Vogel-Fulcher-Tammann Equation Research Articles

Temperature and composition dependence modeling of viscosity and electrical conductivity of low-activity waste glass melts

The development of models that accurately relate the properties of a glass melt to its temperature and composition is important for glass formulation, melter control, and modeling the melt flow, refractory corrosion, and production rate. Using a database consisting of more than 4,000 data points measured between 900 °C and 1250 °C for over 600 unique low-activity waste glass compositions, we developed models for the melt viscosity and electrical conductivity. Models based on the Gaussian process regression approach outperformed models based on the Vogel–Fulcher–Tammann equation according to four standard metrics and yielded reliable prediction intervals. The models found primarily linear effects between properties and individual components, except for the effect of the Na2O mass fraction on the electrical conductivity. The effects were found to be consistent with current theories on physical processes involved with those properties.

Influence of shear deformation on the formation of dynamic structure in protic ionic liquids. Representation of the temperature dependence of viscosity within the framework of Angell’s fragility concept

The rheological properties of a liquid containing two types of basic centers and hydroxyl groups (BGE-Im), as well as protic ionic liquids (ILs) derived from it, were studied in a wide range of shear rates (γ̇) (10−6–103 s−1) at various temperatures from 10 to 50 °C. Viscosity (η) of the BGE-Im does not depend on the scanning direction of shear stress (σ), i.e. this compound behaves like a Newtonian fluid over the entire range of σ. The dependence log η (1/T) of BGE-Im in Arrhenius coordinates is linear. Protonation of basic centers of BGE-Im leads to a strong increase in the viscosity of ILs obtained on its basis, and the temperature dependence of the viscosity of these ILs is described by the Vogel–Fulcher–Tammann (VFT) equation. It has been established that in the region of low shear rates, the viscosity of the ILs increases with decreasing shear rate, which leads to the appearance of a yield stress (σY). This indicates the formation of a fluctuation rheopectic structure in the ILs. In this sense, ILs are heterogeneous systems and their behavior is similar to that of highly concentrated suspensions and emulsions. For the first time, a quantitative comparison between the parameters of the VFT equation, the fragility (according to Angell’s model) of ILs, the relative coordination number of ILs molecules and the rheological yield stress characterizing the shear-induced fluctuation rheopectic structure of ILs has been made and the relationship between these characteristics has been shown.

Viscosity and surface tension of the Zr56.5Ti13.3Ni13.6Cu9.6S7 bulk metallic glass-forming liquid

The viscosity of the Zr56.5Ti13.3Ni13.6Cu9.6S7 bulk glass forming alloy was measured in equilibrium liquid at low and high temperatures. Low temperature measurements were conducted in the vicinity of the glass transition using a thermomechanical analyzer, covering a viscosity range between 109 and 1014 Pa s. The high-temperature experiments were carried out by electromagnetic levitation of a spherical droplet in microgravity during a parabolic flight campaign (TEMPUS), ranging in viscosity from 50 to 800 mPa s. The viscosities were individually modeled using the Vogel–Fulcher–Tammann equation to obtain the fragility parameter D*, which displays a strong liquid behavior of 25.8 and 19.6 for the low and high temperature region, respectively. The Mauro–Yue–Ellison–Gupta–Allan viscosity model was additionally applied, revealing an even more accurate description across the whole temperature range. Next to viscosity, TEMPUS measurements allow the determination of surface tension. With a value of 0.9 N m−1, it is significantly lower than that of other Zr-based metallic glasses without the element sulfur.

Crystallization of Zr-Based Amorphous Alloys in Laser Welding

Crystallization often occurs in the laser welding of amorphous alloys, reducing the properties of amorphous alloys. Therefore, the research in this thesis focuses on the experimental selection of suitable welding parameters to prevent crystallization of Zr-based amorphous alloys during the laser welding process. As such, it is necessary to simulate the temperature field curve of the welding area by computer and then determine the power and laser moving speed of laser welding. In this paper, the temperature field curve of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit1) amorphous alloy in laser welding is obtained by finite element analysis. The continuous heating curve (CHT) of Vit1 is fitted by the Vogel–Fulcher–Tammann (VFT) equation and the Kissinger equation. If the temperature field curve intersects with the CHT curve, crystallization occurs. The experiment results show that the VFT equation can be used to predict the crystallization of Vit1 better in laser welding. The temperature and welding time are increased by using a low welding speed. Therefore, the temperature of the weld zone cannot fall in time, resulting in the intersection of the temperature field curve and the CHT curve. Thus, crystallization can be avoided if the welding speed is controlled within a reasonable range, and the highest temperature is kept under the CHT curve. The combination of the CHT curve and the temperature field curve shows that the samples at 300 W-3 mm/s and 300 W-6 mm/s welding parameters all undergo crystallization, while the samples at 300 W-9 mm/s and 300 W-12 mm/s welding parameters do not undergo crystallization. Through the flexural test, it is found that the flexural strength of the welded interface is at its the maximum under 300 W-9 mm/s.

Determination of cooperatively rearranging regions in a binary glass former

Cooperative motions are important for understanding the divergence of viscosity of glassy materials at a finite temperature, since the elementary process of the structural relaxation occurs within the smallest cooperative region as suggested by Adam and Gibbs. On the basis of the definition of a cooperatively rearranging region (CRR) by Adam and Gibbs and by Odagaki, we determine the size of CRR for the Kob–Andersen model as a function of temperature using molecular dynamics simulations. We first confine particles in a spherical region and, varying the radius of that region, we determine the CRR size as the smallest radius of the region in which particles can change their relative positions. The size of the CRR increases as the temperature is reduced and seems to diverge below the glass transition temperature. The temperature dependence of the number of particles in the CRR obeys the equation derived from the Adam–Gibbs relation and the Vogel–Fulcher–Tammann equation.

Molecular dynamics in amorphous double active ionic liquid developed by chemical structural modification of ibuprofen

Ibuprofen is a non-steroidal anti-inflammatory drug categorized as a Class II Biopharmaceutics Classification System (BCS) pharmaceutical with low solubility and high permeability. Though the drug and its salt form are glass-forming, but not physically stable in their amorphous state, which limits their use as amorphous drugs. In this study, a dual-active pharmaceutical ingredient, metforminium ibuprofenate (MtHIb), was prepared by chemical structural modification of sodium ibuprofen (NaIb) with metformin hydrochloride (MtHCl) by a stochiometric metathesis reaction. Information on translational and rotational mobility of both daughter and parents has been obtained from broadband dielectric spectroscopy (BDS) covering a wide temperature and frequency regimes in supercooled and glassy states in conjunction with quantum mechanical calculations. The temperature dependence of α-relaxation times was described by Vogel–Fulcher–Tammann equation. The glass transition temperature for MtHCl and MtHIb were found to be 269.45 and 227.24 K, respectively, which is in good agreement with the DSC thermogram with a slight discrepancy. The fragility index of ibuprofen is found to decrease upon the modification and attained 50.39 for MtHIb indicating its strong glass-forming nature which is well evidently supported by broad diffraction peaks in X-ray diffraction patterns of MtHIb. These results demonstrate that chemical structural modification of ILs can be considered a proven strategy for inhibiting the devitrification of disordered pharmaceuticals to control or bypass the secondary relaxations in the glassy state by modification of its structure. These remarkable outcomes had an impact on the fundamental understanding of amorphous pharmaceuticals on the industrial front.

Experimental studies on several properties of PEG 400 and MWCNT nano-enhanced PEG 400 fluids

The main aim of this research is to design and study MWCNTs nanoparticles influence on polyethylene glycol PEG 400 thermophysical properties and structure. In order to accomplish this objective, four suspensions were manufactured and studied, along and in comparison with the base fluid. Structural analysis, in terms of powder X-ray Diffraction Studies (PXRD), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), rheology and electrical conductivity measurements were performed and was found that samples exhibit good electrical properties, while the viscosity was found to increase when MWCNTs are added. More precisely, melting and phase transitions were explored in relation to temperature from differential scanning calorimeter (DSC) thermograms. Experimental outcomes were linked with the values delivered in the literature and were discussed using different theoretical or experimental correlations. The increase in electrical conductivity is a polynomial one, going to an enhancement of about 16 times when 0.1 wt%. MWCNTs are added to the PEG 400. Rheological results show a non-Newtonian behavior of suspensions and an in-depth discussion on consistency and power – law index was included, together with the viscosity variation as functions of temperature and nanoparticle volume concentration (using Vogel–Fulcher–Tammann equation). Concluding, when it comes to viscosity analysis of MWCNT enhanced fluids, both nanoparticle dimensions, as well as shear rate are relevant influencing parameters.

Observation of ionic conductivity on PUA-TBAI-I2 gel polymer electrolyte

Jatropha oil-based polyurethane acylate gel polymer electrolyte was mixed with different concentrations of tetrabutylammonium iodide salt (TBAI). The temperature dependences of ionic conductivity, dielectric modulus and relaxation time were studied in the range of 298 to 393 K. The highest ionic conductivity of (1.88 ± 0.020) × 10–4 Scm−1 at 298 K was achieved when the gel contained 30 wt% of TBAI and 2.06 wt% of I2. Furthermore, the study found that conductivity-temperature dependence followed the Vogel-Tammann Fulcher equation. From that, it could be clearly observed that 30 wt% TBAI indicated the lowest activation energy of 6.947 kJ mol−1. By using the fitting method on the Nyquist plot, the number density, mobility and diffusion coefficient of the charge carrier were determined. The charge properties were analysed using the dielectric permittivity, modulus and dissipation factor. Apart from this, the stoke drag and capacitance were determined.

Electrical, electrochemical and structural studies of a chlorine-derived ionic liquid-based polymer gel electrolyte.

In the present article, an ionic liquid-based polymer gel electrolyte was synthesized by using poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) as a host polymer. The electrolyte films were synthesized by using the solution casting technique. The as-prepared films were free-standing and transparent with good dimensional stability. Optimized electrolyte films exhibit a maximum room-temperature ionic conductivity of σ = 8.9 × 10−3 S·cm−1. The temperature dependence of the prepared polymer gel electrolytes follows the thermally activated behavior of the Vogel–Tammann–Fulcher equation. The total ionic transference number was ≈0.91 with a wider electrochemical potential window of 4.0 V for the prepared electrolyte film which contains 30 wt % of the ionic liquid. The optimized films have good potential to be used as electrolyte materials for energy storage applications.

Complex Reorientation Dynamics of Sizable Glass-Formers with Polar Rotors Revealed by Dielectric Spectroscopy.

We present the results of dielectric measurements for three sizable glass-formers with identical nonpolar cores linked to various dipole-labeled rotors that shed new light on the picture of reorientation of anisotropic systems with significant moment of inertia revealed by broadband dielectric spectroscopy. The dynamics of sizable glass-formers formed by partially rigid molecular cores linked to small polar rotors in many respects differs from that of typical glass-formers. For instance, the extraordinarily large prefactors (τ0 > 10–12 s) in the Vogel–Fulcher–Tammann equation were found. The rich and highly diverse relaxation pattern was governed by the location of a dipole, its ability to rotate freely, and the degree of coupling to the motion of the entire sizable system.

Unfolding kinetic fragility in relaxor ferroelectrics

The fragility parameter is one of the most important material constants that is extensively used in glass science, playing a central role in the enhancement of understanding the glass formation process of disordered systems. Although fragility has been widely used, this concept has never been precisely defined and evaluated in relaxor ferroelectrics. Here, we have filled up this scientific gap. Based on a generalized Vogel–Fulcher–Tammann equation, the fragility parameter is introduced for relaxor ferroelectrics. The new formulation has been quantitatively assessed by combining dielectric spectroscopy and pyroelectric measurements on canonical relaxors. A clear correlation between the fragility and a new local structural heterogeneity-related order parameter elucidates new information about the ferroelectric order of relaxor ferroelectrics. This may open a new pathway to disentangle relaxation phenomena in other relaxor ferroics.

Temperature dependence and correlation of polarization processes in P(VDF-HFP) films

Polymer dielectrics are indispensable in electrical and electronic systems, being used as insulation, capacitors, gate dielectric, etc. However, a lot of polymer materials show unsatisfactory efficiency at high temperature and low frequencies, which has been found to be closely related to polarization processes. In this paper, the dielectric spectroscopy of poly (vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) films is investigated over a broad frequency range from 10 mHz to 1 MHz and temperature range from −130 °C to 130 °C based on the Dissado-Hill model. The processes in the entire response are identified and characterized quantitatively. The temperature dependence of major processes contributing to energy storage and dielectric loss are revealed. It is found that the variations of both β polarization and DC conductance coincide with Arrhenius equation, while both α polarization and quasi-DC polarization show Vogel−Fulcher−Tammann (VFT) features. Moreover, α polarization and quasi-DC polarization share the same form parameter of VFT equation, indicating that they have a common origin of microstructure. The origin and correlation of polarization processes could be used to develop a paradigm for rational design of polymer dielectrics to enhance or suppress specific processes for certain purposes.

Influence of Co2+ on the Structure, Conductivity, and Electrochemical Stability of Poly(Ethylene Oxide)-Based Solid Polymer Electrolytes: Energy Storage Devices

In the present work, using a simple solution cast technique, a series of poly(ethylene oxide) (PEO)-doped cobalt chloride (CoCl2) solid polymer electrolytes (SPEs) were successfully prepared. The effect of dopant on the morphology, structure, thermal, and electrochemical stability of the PEO films was systematically studied, and their ionic conductivity was examined. The Fourier transform infrared spectroscopy data provide evidence of the complex nature and existence of various microscopic interactions. The PEO ionic conductivity of 8.6 × 10−8 S cm−1 was found to increase to 3.5 × 10−3 S cm−1 upon the inclusion of 5 wt.% of CoCl2 at 303 K. An effort was made to understand the enhanced conductivity. Several studies were utilized to better understand the fundamental interplay of ion content and segmental motion using the Vogel–Tammann–Fulcher equation with typical investigations based on the fit of temperature-dependent conductivity data. The activation energy (Ea) decreased with increasing dopant concentration. The PCL5 transfer number (tion) was determined to be 0.93, evidence of the ionic nature of the doped electrolyte. Further, the purity and electrochemical stability of SPEs were studied using cyclic voltammetry and chronocoulometry. The thermal analysis showed reduced crystallinity and changes in glass transition and melting temperature at lower temperature, indicating enhanced amorphous content, thus confirming faster ion conduction. These SPEs with excellent electrical performance are promising candidates for electrolytes in solid-state batteries and other energy storage devices.

Crystal Memory near Discontinuous Triacylglycerol Phase Transitions: Models, Metastable Regimes, and Critical Points.

It is proposed that “crystal memory”, observed in a discontinuous solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystalline phases and a liquid TAG phase, in a superheated metastable regime. Such a coexistence has been detected. Solid crystals can act as heterogeneous nuclei onto which molecules can condense as the temperature is lowered. We outlined a mathematical model, with a single phase transition, that shows how the time-temperature observations can be explained, makes predictions, and relates them to recent experimental data. A modified Vogel-Fulcher-Tammann (VFT) equation is used to predict time-temperature relations for the observation of “crystal memory” and to show boundaries beyond which “crystal memory” is not observed. A plot of the lifetime of a metastable state versus temperature, using the modified VFT equation, agrees with recent time-temperature data. The model can be falsified through its predictions: the model possesses a critical point and we outline a procedure describing how it could be observed by changing the hydrocarbon chain length. We make predictions about how thermodynamic functions will change as the critical point is reached and as the system enters a crossover regime. The model predicts that the phenomenon of “crystal memory” will not be observed unless the system is cooled from a superheated metastable regime associated with a discontinuous phase transition.

Determination and modelling of density, viscosity and solubility of (R)-(-)-phenylephrine hydrochloride in methanol + ethyl acetate at (278.15–323.15) K and 0.1 MPa

For further optimizing the pipeline design of continuous crystallizer, in this research work, density, viscosity and solid-liquid equilibria (SLE) solubility of (R)-(-)-phenylephrine hydrochloride (R-PEC) in binary solvent of “methanol (MtOH) + ethyl acetate (EtAC)” were investigated at temperature T = (278.15–323.15) K under pressure p = 0.1 MPa. The results showed that experimental density and viscosity values were negatively related with temperature while the SLE solubility data had positive correlation with the experimental temperature. Moreover, density and viscosity profiles increased with the incremental molarity of R-PEC, similarly, solubility of R-PEC raised along with the mass fraction of MtOH in binary solvents. Hansen solubility parameter (HSP) was applied to investigate the solubility behavior of R-PEC in MtOH+EtAC, four selected solubility parameters could give a logical explanation on R-PEC solubility. By using Mathcad software (Version: 15), the Vogel-Tammann-Fulcher (VTF) equation was employed for the description of density as well as viscosity values. Values of average relative deviation (ARD), multi-correlation coefficient (R2) and root-mean square deviation (RMSD) between experimental data and predicted data showed that VTF equation could provide satisfactory correlations with the experimental data. Besides, solubility values of R-PEHC in selected binary solvent were correlated with three activity coefficient models including Wilson, NRTL (Non-Random Two Liquids) and UNIQUAC (Universal Quasi–Chemical) model by using Mathcad software, the UNIQUAC model were more suitable for correlation with experimental solubility than others in terms of ARD and RMSD. Furthermore, based on the experimental solubility results and regression parameters of UNIQUAC model, thermodynamic properties of mixing and dissolution process were discussed in this work, the results showed that the both processes of R-PEHC in MtOH+EtAC were always spontaneous and entropy driven, the mixing process and part of dissolution process (R-PEHC in MtOH + EtAC at T ≤ 303.15 K) were exothermic. Experimental densities, viscosities, solubility as well as selected models would be very helpful for optimizing the pipeline design (including material selection, size calculation and so on) of continuous crystallizer.

Comparing secondary organic aerosol (SOA) volatility distributions derived from isothermal SOA particle evaporation data and FIGAERO–CIMS measurements

Abstract. The volatility distribution of the organic compounds present in secondary organic aerosol (SOA) at different conditions is a key quantity that has to be captured in order to describe SOA dynamics accurately. The development of the Filter Inlet for Gases and AEROsols (FIGAERO) and its coupling to a chemical ionization mass spectrometer (CIMS; collectively FIGAERO–CIMS) has enabled near-simultaneous sampling of the gas and particle phases of SOA through thermal desorption of the particles. The thermal desorption data have been recently shown to be interpretable as a volatility distribution with the use of the positive matrix factorization (PMF) method. Similarly, volatility distributions can be inferred from isothermal particle evaporation experiments when the particle size change measurements are analyzed with process-modeling techniques. In this study, we compare the volatility distributions that are retrieved from FIGAERO–CIMS and particle size change measurements during isothermal particle evaporation with process-modeling techniques. We compare the volatility distributions at two different relative humidities (RHs) and two oxidation conditions. In high-RH conditions, where particles are in a liquid state, we show that the volatility distributions derived via the two ways are similar within a reasonable assumption of uncertainty in the effective saturation mass concentrations that are derived from FIGAERO–CIMS data. In dry conditions, we demonstrate that the volatility distributions are comparable in one oxidation condition, and in the other oxidation condition, the volatility distribution derived from the PMF analysis shows considerably more high-volatility matter than the volatility distribution inferred from particle size change measurements. We also show that the Vogel–Tammann–Fulcher equation together with a recent glass transition temperature parametrization for organic compounds and PMF-derived volatility distribution estimates are consistent with the observed isothermal evaporation under dry conditions within the reported uncertainties. We conclude that the FIGAERO–CIMS measurements analyzed with the PMF method are a promising method for inferring the volatility distribution of organic compounds, but care has to be taken when the PMF factors are analyzed. Future process-modeling studies about SOA dynamics and properties could benefit from simultaneous FIGAERO–CIMS measurements.

Effect of cation alkyl chain length on photo-luminescence dynamics of ionic liquids containing dicyanoaurate(I) anion

Viscosity and photo-luminescence dynamics of N-alkyl-N-methylpyrrolidinium dicyanoaurate (I) ([Py1n][Au(CN)2]) (n = 4, 6, 8, and 12) and 1-alkyl-3-methylimidazolium dicyanoaurate (I) ([Cnmim][Au(CN)2]) (n = 4, 8, and 12) were studied. The viscosity increased with increasing alkyl chain length for both cations, and the temperature dependence of the viscosity showed a good fit with the Vogel–Fulcher–Tammann equation. Steady-state luminescence of both [Py1n][Au(CN)2] and [Cnmim][Au(CN)2] showed dual luminescent bands at around 370 nm and 460 nm. The band with the shorter wavelength most likely arose owing to fluorescence of the trimer of the anion, and the longer-wavelength band could be assigned to phosphorescence of the linear oligomers of the anion. The relative ratio of the intensity of the fluorescence to that of the phosphorescence of [Py1n][Au(CN)2] was significantly smaller than that of [Cnmim][Au(CN)2]. The luminescent dynamics measured by a streak camera revealed a short lifetime of fluorescence, and the phosphorescence peak shift with time. The phosphorescence peak shift was attributed to two contributions from the amplitudes and the time constants. Based on the dependence on the solvent viscosity and the anion concentration, the slower time constant was assigned to the dynamics of tetramer formation owing to a reaction between the trimer and the monomer. The faster dynamics were assigned to the solvation dynamics, which were accompanied by the structural change of the trimer after intersystem crossing.

Physicochemical and electrochemical properties of the (fluorosulfonyl)(trifluoromethylsulfonyl)amide ionic liquid for Na secondary batteries

In this study, thermal, physical, and electrochemical properties of the ionic liquid electrolyte system, Na[FTA]-[C3C1pyrr][FTA], (FTA‒ = (fluorosulfonyl) (trifluoromethylsulfonyl)amide and C3C1pyrr+ = N-methyl-N-propylpyrrolidinium) have been investigated for Na secondary batteries. The asymmetric FTA‒ structure provides a wide liquid-phase temperature range, especially at low x(Na[FTA]) (x(Na[FTA]) = molar fraction of Na[FTA]) and low temperature range. Glass transition at 170–209 K is the only observed thermal behavior in the x(Na[FTA]) of 0.0–0.4. Temperature dependence of viscosity and ionic conductivity obeys the Vogel‒Tammann‒Fulcher equation, and the correlation between molar conductivity and viscosity follows the fractional Walden rule. The anodic potential limits are above 5 V vs. Na+/Na at 298 and 363 K. The noticeable effects of x(Na[FTA]) are observed in the electrochemical performance of Na metal and hard carbon electrodes. In both cases, a moderate concentration, x(Na[FTA]) of 0.2–0.3, enables favorable charge-discharge behavior. At 363 K, the discharge capacities of the hard carbon electrode at x(Na[FTA]) of 0.3 are 260 and 236 mAh g−1 at the current densities of 20 and 200 mA g−1, respectively. The optimum cycling performance occurs at x(Na[FTA]) = 0.3, providing satisfactory capacity retention and high average Coulombic efficiency.

NePCM Based on Silver Dispersions in Poly(Ethylene Glycol) as a Stable Solution for Thermal Storage.

The main objective of this study is to design and characterize silver suspensions based on poly(ethylene glycol) PEG400, Ag/PEG400, as energy storage media for low-temperature applications. A polyvinylpyrrolidone (PVP) treatment was applied to ~22 nm silver nanoparticles to ensure good stability in poly(ethylene glycol). An array of different experimental techniques was utilized to analyze the molecular mass and purity of base poly(ethylene glycol), morphology of dry PVP-capped Ag nanoparticles, hydrodynamic average size of dispersed Ag particles, as well as thermal stability of PEG400 and Ag/PEG400 dispersions. Samples exhibited good temporal stabilities with average hydrodynamic diameter around 50 nm according to dynamic light scattering analyses. Melting and solidification transitions were investigated in terms of temperature and enthalpy from differential scanning calorimeter (DSC) thermograms. The thermophysical characterization was completed with thermal conductivity (k), dynamic viscosity (η), isobaric heat capacity (Cp), density (ρ), and surface tension (σ) measurements of designed materials using a Hot Disk thermal conductivimeter, a rotational rheometer, a DSC calorimeter working with a quasi-isothermal modulated method, a U-tube densimeter and a drop shape analyzer, respectively. For a nanoparticle loading of only 1.1% in mass, sub-cooling reduced by 7.1% and thermal conductive improved by 3.9%, with almost no penalization in dynamic viscosity (less than 5.4% of increase). Maximum modifications in Cp, ρ, and σ were 0.9%, 2.2%, and 2.2%, respectively. Experimental results were compared with the values provided by using different theoretical or semi-empirical equations. In particular, good descriptions of dynamic viscosity as functions of temperature and nanoparticle volume concentration were obtained by using the Vogel–Fulcher–Tammann equation and a first-order polynomial η() correlation, with absolute average deviations of 2.2% and 0.55%, respectively.

Viscosity of Typical Room-Temperature Ionic Liquids: A Critical Review

Experimental data on viscosity of typical ionic liquids in the liquid state were compiled and critically evaluated. The compilation contains data for 268 ionic liquids from 215 literature references and covers the period from 1998 through the end of December 2018. Equations for corrections of influences of contamination water and residual Cl− on viscosities of a series of typical ionic liquids are established. The influences of experimental methodology and the impurities (i.e., contamination water and residual halide ions) of the samples used on the reported viscosities of these typical ionic liquids are critically evaluated or quantitatively corrected, and the viscosities for these “pure” ionic liquids are recommended. The parameters of the Vogel–Fulcher–Tammann equation for temperature dependence of the recommended viscosities of these ionic liquids were reported. The effects of ionic structures on the viscosity of ionic liquids are presented.