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  • 101. Shah, Faiz Ullah
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Antzutkin, Oleg
    Synthesis, physicochemical, and tribological characterization of S-Di-n-octoxyboron-O,O'-di-n-octyldithiophosphate2009In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 1, no 12, p. 2835-2842Article in journal (Refereed)
    Abstract [en]

    Dialkyldithiophosphates (DTPs) of zinc(II), copper(II), and other metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Among these DTP compounds, zinc dialkyldithiophosphates (ZnDTPs) are the most common additives extensively used for more than 60 years. These additives form a protective film on steel surfaces and, thus, control friction and reduce wear. However, ZnDTPs contain zinc and large amounts of phosphorus and sulfur, which impair the environment, both directly and indirectly, by adversely affecting the performance of catalytic converters of various automobiles. For this reason, environmental legislation imposes limitations on concentrations of phosphorus, sulfur, and zinc in the lubricants. In this work, we report on zinc-free S-di-n-octoxyboron-O,O′-di-n-octyldithiophosphate (DOB-DTP) lubricant additive with amount of phosphorus and sulfur reduced by half in a molecule as compared with ZnDTPs. DOB-DTP was synthesized by a reaction in two steps under inert nitrogen atmosphere. The final product, a viscous liquid, was characterized by the elemental analysis, FT-IR, multinuclear 1H, 13C, 31P, and 11B NMR spectroscopy and thermal analyses. Tribological performance of a mineral oil with this new additive was evaluated in comparison with O,O′-di-n-butyl-dithiophosphato-zinc(II) (ZnDTP) using a four-ball tribometer. The surface morphology and the elemental composition of the tribofilms were characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). The results show that DOB-DTP has a considerably better antiwear performance and higher stability of the coefficient of friction with time as compared with ZnDTP. Both phosphorus and sulfur were detected by the EDS on the worn steel surfaces at all concentrations of additives in the base oil.

  • 102. Shah, Faiz Ullah
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Antzutkin, Oleg N.
    Boron in Tribology: From Borates to Ionic Liquids2013In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 51, no 3, p. 281-301Article, review/survey (Refereed)
    Abstract [en]

    Boron compounds are widely used in a range of tribological applications such as friction modifiers, antioxidants, antiwear additives, and in many cases as environmentally friendly lubricants. The chemical nature and structure of boron compounds provide multifunctionality. They are used as (1) solid lubricants such as boric acid and hexagonal boron nitride, (2) liquid lubricants such as ionic liquids, (3) lubricant additives such as borate derivatives of various organic and inorganic compounds, and (4) coatings such as cubic boron nitride and different metal borides. Boron is also one of the most favorable elements for coatings and thin films in biotribological and biomedical applications. This review outlines the growing role of boron in lubrication over the past several decades, summarizes the main findings, and identifies future challenges related to boron chemistry.

  • 103. Shah, Faiz Ullah
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Höglund, Erik
    Lindberg, Mats
    Antzutkin, Oleg N.
    Interfacial Antiwear and Physicochemical Properties of Alkylborate-dithiophosphates2011In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, no 4, p. 956-968Article in journal (Refereed)
    Abstract [en]

    Boron compounds have become of interest in tribology because of their unique tribochemical and tribological properties. At the same time, dialkyldithiophosphates (DTPs) of transition metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Because of the environmental pollution and health hazards of these compounds, ashless compounds with reduced amounts of sulfur and phosphorus are desirable. This work reports on the synthesis, characterization, and tribological properties of a new class of compounds, alkylborate-dithiophosphates. This class combines two high-iron-affinity surface active groups, borate and dialkyldithiophosphate, into a single molecule. The final products, viscous liquids, were characterized by FT-IR, multinuclear 1H, 13C, 31P, and 11B NMR spectroscopy and thermal analyses. Residues of one representative compound from this class, DPB-EDTP, after thermal analyses were additionally characterized by multinuclear 13C, 31P and 11B MAS and 31P CP/MAS NMR spectroscopy. Solid-state NMR data suggest that a dominant part of the solid residue of DPB-EDTP consists of borophosphates. Antiwear and friction properties of a mineral oil with these novel additives were evaluated in a four-ball tribometer in comparison with O,O?-di-n-butyl-dithiophosphato-zinc(II), Zn-BuDTP, as a reference lubricant additive. The surface morphology and the elemental composition of the tribofilms were characterized using scanning electron microscopy with energy-dispersive X-rays spectroscopy (SEM/EDS). The results show that alkylborate-dithiophosphates, with substantially reduced amounts of sulfur and phosphorus compared with Zn-BuDTP, have considerably better antiwear and friction performance.

  • 104. Shah, Faiz Ullah
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    MacFarlane, Douglas R.
    Somers, Anthony
    Forsyth, Maria
    Antzutkin, Oleg N.
    Novel halogen-free chelated orthoborate-phosphonium ionic liquids: synthesis and tribophysical properties2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 28, p. 12865-12873Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis, characterisation, and physical and tribological properties of halogen-free ionic liquids based on various chelated orthoborate anions with different phosphonium cations, both without halogen atoms in their structure. Important physical properties of the ILs including glass transition temperatures, density, viscosity and ionic conductivity were measured and are reported here. All of these new halogen-free orthoborate ionic liquids (hf-BILs) are hydrophobic and hydrolytically stable liquids at room temperature. As lubricants, these hf-BILs exhibit considerably better antiwear and friction reducing properties under boundary lubrication conditions for steel-aluminium contacts as compared with fully formulated (15W-50 grade) engine oil. Being halogen free these hf-BILs offer a more environmentally benign alternative to ILs being currently developed for lubricant applications.

  • 105. Sherrington, I.
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Tribotronics: The advent of a new paradigm for tribological systems?2013In: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, p. 3200-3203Conference paper (Refereed)
  • 106.
    Shu, Ju
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Harris, Kathryn
    KTH, School of Industrial Engineering and Management (ITM).
    Munavirov, B.
    Westbroek, R.
    Leckner, J.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM). Soete Laboratory, Ghent University, B-9000 Ghent, Belgium.
    Tribology of polypropylene and Li-complex greases with ZDDP and MoDTC additives2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 118, p. 189-195Article in journal (Refereed)
    Abstract [en]

    The influence of thickener and additive interactions on grease lubricating performance is examined. Polypropylene and lithium complex thickened (Li-complex) greases were tested both as neat greases and with a 2 wt% addition of ZDDP and/or MoDTC. A combination of ZDDP and MoDTC in the polypropylene grease provided the lowest friction with greater longevity compared to the Li-complex grease with the same additives, independent of sliding speed, contact pressure, temperature or type of sliding: continuous vs. reciprocating. The additive combination of ZDDP and MoDTC provided the best antiwear performance in both greases. Depending on the grease sample type, EDS revealed the presence of iron, zinc, phosphorous, sulfur, and molybdenum within the tribofilms.

  • 107. Simmons, G. F.
    et al.
    Aidanpää, J. -J
    Cervantes, M.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Operational transients in the guide bearings of a 10 MW Kaplan turbine2013In: International journal on hydropower and dams, ISSN 1352-2523, Vol. 20, no 5, p. 94-100Article in journal (Refereed)
    Abstract [en]

    Experiments using a 10 MW Kaplan hydropower machine with a PowerFormerTM generator (the Porjus U9 research machine) are described. This machine has an extensive array of sensors to determine oil film thickness, pad tilting, pad load and oil temperature in all three guide bearings, as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all three guide bearings are examined during both steady-state and transient operation.

  • 108. Simmons, Gregory F.
    et al.
    Cha, Matthew
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Aidanpaa, Jan-Olov
    Cervantes, Michel J.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Department of Mechanical Construction and Production, Ghent University, Belgium.
    Steady state and dynamic characteristics for guide bearings of a hydro-electric unit2014In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 228, no 8, p. 836-848Article in journal (Refereed)
    Abstract [en]

    Experiments are conducted using a 10-MW Kaplan hydropower machine which is outfitted with an extensive array of sensors to determine oil film thickness, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all journal bearings are compared to a commercial rotor dynamics model and results for the central journal bearing are compared to a multi-physics model to provide insight into the machine's steady state and dynamic characteristics and their variations during normal operation.

  • 109. Simmons, Gregory F.
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Mueller, Michael
    Byheden, Åke
    Prakash, Braham
    Extending performance limits of turbine oils2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 52-60Article in journal (Refereed)
    Abstract [en]

    New turbine oils providing both extremely high viscosity index (VI) and improved boundary/mixed lubrication performance are investigated. Comparisons are made in both laboratory scale testing using typical journal bearing sliding surfaces (steel and white metal) and full scale testing using a hydrodynamic journal bearing test machine. The results from these studies demonstrate the effectiveness of new, high VI, turbine oils for reducing friction at machine startup and improving performance during full film operation.

  • 110. Simmons, Gregory F.
    et al.
    Kuznetsov, Evgeny
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Powerplant lubricant selection for improved efficiency and environmental impact reduction2010In: Proceedings of the ASME 2010 International Mechanical Engineering Congress & Exposition, IMECE 2010, 2010Conference paper (Other academic)
    Abstract [en]

    Computational models were used to optimize bearing per-formance by adjusting a number of lubricant properties. Thiscomputational optimization showed that the most beneficialcharacteristics to hydrodynamic bearing operation were highviscosity index (VI) and high specific heat capacity. Four envi-ronmentally adapted synthetic lubricants were developed to pro-vide these characteristics including: ISO VG32 with 259 VI, ISOVG22 with 245 VI, ISO VG22 with 336 VI, and ISO VG15 with226 VI. A full scale bearing test machine was then operated withthese lubricants in addition to mineral based turbine oils, ISOVG68 with 103 VI and ISO VG32 with 105 VI, to determine theeffect on bearing performance and to validate the models. Thenew lubricants reduced bearing power loss by up to 20% and sig-nificantly reduced bearing temperatures with somewhat reducedfilm thickness. The machine was then operated to provide equiv-alent minimum viscosity with the new lubricants by varying inlettemperature, finding that changes in power loss were less sub-stantial with equivalent minimum viscosity.Comparison of simulated and experimental results led todevelopment of a simple, practical method to estimate benefitsand operational parameters for lubricants based on viscositygrade, viscosity index and a simplified description of the machine’s bearings. Other, less tangible, factors considered arebio-degradeability and impact of power loss reduction.

  • 111. Simmons, Gregory F.
    et al.
    Varela, Alejandro Cerda
    Santos, Ilmar Ferreira
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Dynamic characteristics of polymer faced tilting pad journal bearings2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 74, p. 20-27Article in journal (Refereed)
    Abstract [en]

    Dynamic characteristics of polymer faced tilting pad journal bearings are presented. Investigations are conducted using a single pad, load on pad configuration over a range of shaft speeds and loads. Two polyether ether ketone (PEEK) faced pads, one polytetrafluoroethylene (PTFE) faced pad and two entirely PEEK pads are investigated to determine the effect of varying mean bearing pressure and pivot characteristics as well as different material properties of the polymer layer. Experimental results indicate increased damping and decreased stiffness and slightly increased oil film temperature for entirely PEEK pads compared to pads with a PEEK lining and steel backing. Similar effects were observed by using a softer (PTFE) pad liner with a steel backing.

  • 112. Simmons, Gregory
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    A comparative study of mineral-based and environmentally adapted lubricants with viscosity index improvers in journal bearings2009In: Proceedings of the World Tribology Congress 2009: Sunday 6th to Friday 11th, September, 2009, Kyoto, Japan, 2009, Vol. 570, p. 570-Conference paper (Refereed)
    Abstract [en]

    While hydropower plant efficiency is exceptional, very little has been done to further improve its already high level of efficiency. In this regard, the bearings stand out as one of the major sources of losses in the plant that has potential for significant improvements with relatively little investment. One way to reduce losses while maintaining operating characteristics is to change lubricating oil to a higher viscosity index (VI) lubricant with a lower viscosity base oil. Studies showed that the thermal performance of mineral-based oils could be improved through the use of VI improvers to match that of synthetic lubricants. Another study investigated the case of polyalphaolefin-based lubricants, which found that lubricant with high VI provides performance equivalent to higher viscosity lubricants with lower VI ratings. Environmentally adapted lubricants, because of their inherent higher VI, provided higher viscosity in the region of lowest film thickness and lower viscosity in the rest of the bearing than standard mineral oil-based lubricants. This reduction in viscosity throughout the bearing led to a measurable reduction in power losses in the bearing system while maintaining desirable film thickness. Lubricants studied in this testing include industry standard VG32 mineral based turbine oil as a reference and synthetic ester and mineral based lubricants enhanced with polymer based VI improver additives. 

  • 113. Simmons, Gregory
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Synthetic Lubricants in Hydrodynamic Journal Bearings: Experimental Results2011In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 42, no 1, p. 109-115Article in journal (Refereed)
    Abstract [en]

    Synthetic lubricants and additives have seen many major improvements in recent years. However, very little is known about the performance peculiarities of these new lubricants in actual machines. To fill this gap, a new full-scale hydro-dynamic journal bearing test rig has been constructed to evaluate the behavior of conventional and new bearing designs, synthetic lubricants and variations in operating parameters. This test rig’s bearing has diameter 180 mm with measuring capabilities including continuous film thickness and film pressure as well as temperature. The new machine was used to compare a number of synthetic lubricants to mineral based lubricants, finding that performance of the synthetic lubricants was superior to their mineral based counterparts of much higher viscosity grade. These tests showed that high viscosity index (VI) synthetic lubricants had higher viscosity in the region of maximum pressure and lower viscosity elsewhere in the bearing than similar mineral based lubricants. This reduction in viscosity in low pressure zones was found to produce a measurable reduction in friction and power loss in the bearing system. This paper provides comparative performance results of several formulations of current and future turbine oils from measurements of losses, oil film thickness, and temperature under a range of operating parameters. Lubricants tested include ISO VG68 and VG32 mineral based turbine oils (VG68 and VG32), ISO VG32 synthetic ester based oil (SE32), two ISO VG22 synthetic ester based oils (SE22 and SV22), and ISO VG15 synthetic ester based oil (SE15). It was found that SE32 and VG68 provided similar performance at lower speeds while SV22 provided similar performance to VG68 at the highest speed. Likewise, SE22 and SV22 provided similar performance to VG32 at low speeds while SE15 provided similar performance to VG32 at medium to higher speeds. Generally, the results demonstrate the potential for replacing mineral based lubricants with high performance synthetic lubricants of significantly lower viscosity grade without sacrificing bearing safety.

  • 114. Taher, Mamoun
    et al.
    Shah, Faiz Ullah
    Filippov, Andrei
    de Baets, Patrick
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Department of Mechanical Construction and Production, Ghent University, Belgium .
    Antzutkin, Oleg N.
    Halogen-free pyrrolidinium bis(mandelato) borate ionic liquids: some physicochemical properties and lubrication performance as additives to polyethylene glycol2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 58, p. 30617-30623Article in journal (Refereed)
    Abstract [en]

    This work reports on the synthesis and physicochemical characterisation of novel halogen-free boron containing ionic liquids (hf-BILs) with dialkylpyrrolidinium cations [C(n)C(1)Pyrr](+), n = 4-14, and bis(mandelato) borate anion [BMB](-). All the synthesised compounds are liquids at room temperature. It was found that the thermal properties and density of these hf-BILs are affected by the length of the longest alkyl chain connected to the nitrogen atom in the pyrrolidinium cations. Differential scanning calorimetry measurements revealed that glass transition temperatures of these ionic liquids are in the temperature range from 218 to 241 K. Interestingly, the glass transition temperatures follow the "odd-even" effect related to the number of carbons (n) in one of the alkyl chains of [CnC1Pyrr]+. It was also found that hf-BILs' density decreases with an increase in the alkyl chain length of [CnC1Pyrr]+. It is suggested that the "odd-even" effect is associated with the difference in packing and specific interactions of cations and anions of this class of hf-BILs. Their lubricating properties, as 3 wt% additives in polyethylene glycol (PEG), were evaluated in steel-steel contacts. PEG with hf-BILs additive provided significantly lower wear and friction compared to the neat PEG and 5W40 engine oil. It was found that shortening the length of the longest alkyl chain in the cations of [C(n)C(1)Pyrr][BMB] significantly reduces frictional losses. Antiwear properties of [C(n)C(1)Pyrr][BMB] in PEG follow the same trend.

  • 115. Wang, Y. -L
    et al.
    Sarman, S.
    Glavatskih, Sergei B.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Antzutkin, O. N.
    Rutland, M. W.
    Laaksonen, A.
    Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures. I. Local microscopic structure2015In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 119, no 16, p. 5251-5264Article in journal (Refereed)
    Abstract [en]

    Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P<inf>6,6,6,14</inf>][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P<inf>6,6,6,14</inf>] cations and isolated polar domains consisting of the central segments of [P<inf>6,6,6,14</inf>] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P<inf>6,6,6,14</inf>] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P<inf>6,6,6,14</inf>][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P<inf>6,6,6,14</inf>] cations. © 2015 American Chemical Society.

  • 116.
    Wang, Yong-Lei
    et al.
    KTH.
    Sarman, Sten
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Antzutkin, Oleg N.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Laaksonen, Aatto
    Solvation structures of water in trihexyltetradecylphosphonium-orthoborate ionic liquids2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 6, article id 064507Article in journal (Refereed)
    Abstract [en]

    Atomistic molecular dynamics simulations have been performed to investigate effective interactions of isolated water molecules dispersed in trihexyltetradecylphosphonium-orthoborate ionic liquids (ILs). The intrinsic free energy changes in solvating one water molecule from gas phase into bulk IL matrices were estimated as a function of temperature, and thereafter, the calculations of potential of mean force between two dispersed water molecules within different IL matrices were performed using umbrella sampling simulations. The systematic analyses of local ionic microstructures, orientational preferences, probability and spatial distributions of dispersed water molecules around neighboring ionic species indicate their preferential coordinations to central polar segments in orthoborate anions. The effective interactions between two dispersed water molecules are partially or totally screened as their separation distance increases due to interference of ionic species in between. These computational results connect microscopic anionic structures with macroscopically and experimentally observed difficulty in completely removing water from synthesized IL samples and suggest that the introduction of hydrophobic groups to central polar segments and the formation of conjugated ionic structures in orthoborate anions can effectively reduce residual water content in the corresponding IL samples.

  • 117. Wang, Yong-Lei
    et al.
    Shah, Faiz Ullah
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Ghent University, Belgium .
    Antzutkin, Oleg N.
    Laaksonen, Aatto
    Atomistic Insight into Orthoborate-Based Ionic Liquids: Force Field Development and Evaluation2014In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 29, p. 8711-8723Article in journal (Refereed)
    Abstract [en]

    We have developed an all-atomistic force field for a new class of halogen-free chelated orthoborate-phosphonium ionic liquids. The force field is based on an AMBER framework with determination of force field parameters for phosphorus and boron atoms, as well as refinement of several available parameters. The bond and angle force constants were adjusted to fit vibration frequency data derived from both experimental measurements and ab initio calculations. The force field parameters for several dihedral angles were obtained by fitting torsion energy profiles deduced from ab initio calculations. To validate the proposed force field parameters, atomistic simulations were performed for 12 ionic liquids consisting of tetraalkylphosphonium cations and chelated orthoborate anions. The predicted densities for neat ionic liquids and the [P-6,P-6,P-6,P-14][BOB] sample, with a water content of approximately 2.3-2.5 wt %, are in excellent agreement with available experimental data. The potential energy components of 12 ionic liquids were discussed in detail. The radial distribution functions and spatial distribution functions were analyzed and visualized to probe the microscopic ionic structures of these ionic liquids. There are mainly four high-probability regions of chelated orthoborate anions distributed around tetraalkylphosphonium cations in the first solvation shell, and such probability distribution functions are strongly influenced by the size of anions.

  • 118.
    Wang, Yong-Lei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Shimpi, Manishkumar R.
    Sarman, Sten
    Antzutkin, Oleg N.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Univ Ghent, Belgium.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Laaksonen, Aatto
    Atomistic Insight into Tetraalkylphosphonium Bis(oxalato)borate Ionic Liquid/Water Mixtures. 2. Volumetric and Dynamic Properties2016In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, no 30, p. 7446-7455Article in journal (Refereed)
    Abstract [en]

    Atomistic molecular dynamics simulations have been performed to investigate volumetric quantities and dynamic properties of binary trihexyltetradecylphosphonium bis(oxalato)-borate ([P-6,P-6,P-6,P-14][BOB]) ionic liquid (IL)/water mixtures with different water concentrations. The predicted liquid densities for typical [P-6,P-6,P-6,P-14][BOB] IL/water mixtures are consistent with available experimental data with a relative discrepancy of less than 3%. The liquid densities and excess molar volumes of all studied [P-6,P-6,P-6,P-14][BOB] IL/water mixtures are characterized by concave and convex features, respectively, within full water concentration range. The dynamic properties of [P-6,P-6,P-6,P-14] cations, [BOB] anions, and water molecules are particularly analyzed through calculation of velocity autocorrelation functions, diffusion coefficients, and reorientational autocorrelation functions and correlation times. The translational and reorientational mobilities of three species become faster upon increasing water concentration in [P-6,P-6,P-6,P-14][BOB] IL/water mixtures and present complex dynamical characteristics arising from three distinct microscopic diffusion features within the full water concentration range. The obtained striking volumetric quantities and particular dynamic properties are well correlated to microscopic liquid structural organization and distinct local ionic environment of all studied [P-6,P-6,P-6,P-14][BOB] IL/water mixtures.

  • 119.
    Álvarez Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Cranston, Emily
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wakeham, Deborah
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Niga, Petru
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Werzer, O.
    Sweeney, J.
    Hausen, F.
    Hayes, R.
    Webber, G. B.
    Endres, F.
    Bennewitz, R.
    Hjalmarsson, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Atkin, R.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Nanotribology: Tribotronics, ionic liquids and control of surface interactions2013In: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, p. 3106-3108Conference paper (Refereed)
    Abstract [en]

    The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation between the number of ion pairs trapped in the tribological contact and the friction coefficient displayed. The second is the fact that the surface electrical potential can be used to control the composition of the boundary layer and thus tune the friction. Thirdly, the interfacial ordering appears to significantly affect the fluid dynamics over large distances.

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