Liquid-like Structure Research Articles

Odd–Even Effect in Molecular Packing of Self-Assembled Monolayers of Biphenyl-Substituted Fatty Acid on Ag(111)

Self-assembled monolayers (SAMs) of the homologous series of biphenyl-substituted fatty acids on Ag(111) in the form of (C6H4)2–(CH2)n–COO/Ag (BPnCOO/Ag, n = 1–4) were studied using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM). The combination of spectroscopic (IRRAS and XPS) and microscopic analyses (STM) revealed that depending on the parity of the parameter n, which defines the length of the short aliphatic linker, two types of structures are formed by the BPnCOO/Ag. For n = even, highly ordered and stable SAMs are formed in a very short time. For n = odd, the respective monolayers have a disordered liquidlike structure with more canted orientation of the molecular backbone and the anchoring carboxylic group, which results in lower packing density and film thickness compared to the even-numbered SAMs. By comparing obtained results with former odd–even effects reported for analogous SAMs based on thiols and selenols,...

Water Adsorption Isotherms on Fly Ash from Several Sources.

In this study, horizontal attenuated total reflection (HATR) Fourier-transform infrared (FT-IR) spectroscopy was combined with quartz crystal microbalance (QCM) gravimetry to investigate the adsorption isotherms of water on fly ash, a byproduct of coal combustion in power plants. Because of composition variability with the source region, water uptake was studied at room temperature as a function of relative humidity (RH) on fly ash from several regions: United States, India, The Netherlands, and Germany. The FT-IR spectra show water features growth as a function of RH, with water absorbing on the particle surface in both an ordered (ice-like) and a disordered (liquid-like) structure. The QCM data was modeled using the Brunauer, Emmett, and Teller (BET) adsorption isotherm model. The BET model was found to describe the data well over the entire range of RH, showing that water uptake on fly ash takes place mostly on the surface of the particle, even for poorly combusted samples. In addition, the source region and power-plant efficiency play important roles in the water uptake and ice nucleation (IN) ability of fly ash. The difference in the observed water uptake and IN behavior between the four samples and mullite (3Al2O3·2SiO2), the aluminosilicate main component of fly ash, is attributed to differences in composition and the density of OH binding sites on the surface of each sample. A discussion is presented on the RH required to reach monolayer coverage on each sample as well as a comparison between surface sites of fly ash samples and enthalpies of adsorption of water between the samples and mullite.

Oxygen Redox Reaction in Lithium-based Electrolytes: from Salt-in-Solvent to Solvent-in-Salt

Electrolytes are key components of Li/O2 batteries. The ionic liquid-like structure and good electrochemical and thermal stability of solvent-in-salt electrolytes make them of great interest for lithium batteries. Solutions of lithium bis(trifluoromethanesulfonyl)imide in tetraethylene glycol dimethyl-ether with molar ratios ranging from 1:9 to 1:0.9 are here investigated. A voltammetric study of oxygen redox reaction in presence of different concentrations of salt, from salt-in-solvent to solvent-in-salt solutions, is reported here for the first time along with a novel luminescence method for the evaluation of O2 solubility. The results indicate that superconcentrated solutions favor the solution formation mechanism of Li2O2 during discharge which in turn is beneficial for battery cycling stability. Despite the higher viscosity of solvent-in-salt solutions than conventional electrolytes, O2 solubility is improved at the highest salt concentrations. These findings contribute to understand electrochemical processes in solvent-in-salt solutions for Li/O2 and next generation metal-based batteries.

Long-Lived Neighbors Determine the Rheological Response of Glasses.

Glasses exhibit a liquidlike structure but a solidlike rheological response with plastic deformations only occurring beyond yielding. Thus, predicting the rheological behavior from the microscopic structure is difficult, but important for materials science. Here, we consider colloidal suspensions and propose to supplement the static structural information with the local dynamics, namely, the rearrangement and breaking of the cage of neighbors. This is quantified by the mean squared nonaffine displacement and the number of particles that remain nearest neighbors for a long time, i.e., long-lived neighbors, respectively. Both quantities are followed under shear using confocal microscopy and are the basis to calculate the affine and nonaffine contributions to the elastic stress, which is complemented by the viscoelastic stress to give the total stress. During start-up of shear, the model predicts three transient regimes that result from the interplay of affine, nonaffine, and viscoelastic contributions. Our prediction quantitatively agrees with rheological data and their dependencies on volume fraction and shear rate.

Coexistence of ice clusters and liquid-like water clusters on the Ru(0001) surface.

The RAIRS spectra of water adsorbed on Ru(0001) at 85 K are recorded from 600 cm-1 to 4000 cm-1. Measured at water coverages from 0.13 ML to 2.0 ML, the RAIRS spectra suggest that chemisorption of water on Ru(0001) depends on coverage. Water adsorbs on a clean Ru surface as chemisorbed ice-like clusters (likely through an O-Ru bond) up to 0.33 ML. Above this coverage, the chemisorbed layer saturates. Upon more exposure, water adsorbs as a liquid-like H-bonded layer without bonding to the Ru substrate. The chemisorbed water absorbs 7 times less IR per molecule than the liquid-like structure, which indicates that the orientation of the chemisorbed water is more parallel to the surface. Additionally, the influence of water-Ru bonding on H-bonding is reflected in the OH symmetric stretching mode. Under perturbation from water-Ru bonding, a large red shift (40 cm-1) in the free OH stretching frequency is observed in the chemisorbed clusters. By deconvoluting the main H-bonded OH stretching peak into five Gaussian sub-bands at 2945 ± 5 cm-1, 3210 ± 5 cm-1, 3300 ± 15 cm-1, 3430 ± 5 cm-1 and 3570 ± 10 cm-1, changes in the H-bonding network are rationalized in terms of H-bonding motifs. The donor-acceptor-acceptor motif is significant only in the chemisorbed clusters. On the other hand, the donor-acceptor motif dominates in the liquid-like structure, which increases the disorder present in the adlayer. Although chemisorption is suppressed above 0.33 ML, no structural changes in the ice-like clusters are observed up to multilayer coverage. Therefore, ice-like and liquid-like water coexist in a meta-stable state at 85 K.

Structure and Dynamics of Ionic Liquid [MMIM][Br] Confined in Hydrophobic and Hydrophilic Porous Matrices: A Molecular Dynamics Simulation Study.

The effects of confinement on the structural and dynamical properties of the ionic liquid (IL) 1,3-dimethylimidazolium bromide ([MMIM][Br]) have been investigated by molecular dynamics simulations. We used zeolite faujasite (NaY) as a hydrophilic confinement and dealuminated faujasite (DAY) as a hydrophobic confinement. The presence of an extra framework cation, [Na+], in NaY makes the host hydrophilic, whereas DAY, with no extra framework cation, is hydrophobic. Although both NaY and DAY have almost similar structures, the IL showed markedly different structural and dynamical properties in these confinements and in bulk. In the confinements, the cation-cation radial distribution function, which strongly depends on temperature, exhibits a layer-like structure, whereas in bulk, it shows a liquid-like structure that hardly depends on temperature. Although the interaction between [MMIM]+ and Br- in DAY is stronger than that in both NaY and bulk, the strength of the interaction between them is almost invariant with temperature. Both [MMIM]+ and Br- strongly interact with Na+ of the host, and their interaction strongly depends on temperature, whereas the interaction of the IL with Si and O is very weak and invariant with temperature. In bulk, the self-diffusion coefficient, [D], of both [MMIM]+ and Br- increases exponentially with temperature, and the D of the cation is slightly higher than that of the anion at all studied temperatures, whereas in the confinements, [MMIM]+ moves much faster than Br-. For example, in the hydrophilic confinement, the D of the cation is 20-30 times higher than that of the anion. The D of both the ions decreases significantly in the confinements as compared to that in bulk. During diffusion, [MMIM]+ diffuses closer to the inner surface in the hydrophilic confinement than that in the hydrophobic confinement. The diffusion pathway imperceptibly depends on temperature but strongly depends on the nature of the confinement. The self part of the time-dependent van Hoove correlation function of [MMIM]+ in the hydrophilic confinement shows a larger deviation from its Gaussian form than that in the hydrophobic confinement at all temperatures, indicating that the long-time dynamics of [MMIM]+ in NaY is more heterogeneous than that in DAY. Although the orientational relaxation time scales of [MMIM]+ in the confinements significantly slowed as compared to those in bulk, confinement does not affect the librational motion of the collective hydrogen-bond network present in the IL.

Ternary Solid–Liquid Equilibria of Semicrystalline, Branched Polymer Solvent Mixtures—A Theoretical Study by Means of Lattice Cluster Theory

Analytical polymer separation techniques, like CRYSTAF (crystallization analysis fractionation) and TREF (temperature rising elution fractionation), play a crucial role in gaining insight into the interrelation between molecular architecture and properties. Often polymer samples are semicrystalline, as it consists of amorphous regions which exhibit a liquid-like structure, and ordered crystallized structures called crystallites. Additionally, polymers exhibit a certain degree of short-chain branching, and they are polydisperse with respect to molecular weight and chemical composition. To explain the theoretical background of common polymer separation techniques, a fair prediction of solid–liquid equilibria (SLE) of polymer solvent systems is required. By application of Lattice Cluster Theory (LCT), developed by Freed and co-workers, the molecular architecture can be considered. Recently, LCT was applied to calculate the SLE of binary semicrystalline, high-polymer solvent mixtures having an arbitrary molec...

Solidification ofHe4clusters adsorbed on graphene

We determined the ground state of $^{4}\mathrm{He}_{N}$ clusters adsorbed on one side of graphene for selected cluster sizes in the range from $N=20$ to $N=127$. For all investigated clusters variational and diffusion Monte Carlo simulations were performed at $T=0$ K, and in addition for a selected subset finite temperature path integral Monte Carlo. At $T=0$ K the liquid or solid character of each cluster was investigated by restricting the phase using corresponding importance sampling trial-wave functions. The $^{4}\mathrm{He}$-graphene interaction was modeled as a sum of individual $^{4}\mathrm{He}$-C interactions, where both isotropic and anisotropic models were tested; also the effect of the substrate-mediated McLachlan interaction was investigated. We have found homogeneous crystallization in models of anisotropic interactions, starting from clusters with $N=26$ atoms in simulations without the McLachlan interaction, and between $N=37$ and 61 when it is included. The atoms become increasingly delocalized as one moves from the center of the cluster to the perimeter, evidenced by the Lindemann parameter. On the other hand, in the case of the isotropic interaction model, a liquidlike structure is more favorable for all considered cluster sizes. We use a liquid-drop model to extrapolate the energy per particle to the $N\ensuremath{\rightarrow}\ensuremath{\infty}$ limit, and the results are compared with the values obtained in studies of bulk $^{4}\mathrm{He}$ on graphene. Low-temperature path integral Monte Carlo simulations are in agreement with ground-state results.

Effect of functionality on unentangled star polymers at equilibrium and under shear flow.

The properties of unentangled star polymers with arm length Nf = 20 beads and functionality f (3 ≤ f ≤ 60) are investigated at equilibrium and under shear flow by coarse-grained molecular dynamics simulations. At equilibrium, the star polymer shows a crossover from a linear, freely penetrable, extremely soft object to a spherical, slightly hard object with an impenetrable center with increasing f. The results confirm that the arm relaxation is essentially independent of f and stars of large f form a liquid-like structure. In shear flow, the polymer deformation and alignment are calculated as well as the shear-induced rotational dynamics as function of shear rate. These properties are found to exhibit qualitative changes at an f-independent shear rate, γṗ, which is a consequence of competition between chain relaxation and imposed flow. Shear thinning is characterized by shear viscosity and normal stress differences. With increasing f, the critical shear rate for the onset of shear thinning decreases from γṗ for f = 3 to a smaller value. Our results also show that shear thinning of stars of large f arise from the collapse of liquid-like structures at low shear rates (γ̇≪γṗ), where chains have no deformation; at high shear rates (γ̇≫γṗ), shear thinning is mainly attributed to the chain stretching and orientation as linear polymers.

Estimating the surface tension of grain boundaries in pure metals

The surface tension of grain boundaries with liquid-like structure in a pure metal is presented as a function of the melting temperature and the molar volume of the metal in the solid state at the temperature of melting. Several empirical expressions for estimating the average surface tension of high-angle GBs at high homologous temperatures are proposed on this basis.

Particle-directed assembly of semiflexible polymer chains.

We use Langevin dynamics simulations to study aggregation of semiflexible polymers driven by attractions between polymers and spherical particles. We consider a simple model with purely repulsive polymer/polymer and particle/particle interactions but attractive polymer/particle interactions. We find a rich "phase diagram" that contains several different types of globular and rod-like aggregates with either liquid-like or crystalline structure for the particle positions. Systems that exhibit rod-like aggregates with crystalline internal order exhibit a discontinuous rod-globule transition, while systems with liquid-like internal order exhibit a smooth crossover between isotropic and elongated aggregates with increasing chain stiffness. Polymers in elongated liquid-like aggregates often adopt helical configurations that wind around the axis of the aggregate.

Understanding adsorption behavior of silica nanoparticles over a cellulose surface in an aqueous medium

The suspension and adsorption of silica nanoparticles on a cellulose surface, in an aqueous medium is investigated using Brownian dynamic simulations. The inter particle and particle–surface interactions are modeled within the framework of the DLVO theory. Our analysis predicts the accumulation of negatively charged nanoparticles near a negatively charged surface depending on the Debye screening length of the medium. A crossover from the suspension to the adsorption of negatively charged silica nanoparticles onto a negatively charged cellulose surface has been reported as the screening length (k−1) of the medium increases. The crossover is observed at k−1=100nm, due to the interplay between the nanoparticle–nanoparticle and the nanoparticle–surface interactions. The adsorption behavior of nanoparticles is explained using the potential of mean force analysis. The amount of nanoparticles adsorbed depends on their bulk volume fraction (ϕ) and the screening length of the medium. Further, the effects of electrical potentials of nanoparticle (ΨP) and surface (ΨS) on the adsorption are reported. The data suggests that the adsorption of nanoparticles increases either with increasing ΨP magnitude, or/and, with decreasing ΨS magnitude. The adsorbed particles form a disordered monolayer, and undergo subdiffusive motion. We have also observed a transition from the gas-like structure to the liquid-like structure of nanoparticles in the adsorbed monolayer as their bulk volume fraction increases.

Two-Dimensional Ordering of Ionic Liquids Confined by Layered Silicate Plates via Molecular Dynamics Simulation

Recent experiments and computer simulation studies on nanoconfined ionic liquids (ILs) have shifted the focus from perpendicular to lateral distribution, the understanding of which is crucial for IL performance in the field of energy storage systems and tribology. In this article, the structure of 1-ethyl-3-methylimidazolium bromide, [Emim][Br], confined by a hydroxyl group functionalized surface of kaolinite plates has been studied by molecular dynamics simulation. Depending on the degree of confinement, the IL anion can pack into a two-dimensional (2D) ordered structure with square symmetry, coexisting liquid–solid phase, or liquidlike structure. The ordered structure arises from surface-induced ionic orientational preference and the driving force from confinement that supports the formation of the 2D planar structure. The flexible H-bond formed between Br and surface hydroxyl group at fixed d-spacing results in the liquidlike ordering that breaks down the electrostatic network in ILs. The influence of water addition varies when confining plates are treated differently, namely, forming large H-bonding network and small isolated oligomers for relaxed and fixed d-spacing, respectively. This work reveals additional information about the relative importance of factors like packing constraints, interaction within ILs, and selective attraction in determining the structure and dynamics of confined ILs.

Formation and Growth of Clusters of Sulfur Dioxide

Formation and growth of neutral SO2 clusters is investigated in an adiabatic-expansion setup by means of sulfur 2p (S2p) photoelectron spectroscopy and theoretical modeling. The shift in S2p ionization energy between the cluster and a single molecule, i.e., IE(cluster)-IE(monomer), is recorded and used to monitor the mean cluster size over a wide range of expansion conditions. The produced clusters were shown to fall into two different size regimes. Comparison between theoretical simulations and experimental observations suggests that while the smallest clusters belong to the ultrafine particle mode and have a liquid-like structure, the larger clusters belong to the accumulation mode of fine particles and possibly have a frozen cluster core. The transition between the two size/structure regimes occurs over a narrow interval in expansion conditions and may possibly reflect a change in growth mechanism from monomer addition to growth by cluster-cluster collisions.(c) Jarle Harnes, Mahmoud Abu-Samha, Mathias...

Effect of interfacial hydrogen bonds on the structure and dynamics of confined water

Reactive molecular dynamics (MD) is used to simulate the equilibrium process of water confined between two fully hydroxylated α-quartz (001) surfaces with separation distances from 7 to 20 Å. Effect of different patterns of interfacial hydrogen bonds on the structure and dynamics of confined water is investigated. Density profiles, radial distribution functions, number of interfacial hydrogen bonds, and mean square displacements are calculated. The α-quartz (001) surface is cut from an α-quartz crystal at a certain depth to construct a surface with geminal silanols after being fully hydroxylated. The silanol groups on the surface are treated in two different ways in the MD simulations. One of the silanol groups are treated as to be fixed, and the other one is treated as no constraint for the movement of surface silanols. Our results show that different patterns of hydrogen bonds are formed at the interface between SiO2 surface and water. For the fixed silanol surface there is one type of strong hydrogen bonds interacting between the oxygen atoms of water and the hydrogen atoms of surface silanols, leading to the dipole moment of water molecules pointing out from the surface. For the movable silanol surface there are two types of strong hydrogen bonds formed at the interface. One is between the oxygen atoms of water and the hydrogen atoms of surface silanols, and the other is between the oxygen atoms of surface silanols and the hydrogen atoms of water. The number of hydrogen bonds of the first type is much less than those of the second type, leading to the dipole moment of water molecules pointing to the surface. Moreover, the total number of interfacial hydrogen bonds formed on the fixed silanol surfaces is larger than that on the movable silanol surfaces. The density profiles of the confined water indicate the formation of a strong layering of water in the vicinity of the fixed silanol surface, and the water layer is also more ordered with an ice-like structure, as compared with a dense water layer with a liquid-like structure in the case of movable silanol surfaces. Thus the mean square displacements of confined water show that, as compared with interfacial hydrogen bonds formed on the fixed silanol surfaces, the weaker and the lesser interfacial hydrogen bonds formed on the movable silanol surfaces may be responsible for more intense movement of confined water between the movable silanol surfaces. Our simulation suggests that the different pattern of interfacial hydrogen bonds could signifiantly affect the structure and dynamic behaviors of the confined water between two fully hydroxylated silica surfaces.

Preparation of fusion materials based on ionic liquids and cationic gold nanoparticles

Fusion materials based on cationic gold nanoparticles mixed with ionic liquids were prepared. An anion exchange of the surface-capping ligand on the gold nanoparticles from a halogen anion to bis(trifluoromethanesulfonyl)amide (Tf2N) in an aqueous solution afforded nanoparticles showing infinite miscibility with Tf2N-based ionic liquids. The thermal decomposition temperature of the gold nanoparticle was elevated by 100 °C after the anion-exchange process. The ionic liquid-like structure of the surface-capping ligand with Tf2N anions led to a glassy solid material with a densely packed assembly of nanoparticles, in which a portion of nanoparticles formed superlattices. A fusion material of ionic liquid and gold nanoparticles with a gold content as high as 40 wt% was obtained by the co-solvent evaporation method using acetone. The stable dispersion of gold nanoparticles in the fusion materials with a high gold content was confirmed by the clear appearance of the plasmon absorption of gold nanoparticles in an optical microscopic image, as well as in an absorption spectrum. The use of an ionic liquid-based monomer yielded a gold nanoparticle–ionic liquid polymer composite, in which the gold nanoparticles showed a high thermal stability. Gold nanoparticles capped with a simplified ionic liquid-like ligand were prepared, which were incorporated into the fusion materials with ionic liquids at concentrations of up to 40 wt% of inorganic content. The fusion material of gold nanoparticles with an ionic liquid monomer was readily converted into a polymeric composite, in which gold nanoparticles showed high thermal stability.

Thermal loop test to determine structural changes and thermal stability of creamed honey: Rheological characterization

This study was the first attempt to understand if thermal stability of any food product during storage could be determined. In this respect, a novel method, namely, the thermal loop test was used to determine structural changes and thermal stability of creamed honey in this study. The novelty of this method was that thermal stability of a product is tested within a number of thermal cycles over a determined range of temperature. Creamed honey was characterized in terms of physicochemical, thermomechanical and rheological properties. It showed non-Newtonian thixotropic behavior at all temperature levels (10, 25 and 40°C). Time-dependent flow behavior was successfully defined by Weltman and second order structural models. Hysteresis loop area depended on temperature and decreased with increase in temperature. Creamed honey had liquid-like structure, showing that it had more pronounced viscous nature than elastic nature (G″>G′). Temperature sweep tests were conducted to determine temperature dependency of η50, G′ and G″ values using Arrhenius equation. These test results confirmed the thermal stability test results, revealing that thermal loop test can be an accurate method to determine thermal stability of similar food products, as a new information. Relative structural index value (Δ) increased with number of thermal loop, suggesting that creamed honey had low thermal stability and showed a great structural change by the thermal stress applied between 5°C and 50°C. These results suggest that crystallized honey be abstained from large temperature fluctuations to avoid from irreversible changes in rheological characters; thus, to maintain spreadability.

Correlating the Resulting Internal Structures of Lithium-Ion Battery Electrodes to the Prior-to-Coating Suspension Properties

On the way to environmentally friendly and sustainable mobility lithium-ion batteries are in focus of various research works. Fundamental studies regarding the synthesis of new active materials or improvements of other important components, e.g. electrolytes or binders, are providing essential progress towards efficient e-mobility. In addition to all the material based developments, it is indispensable to gain a more detailed understanding of the main leverages which improve the electric and ionic transport processes inside the electrode and cell. One crucial property is the electrode’s inner structure. Since not only the materials but also the production processes have a considerable impact on the electrode structure, knowledge of the relationships between processes and structures is essential for a targeted electrode manufacturing.Electrode’s inner structure is basically predetermined by the chosen components, particularly by their particle size distributions and aggregation status (active material, additives) or molecular weight (binder). In addition, some process steps in the manufacturing chain for lithium-ion battery electrodes, such as dispersing and calendering, show crucial impact on the resulting electrode structure. The process modalities while dispersing the powdery materials in a solvent control the desagglomeration degree of the carbon blacks and thus significantly affect the structure in the subsequently produced electrode. Changes in pore diameter distribution (see figure 1), porosity and tortuosity of the pores can be achieved by a more/less intensive or longer/shorter dispersing of the components in the solvent. To predict these structural alterations it is necessary to learn more about the suspension properties, especially about its structure.Colloidal suspensions are commonly analyzed regarding their rheological characteristics in terms of flow behavior to estimate the properties for further processing steps like coating. In addition, rheological measurements can provide indirect structural information of battery suspensions, for instance concerning the fragmentation degree of the carbon black and the structural changes in the suspension while dispersing. Figure 2 exemplarily depicts the observed differences between suspensions with an aggregated particle-network (solid/gel like: phase angle 0°) to a more liquid-like (phase angle increasing up to 90°) suspension structure. A notable structural decrease can be identified after 45 minutes of dispersing compared to a shorter dispersing time of 10 minutes.The correlation between suspension structure, analyzed via rheological measurements, and the resulting electrode structure, characterized via mercury porosimetry, is in the focus of the presented work. Additional investigations on the interrelations between structures and electric or ionic transport processes as well as electrochemical cell performances provide a basis for targeted electrode manufacturing.

High-Entropy Metallic Glasses

The high-entropy alloys are defined as solid-solution alloys containing five or more than five principal elements in equal or near-equal atomic percent. The concept of high mixing entropy introduces a new way for developing advanced metallic materials with unique physical and mechanical properties that cannot be achieved by the conventional microalloying approach based on only a single base element. The metallic glass (MG) is the metallic alloy rapidly quenched from the liquid state, and at room temperature it still shows an amorphous liquid-like structure. Bulk MGs represent a particular class of amorphous alloys usually with three or more than three components but based on a single principal element such as Zr, Cu, Ce, and Fe. These materials are very attractive for applications because of their excellent mechanical properties such as ultrahigh (near theoretical) strength, wear resistance, and hardness, and physical properties such as soft magnetic properties. In this article, we review the formation and properties of a series of high-mixing-entropy bulk MGs based on multiple major elements. It is found that the strategy and route for development of the high-entropy alloys can be applied to the development of the MGs with excellent glass-forming ability. The high-mixing-entropy bulk MGs are then loosely defined as metallic glassy alloys containing five or more than five elements in equal or near-equal atomic percent, which have relatively high mixing entropy compared with the conventional MGs based on a single principal element. The formation mechanism, especially the role of the mixing entropy in the formation of the high-entropy MGs, is discussed. The unique physical, mechanical, chemical, and biomedical properties of the high-entropy MGs in comparison with the conventional metallic alloys are introduced. We show that the high-mixing-entropy MGs, along the formation idea and strategy of the high-entropy alloys and based on multiple major elements, might provide a novel approach in search for new MG-forming systems with significances in scientific studies and potential applications.

Structure development and acidification kinetics in fermented milk containing oat β-glucan, a yogurt culture and a probiotic strain

The impact of oat β-glucan fortification (1.4%) on the acidification and gelation kinetics of fermented skimmed milk (12% total solids) as well as the effects of inclusion of a probiotic strain (Lactobacillus paracasei subsp. paracasei B117) into the yogurt starter culture (Lactobacillus delbrueckii subsp. bulgaricus Y 6.15 and Streptococcus thermophilus Y 4.10) and fermentation temperature (36, 38 and 40 °C) have been explored by dynamic rheometry, pH measurements and microbial enumeration. The viability/growth of the mixed culture bacteria was also evaluated upon storage. Incorporation of β-glucan to milk resulted in phase separation between proteins and the added polysaccharide, altering the entire gelation process as manifested by the development of a transient gel structure at the early stages, followed by significant (P < 0.05) retardation of both protein aggregation and acidification kinetics, and finally the formation of significantly weaker gels compared to control formulations. Furthermore, fortification of milk with β-glucan led to a liquid-like structure (tan δ > 1) at the end of fermentation (pH = 4.6) when performed at 36 °C. A higher fermentation temperature accelerated the acidification kinetics, yielding a shorter gelation time, but the storage modulus values of milk gels decreased. Inclusion of the probiotic strain into the yogurt starter culture seemed to increase the gelation rate without affecting the gelation time and gel strength. Viability of all three culture bacteria was enhanced by decreasing fermentation temperature and during storage. Moreover, the L. paracasei showed good compatibility with the yogurt starter culture and the addition of β-glucan enhanced the viability of the probiotic strain in the fermented products throughout cold storage (4 °C).