The Long‐Term Stability of KO2 in K‐O2 Batteries

The rechargeable K‐O₂ battery is recognized as a promising energy storage solution owing to its large energy density, low overpotential, and high coulombic efficiency based on the single‐electron redox chemistry of potassium superoxide. However, the reactivity and long‐term stability of potassium superoxide remains ambiguous in K‐O₂ batteries. Parasitic reactions are explored and the use of ion chromatography to quantify trace amounts of side products is demonstrated. Both quantitative titrations and differential electrochemical mass spectrometry confirm the highly reversible single‐electron transfer process, with 98 % capacity attributed to the formation and decomposition of KO₂. In contrast to the Na‐O₂ counterparts, remarkable shelf‐life is demonstrated for K‐O₂ batteries owing to the thermodynamic and kinetic stability of KO₂, which prevents the spontaneous disproportionation to peroxide. This work sheds light on the reversible electrochemical process of K⁺+e^?+O₂?KO₂.     

Some applications of modern polarography in metallurgical analysis

Summary A brief review is set out on the application of modern polarographic techniques, as square-wave, pulse and differential cathode-ray polarography in the field of metallurgical and trace analysis. Some experimental details are given to achieve the increased precision of 0.1% of differential cathode-ray polarography. For a number of alloys the analytical data obtained by modern polarographic techniques are compared with those of other analytical methods, e.g. volumetric and gravimetric analysis, electrolysis, X-ray fluorescence.

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Zusammenfassung Es wird ein Überblick über Anwendung moderner polarographischer Verfahren wie Square-Wave-, Pulse- und Differentialkathodenstrahlpolarographie in der Legierungs- und Spurenanalyse gegeben. Einzelheiten über die bei der Anwendung der Kathodenstrahlpolarographie erzielbare Genauigkeit von 0,1% werden mitgeteilt. Für eine Reihe von Metallegierungen werden die polarographischen Analysenergebnisse mit den nach anderen Methoden (Volumetrie, Gravimetrie, Elektrolyse, Röntgenfluorescenz) erhaltenen Werten verglichen.

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Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday.     

A study of η-allyl(η-cyclopentadienyl)- dicarbonylmanganese salts

New substituted η³-allyl(η⁵-cyclopentadienyl)dicarbonylmanganese cations have been prepared as their tetrafluoroborates. They readily add a wide range of nucleophiles yielding η²-alkene(η⁵-cyclopentadienyl)dicarbonylmanganese complexes. Of the latter, in general only those involving terminal alkenes are sufficiently stable to permit ready isolation; otherwise metal-free alkenes are obtained. Regioselectivity in these additions depends on the nucleophile.     

Molecular complexes of sulfur dioxide with organic carbonates

Spectroscopic studies made on the bisphenol A polycarbonate–sulfur dioxide system showed evidence of interaction between polymer and penetrant. Equilibrium studies made on solutions of sulfur dioxide and organic carbonates chosen as monomer analogs showed that complexes of the donor–acceptor type were formed, and that at temperatures of 15°C and less the stoichiometry of these was greater than 1:1. The procedures described are compared with those used in other donor–acceptor studies, and the results observed from the equilibrium studies are interpreted by using data reported for other sulfur dioxide–donor systems.     

Femtosecond vibrational dynamics of self-trapping in a quasi-one-dimensional system

We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system [Pt(en)(2)] [Pt(en)2Br2];(PF6)(4) ( en = ethylene-diamine, C2H8N2), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at approximately 110 cm(-1) accompanies the formation of the self-trapped exciton on a approximately 200 fs time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.     

Development and applications of a preparative scale sample controlled thermogravimetric system

Journal of Thermal Analysis and Calorimetry -     

Some exact solutions for a class of compressible non-linearly elastic materials

In this paper we consider exact solutions for plane and axisymmetric deformations for a class of compressible elastic materials we call coharmonic. The coharmonic materials are derived from the harmonic materials by using Shield's inverse deformation theorem. The governing equations for the coharmonic material show the same kind of simplification associated with the harmonic materials. The equations reduce to first-order linear equations depending on an arbitrary harmonic function. They are intractable in general, so various ansätze are investigated. Boundary value problems for the coharmonic materials are compared with the same problems for harmonic materials. For certain boundary value problems, the harmonic materials exhibit well-known problematic behaviour which limits their use as models of material behaviour. The corresponding solutions for the coharmonic materials do not display these non-physical features.