Cerium compounds are extensively utilized to enhance the chemical stability of proton exchange membranes (PEMs) due to their efficient scavenging of free radicals; however, cerium ions can reduce the proton conductivity of PEMs and can migrate out of PEMs. In this work, we synthesized a novel compound, cerium phosphotungstate (CeHPW), which effectively reduces the solubility of Ce ions while simultaneously enhancing the proton conductivity of PEMs. Moreover, quercetin was employed to anchor Ce ions further, thereby obtaining water-insoluble QCeHPW. QCeHPW exhibits superior free radical scavenging ability compared to either CeO2 or quercetin alone. Furthermore, the proton conductivity of sulfonated poly(ether ether ketone) (SPEEK) composite membrane containing 7.5 wt% QCeHPW in liquid water at 25 degrees C was 0.052 S cm-1, which represents a 53 % improvement over the SPEEK control membrane (0.034 S cm- 1). The single-cell performance of this membrane is significantly better than that of SPEEK control membrane. In addition, compared to SPEEK membranes doped with quercetin or CeO2, the decay rate of the open-circuit voltage (OCV) for this membrane is lower.

This study fabricated flexible phase change composites (PCCs) by integrating paraffin wax (PW) as the phase change material, ethylene-propylene-diene monomer (EPDM) as the matrix, and expanded graphite (EG) as the adsorption filler. The dual encapsulation networks-comprising EG porous adsorption and EPDM cross-linking structure were engineered to optimize thermal and mechanical performance. The resulting EPDM/PW@EG-60%, featuring a C-S x -C cross-linking network, exhibits excellent low-temperature flexibility, good impact resistance, high latent heat of 140.1 J/g, and satisfactory cycling stability with only 2.4% enthalpy attenuation after 100 thermal cycles. Additionally, it shows a low leakage rate of 1.2% even under 500 g load at 60 degrees C for 10 h. In contrast, EPDM/PW@EG-60%-DCP with a C-C cross-linking network showed correspondingly lower performance: a lower latent heat of 130.8 J/g and reduced cycling stability, with an enthalpy loss of 5.3% after 100 thermal cycles. To our knowledge, this work represents the first report on the influence of EPDM cross-linking network structure on the mechanical strength, latent heat capacity, and thermal cycling stability of PCCs, elaborating the underlying mechanisms. This work provides critical theoretical insights and scientific guidelines for designing flexible PCCs with high latent heat and low leakage rate.

The sharply declined proton conductivity of proton exchange membranes (PEMs) at low relative humidity (RH) severely constricts the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, we develop a composite PEM using plasma-treated Prussian blue analogue (PBA) with well-linked lattice water to address this challenge. The plasma treatment generates more defect-sites of cyano-group in PBA, which accommodates tunable ligand-water, better linking the adjacent zeolitic-water to form a continuous hydrogen-bonding-network for Grotthuss proton conduction. Therefore, the PBA composite PEM achieves a proton conductivity of 102.9 mS cm−1 in water at 80 °C, and maintains 7.5 mS cm−1 at 25% RH, with much reduced conduction activation energy. In PEMFC operated at 80 °C, the composite PEM delivers power densities of 707.7 mW cm−2 and 338.0 mW cm−2 at 100% RH and 25% RH, respectively.

The inherent brittleness of SiCf/SiC composite claddings causes stress concentration and microcrack initiation at micro-defects. Early detection of these cracks under micro-strain is difficult due to their small scale, irregular morphology, and background noise. To address this, an enhanced U-Net model integrated with a novel dualsource attentive block module (DSABM) is proposed. The DSABM effectively fuses multi-scale features and improves discrimination between cracks and background interference. Combined with strategic data augmentation and dynamic dataset splitting, the method demonstrates robust performance. On a dedicated cladding crack dataset, it achieves an F1-score of 86.84% and a precision of 89.21% in detecting cracks larger than 10 mu m, while processing images at 165 frames per second. The model shows strong generalization in complex scenarios, confirming its utility as a reliable, high-speed automated tool for the inspection and safety assessment of nuclear ceramic cladding.

Despite the unique physicochemical properties and tunable surface chemistry of carbon dots (CDs), limited research has been conducted on their use as nanofillers in composite proton exchange membranes (PEMs) for fuel cell applications. In this work, phosphotungstic acid (HPW)-modified branched polyethylenimine (BPEI) coated CDs (CDs-HPW) were incorporated into a sulfonated poly(ether ether ketone) (SPEEK) matrix to develop high-performance nanocomposite PEMs with enhanced proton conductivity. CDs-HPW were synthesized via a simple hydrothermal approach by immobilizing HPW onto the-NH2 and-COOH rich surfaces of CDs through strong ionic and covalent bonding. FTIR, XPS, and TGA results confirmed successful anchoring of HPW on the CDs surface. The incorporation of CDs-HPW into the composite membranes resulted in a substantial enhancement in proton conductivity, reaching approximately 43% higher than that of the SPEEK control membrane. The long-term water-immersion test revealed no detectable HPW leaching, demonstrating the robust anchoring of HPW on the CDs surface. In addition, the SPEEK/CDs-HPW-3% composite membrane exhibited slightly lower hydrogen crossover and comparable oxidative stability relative to pristine SPEEK. The membrane electrode assembly (MEA) based on the SPEEK/CDs-HPW-3% composite membrane achieved a peak power density of 472 mW/cm2, approximately 30% higher than that of the SPEEK-based membrane.

The damage and failure mechanisms of SiCf/SiC composites under low strain remain unclear. This study proposes a multi-stage CT combined with iterative semi-supervised deep learning approach. Compared with conventional methods, the 3D approach reduces the relative error in porosity estimation for post-failure specimens by approximately 37%, enabling a transition from 2D inference to quantitative 3D characterization. Multi-stage CT captures the sequential evolution and competition of damage modes. At low strain, damage initiates as matrix microcracks; with increasing load, crack deflection at the fiber/matrix interface becomes a critical transition, shifting the dominant mechanism from matrix cracking to interfacial delamination. Ultimately, the coalescence of delamination cracks leads to macroscopic failure, accounting for the vast majority (exceeding 85%) of the total crack volume. Quantitative analysis reveals that during the accelerated damage stage, when the cumulative volume fraction of delamination cracks surpasses approximately 80%, the equivalent diameter of the largest connected domain undergoes an abrupt increase of over 30%, indicating rapid crack coalescence and the attainment of a critical damage threshold. These findings identify interfacial delamination as the dominant failure mechanism and provide quantitative insights for reliability assessment and material design optimization.

Tungsten (W)-based cermet fuels have garnered significant interest in nuclear thermal propulsion (NTP) systems due to their high melting point, thermal properties, and compatibility with hydrogen (H2) propellants. The W-Y2O3 composite matrix prepared by spark plasma sintering (SPS) exhibits greater densification and suppressed grain growth compared to pure W. Since NTP systems operate at temperatures above 2300 degrees C, the microstructural evolution under elevated temperatures is crucial to fuel performance. This study investigates the high temperature effects on the microstructure of pure W and W-Y2O3 matrices fabricated by SPS. The matrices were subjected to temperatures ranging from 1800 degrees C to 2300 degrees C. Below 2300 degrees C, Y2O3 particles effectively inhibited W grain growth through the Zener pinning effect, thereby increasing the proportion of low-angle grain boundaries (LAGBs). At high temperatures, H2diffuses into the matrix, reacting with uranium dioxide (UO2), which contributes to fuel loss. The fine grains increase grain boundary density, extending H2 diffusion paths, while LAGBs help mitigate harmful H2 accumulation. However, at 2300 degrees C, W diffuses into Y2O3, causing the Y2O3 grains to grow and leading to the formation of pores and cracks. This weakens the Zener pinning effect, promoting abnormal grain growth of W, which ultimately results in an increase in high-angle grain boundaries (HAGBs) and accelerates the diffusion of H2. The study identifies three stages of W diffusion into Y2O3: initial enrichment at Y2O3 grain boundaries, formation of W-depleted/W-enriched island-like structures within Y2O3 grains, and the formation of a Y6WO12 core-Y2O3 shell structure at 2300 degrees C, providing valuable insights for optimizing Y2O3 composites for NTP applications.

Current research on epoxy (EP) vitrimers primarily focuses on enhancing material mechanical properties and self-healing efficiency. However, EPs with high mechanical strength struggle to reconcile network dynamicity due to their high crosslinking density or substantial content of rigid moieties. Consequently, they often require harsh repair/recycling conditions, exhibit low recycling efficiency. In this study, a series of EP vitrimers with different crosslinking network structures was prepared by reacting a high-rigidity group-concentrated multi-reversible dynamic bond long-chain curing agent with a flexible epoxy monomer containing polyether bonds. The concept of crosslinking network rigid-flexible ratio (CRFR) was introduced to quantify the properties. Through structural optimization, the EP vitrimer demonstrated ultrahigh tensile strength (91.6 MPa) and storage modulus (2.65 GPa). Its excellent network dynamicity resulted in an ultra-fast stress relaxation rate (8.7 s at 120 degrees C), outstanding processability and shape-memory properties. Furthermore, the EP vitrimer can be fully degraded at 50 degrees C in either an HCl pure H2O/DMF solution. The degradation products can be repolymerized directly, enabling green closed-loop recycling with full retention of the original mechanical strength. This work provides an important theoretical foundation and a new pathway for the design of high-strength polymers, as well as for the green recycling of EP vitrimers.

The development of flexible phase change composites (PCCs) with high latent heat, low leakage, and reliable performance in harsh environments remains a great challenge. This study presents a novel PCC by employing acrylonitrile butadiene rubber (NBR) as a flexible matrix, palmitic acid (PA) as the phase change material, and polydopamine-modified montmorillonite (DMMT) as a barrier filler. NBR grade with 26% acrylonitrile content exhibited optimal compatibility with PA, driven by a close match in dispersion surface energy components. The DMMT, uniformly dispersed and exfoliated within NBR, constructed a tortuous labyrinth, which worked with the NBR crosslinking network to encapsulate the PA. This endowed the PCC with a high latent heat of 118.6 J g-1 and low leakage rate (1.1% after 8 h at 80 degrees C). Furthermore, the PCC demonstrated outstanding cyclic stability and remarkable performance retention in transformer oil. This work provides profound insights into the compatibility mechanism and an effective preparation strategy for high-performance PCCs, demonstrating great potential for thermal management applications in harsh conditions.

CeO2 is incapable of conducting protons and tends to leach from the proton exchange membrane (PEM) under the acidic conditions during fuel cell operation, consequently deteriorating both the power density and durability of the fuel cell. In this work, we prepared an acid-insoluble HPCe hybrid by combining polyethyleneiminepolydopamine (PEI-PDA) crosslinked coated CeO2 with phosphotungstic acid, a strong proton conductor. The PEI-PDA coating not only prevents the dissolution of CeO2 in acidic environments but also suppresses the leaching of HPW. When incorporated into Nafion, the composite membrane containing 2 wt% HPCe exhibits a proton conductivity of 0.115 S cm- 1 in liquid water, which is 15% higher than that of the recast Nafion membrane (0.100 S cm-1), while remaining stable for 2 months. After being assembled in the fuel cell, the performance and operation stability of the composite membrane significantly outperforms the recast Nafion membrane.

Molybdenum (Mo)-based cermet fuel elements represent a promising fuel form for nuclear thermal propulsion (NTP) applications. Compared to tungsten (W)-based materials, Mo-30wt%W (Mo-30W) alloy offers a lower neutron absorption cross-section, making it more suitable for high-assay low-enriched uranium (HALEU) fuels. However, previous studies on Mo-30W have mostly focused on empirical comparisons of process parameters and density, without establishing a quantitative relationship between temperature, solubility, density, and mechanical properties. This study uses spark plasma sintering (SPS) to simultaneously investigate the effects of temperature on densification and solid solution evolution. As the temperature increases, the solid solubility of W in the Mo matrix increases significantly, leading to an increase in the solid solution lattice parameter. Its solubility in Mo increases from 9.86 wt% at 1400 degrees C to 25.87 wt% at 1800 degrees C. Simultaneously, the relative density of Mo-30W alloy is about 95% at 1400 degrees C and exceeds 98% at 1800 degrees C. Increased temperature drives recrystallization and grain growth, eliminating porosity. The proportion of low-angle grain boundaries (LAGBs) peaks around 1500 degrees C and then declines. Microstructural characterization shows that the densification process is dominated by grain boundary diffusion, with an activation energy of approximately 260 kJ/mol. These micro-structural changes are closely related to thermodynamic properties. At low temperatures, thermal conductivity and hardness are mainly affected by porosity, and both reach peaks at 1500 degrees C. At higher temperatures, grain coarsening becomes dominant, weakening the Hall-Petch effect and thus reducing hardness. The increased solubility of W in Mo leads to increased lattice parameters and enhanced lattice distortion, while recrystallization promotes an increase in the proportion of high-angle grain boundaries (HAGBs). Both of these factors enhance phonon scattering, increase thermal resistance, and cause a slow decrease in thermal conductivity.

Heteropoly acids (HPAs) serve as effective additives for enhancing proton transport in composite proton exchange membranes (PEMs) because of their high proton mobility. However, their high-water solubility leads to leaching, reducing long-term proton conductivity and stability, and thereby limiting the application of HPA-based composite membranes. Here, we describe a simple hydrothermal method for creating water-insoluble phosphotungstic acid-benzimidazole-linked polymer (P-BILP) nanohybrids, where phosphotungstic acid (HPW) is embedded within the BILP framework. The successful incorporation and stabilization of HPW in the polymer matrix were confirmed by XRD, FTIR, and XPS analyses. As a result, HPW leaching is successfully inhibited. Incorporating P-BILP filler into sulfonated poly (ether ether ketone) (SPEEK) significantly enhances the performance of blended membranes for fuel cell applications. SPEEK/P-BILP demonstrates 63% higher proton conductivity in liquid water. The membrane electrode assembly using SPEEK/P-BILP achieves 30% greater power density at 60°C under 100% relative humidity (RH). These results indicate that improved proton conductivity and power density make this composite membrane more effective for practical fuel cell use.

ABSTRACT The corrosion problems of high‐voltage power transmission conductors typically occur in environments with electric fields. However, current research mainly focuses on atmospheric corrosion of metals with limited attention to the combined effects of electric fields and atmospheric conditions on metal corrosion. This study established a corrosion prediction model that considers the effects of electric fields and dynamic boundaries. Because of the influence of dynamic boundaries, this model can calculate parameters such as corrosion rate, corrosion depth, corrosion product accumulation and ion concentration for metal samples with and without an external electric field. The model is validated through indoor accelerated corrosion tests under low applied electric fields and by using aluminium alloy conductor samples from high electric field regions of actual ± 500 kV power transmission lines. The results indicate that the corrosion rate of aluminium alloys initially increases and then decreases over time. Additionally, the corrosion rate of aluminium alloys under an applied electric field is higher than that without an electric field during the same period. The mechanism of increased corrosion rate is analysed to be that the presence of the electric field accelerates the cathode reaction rate of the electrode. The corrosion rate of the sample increased by about 78% under a lower electric field (0–20 kV/m) and by about 2.75 times under a higher electric field around 2000 kV/m.

A novel graphite matrix was prepared by adding carbon black (CB) as a densification agent to traditional matrix A3-3 graphite preparation. The particle size of CB densifier we chose was approximately 50-150 nm, which was smaller than the pore diameter of densified matrix graphite (500-1000 nm). Five different mass fractions of CB were mixed and compared with as-received A3-3 by various characterization methods, which indicated that CB can effectively fill the pores of A3-3 and improve its anti-infiltration capability against molten salt (fluoride salt for molten salt reactor and heat storage salt). Meanwhile, considering the requirements for A3-3 graphite in scenarios of solid fuel molten salt reactor and thermal energy storage system, all the samples were compared as well before and after purification. The results showed that purification treatment resulted in slight increase of the pore size and open porosity of graphite and thus weakened its anti-infiltration capability against molten salt, but the thermal properties of graphite improved inversely. However, the addition of excessive CB could cause the significantly decline of thermal properties of A3-3. Comprehensively considering the anti-infiltration effect and requirements of thermal properties, adding 5% CB was the most preferrable choice for the matrix graphite before and after purification.

Covalent organic frameworks (COFs) are highly porous crystalline polymers with well-defined pore structures, exhibiting great potential for the use of composite membranes to separate ions with different sizes. However, COFs are mostly insoluble and poorly dispersed in common solvents, making it very difficult to well disperse COFs in polymer matrix to prepare high-quality composite membranes. In this work, a MS hybrid was prepared by in-situ growing COFs on the surface of Ti3C2Tx MXenes, which helps improve the filler-matrix compatibility significantly. The synergetic effect of the two-dimensional structure of MXene nanosheets and the porosity of COF components in MS contributes to the improvement for the ion selectivity of the composite membranes (SPEEK/MS). The vanadium flow battery (VFB) loaded with the SPEEK/MS-10 membrane achieves the energy efficiency of 93 % at 40 mA cm-2, as compared to 86 % for that with the SPEEK control membrane. Moreover, the improved cycling stability and capacity retention was achieved for the SPEEK/MS-10 based VFB. Therefore, this work provides a promising strategy to fabricate high-performance COF-based composite PEMs for the VFB applications.

Styrene-butadiene rubber/[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride/clay nanocomposites (SBR/METAC/clay NCs) were obtained via a novel strategy combining a gel compounding approach and hydrophilic modification of the matrix. The influences of METAC-induced hydrophilic modification, clay loading, and composite fabrication methodology on the mechanical performances and microstructural characteristics of SBR/clay NCs were systematically investigated. SBR/METAC/clay NC showed a good filler dispersion, and there existed a clay intercalation structure when the ratio of clay to METAC was low. At a clay loading of 30 phr, the SBR/METAC/clay NCs exhibited a maximum tensile strength of 17.6 MPa, representing a tenfold enhancement compared to pure SBR. The interface interaction research revealed the reinforcement mechanism: METAC builds a bridge of clay-SBR interaction by co-crosslinking with SBR and interacting with clay by electrostatic interaction, and promotes more SBR macromolecular chains to anchor to clay, which significantly improves the mechanical performances of SBR/METAC/clay NCs. Benefiting from the excellent exfoliation and dispersion of clay layers within the SBR matrix, coupled with their inherent 2D lamellar structure, SBR/METAC/clay NCs are anticipated to find applications in areas such as barrier properties against gases or liquids.

Vanadium flow battery (VFB) requires efficient proton exchange membrane (PEM) toward realistic utilization. Although sulfonated covalent organic framework (SCOF) seems promising to prepare alternatives over traditional PEMs, the present SCOF-based membranes, either free-standing or composite, are widely afflicted by complicated synthesizing procedure, low proton/vanadium selectivity or weak mechanical strength. Herein, a one-pot method is proposed to prepare an updated paradigm of polymer-SCOF composite PEM. This easyhandling method accommodates the homogeneous in-situ synthesis of SCOF in the solution of sulfonated poly (ether ether ketone) (SPEEK) during casting, which circumvents the problems of interfacial compatibility and filler agglomeration usually encountered in traditional composite materials, rendering good miscibility and high loading of SCOF. Concurrently, the in-situ synthesized SCOF automatically forms the pores with substantial insertion by SPEEK chains, which restricts SCOF sheets from stress separation, thereby obviously mitigating mechanical brittleness. Furthermore, by adequately occupying SCOF pores, vanadium ion barrier property is evidently improved. Therefore, the one-pot prepared composite PEM with 50 wt% loading SCOF realizes a proton conductivity of 0.071 S cm(-1), and a VO2+ permeability of 1.2 x 10(-7) cm(2) min(-1) at 25 degrees C, as well as optimized swelling ratio and mechanical strength. Applied in VFB, such advantageous membrane enables a

The hydrodynamic characteristics of heavy particles in a conical spouted bed at high temperatures are of critical importance for nuclear fuel coating. In this study, the effects of temperature and gas flow on the hydrodynamic behavior of heavy particles in a conical spouted bed were systematically investigated by using power spectral density (PSD). The experimental results indicate that the intensity of the main frequency peak in the annular zone decreases, while that in the spout zone gradually increases with an increasing gas flow rate at the same operating temperature. Meanwhile, the intensity and magnitude of the main frequency peak slowly decline, and the main frequency peaks broaden with the increase of temperatures at the corresponding gas flow. Based on these phenomena, the influence mechanism of temperature on the hydrodynamics of heavy particles is proposed: the large and uniform bubbles at lower temperatures evolve into the slightly small bubbles of various sizes at higher temperatures, which will increase the volume fraction of particles in the spout zone and thus improve the efficiency of spouting. This study reveals the hydrodynamic characteristics of heavy particles and provides deeper insights into spouting behaviors for nuclear fuel coating at high temperatures.

The trade-off between proton conductivity and mechanical stability is a core challenge in designing highperformance proton exchange membranes (PEMs). Uniaxial stretching can improve the overall performance of the materials by creating ordered polymer structures. Currently, the effects of uniaxial stretching on the ordered structure, hydrophilic-hydrophobic phase interactions, and various properties of the membranes have not been fully explored. In this paper, PEMs with ordered structure were fabricated using uniaxial stretching technique, which oriented the ion channels, thus offering the membranes enhanced conductivity and mechanical properties simultaneously. The comprehensive investigation of the effects of stretching on internal structure, microphase separation, proton conductivity, mechanical properties, and gas barrier of the membranes was conducted, while the intrinsic mechanisms behind the improved proton conductivity were explored. It was demonstrated that uniaxial stretching induced the ionic and inter-crystalline domains within the membranes to be oriented. The size and amount of hydrophilic domains were increased, and the connectivity of hydrophilic ion channels was then enhanced. Consequently, the proton conductivity of the stretched membrane was 1.25 times that of the pristine membrane. Molecular dynamics simulations validated these observations, providing theoretical underpinnings for the improved conductivity. Meanwhile, stretching facilitated the orderly arrangement of polymer chains, thereby increasing the crystallinity of the PEMs from 12.27 % to 18.95 %. These changes in the microstructure contributed to the improvement of macroscopic properties, e.g., the tensile strength and Young's modulus of the membranes increased by 40.65 % and 22.38 %, respectively. These findings provided valuable insights for the design and development of ordered PEMs.