Material Dispersion Research Articles

Fe3O4 incorporated geopolymer nanocomposites for microwave absorption: Role of size, structure, and dispersion

The demand for sustainable construction materials with outstanding microwave absorbing properties is essential to provide comprehensive protection against the harmful effects of electromagnetic (EM) radiation. Herein, a series of Fe3O4-based materials with similar shapes, including Fe3O4 nanospheres with average sizes of 10 nm (Fe3O4-10) and 400 nm (Fe3O4-400) and hollow Fe3O4 nanospheres with an average size of 400 nm (H-Fe3O4-400), were synthesized. SiO2 was coated on the surface of Fe3O4-based materials. Geopolymer (GP) nanocomposites containing different Fe3O4-based materials were prepared. The roles of the size, structure, and dispersion of Fe3O4-based materials on the microwave absorption and compression properties of GP nanocomposites were comprehensively explored. Owing to the hollow structure and heterointerface formed, GP nanocomposites containing H-Fe3O4-400 displayed outstanding microwave absorption performance with a minimum reflection loss (RLmin) of −39.3 dB at 2.2 mm and an effective absorption bandwidth (EAB) of 4.8 GHz. More importantly, radar cross section (RCS) simulation was conducted to demonstrate the outstanding microwave attenuation capability of H-Fe3O4-400/GP nanocomposites in a real service environment. The results showed that the performance of GP nanocomposites was more competitive than that of other similar microwave absorbing construction materials. Furthermore, the compression tests showed that the introduction of H-Fe3O4-400 decreased the compressive strength of the GP nanocomposites from 37.87 to 31.62 MPa, while the presence of SiO2 enhanced interfacial load transfer, increasing the compressive strength to 37.16 MPa. The overall results validated that the as-prepared GP nanocomposites can be a potential candidate for use in construction areas where microwave absorption is essential.

Commercially important mangrove crabs are more susceptible to microplastic contamination than other brachyuran species

Brachyuran crabs are ecologically and economically important macrofauna in mangrove habitats. However, they are exposed to various contaminants, including plastics, which bioaccumulate in relation to their feeding modes. Setiu Wetlands is a unique place on the east coast of Peninsular Malaysia where different ecosystems such as mangroves, lagoon, beaches, etc., are duly connected and influencing each other. In recent years, the shifted river mouth has threatened these wetlands, causing severe hydrodynamic changes in the lagoon, especially in the core mangrove zone. The present study tested microplastics (MPs) contamination in the mangroves through brachyuran crabs as indicators. Three sampling sites, namely Pulau Layat, Kampung Pengkalan Gelap, and Pulau Sutung were chosen. The four abundant crab species Parasesarma eumolpe, Metaplax elegans, Austruca annulipes, and Scylla olivacea, which display different feeding behaviours were collected from all sites covering the dry (Feb–Mar 2021) and the wet (Dec 2021–Jan 2022) seasonal periods. There were significant differences in the seasonal abundance of MPs among crab species. The highest accumulation of MPs in the crab stomachs in the dry season could be linked to subdued water circulation and poor material dispersion. Besides the lower MPs in the wet period due to improved water exchange conditions, its significant presence in the stomachs of S. olivacea indicates the role of its feeding behaviour as a carnivore. In addition, the micro-Fourier transform infrared spectroscopy (micro-FTIR) revealed the widespread occurrence of polymers such as rayon and polyester in all species across the sites. Given the fact that crabs like S. olivacea are commercially important and the ones contaminated with MPs can cause detrimental effects on the local community's health, further managerial actions are needed to assure sustainable management of the Setiu Wetlands.

Plasma dynamic synthesis of dispersed metal oxide materials in CO2 medium

The steadily high interest in metal oxides, including in the form of fine powders, has led to a rapid increase in their production, the search for new synthetic methods and the expansion of possible applications. CO2 has proven itself as a cheap and abundant source of mild oxidant, which can potentially be used for oxidation reactions. However, the key problem of CO2 application is the necessity to break the bonds of the CO2 molecule that requires a large amount of energy. This work presents a fundamentally new approach for metal oxide synthesis, when applying CO2 as a gaseous precursor and oxidant, based on application of a pulsed arc discharge plasma of the electroerosion type. The implementation of the proposed method called plasma dynamic synthesis results in obtaining dispersed metal oxides that is demonstrated by the examples of Cu–O, Fe–O, Ti–O and Al–O systems. The influence of the metal-containing plasma type and operation modes on the formation of metal-oxide dispersed materials is studied. The multi-pulse operation mode in the considered system with titanium and aluminum electrodes provides obtaining almost completely oxidized products that is found to depend on the electronegativity of the initial metals. When applying aluminum electrodes, the process not only provides a high productivity of obtaining dispersed materials (up to 15 g per cycle), but also allows the CO2 conversion rate of up to 14.5%. Moreover, the electroerosion plasma demonstrates the energy efficiency of CO2 decomposition exceeding other plasma-based methods due to ongoing exothermic reactions of metal oxide formation. The as-synthesized products can be used to obtain bulk ceramic materials that is shown by the example of aluminum oxide powders. The hardness of the obtained ceramic specimens produced by SPS method is found to be ∼22 GPa and correlates with the best samples for aluminum oxides.

CALCULATION AND INVESTIGATION OF THE CUTTING PROCESS FOR IMPROVING THE DURABILITY OF KNIVES OF STRAW CHOPPER-SPREADER

For the disposal of the non–grain part of the heap of various crops in modern combines, they are crushed, as a rule, by a special unit – a shredder-a straw spreader. During its operation, the crushed straw is scattered across the field, while the scattering width is regulated structurally and technologically depending on the width of the harvester's reaper, the speed of movement, the rotor speed. The quality of fragmentation and dispersion of plant material depends on the condition of the working organs of the shredder-straw spreader – its knives, with wear and blunting of which the basic parameters of agricultural technology deteriorate, energy consumption increases, losses increase. (Research purpose) The research purpose is calculation and theoretical investigation of the cutting process of the shredder-straw spreader, as well as determining the dependence of the thickness of the knife blade on the height of the compressible (cut) layer. (Materials and methods) Adopted spring wheat straw as the cut material. We took the straw shredder-spreader of the Acros-590 Plus combine harvester equipped with original knives from MWS (Germany) as the unit under study. Calculations of the optimal thickness of the blade of the straw shredder-spreader knife from the height of the layer of the non-grain part of the pile entering it were performed. (Results and discussion) Studies have shown that at different heights of the initial layer, its cutting with a knife with a cutting edge thickness of 100 micrometers occurs when a compression height of 1.4 millimeters is reached for a layer of 2 millimeters and 99.4 millimeters for a layer of 100 millimeters. The compression value of the initial two–millimeter layer when it is cut will be 30 percent (the multiplicity or compression ratio of the CSF is about 1.3 times), and for the initial hundred-millimeter layer - 0.6 percent (the compression ratio is about 0.03 times). (Conclusions) It is advisable to sharpen the blade for technological reasons and the existing design of the knife IRS combines PCM (Acros-590 Plus) to a thickness of 100 µm or more.

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes Enabled by a Graphite Conductive Additive.

Cobalt-free cation-disordered rocksalt (DRX) cathodes are a promising class of materials for next-generation Li-ion batteries. Although they have high theoretical specific capacities (>300 mA h/g) and moderate operating voltages (∼3.5 V vs Li/Li+), DRX cathodes typically require a high carbon content (up to 30 wt %) to fully utilize the active material which has a detrimental impact on cell-level energy density. To assess pathways to reduce the electrode's carbon content, the present study investigates how the carbon's microstructure and loading (10-20 wt %) influence the performance of DRX cathodes with the nominal composition Li1.2Mn0.5Ti0.3O1.9F0.1. While electrodes prepared with conventional disordered carbon additives (C65 and ketjenblack) exhibit rapid capacity fade due to an unstable cathode/electrolyte interface, DRX cathodes containing 10 wt % graphite show superior cycling performance (e.g., reversible capacities ∼260 mA h/g with 85% capacity retention after 50 cycles) and rate capability (∼135 mA h/g at 1000 mA/g). A suite of characterization tools was employed to evaluate the performance differences among these composite electrodes. Overall, these results indicate that the superior performance of the graphite-based cathodes is largely attributed to the: (i) formation of a uniform graphitic coating on DRX particles which protects the surface from parasitic reactions at high states of charge and (ii) homogeneous dispersion of the active material and carbon throughout the composite cathode which provides a robust electronically conductive network that can withstand repeated charge-discharge cycles. Overall, this study provides key scientific insights on how the carbon microstructure and electrode processing influence the performance of DRX cathodes. Based on these results, exploration of alternative routes to apply graphitic coatings is recommended to further optimize the material performance.

Fabrication of methyl parathion electrochemical sensor based on β-cyclodextrin decorated single-wall carbon nanotubes

ABSTRACT Herein, an efficient and sensitive methyl parathion (MP) electrochemical sensor was fabricated by using β-cyclodextrin (β-CD) decorated single-wall carbon nanotubes (SCN), which were used to modify the glassy carbon electrode (GCE). The β-CD@SCN/GCE sensor achieved the sensitive MP detection. For the obtained β-CD@SCN nanocomposite, SCN could form three-dimensional reinforced carbon conductive network with good conductivity property and efficient charge transport channels; β-CD could promote the dispersion of carbon materials and boost the accumulation capability of MP on the surface of β-CD@SCN/GCE. The combination of β-CD and SCN significantly optimized the electrochemical property of β-CD@SCN/GCE sensor for the detection of MP. The β-CD@SCN/GCE sensor exhibited good MP electrochemical detection performance with low limit of detection of 7.23 nM. When used for the detection of MP in grape juice, the β-CD@SCN/GCE sensor exhibited good MP electrochemical sensing analysis performance with satisfactory recovery rates (96.54–98.18%) and relative standard deviation values (1.60–2.07%).

A Generic and Effective System Dispersion Compensation Method: Development and Validation in Visible-Light OCT

Compared with optical coherence tomography (OCT) in the near-infrared domain, the visible-light OCT (vis-OCT) system affords a higher axial resolution for discerning subtle pathological changes associated with early diseases. However, the significant material dispersion at the visible-light range leads to a severe problem for dispersion management in vis-OCT systems, which results in a compromised axial resolution. While dispersion compensators (such as prism pairs) are commonly used, a digital method is still highly desirable and has been widely used to compensate for the residual dispersion imbalance between the reference and sample arms in an OCT system. In this paper, we develop a generic approach to effectively compensate for the system dispersion, especially the higher-order dispersion in the vis-OCT system, by using a single arbitrary measurement of the mirror-reflection (SAMMR) method and its resulting phase information. Compared with the previous methods, including the method based on the Taylor series iterative fitting and differential method, the proposed method does not need to extract the dispersion coefficients or use the metric functions and affords a better performance for axial resolution and the signal-to-noise ratio in vis-OCT systems. Its effectiveness is further validated in an OCT system operating in the near-infrared domain.

Electrochemical properties and performance of a flexible polysiloxane-based ionic conductor as a binder for LiFePO4 cathode

Poly(methyl(2-(tris(2-H methoxyethoxy)silyl)ethyl)siloxane)) modified with Si-tripodant centers (2550EO) and integrated amide salt (LiF(SO2CF3)2 (LiTFSI)) has been used as a binding agent in the lithium-ion batteries containing LiFePO4 (LFP). The performance of the cathode produced using 2550EO/LiTFSI was evaluated using X-ray diffraction, scanning electron microscope, and electrochemical measurements. The electrochemical performance of the LFP cathode using 2550EO/LiTFSI was compared to alternative binders, such as Polyvinylidene fluoride (PVDF), Polyethylene oxide (PEO), and 2550EO, at 25 °C and 60 °C, respectively. By using 2550EO/LiTFSI as a binder in LFP/Li battery preparation, the rate capability and cycle stability of the LFP cathode is significantly enhanced. The enhanced performance is attributed to the formation of a thin, solid-electrolyte interface (SEI) on the electrodes, the uniform dispersion of active and conductive materials throughout the electrode, and the adhesion capability of 2550EO#LiTFSI/LFP to the Al current collector, which increases the electronic conductivity of the LFP cathode.

Observations of two-dimensional turbulence in the surfzone

Low-frequency, many-minute-period horizontal surfzone eddies are an important mechanism for the dispersion of material, transporting larvae, pollutants, sediment, and swimmers both across and along the nearshore. Previous numerical, laboratory, and field observations on alongshore uniform bathymetry with no or roughly uniform mean background flows suggest that the low-frequency eddies may be the result of a two-dimensional inverse energy cascade that transfers energy from relatively small spatial-scale vorticity injected by depth limited breaking waves to larger and larger spatial scales. Here, using remotely sensed high-spatial resolution estimates of currents, those results are extended to surfzones with strong complex mean circulation patterns [flows O(1 m/s)] owing to nonuniform bathymetry. Similar to previous results, wavenumber spectra and second-order structure functions calculated from the observations are consistent with a two-dimensional inverse energy cascade. The size of the largest eddies is shown to depend on the surfzone width and the spatial scales of the mean currents. Third-order structure functions also are consistent with an inverse cascade for spatial scales greater than ∼50 m. At smaller scales, the third-order structure functions suggest a mixture of inverse and forward cascades.

Atomic Ru coordinated by channel ammonia in V-doped tungsten bronze for highly efficient hydrogen-evolution reaction

Regulation of the atomic distribution is crucial for the development of atomically dispersed electrocatalysts. In this study, atomic Ru coordinated by channel ammonia in V-doped tungsten bronze (Ru/V-NHWO, Ru 0.44 wt%, V 0.45 wt%) was used as a high-performance catalyst for the hydrogen evolution reaction (HER), demonstrating remarkable mass activity in a wide pH range. Atomic Ru with a regulated spatial distribution and electronic structure was achieved owing to its unique coordination with the ammonia species in the hexagonal channels of V-NHWO. V doping in NHWO led to enhanced intrinsic activity and conductivity. Theoretical calculations revealed that the multichannel, vertically integrated Ru sites in the V-doped channels, as well as the coexisting Ru sites without multichannels or V-doping, improved the free energy of water dissociation and hydrogen sorption, which boosted the HER activity. Our study paves a new way for constructing atomically dispersed materials with a regulated spatial distribution for diverse applications.

ПРОГНОЗУВАННЯ НЕСУЧОЇ СПРОМОЖНОСТІ ПЛИТНОГО ФУНДАМЕНТА ЗА ЧИСЛОВИМ МЕТОДОМ ГРАНИЧНИХ ЕЛЕМЕНТІВ

Construction is one of the leading branches of the national economy in the historical aspect of its development. The first design task is to determine the strength of building structures. Therefore, the study of the stress-strain state and related calculations are the most important in construction. The purpose of studying soil mechanics and foundation construction techniques is the calculation and construction of structures on or in soil. The main task is the construction of structures with a sufficient degree of reliability.The selection of an adequate theoretical model remains the main problem of soil mechanics. Indeed, the deformation of the dispersed granular material of the soil takes place during the mutual sliding of the grains, the rheology of the soil is complex, as evidenced by a large amount of experimental material. Today, the path of development of soil mechanics is related to the study of problems within the framework of the elastic-plastic dilatation model and the improvement of this model based on experiments. A mathematical model of a technical object at the micro level is a system of differential equations in partial derivatives, the exact solution of which can be obtained only in a few partial cases, therefore a discrete model is built using numerical methods that use the Poisson idea that the behavior of a complex model can be represented by the behavior of its individual component elements. The intensive development and widespread use of computers significantly brought fundamental mathematical problems closer to applied ones, and strengthened their mutual influence.The emergence of a new, powerful and general method of research - a numerical experiment, more than ever before closely connected the physical content of the problem, its mathematical formulation, numerical methods of calculation and modern computers. The work uses the numerical method of boundary elements. A promising way to develop foundations and foundation structures is to use the ratios of the theory of plastic flow, and the level of development of soil mechanics significantly affects the economy and reliability of the decisions made.

OBTAINING BULK PRODUCTS FROM CU-SIC METAL-MATRIX COMPOSITE FOR ENERGY-EFFICIENT HEAT-CONDUCTING SYSTEMS

Link for citation: Nikitin D.S., Shanenkov I.I., Nassyrbayev A., Vympina Yu. N., Orlova E.G., Ivashutenko A.S., Sivkov A.A. Obtaining bulk products from Cu-SiC metal-matrix composite for energy-efficient heat-conducting systems. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 93-101. In Rus. The relevance of the research is associated with the rapid development of modern high-performance computing systems, superneurocomputers and artificial intelligence devices. Today such development is held back largely due to the lack of an effective cooling system for high-power elements of their structures. Composite materials Cu-SiC with improved physical, mechanical and thermophysical characteristics can be used to solve problems of heat removal intensification. The main aim of the research is to obtain bulk products from metal-matrix composite Cu-10% SiC with improved physical, mechanical and thermal characteristics by spark plasma sintering. Objects of the research are bulk products from metal-matrix composite Cu-10%SiC. The samples were obtained by spark plasma sintering at temperatures of 700, 750, 800, 850 °C and a pressure of 60 MPa. Methods: spark plasma sintering, X-ray diffractometry (X-ray phase analysis), scanning electron microscopy, indentation, laser flash method. Results. Experimental studies have been carried out to obtain bulk metal-matrix composites with a copper matrix and the addition of reinforcing superhard particles of silicon carbide Cu-10%SiC. The compaction of dispersed composite materials was carried out by spark plasma sintering at various temperatures of 700, 750, 800, and 850 °C. The microstructure and composition of initial dispersed materials and final bulk products have been studied. It is shown that the spark plasma sintering method has advantages for obtaining relatively dense materials with high physical, mechanical and thermal properties. Analysis of the obtained samples showed the formation of a dense (up to ~88 %) homogeneous fine-grained composite structure. The greatest densification of the material is achieved at the highest sintering temperature of 850 °C, which causes this sample to demonstrate the maximum hardness (H=3,63 GPa) and Young's modulus (E=159,63 GPa), as well as the thermal conductivity at room temperature (λ=223 W/m K). The obtained composite materials can be used as structural and functional materials for energy-efficient heat-conducting systems.

Role of Rheology in Morphology Development and Advanced Processing of Thermoplastic Polymer Materials: A Review.

This review presents fundamental knowledge and recent advances pertaining to research on the role of rheology in polymer processing, highlights the knowledge gap between the function of rheology in various processing operations and the importance of rheology in the development, characterization, and assessment of the morphologies of polymeric materials, and offers ideas for enhancing the processabilities of polymeric materials in advanced processing operations. Rheology plays a crucial role in the morphological evolution of polymer blends and composites, influencing the type of morphology in the case of blends and the quality of dispersion in the cases of both blends and composites. The rheological characteristics of multiphase polymeric materials provide valuable information on the morphologies of these materials, thereby rendering rheology an important tool for morphological assessment. Although rheology extensively affects the processabilities of polymeric materials in all processing operations, this review focuses on the roles of rheology in film blowing, electrospinning, centrifugal jet spinning, and the three-dimensional printing of polymeric materials, which are advanced processing operations that have gained significant research interest. This review offers a comprehensive overview of the fundamentals of morphology development and the aforementioned processing techniques; moreover, it covers all vital aspects related to the tailoring of the rheological characteristics of polymeric materials for achieving superior morphologies and high processabilities of these materials in advanced processing operations. Thus, this article provides a direction for future advancements in polymer processing. Furthermore, the superiority of elongational flow over shear flow in enhancing the quality of dispersion in multiphase polymeric materials and the role of extensional rheology in the advanced processing operations of these materials, which have rarely been discussed in previous reviews, have been critically analyzed in this review. In summary, this article offers new insights into the use of rheology in material and product development during advanced polymer-processing operations.

Reducing radar cross section of flat metallic targets using checkerboard metasurface: Design, analysis, and realization

Aiming at the large-scale application of metasurface in the field of radar stealth, we present a hybrid resonance-based and dispersion substrate integrated checkerboard metasurface (CMS) for reducing the radar cross section (RCS) of flat metallic targets. Considering the frequency-dependent characteristics of such a dispersion material, a pair of single and dual resonant artificial magnetic conductor meta-atoms with the modified “crusades-like” cell topologies is employed to maximize the operating bandwidth; besides, a comprehensive and thorough investigation on the resonance mechanism is conducted in this paper to provide an intuitive physical insight of meta-atoms’ reflection responses. By comparing the predicted results with simulations, the quasi-periodic effect is introduced to explain the frequency shift of 10 dB RCS reduction bandwidth. In the implementation procedure, a prototype of the designed RCS reducer with a total dimension of 180 × 180 mm2 is fabricated and measured, the 10 dB RCS reduction bandwidth of theoretical simulation and experimental measurement are basically consistent, and the performance improvement of 8 dB RCS reduction in the experimental results can be attributed to the dispersion effects of the dielectric substrate. With a better figure of merit, our efforts may serve as a useful exemplar for the economical CMS architecture in radar evasive applications.

Triple signal-enhancing sandwich-type electrochemical immunosensor based on Au@SNHC and PtPdCu/BNC for detection of Cardiac Troponin I

A novel multiple amplification strategy for electrochemical immunoassay was developed elaborately. The realization of this strategy is based on the high efficiency catalysis of boron nitrogen double-doped carbon loaded trimetallic PtPdCu mulberry-like nanospheres (PtPdCu/BNC) and the satisfactory conductivity of gold nanoparticles modified with sulfur nitrogen co-doped hollow porous carbon (Au@SNHC). Single crystal anisotropic Pt octahedral seeds were synthesized with sodium citrate as shape-directing agent, and then three metals were grown in situ to prepare the trimetallic PtPdCu mulberry nanospheres, which had excellent utilization of atoms and a significant number of catalytic active centers. Boron nitrogen double-doped carbon (BNC) with abundant free electrons and high electron density micro-mesoporous can be used as the supported dispersion material of PtPdCu MBNSs, further catalytically enrich H2O2. Moreover, the etching vulcanization of small ZIF template and the co-doping of sulfur and nitrogen endow sulfur nitrogen co-doped hollow porous carbon (SNHC) with shorter the diffusion distance of charge carrier and lower mass transfer resistance. Under optimal conditions, the developed immunosensor exhibits good sensing performance with a detection limit of 4.27 fg⋅mL−1, and the wide linear dynamic range (10 fg⋅mL−1–100 ng⋅mL−1). This study provides a possible strategy for early diagnosis and postoperative monitoring of AMI.

Genetic-Algorithm-Based Design of Large-Mode- Area All-Solid Anti-Resonant Fiber With Normal Dispersion and Single-Mode Operation in the 2 μm Wavelength Region

Recent years have witnessed much progress in the development of fiber lasers in the 2 μm region. Yet, to date, their power levels are limited by modulation instability and soliton formation attributed to the strong anomalous dispersions of fused silica in this wavelength region. Further power scaling requires a novel design of an all-solid silica active fiber that features normal dispersion by compensating the material dispersion with the waveguide dispersion. At the same time, a large mode area, low losses, single mode operation and robustness need to be maintained. In this paper, we propose an all-solid anti-resonant fiber (AS-ARF) design that meets these demands. We demonstrate that normal dispersion can be achieved in AS-ARFs at 2 μm by exploiting the Kramers-Kronig relation. To balance the desired dispersion with the other performance parameters, we optimize the design of the AS-ARFs using a genetic algorithm. The optimized AS-ARF has a mode field area of 1170 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and normal dispersion over the spectrum from 1.96 μm to 2.04 μm. Within this spectrum, the maximum confinement loss (CL) of the fundamental mode (FM) is 16 dB/km and the minimum CL of the higher order modes (HOMs) is over 100 dB/km. The HOMs can be easily coupled out by bending the fiber while the FM stays in the core. For example, the CLs are over 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> dB/km for the HOMs and below 200 dB/km for the FM at 2 μm at a bending radius of 20 cm. Moreover, the properties of the proposed AS-ARF remain favorable even under large geometric variations, showing good tolerance to manufacturing errors. We expect the proposed AS-ARF to further stimulate the development of high-power fiber lasers in the 2 μm region.

Mechanism of pin thread and flat features affecting material thermal flow behaviors and mixing in Al-Cu dissimilar friction stir welding

Three different features of pin models in Al-Cu dissimilar friction stir welding processes are established to analyse the effects of threads and flats on the two-phase material thermal flow behaviors. Based on computational fluid dynamics (CFD), a simulation methodology that calculates pins with complex morphologies through an adaptive force boundary is proposed. The pin characteristics are gradually optimized from “conical contour” to “conical-thread” and then to “thread-flats”. For dissimilar Al-Cu materials, the physical properties are weighted by the volume fractions of two-phase materials in the mixing zone. To build a dynamic adaptive contact model that varies with the material flow state, the interfacial friction shear stress is calculated by using the relative slip between the tool and material. The linkage effects between the “thread + flats” on the dissimilar Al/Cu welding mechanisms are systematically analysed. The enhancing mechanisms of the thread and flats on the material flow are different. The thread mainly reinforces the longitudinal migration of the Al/Cu materials, which is perpendicular to the horizontal plane. The flats effectively expand the plastic flow range and material mixing zone on the horizontal plane. These flow expanding effects are observed on the Z = 1 mm plane since the radial range of material flow enlarges from 2 mm to 3 mm under the action of the flats, while the horizontal flow range undergoes little change with the thread. The coupled mechanism of the “thread + flats” shows 0.06 s periodic strengthening, and the fluctuation threshold of the material flow velocity is wider, significantly improving the upwards stirring of the bottom material. The enhanced horizontal flow and vertical migration are beneficial to the uniform dispersion of the second-phase material (Cu) and local material softening for the formation of Al-Cu heterogeneous joints. Moreover, the accuracy of the model is verified by comparing the simulated and experimental TMAZ boundaries.

A novel coating strategy for graphene-modified Li1.2Mn0.54Ni0.13Co0.13O2 as cathode material for LIBs

In this study, reduced graphene oxide (RGO) coated Li1.2Mn0.54Co0.13Ni0.13O2 (RGO@LMNCO) materials with different amounts of RGO were synthesized using a facile hydrothermal method. The double electron layer on the graphene surface was opened by adding a certain amount of electrolyte（NaCl）to the solution to increase the activity of the graphene, thus contributing to the uniform dispersion of the nano-cathode material on the RGO and reducing the secondary agglomeration. The physical characterization and electrochemical test results confirmed that LMNCO material with 2 wt% RGO (2 wt%RGO@LMNCO) was most uniformly dispersed on RGO and exhibited the optimal overall electrochemical performance. The above result suggested that this strategy can be more conductive to exerting the superiority of RGO coating. RGO coating enhanced electronic and ionic conductivity while modifying the potential energy surface of LMNCO effectively and suppressing surface oxygen loss. Subsequently, it can be beneficial to avoid side reactions between the cathode material surface and the electrolyte. As a result, the surface stability of cathode materials was increased. The 2 wt%RGO@LMNCO electrode exhibited a maximum capacity of 308.7mAh g−1 at 0.2 C. With the increase of the charge/discharge current rate from 0.2 C to 10 C, it still reached 112.3mAh g−1. After 50 cycles at 0.2 C rate, the discharge capacity was decreased from 287.5 to 284.8 mAh·g−1, thus maintaining a capacity retention of 99.06%. Furthermore, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to analyze the synthesized sample. The main reason for enhanced electrochemical performance is that the RGO-LMNCO synthesized by the novel coating strategy, which can more effectively exert the modulation effect of graphene on the cathode material surface, exhibits better dispersion and uniform coating.

Transporting Dispersed Cylindrical Granules: An Intelligent Strategy Inspired by an Elephant Trunk

Manipulating granular materials is a crucial function of robotic grippers. However, the existing approaches always suffer from low efficiency when dealing with large quantities of dispersed granules. To overcome this challenge, inspiration is drawn from an African elephant (Loxodonta Africana), which can employ both fingertip extensions on the trunk tip to efficiently grasp dispersed granular food all at once by mediating state transition of granules. Herein, this bio‐inspired intelligent strategy is integrated into a soft pneumatic gripper for transporting dispersed granules. To evaluate the critical actuation pressures while grasping granules, a library is constructed experimentally, and the effects of the initial relative height and relative lifting speed on the grasping success rate are examined. It is indicated in the experimental results that this trunk‐inspired robotic strategy leads to a success rate of over 90% and saves ≈50% duration of manipulation compared to the individual gripping fashion. Herein, new insights may be offered in this study into a novel manipulation strategy for efficiently transporting dispersed granular materials.

Physical compensation method for dispersion of multiple materials in swept source optical coherence tomography.

An ophthalmic swept source-optical coherence tomography (SS-OCT) system based on a high-speed scanning laser at 1060 nm with a scanning rate of 100 KHz is constructed. Since the sample arm of the interferometer is comprised of multiple glass materials, the ensuing dispersion severely degrades imaging quality. In this article, second-order dispersion simulation analysis for various materials was performed first, and dispersion equilibrium was implemented utilizing physical compensation methods. After dispersion compensation, an imaging depth in air of 4.013 mm was achieved in model eye experiments, and signal-to-noise ratio was enhanced by 11.6%, with a value of 53.8 dB. In vivo imaging of the human retina was performed to demonstrate structurally distinguishable retinal images, characterized by an axial resolution improvement of 19.8%, with a value of 7.7 μm close to the theoretical value of 7.5 μm. The proposed physical dispersion compensation method enhances imaging performance in SS-OCT systems, enabling visualization of several low scattering mediums.