Transport Properties Of Liquids Research Articles

Physical and transport properties of ionic liquids using the geometric similitude concept and a cubic equation of state. Part 1: Thermal conductivity and speed of sound of pure substances

A model based on the geometric similitude concept recently proposed by the authors is extended to calculate the thermal conductivity and the speed of sound of ionic liquids. Experimental data for these properties are employed to determine the constants and the parameters of the proposed general model. The experimental data are taken from ionic liquid database provided by the National Institute of Standards and Technology (NIST). In total, 320 thermal conductivity data (40 ionic liquids) and 2572 speed of sound data (61 ionic liquids), at the temperature range of 263.15 K to 390.15 K and pressure from 0.86 up to 2000 bar have been considered. The proposed empirical equation of state model contains only one adjustable parameter for each ionic liquid, parameter that can be determined using a single experimental data or can be generalized in terms of other available properties, as proposed in this work. The results show that the equation of state model provides acceptable results for the correlation and prediction of the thermal conductivity and the speed of sound for the studied pure ionic liquids.

Liquid Structure and Transport Properties of the Deep Eutectic Solvent Ethaline

A range of techniques including physical property measurements, neutron scattering experiments, ab initio molecular dynamics, and classical molecular dynamics simulations are used to probe the structural, thermodynamic, and transport properties of a deep eutectic solvent comprised of a 1:2 molar ratio of choline chloride and ethylene glycol. This mixture, known as Ethaline, has many desirable properties for use in a range of applications, and therefore, understanding its liquid structure and transport properties is of interest. Simulation results are able to capture experimental densities, diffusivities, viscosities, and structure factors extremely well. The solvation environment is dynamic and dominated by different hydrogen bonding interactions. Dynamic heterogeneities resulting from hydrogen bonding interactions are quantified. Rotational dynamics of molecular dipole moments of choline and ethylene glycol are computed and found to exhibit a fast and slow mode.

Silicon carbide filters and porous membranes: A review of processing, properties, performance and application

Silicon carbide (SiC) filters and porous membranes is a growing industry with deployment for gas and liquid separation processes. In view of its importance, the research efforts into the development of SiC filters and membranes are of growing interest around the world. Therefore, this review paper is focused on the latest advancements in SiC and SiC composites used for the preparation of substrates and thin films in filters and membranes. There is a multitude of methods used to prepare filters and membranes of different shapes (tubular, honeycomb, flat sheets and multi-channel), which are influenced by precursor mixture and sintering conditions. In turn, these processing conditions affect porosity and pore size, which affects the transport and separation properties of SiC filters and membranes. SiC particles size and distribution allow for the precise control of pore size in membranes, leading to high gas separation factors. In addition, SiC has strong thermal stability properties that are very desirable for high temperature gas cleaning. Together with gas and liquid transport and separation properties, this review also addresses the potential applications in gas and liquid separation processes, coupled with thermal/chemical stability properties. Future challenges are highlighted towards further research efforts.

How to detect possible pitfalls in ePC-SAFT modelling: Extension to ionic liquids

An ion-specific electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) has been developed to describe the thermodynamic and transport properties of ionic liquids (ILs) for developing IL-based technologies to separate CO2 from gas mixtures. However, as it has been pointed out previously, SAFT-based models can lead to a pitfall, manifesting as an additional fictitious liquid-liquid critical line connected to an additional mechanically stable critical point when modeling pure substances. In this work, a method for detecting a pitfall in ILs was developed, where an expression with ionic term for calculating the critical point with ePC-SAFT was derived and an algorithm for detecting the additional fictitious phase equilibrium for ILs was proposed. The pitfall occurrence for an extended set ILs taken from our previous work was investigated. It shows that a pitfall occurs only for one single IL among all 96 ILs in the temperature and pressure range of interest. For [C8mpy][BF4], at 290.27–291.78 K, a pitfall may occur at the pressures of interest; at 273.15–290.20 K, it may occur at any given pressure. The ion-specific ePC-SAFT parameters for [C8mpy]+ may therefore need to be modified in the future when more reliable experimental results are available for parameter fitting.

Highly concentrated LiN(SO2CF3)2/dinitrile electrolytes: Liquid structures, transport properties, and electrochemistry.

Liquid structures, transport properties, and electrochemical properties of binary mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and dinitrile solvents [succinonitrile (SN), glutaronitrile (GN), and adiponitrile (ADN)] were investigated. In the LiTFSA/SN and LiTFSA/ADN systems, the stable crystalline solvates of LiTFSA-(SN)1.5 [melting point (Tm): 59 °C] and LiTFSA-(ADN)1.5 (Tm: 50 °C) were formed, respectively. In contrast, the LiTFSA/GN mixtures of a wide range of compositions were found to be glass-forming liquids at room temperature. Raman spectroscopy of LiTFSA/GN liquid mixtures revealed that increasing the LiTFSA concentration results in the formation of the solvent-bridged network structure Li+-GN-Li+. In addition, the considerable formation of contact ion pairs and ionic aggregates was observed in highly concentrated electrolytes. In the liquids, the Li+ ion dynamically exchanged ligands (GN and TFSA) and higher LiTFSA concentrations led to an increase in the ratio of the self-diffusion coefficients of Li+ and TFSA-, DLi/DTFSA, as determined by pulsed field gradient NMR spectroscopy. The Li+ transference number (tLi+ ) of the [LiTFSA]/[GN] = 1/1.5 electrolyte in an electrochemical cell under anion-blocking conditions was estimated to be as high as 0.74. Furthermore, electrochemical measurements revealed that the reductive stability of the LiTFSA/GN electrolyte increases with increasing LiTFSA concentration. A [LiTFSA]/[GN] = 1/1.5 electrolyte is stable against the Li metal electrode, provided that the polarization is relatively small. Owing to high tLi+ , a Li-S battery with the [LiTFSA]/[GN] = 1/1.5 electrolyte showed a high rate discharge capability despite its low ionic conductivity (0.21 mS cm-1) at room temperature.

Comments on “preparation and transport properties of novel lithium ionic liquids [electrochim. Acta 50 (2004) 1–5]” and “ion transport properties of lithium ionic liquids and their ion gels. [Electrochim. acta 50 (2005) 3872–3877

Some years ago, Shobukawa et al. published transport data for a number of lithium salts with complex borate anions having oligoether groups substituted on the central boron atom. It is the purpose of this Comment to show that the data are consistent with cation-anion association as deduced from the Laity resistance coefficients of non-equilibrium thermodynamics. This is most likely due to strong lithium interactions with the oxygen atoms of the ether linkages which has also been postulated in studies of lithium salt-phosphonium ionic liquid mixtures where the cations have similar ether linkages.

Instrumentation for Measuring the Wet Frictional Property of Sanitary Pads

Women wear sanitary pad for whole day during their menstruation period. They have direct skin contact with it even for sleeping and exercising. The presence of sweat and menstrual blood increases the moisture level and the adhesion of liquid to textile causing sensorial discomfort. This study describes the design and uses of modified Textile Stickiness Measurement System (TSMS) which can characterize the frictional properties of sanitary pads under both dry and wet conditions. The uniqueness of this measurement system is that the wetness level of the pad is adjustable and the surface profile of the contacting object (i.e. Lorica®Soft) does simulate the condition of human skin. Also, it does not have restriction on the type of sanitary pad that can be tested. Among the 12 sanitary pads tested (disposable and reusable types), the frictional force for the disposable sanitary pads is lower than the reusable pads whilst the performance of disposable sanitary pads with nonwoven surface is lower than the one with perforated surface. These can attribute to their liquid transport property and surface feature. For those with better liquid transport property, less water will stay on skin surface and so the adhesion between skin and textiles is lower. For those with protruding fibers on its surface, it reduced the contact area and so the frictional force is lower.

Self-Consistent Scheme Combining MD and Order-N DFT Methods: An Improved Set of Nonpolarizable Force Fields for Ionic Liquids

The nonpolarizable force field of ionic liquids is tuned by using the self-consistent scheme of molecular dynamics (MD) simulation and first-principles calculation based on the order-N density functional theory (DFT). The atomic charges are determined by using the whole MD cell for DFT calculation and accounts effectively for the many-body effects of charge transfer and intramolecular polarization. The charges represent effective interactions in the condensed phase within the framework of the nonpolarizable force field and can be an alternative for an explicitly many-body model incorporating, for example, polarizability. Here we demonstrate the performance of nonpolarizable force field determined with the MD-DFT self-consistent scheme in imidazolium-, pyrrolidinium-, and ammonium-based ionic liquids. The variation ranges of molecular charges are much larger with the compositions of the ionic liquid than with the thermodynamic conditions, and the charge-ordering structures become systematically weaker with the effective charges. For energetic properties, while the calculated heat of vaporization depends on the atomic and molecular charges, the corresponding heat capacity is not strongly affected by the DFT-based variation. For transport properties, the self-diffusion coefficient, electrical conductivity, and viscosity vary much more in the self-consistent scheme. The effective DFT charge is observed to enhance the fluidity of ionic liquids and improve the accuracy of electrical conductivity and viscosity. This is due to the weakened interactions among the ions, and the too slow motions observed with a full-charge model are well corrected through the iteration of MD and DFT. We therefore conclude that the set of nonpolarizable force fields obtained with the MD-DFT self-consistent scheme leads to better description of transport properties of ionic liquids.

Rheological and Ionic Transport Properties of Nanocomposite Electrolytes Based on Protic Ionic Liquids and Silica Nanoparticles.

In this study, the effect of hydrophilic silica nanoparticle (AEROSIL 200) addition on the rheological and transport properties of several protic ionic liquids (PILs) consisting of protonated 1,8-diazabicyclo[5.4.0]undec-7-ene cation (DBU) was studied. Interactions between the surface silanol groups of the silica nanoparticles and the ions of these PILs affected the nature of particle aggregation and the hydrogen bonding environment, which was reflected in the nonlinear rheological behaviors and transport properties of their colloidal suspensions. In contrast to shear-thinning gels formed by colloidal suspensions of the silica nanoparticles in [DBU][TFSA] ([TFSA] = [N(SO2CF3)2]), [DBU][TfO] ([TfO] = [CF3SO3]), and [DBU][TFA] ([TFA] = [CF3CO2]), a shear-thickening stable suspension was formed in the [DBU][MSA] ([MSA] = [CH3SO3]) system. A relatively strong interaction between the silanol groups and the ions of [DBU][MSA] and the ability of this PIL to form a thicker solvation layer through hydrogen bonding were assumed to be responsible for this unique behavior. Moreover, the [DBU][MSA]-silica system showed a large enhancement in the conductivity at a certain silica concentration. This enhancement was not observed in the other PIL-silica composites that exhibited shear-thinning behavior. Even though diffusion of ions was found to be restricted in the presence of silica, a preferentially stronger interaction between [MSA] anions and the silica surface resulted in an increase in the number of charge carriers.

Measurement of Liquid Transport Properties of Sanitary Napkin with Modified Forced Flow Water Transport Tester

Sanitary napkin is worn in direct skin contact and is an essential product for most women. Its liquid transport properties, depending on the material and design, affect skin wetness, skin irritating potential and comfortable feeling. Disposable sanitary napkin is commonly used whilst reusable sanitary napkin is also available in the market for sustainable reason. In this study, a measurement method originated from Forced Flow Water Transport Tester (FFWTT) was introduced which can characterize the direction of liquid transport of sanitary napkin under different pressure loadings. Disposable sanitary napkins with nonwoven or perforated film surface were compared against the reusable sanitary napkins. The results found that the reusable sanitary napkins tend to accumulate more next-to-skin moisture than the disposable sanitary napkin at equivalent loadings. Also, its transplanar wicking is poor. Besides, disposable sanitary napkins incorporated with superabsorbent polymer provide acceptable liquid transport property whilst those made of flex foam give the best performance.

Effect of liquid phase composition on the experimental determination of binary gas diffusivities in an isothermal Stefan diffusion column

The Stefan diffusion column was designed in the 19th Century to determine binary gas diffusivities, DAB’s. Typically, pure liquid A is overlaid by gases A and stagnant B, with a steady gas B sweep at the top to remove the evaporated-diffused A. Experimental diffusivities DAB,exp may be obtained from transient interfacial descent data, but column end effects impacting such determination have been ignored or neglected in the literature. This study addresses experimentally and theoretically for the first time the role played by liquid phase composition on DAB determination using the Stefan column. Specifically, changes in interfacial curvature were sought by adding a nonvolatile liquid I (glycerol) to a volatile liquid A (ethanol). Mixtures of known initial composition xA0 were tested in isothermal evaporation-diffusion experiments at ∼65 °C using atmospheric air (B). A one-dimensional transport model for gas A was used to analyze the interfacial descent data. The average DAB,exp errors did not differ significantly between the liquid mixture groups and those for pure ethanol (range for the latter of +9.9 to +17.1%). However, considerable scatter in DAB,exp occurred as the mixtures became more dilute in ethanol, with the coefficient of variation increasing more than ten-fold in the xA0 = 0.146 group. This variability cannot be explained by differences in surface tension exclusively, but may also result from changes in liquid physical and transport properties as well as diffusion of liquid A. A more comprehensive modeling of the liquid phase in conjunction with gas phase transport is necessary to obtain accurate DAB’s.

Bioinspired fabrication of asymmetric wood materials for directional liquid manipulation and transport

Directional liquid transport, an essential process found in many natural creatures, is of great importance to environment, energy, and even life. Wood plants possess directional water transportation from soil to air, however, wood-based materials have no longer such performance because the pressure difference induced by transpiration is lost. Inspired by the controlled transport of water droplets on cactus pine, here, wettability gradient is constructed along wood channels, fabricating novel asymmetric wood slices. The hierarchically micro-/nano-structures and wettability gradients of the slices guarantee the tunable surface wettability and directional liquid transport property. Besides water, the resultant asymmetric wood can directionally deliver oils and moisture. Moreover, the functional wood displays high resistance against harsh corrosions without changing micro-structures or losing directional liquid transport property. The results demonstrate the asymmetric wood material will be useful in liquid manipulation, water harvest and treatment, self-cleaning, anti-fouling, and smart building materials.

Effects of the Water Content on the Transport Properties of Ionic Liquids

Ionic liquids (ILs) have been applied in many fields in recent years, but the high viscosity of ILs has become an important factor hindering the further implementation of ILs. ILs/water binary mixtures often show a lower viscosity than pure ILs. However, the general effects of the water content on the viscosity remain unclear. In this work, the viscosities and self-diffusivity of a series of [Cnmim][Ac] (1-alkyl-3-methyl imidazole acetate) ILs were computed by molecular dynamics simulations with a water mass percentage of 0.02–10%. The results show a general rule that the viscosities of all [Cnmim][Ac] ILs (n = 1–6) first increase and then decrease by adding a certain amount of water, which correlate well with the corresponding reciprocals of self-diffusion coefficients. Interestingly, the inflection points of the viscosity gradually move forward in the direction of a lower water content when increasing the chain length, which is the result of increased hydrophobicity. Structural analysis shows that the chainlike structure of anion···water···anion is the key reason for the increase-to-decrease behavior of viscosity when water is added. Moreover, the sharp peaks of radial distribution functions between water and Ac– go up first and then move down, and the peak positions follow the same trend of inflection points.

Thermodynamic and transport properties of ionic liquids, 1-alkyl-3-methylimidazolium thiocyanate in the aqueous lithium halides solutions

Thiocyanate based ionic liquids, [RMIM][SCN], as fluorine free and low toxic were used effectively in different areas of resaerch. In this work, the thermodynamic and transport properties of aqueous solutions of the synthesized ionic liquids based on thiocyanate anion, [RMIM][SCN] (R = butyl, hexyl and octyl) have been investigated at T = (288.15–318.15) K. Also, effect of LiX (X = Cl−, Br−) salts on the investigated properties have been studied at T = 298.15 K. In this respect, density, speed of sound and viscosity of the solutions have been measured and these properties were used to calculate the apparent molar volume, Vφ, and apparent molar isentropic compressibility κφ. The properties were correlated with corresponding empirical relations to achieve standard partial molar volume, Vφ0, partial molar isentropic compressibility, κφ0, and viscosity B-coefficient. These parameters were used to analysis of the interactions between components. In order to separate Vφ0 contributions of the ILs in binary solutions, the scaled particle theory was used at T = (288.15–318.15) K. The results show that the hydrophobic hydration interactions are dominant interactions.

Effect of the chain lengthening on transport properties of imidazolium-based ionic liquids

The objective of this work is to study the effect of the lengthening of the linear alkyl chain of the imidazolium cation on some transport properties. We focused on hydrophobic ionic liquids based on bis(trifluoromethanesulfonyl)imide anion. Among the different properties, we measured at the viscosity and ionic conductivity of four different 1-alkyl-3-methylimidazolium ionic liquid in the temperature range between 293 and 333K. Thus, Electrochemical windows of these ionic liquids and the diffusion coefficient of ferrocenemethanol (FcMeOH) in the four ionic liquids were studied using cyclic voltammetry at 298K. The FcMeOH diffusion coefficient was found to be higher in shorter alkyl chain ionic liquids.

Survey on transport properties of vapours and liquids on biodegradable polymers

In this work an extensive study of vapour and liquid transport properties for various biodegradable polymers has been performed being this kind of studies scarce in literature. For that different techniques have been employed: vapour and liquid transmission rate measurements and vapour and liquid sorption measurements. The study of the vapour and liquid transmission rate of different solvent families allows to shed light on the influence of several factors: nature of the penetrant and polymer, solubility parameter, glass transition temperature and free volume fraction of the polymer, being the last two the factors that play the most important role in the permeability coefficient. Furthermore, based on the solubility parameter, δ, it has been proved that Δδ=δpol-δsol can be used as a tool to predict qualitatively the transport properties. In liquid transmission rate measurements the plasticization and the work of adhesion between the polymer and the solvent influence greatly the obtained results. Sorption measurements have shown that plasticization and clustering phenomena occur. The liquid sorption characterization indicates that both, the molecule size and chemical nature, influence considerably the permeation, obtaining values that expand over 2 decades. Overall, this work aims to provide a deep insight on the transport properties of organic compounds on biodegradable polymers that would allow broadening their applications not only in packaging but also in separation processes.

Mechanisms of Ion Transport in Block Copolymeric Polymerized Ionic Liquids.

We present the results of a multiscale simulation framework investigating the ion transport mechanisms in multicomponent polymerized ionic liquids. Three different classes of polymeric ionic liquid systems, namely, random copolymers, lamellae forming block copolymers, and homopolymers, are constructed at the coarse-grained scale, and their atomistic counterparts are derived by using a reverse mapping method. Using such a framework, we investigate the influence of morphology on ion transport properties of such polymerized ionic liquids. Our results for ion mobilities are in qualitative agreement with experimental observations. Further analysis of random copolymer and block copolymer systems reveal that the reduced ion mobilities in such systems arise from the influence of architecture and morphology on ion coordination and intramolecular hopping events.

Thermodynamic, Dynamic, and Transport Properties of Quantum Spin Liquid in Herbertsmithite from an Experimental and Theoretical Point of View

In our review, we focus on the quantum spin liquid (QSL), defining the thermodynamic, transport, and relaxation properties of geometrically frustrated magnet (insulators) represented by herbertsmithite ZnCu 3 ( OH ) 6 Cl 2 . The review mostly deals with an historical perspective of our theoretical contributions on this subject, based on the theory of fermion condensation closely related to the emergence (due to geometrical frustration) of dispersionless parts in the fermionic quasiparticle spectrum, so-called flat bands. QSL is a quantum state of matter having neither magnetic order nor gapped excitations even at zero temperature. QSL along with heavy fermion metals can form a new state of matter induced by the topological fermion condensation quantum phase transition. The observation of QSL in actual materials such as herbertsmithite is of fundamental significance both theoretically and technologically, as it could open a path to the creation of topologically protected states for quantum information processing and quantum computation. It is therefore of great importance to establish the presence of a gapless QSL state in one of the most prospective materials, herbertsmithite. In this respect, the interpretation of current theoretical and experimental studies of herbertsmithite are controversial in their implications. Based on published experimental data augmented by our theoretical analysis, we present evidence for the the existence of a QSL in the geometrically frustrated insulator herbertsmithite ZnCu 3 ( OH ) 6 Cl 2 , providing a strategy for unambiguous identification of such a state in other materials. To clarify the nature of QSL in herbertsmithite, we recommend measurements of heat transport, low-energy inelastic neutron scattering, and optical conductivity σ ¯ in ZnCu 3 ( OH ) 6 Cl 2 crystals subject to an external magnetic field at low temperatures. Our analysis of the behavior of σ ¯ in herbertsmithite justifies this set of measurements, which can provide a conclusive experimental demonstration of the nature of its spinon-composed quantum spin liquid. Theoretical study of the optical conductivity of herbertsmithite allows us to expose the physical mechanisms responsible for its temperature and magnetic field dependence. We also suggest that artificially or spontaneously introducing inhomogeneity at nanoscale into ZnCu 3 ( OH ) 6 Cl 2 can both stabilize its QSL and simplify its chemical preparation, and can provide for tests that elucidate the role of impurities. We make predictions of the results of specified measurements related to the dynamical, thermodynamic, and transport properties in the case of a gapless QSL.

On the Use of the Angell-Walden Equation To Determine the "Ionicity" of Molten Salts and Ionic Liquids.

In this work, the Angell analysis of Walden plots of the conductivity of ionic liquids and other electrolytes against viscosity is used to examine simple molten salts at high temperatures, a test that does not appear to have been made previously. It is found that many simple salts such as alkali metal fluorides and chlorides are predicted to be "superionic" as their Walden plots fall above the arbitrary reference line introduced by Angell, which passes through the datum point for 1 M aqueous KCl at 25 °C. This contradicts long-standing molecular dynamics evidence in the literature showing that these salts conduct simply by ion migration in an electric field. Zinc chloride is also predicted to be "ideal", whereas one would expect it to be "subionic" in Angell's terminology given that it is an associated salt. Results for certain protic ionic liquids are also contradictory. Therefore, Angell-Walden analyses of this type do not convey any useful information other than a qualitative ranking of the conductivity of similar ionic liquids at a given viscosity and their use for estimating "ionicity" is best discontinued. It cannot and should not be used for classifying the interactions in ionic liquids. Instead, it is argued that an examination of Laity resistance coefficients is more useful in any discussion of true association in molten salts and ionic liquids where known examples show negative like-ion resistance coefficients with NE deviation parameters close to unity. Such an approach could be more fruitful in understanding the transport properties of molten salts and ionic liquids rather than simple comparisons of viscosity and conductivity.

Assessment of thermal and transport properties of ionic liquids as suitable absorbent for absorption cooling applications

Ionic liquids, salts which have liquid phase at temperature below 100°C, have been widely introduced in engineering applications, including absorption cooling systems. The application of ionic liquids in absorption cooling systems is intended to remove the disadvantages of conventional working fluids such as corrosion and crystallization. In terms of thermodynamic performances, theoretical investigation based on solubility behavior of ionic liquids in natural refrigerants show a competitive performance in comparison with conventional working fluid. Nevertheless, heat transfer performance, which is also an important key in absorption cooling systems, particularly in terms of system design and size, needs to be deeply explored and investigated. This study aims to assess the thermal and transport properties of ionic liquids as absorbent in relation to the heat and mass transfer characteristics of these working fluids. The thermal and transport properties of ionic liquids proposed as absorbent for absorption cooling systems are collected, and heat and mass transfer characteristic of these ionic liquids based on their thermal and transport properties are investigated and analyzed. Finally, the most suitable ionic liquids for absorption machines, both in terms of thermodynamics and heat and mass transfer performances can be proposed.