Glass-metal Nanocomposites Research Articles

Evaluation of room temperature creep deformation of in situ Fe-based bulk metallic glass nanocomposites by instrumented indentation

In the present work, Fe57Cr9Mo5B16P7C6 (at. %) in situ bulk metallic glass nanocomposites of varying crystallinity, i.e. 0 to 80 vol. %, were synthesized by spark plasma sintering. Room temperature indentation creep behaviour of these composites was evaluated with nanoindentation technique. Effect of crystalline phase content on overall creep behaviour of the BMG composites was evaluated. Creep resistance of the BMG composites was improved with increase in the amount of crystalline phases up to 40 vol. %. Improved creep resistance is attributed to the presence of nanocrystalline phases in amorphous matrix and lower defect concentration in the BMG composite samples. However, excess crystallinity imparted brittleness and resulted in poor creep performance of the BMG composites. Derived stress exponent values are significantly lesser for the BMG composite sample in comparison to the amorphous compact indicating the transition in the mode of plastic deformation from inhomogeneous to nearly homogeneous. Loading rate has more pronounced influence on final creep displacement of fully amorphous sample in comparison to that of BMG composite.

In situ processing of Fe-based bulk metallic glass nanocomposites in supercooled liquid region by spark plasma sintering

Current study reports fabrication of in-situ Fe-based bulk metallic glass (BMG) nanocomposites by carrying out spark plasma sintering of Fe57Cr9Mo5B16P7C6 amorphous alloy powder. In situ BMG composites were synthesized with varying amount of crystalline phases by controlled partial devitrification in supercooled liquid region. Application of high consolidation pressure (400 MPa) during sintering contributed to enhanced viscous flow in the amorphous powder resulted in high densification (> 97 %) in the sintered compacts. Microstructural and phase evolution in the consolidated BMGs and BMG nanocomposites were systematically investigated with respect to sintering conditions. Microscale heterogeneity with respect to phase evolution in the sintered samples was evaluated by nanoindentation studies. Hardness of the sintered BMG nanocomposites was found to be significantly higher than the sintered BMGs ascribed to the evolution of hard intermetallic phases during devitrification.

Nanoheterogeneous ZrTa metallic glass thin films with high strength and toughness

This study investigated the mechanical behavior of ZrxTa1−x (x = 21–79 at%) thin films and nanolayered films of ZrTa with modulated composition as model systems to gain insight into the hardness and toughness of metallic glasses and metallic glass nanocomposites. The monolithic films exhibit two primary microstructures, namely, a fully amorphous form (Zr = 35–70at%.) and an amorphous-crystalline composite (21–30 at% Zr). The amorphous films show a monotonic hardness variation with composition over a wide range of 5.5 – 9 GPa. The partial crystallization of the films results in a further jump in hardness, as opposed to the general trend of softening upon crystallization. The emergence of the crystalline phase also improves the ductility of the films, as verified by nanoindentation-based fracture toughness measurements. The indentation pile-up exhibits several shear bands in the fully amorphous films, replaced by a featureless pile-up zone for the case of Zr25Ta75, further verifying the superior toughness of the composite. The second part of the analysis pursued obtaining a similar toughening through fully amorphous nanolayered films of Zr35Ta65 / Zr70Ta30. The results indicate that these films provide a balanced combination of high hardness and enhanced ductility, providing an alternative route to the development of tough metallic glass coatings. Data AvailabilityThe raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

Optical and dielectric properties of nanocomposites on base nanoporous glasses with silver and silver iodide nanowires

It is experimentally shown that the electrolysis of silver salt in silicate nanoporous glasses (NPGs) with interconnecting pores, having average sizes of 25 nm, makes possible to fabricate metal-glass nanocomposites. Silver component of nanocomposites consists of fractal microbranches, which, in turn, consist of silver nanowires. By iodizing silver nanowires can be transformed to AgI nanowires. Absorption and luminescence spectra of fabricated nanocomposites are presented. Dielectric spectra of “Ag nanowires-glass” nanocomposite were measured in temperature range of −50 … +250 OC for frequencies of 0.1–106 Hz. Dielectric measurements of “AgI nanowires -glass” nanocomposite have shown the presence of phase transition, typical for crystalline AgI.

Atomistic investigation of mechanical properties of metallic glass nanocomposites

In this paper, tensile deformation of metallic glass (MG) nanocomposites which consist of cellular MG matrix and columnar grains are studied by the molecular dynamic simulations. The size effects of the ligament thickness and the grain size on the yield strength and plasticity are elucidated. It is found that the ratio of the grain size to the ligament thickness (d/s) has a great influence on the plastic deformation. Two typical deformation mechanisms are further investigated. In the composite models with large d/s, grain boundaries motion and voids formation are the main mechanisms. When d/s decreases to 6, the grains can not only promote multiple shear bands formation but also impede the main shear band propagation. As a result, large plastic plateau appears in the stress–strain curve. These results are helpful to optimize the mechanical properties of MG composites.

A molecular dynamics study on the tensile characteristics of various metallic glass nanocomposites reinforced by Weyl semimetals three-dimensional graphene network

Carbon nanostructures as one of the efficient candidates have been employed to reinforce various types of nanocomposites. Accordingly, the current study employs the recently proposed three-dimensional graphene network, i.e. Hexagonal Graphene Network (HGN), Triangular Graphene Network (TGN) and Quadrilateral Graphene Network (QGN), as the reinforcements for highly applicable metallic glass (MG) nanocomposites with various compositions to study the tensile characteristics such as Young's modulus (YM), Ultimate Strength (Sut) and ultimate strain (US) using molecular dynamics (MD) simulations. Considering pure MGs, two-elements MG with higher Cu percentage demonstrate superior tensile behavior compared to other MGs. Moreover, the increase in the number of elements in MG composition slightly deteriorates tensile characteristics. It is observed that reinforcements considerably improve the tensile characteristics which are considerably pronounced for HGN reinforced MG nanocomposites (MGNCs). Further, it is demonstrated that US is more sensitive to the reinforcement of MGs compared to Young's modulus and ultimate strength. In addition, it is observed that the effect of MG types on the tensile characteristics becomes relatively insignificant in large deformations as C–C bond plays the dominant role to resist axial force in comparison with the weak vdW interaction between the elements of MG and the nanofiller. Further, necking is observed for two-elements MGs which indicate their more ductile behavior than other types. Finally, for the applications that correspond to big axial force, large and small deformations, Al-based three-elements, Ti–Ni based four-elements and Ti-based three-elements MGNCs with HGN reinforcement is proposed, respectively.

Strengthening and toughening mechanisms of metallic glass nanocomposites via graphene nanoplatelets

The lack of ductility, mainly due to shear localization, limits the full exploitation of metallic glasses (MGs). Such a weakness can be mitigated via introducing graphene nanoplatelets (GNs), which helps strengthen and toughen MG matrix. Using molecular dynamics simulations, we investigate the tensile deformation of Cu50Zr50 metallic glass-graphene nanoplatelet composites (MGGNCs) regarding the effects of graphene volume fraction and graphene layer number. Increasing fraction of GN in MGGNC enhances both tensile strength and fracture strain. The dominant component changes from MG matrix to GN, corresponding to a failure mode transition from shear banding in MG to brittle fracture in graphene. For a given volume fraction, single-layered GN behaves better than its double-layered counterpart, manifested as a higher fracture strain in MGGNCs. Our study illustrates the strengthening and toughening mechanisms in MGGNCs, and why single-layered GN performs better. All of these results can contribute to the synthesis of novel MG/graphene composites.

A comprehensive analysis of the mechanical properties and fracture analysis of metallic glass nanocomposites reinforced by carbon nanotubes and Cu nanowires: A molecular dynamics study

Reinforced by nanowires (NWs), carbon nanotubes (CNTs) and NW encapsulated CNT (NW@CNT), tensile behavior of various types of Cu-Zr based metallic glass (MG) nanocomposites are studied using molecular dynamics (MD) simulations. It is observed that pure two-toms alloy MG and the one reinforced with bigger CNT demonstrates higher tensile properties than other types of MGs. Further, it is observed that the ultimate strength of reinforced MGs with individual CNTs is slightly higher than that of NW@CNT reinforced analogous. In this case, it is noticed that reinforced three-atoms Cu-Zr MG nanocomposites including Ti atoms demonstrate the highest ultimate strength and strain.

Layer thickness effects on the strengthening and toughening mechanisms in metallic glass-graphene nanolaminates

Experiments have proved that one solution to improve the ductility of metallic glasses lies in introducing graphene and synthesizing metallic glass (MG) nanolaminates. In this work, molecular dynamic simulations are conducted to investigate layer thickness effects on the tensile behaviors of Cu50Zr50 metallic glass-graphene nanolaminates (MGGNLs). The increase in MG layer thickness leads to the decrease in the ultimate strength of MGGNL and helps to the development of shear bands. Meanwhile, plastic deformation mode transits from homogeneous flow to shear localization. The critical layer thickness related to such a transition can be predicted by the strain energy theory. Once the dissipated energy in MG matrix during shear bands formation exceeds the stored strain energy in graphene, shear localization dominates plastic deformation mode. Besides, fracture strain decreases with increasing MG layer thickness. There also exists a kink for the linear decline in fracture strain, corresponding to the plastic deformation transition. Finally, the equivalent model for layer thickness is proposed to better describe the Hall-Petch effect on the yield strength of MGGNLs. Our study provides the guidance to the synthesis of novel metallic glass nanocomposites.

Buckling behavior of various metallic glass nanocomposites reinforced by carbon nanotube and Cu nanowire: A molecular dynamics simulation study

The reinforcement of various materials by nanofillers as nanocomposites has recently received the attention of many researchers. In the present research, molecular dynamics simulations are used to investigate the influence of nanowire (NW)/carbon nanotube (CNT) reinforcement on the buckling behavior of metallic glass matrix nanocomposites (MGMNCs). The buckling characteristics of nanocomposites made by adding Cu NWs, CNTs and Cu NW-encapsulated CNTs to metallic glass matrices are studied. The results demonstrate that MG alloys comprising just two elements (Cu and Zr) with higher Cu percentage have higher mechanical stability. Also, it is observed that adding NW leads to a negative effect on the buckling behavior, while adding CNT and NW-encapsulated CNT considerably increases the buckling force and strain of the metallic glass models. Moreover, it is found that the filled CNT is the most effective nanofiller for amending the buckling behavior of metallic glasses. Furthermore, as the size of nanofillers gets larger, the critical force increases and the critical strain decreases.

Fluorescent clusters in chloride photo-thermo-refractive glass by femtosecond laser bleaching of Ag nanoparticles.

We report photoluminescence in bulk chloride photo-thermo-refractive glass under irradiation with femtosecond laser pulses. The fluorescence originates from the bleaching of silver nanoparticles precipitating in the glass. Similarly to the conventional process of the femtosecond re-shaping of metal inclusions with diameter tens of nanometers, irradiation of the smaller nanoparticles results in a fast shrinking size with an ellipsoidal shape via photofragmentation. Under UV excitation, remaining sub-nanometer silver molecular clusters show visible and near IR fluorescence, which increases with chlorine concentration. The observed bleaching of silver nanoparticles in bulk glass-metal nanocomposite can find applications in data storage and bleaching of volume Bragg gratings.

Mechanical characteristics of CNT-reinforced metallic glass nanocomposites by molecular dynamics simulations

Carbon nanotubes (CNTs) have been widely used to strengthen different types of materials including polymers, ceramics, and metals due to their extraordinarily high strength. In this work, we investigated the influence of CNTs on the mechanical characteristics of amorphous metallic glasses by using molecular dynamics simulations. We constructed long (continuous) and short (discontinuous) CNT-reinforced metallic glass nanocomposites, determined their stress–strain responses and elastic modulus, and compared their tensile and compressive behaviors with monolithic metallic glasses. It was found that long CNTs dramatically increased the stiffness and yield strength of the metallic glass, and improved their elastic region of deformation and ability to absorb energy. In contrast, metallic glasses reinforced with short CNTs showed almost no improvement of mechanical properties.

Correction: Corrigendum: Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser

We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as 3.5 at the laser fluence of 0.6 J/cm2. The developed approach can be employed to control the anisotropy of the glass-metal composites.

Effect of the size of nanoparticles on their dissolution within metal-glass nanocomposites under sustained irradiation

We investigate the dissolution law of metallic nanoparticles (NPs) under sustained irradiation. The system is composed of isolated spherical gold NPs (4–100 nm) embedded in an amorphous silica host matrix. Samples are irradiated at room temperature in the nuclear stopping power regime with 4 MeV Au ions for fluences up to 8 × 1016 cm−2. Experimentally, the dependence of the dissolution kinetics on the irradiation fluence is linear for large NPs (45–100 nm) and exponential for small NPs (4–25 nm). A lattice-based kinetic Monte Carlo (KMC) code, which includes atomic diffusion and ballistic displacement events, is used to simulate the dynamical competition between irradiation effects and thermal healing. The KMC simulations allow for a qualitative description of the NP dissolution in two main stages, in good agreement with the experiment. Moreover, the perfect correlation obtained between the evolution of the simulated flux of ejected atoms and the dissolution rate in two stages implies that there exists an effect of the size of NPs on their dissolution and a critical size for the transition between the two stages. The Frost-Russell model providing an analytical solution for the dissolution rate, accounts well for the first dissolution stage but fails in reproducing the data for the second stage. An improved model obtained by including a size-dependent recoil generation rate permits fully describing the dissolution for any NP size. This proves, in particular, that the size effect on the generation rate is the principal reason for the existence of two regimes. Finally, our results also demonstrate that it is justified to use a unidirectional approximation to describe the dissolution of the NP under irradiation, because the solute concentration is particularly low in metal-glass nanocomposites.

Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser.

We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as 3.5 at the laser fluence of 0.6 J/cm2. The developed approach can be employed to control the anisotropy of the glass-metal composites.

Processing and Characterization of In-Situ Generated Nanosilver and Er3+ Co-Doped Bromoborosilicate Glass Nanocomposites.

In the present investigation, bromoborosilicate glass of composition 6Na2O-19K2O-10BaBr2- 2Al2O3-15B2O3-48SiO2 (mole %) added with 0.2 wt% SnO, co-doped with 0.001 wt% Ag and 0.7 wt% Er2O3 in excess amount, was prepared by melt-quench technique. The metal-glass nanocomposites were derived involving a single-step in-situ thermochemical reduction of the precursor glass subjecting an isothermal heat-treatment protocol. The precursor glass and metal glass nanocomposites were characterized by dilatometer, differential scanning calorimeter, X-ray diffractometer, field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectrometer, UV-Vis-NIR spectrophotometer, fluorimeter etc. XRD spectra represent the amorphous nature of the samples and without having any sharp peaks of silver (Ag0) and barium bromide (BaBr2). But the FESEM micrograph shows the presence of BaBr2 crystallites in clusters and the TEM micrograph shows the presence of AgO nanoparticles of different shapes and sizes. The precursor glass sample shows sharp absorption peak at 378 nm and 521 nm due to the 4G11,2 and 2H11/2 energy levels of Er3+ but glass nanocomposites exhibit another band at 410 nm due to the surface plasmon resonance of Ag0 nanoparticles. They also show sharp emis- sion peak at 1542 nm due to 4115/2 -+4l13/2 transition of Er3+ ions and prominent upconverted peaks at 630 nm (red, medium) and 645 nm (red, strong) due to 4F9/2 + 1 15/2 transition. The intensity of the absorption and upconverted peaks increases with the duration of heat treatment, having maximum intensity at 5 h and the intensity of the emission peak increases with heat treatment upto 1 h and then decreases for 5 h. Thus these metal-glass nanocomposites show enhanced photoluminescence upconversion and are promising material for different photonic applications.

Radially and azimuthally polarized laser induced shape transformation of embedded metallic nanoparticles in glass.

Radially and azimuthally polarized picosecond (~10 ps) pulsed laser irradiation at 532 nm wavelength led to the permanent reshaping of spherical silver nanoparticles (~30 - 40 nm in diameter) embedded in a thin layer of soda-lime glass. The observed peculiar shape modifications consist of a number of different orientations of nano-ellipsoids in the cross-section of each written line by laser. A Second Harmonic Generation cross-sectional scan method from silver nanoparticles in transmission geometry was adopted for characterization of the samples after laser modification. The presented approach may lead to sophisticated marking of information in metal-glass nanocomposites.

On the evolution of the steady state in gold-silica nanocomposites under sustained irradiation

We investigate the kinetic evolution of a nanocomposite submitted to sustained irradiation. The study focuses on gold nanoparticles embedded within a silica host matrix. Irradiations with 4 MeV Au ++ ions are performed in the temperature range from 300 K to 1100 K and for fluences up to 8 × 1016 cm−2. The experimental results are combined with kinetic Monte Carlo simulations to fully characterize the kinetic evolution of the nanoparticles under irradiation. In particular, the change of the steady state with the temperature is investigated in details. First, we demonstrate the existence of a direct-coarsening regime at high temperature, e.g., above 900 K, and of a coarsening-resistant regime at low temperature, e.g., below 700 K. Second, we show that the transition between these two regimes takes place in a temperature region, where the nucleation of new nanoparticles is hindered, and the mass is redistributed among the existing nanoparticles. We also use our experimental results to critically analyze the existing theoretical models. As it has recently been pointed out that the physical principles underlying precipitation under irradiation are similar to those that govern the behavior of driven alloys, this work can be considered as an attempt to bridge the gap between two fields of experimental and theoretical studies, viz., those on driven alloys and those on metal-glass nanocomposites submitted to a sustained irradiation.

Deformation induced alloying in crystalline – metallic glass nano-composites

We study the mechanisms of deformation driven chemical mixing in a metallic nanocomposite model system. More specific, we investigate shear banding at the atomic scale in an amorphous CuZr/ crystalline Cu nanolaminate, deformed by microindentation. Three CuZr/Cu multilayer systems (100nm Cu/100nm CuZr, 50nm Cu/100nm CuZr, and 10nm Cu/100nm CuZr) are fabricated to study the effect of layer thickness on shear band formation and deformation induced alloying. The chemical and structural evolution at different strain levels are traced by atom probe tomography and transmission electron microscopy combined with nano-beam diffraction mapping. The initially pure crystalline Cu and amorphous CuZr layers chemically mix by cross-phase shear banding after reaching a critical layer thickness. The Cu inside the shear bands develops a high dislocation density and can locally undergo transition to an amorphous state when sheared and mixed. We conclude that the severe deformation in the shear bands in the amorphous layer squeeze Zr atoms into the Cu dislocation cores in the Cu layers (thickness <5nm), resulting in local chemical mixing.

Self-arrangement of periodic layers of silver nanoparticles in silicate glass

We studied the influence of hydrogen-reducible metal ions concentration profile under the surface of ion exchanged glass on the behavior of the layered glass-metal nanocomposite which can be formed via self-arranging in the course of thermal processing of the glass in hydrogen atmosphere. The modeling shows that depending of the ascending or descending type of the concentration profile the layered nanocomposite with decreasing or increasing gaps between the layers of nanoparticles can be formed. In certain cases the mean radius and the particle size-distribution function may be the same among the subsequent layers. A proper choice of the ascending concentration profile can provide practically equidistant layers of the nanocomposite applicable for photonic crystals and Bragg gratings.