Glass State Research Articles

Structural rejuvenation and relaxation of a metallic glass under the periodically thermal-mechanical loading

The current work focuses on effect of the thermomechanical protocol which can lead either to aging or rejuvenation of glass through decoupling of the thermal and mechanical processes. We demonstrated that the La-based metallic glass shows a kind of material hypomnesia because a clearer rejuvenation trend is observed just after imposing strain oscillations of increasing amplitude than after a long period from that, as it is proved by the results of stress relaxation. There is a threshold value of the oscillation amplitude that separates the effect of the protocol between acceleration of aging and rejuvenation. The activated energy spectrums imply plasticity and mechanical heterogeneity of the metallic glass promoted by simple mechanical stimulation. Mechanical perturbations applied not long ago in time are vital for hypomnesia metallic glasses, in which different histories lead to various degrees of aging or rejuvenation. The correlation between the thermomechanical properties of metallic glasses and the previous application of strain oscillations of various amplitude is unveiled in this work, revealing an effective tool for regulating the structural state of metallic glasses through an easy-operated method.

Effect of anisotropic deformation on the differential scanning calorimetry response of polymer glasses

AbstractLarge anisotropic deformation affects the physical state of a polymer glass, where the changes in the state of material are revealed by performing a differential scanning calorimetry (DSC) experiment. Previously, the deformation was applied to polymers well below their glass transition temperatures, and it was found that uniaxial compressive loading–unloading resulted in a broad exothermic peak on the DSC trace. Here we report on the effect on the subsequent DSC response of a deformation experiment performed in uniaxial extension on a ductile 50:50 co‐polymer poly(BMA‐co‐MMA) (PBMA/MMA). The deformation of up to 80% strain was applied at Tg − 30°C and Tg − 40°C, that is, closer to Tg than in the previous work. Unlike in the well below Tg deformation case, the DSC trace contains an endothermic peak followed by an exothermic peak. The magnitude of the endothermic peak as well as the asymptotic glassy heat capacity increase with the amount of mechanical work performed during the deformation cycle.

Prediction of Van Hove singularity systems in ternary borides

A computational search for stable structures among both α and β phases of ternary ATB4 borides (A = Mg, Ca, Sr, Ba, Al, Ga, and Zn, T is 3d or 4d transition elements) has been performed. We found that α-ATB4 compounds with A = Mg, Ca, Al, and T = V, Cr, Mn, Fe, Ni, and Co form a family of structurally stable or almost stable materials. These systems are metallic in non-magnetic states and characterized by the formation of the localized molecular-like state of 3d transition metal atom dimers, which leads to the appearance of numerous Van Hove singularities in the electronic spectrum. The closeness of such singularities to the Fermi level can be easily tuned by electron doping. For the atoms in the middle of the 3d row (Cr, Mn, and Fe), these singularities led to magnetic instabilities and magnetic ground states with a weakly metallic or semiconducting nature. Such states appear as non-trivial coexistence of the different spin ladders formed by magnetic dimers of 3d elements. These magnetic states can be characterized as an analog of the spin glass state. Experimental attempts to produce MgFeB4 and associated challenges are discussed, and promising directions for further synthetic studies are formulated.

Transient replica symmetry breaking in Brillouin random fiber lasers

Replica symmetry breaking (RSB), as a featured phase transition between paramagnetic and spin glass state in magnetic systems, has been predicted and validated among random laser-based complex systems, which involves numerous random modes interplayed via gain competition and exhibits disorder-induced frustration for glass behavior. However, the dynamics of RSB phase transition involving micro-state evolution of a photonic complex system have never been well investigated. Here, we report experimental evidence of transient RSB in a Brillouin random fiber laser (BRFL)-based photonic system through high-resolution unveiling of random laser mode landscape based on heterodyne technique. Thanks to the prolonged lifetime of activated random modes in BRFLs, an elaborated mapping of time-dependent statistics of the Parisi overlap parameter in both time and frequency domains was timely resolved, attributing to a compelling analogy between the transient RSB dynamics and the random mode evolution. These findings highlight that BRFL-based systems with the flexible harness of a customized photonic complex platform allow a superb opportunity for time-resolved transient RSB observation, opening new avenues in exploring fundamentals and application of complex systems and nonlinear phenomena.

Efficient Synthesis of Highly Crystalline One-Dimensional CrCl3 Atomic Chains with a Spin Glass State.

One-dimensional (1D) magnetic material systems have attracted widespread interest from researchers because of their peculiar physical properties and potential applications in spintronics devices. However, the synthesis of 1D magnetic atomic chains has seldom been investigated. Here, we developed an iodine-assisted vacuum chemical vapor-phase transport (I-VCVT) method, utilizing single-walled carbon nanotubes (SWCNTs) with 1D cavities as templates, and high-quality and high-efficiency fabrication of 1D atomic chains of CrCl3 was achieved. Furthermore, the structure of CrCl3 atomic chains in the confined space of SWCNTs was analyzed in detail, and the charge transfer between the 1D atomic chains and SWCNTs was investigated through spectroscopic characterization. A comprehensive study of the dynamic magnetic properties revealed the existence of spin glass states and freezing of the 1D CrCl3 atomic chains at around 3 K, which has never been seen in bulk CrCl3. Our work established an effective strategy for the control synthesis of 1D magnetic atomic chains with promising potential applications in further magnetic-based spintronics devices.

Studies on the structure and the magnetic properties of high-entropy spinel oxide (MgMnFeCoNi)Al2O4

The study of high-entropy materials has attracted enormous interest since they could show new functional properties that are not observed in their related parent phases. Here, we report single crystal growth, structure, thermal transport, and magnetic property studies on a novel high-entropy oxide with the spinel structure (MgMnFeCoNi)Al2O4. We have successfully grown high-quality single crystals of this high-entropy oxide using the optical floating zone growth technique for the first time. The sample was confirmed to be a phase pure high-entropy oxide using x-ray diffraction and energy-dispersive spectroscopy. Through magnetization measurements, we found (MgMnFeCoNi)Al2O4 exhibits a cluster spin glass state, though the parent phases show either antiferromagnetic ordering or spin glass states. Furthermore, we also found that (MgMnFeCoNi)Al2O4 has much greater thermal expansion than its CoAl2O4 parent compound using high resolution neutron Larmor diffraction. We further investigated the structure of this high-entropy material via Raman spectroscopy and extended x-ray absorption fine structure spectroscopy (EXAFS) measurements. From Raman spectroscopy measurements, we observed (MgMnFeCoNi)Al2O4 to display a combination of the active Raman modes in its parent compounds with the modes shifted and significantly broadened. This result, together with the varying bond lengths probed by EXAFS, reveals severe local lattice distortions in this high-entropy phase. Additionally, we found a substantial decrease in thermal conductivity and suppression of the low temperature thermal conductivity peak in (MgMnFeCoNi)Al2O4, consistent with the increased lattice defects and strain. These findings advance the understanding of the dependence of thermal expansion and transport on the lattice distortions in high-entropy materials.

Clustering-mediated enhancement of glass-forming ability and plasticity in oxygen-minor-alloyed Zr-Cu metallic glasses

A better metallic glass (MG) is usually more brittle as if there exists a tradeoff between glass-forming ability (GFA) and plasticity. However, recent experiments show that GFA and plasticity can be simultaneously enhanced via minor addition of oxygen into a Zr-Cu-based MG, a previously thought harmful element. In this work, using molecular dynamics (MD) simulations, we reveal that finely dispersed O-centered clusters (OCCs), being structurally compact and energetically stable at the both liquid and glass states, are responsible for the concurrent enhancement of GFA and plasticity in Zr-Cu MGs. The OCCs promote structural and dynamical heterogeneities in the supercooled liquid, leading to an enhanced GFA. Meanwhile, the densely packed OCCs collaborate with their loosely packed surroundings, amplifying structural fluctuations, facilitating formation of shear-transformation zones and thus enhancing plastic deformation. This work not only deepens the mechanistic understanding of glass formation and deformation behaviors of MGs, but also has important implications for developing low-cost MGs with low-grade raw materials containing oxygen.

Machine Learning Aided Prediction of Glass-Forming Ability of Metallic Glass

The prediction of the glass-forming ability (GFA) of metallic glasses (MGs) can accelerate the efficiency of their development. In this paper, a dataset was constructed using experimental data collected from the literature and books, and a machine learning-based predictive model was established to predict the GFA. Firstly, a classification model based on the size of the critical diameter (Dmax) was established to determine whether an alloy system could form a glass state, with an accuracy rating of 0.98. Then, regression models were established to predict the crystallization temperature (Tx), glass transition temperature (Tg), and liquidus temperature (Tl) of MGs. The R2 of the prediction model obtained in the test set was greater than 0.89, which showed that the model had good prediction accuracy. The key features used by the regression models were analyzed using variance, correlation, embedding, recursive, and exhaustive methods to select the most important features. Furthermore, to improve the interpretability of the prediction model, feature importance, partial dependence plot (PDP), and individual conditional expectation (ICE) methods were used for visualization analysis, demonstrating how features affect the target variables. Finally, taking Zr-Cu-Ni-Al system MGs as an example, a prediction model was established using a genetic algorithm to optimize the alloy composition for high GFA in the compositional space, achieving the optimal design of alloy composition.

Griffiths phase, re-entrant spin-glass behaviour and schottky anomaly in anti-site disordered double perovskite Pr2MnNiO6

In the present study, the effect of anti-site disorder on the magnetic properties of Pr2MnNiO6 is explored. Due to anti-site disorder, a reduced T C preceded by a Griffith phase has been observed. At low temperatures, we also report the development of the spin glass phase in co-existence with the cluster-like ferromagnetic order. The signature of the re-entrant spin glass phase, where the material is ferromagnetic below T c, and undergoes a transition to the spin glass state, is revealed by the frequency-dependent ac-susceptibility measurements. The spin glass behavior is also supported by the slow decay of thermo-remanent magnetization. The low temperature specific heat shows a small field dependent behaviour which may be attributed to Schottky effects.

Comparative analysis of process-induced strain glass states in austenitic and martensitic NiTi shape memory alloy plates

Strain glass alloys (SGAs) are metallic alloys with glassy martensitic nanodomains within a crystalline material that occur from compositionally or processing-induced strain. SGAs originate from shape memory alloys (SMAs) and exhibit similar shape memory properties and high actuation densities. The transition from SMA to SGA is relatively unexplored, and although there are similarities to amorphous SMAs and cold-worked SMAs, SGAs should be distinguished as a separate grouping. The transition occurs by interrupting the long-range martensitic order, which in turn disrupts the martensitic transformation, resulting in short-range martensitic order. A glassy martensitic phase is produced that exhibits enhanced structural and load-bearing abilities, functional stresses, and recoverability. In this study, the transformation from SMA to SGA is explored in two common commercially available SMAs, Ni49.5Ti50.5 and Ni50.8Ti49.2 (at. %), to compare martensitic versus austenitic SGAs, respectively. SMA plates were cold worked in 5% increments until a strain glass transition occurred. Characterizations of the samples at various stages of cold work were examined via differential scanning calorimetry (DSC), Vickers hardness, transmission electron microscopy (TEM), and synchrotron radiation X-ray diffraction (SR-XRD). Some prominent characteristics between the two plates, such as enthalpy peaks, twin size reduction, and crystallographic structure, were examined and compared to improve the understanding of the SMA to SGA transition.

Small-angle X-ray scattering analysis on the in-plane cluster distribution during heating amorphous Mg85Y9Cu6 alloys

In-plane cluster arrangements of a long-period stacking ordered (LPSO) structure in MgYCu alloys were examined by reverse Monte Carlo fitting of small-angle X-ray scattering (SAXS) intensities. In situ SAXS measurements were performed at a heating rate of 10 K min−1. from the glass state to the mp. The clusters were characterized as so-called L12 clusters commonly observed in the LPSO structures. The results suggest that the average in-plane distance of the clusters decreased during heating. The distance showed two preferred average distances, in contrast to the MgYZn case where the average distance decrease monotonically during heating.

Metastate analysis of the ground states of two-dimensional Ising spin glasses.

Using an efficient polynomial-time ground-state algorithm we investigate the Ising spin glass state at zero temperature in two dimensions. For large sizes, we show that the spin state in a central region is independent of the interactions far away, indicating a "single-state" picture, presumably the droplet model. Surprisingly, a single power law describes corrections to this result down to the smallest sizes studied.

Improved wear resistance of metallic glacier glass

Metallic glasses (MGs) have garnered significant attention due to their excellent properties, like high wear resistance, making them highly promising for a wide range of engineering applications. However, it is of significance to further increase the wear resistance of MGs, which has rarely been studied. Here we present a remarkable enhancement of wear resistance when some MGs undergo a liquid-liquid transition to form a new metallic glacial glass (MGG) state. Within an identical composition of La65Ni20Al15, the wear resistance of the MGG exhibits a notable superiority of 104% compared to the as-cast MG, and an even more remarkable advantage of 349% compared to its crystalline counterpart. The excellent wear resistance of the MGG is attributed to its ultrastable nature in energy confirmed by dynamic relaxation changes. This work not only offers a unique perspective on MGGs, but also provides an effective technique for developing wear-resistant materials.

Emerging exotic compositional order on approaching low-temperature equilibrium glasses

The ultimate fate of a glass former upon cooling has been a fundamental problem in condensed matter physics and materials science since Kauzmann. Recently, this problem has been challenged by a model with an extraordinary glass-forming ability effectively free from crystallisation and phase separation, two well-known fates of most glass formers, combined with a particle-size swap method. Thus, this system is expected to approach the ideal glass state if it exists. However, we discover exotic compositional order as the coexistence of space-spanning network-like structures formed by small-large particle connections and patches formed by medium-size particles at low temperatures. Therefore, the glass transition is accompanied unexpectedly by exotic compositional ordering inaccessible through ordinary structural or thermodynamic characterisations. Such exotic compositional ordering is found to have an unusual impact on structural relaxation dynamics. Our study thus raises fundamental questions concerning the role of unconventional structural ordering in understanding glass transition.

Tailoring Mid‐Gap States of Chalcogenide Glass by Pressure‐Induced Hypervalent Bonding Towards the Design of Electrical Switching Materials

AbstractPhase change memory (PCM) and ovonic threshold switching (OTS) materials using chalcogenide glass are essential elements in advanced 3D memory chips. The mid‐gap states, induced by the disorder and defects in the glass, are the physical mechanisms of the electrical switching behavior, while the origin of these trap states is still under debate and the medium‐range clusters that break the global octet rule, such as over‐coordinated atoms, are known to be responsible in various glass. Here, it is discovered that a large fraction of over‐coordinated clusters fails to generate mid‐gap states, which are probably caused by hypervalent bonding, a multi‐centered covalent bond participated by delocalized lone‐pair electrons. This is confirmed by the pressure‐driven simulations of amorphous GeSe models, in which it is found that octahedral motifs and hypervalent bonds prevent the over‐coordinated medium‐range clusters from providing excessive electrons. In practical applications, compatible dopants can be used to change the number of hypervalent bonds, thus controlling the number of mid‐gap states and consequently the performance of PCM and OTS materials. These results reveal the origin of mid‐gap states in chalcogenide glasses, enabling extensive control in the development of pioneering electrical switching materials.

Study of the de Almeida-Thouless line in the one-dimensional diluted power-law XY spin glass.

We study the de Almeida-Thouless (AT) line in the one-dimensional power-law diluted XY spin-glass model, in which the probability that two spins separated by a distance r interact with each other, decays as 1/r^{2σ}. Tuning the exponent σ is equivalent to changing the space dimension of a short-range model. We develop a heat bath algorithm to equilibrate XY spins; using this in conjunction with the standard parallel tempering and overrelaxation sweeps, we carry out large-scale Monte Carlo simulations. For σ=0.6, which is in the mean-field regime above six dimensions-it is similar to being in 10 dimensions-we find clear evidence for an AT line. For σ=0.75 and σ=0.85, which are in the non-mean-field regime and similar to four and three dimensions, respectively, our data is like that found in previous studies of the Ising and Heisenberg spin glasses when reducing the temperature at fixed field. For σ=0.75, there is evidence from finite-size-scaling studies for an AT transition but for σ=0.85, the evidence for a transition is nonexistent. We have also studied these systems at fixed temperature varying the field and discovered that at both σ=0.75 and at σ=0.85 there is evidence of an AT transition! Confusingly, the correlation length and spin-glass susceptibility as a function of the field are both entirely consistent with the predictions of the droplet picture and hence the nonexistence of an AT line. In the usual finite-size critical point scaling studies used to provide evidence for an AT transition, there is seemingly good evidence for an AT line at σ=0.75 for small values of the system size N, which is strengthening as N is increased, but for N>2048 the trend changes and the evidence then weakens as N is further increased. We have also studied with fewer bond realizations the system at σ=0.70, which is the analog of a system with short-range interactions just below six dimensions, and found that it is similar in its behavior to the system at σ=0.75 but with larger finite-size corrections. The evidence from our simulations points to the complete absence of the AT line in dimensions outside the mean-field region and to the correctness of the droplet picture. Previous simulations which suggested there was an AT line can be attributed to the consequences of studying systems which are just too small. The collapse of our data to the droplet scaling form is poor for σ=0.75 and to some extent also for σ=0.85, when the correlation length becomes of the order of the length of the system, due to the existence of excitations which only cost a free energy of O(1), just as envisaged in the TNT picture of the ordered state of spin glasses. However, for the case of σ=0.85 we can provide evidence that for larger system sizes, droplet scaling will prevail even when the correlation length is comparable to the system size.

Molecular Origin of the Reinforcement Effect and Its Strain-Rate Dependence in Polymer Nanocomposite Glass.

We investigate the molecular origin of mechanical reinforcement in a polymer nanocomposite (PNC) under a glass state via molecular dynamics simulations. The strength of the PNC system is found to be reinforced mainly via reduced plastic deformations of the nanoparticle neighborhood (NN). Such a reinforcement effect is found to decay with an increase in the strain rate. The Arrhenius-Eyring relation is used to analyze its origin. The amplitude of the reinforcement is found to be determined by the difference between the energy barrier (ΔE) for the activation of NN and the work (W) done by the applied stress to conquer that barrier. A larger strain rate is found to result in a larger W and, hence, a weaker reinforcement effect. Such a strain-rate dependence is verified in the experimental tensile tests of a poly(vinyl alcohol)/SiO2 composite system. These results not only provide a new understanding of the molecular origin of the reinforcement effect in the PNC system, but also pave the way for a better design of the PNC material properties.

Disorder induced cluster spin glass like state in MnFeSb

Hexagonal MnSb is a ferromagnet with Curie temperature and saturation magnetization values of 587 K and 110 emu/g, respectively. In this paper, the origin of the complex magnetic behavior of a single phase MnFe0.20Sb prepared using solid-state reaction method is examined. A thorough investigation of temperature dependent magnetization and magnetic relaxation measurements reveals the presence of a glassy like phase below 15 K. AC susceptibility measurements revealed the existence of a cluster glass-like state with a freezing temperature of 18 K. The presence of competing magnetic interactions and random occupation of Fe atoms at 2d site leads the system to exhibit a cluster glass state. Furthermore, resistivity measurements indicate that the material exhibits a Kondo-like behavior below 30 K and can be attributed to the interaction of conduction electrons with localized Mn moments.

Evaluation study on experimental and theoretical simulation elastic properties analysis of neodymium-doped magnesium borotellurite glasses

This study investigated the elastic, structural, and physical of magnesium borotellurite glasses modified with neodymium oxide. The bulk sample's density increased from 3.97 g/cm3 to 4.10 g/cm3 by raising the Nd2O3 concentration while molar volume illustrated a contrary trend. X-ray diffraction analysis proves the amorphous state of glasses and elastic moduli demonstrated a linear increase with the increment of Nd2O3. The elastic modulus shows and increasing trend with the progress of neodymium concentration. The elastic moduli from Makishima-Mackenzie and Rocherulle’s model followed the same trend as the experimental values. The results show that the MBTNd-3 glass sample currently has the optimum properties, indicating that the MBTNd-3 glass sample is potentially used for high-strength glass applications.

Melt pool size of optical glass irradiated by semiconductor laser

ABSTRACT Using a continuous laser to soften glass locally is a novel way of selective glass forming. Due to gaussian distribution of laser power density, a temperature gradient will be generated on glass treated with localized irradiation by laser, which brings about the coexistence of a glass state and a viscoelastic state. This situation creates a bulge on the surface of the softened area. Based on this phenomenon, we propose a measurement approach and a calculation model for the softening zone width of glass irradiated locally by laser and verify the calculation model through simulations and experiments. The maximum temperature deviation of the proposed temperature field prediction model is 4.7°C, while the minimum deviation is 0.53°C; making the deviation between the calculation model of the softening zone width and the experimental measurement result less than 0.319%.