Effect Of Intermolecular Forces Research Articles

The Effects of Short-Range Intermolecular Repulsive Forces on Hamaker Constant Estimation Using Atomic Force Microscopy.

The atomic force microscope (AFM), as it is able to characterize surface topography as well determine the AFM cantilever tip-surface force, proves effective at estimating the value of the Hamaker constant, A, for a given solid material. Two main AFM-based methods have been proposed for estimating values of A. In the approach-to-contact (AtC) method, Hamaker constants are inferred from the deflections at which the AFM tip first jumps into contact with the substrate. In the pull-off (PO) method, the deflections that arise when the AFM tip is finally pulled away from the substrate are used to estimate values of A. In prior applications of these two methods, the short-range intermolecular repulsive forces that are known to arise between the AFM tip and the substrate were, however, ignored. Upon invoking a physically relevant description of these short-range and steeply repulsive forces, we investigate the effects of repulsive interactions on the values of A estimated from the existing AtC and PO methods when applied to neutrally charged systems under low humidity or vacuum conditions. For experimentally relevant surfaces, we find that repulsive forces have a modest effect on the AtC method, although they still need to be accounted for in order to generate improved estimates of the Hamaker constant. On the other hand, repulsive forces have a significant effect on the Hamaker constants inferred from the PO method, and must be properly accounted for when using this approach. Our analysis also includes an explicit incorporation of surface roughness into the PO method, which is not typically done in most prior applications of the PO method.

Mechanochromism of π-conjugated borate derivatives and the effect of intermolecular non-covalent forces on molecular packing and mechanochromic property

We prepared three π-conjugated pinacol borate derivatives anthryl dioxaborolane (ANB), pyrenyl dioxaborolane (PYB) and perylenyl dioxaborolane (PEB) based on anthracene, pyrene and perylene moieties, and studied their optical properties in solid and solution. Interestingly, the three molecules were structurally similar, yet exhibited different optical properties and mechanochromic behavior. Crystal structure studies showed that the mechanical fluorescent response of ANB, PYB and PEB were closely related to the molecular packing modes. Although there were multiple π-π and σ-π interactions in all three molecules, the conjugation degree of ANB was relatively low, resulting in a weak π-π interaction. Therefore, the effective partial parallel packing between adjacent ANB could not form in the initial state, and external mechanical stimulation could not induce the change of optical properties. In PYB and PEB molecules with a high conjugation degree, the π-π interaction was stronger. A partial parallel packing state was formed between the molecules under the synergistic action of π-π and σ-π interaction. Under external disturbance, the relative slippage between molecules was easy to occur. Thus, the characteristic static excimer fluorescence was displayed due to the enhancement of parallel packing. Since the intermolecular interactions of PYB and PEB were a kind of weak non-covalent forces, the packing state changed by external force could return to the initial state at room temperature, showing reversible mechanochromic characteristic. This kind of room temperature reversible force sensitive material constructed by weak non-covalent interactions was expected to be applied and popularized in the fields of encrypted communication and anti-counterfeiting display.

Analysis of nonlinear bending behavior of nano-switches considering surface effects

Nano-switch structures are important control elements in nanoelectromechanical systems and have potential applications in future nanodevices. This paper analyzes the effects of surface effects, geometric nonlinearity, electrostatic forces, and intermolecular forces on the nonlinear bending behavior and adhesion stability of nano-switches. Based on the Von Karman geometric nonlinearity theory, four types of boundary conditions for the nano-switch structure were specifically calculated. The results show that surface effects have a significant impact on the nonlinear bending and adhesion stability of nano-switches. Surface effects increase the adhesion voltage of the nano-switch and decrease its adhesion displacement, and as the size of the nano-switch structure increases, the impact of surface effects decreases. A comparative analysis of the linear theory and the nonlinear theory results shows that the adhesion voltage predicted by the linear theory is smaller than that predicted by the nonlinear theory. The effect of geometric nonlinearity increases as the size of the nano-switch structure increases, as the distance between the electrodes increases, and as the aspect ratio of the nano-switch structure increases. These findings provide theoretical support and reference for the design and use of future nanodevices and nanoelectromechanical systems.

Effects of particle properties, intermolecular forces, and molecular structure on the shear-thickening behavior of waxy starch dispersions

The shear-thickening phenomenon in waxy starch dispersions has been reported; however, the influence of starch properties on it remains unclear. Herein, the shear-thickening behavior of five waxy starch dispersions at different concentrations is investigated, and two shear-thickening areas are identified for the first time. Waxy potato and cassava starch dispersions present two shear-thickening areas, waxy maize and wheat starch dispersions exhibit one shear-thickening area, and waxy rice starch dispersion exhibits no shear-thickening behavior. Starches with high degree of polymerization (DP > 12 and > 37 chains), short-range order, relative crystallinity, melting enthalpy (ΔH), and low molecular weight easily form large particle fragments and strong intermolecular forces, thereby resulting in double shear-thickening areas. Starches with relatively high DP > 12 chains, short-range order, relative crystallinity, and ΔH form one shear-thickening area. Starches with no shear-thickening area have high molecular weight, degree of branching, and DP < 12 chains, and low short-range order, relative crystallinity, and ΔH. It can be speculated that the first shear-thickening area (2–5 s−1) is due to the presence of large particle fragments, whereas the second (10–15 s−1) is due to the interaction between the side chains of the starch molecule.

Intermolecular forces and surface stress residual effects on the size-dependent performance analysis of nanocrystalline micro/nano gyroscopes

This work investigates an electrostatically-actuated vibrating beam micro/nano-gyroscope made of nanocrystalline silicon material. The comprehensive size-dependent micro/nanogyroscope model is developed by couple stress and surface elasticity theories. Then, considering the effects of intermolecular forces (Casimir force and van der Waals force) and surface stress residual, an in-depth investigation was conducted on the performance of the micro/nanogyroscope. The calculation results display that the maximum static deflection, pull-in voltage and natural frequency change obviously with the increase of surface stress residual as the scale varies from micrometer to nanoscale. However, the effect of intermolecular forces on the performance of gyroscopes is exactly the opposite, which improves the prediction of system structural softening deformation phenomenon. Considering the influence of the Casimir and van der Waals forces in micro/nano gyroscopic system will help gyroscopes to obtain reliability and functionality sensitivity, increase the accuracy of predicting static deformation, natural frequency and differential frequency. Moreover, a frequency-domain method using the difference between the two vibration natural frequencies is studied, with changing the scale of the gyroscope under the effect of the intermolecular forces. The numerical simulations exhibit that when considering smaller structure sizes of the gyroscope, strong coupling occurs between the intermolecular forces and surface stress residual, which is helpful for the design of micro/nano gyroscopes.

Molecular dynamics investigation on the interfacial thermal resistance between annealed pyrolytic graphite and copper.

Modern highly integrated microelectronic products often face the challenge of internal heat dissipation, leading to a significant decrease in their operational efficiency. Annealed Pyrolytic Graphite (APG), due to its superior thermal conductivity, has garnered attention from researchers. The interface thermal resistance between APG and supporting materials like copper significantly affects heat transfer during APG's operation. Existing studies rarely delve into the influence of factors such as the shape of APG material interfaces on thermal resistance from a microscopic perspective. In this paper, utilizing transient thermo-reflectance method and non-equilibrium molecular dynamics simulations, the interface thermal resistance of the APG-Cu structure was investigated under different conditions. The impact of parameters such as copper thickness, interface micro-surface morphology, and APG thickness on the calculated interface thermal resistance was examined. Simulation results revealed that copper thickness had a minor effect on the interface thermal resistance. This is because the phonon participation ratio remains unaffected by changes in the thickness of the copper layer. The interfacial thermal resistance beneath microscopically cylindrical copper surfaces was considerably lower than that of rectangular copper surfaces. This is because beneath the cylindrical surface, the enlarged interface contact area facilitates enhanced thermal transport between the interfaces. The computed results of the radial distribution function in the paper also indirectly validate this viewpoint. The magnitude of interfacial thermal resistance for different APG layers was influenced by the coupling effect of intermolecular forces and the layered stacking structure of APG. The interfacial thermal resistance under the condition of three layers of APG reaches its minimum value, which is 2.2 × 10-9 (K m2 W-1). Furthermore, from the phonon perspective, it is found that the interfacial thermal resistance with different numbers of APG layers is closely related to the localization or delocalization state of phonons. As the number of APG layers increased, the interface thermal resistance showed a trend of initial decrease followed by an increase, this is because the average phonon participation ratio increases and then decreases with the number of APG layers. The average phonon participation ratio reaches its maximum value of 0.45778 under the condition of three layers of APG.

Rimming flow in a rotating horizontal cylinder with phase change at the interface

The two-dimensional solutions and stability analysis are presented for an evaporating thin viscous liquid film flowing inside a uniformly heated rotating horizontal cylinder. A non-linear, fourth-order, partial differential evolution equation is obtained by simplifying mass, momentum, and energy conservation equations within the lubrication approximation. The effect of evaporation, gravity, viscous drag, surface tension, thermocapillary stress, and intermolecular forces has been taken into account. The numerical solutions of the model are validated against the existing experimental as well as the numerical results, along with the analytical result for the limiting cases of the present model. The film thickness model is solved to elucidate two-dimensional spatiotemporal solutions and their stability for a wide range of thermal and other parameters. The evaporative mass flux at the liquid–air interface results in unsteady solutions which are oscillatory in nature, and the amplitude of the oscillations increases with an increase in the evaporative flux. The film ruptures after some time and the rupture time is found to be inversely proportional to the evaporation number, a non-dimensional number quantifying the rate of evaporation. The linear stability analysis shows that the thermocapillary stresses as well as the long-range molecular forces destabilize the film. A negative disjoining pressure is shown to reduce the rupture time and vice versa. Evaporation (condensation) plays a destabilizing (stabilizing) role in the thin film flow. Non-linear computations are carried out for the steady profiles, validating the growth rates obtained from the linear stability analysis.

Effect of flexoelectricity on the Pull-in instability of beam-type NEMS

Considering the increasing number of smart materials in advanced industries and technologies, the need to investigate the use of these materials is felt more and more. The flexoelectric effect is one of the most important phenomena created in micro-scale beams, which will have a significant effect on the results and should be investigated. Therefore, in this article, the Pull-in instability in the beam-type microelectromechanical systems has been investigated under the flexoelectric effect. The governing equations of the system have been derived based on the theory that is founded on the strain gradient theory for the Euler-Bernoulli beam model. This beam is under the effect of intermolecular Casimir force and electrostatic force. The equations and boundary conditions related to them have been non-dimensionalized first in direct and indirect flexoelectric effect. With the help of the differential quadrature method, the Pull-in voltage's critical parameters and the system's free-standing behavior have been studied. Among the significant results obtained from this research, it is possible to mention the Pull-in voltage increase due to the flexoelectric effect reduction. Also, in the indirect state of the flexoelectric effect, the increase in the initial applied voltage causes a decrease in the Pull-in voltage.

Performance of a transverse ridge located through the contact zone of an ultra-thin film including surface force effect

PurposeThe purpose of this paper is to investigate the performance of an ultra-thin film lubricated conjunction through the elastohydrodynamic lubrication of point contacts for various ridge shapes and sizes located within the contact zone including flat-top, triangle and cosine wave profiles, considering the influence of surface forces of solvation and Van der Waals’ in addition to the hydrodynamic effect to predict an optimum geometric characteristics for surface texture for lubricated conjunctions.Design/methodology/approachSurface features are simulated in a variety of sizes and shapes including flat-top, triangle and cosine wave profiles. While estimating the elastic deformation of the contacting surfaces, surface forces of solvation and Van der Waals’ are taken into account. The Reynolds equation is solved using the Newton–Raphson method to get the pressure profile and film thickness including the elastic deformation, and surface feature.FindingsThe geometrical characteristics of the ridge, its placement in relation to the contact zone and its height all have a significant impact on the performance of ultra-thin film lubricated conjunction. When the triangular-shaped ridge is present in contact, it forecasts even sharper peaks in film thickness and pressure. More friction, wear and eventually contact fatigue are brought on by this more acute pressure and film thickness peaks. The flat-top ridge shape shows a better performance for lubricated conjunction where, the minimum film thickness value is comparable to that obtained for the case of a smooth contact surface. This behavior is attributed to the effect of intermolecular force of solvation. An increase in the size of the ridge results in a step increase in the film thickness for different ridge shapes, particularly for the flat-topped ridge pattern.Originality/valueEvaluation of the performance of elastohydrodynamic lubricated ultra-thin film conjunction related to film thickness and pressure profile for various ridge surface features of different amplitudes, shapes and sizes located through the contact zone considering the influence of surface forces of solvation and Van der Waals’ in addition to the hydrodynamic effect.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2023-0062/

Modelling the reaction kinetics of β-lactoglobulin and κ-casein heat-induced interactions in skim milk

Levels of native beta-lactoglobulin (β-lg) in heat-treated milk are often used as a measure of quality deterioration. Most kinetic studies to date on β-lg denaturation have been simplified to a single step model, which limits its application in various processing conditions. Furthermore, this denaturation of β-lg is only an initial stage in a series of interactions to take place. In this work, a multistep model for the denaturation of β-lg and its subsequent reaction with κ-casein was developed. This model was used to rationalize the concentrations of native β-lg and κ-casein determined from HPLC. Notably, this model provides a clear account of the influence of β-lg on the loss of micelle-bound κ-casein. The various reaction rates reveal reactions are limited by the rate at which sulfhydryl-disulfide reactions connect proteins while the effect of intermolecular forces is minimal.

Elastohydrodynamic ultrathin film formation at the start-up of motion under the combined effect of surface force and hydrodynamic action

Purpose The purpose of this study is to investigate the behavior of ultra-thin film formation at the start-up of motion for different acceleration rates and final entrainment speed, including the effect of intermolecular forces; solvation and Van der Waals’ in addition to hydrodynamic action for the elastohydrodynamic lubrication of point contact problems. Design/methodology/approach The equation of motion of the ball is considered to account for the applied force on the ball during the start-up of motion. The Newton–Raphson with Gauss–Seidel iterative method is used to solve the Reynolds, film thickness and load balance equations simultaneously. In addition to hydrodynamic effects, solvation and Van der Waals’ forces are taken into account in the calculation of bearing capacity. Findings The simulation results showed that the effects of acceleration rate are important for ultra-thin film formation at the start-up of motion. Increasing the rate of acceleration results in a higher value of central film thickness during the start-up of motion than the corresponding steady-state film thickness value reached at the final entrainment speed. The effects of intermolecular forces are important to prevent metal-to-metal contact during the inactive period of motion, where a constant value of film thickness is achieved regardless of the value of the acceleration rate or final entrainment speed. Originality/value The behavior of ultra-thin film formation at start-up of motion, including the effect of intermolecular forces; solvation and Van-der-Waals’ along with hydrodynamic action, are evaluated after different acceleration rates and final entrainment speeds.

From Individual Liquid Films to Macroscopic Foam Dynamics: A Comparison between Polymers and a Nonionic Surfactant.

Foams can resist destabilizaton in ways that appear similar on a macroscopic scale, but the microscopic origins of the stability and the loss thereof can be quite diverse. Here, we compare both the macroscopic drainage and ultimate collapse of aqueous foams stabilized by either a partially hydrolyzed poly(vinyl alcohol) (PVA) or a nonionic low-molecular-weight surfactant (BrijO10) with the dynamics of individual thin films at the microscale. From this comparison, we gain significant insight regarding the effect of both surface stresses and intermolecular forces on macroscopic foam stability. Distinct regimes in the lifetime of the foams were observed. Drainage at early stages is controlled by the different stress-boundary conditions at the surfaces of the bubbles between the polymer and the surfactant. The stress-carrying capacity of PVA-stabilized interfaces is a result of the mutual contribution of Marangoni stresses and surface shear viscosity. In contrast, surface shear inviscidity and much weaker Marangoni stresses were observed for the nonionic surfactant surfaces, resulting in faster drainage times, both at the level of the single film and the macroscopic foam. At longer times, the PVA foams present a regime of homogeneous coalescence where isolated coalescence events are observed. This regime, which is observed only for PVA foams, occurs when the capillary pressure reaches the maximum disjoining pressure. A final regime is then observed for both systems where a fast coalescence front propagates from the top to the bottom of the foams. The critical liquid fractions and capillary pressures at which this regime is obtained are similar for both PVA and BrijO10 foams, which most likely indicates that collapse is related to a universal mechanism that seems unrelated to the stabilizer interfacial dynamics.

Enhancing photocurrent of dye-sensitized solar cells through solvent modulating aggregation of dyes

Aggregation of organic molecules plays a key role in determining the photoelectronic properties of various devices. However, the formation of aggregates is an outcome of complex synergistic effects of various intermolecular forces, and changes with the molecular structure and environment. Here we exploit the aggregation of two dyes with (MTPABT-Pyc) or without (MTPAcc) the nanosecond long-lived charge separation state and their effect on photovoltaic performance of dye-sensitized solar cells (DSSCs). Different solvent systems were selected to modulate the interactions between solvents and dye molecules for the effects on photophysical processes. Combining the experimental results on the solvent effect on dye aggregation with theoretical calculations reveals that MTPAcc inclines to form H-aggregation on the TiO2 surface because of the decisive role of its molecular structure. The solvent regulation has a great impact on MTPABT-Pyc which can make aggregates transform between H-aggregation and J-aggregation. The effects of aggregation on the device performance of two dyes are completely opposite. High performance of MTPAcc depends on the co-adsorbent chenodeoxycholic acid, which could suppress the dye aggregation. In contrast, the aggregation of MTPABT-Pyc will not harm the charge separation and transportation processes in devices and shows a positive effect on the cell performance due to the aggregation exhibiting broader absorption bands. As the photocurrent contribution by the aggregation-induced long-wavelength absorption increases from 9% (H-aggregation) to 34% (J-aggregation), the short-circuit current (Jsc) and the power conversion efficiency (PCE) of MTPABT-Pyc increased by 13% and 14%, respectively. These results pave a new way for taking full advantage of the aggregation of molecules to realize high-performance light-to-current conversion.

Modeling surface tension of ionic liquids by chemical structure-intelligence based models

Surface tension is one of the most significant physicochemical characteristics in process design, industrial applications of heterogeneous systems, and scientific applications. To estimate the surface tension of ionic liquids, acquiring a reliable and accurate model is crucial since experimental measurements are costly and time-consuming. In this regard, the main objective of this study is to estimate the surface tension of ionic liquids (ILs) by utilizing two mathematical models based on the radial basis function (RBF) and least square-support vector machine (LSSVM), coupled with two optimization algorithms namely firefly algorithm (FFA) and differential evolution (DE). In this work, a huge experimental dataset including 1042 data points from 69 ILs was utilized. The dataset consists of surface tension and temperature over a range of 18.5–70.3 mN/m and 268.29–532.4 K, respectively, where the pressure is constant (0.101 MPa). The input parameters were chosen to be chemical structure and temperature, whereas the surface tension was the output parameter. Sensitivity analysis, statistical, and graphical error were used in order to evaluate the performance and accuracy of the proposed models. The results showed that the LSSVM-FFA model accurately predicts the surface tension of ILs with the percentage of average absolute relative deviation of 1.8440% and determination coefficient of 0.9828. The sensitivity analysis showed that surface tension is affected by some substrates such as NH2 and SO2 more dominantly compared to other substructures. Furthermore, statistical and graphical error analyses of the models developed in this study along with those obtained from the literature demonstrate that the LSSVM-FFA model significantly outperforms all the existing models in terms of accuracy and range of validity. Finally, conclusions drawn from understanding the impact of temperature on the surface tension using the proposed models reveals a declining surface tension with increasing temperature owing to the effect of intermolecular forces. The outcome of this study can help not only circumvent the challenges of predicting surface tension of ILs, but also establish modern and reliable predictive approaches for an extensive dataset over a wide range of temperatures.

Modification of the Fluctuation Dynamics of Ultrathin Wetting Films.

We report on the effect of intermolecular forces on the fluctuations of supported liquid films. Using an optically induced thermal gradient, we form nanometer-thin films of wetting liquids on glass substrates, where van der Waals forces are balanced by thermocapillary forces. We show that the fluctuation dynamics of the film interface is strongly modified by intermolecular forces at lower frequencies. Data spanning three frequency decades are in excellent agreement with theoretical predictions accounting for van der Waals forces. Our results emphasize the relevance of intermolecular forces on thermal fluctuations when fluids are confined at the nanoscale.

Effect of hydrophilic or hydrophobic interactions on the self-assembly behavior and micro-morphology of a collagen mimetic peptide

Peptide self-assembles with bionic properties have been widely utilized for bioactive drugs and biomedical materials. Collagen mimetic peptide (CMP) gains more attention due to its unique advantages in biosecurity and function. Unfortunately, the self-assembly mechanism of CMP, particularly the effect of intermolecular forces on its self-assembly behavior and morphology, is still unrecognized. Herein, the hydrophilic glycidol (GCD) and hydrophobic Y-glycidyl ether oxypropyl trimethoxysilane (GLH) were grafted onto the side chains of CMP through the ring-opening reaction (GCD/CMP, GLH/CMP). Subsequently, the effects of hydrophilic and hydrophobic interactions on the self-assembly behavior and morphology of CMP were further studied. The results substantiated that the GCD/CMP and GLH/CMP self-assembly followed “nucleation-growth” mechanism, and the supererogatory hydrophilic and hydrophobic groups prolonged the nucleation and growth time of CMP self-assembly. Noted that the hydrophilic interaction had stronger driving effects than hydrophobic interaction on the self-assembly of CMP. The GCD/CMP and GLH/CMP self-assembles exhibited fibrous 3D network and microsphere morphology, respectively. Furthermore, the GLH/CMP self-assembles had better resistance to degradation. Consequently, the microtopography and degradation properties of CMP self-assembles could be controlled by the hydrophilic and hydrophobic interactions between CMP, which would further provide a way for subsequent purposeful design of biomedical materials.Graphical abstract

A new design method for high conditions applied to minimum length nozzles

This present work focused on new nozzles design method, based on the characteristics method, which is a technique method to reduce a partial differential equation to linear differential equations along which the solution can be integrated from initial conditions. The latter is developed under the real gas theory, because when the both pressure and temperature of a gas increases, the specific heat and their ratio do not remain constant anymore and start to vary with the gas parameters. The gas doesn’t stay perfect, and it becomes a real gas. The presented equations of the characteristics remain valid whatever area or field of study. With the assumptions that Berthelot’s state equation accounts for molecular size and intermolecular force effects, expressions are developed for analyzing the supersonic flow for thermally and calorically imperfect gas. The resolution has been made by the finite differences method using the corrector predictor algorithm. As result, the developed mathematical model used to design 2D minimum length nozzles under effect of the stagnation parameters of fluid flow. A comparison for air with the perfect gas PG and high temperature HT models on the one hand and our results by the real gas theory on the other of nozzles are made. An important gain of length and weight can rise up to 40% and 20% respectively. It is in this context that Minimum Length Nozzle (MLN) nozzles for aerospace engines based on real gas theory were developed to achieve maximum thrust with the smallest possible nozzle weight (minimum length).

Numerical investigation of the thermal-caloric imperfections on entropy enhancement across normal shock waves

Changes in flow properties across a normal shock wave are calculated for a real gas, thus giving us a better affinity to the real behavior of the waves. The purpose of this work is to develop shock-wave theory under the gaseous imperfections. Expressions are developed for analyzing the supersonic flow of such a thermally and calorically imperfect gas. The effects of molecular size and intermolecular attraction forces are used to correct a state equation, focusing on determination of the impact of upstream stagnation parameters on a normal shock wave. Flow through a shock wave in air is investigated to find a general form for normal shock waves. At Mach numbers greater than 2.0, the temperature rise is considerably below, and hence the density rise is well above, that predicted assuming ideal gas behavior. It is shown that caloric imperfections in air have an appreciable effect on the parameters developed in the processes considered. Computation of errors between the present model based on real gas theory and a perfect gas model shows that the influence of the thermal and caloric imperfections associated with a real gas is important.

Propulsion and Thermodynamic Parameters of van der Waals Gases in Rocket Nozzles

Propellants or combustion products can reach high pressures and temperatures in advanced or conventional propulsion systems. Variations in flow properties and the effects of real gases along a nozzle can become significant and influence the calculation of propulsion and thermodynamic parameters used in performance analysis and design of rockets. This work derives new analytical solutions for propulsion parameters, considering gases obeying the van der Waals equation of state with specific heats varying with pressure and temperature. Steady isentropic one-dimensional flows through a nozzle are assumed for the determination of specific impulse, characteristic velocity, thrust coefficient, critical flow constant, and exit and throat flow properties of He, H2, N2, H2O, and CO2 gases. Errors of ideal gas solutions for calorically perfect and thermally perfect gases are determined with respect to van der Waals gases, for chamber temperatures varying from 1000 to 4000 K and chamber pressures from 5 to 35 MPa. The effects of covolumes and intermolecular attraction forces on flow and propulsion parameters are analyzed.

Separation and model correlation for p-nitroaniline and m-nitroaniline mixture with subcritical R134a

To evaluate the separation feasibility of subcritical 1,1,1,2-tetrafluoroethane (sub-R134a) for mixture of p-nitroaniline (p-NA) and m-nitroaniline (m-NA), the separating effect and equilibrium solubility of p-NA and m-NA in both sub-R134a binary and ternary system are measured with static method at 308, 318, 328 K and (5–18) MPa for the first time. The effect of temperature, pressure, solvent density, dipole moment, molecular volume, and intermolecular forces on solubility are analyzed; in addition, the separating effect and solute solubility are compared with those in SCCO2. At 318 K and 18.0 MPa, the separation efficiency of sub-R134a for the solute mixture reaches to the maximum of 87.89%.Semi-empirical models, including Chrastil, A-L, K-J and S-S models for binary system, and González, Sovová, M-M-T, and Z-J models for ternary system, are used for correlating the experimental solubility. The satisfactory correlated results are obtained with the AARD value ranging from 4.85% to 11.27%.