Vitrification Research Articles

In-situ and quantitative imaging of evaporation-induced stratification in binary suspensions

The drying of a multi-component dispersion, such as water-based paint, ink and sunscreen to form a solid film, is a widespread process. Binary colloidal suspensions have proven capable of spontaneous layer formation through size segregation during drying. To design bespoke stratification patterns, a deeper understanding of how these emerge is crucial. Here, we visualize and quantify the spatiotemporally evolving concentration profiles in situ and with high resolution using confocal fluorescence microscopy of custom-designed binary dispersions in a well-defined geometry. Our results conclusively establish two distinct stratification routes, which give rise to three layered structures. A first thin layer develops directly underneath the evaporation front in which large particles are kinetically trapped. At later times, asymmetrical particle interactions lead to the formation of two subsequent layers enriched in small and large particles, respectively. The spatial extent and magnitude of demixing strongly depend on the initial volume fraction. We explain and reproduce the experimental concentration profiles using a theoretical model based on dynamic arrest and higher-order thermodynamic and hydrodynamic interactions. These insights unravel the key mechanisms underlying colloidal auto-stratification in multi-component suspensions, and allow preprogramming of stratification patterns in single-deposition formulations for future applications.

Towards commonality between shear banding and glass-liquid transition in metallic glasses

Despite the high attendance of shear banding in metallic glasses and other disordered materials, the nature of the emergence of shear band is still mysterious. Using molecular dynamics simulations, a set of detailed characterizations of shear band in a typical ${\mathrm{Cu}}_{50}{\mathrm{Zr}}_{50}$ metallic glass is obtained. Then we uncover a large number of robust and intriguing commonalities between the emergence of shear bands and the glass-to-liquid transition, including strong similarities on viscosity drop, enthalpy discontinuity, breakdown of hard backbone network, as well as relaxation process. Such observations indicate that shear banding in metallic glasses is a consequence of deformation-controlled glass transition, as further quantitatively validated via the compelling overlap between the venerable Vogel-Fulcher-Tammann law (and Adam-Gibbs relation) and the evolving glass state of shear band controlled by configurational temperature. These results provide a direct bridge between shear banding and glass-to-liquid transition and are instrumental to build the unified framework of flow behavior induced either by thermal or stressed stimuli in disordered materials.

EPR, NMR, DFT and XPS study on LaAlO3 phase transition in glass and influence on glass structure and properties

Thermal treatment induced phase transition of LaAlO3 in glass and its influence on glass structure and dielectric, magnetic, and Faraday rotation properties were characterized through various techniques such as nuclear magnetic resonance, X-ray neutron diffraction, transmission electron microscopy, X-ray photoelectron microscopy, vibrating-sample magnetometer, and electron paramagnetic resonance. Cubic LaAlO3 nanocrystals were synthesized and incorporated into lead-tellurite glasses, after crystallization treatment at 380 °C for 2 h, 14-17 nm-cubic LaAlO3 nanocrystals were changed to 14-27 nm-rhombohedral LaAlO3 perovskite due to the temperature-induced viscosity and strain in the melt. The phase transition of LaAlO3 nanocrystals in glass matrix was verified through versatile techniques in terms of the octahedral AlO6 distortion, SAED patterns, changes of lattice parameters calculated by Rietveld refinement, and coordination number changes of AlO6 by NMR and XPS techniques. The modification to the glass structure was yielded by phase transition through converting TeO4→TeO3, AlO6→AlO4, BO4→BO3, and producing non-bridging oxygen. In addition, the energy band gap and density of states of glass after phase transition was calculated through Density functional theory (DFT) simulation. Glass doped with 10% LaAlO3 exhibited a promising dielectric constant and good thermal stability due to the phase transition induced polarizability, and improved optical and magnetic performance which is promising for photonics device applications.

Mesoscale structure–function relationships in mitochondrial transcriptional condensates

In live cells, phase separation is thought to organize macromolecules into membraneless structures known as biomolecular condensates. Here, we reconstituted transcription in condensates from purified mitochondrial components using optimized invitro reaction conditions to probe the structure-function relationships of biomolecular condensates. We find that the core components of the mt-transcription machinery form multiphasic, viscoelastic condensates invitro. Strikingly, the rates of condensate-mediated transcription are substantially lower than in solution. The condensate-mediated decrease in transcriptional rates is associated with the formation of vesicle-like structures that are driven by the production and accumulation of RNA during transcription. The generation of RNA alters the global phase behavior and organization of transcription components within condensates. Coarse-grained simulations of mesoscale structures at equilibrium show that the components stably assemble into multiphasic condensates and that the vesicles formed invitro are the result of dynamical arrest. Overall, our findings illustrate the complex phase behavior of transcribing, multicomponent condensates, and they highlight the intimate, bidirectional interplay of structure and function in transcriptional condensates.

THERMAL EXCITATION ENERGY OF TRAPPED ELECTRONS AT LOW TEMPERATURE STUDIED THROUGH POSITRON ANNIHILATION LIFETIME SPECTROSCOPY

Positronium (Ps) formation has been studied in high density polyethylene (HDPE) below and around gamma transition temperature (Tγ). The increase in ortho-positronium (o-Ps) intensity (I3) with time due to trapped electrons at different rate has been discussed in terms of different possible models. Some calculation have been performed to find the thermal activation energy of trapped electrons.

Sensitization effect of Nd3+ ions on Yb3+/Nd3+ co-doped oxyfluoride glasses and study of their optical, fluorescence, and upconversion abilities for visible laser and NIR amplifier applications

The development of laser technology has created intense demand for optical confinement materials with high performance. Herein the authors have been investigated Yb 3+ -singly doped and Yb 3+ /Nd 3+ -codoped SiO 2 -based oxyfluoride glasses in terms of their optical absorption, and their near-infrared (NIR) and up-conversion (UC) emissions including emission decay profiles. Under 808 nm laser diode (LD) excitation, four NIR emission bands were observed i.e., (Nd 3+ : 4 F 3/2 → 4 I 9/2 , Yb 3+ : 2 F 5/2 → 2 F 7/2 , Nd 3+ : 4 F 3/2 → 4 I 11/2 , and Nd 3+ : 4 F 3/2 → 4 I 13/2 ) in co-doped glasses. NIR emission cross-sections [ (σ emi ) stimulated, (σ M emi ) from Mc-cumber theory] were calculated for 2 F 5/2 → 2 F 7/2 (∼1030 nm) transition of Yb 3+ ion. σ emi was found to be highest (26.27 × 10 −21 cm 2 ) for the Yb 3+ : 2 F 5/2 → 2 F 7/2 transition in N2 glass. UC emission spectra recorded at 980 nm LD show bands centered at 500, 536, 595 & 610, and 664 nm, attributed to 4 G 9/2 → 4 I 9/2 , 4 G 7/2 → 4 I 9/2 & 4 G 7/2 → 4 I 11/2, 4 G 5/2 → 4 I 9/2 , and 4 G 9/2 → 4 I 13/2 transitions, respectively. Decay profiles were analyzed for Yb 3+ : 2 F 5/2 → 2 F 7/2 (∼1030 nm) and Nd 3+ : 4 F 3/2 → 4 I 11/2 (∼1057 nm) transitions at 808 nm LD. Energy transfer (ET) process from Nd 3+ to Yb 3+ in present glasses were detailed.

Configurational Entropy Effects on Glass Transition in Metallic Glasses.

Configurational entropy (Sconf) is known to be a key thermodynamic factor governing a glass transition process. However, this significance remains speculative because Sconf is not directly measurable. In this work, we demonstrate the role of Sconf theoretically and experimentally by a comparative study of a Zr-Ti-Cu-Ni-Be high-entropy metallic glass (HE-MG) with one of its conventional MG counterparts. It is revealed that the higher Sconf leads to a glass that is energetically more stable and structurally more ordered. This is manifested by ab initio molecular dynamics simulations, showing that ∼60% fewer atoms are agitated above Tg, and experimental results of smaller heat capacity jump, inconspicuous stiffness loss, insignificant structural change during glass transition, and a more depressed boson peak in the HE-MG than its counterpart. We accordingly propose a model to explain that a higher Sconf promotes a faster degeneracy-dependent kinetics for exploration of the potential energy landscape upon glass transition.

Precise conversion electron intensities of low energy gamma transitions for efficiency calibration of electron detectors

Precise energies and relative intensities of gamma transitions and conversion electrons in the electron capture decay of 153Gd have been determined independently with our well-tested and optimized gamma and electron spectrometers - a large-volume (60 cc) HPGe detector and a mini-orange electron transporter paired to a Si(Li) detector, respectively. The experimental internal conversion coefficients of the gamma transitions in 153Eu have been determined using Normalized Peak to Gamma method and compared with the theoretical values adopted by Nuclear Data Sheets to assign multipolarities of all the transitions. The precise internal conversion electron intensities of the low energy transitions can be used as standards for calibration purposes of electron detectors and spectrometers.

Iso-conversional analysis of thermally induced glass transition in some quaternary glasses of SeTeSnGe system

The study of glass transition and its consequences is an essential task to decide the utility of glasses (ChGs) at the industrial level. The model fitting non-isothermal methods provide information about the glass transition in terms of the related overall activation energy. However, thermal analysis of the activation energy at the different extent of conversions reveals the features of glass transition more deeply as compared to the non-isothermal model-fitting methods. Keeping in mind this fact, we have studied the iso-conversional glass transition in Se78-xTe20Sn2Gex (STSG ChGs, x = 0, 2, 4, and 6) glasses using calorimetric experiments in Differential Scanning Calorimetry (DSC).The temperature dependence of the extent of conversion (i.e., glass transition fraction αg) and the variation of activation energy Eg and rate constant with αg have been studied. Further, the various heating rate method has been chosen to study the correlation between the iso-conversional rate constant and corresponding activation energy. The variation of Eg with αg for the present samples of Se78-xTe20Sn2Gex indicates the occurrence of the rigidity transitions after x = 2 because of the abrupt growth in the number density of edge-sharing tetrahedral species of GeSe4 over the corner-sharing species.

Temperature Dependence of Structural Relaxation in Glass-Forming Liquids and Polymers.

Understanding the microscopic mechanism of the transition of glass remains one of the most challenging topics in Condensed Matter Physics. What controls the sharp slowing down of molecular motion upon approaching the glass transition temperature Tg, whether there is an underlying thermodynamic transition at some finite temperature below Tg, what the role of cooperativity and heterogeneity are, and many other questions continue to be topics of active discussions. This review focuses on the mechanisms that control the steepness of the temperature dependence of structural relaxation (fragility) in glass-forming liquids. We present a brief overview of the basic theoretical models and their experimental tests, analyzing their predictions for fragility and emphasizing the successes and failures of the models. Special attention is focused on the connection of fast dynamics on picosecond time scales to the behavior of structural relaxation on much longer time scales. A separate section discusses the specific case of polymeric glass-forming liquids, which usually have extremely high fragility. We emphasize the apparent difference between the glass transitions in polymers and small molecules. We also discuss the possible role of quantum effects in the glass transition of light molecules and highlight the recent discovery of the unusually low fragility of water. At the end, we formulate the major challenges and questions remaining in this field.

Effects of interstitial water on phase transition of forsterite glass

To investigate the effects of interstitial water on phase transition mechanisms of forsterite glass, we performed molecular dynamics calculations of forsterite-water systems. The results show that the density of the interstitial water is higher than that of ordinary water. This suggests that the interstitial water can be a liquid state in forsterite glass at temperatures above the boiling point without pressurization. Furthermore, the formation of the magnesium hydroxide crystal from the dissolved MgOxHy in the high-density water was observed. The unique property of the interstitial water is an important factor to understand the evolution processes of silicate minerals in space.

Insights into the microevolution of SARS-ACE2 interactions: in silico analysis of glycosylation and SNP pattern

The prefatory protein–glycan interaction and stabilizing protein–protein interaction of severe acute respiratory syndrome viruses with angiotensin-converting enzyme 2 play a significant role in complex formation thereby promoting endocytosis. The microevolution of SARS-CoV-2 over a period of time has a significant role in increasing the affinity of receptor-binding domain against angiotensin converting-enzyme 2. In this study, we have corroborated the vitality of acquired SNPs over a period of time with increased affinity by using docking studies. The results indicate that the virus modulates the undesirable glycosylation sites by a series of substitution and deletion mutations. It uses bulky residues such as Tyr/Phe for dynamic arrest for quick stabilization of the complex, and Lys residues for stabilizing via hydrogen bond formation besides increasing the binding affinity to ease the cell entry. Communicated by Ramaswamy H. Sarma

Microscopic dynamics underlying the stress relaxation of arrested soft materials

Arrested soft materials such as gels and glasses exhibit a slow stress relaxation with a broad distribution of relaxation times in response to linear mechanical perturbations. Although this macroscopic stress relaxation is an essential feature in the application of arrested systems as structural materials, consumer products, foods, and biological materials, the microscopic origins of this relaxation remain poorly understood. Here, we elucidate the microscopic dynamics underlying the stress relaxation of such arrested soft materials under both quiescent and mechanically perturbed conditions through X-ray photon correlation spectroscopy. By studying the dynamics of a model associative gel system that undergoes dynamical arrest in the absence of aging effects, we show that the mean stress relaxation time measured from linear rheometry is directly correlated to the quiescent superdiffusive dynamics of the microscopic clusters, which are governed by a buildup of internal stresses during arrest. We also show that perturbing the system via small mechanical deformations can result in large intermittent fluctuations in the form of avalanches, which give rise to a broad non-Gaussian spectrum of relaxation modes at short times that is observed in stress relaxation measurements. These findings suggest that the linear viscoelastic stress relaxation in arrested soft materials may be governed by nonlinear phenomena involving an interplay of internal stress relaxations and perturbation-induced intermittent avalanches.

Anomalous rheological aging of a model thermoreversible colloidal gel following a thermal quench.

We investigate the aging behavior in a well-studied model system comprised of a colloidal suspension of thermoreversible adhesive hard spheres (AHS) but thermally quenched below the gel transition to much larger depths than previously studied. The aging behavior in the model AHS system is monitored by small amplitude oscillatory shear rheology measurements conducted while rapidly quenching from the liquid state at 40 °C to a temperature below the gel temperature, and new, anomalous aging behaviors are observed. Shallow quenches lead to monotonic development of the elastic modulus with time, consistent with prior reports for the development of a homogeneous gel [Gordon et al., J. Rheol. 61, 23-34 (2017)]. However, for deeper quenches, a unique and new phenomenon is reported, namely, after an initial rise in the modulus, a reproducible drop in the modulus is observed, followed by a plateau in the modulus value. This drop can be gradual or sudden and the extent of the drop depends on the quench depth. After this drop in the modulus, AHS gel evolves toward a quench-path independent state over the experimental timescale. These effects of the extent of quenching on aging behavior are hypothesized to be a consequence of quenching into different underlying thermodynamic states of colloidal gels and the possible influence of the adhesive glass dynamical arrest for the deepest quenches. The research connects homogeneous gelation with heterogeneous gel formation due to phase separation and shows that the extent of quench can be used as an independent parameter to govern the rheological response of the arrested gel.

Comment on "Communication: Is directed percolation in colloid-polymer mixtures linked to dynamic arrest?" [J. Chem. Phys. 148, 241101 (2018)

In their Communication [J. Chem. Phys. 148, 241101 (2018)], Richard et al. state that in the work of Kohl et al. [Nat. Commun. 7, 11817 (2016)], a mechanism for dynamical arrest in temporal networks has been proposed that actually has never been proposed (and would be obviously wrong) in this context. The actual findings of Kohl et al. are not tested nor affected by the communication. The work of Richard et al. rests on simulations in a regime of the phase diagram that significantly differs from the one that Kohl et al. consider. In this Comment, it is shown that both the effective density and the rescaled second virial coefficient indicate that the comparison presented by Richard et al. is invalid. Therefore, the implications that are based on this comparison are incorrect. There is no indication for a disagreement between the simulations of Richard et al. and those of Kohl et al., and I am confident that upon consistent comparison and interpretation of the results, both works can contribute to a more comprehensive picture of gel-forming systems.

Response to "Comment on 'Communication: Is directed percolation in colloid-polymer mixtures linked to dynamic arrest?'" [J. Chem. Phys. 157, 027101 (2022)

None

DNA fragmentation of equine cumulus cells from Cumulus-Oocyte complexes submitted to vitrification and its relationship to the developmental competence of the oocyte.

The objectives of this study were to evaluate the effect of vitrification on the DNA fragmentation rate of equine cumulus cells and to assess its relationship to oocyte in vitro maturation (IVM) after vitrification. Cumulus cells (CC) from 14 mares were recovered from COCs, previously submitted to vitrification (VIT) and IVM. The DNA fragmentation rate of the cumulus cells (CC-DF) was assessed using a chromatin dispersion test. CC-DF rates between vitrified and control COCs were statistically compared by Student's t-test. The rates of CC-DF from control COCs were lower than in vitrified COCs. The percentage of CC-DF was not significantly different (p > .05) between groups of COCs able to reach metaphase II (MII > 0) and those in which oocyte maturation was not achieved (MII=0). In conclusion, vitrification has a deleterious effect on the DNA fragmentation of equine cumulus cells; however, this parameter cannot be used as a predictor for IVM success after COCs vitrification.

The effect of inter-particle hydrodynamic and magnetic interactions in a magnetorheological fluid

A magnetorheological fluid, which consists of magnetic particles suspended in a viscous fluid, flows freely with well-dispersed particles in the absence of a magnetic field, but particle aggregation results in flow cessation when a field is applied. The mechanism of dynamical arrest is examined by analysing interactions between magnetic particles in a magnetic field subject to a shear flow. An isolated spherical magnetic particle undergoes a transition between a rotating state at low magnetic field and a static orientation at high magnetic field. The effect of interactions for spherical dipolar and polarisable particles with static orientation is examined for an unbounded dilute viscous suspension. There are magnetic interactions due to the magnetic field disturbance at one particle caused by the dipole moment of another, hydrodynamic interactions due to the antisymmetric force moment of a non-rotating particle in a shear flow, and a modification of the magnetic field due to the particle magnetic moment density. When there is a concentration variation, the torque balance condition results in a disturbance to the orientation of the particle magnetic moment. The net force and the drift velocity due to these disturbances is calculated, and the collective motion generated is equivalent to an anisotropic diffusion process. When the magnetic field is in the flow plane, the diffusion coefficients in the two directions perpendicular to the field direction are negative, implying that concentration fluctuations are unstable in these directions. This instability could initiate field-induced dynamical arrest in a magnetorheological fluid.

Crystallization Kinetics of Basalt Glass-Ceramics Produced from Olivine Basalt Rock

Glass-ceramics acquired from the melting of rocks have a vast application marketplace. In this study, an olivine basalt rock from Zhangjiakou in China was selected as a raw material to prepare basalt glass-ceramics, and the crystallization kinetics of olivine basalt glass was investigated using differential thermal analysis. Polarizing microscope and X-ray diffraction (XRD) analysis results revealed that the main mineral compositions of olivine basalt are plagioclase, pyroxene, olivine, and iron oxide(s). Three crystallization peaks were observed in the DSC curve of the olivine basalt glass. The Avrami exponent (n), apparent activation energies for the crystallization, and glass transition of basalt glass were determined using the Owaza method based on data obtained from isothermal measurements. The crystallization activation energies (E) of the three crystallization peaks of olivine basalt glass were 314.20 kJ/mol, 1232.49 kJ/mol, and 696.89 kJ/mol, respectively. In addition to this, the crystal growth index indicated that the crystallization mode in the olivine basalt glass was surface crystallization. The crystallization phases and microstructure of the olivine basalt glass heated at 860 °C, 1100 °C, and 1180 °C were also studied. The conclusions obtained offer some useful information for the preparation of basalt glass-ceramics from olivine basalt rocks.

Experimental evidences of shape co-existence in 154Ho

The excited states of odd-odd 154Ho nucleus have been studied by the 141Pr(16O, 3n)154Ho reaction at Elab= 82 MeV utilizing the Indian National Gamma Array (INGA) setup at BARC-TIFR Pelletron facility, Tata Institute of Fundamental Research, Mumbai. Data from γ−γ coincidence, directional correlation (DCO), and polarization measurements have been analyzed to assign and confirm the spins and parities of the levels. The reported level scheme of 154Ho has been improved by including new levels and transitions. Mixing ratios for the mixed transitions extracted from DCO ratios and parity assignments from polarisation data are reported for the first time. The low-lying states in H154o, which are mostly collective, characterized by regularity in the excitation spectra, are proposed to be arising from neutron excitation. At higher excitation, there is a transition from collective to single-particle character, accompanied by the appearance of irregular and complex structure caused by proton excitation. The newly identified E1 gamma transitions connecting the low-lying positive and negative parity bands indicate octupole correlation in 154Ho. These new connections also support the phenomenological analysis to interpret the observed experimental features from a different perspective.