Ionic Liquids as Performance Ingredients in Space Lubricants

Tribological characteristics of two imidazolium-based room temperature ionic liquids (RTILs), 1-hexyl-3-methylimidazolium tetrafluoroborate, and 1-hexyl-3-methylimidazolium hexafluorophosphate were investigated under high vacuum conditions. Viscosity–temperature characteristics and thermogravimetric characteristics of these compounds were also investigated. Imidazolium-based RTILs have relatively good viscosity–temperature characteristics that are comparable to those of multiply-alkylated cyclopentane (MAC). Thermogravimetric results showed that ionic liquids have high thermal stability and low vapor pressure. Ionic liquids showed low friction and low wear rate under high vacuum conditions, and high load-carrying capacity was observed.

Wear durability study on self-lubricating SU-8 composites with perfluoropolyther, multiply-alkylated cyclopentane and base oil as the fillers

Fabrication and tribological properties of a multiply-alkylated cyclopentane/reduced graphene oxide composite ultrathin film

Room temperature ionic liquids comprise an unique class of solvent composed of organic and inorganic-based ions that are molten under ambient conditions. They are characterised by high solvent polarity and low vapour pressure, and can be tailored to have specific physical and chemical properties. Consequently, there has been great interest in exploiting these attributes to accelerate and control organic reactions. One such reaction, the Diels-Alder reaction, is an important [4+2] cycloaddition reaction used extensively in the preparation of cyclic and heterocyclic compounds. Understanding the factors involved in the enhancing this reaction in ionic liquids remains a subject of intense interest and the centrepiece of the dissertation. The objective of the research is to explore the Diels-Alder cycloaddition reaction in ionic liquids, with a view of developing high effective reactions systems, that operate under mild reaction conditions. The role that ionic liquid media plays in facilitating the Diels-Alder reaction is discussed. A range of physical and chemical modes of activating the reaction are discussed including pressure, the application of Lewis acid catalysts, microwave irradiation and ultrasound sonication and a comparison on the various modes of activation is provided. Importantly, the results of this study can lead to a better understanding of the ionic liquids as well as their utilization for other organic reactions.

INTRODUCTION The unique properties of ionic liquids (ILs) i.e. high thermal and chemical stability, non-flammability, low vapor pressure, and wider electrochemical window compared to traditional solvents, as well as the prospect that they can be tailored or custom designed for specific requirements make them all the more interesting. In recent years, ILs with organic cations have been suggested for electrolyte applications. Ionic liquids seems to be promising electrolytes in protonic systems as they exhibit good proton conducting properties.The motivation for the presented research was dictated by the growing interest in the field of the use of ionic liquids as electrolytes in metal-hydride batteries (Ni-MH) and other proton batteries (eg. based on the Si anode). The electrolytes based on ionic liquids can reduce the problem of the anode material (eg. AB5 alloy) corrosion in aqueous basic solutions, which may result in the improvement of the operation parameters of the proton batteries.The focus of this study was to check the applicability of ILs as non-aqueous electrolytes through the investigation of hydrogen sorption in Pd limited volume electrode (Pd-LVE) and AB5-LVE. Since protic ILs and their mixtures with other solvents have been recently proposed as electrolytes in metal-hydride batteries, Pd-LVE is a very good model system to carry out the preliminary study of hydrogen electrosorption in ionic liquids in view of the further research with the use of multicomponent alloys. EXPERIMENTAL The electrochemical experiments were conducted in selected, commercially available protic and aprotic ionic liquids (i.a. diethylmethylammonium triflate (DEMA-TFO), ethylammonium nitrate (EAN), 1-ethyl-3-methylimidazolium methanesulfonate (EMIm-MS) under inert gas (Ar) using three-electrode system. Pd-LVE (ca. 0.5 μm thick) or AB5-LVE (ca. 50 μm thick) was a working electrode, Ag wire was a quasi-reference electrode, and Pt or Au spiral was an auxiliary electrode. Pd-LVE were obtained electrochemically from the PdCl2 aqueous solution. AB5 alloy (LaMMNi4.1Al0.3Mn0.4Co0.45) was obtained from VARTA Microbatteries GmbH. To aprotic ionic liquid (EMIm-MS) organic acid of the same anion as in the IL (methanesulfonic acid, HMS) was added as a source of hydrogen and to increase the ionic conductivity of the obtained electrolyte. Cyclic voltammetry (CV), chronoamperometry (CA) and chronopotentiometry (CP) techniques were used to perform the electrochemical measurements. The electrodes were subjected to a hydrogen pretreatment procedure (HPP) and standard hydrogen cyclic voltammetry electrosorption experiment to obtain hydrogen absorption isotherms. RESULTS AND DISCUSSION It was observed, that the reversibility of the hydrogen sorption in Pd is significantly lower in ILs than in aqueous solutions, which may be caused by hindered proton transport due to few reasons. The first one is the high viscosity of IL, the second one is the difference of proton source, and finally the possible interactions of IL ions with the Pd electrode. Multiple hydrogen sorption in ILs (HPP) increases the reversibility of the investigated process. Preliminary HPP performed in aqueous solution of sulfuric acid facilitates further hydrogen sorption only in some cases (i.a. in EAN). Thus, it was found that the rate of hydrogen absorption is controlled rather by surface than the bulk processes. The maximum hydrogen sorption capacity (H/Mmax) obtained for Pd in protic IL (i.e. DEMA-TFO) and aprotic IL with addition of organic acid (EMIm-MS + 0.5 M HMS) is comparable with those obtained in aqueous solutions of acids and bases, reaching the value of ca 0.7. Our preliminary studies of hydrogen sorption in the AB5 alloy in a mixture of an aprotic IL with the organic acid (EMIm-MS + 1 M HMS) revealed that, as in case of Pd-LVE, the electrochemical reversibility of this process is much lower in comparison with the electrosorption measurements performed in concentrated base (Fig.1), which is due to the significant difference in ion conductivity and dynamic viscosity of the tested electrolytes. Fig. 1. Cyclic voltammetry behavior of AB5 electrode in EMIm-MS + 1 M HMS, inset: cyclic voltammetry of AB5 electrode in 6 M KOH; first cycles; 2 mVs-1. CONCLUSIONS Examined protic and aprotic ionic liquids can be effectively used as electrolytes in the hydrogen sorption process as we demonstrated by the exemplary Pd-LVE electrode. The max. H/Pd ratios obtained for DEMA-TFO and nitrate protic ILs are similar (0.6-0.7) and comparable with those measured in aqueous solutions of acids and bases. Hydrogen electrosorption from aprotic ionic liquids (eg. in EMIM-MS) with different concentration of acid gives ability to tune the maximum hydrogen capacity. The max. H/Pd ratios obtained for EMIm-MS (acid concentration ca. 0.5 M) equals to ca. 0.74 (this is the same value that was obtained for this type of electrode from acidic aqueous media). Figure 1

Ionic liquids (ILs) are chemical substances with good solubility and low vapor pressure because they are ionized and therefore charged. ILs may damage ecosystem due to their good water solubility. Toxicological studies for individual ILs. Major constraint in ILs ecotoxicology is that risk cannot be quantified by risk quotient methods because of unavailability of exposure assessment data. At present, only limited information is available about the impacts of ILs to aquatic ecosystems. The main objective of the current work is to use statistical methods to available literature on acute toxicity data of ILs to assess potential ecotoxicological risks when the ILs do come into industrial use. Probabilistic ecotoxicological risk assessment (PETRA) method was adopted by using Chemical Toxicity Distributions (CTDs) and Species Sensitivity Distributions (SSDs). SSDs has been used to derive threshold values below which the ecosystem and its biotic components could be protected from the adverse effect of ILs. CTDs has been used to estimate the probability of finding ILs with an effect below a calculated concentration which is considered to be safe environmental concentration. Acute toxicity data were collected from the literature on the acute toxicity of four bacterial pathogens Aeromonas hydrophila, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus. CTD method was applied to assess the distribution of toxicities of group of IL to individual species. The SSD method was applied to estimate guideline values (GVs) to estimate different level of protection of bacterial species from ILs. Imidazolium chloride and bromide ILs were reported to pose more than 5 % risk towards bacteria. Out of the four bacterial strains, E coli was reported to be potentially at higher risk because of highest sensitivity when exposed towards ILs. The risk posed was five percent which is acceptable level of risk.

Room temperature ionic liquids (RTILs) are solvent-free liquids comprised of densely packed cations and anions. The low vapor pressure and low flammability make ILs interesting for electrolytes in batteries. In this work, a new class of ionic liquids were formed for rechargeable aluminum/graphite battery electrolytes by mixing 1-methyl-1-propylpyrrolidinium chloride (Py13Cl) with various ratios of aluminum chloride (AlCl3) (AlCl3/Py13Cl molar ratio = 1.4 to 1.7). Fundamental properties of the ionic liquids, including density, viscosity, conductivity, anion concentrations and electrolyte ion percent were investigated and compared with the previously investigated 1-ethyl-3-methylimidazolium chloride (EMIC-AlCl3) ionic liquids. The results showed that the Py13Cl–AlCl3 ionic liquid exhibited lower density, higher viscosity and lower conductivity than its EMIC-AlCl3 counterpart. We devised a Raman scattering spectroscopy method probing ILs over a Si substrate, and by using the Si Raman scattering peak for normalization, we quantified speciation including AlCl4−, Al2Cl7−, and larger AlCl3 related species with the general formula (AlCl3)n in different IL electrolytes. We found that larger (AlCl3)n species existed only in the Py13Cl–AlCl3 system. We propose that the larger cationic size of Py13+ (142 Å3) versus EMI+ (118 Å3) dictated the differences in the chemical and physical properties of the two ionic liquids. Both ionic liquids were used as electrolytes for aluminum–graphite batteries, with the performances of batteries compared. The chloroaluminate anion-graphite charging capacity and cycling stability of the two batteries were similar. The Py13Cl–AlCl3 based battery showed a slightly larger overpotential than EMIC-AlCl3, leading to lower energy efficiency resulting from higher viscosity and lower conductivity. The results here provide fundamental insights into ionic liquid electrolyte design for optimal battery performance.

Over the years, ionic liquids (ILs) have become an essential tool in chemistry owing to their various applications such as catalysis, electrochemistry, pharmaceuticals, nanotechnology, biotechnology, separation and extraction processes, amongst many others. With respect to the above applications, ionic liquids have desired properties like low flammability, low vapour pressure, high thermal and chemical stability, good electrical conductivity and low volatility. Ionic liquids possess the ability of being “tailored” to meet specific needs for different applications due to the flexibility in their physicochemical properties. This is done by replacing or substituting the side chain length of cation or anion structure.This project focused on the thermodynamic as well as thermo-physical parameters of two-component combinations of ionic liquids (ILs) and carboxylic acids (ethanoic or propanoic or butanoic or pentanoic or 2-methylpropanoic acids) which were investigated at several temperatures. The ionic liquidsutilized for this research investigation includes: •1-ethyl-3-methylimidazolium ethylsulphate ([EMIM]+[EtSO4]−)•1-butyl-3-methylimidazolium methylsulphate ([BMIM]+[MeSO4]−)•N-2′, 3′-epoxypropyl-N-methyl-2-oxopyrrolidinium salicylate ([EPMpyr]+[SAL]−)•N-2′, 3′-epoxypropyl-N-methyl-2-oxopyrrolidinium acetate ([EPMpyr]+[OAC]−)•N-2′, 3′-dihydroxypropyl-N-methyl-2-oxopyrrolidinium chloride ([PYR-PDO]+[Cl]−)Density and speed of sound measurements were examined obtained for the following two component systems: {([EMIM]+[EtSO4]−) + pentanoic or 2-methylpropanoic acid, ([BMIM]+[MeSO4]−) + ethanoic or propanoic acid, ([EPMpyr]+[SAL]−) + ethanoic or propanoic acid, [EPMpyr]+[OAC]−+ propanoic or butanoic acid, [PYR-PDO]+[Cl]−+ ethanoic or propanoic or butanoic acid) throughout the concentration of the ionic liquid at T= (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15) K). Parameters such as excess molar volumes (VmE), isentropic compressibilities (ks) is entropic compressibilities deviation (Δks) and intermolecular free length (Lf) were computed from the measured values of densities and speeds of sound.The experimental data revealed that densities and speeds of sound value decrease with rise in temperature. Furthermore, excess molar volumes and is entropic compressibility deviation for all systems studied were found to be negative and increased with a rise in temperature. The negative outcomes obtained for excessmolar volumes of all the two-component systems studied suggest chemical interactions occur between unlike molecules in the component mixtures. These interactions are ascribed to formation of weak bonds and electron donor and acceptor complexes. Furthermore, the interaction interstices of IL gave some space for the acids to achieve structural arrangement.The Redlich-Kister equation was used to correlate the derived parameters; VmE, Δks and Lf whereas a least squares method was utilized in determining the fitting parameters and standard errors. These was done to check the precision of the measured data and the standard deviations which show moderately lower values for VmE, Δks and Lf with the examined temperatures for all the binary systems.

Descriptive and predictive models for Henry’s law constant of CO2 in ionic liquids: A QSPR study

Ionic liquids (ILs) are a promising medium to assist in the advanced (chemical and biological) recycling of polymers, owing to their tunable catalytic activity, tailorable chemical functionality, low vapor pressures, and thermal stability. These unique physicochemical properties, combined with ILs' capacity to solubilize plastics waste and biopolymers, offer routes to deconstruct polymers at reduced temperatures (and lower energy inputs) versus conventional bulk and solvent-based methods, while also minimizing unwanted side reactions. In this Viewpoint, we discuss the use of ILs as catalysts and mediators in advanced recycling, with an emphasis on chemical recycling, by examining the interplay between IL chemistry and deconstruction thermodynamics, deconstruction kinetics, IL recovery, and product recovery. We also consider several potential environmental benefits and concerns associated with employing ILs for advanced recycling over bulk- or solvent-mediated deconstruction techniques, such as reduced chemical escape by volatilization, decreased energy demands, toxicity, and environmental persistence. By analyzing IL-mediated polymer deconstruction across a breadth of macromolecular systems, we identify recent innovations, current challenges, and future opportunities in IL application toward circular polymer economies.

The enormous emission of carbon dioxide (CO2) from industries has triggered a series of environmental issues. In recent years, ionic liquids (ILs) as novel absorbents are widely used for CO2 capture owing to their low vapor pressure and tunable structures. IL‐modified adsorbents have the advantages of both ILs and porous supports, such as high CO2 selectivity and high specific surface area, which are novel agents to capture CO2 with broad application prospects. In this review, more than 140 IL‐modified adsorbents for CO2 capture in recent years were systematically summarized. The types of ILs including conventional ILs and functionalized ILs on CO2 separation performance of different IL hybrid adsorbents, and their adsorption mechanisms were also discussed. Finally, future perspectives on IL‐modified adsorbents for CO2 separation were further posed.

Ionic liquids (ILs) represent a real alternative for electrochemical applications due to their remarkable characteristics, namely a very low vapour pressure, low flammability, high thermal stability, wide potential window and high ionic conductivity. In this work, Nyquist plot and impedance spectroscopy at room temperature is proposed as an alternative method to obtain the ionic conductivity for ionic liquids by using an Agilent HP 4284A RLC precision meter. For this propose, the IL 1-butyl-3-methylimidazolium tetrafluoroborate (C4C1Im BF4) was selected and results were compared with the previously obtained from the conductimeter CRISON GLP31.

Ionic liquids (ILs) are low temperature molten salts, that is, a salt in the liquid state. ILs used to present a very low vapour pressure and this property makes of the ILs key materials for the development of a wide variety of emerging technologies. The stability of ILs at high temperatures (several hundred degrees), low combustibility, and even the relatively high viscosity of some of them compared to conventional solvents, are characteristic of interest for some applications. Due to the large diversity of ILs components, they may present wide structural variations which can be used to design the IL with more adequate properties for a particular application. These applications might include new types of lubricants and fluids for thermal engines, electrodeposition, energy and CO2 capture devices, biomimetics, double layer capacitors,.....in fact, the scientific and technological importance of the ILs spans nowadays to a wide range of applications [1-5]. Among the energy devices, polymer-electrolyte membranes for fuel cell application are under development as a way to reduce global warming and energy cost and ILs incorporation in the structure of Nafion, a typical membrane for fuel cell use, is under study [6-8]. Since transport properties of porous and dense membranes can be modified with the addition of substances which could favour/reject the pass of some of the particles or ions in a mixture, the incorporation of a particular IL in the structure of a membrane may increase its selectivity and/or specificity. Chemical characterization and determination of electrical parameters for different ILs as well as the changes associated to water incorporation, a subject of interest for different electrochemical applications, is considered in this work. Moreover, due to the importance that membrane separation technology has nowadays, modification of membranes with different structures by incorporation of RTILs or IL-cations and their effect on mass and charge transport is also presented. Ionic liquids, membranes and membranes/IL-modified samples were chemically characterized by X-ray photoelectron spectroscopy (XPS). This technique allows the

The present paper is primarily concerned with the synergistic effects of polar and organic sulfur compounds on the wear and surface roughness under boundary-lubrication (BL) conditions. The effects of lubricants containing the above two types of additives on the wear and the roughness of worn surface in a steel/steel sliding system have been investigated using a four-ball wear tester in air and argon atmospheres. In air, the combination of a fatty acid and a sulfur compound gives less wear and a smoother surface than would the sulfur compound alone in test run on worn surfaces. This surface smoothing is concerned with the friction modifications of surface caused by supplying binary additives and promoting elastohydrodynamic lubrication (EHL). In argon, on the contrary, it seems that the chemical reaction of sulfidized film with fatty acid causes the excessive wear. To control the evaporation of organic sulfur compounds and the effect of oxygen, a high-pressure-differential thermal analysis (HPDTA) was applied to measure the reactivity of various sulfur compounds with iron in inert gas. The results obtained by HPDTA may support those in the wear test. Also in such system, the wear and the roughness of worn surface are not only affected significantly by the reactivity and combination of additives, but also by oxygen.

Recent developments in sustainable corrosion inhibition using ionic liquids: A review