Amorphous Alloys Research Articles

Continuous polyamorphic transition in high-entropy metallic glass

Polyamorphic transition (PT) is a compelling and pivotal physical phenomenon in the field of glass and materials science. Understanding this transition is of scientific and technological significance, as it offers an important pathway for effectively tuning the structure and property of glasses. In contrast to the PT observed in conventional metallic glasses (MGs), which typically exhibit a pronounced first-order nature, herein we report a continuous PT (CPT) without first-order characteristics in high-entropy MGs (HEMGs) upon heating. This CPT behavior is featured by the continuous structural evolution at the atomic level and an increasing chemical concentration gradient with temperature, but no abrupt reduction in volume and energy. The continuous transformation is associated with the absence of local favorable structures and chemical heterogeneity caused by the high configurational entropy, which limits the distance and frequency of atomic diffusion. As a result of the CPT, numerous glass states can be generated, which provides an opportunity to understand the nature, atomic packing, formability, and properties of MGs. Moreover, this discovery highlights the implication of configurational entropy in exploring polyamorphic glasses with an identical composition but highly tunable structures and properties.

Thermal effects on the mechanical behavior of CuZr metallic glasses

Thermal effects on the mechanical behavior of CuZr metallic glasses

Catalytic properties of Fe-based amorphous alloys based on LPBF

Laser Powder Bed Fusion (LPBF) additive manufacturing technology has the advantages of high forming accuracy and rapid cooling. It is expected to overcome the limitations of forming difficulties in amorphous alloys and provide a new opportunity for the production of amorphous alloy structural parts. In this paper, FeSiBCrC amorphous alloy powder was used to prepare Fe-based amorphous alloy samples by LPBF technology. In view of the excellent properties of Fe-based amorphous alloy, the catalytic degradation performance of Fe-based amorphous alloy samples prepared by LPBF was systematically investigated. The catalytic degradation performance of the Fe-based amorphous alloy was optimised by changing the reaction conditions. In the methyl orange (MO) dye degradation experiment, the degradation rate reached 90.99 % within 10 min. Increasing the sample dosage and reaction temperature can improve the degradation efficiency, but excessive addition of H2O2, raising the pH and the initial dye concentration will reduce the degradation efficiency. In addition, in the cyclic catalytic experiment, it was found that it has self-renewing performance, and the degradation efficiency was still higher than 95 % within 35 min after repeated degradation 12 times. Fe-based amorphous alloy catalysts prepared on the basis of LPBF have good catalytic activity and will provide economical and effective technical support for wastewater treatment.

Mechanical properties and deformation behavior of Zr-based bulk metallic glass composites reinforced with tungsten fibers or tungsten powders

Mechanical properties and deformation behavior of Zr-based bulk metallic glass composites reinforced with tungsten fibers or tungsten powders

Research on Exposure to Salt Water Environment of Fe-based Amorphous Alloy Coating Fabricated by Twin Wire Arc Spray

Research on Exposure to Salt Water Environment of Fe-based Amorphous Alloy Coating Fabricated by Twin Wire Arc Spray

Solid-state surfactant templating for controlled synthesis of amorphous 2D oxide/oxyhydroxide nanosheets

As a member of 2D family, amorphous 2D nanosheets have received increasing attention due to their unique properties that are distinct from crystalline 2D nanosheets. However, compared with the vast library of crystalline 2D nanosheets, amorphous 2D nanosheets are still infancy due to the lack of an efficient synthetic approach. Here, we present a strategy that yields a library of 10 distinct amorphous 2D metal oxides/oxyhydroxides using solid-state surfactant crystals. A key feature of this process is a stepwise reaction using solid surfactant; the solid-state surfactant crystals have metal ions arranged in the interlayer space, and hydrolysis of the metal ions leads to the formation of isolated clusters in the surfactant crystals via limited condensation reactions. Immersing the surfactant crystals in formamide promotes nanosheet formation through the self-assembly of clusters by templating the morphologies of the crystals generated from surfactants crystals. Our approach opens a flatland in amorphous 2D world.

Crystalline Metal–Organic Framework Coatings Engineered via Metal–Phenolic Network Interfaces

AbstractCrystalline metal–organic frameworks (MOFs) have garnered extensive attention owing to their highly ordered porous structure and physicochemical properties. However, their practical application often requires their integration with various substrates, which is challenging because of their weakly adhesive nature and the diversity of substrates that exhibit different properties. Herein, we report the use of amorphous metal–phenolic network coatings to facilitate the growth of crystalline MOF coatings on various particle and planar substrates. Crystalline MOFs with different metal ions and morphologies were successfully deposited on substrates (13 types) of varying sizes, shapes, and surface chemistries. Furthermore, the physicochemical properties of the coated crystalline MOFs (e.g., composition, thickness) could be tuned using different synthesis conditions. The engineered MOF‐coated membranes demonstrated excellent liquid and gas separation performance, exhibiting a high H2 permeance of 63200 GPU and a H2/CH4 selectivity of 10.19, likely attributable to the thin nature of the coating (~180 nm). Considering the vast array of MOFs available (>90,000) and the diversity of substrates, this work is expected to pave the way for creating a wide range of MOF composites and coatings with potential applications in diverse fields.

Revealing the effect of annealing at Tg on the crystal growth in Au49Ag5.5Pd2.3Cu26.9Si16.3 metallic glass via nanocalorimetry

In this study, Au49Ag5.5Pd2.3Cu26.9Si16.3 metallic glass is annealed at Tg and its impact on crystal growth is demonstrated with nanocalorimetry. With annealing following the rapid quenching, an amorphous phase free of nuclei, a relaxed amorphous phase, an amorphous phase with nuclei, and an amorphous phase with crystals are sequentially produced. With the reheating at rates ranging from 100 to 50,000 K/s, these four stages are quantitatively distinguished. Additionally, crystal growth behaviors of these four stages are demonstrated by the Kissinger and Mauro-Yue-Ellison-Gupta-Allan model. For the quenched and relaxed amorphous phases, the apparent crystallization activation energy (Ea) decreases with increasing heating rate, with a noticeable upward deviation at ultrahigh heating rates. When nuclei and crystals form in the amorphous phase, Ea keeps decreasing with the heating rate. As the annealing time increases, the maximum growth rate (umax) exhibits a monotonic increase while the temperature corresponding to umax displays a maximum.

Mössbauer analysis of (FeNiCrSiB) amorphous alloy ribbons

The fabrication of iron-based amorphous alloys was executed through the utilization of the melt-spinning technique, followed by a characterization employing X-ray diffraction (XRD), scanning electron microscopes (SEM) and transmission Mössbauer spectroscopy (MS). The studies were performed on Fe76-xNixCr4Si8B12 (where x = 0, 4, 12, and 30) metallic glasses in the form of ribbons. Mössbauer spectroscopy enables the exploration of the localized surroundings of iron (Fe) atoms within the glassy state, revealing alterations in the amorphous structure attributed to variations in the addition of Nickel (Ni). The broad lines in the Mössbauer spectra of ferromagnetic amorphous ribbons are a result of the distribution of non-equivalent iron sites and interatomic distances. The line intensity ratio suggests a preferential orientation of iron moments within the ribbon plane. The results derived from Mössbauer analysis indicate that the amorphous alloys feature bimodal distributions of the hyperfine fields. Changes in the nickel content within the alloys impact the disorder in the as-cast state and concurrently influence parameters such as the average hyperfine field <Hhyp>, the average radius R of the first coordination shell, and the number of nearest neighbor Fe atoms.

Intermittent cluster dynamics and temporal fractional diffusion in a bulk metallic glass

Glassy solids evolve towards lower-energy structural states by physical aging. This can be characterized by structural relaxation times, the assessment of which is essential for understanding the glass’ time-dependent property changes. Conducted over short times, a continuous increase of relaxation times with time is seen, suggesting a time-dependent dissipative transport mechanism. By focusing on micro-structural rearrangements at the atomic-scale, we demonstrate the emergence of sub-diffusive anomalous transport and therefore temporal fractional diffusion in a metallic glass, which we track via coherent x-ray scattering conducted over more than 300,000 s. At the longest probed decorrelation times, a transition from classical stretched exponential to a power-law behavior occurs, which in concert with atomistic simulations reveals collective and intermittent atomic motion. Our observations give a physical basis for classical stretched exponential relaxation behavior, uncover a new power-law governed collective transport regime for metallic glasses at long and practically relevant time-scales, and demonstrate a rich and highly non-monotonous aging response in a glassy solid, thereby challenging the common framework of homogeneous aging and atomic scale diffusion.

Kinetics study and fragility of (Cu50Zr43Al7)98Y2 bulk metallic glass

Crystallization transformation kinetics and fragility of (Cu50Zr43Al7)98Y2 bulk metallic glass (BMG) were investigated at non-isothermal and isothermal conditions by differential scanning calorimetry. Activation energies for the BMG were calculated for the glass transition, onset crystallization, and crystallization peak using various methods of non-isothermal analysis. Results suggested that atomic rearrangement during glass transition is more complex than crystallization, and growth poses greater challenges than nucleation. Isothermal analysis conducted in the supercooled liquid region provides evidence of crystallization being controlled by diffusion, with a calculated mean Avrami exponent of 2.2. Additionally, the findings of fragility studies and kinetic studies demonstrated a strong correlation with the glass-forming ability (GFA), thereby validating the high GFA of the BMG analyzed in this study. Thus, this research results provide a detailed understanding of the complex crystallization kinetics, thermal behavior, and GFA of (Cu50Zr43Al7)98Y2 BMG, emphasizing its potential in materials science applications.

Molecular dynamics simulation of the microstructural evolution in FeCuNi metallic glass under neutron irradiation

Investigating the microstructural characteristics of metallic glasses (MGs) under high-energy irradiation is of great importance for their industrial applications. In this study, molecular dynamics simulations of FeCuNi MG under neutron irradiation have been carried out, and the microstructural evolution has been systematically investigated by the largest standard cluster analysis (LaSCA). It is found that both topologically close-packed (TCP) and icosahedral structures in MG exhibit significant self-healing ability under irradiation. However, the TCP structures are quantitatively more dominant and thus can more rationally explain the structural self-healing mechanism of irradiated MG. Furthermore, during the irradiation process, the large-sized TCP clusters in the MG split into many small-sized clusters. However, due to the inherent self-healing ability of the TCP structures, these split clusters recombine into large-sized clusters after the irradiation ends. In summary, the results of this study are expected to provide theoretical guidance for the development of new high-performance reactor materials.

Tailoring of Novel Amorphous RuS2/ZrS2/MWCNT Nanocomposite Platform as a Dual Sensor for the Detection for Water Pollutant Indigo Carmine

The present study focuses on synthesizing amorphous nanocomposites of RuS2/ZrS2/MWCNT and exploring their potential for modifying electrodes and detecting indigo carmine dyestuff. Amorphous materials have recently garnered significant attention due to their ability to control material properties through their distinct nature. Transition metal dichalcogenides, or TMDs, are being extensively used in various applications such as catalysis, dye degradation, and so on. Amorphous transition metal sulphides, due to their heightened active sites, exhibit higher performance. This study presents the first-ever successful production of two amorphous metal sulphides that are doped with multi-walled carbon nanotubes. The resulting novel material was used to detect indigo carmine with high efficiency. The detection range was wide, spanning from 0.1 μM to 300.0 μM, and the limit of detection was 0.08 μM. These results demonstrate that the material outperforms most previously reported studies in this field. The technique employed was both simple and innovative, and it was used on both Glassy Carbon Electrode (GCE) and Screen-Printed Electrode (SPE) systems. It was effectively evaluated for the detection of the dye in water samples as well as food and pharmaceutical samples.

Stability of oxide crucibles and implications for the fabrication of Zr-based bulk metallic glass master alloys

In this study, a systematic evaluation was conducted on the performance of Al2O3, MgO, BaZrO3 and Y2O3 crucibles for melting Zr-based bulk metallic glass master alloys. The interaction between the crucibles and the alloy melts was investigated, focusing on the effect of crucible type and the addition of Y element on the interaction. The results indicated that the relative stability of the evaluated oxide crucibles, in order of decreasing interaction extent, followed the sequence: MgO→Y2O3→Al2O3→BaZrO3. The grading did not follow the free energy data of the formation of these oxides. It was because that the Y combined with O in the alloy melts to form Y2O3 products, which adhered to the inner surface of the crucible. This further prevented the dissolution of the crucible refractory. Among the tested crucibles, the Y2O3 product layer exhibited the most complete structure on the surface of BaZrO3 crucible, thereby minimizing both the corrosion of the crucible and the contamination of the alloy melts.

Effect of Cu addition on the properties of Pd-based metallic glasses by experimentation and molecular dynamics simulations

The effect of trace Cu element additions on the properties of Pd-based amorphous alloys was investigated by a combination of experimental and molecular dynamics (MD) simulations. Thin ribbons of Pd40Ni40P20 and containing different proportions of Cu (1 %, 3 %, and 5 %) were prepared, analyzed by X-ray diffraction (XRD) to determine the phase structure, tested for their thermal properties by differential scanning calorimetry (DSC), and nanoindentation to test their mechanical properties. Meanwhile, the amorphization process and compression behavior of these alloys were simulated by MD simulation, and the microstructures of the alloys were resolved by using the radial distribution function (RDF) and the coordination number distribution function (PDF), and the glass transition temperatures (Tg) were deduced from the energy variations. The Voronoi polyhedral analyses showed that the addition of trace amounts of Cu altered the content of the specific clusters, which affected the macroscopic mechanical properties. Both nanoindentation experimental and simulation results confirmed that the addition of trace Cu reduces the Tg and improved the mechanical properties of the Pd40Ni40P20 alloy while maintaining the amorphous structure.

Self-oxidized AgCu nano-foam with unique phase structure for ethanol sensors breaking through the trade-off between sensitivity and upper linear limit

Comparing to gas ethanol sensors, electrochemical ethanol sensors are promising owing to the low operating temperature, high sensitivity and good accuracy. Common electrochemical ethanol sensors suffer from a general trade-off relationship between sensitivity and upper limit for linear detection. In this work, facile self-oxidized AgCu nano-foam is obtained by simply dealloying of Mg65Ag12.5Cu12.5Y10 metallic glass ribbon in citric acid, which breaks through the trade-off by showing an ultra-high upper linear limit of 1.5 M and good sensitivity of 109.6 μA mM-1 cm-2. Combined experiment and simulation investigations confirm that the ligaments of the AgCu nano-foam is composed of surfaces with interlacing Ag and Cu2O grains that are driven by surface energy, and cores consist of Ag and Cu grains that result from phase separation. Such phase structures, coupled with the geometry merits, lead to fast oxidation dynamics, abundant electroactive sites, good reversibility and stable microstructure, which results in high upper linear limit and a sensitivity improvement of ∼30 times comparing to Cu nano-foam. This work develops a candidate material for high performance sensing of concentrated ethanol, and verifies a promising strategy to prepare efficient catalysts by multilevel-design of geometry and phase structure.

Unraveling the interrelation between process parameters and defects to enhance the strength of laser additively manufactured CuZrAlTi bulk metallic glass

Laser powder bed fusion (LPBF) enables the production of large and intricately shaped bulk metallic glasses (BMGs); however, the current strength of LPBF-fabricated BMGs is significantly lower than their cast counterparts due to defects generated during the LPBF process in the as-built BMGs. In this study, considering the viscosity characteristics of BMG melts and their impact on melt pool characteristics, we investigated the relationship between LPBF parameters, structural characteristics, and defects in a selected Cu45Zr45Al6Ti4 BMG. Our findings revealed a transition of the melt pool from conduction mode to keyhole mode and subsequently to extended mode with increasing laser power. Furthermore, we explored how melt pool characteristics influence defects such as pores, heat affected zone (HAZ), and crystalline phase in the as-built Cu45Zr45Al6Ti4 BMG. Under optimized LPBF parameters, we successfully fabricated nearly fully amorphous Cu45Zr45Al6Ti4 BMG samples with high density (>99%) and absence of cracks. The printed samples exhibited a compressive strength of 1839 MPa comparable to their cast counterparts while achieving an impressive tensile strength value of 920 MPa, currently the highest reported for CuZr-based BMGs. This study enhances our understanding of the intrinsic relationship between LPBF parameters, melt pool characteristics, defects, and mechanical properties of LPBF-fabricated BMGs while providing a new parameter optimization strategy for reducing defects and achieving high strength in BMGs.

Unravelling the relation between free volume gradient and shear band deflection induced extra plasticity in metallic glasses

Previous experiments have revealed that the controllable introduction of structural gradients in metallic glasses (MGs) can endow the materials with extra plasticity due to the gradient-induced deflection of shear bands. However, the relation between the spatial structural gradient and the initiation of shear band deflection remains unclear. The current study has been focused on investigating the relationship between the improved mechanical properties of MGs and structural gradients specified by the distribution of the intrinsic free volume. Molecular dynamics (MD) simulations are firstly performed on homogeneous MG models containing various initial free volume values, showing that the shear band angle increases with decreasing free volume under uniaxial compression, whereas higher shear band angle is observed under uniaxial tension with increasing free volume. Based on the asymmetric behaviors of MGs under compression and tension, a theoretical model is developed to quantitatively characterize the influence of free volume on the mechanical response of MGs, which incorporates a failure criterion based on free volume generation during external loadings. The model can be further utilized to interpret and predict the fracture strain, shear band angle, maximum stress, and fracture surface morphology of gradient structured MGs in both simulations and experiments. The relationship between free volume gradient and shear band deflection induced extra plasticity established in this study provides valuable guidance for the structural design of MGs with enhanced mechanical properties.

Dynamic Fracture Kinetics of Titanium-Based Bulk Metallic Glass and Its Composites

Dynamic Fracture Kinetics of Titanium-Based Bulk Metallic Glass and Its Composites

Amorphous-Crystalline Heterostructured Nanoporous High-Entropy Alloys for High-Efficiency pH-Universal Water Splitting.

Developing high-efficiency durable electrocatalysts in wide pH range for water splitting is significant for environmentally-friendly synthesis of renewable hydrogen energy. Herein, a facile method by dealloying designable multicomponent metallic glass precursors is reported to synthesize amorphous-crystalline heterostructured nanoporous high-entropy alloys (AC-HEAs) of CuAgAuPtPd, CuAgAuIrRu, and CuAgAuPtPdIrRu, heaped up by nanocrystalline particles with an average size of 2-3nm and the amorphous glued phase. The synthesized AC-HEA-CuAgAuPtPd owns highly catalytic performances for hydrogen evolution reaction (HER), with 9.5 and 20mV to reach 10 mA·cm-2 in 0.5m H2SO4 and 1.0m KOH, and AC-HEA-CuAgAuIrRu delivers 208 and 200mV for oxygen evolution reaction (OER). Moreover, a two-electrode electrolyzer made of the AC-HEA-CuAgAuIrRu bifunctional electrodes exhibit a low cell voltage of 1.48 and 1.49V in the acidic and alkaline conditions at 10 mA·cm-2 for overall water splitting. Combining the enhanced catalytic activities from nanoscale amorphous structure and atom-level synergistic catalyst in AC-HEAs provides an effective pathway forpH-universal electrocatalysts of water splitting.