Severe Agglomeration Research Articles

Effect of Synthesis Temperature on Performance of Phenazine-Based Cathode for Sodium Dual-Ion Batteries.

Organic materials have attracted much attention in the field of electrochemical energy storage due to their ecological sustainability, abundant resources and structural designability. However, low electrical conductivity and severe agglomeration of organic materials lead to poor discharge capacity and reaction kinetics in batteries. Herein, the morphology of the phenazine-based organic polymer poly(5,10-diphenylphenazine) (PDPPZ) was modified by varying the synthesis temperature. PDPPZ-165 °C with an exceptional porous structure provides abundant reaction channels for rapid charge transfer and diffusion that improves the reaction kinetics in sodium dual-ion batteries. Therefore, PDPPZ-165 °C cathode possesses excellent rapid charge-discharge capability delivering a specific capacity of 119.2 mAh g-1 at 40 C. Furthermore, a high specific capacity of 124.7 mAh g-1 can be provided even at a high loading of 16 mg cm-2 at 0.5 C with a capacity retention of 86.4 % after 500 cycles. This work could afford new insights for optimizing the performance of organic cathode materials in sodium dual-ion batteries.

Towards the high RAP dosage obtained by refined processing influence on comprehensive performance of recycled asphalt mixture

The severe agglomeration of Reclaimed Asphalt Pavement (RAP) particles not only leads to high gradation variability during recycling, but also impedes the miscibility between new-old binders. This phenomenon imposes significant limitations on maximizing the utilization of RAP with high content and value. This paper first realized the effective separation of asphalt milling material by the self-developed RAP refined processing equipment to obtain coarse RAP with low binder content and fine RAP with high binder content. The fine RAP with high binder content underwent a deep rejuvenation process, and the recovery efficiency of the asphalt mortar was evaluated by CT scanning test, microscope observation test, and dynamic shear rheology test. Moreover, to investigate the strength formation characteristics of recycled asphalt mixtures with high RAP content, specific tests including wheel tracking test, three-point bending test, Hamburg Wheel Tracking test, dynamic modulus test, and two-point bending fatigue test, were conducted. By using the refined processing equipment, the asphalt film on the RAP can be precisely removed, thereby addressing the issue of aged binder agglomeration. In the coarse RAP with low binder content, the binder content was reduced to 1.48 %, allowing it to be used as a direct substitute for new aggregate, whereas the binder content of fine RAP exceeded 10 %. It was found that the direct incorporation of unrefined RAP enhanced the high-temperature stability and dynamic modulus of recycled asphalt mixture, but impacted their low-temperature cracking resistance, moisture stability, and fatigue performance. After refined processing and differentiated recycling design, the agglomeration of aged binder was reduced and the miscibility of new-old binders was improved, effectively enhancing the comprehensive performance of the recycled asphalt mixture. It should be noted that the mixing homogeneity and miscibility decrease as the RAP content exceeds 75 %, resulting in the reduction of moisture stability, cracking resistance, and fatigue performance of recycled asphalt mixture.

Heterostructured GCN Nanosheets/ZnO nanoflowers for enhanced TMO loading: From high-performance three electrode systems to printed flexible asymmetric supercapacitors

Transition metal oxides (TMOs) are widely used in the development of high-energy-density devices due to their multiple oxidation states and their frequent heterostructuring with carbon-based materials. However, the synthesis process often leads to severe nanoparticle agglomeration and weak synergistic effects with carbon-based templates, thereby limiting their application potential. In this study, we constructed graphitic carbon nitride (GCN) nanosheets/ZnO nanoflowers (NFs) structures with high TMOs loading by utilizing GCN nanosheets, which are rich in surface nitrogen content, as enriched templates for metal ions in conjunction with ultrasonic cavitation. Compared with GCN nanosheets/ZnO nanoparticles (NPs), the ZnO NFs exhibited vertical growth and a fluffy structure on a 2D material template, which resulted in high electronic conductivity, a large effective surface area, hierarchical pores, and strong synergistic interactions with GCNs, thus improving electrochemical performance. This structural enhancement enabled the GCN/ZnO NFs electrodes to achieve a high specific capacitance of 1524F g−1 at a current density of 1 A g−1 in a three-electrode supercapacitor system. Additionally, we formulated GCN/ZnO NFs into electronic inks and used them for the mass production of flexible supercapacitors with the aid of dispensing printing technology. These flexible supercapacitors retained 94% of their specific capacitance even under extreme conditions of 90° torsion. Our proposed strategy of modulating TMOs and 2D structures can create active electrode materials with higher loading capacities, thereby enabling comprehensive customization in material design and device preparation processes.

Synthesis of Monodisperse and Discrete Ultra-High Nickel LiNi0.97Co0.02Mn0.01O2 Octahedral Single Crystals via Single Crystal Intermediates for Li-Ion Batteries.

Micrometer-sized single crystal cathodes have garnered significant interest as promising cathode materials for lithium-ion batteries due to their ability to reduce surface area exposure to electrolytes and suppress side reactions, thereby enhancing electrochemical performance. One of the challenging issues with single crystal cathode materials is synthesizing monodisperse and discrete single crystals rather than agglomerated quasi-single crystals. However, conventional solid-state synthesis of most single crystals results in severe agglomeration and cation mixing, as it requires high temperatures to promote particle growth to several micrometers. In this study, a novel morphology-conserving reaction strategy that employs octahedron single crystal intermediates is introduced to synthesize discrete, monodisperse LiNi0.97Co0.02Mn0.01O2 octahedron single crystals. This scalable and cost-effective approach involves using rock-salt Ni0.97Co0.02Mn0.01O1+x octahedrons as single crystal intermediates, which are transformed in unreactive unary lithium salt melts (LiCl and Li2SO4) from spherical Ni0.97Co0.02Mn0.01(OH)2 obtained via coprecipitation. These intermediates are then subjected to a stoichiometric amount of Li precursor in a conventional solid-state synthesis to produce layered LiNi0.97Co0.02Mn0.01O2. This process is a morphology-conserving lithiation reaction, leading to the formation of discrete and monodisperse LiNi0.97Co0.02Mn0.01O2 octahedron single crystals. The resultant LiNi0.97Co0.02Mn0.01O2 single crystals demonstrate superior electrochemical performance, including stable capacity retention over 150 cycles, which surpasses that of typical quasi-single crystals produced through conventional methods. This is attributed to negligible crack formation during cycling, in contrast to significant cracking observed in conventional quasi-single crystals. This implies that single-crystal forms are preferred over agglomerated quasi-single crystal forms for enhancing cycle performance. These findings provide valuable insights into the industrial synthesis of discrete and monodisperse ultrahigh-nickel oxide cathode materials.

Comparative study of blending techniques in polylactic acid/cellulose nanofibrils green composites for benchtop 3D printing filaments

AbstractAdditive manufacturing for polylactic acid (PLA) reinforced with cellulose nanofibrils (CNF) could unlock fabrication of specialized and user‐specific biomedical devices. However, the process of combining PLA and CNF is challenging and proves complicated with possible irreversible CNF agglomeration and organic solvents leftover, particularly when involving solvent‐casting technique. Direct melt‐blending can mitigate these issues, but there are few reports of a single‐step melting and extrusion process to produce ready‐to‐use 3D printing filaments. This study compares the distribution of CNF fillers within the PLA matrix in PLA/CNF composites made by direct melt‐blending into filaments using a benchtop filament maker, and by solvent‐casting followed by extrusion into filaments. The filaments were 3D‐printed via fused deposition modeling (FDM), followed by tensile testing, morphology, and other characterizations. Uneven filament diameters were observed for the composite filaments prepared via solvent‐casting because of severe agglomeration, resulted in poor printability and tensile properties of filaments and 3D‐printed samples. Direct melt‐blended filament diameters were consistent, resulted in only slight decrease of tensile properties compared to pure PLA, contributing to the highest maximum tensile strength of 3D‐printed sample of 51.47 ± 1.73 MPa at 5% CNF loading. Morphology revealed good integration of CNF into PLA matrix starting at 3% CNF loading. Direct melt‐blending was comparable to the conventional methods, which enables simpler PLA/CNF composite preparation especially for 3D printing.Highlights Better dispersibility achieved by direct melt‐blending than by solvent‐casting. PLA/CNF filaments produced via solvent‐casting suffered severe agglomeration. Direct melt‐blended PLA/CNF5% yielded the highest maximum tensile strength. Morphology reveals good CNF‐PLA integration starting at 3% of CNF loading. Worsened agglomeration causing increased number of voids observed at 10% CNF.

Enhancing separation performance of thin film nanocomposite membranes by self-etching of polydopamine-modified calcium carbonate during interfacial polymerization process

The acid-accepting and gas-generating properties, along with the formation of extensive nanovoids, make CaCO3 nanoparticles attractive as sacrificial nanofillers for fabricating thin-film composite (TFN) nanofiltration membranes. However, challenges such as severe agglomeration and limited acid etching efficiency of the nanoparticles hinder the pursuit of superior membrane performance. In this study, the dispersion and compatibility of CaCO3 nanoparticles within the membrane matrix were improved by modifying them with a polydopamine (PDA) coating. The abundant phenolic hydroxyl groups of PDA enhanced the hydrophilicity and negative charges of membrane surface. Additionally, the PDA capsule increased the etching extent of the CaCO3 nanoparticles by improving the nanoparticle dispersion and generating additional acid, which created sufficient water channels within the polyamide layer. It was demonstrated that incorporating 45 μg/cm2 of PDA-modified CaCO3 nanoparticles doubled the water permeance to 16.7 LMH/bar, while maintaining a low molecular weight cut-off of 249 Da and achieving rejections over 90% for five types of per- and polyfluorinated substances. The PDA modification also overcame the membrane stability issue caused by the agglomerated CaCO3 nanoparticles. This study provides a novel strategy for applying properly modified self-etching nanofillers in TFN membrane development, showing great potential for water treatment applications.

Revisiting the catalytic activity of single horseradish peroxidase clusters through electrochemical collision technique: Effect of electrolyte and substrate

Horseradish peroxidase (HRP) is a versatile biosensing label and signal reporter owing to its broad-spectrum catalytic ability. In present work, we characterized HRP's catalytic performance with various substrates using electrochemical collision technique and analyzed the associated electron transfer processes. Different electrolyte solutions greatly affected enzyme dispersibility and zeta potential, thereby impacting HRP collision dynamics in single H2O2 substrate system. The maximum turnover number (kcat) for single HRP molecules was calculated to be 3.611 ± 0.149 × 103 s−1 in 0.85 % NaCl and 2.967 ± 0.286 × 103 s−1 in 0.1 M PBS solution, reflecting differences in cluster size induced by the electrolyte conditions. More severe agglomeration of HRP molecules was observed in double-substrate systems, where the hydrophilic mediator (K4Fe(CN)6) and lipophilic mediator (ABTS) served as electron donors and signal reporters. The calculated kcat value of single HRP molecules in ABTS-H2O2 was 7.6 times higher than that in K4Fe(CN)6–H2O2. This difference is attributed to mediators' solubility, lipophilicity, and HRP's affinity for different substrates, with HRP demonstrated stronger affinity for ABTS-H2O2 substrates, which realized more efficient electron transfer and compensated for the low diffusion coefficient of ABTS. This work provides a comprehensive analysis of the effects of electrolytes and substrates on HRP collision and catalytic behavior, offering valuable insights for the advanced design of HRP-based biosensors and diagnostic platforms.

A modified drag model for the fluidization of nano-modulated Group C particles

Geldart Group C powders are inherently cohesive due to the strong interparticle forces, leading to severe agglomeration and poor fluidization capability. In this study, fluidization of nano-modulated Group C particles was investigated numerically. These particles, also known as Group C+ particles, were obtained through the nanoparticle modulation technique, with which a small fraction of nanoparticles were vigorously mixed with Group C particles so that they are adhered to the surface of the much larger Group C particles. After modification, the cohesiveness of Group C+ particle was significantly weakened, and therefore these particles could exhibit much better fluidization quality. However, the still existing cohesion resulted in the formation of small agglomerates within the system. To understand the internal agglomeration mechanisms of Group C+ particles and their impact on fluidization behaviors, a new drag model was proposed based on experimental results and the postulation of particle agglomeration. The numerical results of the cases employing the new drag model agreed well with the experimental data in terms of total and dense phase expansion. These findings revealed the drag mechanism associated with modified Group C particles, contributing to the understanding of ultrafine particle fluidization.

Enhanced powder characteristics of succinic acid through crystallization techniques for food industry application

During crystallization, succinic acid, an important food additive, exhibit severe agglomeration behaviour, uneven crystal size distribution (CSD), and irregular crystal morphology, resulting in poor powder flow properties. This paper presents an innovative approach to optimize succinic acid crystallization through investigation of novel blade milling method, seeding, and inclusion of green additive, cetyltrimethylammonium bromide (CTAB). CTAB for crystal habit regulation and formation of desired cubic-like morphology. We employ Mask R-CNN, a deep learning-based image analysis tool to quantitatively assess crystal and powder flow properties. Results demonstrate that the inclusion of 0.5 wt% CTAB with two-stage cooling method yields uniform CSD ranging from 30 μm to 160 μm and improves powder properties, reducing the agglomeration degree by 46% and caking ratio to only 6.78%, indicating a decreased tendency for clumping. The integration of crystallization with the proposed deep learning framework not only improves succinic acid food functionality but also showcases highly efficient method for optimizing crystal properties, setting new standard for food crystallization processes. It has been adequately presented with real-time high-precision analysis of CSD, agglomeration, etc, facilitating rapid screening for optimized food quality improvements.

Optimisation of Mo doping to form NiCoMo ternary sulphides for high performance charge storage.

Multi-component synergy and the rational design of structures are effective methods for preparing electrode materials for high-performance energy storage devices. Transition metal-based hydroxides offer advantages such as a large specific surface area, large interlayer spacing, multiple redox states, and high theoretical capacity, making them commonly used as positive materials for supercapacitors. However, challenges like low conductivity and severe agglomeration limit their practical application. This study focuses on the preparation of Ni, Co, and Mo ternary transition metal hydroxides by incorporating the Mo element to optimize their structure. Furthermore, sulfide ions were utilized in an ion exchange process to replace hydroxides, resulting in the formation of NiCoMo ternary sulfide electrode materials. By adjusting the amount of Mo added, a spherical nanoneedle-shaped N2C1MS0.2-2 electrode material was successfully synthesized. This electrode exhibited a specific capacity of 2094 F g-1 at a current density of 1 A g-1. In addition, an asymmetric supercapacitor was assembled with activated carbon as the negative electrode and N2C1MS0.2-2 as the positive electrode, which had an energy density of 46.2 W h kg-1 at a power density of 800 W kg-1, a capacity retention of 89.7% and a coulombic efficiency of 97.8% after 10 000 cycles. This study provides a reference for the design and preparation of ternary sulphide electrode materials.

Eco‐friendly enhancement of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) bridgeable composites using natural cotton stalk: A novel approach to improved mechanical, barrier properties, and compatibility

AbstractThis study investigates the potential of using natural cotton stalk (CS) to enhance the properties of poly(lactic acid) (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) composite materials. Simple processed CS, used as a bio‐based filler, is integrated into the PLA/PBAT matrix with the objective of improving mechanical properties, barrier performance, and compatibility, while simultaneously reducing costs and environmental impact. The experiments conducted include tensile testing, scanning electron microscopy analysis, Fourier‐transform infrared spectroscopy (FTIR) analysis, X‐ray diffraction study, thermogravimetric analysis, contact angle measurement, water absorption tests, as well as water vapor and oxygen permeability tests. The results demonstrate that the inclusion of CS significantly enhances the mechanical properties and crystallinity of PLA/PBAT composites, along with increasing their water vapor and oxygen barrier capabilities. Compared to PLA/PBAT without CS, the addition of 2% CS to PLA/PBAT led to substantial improvements in tensile strength and elongation at break, with increases of 21.5%, 41.6%, and 74.4%, respectively. Additionally, scanning electron microscopy and Fourier‐transform infrared spectroscopy analyses indicate that the incorporation of CS promotes the compatibility and chemical interaction between PLA and PBAT, thereby enhancing various properties of the composite material. Image analysis revealed that the distribution area of CS fibers in the polymer matrix increased with content up to a peak at 2% but decreased at higher contents due to severe agglomeration, leading to uneven distribution and performance decline. This work proposes three possible reasons for the improvement in water vapor and oxygen permeability performance. Overall, the analysis suggests that an optimal amount of CS can effectively enhance multiple properties of PLA/PBAT composites, while excessive CS may lead to a decline in performance.Highlights Cotton stalk (CS) boosts polylactic acid/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) tensile strength by 21.5% and elongation by 41.6% at 2% inclusion. CS addition enhances water vapor and oxygen barrier properties of PLA/PBAT. Scanning electron microscopy and Fourier‐transform infrared spectroscopy show CS improves PLA/PBAT compatibility and strength. Optimal CS content at 2% identified for best mechanical and barrier performance. Study validates using agricultural waste as fillers in eco‐friendly composites.

Development of high-dispersion CLDH/carbon dot composites to boost chloride binding of cement

Chloride-induced corrosion of steel reinforcement significantly contributes to the durability deterioration for reinforced concrete (RC) structures. Calcined layered double hydroxide (CLDH) possesses a distinctive structure memory effect to adsorb anions and a nucleation effect to facilitate cement hydration, thereby demonstrating a promising potential for chloride binding enhancement of cementitious materials. However, CLDH suffers from severe agglomeration in cement composites, limiting its performance efficacy. To tackle this problem, novel high-dispersity CLDH/carbon dots (CDs) composites (CC) only at small dosages are applied to greatly improve the chloride binding behavior of cement pastes for the first time. In detail, the specific surface area of CC synthesized by simply stirring CDs and CLDH improves by 166.4 % than that of pure CLDH. Remarkably, cement pastes containing CC display a preferable chloride binding capacity; And the chloride binding substantially increases by 52.41 % when the incorporation of CC (by weight of cement) is 0.8 wt%. More importantly, according to the phase composite and microstructure analyses, the chloride binding enhancement mechanism of CC-containing cement pastes is reasonably ascribed to two effects of CC: providing nucleation sites to accelerate cement hydration and exerting the inherent chloride adsorption capacity. This boosts the formation of C–S–H gels and improves the structure memory effect and anions exchange-induced chloride adsorption, thus significantly strengthening the chloride binding of cement. This work provides a novel approach to improve the dispersity of CLDH, effectively strengthening the chloride binding of cement, thereby conductive to prolonging the service life of RC structures.

Mitigating kinetic hindrance of single-crystal Ni-rich cathodes through morphology modulation, nickel reduction, and lithium vacancy generation achieved by terbium doping

Single crystallization has proven to be effective in enhancing the capacity and stability of Ni-rich LiNi1−x−yCoxMnyO2 (SNCM) cathode materials, particularly at high cut-off voltages. Nevertheless, the synthesis of high-quality single-crystal particles remains challenging because of severe particle agglomeration and irregular morphologies. Moreover, the limited kinetics of solid-phase Li+ diffusion pose a significant concern because of the extended diffusion path in large single-crystal particles. To address these challenges, we developed a Tb-doped single-crystal LiNi0.83Co0.11Mn0.06O2 (SNCM-Tb) cathode material using a straightforward mixed molten salt sintering process. The Tb-doped Ni-rich single crystals presented a quasi-spherical morphology, which is markedly different from those reported in previous studies. Tb4+ doping significantly enhanced the dynamic transport of Li+ ions in the layered oxide phase by reducing the Ni valence state and creating Li vacancies. A SNCM-Tb material with 1 at% Tb doping shows a Li+ diffusion coefficient up to more than 9 times higher than pristine SNCM in the non-diluted state. In situ X-ray diffraction analysis demonstrated a significantly facilitated H1-H2-H3 phase transition in the SNCM-Tb materials, thereby enhancing their rate capacity and structural stability. SNCM-Tb exhibited a reversible capacity of 186.9 mA h g−1 at 5 C, retaining 94.6% capacity after 100 cycles at 0.5 C under a 4.5 V cut-off. Our study elucidates the Tb4+ doping mechanisms and proposes a scalable method for enhancing the performance of single-crystal Ni-rich NCM materials.

Designing a high-performance electrode material for hybrid supercapacitor: 1D–2D NiCo carbonate hydroxide nanofiber interlinked microsheet architecture

Developing simple nanoarchitecture and exploiting distinctive components are the two most significant strategies for advancing high-performance electrode materials for hybrid supercapacitors (HSCs). However, severe agglomeration and inability to maintain a stable structure or design of nanomaterials are unfavorable to the procurement of electrochemical devices with exceptional efficiency. Herein, a facile approach was demonstrated for designing and synthesizing NiCo carbonate hydroxide (NCCH) nanoarchitecture by a hydrothermal method. The relative amounts of Ni/Co have been shown to significantly impact the physicochemical and electrochemical properties of the resulting materials. In particular, the material with a Ni/Co proportion of 2:1 (NCCH1) exhibits a linked architecture of 1D nanofiber and 2D microsheet. This nanoarchitecture offers numerous advantages, including offering additional active sites for redox reactions, shortening electron/ion transport paths, and alleviating the volume change during cycling. The optimized NCCH1 electrode exhibits a superior specific capacitance of 2408 F g−1 at a specific current of 1 A g−1, with excellent rate performance. Furthermore, the fabricated HSC attains a striking specific energy of 50.1 Wh kg−1 at a specific power of 805.6 W kg−1 while maintaining prominent cycling stability. Impressively, these findings suggest that the NCCH1 has excellent potential as a capable candidate for the fabrication of high-performance energy storage devices.

Multiscale Scrutinizing Ion Storage Kinetics in Hollow Ni‐Mn Prussian Blue Analogues for Enhanced Capacitive Deionization

AbstractPrussian blue analogues (PBAs) are a class of promising materials for capacitive deionization. However, the kinetic mismatch between their slow ion storage rate and the demand from short‐time desalination severely limits their desalination performance. Here, a group of structure‐tuneable Ni‐Mn PBAs have been developed by a combination strategy of surface‐protected chemical etching and Ostwald ripening to study their ion storage kinetics. Treating them as demos, the characterizations and investigations, e.g., in situ XRD in a three‐electrode system, dynamic impedance, finite element simulation, and DFT calculations etc., reveal that the slow ion diffusion caused by the severe agglomeration of the nanoparticles and the unsuitable lattice parameter controls the final desalination behavior. Therefore, the correspondingly optimized sample (HC‐t) possessing a microscale hollow structure, nanoscale shell thickness, and expanded lattice, displays a fast ion storage kinetics with the ratio of surface‐controlled current as high as 82% at a scan rate of 20 mV s−1. Consequently, it delivers an impressive desalination capacity of 120.8 mg g−1 (2.06 mmol g−1 Na+) with a fast average desalination rate of 0.25 mg g−1 s−1 (0.004 mmol g−1 s−1) at 1.2 V, competitive with those reported in the literature. Moreover, the elucidation of the structure‐performance correlation provides valuable insights for the development and design of next‐generation PBAs for capacitive deionization (CDI).

Microstructural evolution and investigation of mechanical properties of Al 7055 –Nano Si3N4 composites

In this paper an attempt has been made to develop the aluminium based metal matrix composites. Al7055 were chosen as base material and hard ceramic particulate nano silicon nitride as reinforcement. The composites were fabricated by using bottom pouring stir casting technique by varying weight percentage of Si3N4 in steps of (3 wt%, 6 wt% & 9 wt%) respectively and particle size of 30, 60 and 90nm. Morphological characterization of composites was conducted by using HRFESEM. The SEM result reveals that there is homogeneous distribution between the matrix and reinforcement. EDS mapping for prepared composites were done to identify the presence of alloying elements and phase distribution. XRD analysis is conducted for validation of the structural composition. Mechanical tests like tensile, micro Vickers hardness and impact test were performed on developed composites. The ultimate tensile strength of the composites at 9 wt% and particle size of 90 nm found to be diminishing due to severe agglomeration. The hardness value increases at 9 wt% and particle size of 30 nm. The toughness of the composites increased at 30 nm reinforcement size and 6 wt% as compared to higher weight percentage developed composites. Corrosion test were conducted as per ASTM G31 by weight loss method for different samples by dipping composite samples in 50 g Hcl solution for duration of 6 h and it was found that the corrosion resistance of the composites was higher while increasing the wt% of Si3N4 as compared to base matrix..

Mo4/3B2Tx induced hierarchical structure and rapid reaction dynamics in MoS2 anode for superior sodium storage

Molybdenum sulfide (MoS2) with large layer distance and high theoretical capacity has been identified as one of the most promising anodes for sodium ion batteries, but the poor intrinsic conductivity and severe structural agglomeration restricted its diffusion kinetic and specific capacity. In this work, the synergistic effect of heterogeneous interface and Na2S adsorption/conversion active sites was employed to construct Mo4/3B2Tx-MoS2@C composites using a self-assembly and calcination strategy. Theoretical calculation and experimental results demonstrated that the charge transfer and interface between Mo4/3B2Tx and MoS2 along with the 3D hydrangea-like structure improved the intrinsic conductivity and provided fast ion diffusion channels, boosting the electrochemical kinetics; while the favorable adsorption of Na2S and weakened Na-S bond at Mo4/3B2Tx-Mo interface optimized the recombination energies of Mo-S bond, accelerating the ion diffusion and enhancing the electrochemical reversibility. In addition, the copious sulfur vacancies provided additional active sites for ion storage, ameliorating the electrochemical capacity. As expected, the novel Mo4/3B2Tx-MoS2@C electrode delivered a satisfactory rate capacity (340.6 mAh g−1 at 1 A g−1) and durable cyclic performance (267.2 mAh g−1 after 600 cycles at 2 A g−1). When paring with Na3V2(PO4)3, the Mo4/3B2Tx-MoS2@C||Na3V2(PO4)3 full cell exhibited high energy densities of 234.0 and 131.7 Wh kg−1 at 215.7 W kg−1 and 4.4 kW kg−1, respectively. The proposed synergistic strategy of heterogeneous interface and Na2S adsorption/conversion active sites provided a new guidance for the rational design of transitional metal sulfide anodes for sodium ion batteries.

Hollow Stair-Stepping Spherical High-Entropy Prussian Blue Analogue for High-Rate Sodium Ion Batteries.

Prussian blue analogues (PBAs) are considered to be one of the most suitable sodium storage materials, especially with the introduction of the high-entropy (HE) concept into their structure to further improve their various abilities. However, severe agglomeration of the HEPBA particles still limits the fast charging capabilities. Here, an HEPBA (Nax(FeMnCoNiCu)[Fe(CN)6]y□1-y·nH2O) with a hollow stair-stepping spherical structure has been prepared through the chemical etching process of the traditional cubic structure of HEPBA. Electrochemical characterization (sodium ion battery), kinetic analysis, and COMSOL Multiphysics simulations reveal that the nature of the high-entropy and the hollow stair-stepping spherical structure can greatly improve the diffusion behavior of Na+ ions. Moreover, the hollow structure effectively mitigates the volume change of HEPBA during SIBs operation, ultimately extending the lifespan. Consequently, the as-prepared HEPBA cathode exhibits excellent rate performance (126.5 and 76.4 mAh g-1 at 0.1 and 4.0 A g-1, respectively) and stable long-term capability (maintaining its 75.6% capacity after 1000 cycles) due to its unique structure. Furthermore, the waste of the etching process can easily be recycled to prepare more HEPBA product. This processing method holds great promise for designing nanostructures of advanced high-entropy Prussian blue analogues for sodium ion batteries.

Facile and efficient fabrication of carbon nanotube reinforced epoxy vitrimers through dynamic crosslinking

AbstractCarbon nanotubes (CNT) is an ideal candidate for reinforced epoxy vitrimer composites, however, achieving a desirable improvement of the mechanical properties is a great challenge owing to CNT is extremely easy to aggregate. In this study, well‐dispersed CNT reinforced epoxy vitrimers, namely EVD/CNT, were prepared by combining ultrasonic dispersion and dynamic crosslinking techniques, using multiple wall carbon nanotube as reinforcement filler, sebacic acid as curing agent, diglycidyl ether of bisphenol A (DGEBA) as epoxy monomer, zinc acetylacetonate as transesterification catalyst, torque rheometer (internal mixer) as dynamic crosslinking equipment. The CNT reinforced epoxy vitrimers, namely EVS/CNT, were prepared using traditional static curing method. The structure and morphology, mechanical properties and stress relaxation behavior of EVS/CNT and EVD/CNT were comparatively investigated, and the influence of CNT content on the structure and properties of EVD/CNT prepared by dynamic crosslinking method were also studied. The results indicated that dynamic crosslinking technology can stably disperse CNT into epoxy vitrimer resin matrix under continuous shear force. However, CNT experienced severe secondary agglomeration during the static curing process. When the loading amount of CNT was 2 wt%, the tensile strength and elongation at break of EVD/CNT‐2 were 3.2 times and 2.2 times higher than those of EVS/CNT‐2, respectively. The Young's modulus and glass transition temperature (Tg) of EVD/CNT‐2 (6.43 ± 1.10 MPa, 29.6°C) were also higher than those of EVS/CNT‐2 (5.46 ± 0.31 MPa, 25.4°C). Moreover, dynamic crosslinking technology greatly shortened the reaction time of CNT reinforced epoxy vitrimers, improved production efficiency and reduced reaction energy consumption, and was expected to be used for large‐scale and industrial production.

Microstructure and mechanical properties of in-situ hybrid reinforced (TiB+TiC)/Ti composites prepared by laser powder bed fusion

To address the problems of insufficient strength and low hardness in pure titanium, a new Ti–B–C powder system was used to prepare in-situ hybrid reinforced (TiB + TiC)/Ti composites by laser powder bed fusion (LPBF) technology. The influence of different TiB/TiC ratios on the hybrid reinforcement was investigated. When the TiB/TiC ratio is 1:1, the best hybrid reinforcement effect is achieved and the mechanical interlocking structure is formed between TiB and TiC. The structures enhance the strength of (TiB + TiC)/Ti composites significantly. Subsequently, the microstructures and mechanical properties of (TiB + TiC)/Ti composites were investigated by adjusting different TiB + TiC contents. As the TiB + TiC content increases, the grains are refined significantly and transform into equiaxed grains eventually, the preferred orientation disappears. When the TiB + TiC content is too high, severe agglomeration of TiB + TiC occurs, resulting in less noticeable improvement in strength and a rapid decrease in plasticity. Finally, the heat treatment of (TiB + TiC)/Ti composites was carried out. TiB and TiC are uniformly distributed. TiC coarsens significantly, and TiB exhibits a dual-scale effect. The higher the heat treatment temperature, the more favorable it is to improve the plasticity of titanium matrix composites (TMCs). The TMC2 after HT950 has a tensile strength of 879 MPa and an elongation of 11.7%, exhibiting excellent comprehensive mechanical properties.