High Diffusion Research Articles

Methodology for optimally designing hydrogen refueling station barriers using RSM and ANN: Considering explosion and jet fire

Hydrogen is gaining attention as a sustainable energy source with the potential to replace fossil fuels. Due to its high diffusivity and wide flammability range, hydrogen can easily ignite with minimal electrical energy, leading to explosion and fires with minimal friction. Effective blast walls can restrict the dispersion of hydrogen, reducing the explosion overpressure due to delayed ignition. In addition, firewalls can improve safety by minimizing the impact behind the walls, thereby reducing the radiant heat caused by jet fires. This study proposes to optimize the distance between leak sources and barriers, as well as the height and width of barriers, to address explosion overpressure and radiation heat at hydrogen refueling stations (HRS). The optimization was carried out using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) and validated by simulations. This study confirms the feasibility of the barrier design at HRS and contributes to the improvement of safety.

Structural Engineering of Prussian Blue Analogues Enabling All-Climate and Ultralong Cycling Sodium-Ion Batteries.

The development of cost-efficient, long-lifespan, and all-climate sodium-ion batteries is of great importance for advancing large-scale energy storage but is plagued by the lack of suitable cathode materials. Here, we report low-cost Na-rich Mn-based Prussian blue analogues with superior rate capability and ultralong cycling stability over 10,000 cycles via structural optimization with electrochemically inert Ni atoms. Their thermal stability, all-climate properties, and potential in full cells are investigated in detail. Multiple in situ characterizations reveal that the outstanding performances benefit from their highly reversible three-phase transformations and trimetal (Mn-Ni-Fe) synergistic effects. In addition, a high sodium diffusion coefficient and a low volume distortion of 2.3% are observed through in situ transmission electron microscopy and first-principles calculations. Our results provide insights into the structural engineering of Prussian blue analogues for advanced sodium-ion batteries in large-scale energy storage applications.

PNIPAM-based ionic hydrogels for enhanced privacy smart windows and flexible sensor

The thermochromic materials are widely used in the smart window field because they can efficiently regulate solar radiation with temperature changes. Currently, most smart windows switch back and forth between opaque and transparent states to control solar radiation, which is very disadvantageous for the visibility of enclosed environments. Herein, in a binary solvent of ethylene glycol-water (EW), we are developing a series of thermoresponsive ion hydrogels suitable for smart windows by in-situ free radical polymerization of the thermoresponsive monomer N-isopropylacrylamide (NIPAM) and ionic monomers (amphiphilic, anionic, cationic). These smart windows exhibit excellent one-way transparency for privacy protection, allowing observation from a relatively dark private space to a public space outside the smart window during the day, while preventing a view from the relatively bright public space into the private space. Furthermore, these hydrogels demonstrate efficient blocking of ultraviolet / near-infrared radiation, low temperature resistance (∼ −40 °C), wide temperature range thermal responsiveness (∼ −25–60 °C), enabling effective regulation of solar heat radiation. Additionally, the anionic-NIPAM complex hydrogel possesses a high diffusion coefficient of water and excellent conductivity of 13.38 mS cm−1, which can be expanded its application in the field of flexible ion-conductive sensors.

Layered Bismuth Selenide with a Kinetics‐Enhanced Iodine Doping Strategy Toward High‐Performance Aqueous Potassium‐Ion Storage

AbstractAqueous potassium‐ion batteries with inherent safety, high abundance, and competitive hydrated ion‐radius point to future availability in energy storage. However, the extensively studied electrodes (metal‐oxides, Prussian‐blue‐analogues, etc.) typically suffer from undesirable capacities and sluggish kinetics owing to overwhelming ion diffusion barriers. Herein, for the first time, the metal chalcogenide bismuth selenide reinforced by iodine‐doping (I‐Bi2Se3) is implemented for high‐performance aqueous potassium‐ion storage. The co‐intercalation mechanism of potassium‐ion with proton in I‐Bi2Se3 is entirely revealed by operando synchrotron X‐ray diffraction and substantial ex‐situ analysis, and the excellent interlayer diffusion kinetics in the high‐conductive host are further enhanced by iodine‐doping, as proposed by theoretic calculations. Therefore, the resulting high diffusion coefficient and low interfacial transfer resistance endow I‐Bi2Se3 with superior rate performance (109.2 mAh g−1 at 10 A g−1) and cycling stability (91% capacity retention after 1200 cycles). Employing in hybrid‐ion batteries matching zinc metal, the highest reversible aqueous potassium‐ion storage to date of 316.8 mAh g−1 is demonstrated, permitting the establishment of reliable performance pouch cells. The promising aqueous potassium intercalation chemistry built in the improved metal chalcogenide is proven to be extendable to other hybrid‐ion devices, offering novel mechanistic insights and material practices for aqueous energy storage.

Contribution of Sc doping to the growth and adhesion of alumina scale on AlCoCrFeNi high-entropy alloy

Equimolar AlCoCrFeNi high-entropy alloy (HEA) often experiences serious oxidation degradation despite its superior mechanical properties at elevated temperatures. Herein, we reveal that minor Sc addition can enhance the oxidation resistance of AlCoCrFeNi HEA at 1100 °C, and the microstructure and oxidation properties for (AlCoCrFeNi)100−xScx HEAs (Sc-0, Sc-0.1, Sc-0.5 and Sc-1) are evaluated. Except for the original A2 + B2 phases, the Laves phase is found with increasing Sc addition. Moderate Sc addition is beneficial for interface adhesion by lowering the driving force for scale spallation and enhancing the interface toughness, and excessive Sc addition, however, results in serious internal oxidation due to the generation of Sc2O3 stringers as the high diffusivity paths for inward O ions. It is also proved that enhancing the interface toughness is more beneficial to improve the oxidation resistance compared to reducing scale growth rate. Our results can offer guidance for designing advanced alloys with excellent oxidation resistance.

LiF-Rich Alloy-Doped SEI Enabling Ultra-Stable and High-Rate Li Metal Anode.

Li metal is regarded as the "Holy Grail" in the next generation of anode materials due to its high theoretical capacity and low redox potential. However, sluggish Li ions interfacial transport kinetics and uncontrollable Li dendrites growth limit practical application of the energy storage system in high-power device. Herein, separators are modified by the addition of a coating, which spontaneously grafts onto the Li anode interface for in situ lithiation. The resultant alloy possessing of strong electron-donating property promotes the decomposition of lithium bistrifluoromethane sulfonimide in the electrolyte to form a LiF-rich alloy-doped solid electrolyte interface (SEI) layer. High ionic alloy solid solution diffusivity and electric field dispersion modulation accelerate Li ions transport and uniform stripping/plating, resulting in a high-power dendrite-free Li metal anode interface. Surprisingly, the formulated SEI layer achieves an ultra-long cycle life of over 8000 h (20,000 cycles) for symmetric cells at a current density of 10 mA cm-2. It also ensures that the NCM(811)//PP@Au//Li full cell at ultra-high currents (40 C) completes the charging/discharging process in only 68 s to provide high capacity of 151 mAh g-1. The results confirm that this scalable strategy has great development potential in realizing high power dendrite-free Li metal anode.

LiF‐Rich Alloy‐Doped SEI Enabling Ultra‐Stable and High‐Rate Li Metal Anode

AbstractLi metal is regarded as the “Holy Grail” in the next generation of anode materials due to its high theoretical capacity and low redox potential. However, sluggish Li ions interfacial transport kinetics and uncontrollable Li dendrites growth limit practical application of the energy storage system in high‐power device. Herein, separators are modified by the addition of a coating, which spontaneously grafts onto the Li anode interface for in situ lithiation. The resultant alloy possessing of strong electron‐donating property promotes the decomposition of lithium bistrifluoromethane sulfonimide in the electrolyte to form a LiF‐rich alloy‐doped solid electrolyte interface (SEI) layer. High ionic alloy solid solution diffusivity and electric field dispersion modulation accelerate Li ions transport and uniform stripping/plating, resulting in a high‐power dendrite‐free Li metal anode interface. Surprisingly, the formulated SEI layer achieves an ultra‐long cycle life of over 8000 h (20,000 cycles) for symmetric cells at a current density of 10 mA cm−2. It also ensures that the NCM(811)//PP@Au//Li full cell at ultra‐high currents (40 C) completes the charging/discharging process in only 68 s to provide high capacity of 151 mAh g−1. The results confirm that this scalable strategy has great development potential in realizing high power dendrite‐free Li metal anode.

Facile construction of porous carbon fibers from coal pitch for Li-S batteries

Coal pitch, an important by-product in the coal coking industry with a high output, is a low-cost and high-carbon yield precursor for the manufacturing of high-value carbon materials. Herein, N/O co-doped carbon fiber (CFCP), fabricated by electrospinning using pre-oxidized coal pitch as the precursor, was employed as the sulfur host for Li-S batteries. The presence of more pyrrolic N and graphic N in CFCP than carbon fiber made from polyacrylonitrile benefits the adsorption of lithium polysulfide and the battery’s life. Sulphur-CFCP cathode (S@CFCP) exhibited excellent specific capacity and cyclability, with a specific capacity of 701.1 mAh/g and a low capacity decay rate of 0.088% per cycle over 200 cycles at 2.0 C, respectively. The high ion diffusion rate, low charge transfer resistance, and effective conversion of lithium polysulfides enable the high electrochemical performance of S@CFCP.

Impurity transport study based on measurement of visible wavelength high-n charge exchange transitions at W7-X

A recently installed high-speed charge exchange diagnostic at the W7-X stellarator has been used to identify several high-n Rydberg emission lines near 500 nm following impurity injections. The wavelengths of observed high-n Rydberg transitions are independent of the impurity species and originate from ions with ionization states ranging from 14+ to 45+ suggesting that this approach can be applied to a variety of heavy impurities. Moreover, little to no passive signal is observed since the high-n energy levels are unlikely to be populated by electron impact excitation. The combination of the newly developed diagnostic and the observation of high-n Rydberg states provides spatially resolved, high-speed measurements of multiple charge states which are analyzed in a Bayesian inference framework to determine both impurity diffusion and convection profiles. Measurements from the 2023 experimental campaign conclusively show high diffusion and an inward pinch in the core, well above predictions by neoclassical theory.

Surface topography and corrosion resistance of AISI 630 stainless steel after finish turning under different cooling methods

AISI 630 stainless steel (SS) is widely used for medical devices. This paper describes the effects of dry, flood and minimum quantity lubrication (MQL) machining conditions on the surface topography and corrosion resistance (CR) of AISI 630 SS after finish turning. Small areas of valleys and large areas of peaks were observed on the surfaces with minimum surface roughness (SRmin) after dry machining at the feed rate (f) of 0.1 mm/rev and at the f = 0.14 mm/rev using the MQL method. Only small areas of peaks were observed after flood machining at the f = 0.1 mm/rev. Regardless of cooling methods, regularly distributed deep valleys and high peaks were observed on the surfaces with maximum surface roughness (SRmax) machined at the f = 0.35 mm/rev. Surfaces of the samples with SRmin and SRmax under flood machining and with SRmax under MQL machining had high oxygen content in the range of ∼ (20−30) %wt. during 7–72 days of the sample storage in SBF. Such an oxygen content is observed on the machined surfaces for which maximum peak height Sp parameters were in the range of ∼ (10–16) μm and maximum valley height Sv – ∼ (8–10) μm. Compared to SRmin, high ion diffusion was observed on surfaces with SRmax. This means that surfaces with regular deep valleys and high peaks provide high ion mobility between them. In addition, compared to dry and MQL machining, higher resistivity was obtained for the samples under flood machining. Depending on the industrial application requirements, the passivity and CR of AISI 630 SS can be modulated by selecting machining conditions and surface topography. It has been established that in order to achieve favorable CR of the AISI 630 SS surface after finish turning, the flood method is recommended.

Hydration of mafic crustal rocks at high temperature during brittle‐viscous deformation along a strike‐slip plate boundary

AbstractThe Poroshiri ophiolite (Hidaka metamorphic belt, Japan) occurs within a crustal‐scale network of high‐temperature, dextral shear zones that accommodated hundreds of kilometres of displacement due to the opening of the Japan Sea in the Neogene. The opholitic rocks comprise ultramafic, mafic and sedimentary protoliths that have been variably hydrated and metamorphosed. This work investigates the mechanisms and timing of fluid influx relative to viscous deformation in metagabbros and amphibolites deformed during exhumation from granulite‐ to amphibolite‐facies conditions. We consider a range of microstructures, from low strain domains and 1–2 mm thick shear bands to mylonites with a thickness of a few meters. Low strain domains of metagabbros exhibit corona textures with symplectites consisting of pargasitic amphibole (Ed0.7) ‐ anorthitic plagioclase (An80–92) ± orthopyroxene ± clinopyroxene forming around olivine and igneous pyroxene and with similar plagioclase–amphibole‐orthopyroxene ± clinopyroxene granoblastic aggregates in micrometric‐thick fractures. These textures result from hydration under low fluid‐rock ratio, with elevated H2O content only occurring locally (H2O > 1–1.2 wt%). Igneous mineral replacement leads to grain size reduction from 1 mm to ~10 μm. Amphibole exhibits a strong core‐rim zonation primarily controlled by the high diffusivity of Fe, Mg and OH and the low diffusivity of Al. Mineral compositional equilibrium is achieved at the scale of 100–200 μm. In mm‐thick localized shear bands and in metric‐scale mylonitic amphibolites, the heterogeneous mineral composition of amphibole (Ed0.2–0.5) and plagioclase (An40−An80) indicates only partial re‐equilibration (at the scale of 200–500 μm) despite higher fluid‐rock ratios and more pervasive fluid percolation than in metagabbros. Plagioclase–amphibole thermometry and equilibrium phase diagrams indicate that the initial fluid infiltration and corona formation occurred at 800–850°C by fracturing and percolation along grain boundaries. This was followed by the main fluid percolation and mylonitization event, which occurred during exhumation and cooling at conditions of 720–580°C, ~4 kbar. Continuous hydration during retrogression was achieved by the influx of dominantly seawater‐derived fluid, as attested by the high chlorine (Cl) contents (>300–400 ppm) of amphiboles in fractures. The heterogeneous distribution of fractures controls the distribution of fluid from the earliest stages of hydration, creating positive feedback where the growth of hydrous minerals as amphibole (up to +300 vol% of amphibole in high strain areas relative to the low‐strain ones) and the formation of fine‐grained mixed domains that led to further localization of viscous strain and mass transfer (variations of ± 30–40% in major elements). The Poroshiri ophiolite therefore represents a good fossil example of a former transpressional plate boundary where coupled metamorphic and deformation processes were triggered by seawater‐derived fluid that percolated to depths of ~15 km.

A comprehensive investigation on industrial radio frequency (RF) drying: Modeling and optimization strategies for carrot slice processing

Radiofrequency (RF) drying is a revolutionary technique gaining prominence in the food industry. The present study delves into the drying of carrot slices within industrial settings, employing cutting-edge RF technology. The entire drying operation was optimized using response surface methodology, and the effect of process parameters on the physico-chemical properties of carrot slices was noted. Optimized process parameters were found to be at the initial moisture content of 89.86% with an electrode distance of 210 mm and a thickness of carrot slice at 4.75 mm. Page model was found to be most suitable as it explains most of the variations in the moisture ratio. High moisture diffusivity was noted for RF-treated samples which indicates faster drying rates. This project on optimizing and modeling carrot slice drying in industrial RF systems holds immense industrial relevance, promising increased efficiency, improved product quality, and sustainable practices in vegetable processing.

Hierarchically porous and single Zn atom-embedded carbon molecular sieves for H2 separations

Hierarchically porous materials containing sub-nm ultramicropores with molecular sieving abilities and microcavities with high gas diffusivity may realize energy-efficient membranes for gas separations. However, rationally designing and constructing such pores into large-area membranes enabling efficient H2 separations remains challenging. Here, we report the synthesis and utilization of hybrid carbon molecular sieve membranes with well-controlled nano- and micro-pores and single zinc atoms and clusters well-dispersed inside the nanopores via the carbonization of supramolecular mixed matrix materials containing amorphous and crystalline zeolitic imidazolate frameworks. Carbonization temperature is used to fine-tune pore sizes, achieving ultrahigh selectivity for H2/CO2 (130), H2/CH4 (2900), H2/N2 (880), and H2/C2H6 (7900) with stability against water vapor and physical aging during a continuous 120-h test.

Dynamics of reaction–diffusion–advection system and its impact on river ecology in the presence of spatial heterogeneity

This study considers a two-species reaction–diffusion–advection (RDA) model in a heterogeneous advective environment with zero Neumann boundary conditions. We suppose that two species compete for the same food resource but have different diffusion and advection rates. The primary objective of this study is to investigate the global asymptotic stability and coexistence of steady state based on different and unequal diffusion and advection rates through theoretical and numerical analysis. We establish the local stability of two semi-trivial steady states of the competing species. Also, the non-existence of coexistence steady state is proved with the help of some non-trivial assumptions. Finally, we show the global stability with the help of monotone dynamical systems and combine the local stability and non-existence of coexistence steady state. If one species adopts a smaller diffusion and advection rate, the competition’s result depends on the advection and diffusion rate ratio. If the ratio is smaller, then the species will prevail. Also, the species with higher diffusion and smaller advection will win. Lastly, the effectiveness of the model in one and two-dimensional situations is shown by a series of numerical calculations, which is particularly important for environmental consideration.

The role of Sn grain orientation in Cu depletion of Sn-based solders

The miniaturization of solder bumps in flip-chip packages results in large variability in their microstructure making the prediction of joint lifetime challenging. This is of particular importance in Sn-rich solders due to the anisotropic diffusion behavior of Sn and the presence of fast diffusion pathways, such as grain boundaries and twins that vary from joint to joint. We developed a multi-physics phase-field model to predict the electromigration-enhanced evolution of intermetallic compounds in Cu/Sn system with different grain structures. We present simulations of solder joints with polycrystalline Sn with grains with different orientations to observe the effect of Sn anisotropy and grain boundaries on electromigration failure. The simulations predict Cu depletion in the cathode and the formation and accumulation of intermetallic compounds along Sn grain boundaries dependent on the Sn grain orientation. Additionally, Cu6Sn5 clusters are formed in the Sn matrix when high diffusion rates at the interfaces are considered.

Quantifying the effects of inlet gas and collision models in direct metal deposition using a CFD-DEM approach

Simulations of the powder jet in direct metal deposition (DMD) are often made with significant simplifications such as being incompressible, steady-state, or single-component, and do not provide explanation for the choice of parameters in the collision model. This work presents a coupled Computational Fluid Dynamics–Discrete Element Method model for the powder jet in DMD that considers all of the following features: compressibility effects, particle–wall and particle–particle collisions, turbulence, gas mixing, and melt pool boundaries. The goal of the simulation is to optimize the operating conditions and to predict the outcomes of experiments. After effective validation against experimental results, the effects of inlet gas, collision models and different boundary conditions in DMD have been comprehensively studied. It is demonstrated that gases with higher diffusivities, such as helium, are less effective shielding gases than those with lower diffusivities, such as argon. The increased wall temperature arising from the melt pool and track has little influence on the particle distribution.

Effect of sintering temperature and doping content on phase evolution and microstructure of doped UO2 ceramics

ZrO2-doped UO2 ceramics have been considered as a promising high performance nuclear fuel in LWR due to its desirable properties. ZrO2-doped UO2 ceramic fuel samples with different contents of ZrO2 (20 wt%, 25 wt% and 30 wt% ZrO2, equivalent to 35.4 mol%, 42.3 mol% and 48.4 mol%, respectively) were prepared by pressureless sintering at various temperatures (1550 ℃, 1650 ℃ and 1750℃, respectively) for 4 h in a hydrogen reducing environment. Phase evolution and microstructure of as-sintered ZrO2-doped UO2 ceramic samples were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. Results show that there exists coexistence of uranium-rich U1-xZrxO2 phase with face-centered cubic (FCC) structure and zirconium-rich Zr1-yUyO2 phase with tetragonal structure in the 20 wt% ZrO2-doped UO2 ceramic sample when the sintering temperature is lower than 1650 ℃, while the UO2 and ZrO2 will form a single U1-xZrxO2 solid solution after sintering at 1750℃ for 4 h with the ZrO2-doped UO2 ceramic samples containing 25 or 30 wt% ZrO2, respectively. The significant differences of phase structure and ionic radius between ZrO2 and UO2 and the high atomic diffusion barrier are the main reasons that it is difficult to form a single solid solution for UO2-ZrO2 ceramic samples sintered at low temperature.

Boosting Interfacial Electron Transfer and CO2 Enrichment on ZIF-8/ZnTe for Selective Photoelectrochemical Reduction of CO2 to CO.

Artificial photosynthesis is an effective way of converting CO2 into fuel and high value-added chemicals. However, the sluggish interfacial electron transfer and adsorption of CO2 at the catalyst surface strongly hamper the activity and selectivity of CO2 reduction. Here, we report a photocathode attaching zeolitic imidazolate framework-8 (ZIF-8) onto a ZnTe surface to mimic an aquatic leaf featuring stoma and chlorophyll for efficient photoelectrochemical conversion of CO2 into CO. ZIF-8 possessing high CO2 adsorption capacity and diffusivity has been selected to enrich CO2 into nanocages and provide a large number of catalytic active sites. ZnTe with high light-absorption capacity serves as a light-absorbing layer. CO2 molecules are collected in large nanocages of ZIF-8 and delivered to the ZnTe surface. As evidenced by scanning electrochemical microscopy, the interface can effectively boost interfacial electron transfer kinetics. The ZIF-8/ZnTe photocathode with unsaturated Zn-Nx sites exhibits a high Faradaic efficiency for CO production of 92.9% and a large photocurrent of 6.67 mA·cm-2 at -2.48 V (vs Fc/Fc+) in a nonaqueous electrolyte at AM 1.5G solar irradiation (100 mW·cm-2).

Inducing and Understanding Pseudocapacitive Behavior in an Electrophoretically Deposited Lithium Iron Phosphate Li-Metal Battery as an Electrochemical Test Platform.

Our study has effectively employed electrophoretic deposition (EPD) using AC voltage to develop a lithium iron phosphate (LFP) Li-ion battery featuring pseudocapacitive properties and improved high C-rate performance. This method has significantly improved the battery's specific capacity, achieving an impressive 100 mAhg-1 at a 5 C discharge rate, which showcases its superior high-rate capability. Additionally, the battery displayed excellent reversibility during its performance cycles. These results confirm the EPD method's efficacy in improving LFP electrode performance, yielding notable improvements in cycling stability and high-rate capability. The enhanced capacity and high-rate performance of the electrophoretic-deposited LFP electrodes are largely due to the fast kinetics facilitated by pseudocapacitive behavior-induced charge storage and a high Li-ion diffusion constant measured in our EPD-deposited LFP electrodes. This underscores the practicality of our approach and the development of a fundamental test platform to investigate the pseudocapacitive charge storage mechanism in electrodes with typical battery-like behavior.

Li1.5Al0.5Zr1.5(PO4)3-coated Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials with high lithium-ion diffusion rate and long cycling stability for lithium-ion batteries

Li1.5Al0.5Zr1.5(PO4)3-coated Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials with high lithium-ion diffusion rate and long cycling stability for lithium-ion batteries