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This study aims to combine, using a numerical tool, different phenomena of hygromechanical coupling in a unidirectional carbon/epoxy composite and to compare the results obtained with the cases where these couplings are considered separately. The first case of coupling considers the effect produced by the mechanical state on the diffusive behavior of the material. This was accomplished using the free volume theory, which links the trace of the matrix strain tensor to the moisture absorption capacity and the diffusion coefficient. The second case takes into account plasticization, that is, the effect of humidity on the mechanical properties of composites, without modifying the diffusion parameters. Finally, these two mechanisms are combined in a third configuration, which represents the original contribution of this present work. The results include the water content profiles, the diffusion coefficient, the transverse Young's modulus, the transverse hygroscopic expansion coefficient, as well as the induced local mechanical states. The interest of the work carried out is to pave the way for the extension to more complex materials, such as plant fiber biocomposites, in which the water absorption by the hydrophilic fibers should not be neglected anymore. [ABSTRACT FROM AUTHOR]

Biochar-based composite phase change materials (PCMs) are gaining popularity in thermal energy storage (TES) applications. Organic PCMs derived from fatty acids are favored for their affordability and variable melting temperatures based on carbon chain length. Understanding the interaction between different carbon-length fatty acid PCMs and porous biochar is crucial for optimizing thermal performance. Thus, this study explored the interaction between PCMs of decanoic acid (DA) and octadecanoic acid (OA) with banana peel (BP) biochar. Experimental results showed that shorter carbon chain of DA enhanced thermal properties and surface compactness compared to OA. BP-DA had higher loading efficiency and PCMs ratio, resulting in superior thermal cycle endurance and latent heat ratio. The molecular dynamics suggest that longer carbon chains affect the mean square displacement (MSD) curves, reducing the self-diffusion coefficients of BP-DA. This is due to DA's high loading rate, which occupies more space within BP biochar structure, thus limiting its diffusion capacity. Enhanced hydrogen bonding constrained DA's thermal motion during phase transition, restricting atom mobility within BP. With temperature elevations, BP-DA exhibits lesser fractional free volume than BP-OA, due to lower molecular mass. This research highlights how carbon chain length influences composite PCMs performance, offering insights for efficient TES system design. [ABSTRACT FROM AUTHOR]

The electrolyte perturbed‐chain statistical associating fluids theory (ePC‐SAFT) coupled with free volume theory (FVT) was combined with Einstein relation, that is, ePC‐SAFT‐FVT‐E, to describe self‐diffusion coefficients (SDCs) of ionic liquids (ILs). In modeling, ePC‐SAFT was used to calculate density, while FVT parameters, determined from viscosity data, were utilized to calculate the summation of ionic SDCs through the Einstein relation with one parameter. Two strategies were employed to determine this parameter: fitting experimental data for each IL or estimating a universal parameter from van der Waals volume. Comparative analysis reveals good agreement with experimental data, with average absolute relative deviations (ARDs) of 8.14% (strategy 1) and 10.29% (strategy 2). Subsequently, cationic and anionic SDCs were reliably determined from the summation of ionic SDCs, with average ARDs of 10.80% and 10.21%, respectively. This study indicates the ePC‐SAFT‐FVT‐E model, employing viscosity‐derived parameters and three universal parameters, reliably predicts SDCs of ILs in wide temperature and pressure ranges. [ABSTRACT FROM AUTHOR]

The water adsorption process by dough films at 20 and 40 ℃ was measured using a dynamic vapor sorption system under nine relative humidity (RH) levels. Water diffusivity was expressed as a function of water content and temperature according to the Vrentas & Duda free volume theory. The parameters of the free volume model were obtained by inversion of water content as a function of time. The results showed that the water diffusion coefficient determined based on the free volume theory could well simulate the water adsorption process by dough films at most water contents tested, but the predicted values were significantly lower than the actual ones at low water contents. Therefore, the Vrentas & Duda was improved by adding a free volume term as a function of water content. As the water content increased, the water diffusion coefficient slightly decreased initially, then increased, and finally increased rapidly. Finally, the mechanism of water diffusion at low water contents was discussed from the perspectives of β-transition and free volume changes.

This paper aims to develop a general form of the time-temperature-ageing shift model for bituminous materials based on free volume theory and validate its application in the Finite Element (FE) modelling for predicting aged asphalt mixtures' mechanical responses. The frequency sweep, dynamic modulus, and Fourier Transform Infrared Spectroscopy (FTIR) tests were used to validate the proposed time-temperature-ageing shift model. A generalised Maxwell model incorporating the proposed shift model of asphalt mixtures was used to predict the mechanical responses of aged asphalt mixtures using FE modelling, verified via laboratory cyclic load tests. Results indicate that the time-temperature-ageing shift function can model the complex shear modulus and dynamic modulus master curves of bituminous materials, addressing the modulus dependency of temperature and ageing. Temperature dominates the modulus change of bituminous materials in the ageing process. The coefficients of the time-temperature-ageing shift model have clear physical meanings and can potentially quantify the effects of asphalt mixtures' air voids on their temperature and ageing susceptibilities. The time-temperature-ageing shift model can be incorporated into the constitutive relations of the FE model to effectively couple and efficiently predict the effects of temperature and ageing on the mechanical responses of aged asphalt mixtures. [ABSTRACT FROM AUTHOR]

Eighteen models based on two equations of state (EoS), three viscosity models, and four mixing rules were constructed to predict the viscosities of natural gases at high temperature and high pressure (HTHP) conditions. For pure substances, the parameters of free volume (FV) and entropy scaling (ES) models were found to scale with molecular weight, which indicates that the ordered behavior of parameters of Peng-Robinson (PR) and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) propagates to the behavior of parameters of viscosity model. Predicting the viscosities of natural gases showed that the FV and ES models respectively combined with MIX4 and MIX2 mixing rules produced the best accuracy. Moreover, the FV models were more accurate for predicting the viscosities of natural gases than ES models at HTHP conditions, while the ES models were superior to PRFT models. The average absolute relative deviations of the best accurate three models, i.e., PC-SAFT-FV-MIX4, tPR-FVMIX4, and PC-SAFT-ES-MIX2, were 5.66%, 6.27%, and 6.50%, respectively, which was available for industrial production. Compared with the existing industrial models (corresponding states theory and LBC), the proposed three models were more accurate for modeling the viscosity of natural gas, including gas condensate. [ABSTRACT FROM AUTHOR]

[Display omitted] The self-diffusion coefficient of active ingredients (AI) in polymeric solid dispersions is one of the essential parameters for the rational formulation design in life sciences. Measuring this parameter for products in their application temperature range can, however, be difficult to realise and time-consuming (due to the slow kinetics of diffusion). The aim of this study is to present a simple and time-saving platform for predicting the AI self-diffusivity in amorphous and semi-crystalline polymers on the basis of a modified version of Vrentas' and Duda's free volume theory (FVT) [A. Mansuri, M. Völkel, T. Feuerbach, J. Winck, A.W.P. Vermeer, W. Hoheisel, M. Thommes, Modified free volume theory for self-diffusion of small molecules in amorphous polymers, Macromolecules. (2023)]. The predictive model discussed in this work requires pure-component properties as its input and covers the approximate temperature range of T < 1.2 T g , the whole compositional range of the binary mixtures (as long as a molecular mixture is present), and the whole crystallinity range of the polymer. In this context, the self-diffusion coefficients of the AIs imidacloprid, indomethacin, and deltamethrin were predicted in polyvinylpyrrolidone, polyvinylpyrrolidone/vinyl acetate, polystyrene, polyethylene, and polypropylene. The results highlight the profound importance of the kinetic fragility of the solid dispersion on the molecular migration; a property which in some cases might entail higher self-diffusion coefficients despite an increase in the molecular weight of the polymer. We interpret this observation within the context of the theory of heterogeneous dynamics in glass-formers [M.D. Ediger, Spatially heterogeneous dynamics in supercooled liquids, Annu. Rev. Phys. Chem. 51 (2000) 99–128] by attributing it to the stronger presence of "fluid-like" mobile regions in fragile polymers offering facilitated routes for the AI diffusion within the dispersion. The modified FVT further allows for identifying the influence of some structural and thermophysical material properties on the translational mobility of AIs in binary dispersions with polymers. In addition, estimates of self-diffusivity in semi-crystalline polymers are provided by further accounting for the tortuosity of the diffusion paths and the chain immobilisation at the interface of the amorphous and crystalline phases. [ABSTRACT FROM AUTHOR]

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Properties as density and dynamic viscosity were measured for four binary mixtures composed for ethylene glycol dimethyl ether + 2-alkanol (2-propanol, 2-butanol, 2-pentanol, and 2-hexanol). The measurements were carried out in the entire mole fraction range of the liquid phase, 0.1 MPa, and using four temperatures (293.15 K, 303.15 K, 313.15 K, and 323.15 K). The values of excess molar volume and deviation in dynamic viscosity were successfully correlated with the Redlich–Kister equation. Strong attractive forces are obtained for all binary mixtures. The perturbed chain-statistical associating fluid theory equation of state (PC-SAFT EoS) correctly modeled the density of binary mixtures. The free volume theory combined with the equation of state was able to modeling the viscosity of all the mixtures. [ABSTRACT FROM AUTHOR]

In this study, the lattice fluid (LF) and Vrentas's self-diffusion (VSD) model were employed to predict the gas sorption, diffusion, and permeability through various rubbery polymeric membranes, like PDMS, PB, PE, and PIP as homopolymers and SBR (36 wt.%) and EVAc (54 wt.%) as copolymers. The LF model with use of variable characteristic parameters that were based on the temperature and pressure range of interest, enabled to predict convex behavior of pressure-induced sorption of PDMS and PB with an AARD < 3%. The Dullien method was also used to calculate the self-diffusion coefficient of pure components in the selected polymers. Extending VSD model led to reliable gas diffusion predictions with AARD < 10% for all systems. Furthermore, using concept of bulk modulus in combination with Tait equation, pressure functionality of diffusion factor was successfully corrected. The pressure and temperature dependency of the gas permeability through the selected homopolymers and copolymers were also investigated by the proposed model, and it was observed that the predicted permeability values were consistent with the experimental data. [ABSTRACT FROM AUTHOR]

Neutron scattering and molecular dynamics are used to unravel the microscopic mechanisms that govern methane diffusion in MFI zeolite (silicalite-1). First, using neutron scattering for silicalite-1 loaded with different methane amounts, we analyze the experimental dynamic structure factor S (q , ω) in terms of molecular rotations and translations. While the rotational diffusion is found to be nearly independent of the zeolite loading, the translational diffusivity drastically decreases with the adsorbed amount. To gain insights into the diffusion mechanisms, trajectories obtained using molecular dynamics simulations are analyzed by determining mean square displacements 〈 Δ r 2 (t) 〉 and incoherent scattering functions F (q , t). We also determine how anisotropy affects diffusion by considering independently the x , y and z directions. While the activation energy for diffusion is found to be weakly dependent on methane loading, the self-diffusivity decreases as the loading increases. Both the experimental and molecular simulation results suggest that steric repulsion between confined molecules – which increases as the loading increases – drastically affects diffusion. Using a free volume theory, we provide a simple formalism to predict consistently diffusion in the internal porous network of MFI zeolite. To demonstrate the applicability of this simple yet robust framework, we show that the free volume theory accurately captures diffusion in each direction of space but also when the size of the adsorbate molecule is arbitrarily increased. • Neutron scattering and molecular dynamics are used to decipher diffusion in zeolite. • Experimental and molecular simulation suggest that steric repulsion drastically affects diffusion. • A free volume theory is derived to predict diffusion in the zeolite porous network. • The free volume theory accurately captures diffusion in each direction of space. [Display omitted] [ABSTRACT FROM AUTHOR]

Natural ester insulating oil not only has a biodegradation rate of almost 100% but also meets the carbon emission requirements of China’s “Carbon Peak and Carbon Neutrality” and the “European Green Deal” proposed by the European Union. It is considered to be a good substitute for mineral insulating oil. However, due to its higher kinematic viscosity than traditional mineral oil in low-temperature environments, it limits the safety promotion and application of transformers in cold regions. First, we design an experiment to test the kinematic viscosity and density of natural ester insulating oil. Under extremely harsh experimental conditions, we measure key experimental data such as kinematic viscosity. Second, the structure of the four main triglyceride molecules is optimized, and the molecular dynamics (MD) simulation technology is used to establish an MD model that can predict the kinematic viscosity of natural ester insulating oil (−20 °C to 20 °C). Finally, the model is further simplified by the free volume theory to better predict the kinematic viscosity of natural ester insulating oil. This study makes up for the lack of laboratory low-temperature testing of the kinematic viscosity of natural ester insulating oil and provides a convenient and reliable tool for predicting the kinematic viscosity of natural ester insulating oil. It can not only predict the natural ester insulating oil mixed in various proportions but also predict the kinematic viscosity of a certain natural ester molecule. Furthermore, it also provides a guiding direction for the improvement of low-temperature kinematic viscosity of natural ester insulating oil, as well as a strong reference for predicting other properties of other substances. [ABSTRACT FROM AUTHOR]

• Novel model integrates Burgers & FV approaches. • Plastic viscosity decreases with temperature, increases with stress rates for the metallic glass. • Relaxation time increases with loading frequency. • Study sheds light on history-dependent behavior for metallic glasses. Establishing the intrinsic correlation between microstructural heterogeneity and mechanical properties is a challenging issue of metallic glasses. The ratchet behavior was examined in a Zr-based metallic glass under cyclic tensile loading well below the yield point, particularly near the glass transition temperature. It is found that strain evolution during cyclic loading shows heightened sensitivity to temperature and stress rate. Also, creep behavior mirrors the ratchet strain induced by cyclic loading. The proposed constitutive model, integrating the Burgers model with defect concentration based on free volume theory, effectively describes strain evolution during cyclic loading near glass transition temperature. Both macroscopic and microscopic perspectives are included in this model. The results verify that metallic glasses exhibit significant viscous characteristics, displaying noticeable creep deformation under low stress rates and amplitudes, which contributes to ratchet behavior. The fitted parameters show that plastic viscosity decreases with temperature and increases with stress rate, corroborating the decrease of tensile yield stress with temperature increasing; also, the fitted relaxation time increases with loading frequency, reflecting evolution of defect concentration. Structural relaxation competes favorably against stress-driven rejuvenation throughout the cyclic process, suggesting potential in tuning metallic glasses properties through innovation thermos-mechanical processing techniques. [ABSTRACT FROM AUTHOR]

The diffusion of small molecules or ions within polymeric materials is critical for their applications, such as polymer electrolytes. Cross-linking has been one of the common strategies to modulate solute diffusivity and a polymer's mechanical properties. However, various studies have shown different effects of cross-linking on altering the solute transports. Here, we utilized coarse-grained molecular dynamics simulation to systematically analyze the effects of cross-linking and polymer rigidity of solute diffusive behaviors. Above the glass transition temperature T g , the solute diffusion followed the Vogel–Tammann–Fulcher (VTF) equation, D = D 0 e − E a / R (T − T 0) . Other than the conventional compensation relation between the activation energy E a and the pre-exponential factor D 0 , we also identified a correlation between E a and Vogel temperature T 0 . We further characterized an empirical relation between T 0 and cross-linking density. Integrating the newly identified correlations among the VTF parameters, we formulated a relation between solute diffusion and the cross-linking density. The combined results proposed the criteria for the optimal solute diffusivity in cross-linked polymers, providing generic guidance for novel polymer electrolyte design. [ABSTRACT FROM AUTHOR]

[Display omitted] • The average calculated error between model estimation and viscosity experimental data for pure ILs has been obtained 5.27%. • The mixture viscosity of IL-IL and IL-solvent has been correlated using the Eyring theory coupled with the SAFT-VR Morse model. • The viscosity deviation of the IL-IL mixture has been predicted at different temperatures. This work aims to calculate the viscosities of ionic liquid mixtures using the Eyring theory combined with the SAFT-VR Morse EOS. The free volume theory was used to correlate the pure viscosity of ionic liquids (ILs) and solvents. Three model parameters have been adjusted using experimental viscosity data of ILs between 282 K and 413 K and 1 bar to 350 bar. The average ARD%, Bias%, and rmsd between model estimation and viscosity experimental data for pure ILs have been obtained 4.9 %, 1.015 %, and 0.67, respectively. The average error of the proposed model tends to increase at a pressure higher than 200 bar. The average ARD% for [C 2 mim][Tf 2 N] and [C 6 mim][Tf 2 N] is about 3.8 % and 3.4 % at pressures lower than 200 bar, while the average ARD% values increase sharply at higher pressures. This is due to the weak performance of the SAFT-VR Morse EOS for the calculation of IL density at high pressures. The SAFT-VR Morse EOS has been coupled with the Eyring theory, and the Redlich-Kister mixing rule to estimate the mixture viscosity of ILs-ILs and ILs-solvent systems. The thermal contribution of excess activation free energy has been calculated using the Redlich-Kister mixing rule with four adjustable parameters. The average ARD%, rmsd, and Bias% for fifteen binary mixtures have been obtained 3.9 %, 2.51, and 0.57 %, respectively. The average error values for mixture viscosity of ILs-polar solvent are higher than non-polar solvents. In the case of binary IL-IL systems, the model results are in good agreement with experimental data. The model performance has been evaluated using the viscosity deviation property. The SAFT-VR Morse EOS predicts the negative viscosity deviation. The strong attractive interaction in the mixture than a pure component is the major contribution to negative viscosity deviation. The results show that the new model can calculate the mixture viscosity and viscosity deviation of binary systems satisfactory. The obtained error values of mixture viscosity show that the Eyring theory can be coupled with a SAFT-based EOS to calculate the viscosity of ILs over a wide range of pressures and temperatures satisfactory. [ABSTRACT FROM AUTHOR]

The structure of liquid bismuth was studied by X-ray diffraction and computer simulation methods. The contraction of the atomic structure within the first coordination sphere in the temperature interval of 575-1225 K is reported. The temperature dependencies of the coordination numbers and of the free volume are analysed. On the basis of the temperature dependencies of the free volume, the temperature dependencies of viscosity and the self-diffusion coefficient were calculated to be in the ranges from 1.17 to 0.86 mPa s and from 2.18 × 10−9 to 5.44 × 10−9 m2/s, respectively. The free volume – extracted results are in fair agreement with the experimental data and with the results obtained in the molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Decreased viscosity due to the influence of blowing agent in thermoplastic polymer melts is a key issue for understanding the process of foam extrusion. In a process for direct foam extrusion, a novel approach for inline viscosity measurement of single-phase systems in single screw extruders is used to experimentally evaluate a viscosity decrease. Two blowing agents (propane and carbon dioxide) are tested for their effect on the viscosity of a polypropylene melt. While mass fractions of blowing agent below 2 w % show little to no effect in regard to viscosity reduction compared to a pure polymer melt, a mass fraction of 3.5 w % already results in significantly decreased viscosity values. While melt temperature influences the viscosity of the polymer melt, measurements show no significant additional effect in regard to a lowered viscosity of a single-phase system of polymer and fully dissolved blowing agent. [ABSTRACT FROM AUTHOR]

In this study experimental densities and viscosities, at temperatures to 530 K and pressures to 70 MPa, are reported for mixtures of toluene +11.3 mol% and 32.4 mol% ethylene and for mixtures of toluene +7.9 mol% and 30.7 mol% propylene. Both densities and viscosities are measured simultaneously using a variable-volume, rolling ball viscometer/densimeter apparatus. Mixture viscosities decrease as the ethylene or propylene mole fraction increases. The expanded experimental uncertainties in the reported viscosities and densities, both at 95% confidence level, are estimated to be 4.0% and 0.8%, respectively. Mixture viscosities and densities are fit to Tait-like expressions, with temperature-dependent parameters, to provide a facile method for data interpolation. The Perturbed Chain, Statistical Associating Fluid Theory equation of state (PC-SAFT EoS) is used to predict mixture densities to within 3.0% using literature values for the PC-SAFT pure component parameters from fitting both vapor pressure and saturated liquid densities. The Free Volume Theory model, with PC-SAFT calculated densities as input, reproduces the viscosities for the four different mixtures with maximum deviations of 13.5% and 15.4% for ethylene + toluene and propylene + toluene mixtures, respectively. [ABSTRACT FROM AUTHOR]

• A unified model for drying of glassy polymer coatings. • This model is based on sound non equilibrium thermodynamics principles. • Sol-Gel transition is considered. In this work, a unified model has been developed for the drying of the glassy polymeric coatings by studying the solvent evaporation from the poly(methyl methacrylate)/ethyl benzene system as a one dimensional numerical moving boundary experiment with simultaneous heat and mass transfer. The developed model is based on sound non equilibrium thermodynamics principles by considering visco-elastic contribution to diffusion at the late stage of drying. Moreover, sol-gel transition is considered to explain the high solvent concentration far away from the gas-liquid interface (drying surface) at the end of the drying experiment. The Galerkin finite element method is used to solve the model equations. The model predictions for the drying rate and solvent concentration profiles are found to be in satisfactory agreement with the available experimental data. This work can be implemented to design and optimize industrial processes. [ABSTRACT FROM AUTHOR]

We carry out extensive computer simulations to study the phase equilibrium, thermodynamics, and diffusion coefficient of three-center Lennard-Jones (3CLJ) fluids with an emphasis on the effects of bond angle on these properties. We take into account several bond angles ranging from θ0 = 60 to 180 degrees and two equilibrium bond elongations le = 1.0 and 0.5 (in Lennard-Jones length unit). Moreover, we study the fully flexible (FF) 3CLJ fluids for molecules with bond length 1.0. Gibbs ensemble Monte Carlo (MC) simulations are performed to compute the densities of the vapor-liquid coexisting phases and the vapor pressure, and direct three-phase (vapor-liquid-vapor) molecular dynamics (MD) simulations are carried out to calculate the surface tension. We then apply constant NVT MC simulations to obtain the internal energy, the pressure, and the pair correlation function, and utilize equilibrium MD simulations to compute the diffusion coefficient of systems with le = 1.0. In addition to MD simulations, the modified Cohen-Turnbull (mCT) theory is used to to compute the diffusion coefficient and the mean free volume appearing in the mCT relation is provided by the results of the Generic van der Waals (GvdW) theory. We show that the mCT theory is capable of reproducing the MD simulation values quite well over a wide range of density with slight overestimations at medium range. The angle dependence of different thermophysical properties are analyzed and discussed in details. [ABSTRACT FROM AUTHOR]

• New experimental density and dynamic viscosity for diethylene glycol diethyl ether + 2-alkanol mixtures in the temperature range of 293.15 K to 323.15 K. • Perturbed chain-statistical associating fluid theory equation of state was used for modeling the density. • Free volume theory coupled to perturbed chain-statistical associating fluid theory equation of state was used to modeling the viscosity of pure fluids and mixtures. • Redlich-Kister correlation was used to model the excess volume and the deviation in viscosity. • Attraction forces for DEGDEE + 2-propanol and DEGDEE + 2-butanol mixtures, and weak forces for DEGDEE + 2-pentanol and DEGDEE + 2-hexanol mixtures were obtained. Experimental density and dynamic viscosity data for the diethylene glycol diethyl ether +2-alkanol (C3 to C6) mixtures have been published at 293.15 K, 303.15 K, 313.15 K, and 323.15 K and at pressure of 0.1 MPa. Excess molar volume and deviation in dynamic viscosity were obtained from experimental data and correlated with Redlich–Kister equation, from the values obtained, the interaction forces were studied. Perturbed chain-statistical associating fluid theory equation of state was used for modeling the density for pure fluids and mixtures. Free volume theory coupled to Perturbed chain-statistical associating fluid theory equation of state was used to modeling the viscosity of pure fluids and mixtures; in the case of binary mixtures, we proposed a simple mixing rule and used the Pourabadeh et al. mixing rule. Good results in the prediction and correlation of experimental liquid density and dynamic viscosity for binary mixtures were obtained, 0.12% and 2.28%, respectively. [ABSTRACT FROM AUTHOR]

• Diatomaceous earth/octadecanoic acid composite is fabricated by vacuum impregnation. • DEOA-4 exhibited better thermal properties, stability, and chemical compatibility. • High fraction PCMs show less fractional free volume of DE. • Increase loading ratio of OA revealed a decrease in self-diffusion coefficient. • A proper loading ratio can enhance pore-filling process and thermal performances. To promote diatomaceous earth (DE)-based phase change composite as green energy building materials, this paper bridges the studies of experimental and molecular dynamics (MD) focusing on the absorption effect of phase change materials (PCMs). Octadecanoic acid (OA) was selected as PCMs and DE as supporting material for the fabrication of composite PCMs at different loading ratios; effect on thermal properties and porosity of the composite PCMs were further investigated by MD simulation. In consonance with ATR-FTIR and XRD analyses, the highest loading ratio (DEOA-4) was proven to absorb a high amount of PCMs, with excellent thermal stability and chemical compatibility. DEOA-4 exhibited higher latent heat storage capacity of 52.67 J/g, with a loading ratio and loading efficiency of 32.13 and 32.98 %. Besides, MD simulation showed that increasing the OA loading would decrease the fractional free volume of DEOA models, resulting in a limited mobility of PCMs molecules, as confirmed by self-diffusion coefficient at room and melting temperatures. Experimental and computational studies revealed that pore-filling process plays an imperative role during PCMs absorption. An adequate amount of loading ratio can potentially enhance the pore-filling process, maximize the efficiency of the performances, and promote the development of green energy in concrete structures. [ABSTRACT FROM AUTHOR]

We present a theory that predicts the phase behavior of hard spheres (HS) mixed with non-adsorbing supramolecular polymers in a common solvent. It combines Generalized Free Volume Theory with a mean-field model for equilibrium polymers in solution extended with scaling theory to incorporate excluded volume effects in a good solvent. The system displays similar phase stability as conventional HS-polymer mixtures, although there is a small preference for gas–liquid coexistence with respect to fluid–crystal equilibrium in the case of a HS-supramolecular polymer mixture. Phase transitions can be induced by external stimuli such as temperature or light due to the stimuli-responsive nature of the supramolecular polymer size. [ABSTRACT FROM AUTHOR]

Gas membrane separation process is highly unpredictable due to interacting non-ideal factors, such as composition/pressure-dependent permeabilities and real gas behavior. Although molecular dynamic (MD) simulation can mimic those complex effects, it cannot precisely predict bulk properties due to scale limitations of calculation algorithm. This work proposes a method for modeling a membrane separation process for volatile organic compounds by combining the MD simulation with the free volume theory. This method can avoid the scale-up problems of the MD method and accurately simulate the performance of membranes. Small scale MD simulation and pure gas permeation data are employed to correlate pressure-irrelevant parameters for the free volume theory; by this approach, the microscopic effects can be directly linked to bulk properties (non-ideal permeability), instead of being fitted by a statistical approach. A lab-scale hollow fiber membrane module was prepared for the model validation and evaluation. The comparison of model predictions with experimental results shows that the deviations of product purity are reduced from 10% to less than 1%, and the deviations of the permeate and residue flow rates are significantly reduced from 40% to 4%, indicating the reliability of the model. The proposed method provides an efficient tool for process engineering to simulate the membrane recovery process. [ABSTRACT FROM AUTHOR]

In the light of many mysterious and contradictory claims and explanations on our universe, an alternative new theory focusing on free space and associated energy is proposed to explore the inflation and gravity, on the basis of the very successful free volume theory applicable to wide length scales from electrons to small molecules, macromolecules, colloidal particles and even granules. Hypothetical particles dubbed "freevons" of very high frequency and energy are proposed to fill up the free volume available in any system from microscopic atomic world to the macroscopic universe. The Eyring's rate process theory that is originated from quantum mechanics and has a wide applicability to many chemical and physical processes is assumed to govern the behavior of freevons. It turns out that for keeping the universe to expand in an accelerated manner, the freevons must form the paired structures, very similar to electrons paired in superconductivity state and helium-3 atoms paired in a superfluidity state. Our theory predicts that there should be a temperature induced phase transition at about 5K and the Hubble's constant should dramatically increase at this critical point, implying that the universe will inflate even further rapidly. The universe is therefore viewed as particles, stars, and galaxies, dispersed in a superfluidity freevon sea and the gravity would be induced from the force density, usually defined as a negative gradient of pressure in fluid mechanics. The Newton's gravity equation is thus easily obtained under these assumptions, and similarly the Coulomb's Law can also be obtained using the same approach. In this superfluidity freevon framework, the volumes rather than the masses of particles are found to be important in determining the gravitational forces. The inflation driving force comes from the activity or concentration gradient of freevons formed possibly at the beginning of the big bang. Our approach may bridge various theories in astrophysics fields. [ABSTRACT FROM AUTHOR]

• Large-scale plasticity was frequently achieved in different notched samples, and the maximum plasticity was found to be 18.3%. • There is a transition from brittle fracture to large plastic stability: the stress triaxiality driven SSB stage, and the V-shaped DSBs controlled stage. • It proved that such plasticity improvement stemmed from different notch configurations. • It demonstrated that thickness has a slight influence on plasticity of notched samples. • Notch parameters and geometry configurations could work as the basis parameters for designing porous metallic glasses with high ductility. Systematical experiments, simulations and microscopic characterizations on double edge notched samples manifested a transition from brittle instability to steady plasticity. Effects of ligament length, geometrical notch parameters as well as thickness were studied. It was found that ligament length is essentially the space provider for intersection of shear bands. With a narrow ligament, it is unlikely to form V-shaped double shear bands because of the limited region between notch tips. Meanwhile, the plastic deformation ability is determined by stress triaxiality. With a wider ligament, V-shaped double shear bands become predominant in controlling deformation stability, accompanying with much higher plasticity than previous investigations because of large-regions of shear band entanglements. Such plasticity enhancement is proven to have weak linkage with the restriction of crosshead of machines, and it is the resultant response of notch configuration. Besides, thickness is less influential to global plasticity. On another hand, by means of hydrostatic stress embedded free volume model, shear banding process is simulated by FEM model, by which the shear band evolution patterns in tests could be well understood and explained. The current findings could further enrich the plastic stability mechanism of metallic glasses under complex stress states. As well, those parameters on notch configurations could provide the state-of-the-art parameters used for fabrication of porous metallic glasses. [ABSTRACT FROM AUTHOR]

Asphalt rejuvenation technology is an effective method to recycle reclaimed asphalt pavement (RAP) for the production of high-quality recycled asphalt mixtures. This approach contributes to mitigating environmental pollution and facilitating resource recycling. In this study, the impact of rejuvenator molecules on the rejuvenation process was explored by utilizing theoretical models and dynamics simulations. Free volume theory models were used to calculate the diffusion coefficient, while molecular dynamics (MD) simulations revealed the internal energy changes during diffusion. Molecules with high interaction with aged asphalt are easier to reach the homogeneous state in diffusion systems under higher temperatures. The quantification of blending by Fick's 2nd law suggests that the blending process consists of three stages: an intense diffusion phase, a stabilization phase, and a homogeneous state phase. The time taken to reach the homogeneous stage depends on the chemical structure of the rejuvenators and the temperature. This study elucidates the molecular-scale mechanism of RAP rejuvenation and provides a roadmap for improving environmentally friendly RAP rejuvenation technology. • Blending process consists of three phases. • Interactions and free volume control the diffusion process. • Saturated-based molecules is more susceptible to high-temperature excitation. [ABSTRACT FROM AUTHOR]

In this study, both theoretical and empirical viscosity models were evaluated for binary associating liquid mixtures of water + 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol. The interaction between molecules in the mixtures was analyzed using the calculation of excess energy of flow obtained from Eyring's absolute rate theory. Free volume (FV) viscosity model was coupled with Peng-Robinson (PR) and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of states (EoS); friction theory (FT) was coupled with PR EoS; no significant difference was observed in the modeling results using different EoS. A new mixing rule was found to improve the modeling results of FT coupled with the PR EoS for the binary mixtures studied. The empirical models correlated viscosity of aqueous diol systems well with average absolute percent deviation (AAD%) < 1. [ABSTRACT FROM AUTHOR]

Toluene viscosities and densities, measured with a windowed, variable-volume, rolling-ball viscometer/densimeter (RBVD), are reported at temperatures from 296–535 K and pressures to 300 MPa. The combined expanded uncertainty in the reported viscosities and densities are 4.0% and 0.8% of the measured values respectively, each with a coverage factor, k = 2. Densities obtained with the RBVD exhibit an average absolute percent deviation (Δ AAD ) of 0.20% against densities calculated with the Lemmon and Span Equation of State. Viscosities obtained with the RBVD exhibit Δ AAD values of less than 4.0% for data from 18 of 20 available literature sources for high pressure data. The reported viscosities are generally in good agreement with calculated viscosities from the reference equation of Avgeri et al. The reported toluene viscosities extend the available database from 423–535 K and 40–300 MPa. Toluene viscosities are also reasonably correlated with the empirical Tait equation that allows for reliable interpolation of the data. Free Volume Theory (FVT) matches the reported viscosities to within 3.4% Δ AAD using FVT parameters fit to a viscosity data set limited to 373 K and using densities calculated with the Perturbed–Chain Statistical Association Fluid Theory (PC-SAFT). An improved fit of the viscosity data is obtained if temperature-dependent, FVT parameters are used. The challenge remains to predict the temperature dependence in the FVT parameters from first principles. [ABSTRACT FROM AUTHOR]

In this feature article, we first make some simple reviews about the most popular theories for glass transition: 1) Free volume theory, 2) Entropy theory, 3) Götze’s Mode coupling theory, and 4) Caging and Jamming theory. We address the issue of existing studies of glass transformations. Then, we review some special colloidal/polymer model systems which can give a repulsive potential together with an attractive potential and also large enough and slow enough, so we can study the structure (through microscopy and scattering techniques) and dynamics (mainly through rheology) changes as a function of temperature and volume fraction. We hope, this paper, with the study to explore the structural and dynamics along the path toward the equilibrium, can provide some information, stimulation, incentive, and guidance for future theoretical and experimental studies for glass transition of structural materials, especially for polymers, colloids and colloid/polymer systems. [ABSTRACT FROM AUTHOR]

This review paper deals the history and development of various theories to predict the diffusion in polymeric systems. The basis and application of various theories with the prediction capabilities are discussed. The most commonly used theory is Vrentas and Duda free volume theory with excellent agreement with experimental data report so far. This theory predicts the data very accurately in rubbery region. However, few modifications have come up in this theory to predict the diffusion above the glass transition with a little success. [ABSTRACT FROM AUTHOR]

Gradient of free volume distribution in metallic glasses is omnipresent either naturally or artificially in synthesis and application. But how the spatial inhomogeneity affects mechanical properties remains poorly understood. Here we probe this issue using finite element modeling. We find that the strength and toughness improves with increasing gradient; and the larger the gradient, the more effective. But the plasticity is marginally enhanced or even decreases. Too high the gradient value leads to brittle fracture caused by abrupt release of the large stress concentrated at the gradient region. The effects are represented in their relations with the gradient energy coefficient. [ABSTRACT FROM AUTHOR]

As a popular thermodynamic calculation method for binary alloys, Miedema's model has been applied in many fields. Chou's Model, a new generation of geometric model for ternary and multicomponent alloy systems, overcomes the intrinsic theoretical defects (including symmetric and asymmetric) existing in some original geometric models. Here, by means of combining Miedema's model and Chou's model as well as including the consideration of the excess entropy we attempted to build the new thermodynamic model to evaluate thermodynamic properties of ternary and multicomponent alloying systems in terms of the physical parameters (molar volume, electronegativity, electronic density and melting point) of constituents. Moreover, the activity and interaction coefficients of a wide of components in iron melt have been discussed in details.

Poly (vinyl acetate) (PVAc) is a polymer used in various industrial applications, and the quantitative determination of CO 2 solubility and diffusion coefficient is important for designing foaming processes involving supercritical CO 2. In this study, these two physical properties were obtained experimentally and theoretically using the perturbed chain–statistical associating fluid theory (PC–SAFT) and free volume theory at temperatures between 353 K and 473 K and pressures up to 20 MPa. CO 2 solubility increased almost linearly with pressure and could be correlated with the PC–SAFT equation of state and binary interaction parameter k ij within the average relative deviation of 2.1%. Furthermore, the fitted plot of k ij versus temperature can be used to predict CO 2 solubility at lower temperatures. The diffusion coefficient of CO 2 in PVAc was experimentally determined from CO 2 sorption curves. Its value increased with increasing CO 2 solubility and temperature, which was consistent with the free volume theory. [Display omitted] • Solubility and diffusivity of CO 2 in poly(vinyl acetate) (PVAc) were studied. • Temperatures of 353–473 K and pressures of 5–20 MPa were employed. • Perturbed-chain statistical associating fluid theory (PC-SAFT) helped in modeling solubility. • Diffusion coefficient of CO 2 in PVAc was modeled using the free volume theory. [ABSTRACT FROM AUTHOR]