On the thermodynamics of plasticity during quasi-isentropic compression of metallic glass

Entropy production in quasi-isentropic compression (QIC) is critically important for understanding the properties of materials under extremeconditions. However, the origin and accurate quantification of entropy in this situation remain long-standing challenges. In this work, a framework is established for the quantification of entropy production and partition, and their relation to microstructural change in QIC. Cu50Zr50is taken as a model material, and its compression is simulated by molecular dynamics. On the basis of atomistic simulation-informed physicalproperties and free energy, the thermodynamic path is recovered, and the entropy production and its relation to microstructural change aresuccessfully quantified by the proposed framework. Contrary to intuition, entropy production during QIC of metallic glasses is relativelyinsensitive to the strain rate ˙γ when ˙γ ranges from 7.5 × 10^(8) to 2 × 10^(9)/s, which are values reachable in QIC experiments, with a magnitudeof the order of 10^(−2)kB/atom per GPa. However, when ˙γ is extremely high (>2 × 10^(9)/s), a notable increase in entropy production rate with˙γ is observed. The Taylor–Quinney factor is found to vary with strain but not with strain rate in the simulated regime. It is demonstrated thatentropy production is dominated by the configurational part, compared with the vibrational part. In the rate-insensitive regime, the increase inconfigurational entropy exhibits a linear relation to the Shannon-entropic quantification of microstructural change, and a stretched exponential relation to the Taylor–Quinney factor. The quantification of entropy is expected to provide thermodynamic insights into the fundamentalrelation between microstructure evolution and plastic dissipation.

Corrosion and in vitro cytocompatibility investigation on the designed Mg-Zn-Ag metallic glasses for biomedical application

In the present work,seven Mg-Zn-Ag alloys with the nominal composition of Mg_(96-x)Zn_(x)Ag_(4)(x=17,20,23,26,29,32,35 in at.%)were prepared by induction melting and single-roller melt-spinning.The X-ray diffraction(XRD)analyses indicate the metallic glasses with three composition of Mg_(73)Zn_(23)Ag_(4),Mg_(70)Zn_(26)Ag_(4),and Mg_(67)Zn_(29)Ag_(4)were obtained successfully.The differential scanning calorimetry(DSC)measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis.The maximum glass transition temperature(Trg)was found to be 0.525 with a composition close to Mg_(67)Zn_(29)Ag_(4),which results in the best glass-forming ability.Moreover,the immersion test in simulated body fluid(SBF)demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses.The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content.The sample Mg_(67)Zn_(29)Ag_(4)has the lowest corrosion rate of 0.19mm/yr,which could meet the clinical application requirement well.The in vitro cell experiments show that the Madin-Darby canine kidney(MDCK)cells cultured in sample Mg_(67)Zn_(29)Ag_(4)and its extraction medium have higher activity.However,the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma(RD)tumor cells.The present investigations on the glass-forming ability,corrosion behavior,cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.

Ultrasensitive Mechanical Sensor Using Tunable Ordered Array of Metallic and Insulating States in Vanadium Dioxide

Detecting tiny deformations or vibrations, particularly those associated with strains below 1%, is essential in various technological applications. Traditional intrinsic materials, including metals and semiconductors, face challenges in simultaneously achieving initial metallic state and strain-induced insulating state, hindering the development of highly sensitive mechanical sensors. Here we report an ultrasensitive mechanical sensor based on a strain-induced tunable ordered array of metallic and insulating states in the single-crystal bronze-phase vanadium dioxide [VO_(2)(B)] quantum material. It is shown that the initial metallic state in the VO_(2)(B) flake can be tuned to the insulating state by applying a weak uniaxial tensile strain. Such a unique property gives rise to a record-high gauge factor of above 607970, surpassing previous values by an order of magnitude, with excellent linearity and mechanical resilience as well as durability. As a proof-of-concept application, we use our proposed mechanical sensor to demonstrate precise sensing of the micro piece, gentle airflows and water droplets. We attribute the superior performance of the sensor to the strain-induced continuous metal-insulator transition in the single-crystal VO_(2)(B) flake, evidenced by experimental and simulation results. Our findings highlight the potential of exploiting correlated quantum materials for next-generation ultrasensitive flexible mechanical sensors, addressing critical limitations in traditional materials.

Distinct vibrational signatures and complex phase behavior in metallic oxygen

Evidence for metallization in dense oxygen has been reported for over 30 years[Desgreniers et al.,J.Phys.Chem.94,1117(1990)]at a now routinely accessible 95 GPa[Shimizu et al.,Nature 393,767(1998)].However,despite the longevity of this result and the technological advances since,the nature of the metallic phase remains poorly constrained[Akahama et al.,Phys.Rev.Lett.74,4690(1995);Goncharov et al.,Phys.Rev.B 68,224108(2003);Ma,Phys.Rev.B 76,064101(2007);and Weck et al.,Phys.Rev.Lett.102,255503(2009)].In this work,through Raman spectroscopy,we report the distinct vibrational characteristics of metallicζ-O_(2) from 85 to 225 GPa.In comparison with numerical simulations,wefind reasonable agreement with the candidate structure up to about 150 GPa.At higher pressures,the C2/mstructure is found to be unstable and incompatible with experimental observations.Alternative candidate structures,and Ci,with C2/m C2/conly two molecules in the primitive unit cell,are found to be stable and more compatible with measurements above 175 GPa,indicative of the dissociation of(O_(2))4 units.Further,we report and discuss a strong hysteresis and metastability with the precursory phaseϵ-O_(2).Thesefindings will reinvigorate experimental and theoretical work into the dense oxygen system,which will have importance for oxygen-bearing chemistry,prevalent in the deep Earth,as well as fundamental physics.

Structural color of metallic glass through picosecond laser

The alteration in surface color of metallic glasses(MGs)holds great significance in the context of microstructuredesign and commercial utility.It is essential to accurately describe the structures that are formed during the laser and colorseparation processes in order to develop practical laser coloring applications.Due to the high oxidation sensitivity of Labasedmetallic glass,it can broaden the color range but make it more complex.Structure coloring by laser processing on thesurface of La-based metallic glass can be conducted after thermoplastic forming.It is particularly important to clarify therole of structure and composition in the surface coloring process.The aim is to study the relationship between amorphoussurface structural color,surface geometry,and oxide formation by laser processing in metallic glasses.The findings revealedthat the periodic structure primarily determines the surface color at laser energy densities below 1.0 J/mm^(2).In contrast,thesurface color predominantly depends on the proportion of oxides that are formed when energy densities exceed 1.0 J/mm^(2).Consequently,this study provides a novel concept for the fundamental investigation of laser coloring and establishes a newavenue for practical application.

“Glass-quake”in elastically loaded bulk metallic glasses

Amorphous solids exhibit scale-free avalanches,even under small external loading,and thus can work as suitable systems to study critical behavior and universality classes.The abundance of scale-free avalanches in the entire elastic tension regime of bulk metallic glass(BMG)samples has been experimentally observed using acoustic emission(AE)measurements.In this work,we compare the statistics of avalanches with those of earthquakes,and find that they both follow the Gutenberg–Richter law in the statistics of energies and Omori’s law of aftershock rates,and share the same characteristics in the distribution of recurrence times.These resemblances encourage us to propose the term“glass-quake”to describe avalanches in elastically loaded BMGs.Furthermore,our work echoes the potential universality of critical behavior in disordered physical systems from atomic to planetary scales,and motivates the use of elastic loaded BMGs as valuable laboratory simulators of seismic dynamics.

An effective strategy of constructing multi-metallic oxides of ZnO/ CoNiO_(2)/CoO/C microflowers for improved supercapacitive performance

In this work,a new ZnO/CoNiO_(2)/CoO/C metal oxides composite is prepared by cost-effective hydrothermal method coupled with annealing process under N_(2) atmosphere.Notably,the oxidation-defect annealing environment is conducive to both morphology and component of the composite,which flower-like ZnO/CoNiO_(2)/CoO/C is obtained.Benefited from good chemical stability of ZnO,high energy capacity of CoNiO_(2) and CoO and good conductivity of C,the as-prepared sample shows promising electrochemical behavior,including the specific capacity of 1435 C·g^(-1) at 1 A·g^(-1),capacity retention of 87.3%at 20 A·g^(-1),and cycling stability of 90.5%for 3000 cycles at 5 A·g^(-1),respectively.Furthermore,the prepared ZnO/CoNiO_(2)/CoO/C/NF//AC aqueous hybrid supercapacitors device delivers the best specific energy of 55.9 W·h·kg^(-1) at 850 W·kg^(-1).The results reflect that the as-prepared ZnO/CoNiO_(2)/CoO/C microflowers are considered as high performance electrode materials for supercapacitor,and the strategy mentioned in this paper is benefit to prepare mixed metal oxides composite for energy conversion and storage.

Theoretical characterization of the temperature-dependent saturation magnetization of magnetic metallic materials

Based on the force-heat equivalence energy density principle,a theoretical model for magnetic metallic materials is developed,which characterizes the temperature-dependent magnetic anisotropy energy by considering the equivalent relationship between magnetic anisotropy energy and heat energy;then the relationship between the magnetic anisotropy constant and saturation magnetization is considered.Finally,we formulate a temperature-dependent model for saturation magnetization,revealing the inherent relationship between temperature and saturation magnetization.Our model predicts the saturation magnetization for nine different magnetic metallic materials at different temperatures,exhibiting satisfactory agreement with experimental data.Additionally,the experimental data used as reference points are at or near room temperature.Compared to other phenomenological theoretical models,this model is considerably more accessible than the data required at 0 K.The index included in our model is set to a constant value,which is equal to 10/3 for materials other than Fe,Co,and Ni.For transition metals(Fe,Co,and Ni in this paper),the index is 6 in the range of 0 K to 0.65T_(cr)(T_(cr) is the critical temperature),and 3 in the range of 0.65T_(cr) to T_(cr),unlike other models where the adjustable parameters vary according to each material.In addition,our model provides a new way to design and evaluate magnetic metallic materials with superior magnetic properties over a wide range of temperatures.

Effect of overheating-induced minor addition on Zr-based metallic glasses

Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin responsible for the variation of properties remains poorly understood.In the present work,we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins.Specifically,we quenched the melt at different temperatures ranging from 1.1Tl to 1.5Tl(Tl is the liquidus temperature)to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating.We found that glass transition temperature,Tg,increases by as much as 36 K,and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5Tl.The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys.The incorporated oxygen and silicon can both enhance the interactions between atoms,which renders the cooperative rearrangements of atoms difficult,and thus enhances the kinetic stability of the MGs.

Three-dimensional porous bimetallic metal–organic framework/gelatin aerogels: A readily recyclable peroxymonosulfate activator for efficient and continuous organic dye removal

As promising catalysts for the degradation of organic pollutants,metal–organic frameworks(MOFs)often face limitations due to the particle agglomeration and challenging recovery in liquid-catalysis application,stemming from their powdery nature.Engineering macroscopic structures from pulverous MOF is thus of great importance for broadening their practical applications.In this study,three-dimensional porous MOF aerogel catalysts were successfully fabricated for degrading organic dyes by activating peroxymonosulfate(PMS).MOF/gelatin aerogel(MOF/GA)catalysts were prepared by directly integrating bimetallic FeCo-BDC with gelatin solutions,followed by freeze-drying and low-temperature calcination.The FeCo-BDC-0.15/GA/PMS system exhibited remarkable performance in degrading various organic dyes,eliminating 99.2%of rhodamine B within a mere 5 min.Compared to the GA/PMS system,there was over a 300-fold increase in the reaction rate constant.Remarkably,high removal efficiency was maintained across varying conditions,including different solution pH,co-existing inorganic anions,and natural water matrices.Radical trapping experiments and electron paramagnetic resonance analysis revealed that the degradation involved radical(SO_(4)^(-)·)and non-radical routes(^(1)O_(2)),of which ^(1)O_(2) was dominant.Furthermore,even after a continuous 400-min reaction in a fixed-bed reactor at a liquid hourly space velocity of 27 h^(-1),the FeCo-BDC/GA composite sustained a degradation efficiency exceeding 98.7%.This work presents highly active MOF-gelatin aerogels for dye degradation and expands the potential for their large-scale,continuous treatment application in organic dye wastewater management.

Unveiling the early stage evolution of local atomic structures in the crystallization process of a metallic glass

The early stage evolution of local atomic structures in a multicomponent metallic glass during its crystallization process has been investigated via molecular dynamics simulation.It is found that the initial thermal stability and earliest stage evolution of the local atomic clusters show no strong correlation with their initial short-range orders,and this leads to an observation of a novel symmetry convergence phenomenon,which can be understood as an atomic structure manifestation of the ergodicity.Furthermore,in our system we have quantitatively proved that the crucial factor for the thermal stability against crystallization exhibited by the metallic glass is not the total amount of icosahedral clusters,but the degree of global connectivity among them.

Synthesis and Coloring Mechanism of Metallic Glaze in R_(2)O-RO-Al_(2)O_(3)-SiO_(2)-P_(2)O_(5)System

A copper-red and silver-white metallic glaze of R_(2)O-RO-Al_(2)O_(3)-SiO_(2)-P_(2)O_(5)system was synthesized by adjusting the firing temperature and glaze components.The coloration mechanism of the metallic glaze was revealed via investigation of the microstructure of the glaze.Our research reveals that the metallic glaze with different colors is mainly due to the amount of Fe_(2)O_(3).The metallic glaze shows a silver-white luster due to a structural color ofα-Fe_(2)O_(3)crystals with a good orientation when the sample contains 0.0939 mol of Fe_(2)O_(3),maintaining temperatures at 1150℃for 0.5 h.The metallic glaze is copper-red which is dominated by the coupling of chemical and structural color ofα-Fe_(2)O_(3)crystals when the sample contains 0.0783 mol of Fe_(2)O_(3).After testing the amount of SiO_(2),we find that 4.0499 mol is the optimal amount to form the ceramic network,and 0.27 mol AlPO_(4)is the best amount to promote phase separation.

Suppressing dendritic metallic Li formation on graphite anode under battery fast charging

Lithium-ion batteries(LIBs)with fast-charging capability are essential for enhancing consumer experience and accelerating the global market adoption of electric vehicles.However,achieving fast-charging capability without compromising energy density,cycling lifespan,and safety of LIBs remains a significant challenge due to the formation of dendritic Li metal on graphite anode under fast charging condition.In view of this,the fundamentals for the dendritic metallic Li formation and the strategies for suppressing metallic Li plating based on analyzing the entire Li^(+)transport pathway at the anode including electrolyte,pore structure of electrode,and surface and bulk of materials are summarized and discussed in this review.Besides,we highlight the importance of designing thick electrodes with fast Li^(+)transport kinetics and comprehensively understanding the interaction between solid electrolyte interphase(SEI)and Li^(+)migration in order to avoid the formation of dendritic Li metal in practical fast-charging batteries.Finally,the regulation of Li metal plating with plane morphology,instead of dendritic structure,on the surface of graphite electrode under fast-charging condition is analyzed as a future direction to achieve higher energy density of batteries without safety concerns.

The occurrence of metallic copper and redistribution of copper in the shocked Suizhou L6 chondrite

Copper possesses very strong chacophile properties,but under the conditions found in meteorites,its behavior is like that of siderophile elements.The Suizhou meteorite is a highly shocked L6 chondrite.Troilite and taenite are considered the main primary carrier of copper in this meteorite,and the post-shock thermal episode is considered the main reason that elemental Cu migrates from its original host phase and forms metallic grains.The Suizhou meteorite contains a few very thin shock melt veins.The occurrence and behavior of metallic copper in this meteorite were studied by optical microscopic examination,electron microprobe analyses,and high-resolution X-ray elemental intensity mapping.Our results show that metallic copper is abundant in the Suizhou chondritic rock.Metallic copper grains adjacent to small troilite grains inside FeNi metal are the most common occurrence,and those at the FeNi metal–troilite interface are the second most common case.The metallic copper grains occurring at the interface of FeNi metal/troililte and silicate are rather rare.Metallic copper grains are not observed within the Suizhou shock veins,Instead,Cu in elemental form is transferred through shock metamorphism into FeNi metal+troilite intergrowths.Four diff erent occurrence types of Cu in the FeNi metal+troilite intergrowths have been identifi ed:the concentrations of Cu in the FeNi+FeS intergrowths for four occurrence types are rather close,we estimate it might be lower than 1 wt%.

Effect of high-energy Ne ions irradiation on mechanical properties difference between Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5)metallic glass and crystalline W

In this paper,high-energy Ne ions were used to irradiate Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) metallic glass(MG)and crystalline W to investigate their difference in mechanical response after irradiation.The results showed that with the irradiation dose increased,the tensile micro-strain increased,nano-hardness increased from 7.11 GPa to 7.90 GPa and 8.62 GPa,Young’s modulus increased,and H3/E2 increased which indicating that the plastic deformability decreased in crystalline W.Under the same irradiation conditions,the Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG still maintained the amorphous structure and became more disordered despite the longer range and stronger displacement damage of Ne ions in Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG than in crystalline W.Unlike the irradiation hardening and embrittlement behavior of crystalline W,Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG showed the gradual decrease in hardness from 6.02 GPa to 5.89 GPa and 5.50 GPa,the decrease in modulus and the increase in plastic deformability with the increasing dose.Possibly,the irradiation softening and toughening phenomenon of Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG could provide new ideas for the design of nuclear materials.

Impact response and energy absorption of metallic buffer with entangled wire mesh damper

An innovative metallic buffer consisting of series-connected hat-shaped entangled wire mesh damper(EWMD)and parallel springs are proposed in this work to enhance the reliability of engineering equipment.The impact response and the energy dissipation mechanism of hat-shaped EWMD under different quasi-static compression deformations(2-7 mm)and impact heights(100-200 mm)are investigated using experimental and numerical methods.The results demonstrate distinct stages in the quasi-static mechanical characteristics of hat-shaped EWMD,including stiffness softening,negative stiffness,and stiffness hardening.The loss factor gradually increases with increasing compression deformation before entering the stiffness hardening stage.Under impact loads,the hat-shaped EWMD exhibits optimal impact energy absorption when it enters the negative stiffness stage(150 mm),resulting in the best impact isolation effect of metallic buffer.However,the impact energy absorption significantly decreases when hat-shaped EWMD enters the stiffness hardening stage.Interestingly,quasi-static compression analysis after experiencing different impact loads reveals the disappearance of the negative stiffness phenomenon.Moreover,with increasing impact loads,the stiffness hardening point progressively shifts to an earlier stage.

Elliptical vibration chiseling:a novel process for texturing ultra-high-aspect-ratio microstructures on the metallic surface

High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications,such as high-performance heat transfer enhancement and surface plasmon devices.However,the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques.This study proposes a novel cutting-based process,namely elliptical vibration chiseling(EV-chiseling),for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio.Unlike conventional cutting,EV-chiseling superimposes a microscale EV on a backward-moving tool.The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation.Thanks to the tool’s backward movement,the chip is left on the material surface to form a microstructure rather than falling off.Since one microstructure is generated in one vibration cycle,the process can be highly efficient using ultrafast(>1 kHz)tool vibration.A finite element analysis model is established to explore the process mechanics of EV-chiseling.Next,a mechanistic model of the microstructured surface generation is developed to describe the microstructures’aspect ratio dependency on the process parameters.Then,surface texturing tests are performed on copper to verify the efficacy of EV-chiseling.Uniformed micro ribs with a spacing of 1–10μm and an aspect ratio of 2–5 have been successfully textured on copper.Compared with the conventional EV-cutting that uses a forward-moving tool,EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times.The experimental results also verify the accuracy of the developed surface generation model of microstructures.Finally,the effects of elliptical trajectory,depth of cut,tool shape,and tool edge radius on the surface generation of micro ribs have been discussed.

Universal basis underlying temperature, pressure and size induced dynamical evolution in metallic glass-forming liquids

The dramatic temperature-dependence of liquids dynamics has attracted considerable scientific interests and efforts in the past decades, but the physics of which remains elusive. In addition to temperature, some other parameters, such as pressure, loading and size, can also tune the liquid dynamics and induce glass transition, which makes the situation more complicated. Here, we performed molecular dynamics simulations for Ni_(50)Zr_(50) bulk liquid and nanodroplet to study the dynamics evolution in the complex multivariate phase space, especially along the isotherm with the change of pressure or droplet size. It is found that the short-time Debye–Waller factor universally determines the long-time relaxation dynamics no matter how the temperature, pressure or size changes. The basic correlation even holds at the local atomic scale. This finding provides general understanding of the microscopic mechanism of dynamic arrest and dynamic heterogeneity.

Magnetic and magnetocaloric effect of Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass

Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass exhibited excellent magnetic refrigeration material with a wide temperature range and high refrigeration capacity(RC)was reported.Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass was observed with typical spin glass behavior around 15.5 K.In addition,we find that the magnetic entropy change(-△S_(M))originates from the sample undergoing a ferromagnetic(FM)to paramagnetic(PM)transition around 20 K.Under a field change from 0 T to 7 T,the value of maximum magnetic entropy change(-△S_(M)^(max))reaches 12.5 J/kg·K,and the corresponding value of RC reaches 487.7 J/kg in the temperature range from 6 K to 60 K.The large RC and wide temperature range make the Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass be a promising material for application in magnetic refrigerators.

Failure pattern in ceramic metallic target under ballistic impact

The ballistic resistance and failure pattern of a bi-layer alumina 99.5%-aluminium alloy 1100-H12 target against steel 4340 ogival nosed projectile has been explored in the present experimental cum numerical study.In the experimental investigation,damage induced in the ceramic layer has been quantified in terms of number of cracks developed and failure zone dimensions.The resultant damage in the backing layer has been studied with variation in the bulge and perforation hole in the backing layer with the varying incidence velocity.The discussion of the experimental results has been further followed by three dimensional finite element computations using ABAQUS/Explicit finite code to investigate the behaviour of different types of bi-layer targets under multi-hit projectile impact.The JH-2 constitutive model has been used to reproduce the behaviour of alumina 99.5%and JC constitutive model has been used for steel 4340 and aluminium alloy 1100-H12.The total energy dissipation has been noted to be of lesser magnitude in case of sub-sequential impact in comparison to simultaneous impact of two projectiles.The distance between the impact points of two projectiles also effected the ballistic resistance of bi-layer target.The ballistic resistance of single tile ceramic front layer and four tile ceramic of equivalent area found to be dependent upon the boundary conditions provided to the target.