Search

Oxygen and impurities are basically unavoidable during the manufacturing of Fe-based metallic glasses, frequently impeding the products' performance and greatly increasing the processing cost. Until now, how oxygen affects the glass-forming ability remains controversial, and eliminating the adverse effects of oxygen and impurities is still a huge challenge. Here we discover a new force of oxide inclusion flotation that drives the occurrence of purification, by blowing oxygen into the Fe-based melts, which help to mix the melts well to accelerate the oxidization and elimination of impurities from commercial raw materials. The synergistic reaction of oxygen and impurities not only improves the glass forming ability, magnetic and mechanical properties of the products, but also makes the stringent processing requirements, e.g. high-purity starting materials and/or high-purity argon, unnecessary. This study uncovers the mystery of oxygen in the glass formation, extends the innovation of fabrication process and highlights a significant technological breakthrough to reduce industrial production cost of Fe-based metallic glasses.

Highly undercooled multi-component CoCrCuFeNi-3 at.% Sn high-entropy alloy was studied by adopting molten glass purification combined with cycle superheating methods. Based on the critical undercooling ΔT⁎, the characteristic of liquid-phase separation was researched at different undercoolings. Accompanying phase separation, two phases (CoCrFeNi-rich and CuNi-rich) and three kinds of nano-precipitates (CrCo-rich, CrSn-rich and Sn-rich nano-precipitates) were detected. The microhardness of undercooled CoCrCuFeNi-3 at.% Sn high-entropy alloys increased markedly with the increase of undercooling. The effect of Sn on the microstructure evolution and properties in the process of phase separation was clarified with the aid of nano-precipitates.

Selective laser melting (SLM) provides a promising alternative to overcome the size and geometry limitation in the fabrication of metallic glasses (MGs). Understanding the change of atomic-scale structure is vital to glass formation and the properties of SLM-fabricated MGs. In this work, atomic structural evolution of Cu50Zr50 MG fabricated by SLM was investigated using molecular dynamics simulations. Voronoi tessellation analysis indicates that icosahedron-like clusters and Frank-Kasper polyhedra are dominant in cladding and deposited layers. In addition, the fractions of populous icosahedron-like clusters decrease in molten pool while slightly increase in heat affected zone during SLM process, and the fractions of populous Frank–Kasper polyhedra remain virtually unchanged after laser melting and heat affecting. This work provides a necessary understanding and novel guidance to the fabrication of MGs using SLM.

Ti–10Fe–6Al alloy was rapidly solidified using single roller melt-spinning technique to obtain ribbons, which was developed and used for supercapacitor electrode materials for the first time through facile oxidation. After oxidation at 680 °C for 100 h, TiO2/Fe2O3/Al2O3 nanocomposite on Ti–10Fe–6Al alloy ribbons consisting of numerous nanoparticles with average diameter of 90 nm was formed, which directly served as current collectors. For Ti–10Fe–6Al alloy foils cut from alloy ingot, oxidation product also showed particle shape but the diameter was far larger than that on oxided Ti–10Fe–6Al alloy ribbons. The ribbon electrode exhibited excellent electrochemical performance with areal capacitance of 10,500 µF cm−2 at current density of 40 µA cm−2 as well as long-term cycling stability of about 79.9% capacitance enhancement after 5000 cycles.

In the present work, mesoporous NiCo2O4 nanorod/graphene oxide (NiCo2O4/GO) composite was prepared by a facile and cost-effective hydrothermal method and meanwhile, N-doped graphene (N-G) was fabricated also by a hydrothermal synthesis process. NiCo2O4/GO composite and N-G were used as positive and negative electrodes for the supercapacitor, respectively, which all displayed excellent electrochemical performances. The NiCo2O4/GO composite electrode exhibited a high specific capacitance of 709.7 F g−1 at a current density of 1 A g−1 and excellent rate capability as well as good cycling performance with 84.7% capacitance retention at 6 A g−1 after 3000 cycles. A high-voltage asymmetric supercapacitor (ASC) was successfully fabricated using NiCo2O4/GO composite and N-G as the positive and negative electrodes, respectively, in 1 M KOH aqueous electrolyte. The ASC delivered a high energy density of 34.4 Wh kg−1 at a power density of 800 W kg−1 and still maintained 28 Wh kg−1 at a power density of 8000 W kg−1. Furthermore, this ASC showed excellent cycling stability with 94.3% specific capacitance retained at 5 A g−1 after 5000 cycles. The impressive results can be ascribed to the positive synergistic effects of the two electrodes. Evidently, our work provides useful information for assembling high-performance supercapacitor devices.

Molecular dynamics simulations have been performed to study the cooling process of two-dimensional liquid germanium under nanoslit confinement. The results clearly indicates that the liquid germanium undergoes an obvious liquid-solid phase transition to a monolayer honeycomb film with the decrease of temperature, accompanying the rapid change in potential energy, atomic volume, coordination number and lateral radial distribution function. During the solidification process, some hexagonal atomic islands first randomly emerge in the disordered liquid film and then grow up to stable crystal grains which keep growing and finally connect together to form a honeycomb polycrystalline film. It is worth noting that the honeycomb germanium film is low-buckled, quite different from the planar graphene.

As a promising additive manufacturing technique, selective laser melting (SLM) provides the possibility of fabricating metallic glassy components free of the constraints of geometrical complexity and dimensions. However, unexpected crystallization greatly affects the microstructure and degrades the mechanical performance of SLM-fabricated metallic glasses (MGs). To clarify the crystallization mechanism and the effect of laser processing on the crystallization, we investigate the atomic-level crystallization in the SLM Zr90Cu10 MG by using molecular dynamics simulations. The results show that crystallization highly related to scan speed lies in the atomic-level cluster changes. Lower scan speed leads to a dramatically increased fraction of the BCC crystal phase, accompanied by the nucleation of a few HCP and FCC crystal phases. As scan speed increases, more icosahedron-like clusters are formed, leading to the formation of the MG, while the nucleation of the crystal phase is suppressed. The suppression of crystallization is further attributed to a higher average temperature variation rate induced by higher scan speed, which reduces the relaxation time, preventing the nucleation and growth of crystal phases. This work contributes to the understanding of the crystallization in MGs during the SLM process at the atomic level, providing guidance to suppress the crystallization in the SLM process of desired metallic glassy components.

In the report, we explore a two-step efficient synthetic to purposefully fabricate three-dimensional (3D) NiCo2S4 nanosheets for advanced electrochemical supercapacitors. They were characterized for their structural, morphological and electrochemical properties by using XRD, SEM, TEM, cyclic voltammetry and charge discharge methods. The unique designed nanostructure exhibits a high specific capacitance (1257.1 F g−1 at current density 1 A g−1), good rate performance (75.7% retention for current increases around 20 times) and excellent cycling stability (80% retention at 5 A g−1 after 1000 cycles). We are the first step in the synthesis of 3D NiCo2S4 flowers, which have a specific capacitance of 700.7 F g−1 at the current density of 1 A g−1 and exhibit excellent cycling stability with 95% capacitance retention. The S-NiCo2S4//activated carbon asymmetric supercapacitor is can deliver a maximum energy density of 47.3 W h kg−1 at a power density of 477.3 W kg−1. Therefore, according to our investigation it can be concluded that the low cost and environmental friendly two-step approach from 3D NiCo2S4 nanoflowers to the 3D NiCo2S4 nanosheets could be used to deposit efficient 3D NiCo2S4 nanosheets for supercapacitor application.

Synthesis of electrode materials with desirable morphology and size for supercapacitor applications is an important and challenging research topic. In this work, four types of Co3O4 nanostructures, namely hexagonal-shaped nanosheets, nanoflake arrays, nanoflowers and oval-shaped nanospheres were synthesized via a facile in-situ dealloying method. Applied as electrode material for supercapacitiors, the Co3O4 nanospheres achieves highest areal capacitance of 16.58 F cm−2 at current density of 10 mA cm−2. The Co3O4 nanoflowers exhibited promising capacitive properties and excellent retention. Its areal capacitance can reach 9.27 F cm−2 at the current density of 10 mA cm−2 and retain 98.5% of its initial capacitance at the current density of mA cm−2 after 1000 charge–discharge cycles. This work could provide a deeper understanding of the morphology effect on the supercapacitive performance, and also suggests the importance of rational design and synthesis of electrode materials with desirable morphology and size for high performance supercapacitor applications.

The solidification of two-dimensional liquid copper confined to graphene layers has been studied using molecular dynamics simulations. The results clearly show that the liquid copper undergoes an obvious transition to a crystal film with the decrease of temperature, accompanied by dramatic change in potential energy and radial distribution function. Moreover, five different simulation models are used to investigate the effects of the number of graphene layers on the mechanical properties of the composites. It is found that the strength and plasticity of the composites have been improved significantly.

In this paper, Cu2O/CoO nanoneedle arrays (Cu2O/CoO-NNAs) are vertically grown on nanoporous Cu/Co (NPs-Co/Cu) conductive substrate through a facile dealloying and oxidation method. Benefiting from their intriguing structural features, the NPs-Cu/Co alloy based Cu2O/CoO-NNAs hybrid possesses fascinating electrochemical performance as an integrated binder-free electrode for symmetric supercapacitors (SSCs). High areal capacitances of 0.21 F cm−2 can be achieved at a current densities of 5 mA cm−2. Moreover, electrode has an excellent long-term cycling stability with 100% capacitance retention after 10000 cycles. A maximum of volumetric energy density (0.81 mW h cm−3) and volumetric power density (3 W cm−3) were achieved for the as-fabricated SSCs device. Therefore, the present work holds a great promise for future design and large-scale production of high volumetric energy density and volumetric energy density electrodes by dealloying and oxidation method for energy storage devices.

AlxCrFeNi eutectic multi-component alloys were prepared to obtain excellent mechanical properties by double-phase strengthening. The X-ray diffraction results showed that the crystal structure were both body-centered cubic and energy-dispersive X-ray spectrometer identified that the two phases are ordered NiAl intermetallic and disordered [Fe, Cr] solid solution. The formation of eutectic structures was introduced by a simplified dynamic model. After mechanical tests, the alloys presented excellent compressive strength and unexpected large deformation. Due to the solid solution and fine-grain strengthening resulted by Al addition, mechanical properties of AlxCrFeNi alloys exhibited regularity in some degree. Among all alloys, Al1.3CrFeNi has the highest fracture strength and Al0.9CrFeNi has the most excellent strain. Besides, Al1.2CrFeNi alloy showed a good combination of strength and ductility.

NiCo2S4 spheres with granular core were designed and fabricated via an easy two-step hydrothermal reation: carbon sphere clusters were used as templates to obtain NiCo2(OH)6/C precursor, which reacted with sodium sulfide to synthesize granular NiCo2S4 and then, the precursor of NiCo2S4 was grown on the periphery of granular NiCo2S4 to form the unique structure. The NiCo2S4 spheres with granular core specific surface area reaches 26.61 m2 g−1, which is about twofold of granular NiCo2S4 (11.41 m2 g−1). Electrochemical performance of the electrodes has been investigated. The electrode of NiCo2S4 spheres with granular core displays high specific capacitance of 1156 F g−1 at a current density of 1 A g−1, which increases by 71% compared to that of granular NiCo2S4 (675 F g−1). Upon 1000 charge/discharge cycles, the NiCo2S4 spheres with granular core electrode exhibits excellent cycling stability with 82% capacitance retention at 5 A g−1. In view of the low cost and superior electrochemical performance, the NiCo2S4 spheres with granular core synthesized using carbon sphere clusters as templates could be a promising electrode material for supercapacitors.

Co 3 O 4 nanosheets were straightforwardly fabricated through in-situ dealloying and oxidation process of etching Al 65 Co 35 alloy in 1 M NaOH solutions. It exhibited a high specific capacitance of 5747 mF cm −2 at a current density of 5 mA cm −2 and good rate capability. Meanwhile, the capacitance retention keeps about 108.7% of the initial value after 1000 cycles at a current density of 30 mA cm −2 . The simple synthetic process and all these impressive results demonstrated that the Co 3 O 4 electrode with flower-like nanoplates is promising for practical applications in supercapacitors.

In this paper, we reported a facile route for the fabrication of TiO 2 /Fe 2 O 3 composite on the surface of Ti-15Fe alloy foil prepared by arc melting through simple high-temperature oxidation, which was used as an electrode for supercapacitor. TiO 2 and Fe 2 O 3 grew together and in coarse short rod shape. The electrode exhibited excellent electrochemical performance with areal capacitance of 840 mF cm − 2 at current density of 1 mA cm −2 as well as superior long-term cycling life of 120% capacitance retention after 3000 cycles. These results demonstrate the potential of oxidation products of Ti alloys as high-performance electrode materials for supercapacitor applications.

In this paper, the structure transformation and fractography of a metallic glass Zr 20 Ti 20 Cu 20 Ni 20 Be 20 (at.%) are investigated. As measured in a previous study, this metallic glass exhibits three exothermic events during heating at 20 K/min in differential scanning calorimetry. However, based on the observation by transmission electron microscope, the first exothermic event is found not to correspond to the crystallization behavior but the structural relaxation, the precipitation of crystalline phase happens to the second one, and the nano-scale crystalline particles coarsen during the third one. On the other hand, although the as-cast Zr 20 Ti 20 Cu 20 Ni 20 Be 20 metallic glass fractures in an extremely brittle way in compression tests, the fractograph shows two types of features: One is mirror-like smoothness as an indicator of brittleness, and the other is vein-like pattern as a sign of plasticity. These different features are attributed to the fracture mode instead of the plasticity or toughness in metallic glass.

In the present paper, 10 vol%TiC/Ti–6Al–3Sn–3.5Zr–0.4Mo–0.75Nb–0.35Si composite produced via in situ casting technique was tested in the temperature range from room temperature to 900 °C and much attention was paid on the microstructural evolution during high-temperature tensile test. It was found that the variation of microstructures in deformation zones with strain exhibited different trends at different temperatures. Below 600 °C, dislocation density increased with strain over the entire strain range. As temperature increased to 700 °C, dislocations proliferated rapidly in the initial deformation and then dislocation annihilated through dynamic recovery. Above 800 °C, the variation of microstructures in deformation zones with strain was similar to that at 700 °C at the beginning but at higher strain, dynamic recrystallization (DRX) occurred, leading to the formation of equiaxed microstructure. Microstructural evolution in deformation zones corresponded to the variation of tensile stress–strain characteristics with temperature, reflecting the hardening or softening feature of matrix. Dynamic recovery ascribed to the flow softening of the composite at 700 °C, while flow softening is owing to dynamic recovery and DRX above 800 °C. In addition, matrix softening should show different trends in different temperature ranges.

A novel hierarchical structure of Ni 3 S 2 nanosheets coated on mesoporous NiCo 2 O 4 nanoneedles arrays was designed and investigated. Due to the positive synergistic effect of the two materials resulting from the three-dimensional coated structure, the as-prepared NiCo 2 O 4 /Ni 3 S 2 heterostructure hybrid exhibited excellent electrochemical performance with areal capacitance of 4569.1 mF cm −2 at current density of 1 mA cm −2 as well as remarkable cycling stability of 89.2% capacitance retention after 1000 cycles. The impressive results here may pave the way to development of high-performance electrode materials for supercapacitors.

In this paper, microstructural characterization and mechanical properties of 10 vol% TiC/Ti-6Al-3Sn-3.5Zr-0.4Mo-0.75Nb-0.35Si composite obtained at slow cooling rate has been discussed. Equiaxed or near-equiaxed α phase was formed in the composite when cooled from above the β-transus temperature at a cooling rate of 10 °C/min. This is due to the fact that α precipitates can heterogeneously nucleate on TiC particles during the slow-cooling process. It was obtained that the lattice disregistry between TiC and α precipitates was only 3.8%, which corresponds to the crystallographic orientation relationship of [2-1-10]α//[011]TiC; (0001)α//(1-11)TiC. The tensile results showed that heat treatment improved UTS and elongation, simultaneously, below 700 °C. The enhancement of UTS is mainly attributed to solid solution strengthening of C in matrix since about 5.5 vol% TiC dissolved into matrix after heat treatment. The obvious increase in room-temperature elongation is because of the formation of equiaxed microstructure and the reduction in the sizes of spheroidised TiC particles. With the increase of temperature, the discrepancy in UTSs of the as-cast and heat-treated composites became small.

In this paper, five types of TiC particle reinforced titanium matrix composites (TiC-PTMCs) were fabricated by casting route in order to investigate the influence of Zr, Mo and TiC on microstructures and tensile strengths of TiC-PTMCs. The increase of Zr content promoted the precipitation of eutectic TiC and refined primary TiC, while increasing Mo content led to the refinement of α lath. The composites with high Zr and Mo contents and low TiC content showed superiority in ultimate tensile strength (UTS) below 650 °C, whereas above 700 °C, high UTS was obtained in the composites with high TiC content and low Mo content. Below 650 °C, solid solution strengthening and fine grain strengthening of matrix make the largest contribution to the improvement of UTS. However, above 700 °C, solid-solution strengthening of Zr and the load bearing effect of TiC play a dominant role in the enhancement of UTS. Accordingly, effective routes for improving UTSs of TiC-PTMCs in different temperature ranges are different.

In this paper, three-step heat treatment was developed and performed on 8vol.%TiC/Ti–5.8Al–2Zr–1.3Mo–1V composite prepared by in situ casting route. This heat treatment leads to significant changes in microstructure and tensile properties. Matrix microstructure was refined obviously and fine TiC particles with average diameter of 3.6 μm were obtained. The tensile strength and elongation are all improved at room temperature and 600 °C and room-temperature elongation increases to 5.86%.

In present work, the glass-forming ability of Cu-Zr and Cu-Al systems has been estimated by utilizing a monolayer two-dimensional model. The structure of 2D Cu-Zr MGs can be simply characterized by three kinds of Voronoi polygons, i.e. pentagon, hexagon and heptagon, and the structural translational symmetry is broken down by the strong coupling effect between pentagon and heptagon, promoting the formation of MGs. Moreover, the larger bond lengths of Cu-Zr and Zr-Zr pairs are found responsible for the outstanding GFA of Cu-Zr system. The 2D model provides a promising avenue for accurately predicting the GFA of alloys of interest, which is important both in theoretical research and engineering.

High Nb-containing TiAl alloys with different aluminum content were prepared by vacuum induction casting technology, and then processed via directional solidification in a Y2O3-coated Al2O3 crucible. The effect of aluminum content on the metal and coating interface, chemical composition, and phases at the interfaces were evaluated. The variations of microhardness of the samples from surface to interior were presented. The results showed that there is no significant difference between the matrix structure of TiAl alloy with different aluminum content. Nevertheless, with increasing aluminum content in the melt, the thickness of the reaction layer decreased. Moreover, the elements diffusion distance and hardness also showed an apparent decrease with the increasing of aluminum content. Besides inherent phases in the melt, simultaneous precipitation of Al2O3 particles also occurred.