Search

Abstract: This paper provides an in-depth investigation into the effects of environmental temperature and sliding speed on the tribological behaviour of a bulk metallic glass (BMG), Ti40Zr25Ni3Cu12Be20. The sliding was between the BMG and EN26 steel. The results showed that the wear resistance of the BMG increases with environmental temperature when it is below the material's glass transition temperature (T g); and that the steady friction coefficient does not vary notably. The stress on the contacting asperities influences the wear rate. Wear debris also play an important role at elevated temperatures, which could even change the wear mechanism from 2-body abrasion to 3-body abrasion under certain environmental temperature. The BMG remains amorphous, even at an environmental temperature close to its T g, indicating that frictional heating controls the microstructure transformation during contact sliding. Under a high environment temperature, a dissimilar material layer could emerge at the sliding interface, leading to a significant reduction in wear rate. [Copyright &y& Elsevier]

Abstract: This paper investigates the friction and wear properties of bulk metallic glass Ti40Zr25Ni3Cu12Be20 (at%) sliding against EN26 steel in a dry environment. It was found that frictional heating plays a central role in the variation of the tribological properties of the material. When the temperature rise does not cause phase transformation but introduces plasticity, the friction coefficient decreases and the wear rate increases. A further temperature rise brings about a wear mode transition from brittle to ductile wear. When the temperature is above the glass transition temperature of the material, crystal particles emerge in the deformed subsurface, and turns the wear to a brittle mode again, even though superplastic deformation of the material also takes place in conjunction with such phase transformation. As a result, friction coefficient increases and wear rate decreases. [Copyright &y& Elsevier]

Abstract: Inelastic deformation of metallic glass is through shear banding, characterized by significantly localized deformation and emerged expeditiously under certain stress state. This study establishes a new constitutive model addressing the physical origin of the shear banding. In the modeling, the atomic structural change and the free volume generation are embodied by the plastic shear strain and the associated dilatation. The rugged free energy landscape is adopted to naturally reflect the rate-independent flow stress and flow serrations. Based on this, the conditions for the onset of shear banding instability are established, which enables the explicit calculation of the shear band inclination angle and its extension speed. The study concludes that shear band angle is significantly influenced by the diltancy factor and pressure sensitivity, that a shear band does not increase its thickness once emanated from a deformation unit, that the spreading speed of a shear band is intersonic, and that more shear bands, which lead to higher ductility, can be induced by high strain rates or by the introduction of a second material phase. The analysis also demonstrates that the ductility of metallic glass depends on the sample geometry and/or the stress state. [Copyright &y& Elsevier]

Abstract: Cu46Zr47Al7 bulk metallic glass (BMG) alloys with different microstructure were fabricated by adjusting the casting size. For the monolithic BMG with different diameters, the measured plasticity decreased with the increase of sample size and was mainly due to the sliding of two undeveloped parts along main shear band. Excellent compression plastic strain (∼13.2%) was obtained for the marginal BMG containing in situ nanocrystals with sample size up to 3.5mm in diameter where multiple shear bands formed. It is suggested that failure of BMG samples will occur when the temperature rise in shear layer reaches a critical value. The temperature rise is closely related to the sample size and stress drop, moreover, it can be controlled through adjusting final stress drop (via sample size) and increment rate of stress drop (via microstructure), resulting in enhanced plasticity. [Copyright &y& Elsevier]

Abstract: The corrosion behavior of Cu x Zr100−x (x =40, 50 and 60at.%) metallic glasses prepared by rapid quenching were investigated by means of electrochemical polarization measurements and immersion tests in 0.01 and 0.1mol/L HCl solutions, respectively. The influence of the alloy composition on morphological and compositional characteristics of pit regions was discussed in detail. All the investigated Cu–Zr metallic glasses are susceptible to pitting corrosion due to the adsorption of the Cl− ions. The pit morphology is strongly dependent on the Cu concentration of the alloy. A more severe corrosion on the wheel sides compared with the air sides demonstrates that the surface characteristics play an important role in influencing the corrosion resistance of the glassy alloys. [Copyright &y& Elsevier]

To achieve plasticity of Ti-based bulk metallic glasses (BMGs) without sacrificing their high strength, the microstructure of Ti50Cu20Ni24Sn3Si2B1 alloy was tailored to form in situ composites. The cast rods consist of micrometer-sized NiTi dendrites surrounded by a thin metallic glass network along with a fine CuTi3 phase. The rods show high strengths of ∼1900–2250MPa and plastic strains of ∼4.5–7.8%, which are superior to the monolithic Ti-based BMGs. The microstructure–property correlations and the deformation behavior are investigated. [Copyright &y& Elsevier]

Abstract: The plastic deformation behavior of Ce68Al10Cu20Nb2 and Ce70Al10Cu20 bulk metallic glasses (BMGs) at room temperature was studied by depth-sensing nanoindentation and microindentation. It is shown that the two BMGs exhibit a continuous plastic deformation without distinct serration at the all of the studied loading rates during nanoindentation. An obvious creep displacement was observed during the holding-load segment at the maximum load for the two alloys, and the magnitude of creep during holding-load increases with loading rate. The subsurface plastic deformation zone of the two BMGs after indentation at various loading rates was investigated through bonded interface technique using depth-sensing microindentation. A highly developed shear banding pattern can be observed in the plastic deformation region, though the global load–depth curves illuminate a “homogeneous flow”. The plastic deformation behavior of the Ce-based BMGs during indentation measurements is discussed in terms of localized viscous flow. [Copyright &y& Elsevier]

Abstract: Ni60Nb40 metallic glass powders were prepared by mechanical alloying and subsequently combined with Al to form an Al–30wt.% Ni60Nb40 metal matrix composite (MMC). The crystallization of the Ni60Nb40 metallic glass reinforcements and their reaction with the Al matrix during preparation of the MMC were investigated in a differential scanning calorimeter (DSC) upon isothermal annealing. The comparison of the DSC curves of the Ni60Nb40 metallic glass and of the Al–30wt.% Ni60Nb40 composite shows that the amorphous Ni60Nb40 particles have a very strong resistance against reaction with Al but reaction occurs after crystallization of the metallic glass. The analysis of the isothermal annealing DSC curves gives an activation energy of crystallization of the Ni60Nb40 metallic glass of 724kJ/mol. The interfacial reaction between Al and the Ni60Nb40 reinforcements is mainly controlled by diffusion. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results indicate that during the interfacial reaction, Ni diffuses from the Ni60Nb40 particles to react with Al and form Al3Ni. At the same time, Al diffuses into the reinforcement particles to react with remaining Nb and form Al3Nb. [Copyright &y& Elsevier]

Abstract: Ball-milled Ti50Cu18Ni22Al4Sn6 amorphous powders were consolidated by equal channel angular extrusion (ECAE) near the glass transition temperature. A density of about 97% was achieved. The incomplete densification was a result of the powders experiencing insufficient viscous flow as they partially crystallized into the NiTi intermetallic phase during the ECAE processing. Partial devitrification led to a slight increase in the glass transition temperature (T g) and minor decrease in the crystallization temperature (T x ), when compared with the starting amorphous powders. However, the width of the supercooled liquid region for the ECAE samples remained large, ∼54K. Under uniaxial compression, the ECAE consolidated samples failed prematurely before yielding due to brittle failure possibly triggered by the pre-existing minor flaws in the specimens, resulting in a much lower compressive fracture strength with respect to that estimated from the microhardness. [Copyright &y& Elsevier]

Abstract: The Ti50Cu18Ni22Al4Sn6 multicomponent alloy was chosen as base alloy due to a complete glass formation under ball milling and a sizable supercooled liquid region, ΔT x =66K. The mixtures of prealloyed Ti50Cu18Ni22Al4Sn6 fragments with CrB or TiB2 particles up to 30vol.% were mechanically milled to fabricate the boride/Ti-based glassy alloy composites. The structural features of the as-milled products were characterized using X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. In the ball-milled composites, the CrB or TiB2 particles with sizes ranging around 10–200nm are dispersed in the Ti-based glassy alloy matrix. Similar to the Ti50Cu18Ni22Al4Sn6 glassy alloy without any borides, a well-defined glass transition temperature, T g, and a wide supercooled liquid region, ΔT x, are observed also for the boride-containing composites. Furthermore, the glass transition and thermal stability of supercooled liquid for the matrix alloy in the composites are dependent on the fraction of boride addition. In the case of CrB addition, the ΔT x value of glassy phase matrix was reduced due to a strong fraction dependence of the T g than that of the T x, remaining at about 60K for boride fractions less than 15vol.%. In contrast, both the T g and T x of the TiB2-containing composites were raised with increasing TiB2 fraction up to 30vol.%, resulting in no significant change for the ΔT x. [Copyright &y& Elsevier]

Abstract: Two Sn-containing Ti-based multicomponent alloys, Ti50Cu35Ni12Sn3 and Ti50Cu18Ni22Al4Sn6, were chosen to investigate the amorphization of pre-alloyed fragments under high-energy ball milling. For comparison, the amorphous alloy ribbons with the same compositions were also prepared using melt-spinning method. Amorphous nature of the as-prepared samples was characterized using X-ray diffraction, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). For the ball-milled (BM) Ti50Cu35Ni12Sn3 alloy, the glass formation is predominant but a small fraction of the α-Ti nanocrystals still remains unreacted. In contrast, the complete amorphization can be achieved in the ball-milled Ti50Cu18Ni22Al4Sn6 alloy. In both cases, thermal properties of the ball-milled glassy alloys are comparable to those of the melt-spun (MS) glasses, exhibiting a distinct glass transition and wide supercooled liquid region about 60K. The amorphization extent in the final milled products is associated with whether the α-Ti phase exists in the initial microstructure of the alloys as starting materials. [Copyright &y& Elsevier]

Presents a study which investigated glass formation in a (Ti,Zr,Hf)-(Cu,Ni,Ag)-Al high-order alloy system by mechanical alloying. Structural features of the alloy system; Observations on the behavior of the high-order alloy upon completion of the primary nanocrystallization; Usual methods in preparing glassy alloys with supercooled liquid regions.

Metallic glasses with long-range disordered atomic structure have recently been attracted a great deal of research attention in catalytic field. Compared to crystalline materials, the metallic glasses present many advanced catalytic properties, yet the catalytic mechanism is not sufficiently understood. In this work, an Fe 78 Si 9 B 13 glassy ribbon manufactured by melt-spinning method was applied for the first time to compare its activation behavior on three peroxides, including hydrogen peroxide (H 2 O 2 ), persulfate (PS) and peroxymonosulfate (PMS). It was shown that Fe 78 Si 9 B 13 metallic glass had exceptionally high capability for activating these three common peroxides to produce reactive radicals ( OH and/or SO 4 • − ). The dominant species of H 2 O 2 in this work was demonstrated as hydroxyl radical ( OH) while the PS and PMS activation mainly generated sulfate radical (SO 4 • − ). The order of predominant radical generation rate by Fe 78 Si 9 B 13 activation under UV−vis irradiation was PS > H 2 O 2 > PMS. The relative contribution of sulfate radical (SO 4 • − ) in PS activation was 78% compared to 61% in PMS. All the peroxides activated by Fe 78 Si 9 B 13 metallic glass presented a radical generation rate at least ∼2 times higher than other iron-containing materials. Crystal violet (CV) dye was used to investigate the catalytic performance of Fe 78 Si 9 B 13 metallic glass for peroxides, which showed an ultrafast dye degradation rate with completely color removal within 15 min. The radical evolution mechanisms for H 2 O 2 , PS and PMS activation were also investigated. The change in surface morphology of ribbon after 5th run reused indicated that the inclusions of Si leading to formation of SiO 2 layer played an important role in the surface stability of ribbons. [ABSTRACT FROM AUTHOR]

Abstract: The atomic rearrangement in metallic glass (MG) is a dynamics process. However, this problem has always been investigated within the quasi-static limit of the material. As such, the physical mechanisms of how the local rearrangements nucleate and coalesce into shear bands have not been fully understood. This study is to clarify the issue with the aid of a systematic molecular dynamics analysis. The present study unveils that the underlying mechanism of plastic deformation is through the rearrangement of atoms, characterized by the sudden surge in kinetic energy or strain rate of a local region, and that the shear banding is a stress-driven dynamic coalescence of these rearranging clusters, propagating in the speed of a shear wave. The ratio of the internal strain rate in forming a cluster to the applied strain rate is a measure of the severity of the local atomic rearrangement. The larger the severity, the easier the shear banding forms. The additional kinetic energy associated with the atom rearrangement in clustering is due to the descending of the potential energy after crossing the energy barrier. As temperature increases, the thermal vibration energy becomes larger than the barrier height, leading to thermal activations in MG and hence giving rise to a homogeneous deformation. [Copyright &y& Elsevier]

Abstract: Cu46Zr47Al7 ternary bulk metallic glass (BMG) and its composite containing CuZr crystallizing phases were obtained through water-cooled copper mold casting. There is an obvious microstructure transition of CuZr crystallizing phase due to the decrease in the cooling rate: disperse small dendrites–regular radial dendrites–martensite phase. Under compression, the CuZr crystallizing phases particularly for martensite phase yield first and stimulate the formation of multiple shear bands in the matrix, which enhanced the ductility of the composite. The quasi-static compression fracture surface of the BMG its composites display a mixture of three distinct patterns: vein-like, smooth regions and river-like patterns. The river-like pattern was related with the secondary shear bands or tertiary shear bands and its area fraction on the fracture surface was dependent on the plasticity. [Copyright &y& Elsevier]

Abstract: The deformation behavior and the effect of the loading rate on the plastic deformation features in (numbers indicate at.%) Ce60Al15Cu10Ni15, Ce65Al10Cu10Ni10Nb5, Ce68Al10Cu20Nb2, and Ce70Al10Cu20 bulk metallic glasses (BMGs) were investigated through nanoindentation. The load–displacement (P–h) curves of Ce65Al10Cu10Ni10Nb5, Ce68Al10Cu20Nb2, and Ce70Al10Cu20 BMGs exhibited a continuous plastic deformation at all studied loading rate. Whereas, the P–h curves of Ce60Al15Cu10Ni15 BMG showed a quite unique feature, i.e. homogeneous plastic deformation at low loading rates, and a distinct serrated flow at high strain rates. Moreover, a creep deformation during the load holding segment was observed for the four Ce-based BMGs at room temperature. The mechanism for the appearance of the “anomalous” plastic deformation behavior in the Ce-based BMGs was discussed. [Copyright &y& Elsevier]

During spark plasma sintering (SPS), the gas atomized powders experience a sequence of densification mechanisms of particle arrangement, viscous flow, and high temperature creep concurrent with grain growth. However, after short time ball-milling of the original powders, the dramatic change of powder shape affects the thermodynamics (densification mechanisms) and kinetics (mass transfer) of powder densification based on the evolution of characteristic microstructure and densification data. In addition, we establish a theoretical framework to determine an atomic diffusivity D T, by incorporating the contribution of the applied pressure to the densification kinetics. Furthermore, the D T can be utilized to govern powder densification during SPS. Accordingly, a larger D T associated with the irregular metallic glass powder gives rise to faster powder densification, as compared with the original spherical powder without mechanical milling. Image 1 • Effect of powder shape on densification mechanism of metallic glass powders was investigated. • Effect of powder shape on mass transfer of metallic glass powders was investigated. • Large D T associated with irregular powder shape enhances powder densification. [ABSTRACT FROM AUTHOR]

Abstract Metallic glasses (MGs) with their intrinsic disordered atomic structure and widely controllable atomic components have recently emerged as fascinating functional materials in wastewater treatment. Compared to crystalline alloys, the less-noble atomic components in monolithic metallic glass are more efficient to be selectively dissolved during dealloying process. This work reported a facile chemical dealloying approach to fabricate a void channels-like structured MG with the elemental components of Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 for methylene blue (MB) degradation. Results indicated that the dealloyed Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 MGs with the void channels-like morphology presented a significant improvement of catalytic efficiency and reusability. The dye degradation reaction rate (k obs) of the dealloyed Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 MGs presented 3 times higher than their as-spun MGs. More importantly, the dealloyed Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 MGs can be reused up to 25 times without significantly loosing catalytic efficiency. It was also found that the dealloyed Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 MGs exhibited a greater corrosion resistance in the simulated dye solution compared to the as-spun ribbons, demonstrating a robust self-healing ability in catalytic activity. This work provides a novel view for designing MG catalysts with high efficiency and stability in worldwide energy and environmental concerns. Graphical abstract Image 1 Highlights • A void channels-like structured melt-spun metallic glass is reported. • Dealloyed metallic glasses show 3 times higher reaction rate than counterparts. • Dealloyed Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 ribbons can be reused for 25 times. • A strong corrosion resistance in dealloyed Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 ribbons is studied. [ABSTRACT FROM AUTHOR]

Abstract Physical correlation between structural heterogeneity and plastic flow of metallic glasses (MGs) is crucial for the understanding of MGs' deformation mechanism. In this work, different degrees of structural heterogeneity are introduced into Zr-based MGs through different cooling rates casting. The effect of structural heterogeneity on serrated flow behavior was studied. The findings demonstrate that there exists a tendency that serration flow dynamics of the MGs transforms from a chaotic state to a self-organized critical state with increased inhomogeneity. The established correlation between structural heterogeneity and serrated flow behavior shows that the higher degree of structural heterogeneity facilitates a higher frequency of interaction and multiplication of shear bands by increasing nucleation sites, and then promotes serrated flow behavior to be more homogeneous in time and space, thereby induces transformation of dynamics behavior and improves the plasticity. The obtained results shed light on deformation mechanism of plastic flow and provide a new insight into the plasticity of MGs. Graphical abstract Image 1 Highlights • Different degrees of structural heterogeneity were obtained under different cooling rates. • Serrated flow behaviors in metallic glasses with different internal structures were investigated. • Increased structural heterogeneity induces a transformation in dynamics from chaotic to a self-organized critical state. • Deformation mechanism of metallic glasses was discussed. • Large plasticity is ascribed to high degree of structural heterogeneity dominating the dynamics of shear bands. [ABSTRACT FROM AUTHOR]

Exploring functional applications as heterogeneous catalysts is an active topic for metallic glasses (MGs). Although recent advances have shown that the MGs with disordered atomic packing structure are indeed having superior catalytic reactivity for wastewater remediation, the catalytic mechanism is not yet clear. Herein, crystallization in melt-spun Fe 78 Si 9 B 13 glassy ribbons was applied at various annealing temperatures for understanding the catalytic mechanism. The crystalline structures and volume fractions of the crystallized α-Fe in the as-received and annealed glassy ribbons were fully characterized. The results showed that Fe 78 Si 9 B 13 glassy ribbons with disordered atomic structure present enhanced catalytic performance for peroxymonosulfate (PMS) activation compared to annealed counterparts with partially crystalline atomic structure. The degradation of five dyes were investigated in view of practical applications. The reaction conditions, such as catalyst dosage, PMS concentration, light intensity as well as salinity and natural organic matters, were fully studied. Quenching experiments were performed to qualitatively identify the generation of OH and SO 4 − . The mechanism of PMS activation by MGs was also proposed. This critical study sheds new insights into the catalytic mechanism for higher catalytic performance of amorphous catalysts compared with crystalline counterparts, providing an effective strategy to design catalysts for improving the overall catalytic activity. [ABSTRACT FROM AUTHOR]

Large-sized industrial grade Zr 55 Cu 30 Ni 5 Al 10 bulk metallic glass (BMG) was fabricated by a two-step arc-melting process and adding a trace of rare earth yttrium elements. A model to calculate critical cooling rate for forming BMG was established by considering the effect of pressure. Based on the model, the most important indicator, namely the critical size of forming BMG, for design and fabrication of BMG components by high pressure die casting (HPDC) is determined in consideration of different processing parameters, including the pressure and casting temperature. Theoretical calculation and numerical simulation indicated that increasing applied pressure during casting suppresses the nucleation of crystal nuclei but has little effect on the growth of nuclei at a deep supercooled temperature, thereby decreasing critical cooling rate and thus increase critical size. An increasing casting temperature would reduce critical size caused by more heat to dissipate. The critical size of the optimized Zr 55 Cu 30 Ni 5 Al 10 BMG cast by using steel mold is determined to be about 4–7 mm under different HPDC parameters. Our study reveals that the forming ability of HPDC is large enough for fabricating low cost Zr-based BMGs with suitable size for applications. [ABSTRACT FROM AUTHOR]

In this work, it is the first time to report that Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 metallic glass having unique atomic structure was employed for activation of persulfate under UV–Vis light. The investigation evaluated the importance of influencing parameters, including dye concentration, persulfate concentration, ribbon dosage and light intensity, on malachite green (MG) dye degradation. The results reveal that 100% dye color removal with a reaction rate of k = 0.0849 min − 1 could be achieved within 30 min under specific parameters control. In addition, surface decay behavior of the catalyst also plays a significant effect on the reusability and sustainability. The inclusion of Nb atom in Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 promotes enrichment of Si atom on the ribbon surface, causing the formation of Si and Nb oxides to further improve the surface stability on both of free and roller-contacted surfaces. The precipitations on reused ribbon surface are confirmed as α-Fe, iron oxide and Si, Nb oxides, revealing a high potential of catalytic reusability for wastewater treatment. The present work will open a new gate for further realizing the high performance of industrial water treatment using metallic glass. [ABSTRACT FROM AUTHOR]

Abstract: In this study, single line scans at different laser powers were carried out using selective laser meting (SLM) equipment on a pre-fabricated porous Al86Ni6Y4.5Co2La1.5 metallic glass (MG) preform. The densification, microstructural evolution, phase transformation and mechanical properties of the scan tracks were systematically investigated. It was found that the morphology of the scan track was influenced by the energy distribution of the laser beam and the heat transfer competition between convection and conduction in the melt pool. Due to the Gaussian distribution of laser energy and heat transfer process, different regions of the scan track experienced different thermal histories, resulting in a gradient microstructure and mechanical properties. Higher laser powers caused higher thermal stresses, which led to the formation of cracks; while low power reduced the strength of the laser track, also inducing cracking. The thermal fluctuation at high laser power produced an inhomogeneous chemical distribution which gave rise to severe crystallization of the MG, despite the high cooling rate. The crystallization occurred both within the heat affected zone (HAZ) and at the edge of melt pool. However, by choosing an appropriate laser power crack-free scan tracks could be produced with no crystallization. This work provides the necessary fundamental understanding that will lead to the fabrication of large-size, crack-free MG with high density, controllable microstructure and mechanical properties using SLM. [Copyright &y& Elsevier]

Highlights: [•] E corr of samples increases but E pit decreases with increasing S C. [•] Si distribution on corroded surfaces depends on the quick growth of iron oxides. [•] Thickness of oxidation film decreases with increasing S C. [•] Critical concentration is found at 0.6M in NaCl immersion experiments. [ABSTRACT FROM AUTHOR]

Abstract: The plastic deformation behavior and serrated flow in seven bulk metallic glass (BMG) systems were investigated through instrumented indentation. These materials include Ce65Al10Ni10Cu10Nb5, Mg65Cu25Gd10, Pd43Ni10Cu27P20, Cu60Zr20Hf10Ti10, Pt57.5Cu14.7Ni5.3P22.5, Ni60Nb37Sn3 and Fe43Cr16Mo16C15B10 BMGs, which show a glass transition temperature (T g) ranging from 360 to 908K at a heating rate of 0.33K/s. Remarkable difference in deformation behavior was found among these BMGs in the load–depth curves during nanoindentation. Prominent serrations are observed in Mg-, Pt- and Pd-based BMGs with medium T g during the loading process, whereas no distinct serrated flow was found in Ce-, Ni- and Fe-based BMGs with quite low or high T g. The subsurface plastic deformation regions after indentation were investigated using depth-sensing microindentation to characterize the shear band feature developed in various BMG systems. The size of the shear band upset is found to be larger in the alloys with lower T g. The effect of T g on the operation of shear bands and the serrated flow behavior in various BMG systems were discussed. [Copyright &y& Elsevier]

The effect of Nb element on the corrosion resistance of Fe-based metallic glasses in the alkaline environment has been investigated with various techniques like potentiodynamic polarization test, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and potentiostatic tests. With increasing the Nb content, the passivation stability of as spun Fe 87- x B 13 Nb x (x = 0, 7 and 10) glassy ribbons increases and the thickness of their passive film decreases according to XPS analysis. In the potentiostatic test, the ribbons have a transition potential E trans of −0.58, −0.47 and −0.38 V SCE with x = 0, 7 and 10 respectively, showing an increasing passivation stability with increasing x , which is more sensible than the potentiodynamic parameters like i pass and E pit. Meanwhile, Nb element has the ability to repair pitting holes. In potentiostatic test, the long constant potential treatment below E trans may enhance the generation of ribbon's passivation film, indicating that the potentiostatic test can tune the passivation behavior of metallic alloys. • With increasing the Nb content, the Fe0 and Nd0 XPS peaks rise. • In potentiostatic test, the ribbons have a transition potential E trans. • Nb element has the ability to repair pitting holes. • Potentiostatic test can indirectly reflect the passivation behavior of alloys. [ABSTRACT FROM AUTHOR]

Although metallic glasses (MGs) with unique disordered atomic structure have increasingly attracted great research interest as one of the most innovative heterogeneous catalysts in water remediation, few works focused on the synergistic role of different elemental constituents to well understand their superb catalytic performance. Herein, Co atoms were selected to partially substitute for the Fe elements in Fe-based MGs to study the corresponding synergistic catalytic function in dye degradation. Experimental results demonstrated that the Fe 36 Co 36 Si 4.8 B 19.2 Nb 4 MG with a kinetic rate constant of k = 0.06 min−1 degrades rhodamine B (RhB) dye 20 times faster than the Fe 73.5 Si 13.5 B 9 Cu 1 Nb 3 MGs with k = 0.003 min−1. Three types of dye including RhB, methylene blue (MB) and malachite green were investigated to draw attention to the broad, practical applications. Various chemical parameters, such as catalyst dosage, persulfate concentration, and dye concentration, were also studied. Quenching experiments indicated that the highly active hydroxyl (⋅OH) and sulfate (SO 4 ⋅−) radicals are largely produced from persulfate by the activation of the Fe 36 Co 36 Si 4.8 B 19.2 Nb 4 MG catalyst. This critical work uncovers a new paradigm to establish an effective approach for alloy design in widespread catalytic applications. Image 1 • Co atoms were selected to partially substitute for the Fe elements in Fe-based MGs. • Catalytic activity was greatly enhanced by synergistic function of iron and cobalt. • Increasing boron contents could promote dye degradation efficiency. • ⋅OH and SO 4 ⋅− were found to be the primary radicals for dye degradation. [ABSTRACT FROM AUTHOR]