Cracks In Layer Research Articles

Characterization of nickel cladding on type 316H stainless steel for enhanced corrosion resistance in molten chloride salts

This study explores the corrosion protection characteristics of nickel (Ni) cladding on Type 316H stainless steel in molten chloride salt environments, relevant to molten salt reactors (MSRs) which are gaining interest as advanced and sustainable nuclear energy sources. Type 316H stainless steel, while noted for its high-temperature strength and corrosion resistance, faces significant challenges when exposed to corrosive molten salts. To address this, Ni cladding was applied using gas tungsten arc (GTA) welding and directed energy deposition (DED) laser cladding. Characterization of the cladding layers was performed using field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS), identifying precipitates such as Ti(C,N) and Cr₂O₃. Mechanical integrity was verified through bending tests in accordance with ASTM E190-21, which revealed no cracks in the cladding layers. Corrosion resistance was assessed through immersion tests in a 57 mol% NaCl - 43 mol% MgCl₂ mixture at 650 °C for 502 h. Results demonstrated superior corrosion resistance of Ni-clad specimens compared to uncoated Type 316H stainless steel and Incoloy 800H, with the Ni cladding exhibiting a weight increase due to Fe deposition from the Fe-base alloys. The study concludes that Ni cladding, irrespective of the application method, enhances the durability and longevity of Type 316H stainless steel in the harsh environments typical of MSRs, suggesting a promising approach to improving the performance of structural materials in these systems.

Dynamic behaviors of interfacial oxides and elements during the ultrasonic-assisted diffusion bonding of 6063Al alloys

Efficiently breaking the oxide layer and rapidly diffusing of elements at low-temperature has been a longstanding goal in the diffusion bonding (DB) of Al alloys. To break the interfacial oxide layers and accelerate atomic diffusion, ultrasound energy was introduced during the DB of 6063Al. A full Zn–Al eutectoid joint was manufactured via a pure Zn interlayer at 360 °C in atmospheric by an ultrasonic-assisted diffusion bonding (U-DB) at only an ultrasonic vibration of10 min. During U-DB, brittle cracks were formed in the interfacial oxide layers due to high strain rate induced by ultrasonic action. Zn diffused into Al alloy through the brittle cracks in oxide layers via “subcutaneous diffusion,” forming a Zn–Al eutectoid diffusion region between the Al alloy and oxide layer. The oxide fragments irregularly migrated to the center of the joint due to Kirkendall effect and ultrasonic action, finally dispersed in the bonded metal. The bonded metal finally transformed as a full Zn–Al eutectoid phase after consuming interlayer. The shear strength of the Zn–Al eutectoid joint reached 82.6 MPa. The Zn–Al mutual diffusion coefficient of U-DB at 360 °C was ∼0.6 μm2/s, which was about 20 times higher than the thermal diffusion coefficient under same temperature condition. Additionally, the mechanism of ultrasonic-assisted diffusion based on the strain-driven diffusion mode was discussed in detail.

Modeling of the damage and fracture behaviors of a SiC triplex tube during the burst test with elastomeric insert

The Silicon Carbide (SiC) triplex cladding tube has been regarded as one of the leading structures for the next-generation light water reactors, because of its larger safety margins under beyond-design basis transient conditions. In this study, a numerical simulation method is developed to reproduce the damage and fracture behaviors of a nuclear-grade SiC triplex cladding tube during the burst test. Especially, a three-dimensional continuum damage mechanics based (CDM-based) constitutive model is developed and validated for the SiCf/SiC composites, with the predictions agreeing well with the experimental data under different loading conditions. By introducing cohesive surfaces in the monolithic layers of a SiC triplex tube, cracking of the monolithic layers and the subsequent local damage behaviors within the SiCf/SiC composite layer are captured. The local tensile strength of ∼402 MPa is identified for the monolithic layers, corresponding to the first load drop during the burst test. The simulation results indicate that cracking of the monolithic layers leads to sharp increases in the locally enhanced hoop stresses and damage factors for the SiCf/SiC composite layer, with slight influences on the field variables far away from the main crack; after the fast increase the evolution velocity of local damage factors slows down, reflecting the toughening effects of SiCf/SiC composite. An assessment strategy for the gas leak tightness and structural integrity of the SiC triplex cladding during the accident sceneries is proposed to predict failure of the SiCf/SiC composites with the critical damage factor, and it is necessary to simulate the damage and fracture behaviors in the multi-layer models with the cracking process of monolithic layers involved.

Effect of microstructure variation induced by processing on corrosion behavior of Zr-Sn-Nb alloy

In order to investigate the effect of microstructure variation induced by processing on corrosion behavior of zirconium alloys, Zr-Sn-Nb alloy original plates were processed by rolling and annealing, and the microstructure and corrosion behavior of both original plates and processed plates were analyzed. It was found that after the original plates were processed, the recrystallized microstructure in original plates was transformed to stress-relieved microstructure in processed plates, with second phase particles ripening. When exposed to pure water and water containing H3BO3 and LiOH, the original plates have better corrosion property than the processed plates, and the corrosion transition of the processed plates happened earlier than that of the original plates. The grain structure differences of original plates and processed plates have two aspects of influence on oxide cracking and corrosion transition. Firstly, there were more defects in processed plates which results in smaller grains and larger grain boundary areas in oxide. Secondly, the strength of processed plates is higher, and this will lead to less stress accommodation of the growing oxide by plastic deformation of the matrix, and higher stress in oxide layer formed during the corrosion process. Both factors caused more cracks in the oxide layer of processed plates, leading to earlier corrosion transition and decreasing corrosion property. Second phase particles and their surroundings are susceptible to cracks during corrosion process, and may become the original source of cracks. However, second phase particle ripening was not closely related to decreasing corrosion property of processed plates.

Aircraft deicing based on large vibration of wings

Since aircraft icing will decrease the ability of aircraft to generate lift, it is significant to consider the aircraft deicing problem. The paper presents an aircraft deicing method based on the cracking of the ice layer caused by the large deformations of wings. To describe the deformation of wings, the absolute coordinate-based formulation is used. The aircraft with high aspect ratio wings is simplified as a hub-beam system. Such a rigid-flexible system with the fast rotation speed of hub and the large deformation of the beam is modeled using absolute coordinate-based formulation accurately. The maneuver of the rigid body will lead to the large deformation of wings to do the de-icing. Numerical examples are presented to reveal that the maximum tensile strength on the wing surface with sinusoidal control torques with some amplitudes and frequencies is larger than the ice’s tensile strength. Hence, the proposed de-icing method based on the aircraft maneuvering is potential.

Study on the restoration of glass slides dating back to the 1940s

The Museum of Sun Yat-sen University houses a collection of antique glass slides dating back to the 1940s. These historical artifacts not only serve as a record of the past but also bring history to life. During extended storage, the emulsion layer on glass slides may harden and become brittle, leading to cracking and buckling. This study suggests a method to enhance the physical property of the emulsion layer by using a combination of nonionic surfactant isomeric alcohol ethoxylates eight (TO-8) and waterborne epoxy resin (WER). We investigated the microscopic action mechanism of the two on the emulsion layer of glass slides using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), water contact angles, and other techniques. Our study revealed that TO-8 can significantly eliminate the spherulitic crystal structure of the emulsion layer, as well as improve its softness and hydrophilicity. The addition of the WER ensures that the cracking and warping of the emulsion layer film is fully corrected, resulting in a flat surface. Additionally, the size of the emulsion layer film remains stable even after wetting. The WER has minimal impact on the image information of glass slides. The emulsion layer of the glass slides, restored using the softening protection solutions developed in this study, showed almost full recovery of image information. This research holds significant theoretical and practical value for repairing cracked and warped emulsion layers on glass slides.

Influence of surface state on interface bonding strength of Al/Ta laminated composite via differential temperature rolling

Al/Ta laminated composite is one of the promising space radiation shielding materials. However, due to significant differences in the properties of Al and Ta alloys, the interface bonding strength of rolled Al/Ta laminated composites is weak. In this study, we prepared 2A12 Al/Ta-2.5W laminated composite using differential temperature rolling method. The influence of surface state on the interface microstructure and interface bonding strength were systematically analyzed, and the interface bonding mechanism of Al/Ta laminated composite was revealed. It is found that 2A12 Al and Ta-2.5W alloys are successfully bonded via differential temperature rolling within rolling temperature range of 350∼450 °C and rolling reduction range of 40 %–50 % when the hardening degree of Ta-2.5W surface layer exceeds 25 %, and the roughness of Ta-2.5W and 2A12 Al surface is greater than 4.5 μm and 3.6 μm, respectively. It is demonstrated that increasing the hardening degree and roughness at Ta-2.5W surface, while decreasing the hardening degree and increasing roughness at 2A12 Al surface can facilitate cracking of the surface layer at Ta-2.5W side and the embedding of virgin Al metal into the cracks during rolling, which can promote the interface bonding process between 2A12 Al and Ta-2.5W alloys. The highest interfacial bonding strength of Al/Ta laminated composite can reach 41.2 MPa. However, when the surface layer at Ta-2.5W side is excessively hardened and the hardness reaches two times of the substrate, thick fragments could be generated at the interface, which have detrimental effect on the interface bonding strength and the value decreases to 23.05 MPa. In terms of the effects of rolling temperature and rolling reduction, it is found that the oxide film and hardening layer on the Ta-2.5W surface are more sufficiently ruptured, and more virgin 2A12 Al metals are embedded in the cracks at the surface of Ta-2.5W at higher rolling temperature and higher rolling reduction conditions, thereby leading to the increased interface bonding strength. This study provides theoretical basis for the preparation of Al/Ta laminated composites and sheds light on the relationship between surface state and interface bonding strength of laminated metal composites.

Wet oxidation behavior of Al-Y synergistic modified liquid phase sintered SiC

The wet oxidation behavior of LPS-SiC ceramics as well as the synergistic modification effect of Al2O3 and Y2O3 as sintering aids are investigated. The results show that SiO2 oxide scale is transformed to aluminosilicate with the addition of Al2O3, which can inhibit the crystallization of oxide layer and formation of cracks. The aluminosilicate oxide layers have low kl value close to zero, which can reduce the consumption of protective oxide layer under water-containing atmosphere. Y2O3 are mainly transformed to Y2Si2O7 to resist the diffusion of oxidative gas. However, with the increase of sintering aids content, the aluminosilicate layer with excessive viscosity limits the emission of gas generated by oxidation and causes many bubbles left in oxide scale which provided rapid channel for oxidative gas. Therefore, LPS-SiC with lower content of sintering aids has better oxidation resistance. This work can provide guidance for the component design of SiC-based ceramics and composites.

High-temperature oxidation behavior and mechanical properties of PS-PVD sprayed Yb2Si2O7 environmental barrier coatings

The high-temperature oxidation behavior and mechanical properties of the Yb2Si2O7/Si environmental barrier coatings (EBCs) prepared by plasma spray-physical vapor deposition at 1250 °C and 1350 °C were investigated, and obvious delamination was observed after oxidation for 4000 h. The results showed that element diffusion occurred during oxidation, and the diffusion of oxygen led to the formation of thermal growth oxides (TGO), which induced pores and microcracks. The TGO played a role in hindering element diffusion, but the mismatching coefficients of thermal expansion and phase transition caused vertical and transverse cracks in the TGO layer. These cracks became channels for oxygen diffusion and ultimately resulted in delamination between TGO and the bonding coating (BC) layer. Furthermore, temperature significantly affects the oxidation kinetics of EBCs, and the oxidation within the BC layer alters its elastic modulus. The elastic modulus of the BC layer first increased and then decreased. The oxidation damage was more pronounced at 1350 °C.

A CO-HSDT isogeometric analysis for free vibration of matrix cracked FG-GPLRC plates coupled with stationary fluid

This paper for the first time proposes an efficiently C0-higer order shear deformation theory (HSDT) and isogeometric analysis (IGA) for the free vibration analysis of matrix cracked functionally graphene nanoplatelets reinforced composite (FG-GPLRC) plate coupled with stationary fluid. This case represents essential components of sophisticated structures utilized in industries such as shipbuilding, nuclear, marine, and naval. The properties of the four GPLs distributions of FG-GPLRC are evaluated by using a combination of the modified Halpin-Tsai micromechanics model and the rule of mixtures, while the degraded stiffness of cracked layers is predicted by the self-consistent micromechanical (SCM) model. The fluid is assumed to be homogeneous, inviscid, incompressible and irrotational, so the free-surface waves and hydrostatic pressure effects on structures are neglected. The governing equation of motion is derived by the Hamilton's principle, where three different fluid-plate interaction systems are taken into consideration. After validating the proposed method against existing literature, the effect of various parameters such as crack density, interaction boundary conditions (IBC), fluid level, GPLs distribution pattern, total number of layers, and geometric parameter on the free vibration of matrix cracked FG-GPLRC plate are investigated. It is believed that the finding in this paper may be helpful for the accurate design and analysis of matrix cracked FG-GPLRC plate submerged in fluid.

Surface with wettability gradient — A novel approach for crystallization fouling control on the horizontal falling film flow

To manage scaling on heat transfer surfaces, using chemical-based antifouling treatments takes a toll on the environment, and related maintenance costs are significant. A unique and environmentally friendly scale mitigation strategy is developed in this work. By manipulating the scale layer distribution using surface wettability gradients, stronger flow shear and weaker scaling adhesion are achieved, facilitating self-cleaning process. Experimental work utilizes a horizontal-tube falling-film evaporator to mimic multiple-effect distillation process. A millimetric wettability pattern – alternating hydrophilic and hydrophobic regions – is created by coating stainless steel tubes. The results show scale layers (calcium carbonate) were either thicker in hydrophilic regions and thinner in hydrophobic regions or had approximately uniform thickness in both regions but cracks in scale layers near wettability boundaries. Scale layers wash-off with flow is observed on patterned tubes, demonstrating self-cleaning process. In contrast to persistent deterioration in overall HTC (heat transfer coefficient) for baseline tube (77 % of initial HTC after 192 h), HTC on patterned tubes initially increases due to surface wetting effects, then maintains roughly constant (15 % higher than that of baseline after 192 h) along with lower scale mass. This work provides a novel scaling control method, a potential “green” alternative to current industry scale-control practices.

Liquid-Phase Exfoliation of 3D Metal-Organic Frameworks into Nanosheets.

Traditionally, the acquisition of 2D materials involved the exfoliation of layered crystals. However, the anisotropic bonding arrangements within 3D crystals indicate they are mechanically reminiscent of 2D counterparts and could also be exfoliated into nanosheets. This report delineates the preparation of 2D nanosheets from six representative 3D metal-organic frameworks (MOFs) through liquid-phase exfoliation. Notably, the cleavage planes of exfoliated nanosheets align perpendicular to the direction of the minimum elastic modulus (Emin) within the pristine 3D frameworks. The findings suggest that the in-plane and out-of-plane bonding forces of the exfoliated nanosheets can be correlated with the maximum elastic modulus (Emax) and Emin of the 3D frameworks, respectively. Emax influences the ease of cleaving adjacent layers, while Emin governs the ability to resist cracking of layers. Hence, a combination of large Emax and small Emin indicates an efficient exfoliation process, and vice versa. The ratio of Emax/Emin, denoted as Amax/min, is adopted as a universal index to quantify the ease of mechanical exfoliation for 3D MOFs. This ratio, readily accessible through mechanical experiments and computation, serves as a valuable metric for selecting appropriate exfoliation methods to produce surfactant-free 2D nanosheets from various 3D materials.

Study of the dynamic impact spalling of ductile materials based on Gurson-type phase-field model

The formation of void damage and spalling failure in ductile metallic materials under strong impact is a well-established phenomenon. In aerospace and defense technology engineering design, understanding the spalling failure process and related mechanisms is of utmost importance. This paper develops an explicit Gurson-type phase-field model that can simulate the void evolution and spalling damage of three-dimensional ductile metallic materials under high-velocity impacts based on the study of Aldakheel et al.. The model incorporates the Gurson-type void evolution equation and the phase-field approach while taking into account the pressure-dependent bulk modulus and inertia effects. This model is used to study the main processes and mechanisms of impacted layer cracking of metals in different dimensions. Meanwhile based on the study of complex spallation cracking processes in metals in two and three dimensions, observing and proposing the formation mechanism of complex spallation cracking modes in materials due to lateral and edge (base angle) rarefied effects.

Peridynamics simulation of microparticle impact: Deformation, jetting, and the influence of surface oxide layer

Over the past decade, cold spraying (CS) has become a significant additive manufacturing technology for creating metallic structures and repairing damaged components. This study uses a novel peridynamic model to investigate the behavior of 12 μm copper particles impacting a copper substrate during CS deposition. The model examines deformation behavior, material jetting, and the effect of a native particle oxide layer. Two oxide thicknesses, 6 nm and 30 nm, were considered. The 6 nm oxide, typical for gas-atomized copper powders, had a negligible effect on deformation, while the 30 nm oxide showed a notable influence. For the 30 nm oxide, the experimentally observed coefficient of restitution (COR) deviated from theoretical predictions in the velocity range of 400–600 m/s due to cracking and fracturing of the oxide layer at higher impact velocities, reducing particle rebound velocity without sufficient metal-to-metal contact for permanent bonding. Permanent adhesion requires significant oxide fragmentation and separation. The study also identified threshold velocities for material jetting from the substrate and particle, showing that oxide presence delays particle jetting by impeding plastic deformation at the edges. Quantifying the oxide volume at the particle-substrate interface clarifies the effect of jetting on COR and bonding strength. The analysis includes effects of deflected jets at extremely high velocities (e.g., 870 m/s), compared with existing literature. Overall, the results demonstrate the efficacy of the peridynamics-based simulation in accurately representing material behavior during high-velocity impacts, effectively predicting oxide breakup, detachment, and removal in CS, and their effects on deposition characteristics.

Study on the dynamic fracture behavior of anisotropic CCNBD shale specimens under different impact angles

Drilling and fracturing are the key technologies for shale gas extraction, while most of the loads generated during rock drilling or fracturing are dynamic. In this study, dynamic impact experiments were conducted on the cracked chevron-notched Brazilian disc shale specimens with different chevron-notched crack (CNC) inclinations (β) and layer inclinations (α) by the split Hopkinson pressure bar. The results show that the dynamic peak load and dissipated energy increases with the increase of β, α, and strain rate, but their changing trends are different. The generation and expansion of cracks during the specimen failure process are mainly affected by β. As β increases, the failure type of the specimen can be divided into pure mode I fracture, mode I-II mixed fracture, pure mode II fracture, mixed tension-shear failure, and Brazilian splitting failure. The increase in strain rate will lead to a decrease in the time for crack initiation and propagation as well as an increase in secondary cracks. In addition, the mode I fracture toughness (KⅠC) and mode II fracture toughness (KⅡC) both grow with the increase of α and strain rate. The KⅡC predicted by the generalized maximum tangential stress criterion (GMST) exhibits more accurate.

High-temperature oxidation behavior of high entropy carbide (TaNbTiV)C in atmospheres with different oxygen contents

A high entropy carbide (TaNbTiV)C was fabricated via spark plasma sintering of high entropy powders that were prepared using a molten salt method. The as-fabricated high entropy carbide was then investigated for its high-temperature oxidation behavior at 850 °C, under atmospheres with three different oxygen contents (20 vol%, 40 vol%, and 60 vol%). After the high-temperature oxidation process, the main phases observed in all the specimens were incompletely oxidized phase (NbxTi1-x)CyO2-y and oxides (Nb0.5Ta0.5)2O5, TiO2, and Nb2O5. Importantly, the thickness of the oxide layer initially increased and then decreased as the oxygen content increased. When the oxygen content reached 40 vol%, the ceramic displayed severe oxidation behavior with observed thicker of the oxide layer, as well as numerous pores and cracks in the oxide layer. This work provides new insights into the oxidation behavior of high entropy carbides.

The concentration influence of multi-walled carbon nanotubes coating on fatigue edge crack growth and other mechanical properties of Al 7075-T6 thin plates

In the current study, the incline edge crack growth behavior in an aluminum alloy 7075-T6 specimens (which were coated using nickel-carbon nanotubes electroless coating) has been investigated undergoes uniaxial tensile fatigue loading. High purity multi walled carbon nanotubes have been used in nano-coating solutions with various concentrations (1 g/l, 2 g/l and 3 g/l) to examine the improvement extent of fatigue crack growth resistance and other mechanical properties. Water jet technique was used to cutting aluminum plates to the required dimensions before the nano-coating procedure. Multi-purpose fatigue apparatus has been adopted to apply tensile fatigue loading with zero stress ratios. High magnification camera with image j software has been utilized to measure the propagated crack lengths with the number of fatigue cycles. To inspection the quality, thickness uniformity and homogeneity of the nano-coating layer over specimen surfaces, EDXRF and FESEM techniques have been adopted in this study. Numerical simulation using ABAQUS 2021 programming was performed for the purpose of the results validation. The measured results offered a 25.9 %, 44.5 % and 47.9 % increasing in the hardness of the coated specimens using 1 g/l, 2 g/l and 3 g/l MWCNTs respectively. The modulus of elasticity produced an increasing of 26.7 %, 44.4 % and 46.3 % for the coated specimens using 1 g/l, 2 g/l and 3 g/l MWCNTs respectively. The nano-coating with 2 g/l MWCNTs produced more homogeneous, uniform thickness coating layer and fatigue crack growth resistance than that of the coated specimens using other concentrations of MWCNTs. The similarity in the crack growth behavior was the major outcome of the results validation from the fatigue tests and numerical simulation.

A Ceramic/Lithiophilic Metal Dual Protective Layer for Stable Lithium Metal Anodes Fabricated via Transfer-Printing Methods

Lithium metal has attracted researcher’s attention because of its superior theoretical capacity (3860mAh g-1 or 2061 mAh cm-3), which is nearly 10 times higher than commercialized anode materials, for example, graphite (372 mAh g-1). However, lithium metal is not currently used in commercial lithium metal batteries due to safety and efficiency issues that arise during long-term battery operation. The high reactivity of lithium metal causes almost all available electrolytes to be spontaneously reduced on the Li surface to form a solid-electrolyte interface (SEI) layer. Unfortunately, this passivating SEI layer is typically too fragile to withstand significant mechanical deformation of the electrode during cycling, resulting in crack formation. These cracks expose fresh Li underneath, which locally enhances Li-ion flux and promotes morphological deformation of the lithium metal surface. This often leads to dendritic Li deposition that can cause internal short circuits and compromise battery safety. Additionally, repeated failures and repairs of SEIs result in the continued loss of both Li and electrolyte, leading to low coulombic efficiency (CE) and rapid capacity decrease.To mitigate these problems, researchers have attempted to suppress lithium dendrite growth by slurry coating on the lithium metal surface such as ceramic layer and lithiophilic metal. These materials and conventional lithium metal protection coating methods partially inhibit the growth of lithium dendrites; however, they come with several significant drawbacks. The ceramic layer possesses high mechanical properties that physically inhibit the growth of lithium dendrites. However, it exhibits poor interfacial characteristics with lithium metal, leading to increased resistance. This heightened resistance results in the formation of uneven lithium deposition layers at high current densities, causing cracks in the ceramic layer. Lithiophilic metals exhibit an advantage in reducing nucleation resistance through alloying reactions with lithium prior to nucleation, thereby facilitating uniform lithium ion deposition. However, their low mechanical properties limit their potential for enhancing electrochemical performance. Furthermore, the conventional coating method used for lithium metal protection involves the direct application of solvent-containing slurries onto the lithium metal surface using slurry coating techniques. Given the inherent reactivity of lithium metal, the presence of residual moisture and impurities within the solvent may induce sub-reactions, ultimately compromising the stability of lithium metal.In this study, we propose an approach to improve the cycling stability of lithium metal through Ceramic/lithiophilic metal dual protective layer fabricated via transfer-printing methods. The dual lithium metal protection layer, consisting of Ceramic/lithiophilic, involves coating a lithiophilic metal layer between the ceramic layer and the lithium metal. This method aims to maximize electrochemical performance improvement through a synergistic effect that utilizes the high mechanical properties of ceramics and solves the problem of interfacial resistance between the ceramic layer and lithium metal through the lithiophilic metal. Furthermore, we propose a coating process for lithium metal protection layers using a method based on transfer printing. This method involves applying pressure to the lithium metal surface through transfer printing of pre-finished composite protective layers on a film, rather than directly applying slurry onto the lithium metal surface. Transfer printing offers the advantage of maintaining the stability of lithium metal by avoiding direct application of slurry onto the lithium metal surface, thereby ensuring the integrity of the protection layer.

(Digital Presentation) Integrated Membrane Electrode Assembly in Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells (PEMFCs), an electrical device with high energy conversion efficiency and zero-carbon emission, has attracted more attention. The membrane electrode assembly (MEA) is the core component of PEMFCs, mainly including proton exchange membrane (PEM), catalyst layer (CL), microporous layer (MPL) and carbon fiber gas diffusion layer (GDL), which has different structures and significantly affects its power density and durability [1].Generally, MEA is fabricated by catalyst coated electrodes (CCE) and catalyst coated membrane (CCM) methods, which often results in a huge interface resistance between electrode and membrane, the weak adhesion and poor proton and electron transfer, limiting the electrochemical surface area (ECSA) and the power density of PEMFCs [2].To solve this problem, many approaches have been adopted, such as improving sintering temperature for MEA, incorporating a guided cracked layer between cathode and membrane, double-layered catalyst and direct deposition method. Zhao et al prepared an integrated membrane electrode assembly structure to reduce the contact resistance between proton exchange membrane and catalyst layer, which significantly improves the efficiency and stability of water electrolysis [4]. At the same time, Klingele and Breitwieser developed a direct deposition of proton exchange membrane technology to improve high performance and long-term stability of PEMFCs. However, these methods are complex and almost impossible to industrialize [5].In this study, integrated membrane electrode assembly (I-MEA) was prepared by combining casting and doctor blade method techniques. The results show that the casting method is more suitable for fabricating I-MEALT in low-temperature proton exchange membrane fuel cells. The power density of the I-MEALT cell is increased by 18% compared with that of the conventional MEALT (Fig. 1). The doctor blade method is more suitable for preparing I-MEAHT in high-temperature proton exchange membrane fuel cells. The maximum power density of I-MEAHT is increased by about 57% compared with that of the conventional MEAHT. The electrochemical impedance shows that this is mainly attributed to the reduced interface resistance between the electrode and the membrane, which facilitates the proton transfer.

Deep Learning Based 3D Resolution Recovery for Breakthrough Imaging of Electrochemical Energy Devices

Many energy materials can only be understood within the context of the (often sealed) devices they make up. Batteries and fuel cells contain intricate mixtures of materials with features and arrangements that span across many orders of magnitude in size and operate under non-ambient conditions. In these devices, the microstructures of the constituent materials and how they are arranged with respect to each other is directly linked to the device performance and degradation behaviors. Complicating matters, opening the devices for inspection and analysis can irreversibly alter the very microstructures in question and can pose safety hazards to researchers if not done correctly. Furthermore, critical material and device properties such as tortuosity or ion transport pathways can only be accurately quantified in 3D. As such, observing microstructures and their evolution in 3D and in their native state is essential for developing a robust understanding of how to engineer new battery and fuel cell materials and architectures with improved performance.X-ray microscopy (XRM) provides a unique method for observing these microstructures in 3D at high resolutions without needing to open them. However, microscopy techniques like XRM make tradeoffs between FOV and resolution, which can pose challenges for strongly multiscale systems like batteries and fuel cells. For example, if images are acquired at high enough resolution to observe critical features like electrode particle sizes in lithium-ion batteries or gas diffusion layer fiber weaves, catalyst distributions, and microporous layer cracks in polymer electrolyte fuel cells, the field of view of that image is restricted to a small local region of the sample. This means that broader defect distributions or larger scale inhomogeneities will be missed. Additionally, for quantitative analysis applications, this means that statistical relevance will be sacrificed because of the limited analysis volume at the appropriate resolution. And for computational modelling efforts, device level phenomena will not be captured well due to the restricted field of view.Advances in modern AI-based resolution recovery methods combined with the non-destructive multiscale imaging capabilities of X-ray microscopy have allowed researchers to overcome this dependency between resolution and field of view to produce 3D images with both high resolution and large field of view. We present here examples of applying these methods to applications in lithium-ion battery and polymer electrolyte fuel cell research [1].[1] Wang, Y.D., Meyer, Q., Tang, K. et al. Large-scale physically accurate modelling of real proton exchange membrane fuel cell with deep learning. Nat Commun 14, 745 (2023).