Lamellar Spacing Research Articles

Phase formation and nanohardness of Ti–48Al–2Cr–2Nb-1.5C alloy by melt spinning: The effect of cooling rates

The effect of wheel speed on the phase formation and nanohardness of Ti–48Al–2Cr–2Nb-1.5C alloy by melt spinning was investigated. The results illustrate that with increasing wheel speed, the solubility of C atoms in the matrix increases, which reduces the volume fraction of Ti2AlC precipitates from 7.8 vol% to 2.5 vol%. The length-diameter ratio of precipitated Ti2AlC decreases from 32.2 to 2.2 with increasing cooling rate. Different wheel speeds didn't change the matrix (γ phase), while the primary phase formation was affected by it during solidification. When the wheel speed is 16 m/s, the α phase can directly nucleate in the liquid phase, leading to an increase in the volume fraction of α2 after RS. Meanwhile, owing to the decrease in lamellar spacing, the increase in the solid solution, and the nanoscale Ti2AlC dispersed in the lamellae, the nanohardness of the lamellae increases with increasing cooling rate. It increases from 4.92 ± 0.12 GPa at conventional solidification to 7.69 ± 0.21 GPa at a wheel speed of 24 m/s, which is an increase of approximately 56.1%.

Acceleration of Spheroidization in Low‐Density Ultrafine Pearlitic Steel by κ‐Carbide

The impact of κ‐carbide on the spheroidization process of low‐density ultrafine pearlitic steel (with 5 wt% Al and 5 wt% Mn additions) is investigated through isothermal annealing spheroidization. In the findings, it is demonstrated that κ‐carbides can significantly refine the lamellar spacing of low‐density ultrafine pearlite during the isothermal transformation. Additionally, under identical conditions, κ‐pearlite exhibits a higher number of ferrite/κ‐carbide interfaces. In the first stage of pearlite spheroidization, an abundance of dislocations and sub‐grain boundaries facilitate rapid fusion of the lamellar pearlite, while in the second stage, they provide a high‐speed diffusion pathway for carbon diffusion. Moreover, the reduced lamellar spacing shortens the distance for carbon and alloying elements diffusion, thereby promoting granular κ‐carbide formation and accelerating spheroidization in low‐density ultra‐fine pearlite.

In-situ synthesized multi-component particle reinforced TiAl composite with excellent mechanical properties

In order to overcome the inherent trade-off between strength and ductility of TiAl alloys, the BN nanosheets were added in Ti-48Al-2Cr-2Nb alloy. Ti-48Al-2Cr-2Nb-xBN (x = 0, 0.1, 0.5, 1, 2 wt%) alloys were prepared by vacuum arc melting (VAR), and the microstructures displayed a fully lamellar structure accompanied by simultaneous precipitation of Ti2AlN and TiB2 phases. The reaction of BN nanosheets with the Ti and Al elements resulted in formation of Ti2AlN and TiB2 phases. The lamellar colony size of TiAl composites was refined from 276.7 to 29.4 µm with BN content increasing from 0 to 2 wt%. While the lamellar spacing displayed an initial decrease followed by an increase, which was attributed to the synergistic effect of Ti2AlN and TiB2. Room temperature compression results showed that the compressive strength surged from 1653 to 2272 MPa as BN content rose from 0 to 0.5 wt%, with the highest compression strain of 34.7 % at 0.5 wt% BN. The high temperature compression results showed that the compressive strength increased from 887 to 1399 MPa as the BN content increasing from 0 to 1 wt%. Crack extension took the form of both trans-granular and inter-granular modes. The strengthening effect of TiAl composites was attributed to grain refinement strengthening and secondary phase strengthening via Ti2AlN and TiB2.

Effect of rare-earth element Gd addition on microstructure of TNM-based TiAl alloys

The effects of gadolinium (Gd) on the microstructures of Ti-43.5Al-4Nb-1Mo-0.1B-XGd (X = 0, 0.03, 0.06, 0.1 at.%) alloys were systematically studied. The results show that all microstructures of casting alloys are nearly lamellar, nevertheless, the precipitations of Gd2O3 are formed by the combination of Gd atoms with O atoms, playing a role of heterogeneous nuclei refining both lamellar colonies and the lamellar spacing. However, the phase transition pathways of all alloys were L → L + β →β→ α + β → α + β/B2 + γ → α2 + B2 + γ. After heat treatment, the microstructures were nearly lamellar, but the lamellar spacing was refined by Gd2O3.

Synergistic control of microstructures and properties in eutectic high-entropy alloys via directional solidification and strong magnetic field

The AlCoCrFeNi2.1 eutectic high-entropy alloy (Ni2.1 EHEA), as an exemplary representative of the high-entropy alloy family, has garnered significant research attention owing to its exceptional comprehensive properties. In this study, we investigated the influence of various growth velocities on the microstructure, lamellar spacing, and mechanical properties of the Ni2.1 EHEA. We observed that at lower growth velocities, the structure consisted of an alternating face-centered-cubic (FCC) phase and B2 phase lamellae aligned in a single direction, with the lamellae orientation parallel to the direction of the heat flow. The yield strength increased with the growth rate, while the ultimate tensile strength decreased with increasing the growth velocity. Ductility remained relatively consistent, and a double yield phenomenon was observed in the elastic-plastic deformation region. Under conditions of high growth velocities, the microstructure transitioned from a single-directional full lamellar structure to a multi-stage lamellar arrangement. The most favorable comprehensive mechanical properties were achieved at a growth rate of 200 μm/s, resulting in a yield strength of 450 MPa, an ultimate tensile strength of 1092 MPa, and a remarkable ductility of ∼32% in the directionally solidified samples—double that of the arc-melted sample. The evolution law of directional solidification structures under the coupling effect of different magnetic fields and different growth rates was studied. The interaction of the thermoelectric-magnetic force and thermoelectric-magnetic convection and the potential mechanism of microstructure evolution under the effect of magnetic field were deeply analyzed. The results reveal that at a growth rate of 2 μm/s, the spacing between eutectic layers decreases as the magnetic induction intensity increases, leading to the transformation of some regular layers into spherical layers. Similarly, at a growth velocity of 10 μm/s, the eutectic structure exhibited a Columnar-to-equiaxed transition (CET). However, as the growth rate further increases, the limited exposure time to the magnetic field prevented significant structural changes.

Microstructure and property optimization of Al–8Ce alloys: Electromagnetic stirring and Sc–Zr microalloying

To further improve the strength of an Al–Ce alloy, the effects of electromagnetic stirring treatment, Sc–Zr microalloying, and their compound action on the microstructure and properties of the Al–8Ce alloy were investigated for the first time in this study. The results show that the primary α-Al becomes coarse, the eutectic Al11Ce3 phase is refined and the lamellar spacing increases significantly due to the combined effect of forced convection of electromagnetic field and dendrite fragmentation and nucleation in Al–8Ce alloy after electromagnetic stirring treatment. After the Sc–Zr microalloying treatment of the Al–8Ce alloy, the α-Al changes from a dendritic to fine round morphology, and the eutectic Al11Ce3 phase changes from lamellar to fibrous, which is due to the heterogeneous nucleation of Al3(Sc, Zr) phase and the adsorption refinement caused by the enrichment of Sc and Zr. The optimization effect of Sc–Zr microalloying on the mechanical properties of the Al–8Ce alloy was better than that of electromagnetic stirring and their synergistic treatment. The tensile strength and yield strength of Al–8Ce alloy with Sc–Zr additions were increased from 157 MPa to 85 MPa–192 MPa and 115 MPa, respectively, by 22.3 % and 35.3 %. After aging treatment, the tensile strength (from 192 to 272 MPa) and yield strength (from 115 to 221 MPa) significantly improved owing to the secondary precipitation of Al3(Sc, Zr) particles. The precipitation strengthening of the Al3(Sc, Zr) phase was the main contributor to the high yield strength of the alloy.

Effect of Graphite Powder Addition on Microstructure and Room Temperature Mechanical Properties of Ti-45Al-8Nb Alloys

The enhancement of the mechanical properties of TiAl alloys through the introduction of a second-phase reinforcement is highly essential. In this paper, using graphite powder as a carbon source, the Ti2AlC phase is introduced to improve the compression and friction properties of the TiAl alloy. Concurrently, the effects of graphite powder additions on the microstructure and room-temperature mechanical properties of Ti-45Al-8Nb-xC (mass%) alloys are investigated. The results show that as the volume fraction of Ti2AlC and the interdendritic γ phase increases, the length–diameter ratio of the Ti2AlC phase decreases with increases in the graphite powder addition. The addition of graphite powder results in a refining effect on the grain size and lamellar spacing of the Ti-45Al-8Nb-xC (mass%) alloys. As the graphite powder content increases from 0 to 0.9 mass%, the microhardness increases from 557 HV to 647 HV. The room-temperature compressive strength and strain of the Ti-45Al-8Nb-xC (mass%) alloys first increase and then decrease with the addition of graphite powder. Specifically, when the content of graphite powder is 0.6 mass%, the alloy exhibits a maximum compressive strength and strain of 1652 MPa and 22.2%, respectively. Compared with the alloy without the graphite powder addition, the compressive strength and strain are improved by 37.7% and 62.1%, respectively. The wear resistance of the alloys is improved through the addition of graphite powder and the wear rate decreases from 5.062 to 2.125 × 10−4 mm3·N−1·m−1 as the content of graphite powder increases from 0 to 0.9 mass%.

Improving mechanisms of lamellar microstructure and mechanical properties by Y and in-situ Y2O3: Modification of carbides particles and complete transformation of Ti2AlC particles

To reveal the modification mechanism of carbides particles by in-situ Y2O3, and then the improvement mechanisms for Ti42Al6Nb2.6C-xY alloys, the microstructures were observed by SEM, XRD and TEM, and the mechanical properties were examined. Results show that the flaky TiC transformed completely into Ti2AlC, and the morphology of Ti2AlC turned fine-needle shaped into short-rod shaped. The content of Ti2AlC with the aspect ratio of 1–5 increased from 24.2 to 81.4%, and the average aspect ratio decreased from 7.9 to 3.7 as Y increased from 0 to 0.08 at. %. The average lamellar colony size and lamellar spacing decreased from 24.054 to 17.500 μm and 0.531 to 0.304 μm, respectively. The growth of TiC phase was constrained by in-situ Y2O3, which alleviated agglomeration distribution of TiC and provided a fine TiC substrate for the nucleation of Ti2AlC. The interfacial interaction between in-situ Y2O3 and Ti2AlC restricted the longitudinal and transverse growth of Ti2AlC. The modified Ti2AlC and in-situ Y2O3 particles as nucleation sites for β grains were the basis for obtaining fine lamellar structure. For mechanical properties, the compressive strength increased from 1388 to 1781 MPa, the yield strength increased from 1265 to 1544 MPa, and the Vickers hardness increased from 495 to 609 HV. The refinement of lamellar colony by modified Ti2AlC and in-situ Y2O3, and the load strengthening of Ti2AlC particle contributed to the mechanical properties.

Induced formation of nano precipitates and improve microstructure and mechanical properties by ultrasonic wave in the solid-liquid two-phase area of as-cast Ti48Al2Cr2Nb 2.5 C alloy

To refine the microstructure and form Ti3Al2 and C14 nano particles, and then improve strength and strain simultaneously, the Ti48Al2Cr2Nb 2.5 C alloy has been prepared under ultrasonic wave. Size of lamellar colony, lamellar spacing, phase composition, compressive properties and the related mechanisms have been studied. Results show that size of lamellar colony decreases from 40.7 to 33.0 µm and lamellar spacing decreases from 1.5 to 0.8 µm. Average length-diameter ratio of Ti2AlC decreases from 5.4 to 1.9 with increasing the ultrasonic treatment time from 20 to 100 s. Two kinds of nanoparticles form. One is hexagonal Ti3Al2 phase, which has incoherent relationship with γ phase. Another is Ti(Al, Cr)2 phase with C14 structure. The Ti2AlC and α grain are refined by undercooling nucleation and dendrite fragmentation in solid-liquid two-phase area. The active dislocations and vacancy under ultrasonic promote the diffusion of Ti and Cr, and then induce the Ti3Al2 and Ti(Al, Cr)2 formed during solid-phase transformation. Compressive results show that the strength increases from 1901 to 2532 MPa, and the strain simultaneously increases from 27 to 34% with increasing the time from 0 to 100 s. The lattice distortion caused by the difference in thermal expansion coefficient between the Ti3Al2, Ti(Al, Cr)2 and matrix and the microstructure refined by ultrasonic jointly hinder dislocation slip to strengthen the alloy. The refinement and uniform distribution of Ti2AlC hinder crack propagation to improve toughness.

Preparation and wear properties of high-silicon high-vanadium wear-resistant alloy with nano pearlite matrix and carbides composite structure

Combining high hardness carbide of high vanadium cast iron with nano pearlite, which has high strength and toughness, represents an innovative attempt to explore a new technology for preparing high vanadium alloy. In this study, a high-silicon high-vanadium wear-resistance alloy (HSHVWRA) was designed, incorporating a nano pearlite matrix and carbides composite structure. By increasing the vanadium content, numerous high hardness micrometer vanadium carbides were obtained The CCT curve was shifted to the left by increasing the silicon content in the alloy. Subsequently, the nano pearlite matrix was obtained by air cooling after austenite at 1100 °C. After heat treatment, the inter lamellar spacing of pearlite decreased from 500 to 1500 nm in the as-cast state to 50–200 nm. The heat treatment process significantly improved the wear resistance of HSHVWRA by obtaining a nano pearlite matrix. The weight loss due to abrasive wear in the nano pearlite matrix-based HSHVWRA was reduced by 26.9 % compared to the traditional micro-pearlite matrix-based alloy. In the impact wear test, the wear weight of the nano pearlite material was reduced by 63.7 % compared to the cast sample, resulting in a maximum relative wear resistance of 2.75. Nano pearlite has the ability to prevent crack initiation between the matrix and carbides and inhibit the propagation of fatigue cracks, thereby enhancing the fatigue resistance of the matrix. Additionally, with a higher number of layered sheets, nano pearlite can effectively withstand impact loads. Meanwhile, submicron carbides dispersed in the nano pearlite matrix contribute to a second phase strengthening role and cooperate with nano pearlite to enhance the wear resistance of the materials.

High-resolution reconstruction-based investigation of multi-scale lamellar microstructures by coupled crystal plasticity and in-situ experiment

This study aims to establish a novel approach to better understand and predict material behavior in multi-scale lamellar microstructures. High-resolution reconstruction is built on collaborative characterization at both grain and sub-grain scale. A framework for microstructural characterization integrates, secondary electron imaging (SEI), electron backscatter diffraction (EBSD), and image recognition, to ensure that the reconstructed microstructure adequately represents the equivalent grain size, lamellar spacing, and lamellar geometric orientation. Importantly, a high-resolution reconstruction algorithm was developed combining the Laguerre-Voronoi tessellation and minimum bounding sphere (MBS), which allows the reconstructed model retain multi-scale microstructures. Finally, the mechanical properties of pearlite were investigated by combining crystal plasticity simulation with in-situ scanning electron microscopy (SEM) tensile testing based on high-resolution reconstruction. Stress-strain field analysis revealed that cross-lamellae strain bands originate from ferrite large deformation-induced shear transmission, with marked strain distribution heterogeneity within identical lamellae. This concurrently validated the excellent reliability of the novel strategy.

Probing effects of solute trapping on the mechanical properties of α-Al in rapidly solidified hypoeutectic Al-10at.%Cu after surface laser melting

After scanned laser surface remelting the resultant rapid solidification microstructures of multicomponent alloys exhibit morphological gradients, with scale refinement and non-equilibrium features, including non-equilibrium solute trapping, which are associated with property changes. Combinations of site-specific mechanical property measurements by nano-indentation and microstructural analyses by electron microscopy have been used to determine microstructure-property relationships for the characteristic features of the rapid solidification microstructure of a hypo-eutectic Al–Cu alloy containing 10 atom percent Cu. A microstructure gradient developed as the solidification rate increased monotonically during the re-solidification process. For a laser scan velocity of 3 mm/s most of the rapid solidification microstructure is comprised of micrometer scale refined dendritic cells of α-Al(Cu) and nanometer scale refined intercellular θ-Al2Cu phase or eutectic. The cellular α-Al(Cu) constituent consistently showed Cu-solute supersaturation and a 36 % hardness increase relative to the as-cast state. The eutectic microconstituent exhibited increases in hardness that correlated quantitatively with the increasing lamellar spacing refinement obtaining for increasing solidification rate. The possible contributions from precipitation, solute and grain-size strengthening mechanisms to the hardness increase in the α-Al(Cu) cells have been assessed. The hardness increase of the α-Al(Cu) cells was attributed to a combination of solute and grain size strengthening.

A microstructure-based constitutive model for eutectoid steels

This work presents a constitutive model for eutectoid steels based on their two-phase lamellar microstructure. The model accounts for the individual behaviour of both ferrite and cementite, with perfect interphase adhesion assumed. It considers anisotropic hardening mechanisms in ferrite derived from the lamellar structure of pearlite while ignoring the crystal structure of either phase. The model also accounts for the evolution of orientation and spacing of lamellae under directional deformation, along with the evolution of internal stress distribution in both phases. Due to its simplicity, the model has very few calibration parameters but is still able to reproduce complex strain paths and loading conditions with excellent accuracy. The model was compared with tensile, compression and torsion tests from a 13-pass wire drawing series (up to drawing strains of 2.7) and reproduced accurately the mechanical response under any loading condition. The robustness of the model lies in the fact that it is able to recreate the evolution of internal stresses built in cementite and ferrite. Such internal stress evolution was confirmed to reproduce accurately the stress partitioning observed in neutron and X-ray diffraction tests reported in literature. Moreover, the model contributes to the understanding of the rapid broadening of cementite diffraction peaks observed during in-situ tensile tests of patented wires.

Effect of Cr–Mo Addition on the Microstructure and Mechanical Properties of Medium‐Carbon Steel

Herein, the effects of Chromium–Molybdenum (Cr–Mo) addition on the microstructural evolution and mechanical properties of medium‐carbon steel after spheroidization annealing are systematically studied through scanning electron microscopy, electron backscatter diffraction, and tensile testing. Cr–Mo addition hinders the proeutectoid ferrite + pearlite transformation, thereby promoting the bainite transformation. Moreover, it refines the pearlite lamellar spacing as well as decreases the average carbide diameter, increases the number of carbides per unit area, and hinders ferrite recrystallization. Compared with those in the B1 steel annealed for 8 h, the size of carbides and their number per unit area in the CM1 steel are 30% lower and 2.2‐fold higher, respectively. Due to finer ferrite grains, smaller carbides, and a higher amount of carbides, the strength of steel improves, and the plasticity slightly reduces after Cr–Mo addition. After 2 h of annealing, the yield strengths of Cr–Mo steels are 77.5–109.5 MPa higher than those of base steels; the elongations are above 20%. The contributions of the strengthening mechanism of steel to the yield strength are as follows (from high to low): grain boundary, precipitation, solid solution, and dislocation strengthening.

Interlayer spacing control strategy to construct the rapid thermal conductivity channel in the molten salt phase change materials

With the goal of improving the thermal conductivity of inorganic salt PCMs without significantly affecting the thermal energy storage density, a functionalized modification strategy to regulate the layer spacing of nano two-dimensional (2D) materials was proposed to construct a thermal conduction pathway in phase change materials (PCMs). In the instance of graphene, we proposed hydroxylation to increase the lamellar spacing between graphene, improve its dispersion in molten salt PCMs, and speed heat transfer of graphene composite molten salt. When compared to pure graphene, the addition of hydroxylated graphene (GOH) improved the thermal conductivity of PCMs significantly. The thermal conductivity model demonstrated that the thermal conductivity pathway can be constructed by equally dispersing enough GOH to further increase the thermal conductivity. When the GOH percentage was 0.8 %, the composite's thermal conductivity was 2.60 W/(m·K), which was 118.5 % greater than the graphene composite with the same content. When the melting point was 240.00 °C, the composite material had a high latent heat of 355.52 J/g. The morphology characterization and thermal conductivity model analysis show that adjusting the layer spacing can improve graphene dispersion, facilitating the construction of thermal conduction pathway in PCMs, accelerating heat transfer, and essentially maintaining PCMs' original thermal energy storage density. Therefore, the strategy of regulating the layer spacing of 2D materials in this study has the potential to extend the application of other 2D materials used in PCMs to improve the heat storage properties.

A refined fully lamellar TiAl alloy extruded at α-phase region: Microstructure and mechanical properties

Multiphase TiAl alloys with refined fully lamellar (RFL) microstructure can balance their mechanical properties at room temperature (RT) and high temperatures, which is vital for their applications. A new cost-effective and compact processing method is needed to reduce the processing cost and widen the extent of applications. In this work, Ti–44.5Al–4Nb–0.5Mo–0.1B (at.%) alloy with RFL microstructure was fabricated using a one-step hot-pack extrusion process at 1280 °C with an extrusion ratio of 4. The microstructure and mechanical properties of the extruded rod were uniform except in a thin layer near the surface. The RFL microstructure exhibited a deformation texture with <11 2‾ 0> α2 parallel to the extrusion direction and (0001) α2 parallel to the radial direction of the rod. The yield strength, ultimate tensile strength and ductility of the rod were simultaneously improved after extrusion due to elimination of βo phase, decrease in the sizes of the lamellar colony and spacing, and the presence of texture. The fundamental reason why RFL microstructure can be obtained by extrusion is that the higher Al and lower Mo contents in the alloy expand α phase region and decrease βo content of the alloy compared with TNM alloy.

Simultaneously enhancing strength and ductility of high-Nb-containing TiAl alloy via extrusion-assisted microstructure tailoring

In most metallic materials, the strength-ductility trade-off serves as an inevitable scenario. Therefore, improving the room/high-temperature strength/ductility of high Nb-TiAl alloys based on a lamellar microstructure is important for practical applications. In this work, a novel microstructure with fine lamellar colonies and a certain number of residual γ grains was developed through hot extrusion in the near α phase region. The results indicated that the lamellar colony size and spacing of the as-cast alloy were significantly refined by hot extrusion. The as-extruded Ti-45Al-8Nb-(W, B, Y) alloy demonstrated a good combination of high strength and ductility. The tensile strength and ductility were 1129 MPa and 2.04% at room temperature (RT), respectively, and 744 MPa and 51.20%, respectively, at 850 °C. A simultaneous improvement in strength and ductility below ductile-brittle transition temperature (DBTT) could be attributed to the abundant deformation twins and their intersections, as well as prominent strain working caused by high-density dislocations in the γ phase. Due to dynamic recrystallization, the ductility was significantly enhanced when stretched over DBTT. This extrusion-assisted microstructure tailoring strategy could be extended to other TiAl systems and may serve as a useful solution for addressing the significant engineering constraints posed by the low RT ductility and poor hot-working capabilities of high Nb-TiAl alloys.

Influence of upset forging and heat treatment on the microstructure and mechanical properties of a new β-solidifying γ-TiAl alloy

Our previous works revealed that alloying of a β-solidifying intermetallic γ-TiAl alloy with Zr and Hf instead of Nb led to improvement in the strength and creep resistance due to effective solid solution hardening, a strong partitioning preference γ>α2 for Zr and a lower lattice misfit of the γ-TiAl and α2-Ti3Al phases. On this basis, a new β-solidifying γ-TiAl alloy with a composition Ti-44Al-X(Nb,Zr,Hf)-0.15B (at.%) (designated as TNZ γ-alloy) has been designed. The as-cast ingot had a fine lamellar structure with a small amount of the metastable β(βo) phase. Compression tests performed at T = 950–1200 °C showed that the new alloy possessed good forgeability even at 950 °C without signs of strain localization. The alloy ingot was subjected to upset forging at T = 950 °C followed by heat treatments. The applied processing led to formation of refined duplex and lamellar type structures almost free of the β(βo) phase. The obtained microstructural conditions were examined and then the tensile and creep tests were performed. The mechanical tests showed that with increasing the lamellar constituent and decreasing the lamellar spacing the creep resistance expectedly increased and ductility decreased. The obtained results are discussed from the viewpoint of processability, mechanical properties and oxidation resistance of the new alloy.

Solidification behavior and microstructure of Ag–Cu eutectic alloy at different sub-rapid cooling rates

The microstructures of rapidly solidified Ag-39.9 at. % Cu eutectic alloys have been widely studied, while the research between microstructures and sub-rapid cooling rates is still lacking. Ag-39.9 at. % Cu eutectic alloy was solidified in quartz crucibles under different conditions. The alloy that was melted and in-situ cooled in a quartz crucible to room temperature solidified into eutectic dendrites composed of regular lamellae. The alloy that was melted and injection cast into a quartz crucible solidified into equiaxed eutectic colonies with primary α-Ag phase embedded. If the quartz crucible was further immersed in a gallium-indium liquid, a new spherical eutectic colony structure was found, with anomalous eutectic or primary α-Ag phase at the central part and a “ring” of coarse lamellar eutectic structure separating the eutectic colony into two parts. It is demonstrated that the cooling rate influences not only the primary phase selection and eutectic lamellar spacing, but also the eutectic nucleation and growth mode.

Tailoring Monovalent Ion Sieving in Graphene-Oxide Membranes with High Flux by Rationally Intercalating Crown Ethers.

Two-dimensional membranes have shown promising potential for ion-selective separation due to their well-defined interlayer channels. However, the typical "trade-off" effect of throughput and selectivity limits their developments. Herein, we report a precise tailoring of monovalent cation sieving technology with enhanced water throughput via the intercalation of graphene-oxide membranes with selective crown ethers. By tuning the lamellar spacing of graphene oxide, a critical interlayer distance (∼11.04 Å) is revealed to maximize water flux (53.4 mol m-2 h-2 bar-1) without sacrificing ion selectivity. As a result, the elaborately enlarged interlayer distance offers improved water permeance. Meanwhile, various specific cations with remarkably high selectivity can be separated in mixed solutions because of the strong chelation with crown ethers. This work opens up a new avenue for high-throughput and precise regulation of ion separations for various application scenarios.