption intact, and the only structural change was a shift of the X-ray diffraction peaks toward lower angles, indicating a modest expansion of the lattice parameter as individual hydrogen atoms slipped into interstitial sites within the crystal.

That lattice expansion is the key to understanding the alloy’s remarkable behavior. In this material, hydrogen is accommodated entirely in solid solution, dissolved atom by atom in the gaps of the crystal lattice rather than being converted into a separate hydride compound. The disordered, chemically diverse environment of a high-entropy alloy presents hydrogen with a mosaic of interstitial sites of varying size and binding energy, and the density functional theory calculations performed by the team confirmed that hydrogen absorption into these sites is thermodynamically favorable. The computations also placed a ceiling on how much hydrogen the lattice can hold, predicting a maximum accommodation limit of approximately 0.05 weight percent.

That theoretical ceiling proved remarkably accurate. The experiments measured a saturation hydrogen uptake of approximately 0.03 weight percent at 500 degrees Celsius, an order-of-magnitude agreement with the computational prediction that validates the entire modeling approach. This kind of synergy between first-principles calculation and experiment is increasingly the gold standard in alloy development, because it means future candidates can be screened computationally before expensive synthesis and testing campaigns begin. For a field like nuclear materials, where qualification timelines are notoriously long, the ability to predict hydrogen behavior from quantum mechanical calculations alone could compress development cycles dramatically.

The broader context makes the result timely. Small modular reactors and other advanced nuclear concepts are moving forward worldwide, and each design ultimately rises or falls on the performance of its structural materials. Zirconium alloys, the workhorses of fuel cladding, have well-documented vulnerabilities to hydrogen pickup during corrosion, and accident-tolerant fuel programs have spent years evaluating alternatives ranging from coated claddings to iron-chromium-aluminum alloys. Refractory high-entropy alloys have separately attracted attention for their potential radiation tolerance, with studies suggesting that the chemical disorder in these materials can enhance defect recombination and reduce radiation damage. The new work adds a third leg to that stool, demonstrating that a refractory high-entropy alloy can also manage hydrogen exposure gracefully.

There are, of course, important caveats that the researchers themselves acknowledge. The alloy accommodates only a limited amount of hydrogen in solid solution, and while the absence of hydrides is a decisive advantage, the long-term consequences of repeated hydrogen uptake and release cycles, the interplay with simultaneous neutron irradiation, and the mechanical properties of hydrogen-charged material all remain open questions for future study. What the current results establish is a proof of principle with quantitative rigor: a non-equiatomic NbVTiAlZr high-entropy alloy can ingest hydrogen at reactor-relevant temperatures through well-characterized kinetic pathways, hold it in solid solution within a predictable limit, and preserve its crystal structure without forming the brittle phases that plague conventional materials. For a nuclear industry searching for materials that can survive increasingly punishing environments, that combination of stability, predictability, and design flexibility may prove to be exactly the breakthrough the field has been waiting for.

Subject of Research: Hydrogen absorption kinetics and hydride resistance in a non-equiatomic NbVTiAlZr high-entropy alloy for nuclear structural applications

Article Title: Hydrogen ingress kinetics and accommodation mechanism in a non-equiatomic NbVTiAlZr high-entropy alloy

Article References: Chakraborty, P., Mhaskar, A., Singh, S. K., Kumar, P., Singh, R. N., & Tewari, R. (2026). Hydrogen ingress kinetics and accommodation mechanism in a non-equiatomic NbVTiAlZr high-entropy alloy. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13846-x

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13846-x

Keywords: high-entropy alloys, hydrogen embrittlement, nuclear materials, hydrogen absorption kinetics, Sievert's apparatus, body-centered cubic structure, hydride formation, density functional theory, activation energy, refractory alloys, small modular reactors, zirconium alloys

The study, led by Watcharee Funfuenha and Wanich Limwanich of Rajamangala University of Technology Lanna, together with colleagues at Chiang Mai University, centered on a deceptively simple idea. Instead of using liquid titanium(IV) n-butoxide directly as an initiator, the researchers first allowed it to ring-open ε-caprolactone at 130 degrees Celsius with no solvent present, producing short living PCL chains that remain capped with reactive titanium-oxygen active centers. Three versions of these macroinitiators, dubbed TiCL2, TiCL4, and TiCL8, were prepared using 2, 4, and 8 mole percent of the titanium alkoxide respectively. Because the concentration of titanium determines how many chains grow from each metal center, the chain length and molecular weight of the macroinitiators increased as the titanium content decreased, giving the team a tunable family of initiators with precisely controlled architectures.

What distinguishes these materials from conventional initiators is that they are not merely catalysts but genuine macromolecular species, carrying living poly(ε-caprolactone) segments that can themselves seed further polymerization. The concept echoes earlier work with tin(II) macroinitiators, but titanium offers a compelling advantage: titanium compounds are generally regarded as low-toxicity and environmentally benign compared with organotin species, which have faced increasing regulatory scrutiny. By pre-forming the titanium-PCL adduct, the researchers create a species in which the reactive Ti-O bond sits at the end of an organic chain, ideally positioned to coordinate incoming monomer and insert it into the growing polymer, the classic coordination-insertion mechanism that underpins much of modern lactone polymerization chemistry.

To understand exactly how these macroinitiators behave, the team turned to differential scanning calorimetry, a technique more familiar for measuring melting points than for probing reaction kinetics. By monitoring the heat released as the polymerization proceeds under controlled heating rates of 4, 6, 8, and 10 degrees Celsius per minute, they were able, for the first time, to extract non-isothermal kinetic parameters for ε-caprolactone polymerization initiated by titanium macroinitiators. The approach follows recommendations from the ICTAC Kinetics Committee, the international body that sets standards for thermal analysis, lending rigor to the analysis. Intriguingly, only the most titanium-rich variant, TiCL8, proved effective at promoting the ring-opening polymerization under these dynamic heating conditions, suggesting that a minimum density of active centers is required for the reaction to proceed at an appreciable rate.

From the calorimetry data, the researchers applied the Kissinger-Akahira-Sunose isoconversional method, a well-established approach for extracting activation energies from experiments conducted at multiple heating rates. The results revealed a clear concentration dependence: the activation energy fell from 73.5 plus or minus 2.9 kilojoules per mole at 10 weight percent TiCL8 to 64.8 plus or minus 1.1 kilojoules per mole at 20 weight percent. In practical terms, a lower activation energy means the reaction proceeds more readily, requiring less thermal pushing to get over the energetic barrier. The frequency factor, determined by fitting an n-order reaction model to the data, followed the same trend, confirming that higher macroinitiator loadings genuinely accelerate the polymerization rather than merely shifting it within the experimental window.

The team went further, computing the activation enthalpy and activation entropy of the process through Eyring-type transition state analysis. At higher TiCL8 concentrations, the transition state formation was facilitated, but the activation entropy became more negative, indicating a more ordered activated complex. This is chemically intuitive: when many titanium centers coordinate monomer molecules simultaneously, the arrangement demands a greater degree of molecular organization than a sparse distribution of active sites would require. Together with a proposed coordination-insertion mechanism, in which the monomer coordinates to the titanium center before inserting into the Ti-O bond, these thermodynamic parameters paint a coherent picture of a reaction whose speed and efficiency can be dialed simply by adjusting the initiator architecture and loading.

Kinetics on a small scale, however, only matters if the chemistry survives scale-up. To test this, the researchers performed larger-scale polymerizations under the same solvent-free conditions using conventional heating. The outcome was striking: high molecular weight PCL was obtained from all three macroinitiators, with weight-average molecular weights reaching 7.18 by ten to the fourth, 7.81 by ten to the fourth, and 6.88 by ten to the fourth grams per mole for TiCL2, TiCL4, and TiCL8 respectively. Molecular weight in this range corresponds to robust, mechanically useful material suitable for film blowing, melt processing, and biomedical fabrication. Achieving it without any solvent not only eliminates a major source of waste and cost but also simplifies purification, since no residual reaction medium needs to be stripped from the product.

The green credentials of the process were then pushed further with microwave irradiation, an energy-transfer method that heats reaction mixtures volumetrically rather than through the vessel walls. Microwave-assisted polymerization sharply reduced reaction times and, crucially, rescued the performance of the less reactive macroinitiators. Under microwave conditions, TiCL2 and TiCL4, which had lagged behind in conventional runs, delivered PCL with weight-average molecular weights of 6.08 by ten to the fourth and 6.23 by ten to the fourth grams per mole respectively. This suggests that the energy profile of microwave heating preferentially benefits systems with fewer, less accessible active centers, potentially by promoting faster and more uniform activation of the Ti-O bonds. For manufacturers weighing energy costs against product quality, the ability to reach high molecular weights quickly at moderate power inputs could prove decisive.

The broader significance of the work lies in its convergence of several green chemistry principles into a single, practical platform. The monomer, ε-caprolactone, derives from a ring-strained cyclic ester that polymerizes without releasing small molecules, making the process atom-economical. The initiator is based on titanium, an abundant and comparatively harmless metal. The reaction proceeds in bulk, with no solvent, at a moderate 130 degrees Celsius, and can be accelerated further by microwave energy rather than prolonged heating. Each of these choices independently reduces the environmental footprint of PCL production; combined, they point toward a manufacturing route that could compete with conventional processes on cost while outperforming them on sustainability metrics.

There remain challenges ahead. The concentration dependence of the kinetics means that process designers must carefully balance initiator loading against molecular weight targets, since the macroinitiator chain length and the density of active centers pull in opposite directions. Understanding how residual titanium content affects the properties and biocompatibility of the final polymer will also be essential for medical applications. Nevertheless, by coupling rigorous non-isothermal kinetic analysis with demonstration-scale synthesis, the Thai team has provided exactly the kind of quantitative foundation that translates laboratory chemistry into industrial practice. As demand for biodegradable polyesters continues to climb amid global pressure on plastic waste, solvent-free titanium-catalyzed routes to PCL may well move from the pages of Polymer Bulletin into the factories of the circular economy.

Subject of Research: Solvent-free ring-opening polymerization of ε-caprolactone using titanium(IV) macroinitiators to produce biodegradable polycaprolactone

Article Title: Development of new titanium(IV)-macroinitiators towards the green and facile ring-opening polymerization of ε-caprolactone

Article References: Funfuenha, W., Cheechana, N., Meepowpan, P., Punyodom, W., & Limwanich, W. (2026). Development of new titanium(IV)-macroinitiators towards the green and facile ring-opening polymerization of ε-caprolactone. Polymer Bulletin, 83(12), Article 645. https://doi.org/10.1007/s00289-026-06707-9

Image Credits: AI Generated

DOI: 10.1007/s00289-026-06707-9

Keywords: polycaprolactone, ring-opening polymerization, titanium(IV) macroinitiator, epsilon-caprolactone, biodegradable polyester, solvent-free synthesis, microwave-assisted polymerization, DSC kinetics, coordination-insertion mechanism, green chemistry, activation energy, polymer bulletin