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

THERMODYNAMIC AND ELECTRIC TRANSPORT PROPERTIES OF FLUID CESIUM AND RUBIDIUM IN THE M-NM TRANSITION REGION

The paper reports new experimental results of the electrical conductivity, σ, and the PVT-data of fluid cesium and rubidium which have been measured simultaneously at sub- and supercritical conditions. In the presentation of these data special emphasis is given to the observed corresponding state behaviour. In the M-NM transition region, i.e. in the density range ρc < ρ < 2 ρc-<c being the critical density - a striking similarity is found in the conductivity change between cesium and rubidium. Next to the critical point, defined by the steep divergence of the thermodynamic derivatives obtained from the PVT-data, such as compressibility and thermal expansivity, the observed conductivity for both cesium and rubidium is 250 ± 150 Ω-1cm-1

Apparatus for neutron diffraction measurements on fluids up to 2 000 K and elevated pressures

The paper describes the principle set-up of a high temperature-high pressure apparatus for neutron diffraction on fluids. As an example the results of the static structure factor of expanded fluid rubidium up to 2 000 K near saturation conditions are briefly presented.Cette publication décrit le principe d'un appareillage pour l'étude de la diffraction des neutrons par des systèmes fluides, à hautes températures et hautes pressions. Comme exemple, les facteurs de structure du rubidium liquide à des températures allant jusqu'à 2 000 K et près de la saturation sont présentés

STRUCTURE OF EXPANDED LIQUID RUBIDIUM BY NEUTRON DIFFRACTION

The static structure factor, S(Q), of liquid rubidium has been studied by neutron diffraction for temperatures up to 2000 K and pressures up to 139 bar near saturation conditions, corresponding to an expansion of the liquid from 1.46 to 0.54 gcm-3. The characteristic changes of the scattering behaviour and of the microscopic structure approaching the M-NM transition region are discussed. A comparison of these results with simple hard sphere model calculations is given

Resonant Raman scattering from phonons in GaAs/(GaAs)(m)(AlAs)(n) quantum wire structures

Raman spectroscopy has been used to measure phonons in GaAs v-groove quantum wire structures containing (001) and (111) GaAs/AlAs superlattice barrier regions. Resonance enhancement permits the identification of modes in different regions of the structure, and the measured phonon frequencies provide structural information which shows clear evidence of GaAs migration during growth from (001) surfaces into the grooves. Confined and interface phonons with large in-(111) plane wavevectors are observed. (C) 1996 American Institute of Physics