Ionic liquids containing tricyanomethanide anions: physicochemical characterisation and performance as electrochemical double-layer capacitor electrolytes

We investigated the use of fluorine free ionic liquids (ILs) containing the tricyanomethanide anion ([C(CN)3]) as an electrolyte in electrochemical double-layer capacitors (EDLCs). Three cations were used; 1-butyl-3-methylimidazolium ([Im1,4]), N-butyl-N-methylpyrrolidinium ([Pyr1,4]) and N-butyl-N-methylpiperidinium ([Pip1,4]). Their physicochemical properties are discussed alongside with their performance as electrolytes. We found that the cyano-based ILs present higher ionic conductivity (9.4, 8.7 and 4.2 mS cm−1 at 25 °C for [Im1,4], [Pyr1,4] and [Pip1,4], respectively) than the widely studied IL containing the bis(trifluoromethylsulfonyl)imide anion, namely [Pyr1,4][Tf2N] (2.7 mS cm−1 at 25 °C). Of the three ILs investigated, [Pip1,4][C(CN)3] presents the widest electrochemical stability window, 3.0 V, while [Pyr1,4][C(CN)3] is stable up to 2.9 V and its [Tf2N] analogue can operate at 3.5 V. Despite operating at a lower voltage, [Pyr1,4][C(CN)3] EDLC is capable of delivering up to 4.5 W h kg−1 when operating at high specific power of 7.2 kW kg−1, while its [Pyr1,4][Tf2N] counterpart only delivered 3.0 W h kg−1 when operated at similar power

EMImCl-AlCl 3

This work studied the electro-polymerisation of 3,4-ethylenedioxythiophene (EDOT) and its electrochemical behavior in Lewis acidic, neutral and basic chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride aluminum chloride (EMImCl-AlCl3) by cyclic voltammetry. It was found that the electro-polymerisation on vitreous carbon only occurs in Lewis neutral EMImCl-AlCl3 as a dark blue-violet film whereas the electro-polymerisation in a Lewis acidic or basic compositions is not possible due to the interactions between the conductive polymer and the ionic liquid as well as the potential stability limits of the electrolyte. PEDOT films synthesised in Lewis neutral ionic liquid were tested in monomer-free Lewis acidic, basic and neutral EMImCl-AlCl3 and show different doping and de-doping behavior for chloride ionic species. The PEDOT films in a Lewis neutral composition showed higher doping levels due to the higher potential stability window, up to 2.6 V vs. Al|Al(III) than in a Lewis acidic and basic solutions. Furthermore, it was shown that the doping and de-doping levels are predefined during the electro-polymerisation of PEDOT. The anion doping and de-doping reaction reached 97% reversibility in the neutral composition, which suggests that PEDOT is a suitable electrode material to store charged species in this media and could be used in rechargeable energy storage devices

Influence of Particle Size Distribution on the Performance of Ionic Liquid-based Electrochemical Double Layer Capacitors.

Electrochemical double layer capacitors (EDLCs) employing ionic liquid electrolytes are the subject of much research as they promise increased operating potentials, and hence energy densities, when compared with currently available devices. Herein we report on the influence of the particle size distribution of activated carbon material on the performance of ionic liquid based EDLCs. Mesoporous activated carbon was ball-milled for increasing durations and the resultant powders characterized physically (using laser diffraction, nitrogen sorption and SEM) and investigated electrochemically in the form of composite EDLC electrodes. A bi-modal particle size distribution was found for all materials demonstrating an increasing fraction of smaller particles with increased milling duration. In general, cell capacitance decreased with increased milling duration over a wide range of rates using CV and galvanostatic cycling. Reduced coulombic efficiency is observed at low rates (<25 mVs(-1)) and the efficiency decreases as the volume fraction of the smaller particles increases. Efficiency loss was attributed to side reactions, particularly electrolyte decomposition, arising from interactions with the smaller particles. The effect of reduced efficiency is confirmed by cycling for over 15,000 cycles, which has the important implication that diminished performance and reduced cycle life is caused by the presence of submicron-sized particles

Ionic liquids at electrified interfaces

Until recently, “room-temperature” (<100–150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)–(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of “first-generation” room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the “later generation” RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in “cocktails” of one’s choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost “universal” solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) “sister-systems”.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules

Subjective Evaluation of Directional Properties of Loudspeaker Systems with the Analog and Digital Crossover Networks

The aim of this study was to determine the way in which loudspeaker systems with the analog and digital crossover networks were subjectively evaluated. The object of the study were two loudspeaker systems, differing in both the position of speakers on the front panel of enclosure and configuration of the crossover networks: 2.5-way and 3-way systems with the slope of frequency response of 12 dB/octave in the cut-off regions. The investigations were conducted for 5 angles from the front hemisphere in the horizontal plane. Test signals were fragments of music and speech. The recordings of these signals were conducted in an anechoic chamber using an artificial head and then presented to the listeners through headphones. Five normally-hearing listeners aged 18-50 years took part in the experiment. Listening tests were carried out in two stages. In the first stage listeners were listening to test signals grouped in triads and their task was to identify pairs of signals the most and the least similar to each other. In the second stage a parametric evaluation was performed. It consisted in assigning five numbers, corresponding to the intensity of the attribute of perception space (evaluated on a scale of 0-10) to each of test signals. The attributes of perception space included: sharpness, clearness, fullness, lack of distortions and loudness. Using the method of multidimensional scaling and correlation analysis it was possible to relate a particular dimension of the multidimensional space to the attributes of the perception space. It was found that the intrinsic attributes responsible for the subjective evaluation of loudspeaker systems with the analog and digital crossover network were sharpness, clearness and loudness

Estimation method of rope wheel bearings wear extant for special conditions of S 1.3 lift at the Coal Mine "Bogdanka"

W pracy przedstawiono metodę oceny stopnia zużycia łożysk kół linowych, opracowaną dla charakterystycznego przypadku wyciągu szybowego S1.3 w L.W. "Bogdanka". Przedstawiona metoda diagnostyczna może mieć również zastosowanie do badania łożysk kół linowych kierunkowych z ruchomą osią i łożyskami umieszczonymi na zewnątrz osi w korpusach, które przeważają w polskim górnictwie. Wyższość tej metody w stosunku do stosowanych do tej pory, polega na skróceniu czasu wykonywania badań, a także braku konieczności angażowania do jego wykonania dodatkowych pracowników obsługi szybu. Nie wymaga ona także specjalnego udostępnienia urządzeń szybowych na czas wykonywania badań.The paper presents estimation method of rope wheel bearings wear for special conditions of mining lift S 1.3 at the Coal Mine "Bogdanka". Except presented application in special conditions of the Coal Mine "Bogdanka", described diagnostic method can be also applied for bearings' wear estimation in ropes with another constructions, which are in most cases used by mining industry in Poland. With its use, diagnosis can be finished within much shorter time, without special activities of additional rope supervising staff members. Also special access to the machine under diagnostic action is not necessary

Propulsion configuration effect on performance of an inverted joined wing airplane

Efficiency is crucial for an airplane to reduce both costs of operations and emissions of pollutants. There are several airplane concepts that potentially allow for increasing the efficiency. A few of them were not investigated thoroughly enough yet. The inverted joined wing configuration, where the upper wing is positioned in the front of the lower one is an example of such a concept. Therefore, a project consisting of an aerodynamic analysis and optimisation, development of the software for multidisciplinary optimisation, development of an electric propulsion system, development of an experimental scaled demonstrator, wind tunnel testing and flight-testing was undertaken by consortium led by the Institute of Aviation, including also Warsaw University of Technology, Air Force Institute of Technology and small company MSP. Results of this project led to the conclusion that inverted joined wing configuration allows to build an airplane with the best performance in the world, but its advantage against conventional airplanes is marginal. One reason for this is large trimming drag of the configuration with relatively high position of the thrust vector. Therefore, other configurations of the propulsion were also considered to see if airplane performance could be further improved. This effort is described in the present paper

Application of one parameter classification for splitting rock massif on roof, seam and floor rocks of "Rudna" Mine

W pracy pokazano, że podział skał złożowych i otaczających na strop, wyrobisko i spąg jest statystycznie istotny. Ocenę podziału oparto na analizie wariancji i klasyfikacji pojedynczej. Badania przeprowadzono dla sześciu parametrów górotworu, która zawierała dokumentacja pomiarów.It was shown in the paper that differentiation of rock massif into roof, seam and floor rocks is statistically significant. Variance analysis and one parameter classification were utilized to carry out required computation. Six rock parameters from laboratory data were taken into account