Scandium-doped AlN 1D hexagonal nanoprisms : a class of room-temperature ferromagnetic materials

Pretty vacancy: The formation energy of Al vacancies in aluminum nitride is decreased by doping with nonmagnetic scandium ions. These vacancies are shown to be the cause of the room-temperature ferromagnetism in the resulting 1D hexagonal nanoprisms of AlN:Sc, a result that is confirmed by first-principles calculations. The doping approach provides a new route to dilute magnetic semiconductor materials.

Room-temperature insertion of elemental tellurium into the Cspł-Br and -I bonds of α-bromo-and α-iodopinacolone

Pinacolyltellurium(IV) dihalides, (t-BuCOCH₂)₂TeX₂ (X ) Br (1b), I (1c)) and Ar(t-BuCOCH₂)TeCl₂ (Ar == 1-C₁₀H₇ (Np) (2a), 2,4,6-Me₃C₆H₂ (Mes) (3a)), are readily prepared at room temperature by the oxidative insertion of elemental tellurium into the C_sp³-Br or -I bond of the α-halopinacolone and by the reaction of ArTeCl₃ with the pinacolone t-BuCOCH₃. The bromides Np(t-BuCOCH₂)TeBr₂ (2b) and Mes(t-BuCOCH₂)TeBr₂ (3b) can be prepared by the addition of bromine to the telluride Ar(t-BuCOCH₂)-Te or of α-bromopinacolone to ArTeBr. Variable-temperature ¹H and ¹³C NMR of the separate signals for the o-Me groups in 3a,b indicate a very high barrier to rotation about the Te-C(aryl) bond. Crystal diffraction data for 1c, 2a-c, and 3b show that intramolecular 1,4-Te …O(C) secondary bonding interactions (SBIs) are retained even in the presence of bulky aryl groups and intermolecular Te …X SBIs are subject to electronic population and steric congestion around the Te(IV) center in the solid state.

Deformation mechanisms in mg alloys and the challenge of extending room-temperature Plasticity

Magnesium alloys show promise for application in formed components where weight saving is an advantage. In most instances forming is carried out at elevated temperatures. However, there are considerable gains to be had if forming can be carried out under ambient conditions. The present article outlines some of the difficulties that lie in the way of achieving this objective. The underlying metallurgical characteristics of the issues are considered and means for overcoming them are discussed. It is concluded that a combination of microstructure and texture control remains a promising strategy.

Lithium-polymer battery based on an ionic liquid–polymer electrolyte composite for room temperature applications

A lithium-polymer battery based on an ionic liquid–polymer electrolyte (IL–PE) composite membrane operating at room temperature is described. Utilizing a polypyrrole coated LiV₃O₈ cathode material, the cell delivers >200 mAh g⁻¹ with respect to the mass of the cathode material. Discharge capacity is slightly higher than those observed for this cathode material in standard aprotic electrolytes; it is thought that this is the result of a lower solubility of the LiV₃O₈ material in the IL–PE composite membrane.

Room temperature fast-ion conduction in imidazolium halide salts

Fast-ion conduction has been observed in the iodide and bromide salts of 1-methyl-3-ethylimidazolium at ambient temperatures. The melting point of these two compounds is above 350 K and even at 273 K the ionic conductivity in the solid-state is greater than 10⁻³S cm⁻¹. Cation diffusion coefficients have been measured using fringe field gradient and/or pulse field gradient ¹H NMR techniques, which indicated cation diffusion coefficients of the order of 10⁻¹⁰ m² s⁻¹ in the solid-state. Remarkably, these values are up to an order of magnitude higher than the cation diffusion coefficient in the supercooled liquid at 293 K. The activation energy for diffusion in the solid-state is extremely small, as is typical of solid-state fast-ion conductors and indicates a change in transport mechanism from the melt to the crystal. The inability to detect an ¹²⁷I signal together with the modelling of the conductivity using the Nernst–Einstein equation suggests that the solid-state conduction is primarily due to cation diffusion. The solid-state fast-ion conduction is most likely related to vacancy diffusion along the cation layers in the crystal. The temperature dependence of the NMR signal intensity indicates that the number of mobile species is increasing with increasing temperature with an activation energy of approximately 20–30 kJ mol⁻¹.

Room-temperature molten salts based on the quaternary ammonium ion

The properties of a family of novel quaternary ammonium salts based on the bis(trifluoromethylsulfonyl)imide and triflate anions are reported. Binary phase diagrams for some of their mixtures and their electrochemical windows of stability are also reported. The highest conductivity observed in the pure salt systems at 25 °C was 7 × 10^-4 S cm^-1. An electrochemical window of stability of up to 5 V was measured on graphite electrodes. The effect of salt structure and solvent on conductivity of the salts is also discussed.

Electrochemistry of room temperature protic ionic liquids

Eighteen protic ionic liquids containing different combinations of cations and anions, hydrophobicity, viscosity, and conductivity have been synthesized and their physicochemical properties determined. In one series, the diethanolammonium cations were combined with acetate, formate, hydrogen sulfate, chloride, sulfamate, and mesylate anions. In the second series, acetate and formate anions were combined with amine bases, triethylamine, diethylamine, triethanolamine, di-n-propylamine, and di-n-butylamine. The electrochemical characteristics of the eight protic ionic liquids that are liquid at room temperature (RTPILs) have been determined using cyclic, microelectrode, and rotating disk electrode voltammetries. Potential windows of the RTPILs have been compared at glassy carbon, platinum, gold, and boron-doped diamond electrodes and generally found to be the largest in the case of glassy carbon. The voltammetry of IUPAC recommended potential scale reference systems, ferrocene/ferrocenium and cobaltocenium/cobaltocene, have been evaluated and found to be ideal in the case of the less viscous RTPILs but involve adsorption in the highly viscous ones. Other properties such as diffusion coefficients, ionic conductivity, and double layer capacitance also have been measured. The influence of water on the potential windows, viscosity, and diffusion has been studied systematically by deliberate addition of water to the dried ionic liquids. The survey highlights the problems with voltammetric studies in highly viscous room temperature protic ionic liquids and also suggests the way forward with respect to their possible industrial use.

Electron backscatter diffraction (EBSD) map of AZ31 compressed to 1% strain at room temperature in a direction parallel to the extrusion direction

The collection contains an EBSD map of AZ31 compressed to 1% strain at room temperature in a direction parallel to the extrusion direction. The map was collected as part of an investigation into the role of twinning in the occurrence of a yield point elongation during deformation.