Ionic Fluids Research Articles

Probing the Reorganization of Ionic Liquids' Structure Induced by CO2 Sorption.

The sorption of CO2 is often used to modify the macroscopic properties of liquids and solids. In the particular case of ionic liquids, different from molecular liquids, the sorption of CO2 may not induce volume expansions due to the strong Coulombic interactions between the ions of the fluid. However, a considerable viscosity decrease has been systematically observed. In order to understand the mechanisms of properties modifications in ionic fluids, herein we used Raman spectroscopy to probe the effect of CO2 on the structure of ionic liquids. It is shown that CO2 perturbs the electrostatic interactions between cations and anions, thus inducing a change in the polar domain of ionic liquids. It is observed that ionic liquids having bulkier ions are more prone to be perturbed by CO2 in comparison to ionic liquids having smaller ions. These results reveal new means of controlling the electrostatic forces between the ions and contributes to the mechanistic understanding of the modification of the macroscopic properties of ionic liquids by CO2 sorption.

Novel Paper Based Hand-Fabricated Point of Care Prothrombin Time Sensing Platform Using Pencil and Correction Pen

Cardiovascular diseases (CVDs) are reported to be the leading cause of death worldwide by World Health Organization (WHO) with an approximate of 31% of global deaths. Consequently, it has been noted that the largest sector of population which experiences coagulation or hemostatic imbalances or undergo oral anticoagulation therapy (OAT) are the major sector susceptible to the risk of mortality due to cardiovascular ailments such as atherosclerosis, deep vein thrombosis (DVT), stroke etc. These candidates are prescribed or administered using oral anticoagulation therapy (OAT) and are advised to take the Prothrombin Time (PT) test respectively. Prothrombin Time (PT) analyzers are the type of haemostasis analyzer mainly catering to the coagulation following the extrinsic pathways. Additionally, the candidates under OAT requires routine administration of the coagulation status for proper dosage of warfarin or its derivatives which shares a very narrow therapeutic window. A slight amount of imbalance in the coagulation chemistry can disrupt the cardiovascular functioning, hence a routine monitoring is strongly mandated by cardiac surgeons. It is important to realize a simplified hand held, low cost point of care solution for diagnosing hemostasis or coagulation status to cater both the rural and urban sectors resulting in lower casualties due to coagulation imbalance. The respective work proposes a handheld point of care PT sensing paper sensor using very inexpensive pencil and correction pen and Whattman filter paper. In addition the sensor has enhanced capability of carrying our sensitive detection of coagulation status compared to the existing complex and expensive sensors developed through a variety of methods like screen printing, lithography, flexography printing, wax printing, PDMS printing, stamping etc. The proposed device consists of two pencil marks as electrodes. The device is illustrated in Figure 1. The sensor monitors a change in impedance (resistance) w.r.t time. Blood being an ionic fluid whose chemistry changes with the ionic interactions during the process of coagulation results in a direct correlation of the coagulation process to the respective impedimetric signatures. The synthetic coagulation behavior and the response of the device has been measure using nail paint as an analyte. The points of maximum changes in resistance (first and second) denotes the application of the analyte to the sensor and initiation of coagulation or solidification respectively (shown in Figure 2) from which the coagulation time is further derived. Lab View has been used as an interfacing platform for processing the respective resistive data and generating corresponding coagulation status. Thus, the particular PDE-PAD (pencil drawn electrodes- paper-based analytical devices) can be considered as a promising future device for low cost sensitive detection platform for a point of care PT diagnosis. Figure 1

Green Chemistry principle: Ionic Liquids as a material teaching for vocational students

The development of human civilization is characterized by the type of material used by society. The rapid development of material engineering and technology produces a variety of advanced materials such as smart materials, natural materials, chemical materials, nanomaterials, advanced materials, and environmentally friendly materials. Ionic Liquids (ILs) have criteria that are expected to be environmentally friendly because of their Green Chemistry (GC). The vocational syllabus needs to be reconstructed to be able to adapt this material technological progress. The purpose of this study was to determine the opinions of lecturers on the adoption of Ionic Liquid material teaching materials in vocational education in an effort to deal with the use of environmentally friendly materials that are indispensable in the industrial field. The subject of the study was taken through a purposive sampling method. There were 5 lecturers in one of the private polytechnics. Data collection through questionnaires is intended to determine the views of lecturers on ionic fluid material teaching materials and analyze the material requirements to be adopted into the vocational curriculum. The investigation results show that the interest and willingness of the lecturer to study and disseminate reached a score of 80%, this means that the lecturer needed the Ionic Liquid material. However, the teacher’s understanding score still needs to be improved, so that it is necessary to design an Ionic Liquid teaching material that is interesting and easy to understand by both lecturers and students. The implications of this study can be used as recommendations in learning to be able to enrich the syllabus by adding Ionic Liquid material teaching material as an indispensable teaching material along with technological advances in industry 4.0.

Performance Analysis of Trihexyltetradecylphosphonium Chloride Ionic Fluid under MQL Condition in Hard turning

The current research presents an overall performance-based analysis of Trihexyltetradecylphosphonium Chloride [[CH3(CH2)5]P(Cl)(CH2)13CH3] ionic fluid mixed with organic coconut oil (OCO) during turning of hardened D2 steel. The application of cutting fluid on the cutting interface was performed through Minimum Quantity Lubrication (MQL) approach keeping an eye on the detrimental consequences of conventional flood cooling. PVD coated (TiN/TiCN/TiN) cermet tool was employed in the current experimental work. Taguchi’s L9 orthogonal array and TOPSIS are executed to analysis the influences, significance and optimum parameter settings for predefined process parameters. The prime objective of the current work is to analyze the influence of OCO based Trihexyltetradecylphosphonium Chloride ionic fluid on flank wear, surface roughness, material removal rate, and chip morphology. Better quality of finish (Ra = 0.2 to 1.82 µm) was found with 1% weight fraction but it is not sufficient to control the wear growth. Abrasion, chipping, groove wear, and catastrophic tool tip breakage are recognized as foremost tool failure mechanisms. The significance of responses have been studied with the help of probability plots, main effect plots, contour plots, and surface plots and the correlation between the input and output parameters have been analyzed using regression model. Feed rate and depth of cut are equally influenced (48.98%) the surface finish while cutting speed attributed the strongest influence (90.1%). The material removal rate is strongly prejudiced by cutting speed (69.39 %) followed by feed rate (28.94%) whereas chip reduction coefficient is strongly influenced through the depth of cut (63.4%) succeeded by feed (28.8%). TOPSIS significantly optimized the responses with 67.1 % gain in closeness coefficient.

A new power/cooling cogeneration system using R1234ze(E)/ionic liquid working fluid

A new power/cooling cogeneration system using R1234ze(E)/ionic liquid working fluid

Wettability of ultra-small pores of carbon electrodes by size-asymmetric ionic fluids.

Recently, we studied the phase behavior of ionic fluids under confinement using the classical density functional theory within the framework of the restricted primitive model. The theoretical results indicate that narrowing the pore size may lead to a drastic reduction in the electric double layer capacitance, while increasing the surface electrical potential would improve the ionic accessibility of micropores. In this work, we extend the theoretical investigation to systems containing size-asymmetric electrolytes that may exhibit a vapor-liquid like phase transition in the bulk phase. The effects of pore size and surface electric potential on the phase diagram and microscopic structures of the confined electrolytes were studied over a broad range of parameters. We found that decreasing the pore size or increasing the surface potential could destabilize the liquid phase in micropores, and capillary evaporation could occur regardless of the size asymmetry between cations and anions. Compared to that in a symmetric ionic system, the vapor-liquid phase separation is more likely to take place as the size asymmetry becomes more pronounced. The phase transition would alter the "accessibility" of ions to micropores and lead to coexisting micropores with different surface charge densities as identified by Monte Carlo simulation.

Effect of nanoparticles in molten salts – MD simulations and experimental study

Highlighted experimental studies on nanofluids reveal an anomalous increment in the specific heat capacity (Cp) of these ionic systems when nanoparticles are added. This fact is really important due the applicability of nanofluids in concentrating solar power plants as heat transfer fluid and storage media. These are promising results for the development of high-temperature heat storage applications by enhanced storage capacity materials. The present work focuses on the study of this effect in NaNO3 molten salt doped with SiO2 nanoparticles by molecular dynamics (MD) simulations and Differential Scanning Calorimetry (DSC) experiments. The study shows that for nanoparticles’ concentrations around 1% wt. the Cp increases by 26% compared to pure NaNO3, whereas at higher concentrations the effect disappears. The results approach high agreement between experimental and simulation results and MD simulations reveal that the increase of Cp at low concentrations is explained by the formation of a semi ordered layer of ionic fluid. This layer is rich in Na+ cations, around the nanoparticles whereas the reduction of Cp at concentrations higher than 2% wt. is related to the aggregation of nanoparticles as revealed by Scanning Electron Microscopy (SEM). However, deep experimental results with other materials will be required in order to validate the layering effect.

Electrostatic contribution to colloidal solvation in terms of the self-energy-modified Boltzmann distribution.

Electrostatic interactions make a large contribution to solvation free energy in ionic fluids such as electrolytes and colloidal dispersions. The electrostatic contribution to solvation free energy has been ascribed to the self-energy of a charged particle. Here we apply a variational field theory based on lower bound inequality to the inhomogeneous fluids of one-component charged hard-spheres, thereby verifying that the self-energy is given by the difference between the total correlation function and direct correlation function. Based on the knowledge of the liquid state theory, the self-energy specified in this study not only relates a direct correlation function to the Gaussian smearing of each charged sphere, but also provides the electrostatic contribution to solvation free energy that shows good agreement with simulation results. Furthermore, the Ornstein-Zernike equation leads to a set of generalized Debye-Hückel equations reflecting the Gaussian distributed charges.

Performance characteristics of hardened AISI D2 steel turning: A review

Hard turning is the process of machining hardened steels that have above 45HRC. In metal-manufacturing, hard turning potentially substitutes the grinding process as it possesses lots of benefits like higher metal volume removal rate, less costly, easy to handle, flexible tooling and exhibiting closer surface quality to grinding finish. In the current scenario, plenty of works were reported on hard turning on AISI D2 steel. As hardened D2 steel is popularly used in Die-Punch, Press-tool making industries, automobile industries etc. However, it is worth needed to briefly summarize all the works published on the hard turning of D2 steel. This will provide a platform for the machinist, industrialist, and researchers to further precede their work on D2 steel. In this review work, basically performance characteristics were discussed considering different cutting tools, distinguish coolants and cooling methodologies aspects. MQL works well in hard D2 turning; however, a combination of different coolants like nanofluid, ionic fluid can be utilized in the future. SIC cooling also provides promising results hence it needs to be elaborated more considering different coolants. Also, force and tool condition monitoring can be studied in hard D2 turning using the SIC technique.

Grand canonical simulations of ions between charged conducting surfaces using exact 3D Ewald summations.

We present a useful methodology to simulate ionic fluids confined by two charged and perfectly conducting surfaces. Electrostatic interactions are treated using a modified 3D Ewald sum, which accounts for all image charges across the conductors, as well as the 2D periodicity, parallel to the surfaces. The energy expression is exact, and the method is trivial to implement in existing Ewald codes. We furthermore invoke a grand canonical scheme that utilizes a bias potential, that regulates the surface charge density. The applied bias potential also enables us to calculate individual chemical potentials of the ions. Finally, we argue that our approach leads to a pedagogically appealing description of the Donnan potential, and what it measures in these systems.

Preliminary study on the contribution of osmotic effects for the electrical resistivity of sands

Electrical resistivity of soils can be used to evaluate the level of contamination in soils in geophysical prospection tests. The chemical composition of pore fluid also corresponds to a given water potential, named as osmotic suction. Therefore both electrical resistivity and osmotic suction can be related when soil is saturated. This paper investigates their relationship when the soil is not saturated. The osmotic suction and electrical resistivity were measured for uniform grading size samples of sand prepared with different concentrations of an ionic leachate from a real landfield. Both were measured also for the fluid with the different concentrations. Suction was measured for different degrees of saturation using the ionic fluid for the different concentrations. The soil osmotic suction is similar to the osmotic suction of the pore fluid independently from the degree of saturation, and the differences in electrical resistivity in the saturated samples and pore fluid alone as function of osmotic suction are related by a constant. Although pore fluid composition affects electrical resistivity, when evaluating the electrical resistivity considering the degree of saturation one should pay attention to factors that are related with matric suction instead of osmotic suction.

Towards the Correct Measurement of Thermal Conductivity of Ionic Melts and Nanofluids

Thermophysical properties of engineering fluids have proven in the past to be essential for the design of physical and chemical processing and reaction equipment in the chemical, metallurgical, and allied industries, as they influence directly the design parameters and performance of plant units in the of, for example, heat exchangers, distillation columns, phase separation, and reactors. In the energy field, the search for the optimization of existing and alternative fuels, either using neutral or ionic fluids, is an actual research and application topic, both for new applications and the sustainable development of old technologies. One of the most important drawbacks in the industrial use of thermophysical property data is the common discrepancies in available data, measured with different methods, different samples, and questionable quality assessment. Measuring accurately the thermal conductivity of fluids has been a very successful task since the late 1970s due to the efforts of several schools in Europe, Japan, and the United States. However, the application of the most accurate techniques to several systems with technological importance, like ionic liquids, nanofluids, and molten salts, has not been made in the last ten years in a correct fashion, generating highly inaccurate data, which do not reflect the real physical situation. It is the purpose of this paper to review critically the best available techniques for the measurement of thermal conductivity of fluids, with special emphasis on transient methods and their application to ionic liquids, nanofluids, and molten salts.

Pulsed Electrical Stimulation Enhances Body Fluid Transport for Collagen Biomineralization.

Mechanical loads from physiologic activities such as walking and running generate bioelectricity in bones. By mimicking bioelectricity, external electrical stimulations have also been used therapeutically to stimulate bone-forming cells and, thus, to promote bone regeneration. However, little is known about the physicochemical mechanism(s) by which electrical stimulations drives calcium phosphate mineralization of collagen. Here, we showed that, during in vitro collagen mineralization in the absence of cells, application of pulsed electrical stimulation significantly enhanced the transport of ionic body fluid components through a micrometer-scale channel (∼100-200 μm gap space between the inner surfaces of tube-like collagen scaffolds and a cathode placed inside the collagen scaffolds). The enhanced transport of ionic precursors increased diffusion of the charged precursors from the channel to the inner collagen surface, where bone mineralization was otherwise restricted. The results indicate that pulsed electrical signals can locally accelerate the nucleation of calcium phosphate nanocrystals in or on collagen, allowing us to better control the spatial distribution of the nanocrystals at the microscale. The findings from this study provide insights into the utilization of electrical stimulation for applications such as facilitating bone-fracture healing and designing better bone-specific biomaterials.

Role of base fluid on enhancement absorption properties of Fe3O4/ionic liquid nanofluids for direct absorption solar collector

Different types of ionic liquid-based nanofluids have been studied by the researchers since the last two decades. Most of the studies have focused on the effect of nanoparticles on the enhancement optical properties (absorption, transmittance, scattering, and extinction coefficient) of the corresponding ionic liquid-based nanofluids. However, optical properties of ionic liquid-based fluid have considerable contribution to absorbance in nanofluids. Therefore, it is necessary to study absorption properties of the different ionic liquid-based fluid of corresponding nanofluids to utilize ionic liquid-based nanofluids in solar thermal applications. The effect of the anion and cation radius in the ionic liquid on the enhancement absorption properties of the corresponding nanofluids is investigated. Through the measurement results, we find that as the cation radius or anion radius increases, the transmittances of the corresponding nanofluids decrease sharply, which is beneficial to enhance absorption properties of Fe3O4/ionic liquid nanofluids. At the same time, we also find that the large viscosity increase the stability of ionic liquid nanofluids, which can affect the absorption properties. Understanding the effect of ILs base fluid on enhancement absorption properties of the corresponding nanofluids will pave the road for improving the efficiency for direct absorption solar collectors.

Heat transfer performance of nano-suspension of Al2O3 in ([C4mim][NT f2]) ionic liquid around a circular cylinder

IoNanofluids are a new category of heat transfer fluids synthesized by suspending fine nanoparticles in ionic liquids. These IoNanofluids show superior heat transfer characteristics than conventional nanofluids and are more suitable for medium to high temperature applications. In this study, a numerical analysis of heat transfer performance of nano-suspension of Al2O3 in ([C4mim][NT f2]) ionic fluid around a circular cylinder has been presented. A 2 − D, laminar, steady and forced convective flow around a hot circular cylinder at a constant temperature has been taken into account at 10 ≤ Re ≤ 40 and 0 % ≤ φ ≤ 2.5 %. Governing equations of flow and heat transfer are solved using SIMPLE algorithm based Finite Volume Method (FVM). An unique aspect of this study is the consideration of the influence of temperature on the thermo-physical properties of the IoNanofluids. Heat transfer characteristics are quantified in terms of mean Nusselt numbers and the thermal field around the circular cylinder has been visualized using isotherms. Influence of flow Reynolds number, particle volume fraction and inlet temperature over the local and mean Nusselt numbers has been discussed in detail. Evidently, increase in flow velocity and addition of nanoparticles resulted in heat transfer augmentation. Additionally, heat transfer performance of Al2O3 − ([C4mim][NT f2]) IoNanofluid is compared with the conventional Al2O3 − H2O nanofluid. Comparatively, IoNanofluids outperformed conventional water based nanofluids with 59 % higher heat transfer enhancement ratios. Also, the heat transfer enhancement ratios were noted to be higher at high temperatures. Thus, the new class of cooling liquids (IoNanofluids) are promising working fluids for advanced real time high temperature engineering applications.

Hydrostatic ionic liquid-lubricated fluid film bearing for a rotational electron-beam lithography system

Rotational electron-beam mastering (REBM) systems have been studied with the aim of achieving the high data density necessary to facilitate the fabrication of next-generation optical data media, such as holographic storage. This study reports the design and testing of an ionic liquid (IL)-lubricated hydrostatic spindle system comprising an IL bearing, IL supply pump, and ionic magnetic fluid seal; and its outgassing performance under high-vacuum conditions. An inner vacuum chamber pressure of approximately 10−4 Pa was maintained during rotation of the spindle system. The outgassed products, as measured by a quadrupole mass spectrometer, were primarily generated from the air components in the lubricant IL. The non-repeatable runout in the radial direction, which is an important parameter of REBM accuracy, was 100 nm for a rotational speed of less than 130 min−1. The proposed method can be used for a 100-nm scale REBM device.

Binary mixtures of ionic liquids based on EMIm cation and fluorinated anions: physico-chemical characterization in view of their application as low-temperature electrolytes

Binary mixtures of ionic liquids (ILs) consisting of 1-ethyl-3-methylimidazolium [EMIm]+ cation coupled with fluorinated anions: bis(fluorosulfonyl)imide [FSI]-, bis(trifluoromethanesulfonyl)imide [TFSI]- and tetrafluoroborate [BF4]-, were formulated to obtain ionic fluids which are liquid at low temperature and to understand their properties. The thermal behaviour of [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x) mixtures with various molar ratios of IL components was investigated with differential scanning calorimetry (DSC). They exhibited reduced enthalpy of the phase transitions and lower melting temperature compared to the parent ILs, or only vitrification/devitrification occurring below −90 °C in some cases where x ranges from 0.5 to 0.8, 0.1 to 0.6 or 0.2 to 0.8 for [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x), respectively. For the formulations showing solely a glass transition, considered to be prospective low-temperature electrolytes, the density, viscosity and conductivity values were determined in a wide temperature range. The density demonstrated linear temperature dependence, whilst the dynamic viscosity and ionic conductivity followed the Vogel-Tamman-Fulcher equation. The corresponding Walden plot for pure ILs and their mixtures revealed a high degree of ionicity classifying them as “good ionic liquids” even down to −25 °C. The [EMIm][FSI]x[BF4](1-x) mixtures with x ranging from 0.5 to 0.6 displayed the lowest viscosity and highest conductivity, indicating them as promising electrolytes for IL-based electrochemical capacitors operating at low temperature, down to at least −40 °C.

Analysis of entropy generation in biomimetic electroosmotic nanofluid pumping through a curved channel with joule dissipation

Biomimetic designs are increasingly filtering into new areas of technology in recent years. Such systems exploit characteristics intrinsic to nature to achieve enhanced adaptivity and efficiency in engineering applications. Peristaltic propulsion is an example of such characteristics and in the current article it is explored as a feasible mechanism for deployment in electrokinetic pumping of nanofluids through a curved distensible conduit as a model for a bioinspired smart device. The unsteady mass, momentum, energy and nanoparticle concentration conservation equations for a Newtonian aqueous ionic fluid under an axial electrical field are formulated and simplified using lubrication approximations and low zeta potential (Debye Hückel linearization). A dilute nanofluid is assumed with Brownian motion and thermophoretic body forces present. The reduced non-dimensional conservation equations are solved with the symbolic software, Mathematica 9 via the NDSolve algorithm for velocity, temperature, nano-particle concentration distributions for low zeta potential. An entropy generation analysis is also conducted. The influence of curvature parameter, maximum electroosmotic velocity (Helmholtz-Smoluchowski velocity), inverse EDL thickness parameter, zeta potential ratio and Joule heating parameter on transport characteristics is evaluated with the aid of graphs and contour plots. Temperature profiles are elevated with positive Joule heating and reduced with negative Joule heating whereas the opposite behaviour is observed for the nano-particle concentrations.

A wrinkled graphene and ionic liquid based electric generator for the sea energy harvesting

Sea energy harvesting with carbon nanomaterials is an attractive renewable energy utilization strategy. Recently, studies with the focus on electric energy generation with various graphene-based materials combined with ionic fluids have been reported. However, reliable materials for the energy generation from the mechanical movements of seawater are still a challenge. In the present work, a wrinkled graphene based highly sensitive and stable electric generator has been developed and applied to multiple seawater movements with superior performances. The electric generation mechanism from the mechanical movements of seawater including droplet movement, boundary shift, and continuous flow is explored, and the corresponding electric generation performances are evaluated. The results suggest that the surface wrinkle nanostructure of graphene can enable energy harvesting from continuously flowing ionic liquid due to the drifting of adsorbed ions and ion accumulation in the wrinkles. Based on these results, a miniaturized sea energy harvesting system is fabricated and evaluated with simulated seawater flow and tidal waves. The as-fabricated generator exhibits high sensitivity and high voltage outputs, suggesting its great application potentials as a sea energy harvesting device.

Electronic bandgap of water in the superionic and plasma phases

Water has been proposed to be one of the main compositions of icy giant planets like Neptune and Uranus. Its thermodynamic states and transport properties at extremes are of interest not only to constrain the interior models but also to understand abnormal magnetic fields of planets. The electronic bandgap of water, which significantly influences the ionization ratio and the conductivity, however, is still under debate. In this work, we revisit the shock reflectivity data reported in the literature. By applying a Drude model, the electronic bandgap of water in the superionic and plasma phases is determined to be 4.4 ± 0.2 eV, in contrast to the threshold of 1.25 ± 0.04 eV for free ion generation in the molecular and ionic fluid phases. Interestingly, the bandgap of water does not show a significant tendency of “closure” with the increase in pressure or temperature in the investigated regime, and the bandgap value is consistent with the predicted value of 4–6 eV by the density functional theory assuming a hybrid Heyd-Scuseria-Ernzerhof functional [Millot et al., Nat. Phys. 14, 297–302 (2018)]. The electronic bandgap and the energy threshold determined in this work provide essential parameters for estimating the conductivity along the radius of Neptune and Uranus and will promote our understanding of the origin of the abnormal magnetic fields.