Dendritic Structure Research Articles

Directionally solidified NiCoCrFeAlW eutectic high-entropy alloy: Microstructure and mechanical properties

The NiCoCrFeAlW eutectic high-entropy alloy exhibits a balanced combination of ductility and strength. This study examines the microstructure evolution and mechanical properties of the Ni30Co30Cr10Fe10Al18W2 alloy at varying growth velocities (10, 20, 50, 100, and 200 μm/s), which in its as-cast state, features a microstructure that includes both coarse dendrites and lamellar eutectic. The structure of the coarse dendrites is characterized by an ordered body-centered cubic (B2) phase, while the lamellar eutectic, features a combination of face-centered cubic (FCC) and ordered B2 phases. The microstructure, characterized by lamellar and dendritic structures that are parallel to the growth direction after directional solidification, undergoes a morphological transition at the solid-liquid interface from a planar to a dendritic form as growth velocity increases. The tensile fracture strength initially increases with the growth velocity, reaching a peak of 1286 MPa at a velocity of 50 μm/s, and then subsequently decreases as the growth velocity continues to increase. Directional solidification results in an increase in sample elongation with increasing growth velocity, achieving an elongation of 22.5% at 200 μm/s. An examination of the deformation mechanism reveals that the lamellar structure, composed of the more ductile FCC phase and the harder B2 phase, effectively harmonizes the plasticity and strength of the alloy. Therefore, directional solidification significantly adjusts the eutectic microstructure's orientation, thereby enhancing the mechanical properties along the direction of solidification.

Understanding of additively manufactured material cyclic behavior at the grain scale by neutron diffraction and crystal plasticity modelling

Additive manufacturing (AM) offers distinct advantages in terms of complexity, reduced material waste, and shorter production times. However, the microstructures of AM alloys differ significantly from conventionally manufactured ones, and their impact on grain behavior remains uncertain. This study employs neutron diffraction, coupled with Crystal Plasticity Finite Element (CPFE) modeling, to investigate microstructural effects on cyclic behavior in 316L LPBF alloys. Neutron diffraction provides high-resolution strain and stress data at the polycrystalline level during loading, offering valuable insights into grain behavior. The CPFE model is initially validated at the grain scale using neutron diffraction, demonstrating its ability to predict local mechanical behavior in additively manufactured materials. This methodology holds promise for broader applications in various AM alloys, particularly when macroscopic identification of mechanical behavior is insufficient. Furthermore, the comparison between neutron diffraction and CPFE predictions allows to identify the influence of dendrites and dislocation substructures on the mechanical behavior at the grain scale. Notably, the micromechanical anisotropy resulting from dislocation organization along dendritic structures with specific orientations is highlighted. This study shows that despite the observed anisotropy, experimental measurement of intragranular strain distribution are correctly captured with a quantification of the deviation observed on some specific orientations due to the above cited microstructure sub-structures.

Evaluation of electrodeposition synthesis of gold nanodendrite on screen-printed carbon electrode for nonenzymatic ascorbic acid sensor

Gold nanodendrite (AuND) is a type of gold nanoparticles with dendritic or branching structures that offers advantages such as large surface area and high conductivity to improve electrocatalytic performance of electrochemical sensors. AuND structures can be synthesized using electrodeposition method utilizing cysteine as growth directing agent. This method can simultaneously synthesize and integrate the gold nanostructures on the surface of the electrode. We conducted a comprehensive study on the synthesis of AuND on screen-printed carbon electrode (SPCE)-based working electrode, focusing on the optimization of electrodeposition parameters, such as applied potential, precursor solution concentration, and deposition time. The measured surface oxide reduction peak current and electrochemical surface area from cyclic voltammogram were used as the optimization indicators. We confirmed the growth of dendritic gold nanostructures across the carbon electrode surface based on FESEM, EDS, and XRD characterizations. We applied the SPCE/AuND electrode as a nonenzymatic sensor on ascorbic acid (AA) and obtained detection limit of 16.8 μM, quantification limit of 51.0 μM, sensitivity of 0.0629 μA μM−1, and linear range of 180–2700 μM (R2 value = 0.9909). Selectivity test of this electrode against several interferences, such as uric acid, dopamine, glucose, and urea, also shows good response in AA detection.

An in-depth study of the synthesis of ReSe2 for anisotropic Raman characteristics

Abstract Two-dimensional transition metal dichalcogenides (TMDs) have received more interest for their potential role in future electronic and optoelectronic applications. Unlike other TMDs, Rhenium diselenide (ReSe2) stands out for its distinctive anisotropic growth characteristics. These unique features arise from its low lattice symmetry and interlayer decoupling, this has sparked significant interest among researchers. Previous research has indicated the presence of various growth patterns, including dendritic formations and structures resembling flowers. In this study, we effectively produced ReSe2 using the ‘Tilting Boat’ method to achieve growth on a 21 μm scale. Through precise manipulation of the growth conditions, we successfully attained flakes of 21 μm scale in comparison to prior findings. Moreover, we successfully produced a variety of shapes, including triangles, diamonds, and hexagons, on 1 × 1 cm2 Si/SiO2 substrates. Furthermore, we achieved the successful production of a continuous ReSe2 film on a 1 × 3 cm2 Al2O3 substrate. We verified the distinct anisotropic properties of ReSe2 via Raman Spectroscopy. Furthermore, we acquired three-dimensional visual representations of ReSe2 flakes and continuous films via SEM measurements. By employing EDS data and analysing x-ray photoelectron spectroscopy spectra, we have established a compositional ratio of 1:2 for Re and Se, which aligns with the MX2 structure. This confirmation indicates the successful synthesis of high-quality ReSe2 flakes.

Microstructural evaluation and optimization of wear behaviour of vacuum arc melted AlFeCrNiSi high entropy alloy

High-entropy alloys (HEA) are equiatomic, multi-element systems that, while having several elements with various crystal geometries to form a single phase. In this study, a novel equiatomic AlFeCrNiSi HEA is prepared using the vacuum arc melting process. The resulting microstructure featured dendritic and inter-dendritic structures with formations of intermetallic compounds such as Al₃Fe₂Si, NiAl, and AlCrNi phases. EDS analysis confirmed the presence of alloying elements and EBSD analysis revealed refined grains with an average size of 1 ± 0.15 µm size. Pin-on-Disc wear test with varying test parameters is conducted to optimize the wear parameters. Signal-to-noise ratio and analysis of variance identified the most significant wear parameters, with load being the most influential, followed by sliding distance and velocity. The wear rate is minimum at the lowest conditions of applied load, sliding distance, and sliding velocity. The improved microhardness also contributed to the improved wear resistance of the cast alloy. The subsequent worn morphology revealed the formation of grooves, microcracks, and oxide layers on the worn surface.

Interpretation of plastic deformation of copper particles in silver

The role of interfaces in metal matrix composites of Cu-Ag alloys deformed in tension is studied. Five types of samples are considered: alloys prepared by traditional casting and alloys compacted by spark plasma sintering are completed with pure elements, copper and silver. Due to more pronounced interfaces in the cast alloys, plastic deformation occurs at higher stresses and hence the dendritic structures of cast alloys are less suitable for applications.

Growth of dendritic CuS nanostructures for photoacoustic image guided Chemo-Photothermal therapy

Herein, we report a unique method for design and development of carboxyl enriched dendritic CuS nanostructures (CuS NSs) for photoacoustic image guided chemo-photothermal therapy. The dendritic network was grown on the surface of CuS nanoparticles via layer-by-layer assembly of amino acid. XRD and TEM studies established the formation of crystalline well-spherical nanosized hexagonal covellite (CuS) phase. The successful growth of dendritic structure was apparent from the rise in surface charge, hydrodynamic diameter and characteristic vibrational band intensity of peptide bonds. The developed different generations of dendritic CuS NSs (D0-CuS NSs, D1-CuS NSs, D2-CuS NSs and D3-CuS NSs) displayed wide-ranging absorption band in near infrared (NIR) zone and exhibited good photothermal heating efficacy upon irradiation of 980 nm laser light. From in to vitro cellular studies, it has been found that the NIR irradiation effectively enhanced the photothermal toxicity of D3-CuS NSs towards cancer cells. Moreover, these negatively charged water-dispersible D3-CuS NSs were conjugated with positively charged anticancer drug, doxorubicin hydrochloride (DOX) through electrostatic interaction. The DOX loaded D3-CuS NSs (DOX@D3-CuS NSs) revealed pH dependent drug release behaviour and their considerable uptake in breast cancer cells (MCF-7). Further, DOX@D3-CuS NSs exhibited a much higher toxicity towards cancer cells upon NIR light over individual counterparts suggesting their strong ability for chemo-photothermal therapy. Moreover, these biocompatible CuS NSs have shown excellent concentration dependent photoacoustic properties at pulse laser excitation (850 nm) and thus, they can be found potential application in chemo-photothermal therapy.

Microscopic scale analysis of the dynamic changes of the melt pool and the evolution of dendritic structure during L-DED of GH3536 alloy

Microscopic scale analysis of the dynamic changes of the melt pool and the evolution of dendritic structure during L-DED of GH3536 alloy

INTERLAYER EFFECT ON DEFORMATION AND FRACTURE OF DENDRITIC STRUCTURE FORMED DURING WIRE-FEED ELECTRON-BEAM ADDITIVE MANUFACTURING OF AL-SI ALLOY

Interfaces and surfaces play an important role in tribology, mechanics and materials science, causing plastic strain localization and stress concentration of different spatial scales. The interfacial inhomogeneity is highly pronounced in 3D printed materials due to thermo-cycling and layer-by-layer building. In this paper, the inlayer and interlayer structure of a eutectic Al-Si alloy fabricated by wire-feed electron-beam additive manufacturing is investigated by optical and electron microscopy. Model structures inheriting the experimental morphology are created, and their deformation and fracture are simulated using ABACUS/Explicit, with the user-defined subroutines being developed to describe the constitutive behavior of aluminum dendrite, silicon and eutectic materials. A two-scale computational approach is implemented to study the influence of the interlayer formed in the heat-affected zone on the dendritic structure strength.

Microstructure and mechanical properties of butt-welded Ti/steel bimetallic sheet using various multi-principal filler wires

Ti/steel bimetallic sheets have attracted significant attention in various engineering fields. However, achieving high-quality welded joints of Ti/steel bimetallic sheet presents difficulties because of poor metallurgical compatibility and different thermal expansion coefficients between titanium and steel. In this study, four types of multi-principal filler wires with varying contents of Cu, Ni, and Ti elements were designed and manufactured to finish the welding of TA2/Q235 bimetallic sheets. The study investigated the effects of various filler wires on the hardness, tensile strength, corrosion resistance, and microstructure of the welded joints. An interesting finding is that the highest tensile strength of 327±6 MPa was achieved in the welded joint using FeCoNi2Ti0.5 filler wire, with a joint coefficient of ∼79.1 %. The highest hardness in the weld zones was achieved by using FeCoNiTi0.5 filler wire, while the lowest hardness was achieved using FeCoNiCu0.5 filler wire. Dendrite (DR), interdendritic (ID), and eutectic structures were consistently observed in these weld zones. The phases of the DR and ID were identified as Fe2Ti and FCC structures based on EBSD data. A high content of Ni in filler wires could reduce the size and content of the Fe2Ti phase in the weld zones of Ti/steel bimetallic sheets.

Отримання жароміцного гомогенного сплаву методом пресування та спікання суміші порошків (Nb-21Ti-5Al-10Cr-7Mo) ат. %

Multicomponent high temperature strength alloys of the Nb-Ti-Al system, alloyed with Cr, Zr, Mo and Si, with a specific gravity of 6.3 - 7.4 g/cm3, have proven extremely promising in aviation and space technology. However, their physical and chemical features are associated with the high activity of the components, with a significant difference in melting temperatures (from Tmel. Mo – 2617 °C to Tmel. Al – 660 °C) and different specific gravity (from 10.2 g/cm3- Mo up to 2.7 g/cm3- Al), is a big problem for their production. The long crystallization interval of cast alloys of this system, thermophysical features of their crystallization, determine the possibility of formation of dendritic structures, the development of dendritic liquation and segregation of low- or high-temperature intermetallics and eutectics, the tendency to the formation of crystallization cracks, which reduces the operational characteristics of cast alloys. In this regard, it became necessary to investigate the possibilities of obtaining an alloy by the method of powder metallurgy. The purpose of this work was to obtain a homogeneous alloy, to study changes in the grain structure, phase transformations and mechanical properties of the material at various stages of processing in the process of obtaining a homogeneous alloy structure by powder metallurgy methods. The need to protect powder components from oxidation, formation of nitrides, carbides during technological operations at temperatures above 200 °C (high-purity argon) has been established. The optimal duration of intensive grinding of a mixture of powders and granules of raw materials has been worked out, which makes it possible to control the uniformity of the size of the particles of the mixture components, porosity and homogeneity of the alloy. The optimal duration of grinding is 30 minutes, during which the most homogeneous mixture in terms of particle size is formed. The optimal annealing mode was established, which ensures the achievement of homogenization of the alloy, phase transformations at the boundaries of the contact of component particles, and changes in grain sizes. Microstructural and X-ray structural analysis of the samples was carried out, their microhardness and grain dispersion were determined. Keyword: high-temperature strength niobium alloys, physical and chemical features, powder metallurgy, homogeneity, microstructure, mechanical properties, phase composition.

Diffusion Limited Aggregation via Python: Dendritic Structures and Algorithmic Art

Diffusion limited aggregation (DLA) has attracted much attention due to its simplicity and broad applications in physics such as nano and microparticle aggregations. In this study, the algorithm of DLA is written with Python. Python's Turtle library is used to plot the aggregate on the computer monitor as it grows. The algorithm is run on the Raspberry Pi. A cheap and portable medium is created for DLA simulation. Two different options are placed in the algorithm. The first path does not allow the primary particle to turn outside of the aggregate after the collision. However, the second one allows the percolation of the primary particle both inside and outside of the aggregate. The spherical dendritic structures consisting of 500-2000 primary particles are obtained by the algorithm. The fractal dimension of these structures is around 1.68. Their porosity is found below 50%. Their gyration radii are also calculated. Beyond scientific investigation, examples of algorithmic art using these dendritic structures are also given.

STUDY OF THE INFLUENCE OF THE CHEMICAL COMPOSITION OF RAILWAY AXLE STEEL ON THE UNIFORMITY OF THE FINAL MICROSTRUCTURE

The relevance of the work. For modern railway transport, increasing the strength and operational reliability of rolling stock parts, in particular railway axles, is an urgent task. It is known that the inhomogeneity of the distribution of chemical elements in the structure of structural grade carbon steels is formed mainly during their crystallization and may subsequently affect the final structural state and set of properties. Purpose. Study of the influence of the chemical composition of steels for railway axles on the uniformity of the structure. Methodology. Experimental ingots of different chemical compositions with different amounts and ratios of the main chemical elements within the range of OS and EA1N were produced in laboratory conditions. The grain structure was studied on microsections after etching with nital. Chemical inhomogeneity (“traces” of the dendritic structure) − the distribution of chemical elements in the microstructure of cast samples was detected by etching in a hot solution of sodium picrate. Metallographic analysis was performed on a light (optical) microscope “Axiovert 200 M MAT” manufactured by “Carl Zeiss”. The results. The effect of changing the chemical composition of carbon steel, which is intended for the manufacture of railway axles, on the peculiarities of the formation of ferrite-pearlite heterogeneity and grain size is determined. It is shown that in samples of steels corresponding to the EA1N brand with a lower carbon content, the distribution of phases is uneven. The mechanism of formation of such a structure is explained from the point of view of two theories. In samples of steels with an average carbon content, which correspond to steel of the OS grade, the distribution of the pearlite and ferrite phases is more uniform, the relationship between the size and the degree of darkening of the pearlite areas with the order of the former dendritic branches has been established. Based on the results of the quantitative analysis of the final grain structure, it was established that OS steel with an average carbon content at different Mn/Si ratios has a more uniform grain structure. EA1N steel with a lower carbon content has a pronounced grain size, with an increase in the Mn/Si ratio, the largest maximum of the dependence of the distribution shifts to a larger grain size (smaller number). Practical results. Increasing the homogeneity of the final microstructure contributes to increasing the plasticity and viscosity of steel, which directly affects the reliability and durability of railway axles.

Bimodal Behavior of Catalyst Layers Prepared By Electrospray: High Water Uptake and Superhydrophobicity

Electrosprayed catalyst layers (CLs) for electrodes of proton exchange membrane fuel cells (PEMFCs) combine high water vapor uptake with a superhydrophobic character. Such ‘bimodal behavior’ is the basis for their high performance as cathode in PEMFC, and must be explained in the light of the film morphology resulting from the electrospray deposition process. A microscopic analysis of the deposited films, covering different scales, reveals important differences in particles and ionomer distribution between the electrosprayed and sprayed layers. The resulting electrosprayed CL shows pore surfaces covered by dendritic structure that provide the superhydrophobic character. Other experimental evidences point to an specific interaction of the ionomer with the catalyst in electrosprayed films.

Bimodal Behavior of Catalyst Layers Prepared By Electrospray: High Water Uptake and Superhydrophobicity

Electrosprayed catalyst layers (CLs) for electrodes of proton exchange membrane fuel cells (PEMFCs) combine high water vapor uptake with a superhydrophobic character. Such ‘bimodal behavior’ is the basis for their high performance as cathode in PEMFC, and must be explained in the light of the film morphology resulting from the electrospray deposition process. A microscopic analysis of the deposited films, covering different scales, reveals important differences in particles and ionomer distribution between the electrosprayed and sprayed layers. The resulting electrosprayed CL shows pore surfaces covered by dendritic structure that provide the superhydrophobic character. Other experimental evidences point to an specific interaction of the ionomer with the catalyst in electrosprayed films.

Magnetic core supported ethyl acetate microdrops for organic contaminants removal from water

Organic contaminants have increasingly become a main threat to the water environment, necessitating novel methods for removing from polluted water. In this study, a kind of magnetic ethyl acetate microdrops (Fe3O4@KCC-1@EA) is fabricated for this purpose The KCC-1 shell of Fe3O4@KCC-1 nanospheres is a layer of silica with a dendritic fibrous structure. The ethyl acetate shell of the Fe3O4@KCC-1@EA microdrops provides them with the properties of an organic solvent. While the magnetic core makes them magnetically manipulable. Adding Fe3O4@KCC-1@EA microdrops to bisphenol A-polluted water allows the contaminants to be extracted into the ethyl acetate shell. These microdrops, saturated with bisphenol A, are then easily separated from the water phase with an external magnetic field, achieving a removal rate of over 98%. Besides bisphenol A, the Fe3O4@KCC-1@EA microdrops could also be employed to remove other organic contaminants. This method could provide a new pathway for water purification from organic contaminants.

Fabrication of Three-Dimensional Dendritic Ag Nanostructures: A SERS Substrate for Non-Invasive Detection.

This paper discusses the fabrication of three-dimensional dendritic Ag nanostructures, showcasing pronounced Localized Surface Plasmon Resonance (LSPR) effects. These nanostructures, employed in surface-enhanced Raman scattering (SERS), function as sensors for lactic acid in artificial sweat. The dendritic structures of the silver nanoparticles (AgNPs) create an effective SERS substrate, with additional hotspots at branch junctures enhancing LSPR. We achieve differential LSPR effects by varying the distribution and spacing of branches and the overall morphology. Adjustments to electrodeposition parameters, such as current and plating solution protective agents on an anodized aluminum oxide (AAO) base, allow for precise control over LSPR intensities. By pre-depositing AgNPs, the electron transmission paths during electrodeposition are modified, which leads to optimized dendritic morphology and enhanced LSPR effects. Parameter optimization produces elongated rods with main and secondary branches, covered with uniformly sized, densely packed, non-overlapping spherical AgNPs. This configuration enhances the LSPR effect by generating additional hotspots beyond the branch tips. Fine-tuning the electrodeposition parameters improved the AgNPs' morphology, achieving uniform particle distribution and optimal spacing. Compared to non-SERS substrates, our structure amplified the Raman signal for lactic acid detection by five orders of magnitude. This method can effectively tailor SERS substrates for specific analytes and laser-based detection.

Template-Assisted Electrodeposited Copper Nanostructres for Selective Detection of Hydrogen Peroxide.

In this study, we demonstrate the electrodeposition of copper nanoparticles (NPs) on pencil graphite electrodes (PGEs) utilizing sodium dodecyl sulphate (SDS) as a soft template. The utilization of the surfactant had an impact on both the physical arrangement and electrochemical characteristics of the modified electrodes. The prepared Cu-SDS/PGE electrodes had hierarchical dendritic structures of copper NPs, thereby increasing the surface area and electrochemical catalytic activity in comparison with Cu/PGE electrodes. The Cu-SDS/PGE electrode showed excellent catalytic activity in reducing hydrogen peroxide, resulting in the sensitive and selective detection of hydrogen peroxide. The electrode exhibited a good sensitivity of 21.42 µA/µM/cm2, a lower limit of detection 0.35, and a response time of less than 2 s over a wide range spanning 1 µM to 1 mM of hydrogen peroxide concentrations. The electrodes were also highly selective for H2O2 with minimal interference from other analytes even at concentrations higher than that of H2O2. The approach offers the benefit of electrode preparation in just 5 min, followed by analysis in 10 min, and enables for the quantitative determination of hydrogen peroxide within 30 min. This can be achieved utilizing a newly prepared, cost-effective electrode without the need for complex procedures.

Microstructural Study of the Coloring Variation of Chinese Sauce Glaze Replications

ABSTRACTSauce glazed wares of Yaozhou kilns are famous for their high gloss and distinctive glaze color palette varying from yellowish‐brown to reddish‐brown. In this work, sauce glazes were successfully replicated using the traditional technology of Yaozhou kilns. Micro‐Raman spectroscopy, combined with optical microscopy, scanning electron microscopy, x‐ray fluorescence, and reflective spectroscopy, was systematically applied to analyze the chemical composition, nature and distribution of crystals, and the coloration of the glazes. The results show that the yellowish‐brown glaze is mainly original from dendritic ε‐Fe2O3 crystals, whereas the reddish‐brown color is mainly derived from dendritic hematite crystals. Such dendritic structure could account for slightly color variations of the glaze surface observed in different angles, which also reported in Japanese Bizen ceramics. The principal component analysis (PCA) was further applied to study the Raman spectra of these iron oxides. The PCA results effectively indicates the structural disorders of these crystals introduced by ion substitutions. These substitutions could not only stabilize the crystals but also darken the crystals color. Besides, high Mg in the raw materials was found to benefit the growth of magnesioferrite crystals. The relative low level of Fe2O3, high level of SiO2, and CaO may relate to the formation of ε‐Fe2O3 crystals.

Experimental Study on the Microstructure and Tribological Properties of Laser-Clad Ni60-WC Composite Coatings.

To address the wear issues faced by the leg components of offshore platforms in harsh marine conditions, a Ni60-WC composite coating was fabricated on the surface of E690 high-strength steel using laser cladding. The microstructure, elemental distribution, microhardness, and tribological properties of the composite coating were characterized and tested using XRD (X-ray diffraction), SEM (scanning electron microscopy), EDS (energy-dispersive spectrometry), a microhardness tester, and a multifunctional tribometer. The study focused on the microstructure and tribological properties of the Ni60-WC composite coating. The results show that the composite coating primarily consists of γ-(Fe, Ni), WC, W2C, M23C6, and M6C phases, with cellular and dendritic structures at the top. WC and W2C, along with M23C6 and M6C, are precipitated from the W and C elements. The average hardness of the composite coating reached 569.5 HV, representing a 103% increase over the substrate hardness. The prepared composite coating exhibited a 32.6% increase in corrosion potential compared to the substrate. Additionally, the corrosion current density was reduced by 62.0%, indicating a significant enhancement in the corrosion resistance of the composite coating. The friction coefficient of the composite coating was reduced by 17.4% compared to the substrate, and wear volume was reduced by 79%, significantly enhancing the tribological performance of the coating due to reduced abrasive wear and fatigue wear.