Enhanced superconductivity of the Ti-Zr alloys in the high-pressure BCC phase

A high-pressure study of the crystal structure and superconductivity of Ti-Zr alloys demonstrates an increase in the ω-β-transition pressure from about 30 to 43–57 GPa when the titanium content in the alloys increases from 0 to 50 at. %. The isobaric values of the BCC β-phase superconducting temperature (at 46 GPa) increase from 5.7 to more than 15 K between 0 and 50 at. % Ti, the latter value being the absolute maximum for BCC d-metal alloys. These data correlate with the earlier assumption of an s-d electron transfer in Zr under pressure.     

Reversible Lithium Insertion into LiNb6Cl19

Crystals of LiNb₆Cl₁₉ were obtained as black needles by solid state reaction of Nb powder, NbCl₅, and Li₂C₂ at 530 °C. The structure contains ladder‐like motifs built of edge and face sharing [NbCl₆] octahedra. The parallel alignment of infinite ladders yields a one‐dimensional structure, with lithium ions occupying voids in a linearly aligned manner. Each ladder combines characteristic fragments from the niobium chloride structures NbCl₄, A₃Nb₂Cl₉ (A = Rb, Cs), and Nb₃Cl₈. Lithium insertion was achieved electrochemically by slow scan cyclic voltammetry in PC (1 M LiClO₄) electrolyte. 3.73 moles of lithium per formula unit could be intercalated, with a high degree of reversibility, to a composition close to Li₅Nb₆Cl₁₉ stoichiometry.     

Demonstrating oxygen loss and associated structural reorganization in the lithium battery cathode Li[Ni0.2Li0.2Mn0.6]O2

The cathode in rechargeable lithium-ion batteries operates by conventional intercalation; Li+ is extracted from LiCoO2 on charging accompanied by oxidation of Co3+ to Co4+; the process is reversed on discharge. In contrast, Li+ may be extracted from Mn4+-based solids, e.g., Li2MnO3, without oxidation of Mn4+. A mechanism involving simultaneous Li and O removal is often proposed. Here, we demonstrate directly, by in situ differential electrochemical mass spectrometry (DEMS), that O2 is evolved from such Mn4+ -containing compounds, Li[Ni(0.2)Li(0.2)Mn(0.6)]O2, on charging and using powder neutron diffraction show that O loss from the surface is accompanied by diffusion of transition metal ions from surface to bulk where they occupy vacancies created by Li removal. The composition of the compound moves toward MO(2). Understanding such unconventional Li extraction is important because Li-Mn-Ni-O compounds, irrespective of whether they contain Co, can, after O loss, store 200 mAhg(-1) of charge compared with 140 mAhg(-1) for LiCoO(2).     

A new type of nano-sized silicon/carbon composite electrode for reversible lithium insertion

A new type of nano-sized silicon/carbon composite was developed. It shows superior electrochemical cycling properties as negative electrode material for possible use in lithium-ion batteries with respect to high reversible and low irreversible capacity, and low fading.     

Inkjet printing of Ce<Subscript>0.8</Subscript>Gd<Subscript>0.2</Subscript>O<Subscript>2</Subscript> thin films on Ni-5%W flexible substrates

The successful inkjet printing of a cerium gadolinium oxide (Ce_0.8Gd_0.2O₂) precursor solution on highly textured Ni-5%W is reported. A stable ink was synthesised from metal acetates and propionic acid with rheological properties suitable for inkjet printing and also the development of solid–liquid interface comparable with thin film formation by dip coating. Two different drop-on-demand print heads were used for deposition: a 16-nozzle piezoelectric cartridge and a single electromagnetic nozzle. Two different rastering patterns with different droplet sizes and spacing were compared. Thermogravimetry and X-ray diffractometry were used to study the thermal decomposition of the metal oxide precursors and to determine the shortest possible heat treatment of the deposited layers, potentially suitable for continuous large scale production. The results from X-ray diffraction show that the single phase Ce_0.8Gd_0.2O₂ was obtained in all cases, but only piezoelectric inkjet printing with optimised drop overlapping produces a highly textured buffer layer. Optical micrographs and atomic force microscopy also indicate the good quality of deposited films after heat treatment.     

meso‐2,2′‐Di­phenyl‐3,3′,4,4′‐tetra­hydro‐2,2′‐bi­furan‐5,5′(2H,2′H)‐dione

The crystal structure of the title compound, C₂₀H₁₈O₄, contains a crystallographic inversion center. The C—C bond linking the two halves of the mol­ecule is slightly elongated at 1.577 (3) Å.     

Zur analytischen Verwendung von S-Methylisothiuroniumsulfat bei der Mercaptanbestimmung

Zusammenfassung Zur Vermeidung der Schwierigkeiten, die bei der Eichung in der polarographischen Mercaptananalyse auftreten, wurde ein Verfahren ausgearbeitet, das für die Bestimmung der Summe von Methyl- und Äthylmercaptan den Gebrauch von S-Methylisothiuroniumsulfat [(S-MIT)₂SO₄] und seine alkalische Zersetzung zu Methylmercaptan unmittelbar vor Gebrauch in der polarographischen Zelle vorschlägt. Untersuchungen über die Bestän-digkeit wäßriger Lösungen von (S-MIT)₂SO₄ ergaben, daß 0,001 M Lösungen bis zu pH 3 über 134 Tage unveränderlich sind. Das beständige und völlig geruchlose (S-MIT)₂SO₄ kann direkt als Urtitersubstanz für Methylmercaptan eingewogen werden. — Durch ac-Polarographie konnten Eichkurven bis zu einem Gehalt von 3 · 10^–6 Mol CH₃SH/l aufgestellt werden.Weiterhin wurde die Eignung des (S-MIT)₂SO₄ als Titrationsmittel zur amperometrischen Bestimmung des Quecksilbers im Mikrogramm-Bereich mit der vibrierenden Platinelektrode gezeigt. Die indirekte Anwendung dieser Methode erlaubt eine schnelle Bestimmung von Mercaptanen und Sulfid im Mikrogramm-Bereich (durchschnittlicher relativer Fehler 5%). Durch die Fällung der entsprechenden Quecksilbersalze sind durch Luftoxydation entstehende Verluste dieser Verbindungen zu vermeiden. Die Methode wurde angewendet zur Gehaltsbestimmung von Sulfideichlösungen und zur H₂S-Bestimmung in Gasen.

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Summary A procedure has been worked out for the improvement of the calibration in polarographic mercaptan analysis. For calibration in the determination of the sum of methyl- and ethylmercaptan use is made of the alkaline decomposition of S-methylisothiuronium sulphate [(S-MIT)₂SO₄] to methylmercaptan immediately before use in the polarographic cell. The stability of aqueous solutions of (S-MIT)₂SO₄ has been examined at different pH-values over 134 days and it has been shown that 0.001 M solutions are stable up to pH 3. The stable and odourless substance can be directly weighed as a primary standard for methylmercaptan. By a c-polarography calibration curves were obtained up to a concentration of 3×10^–6 Mole of CH₃SH/l.Furthermore it is shown that (S-MIT)₂SO₄ can be employed as titrant for the amperometric determination of mercury in the g range using the vibrating Pt electrode. By indirect application of this method mercaptans and sulphide can be determined quickly and exactly with an average relative error of 5%. The method was applied to the determination of the content of sulphide standard solutions and of hydrogen sulphide in gases.

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Diese Arbeit wurde im Rahmen, einer Vertragsforschung mit dem VEB Leuria-Werke Walter Ulbricht durchgeführt. Wir danken dem Werk für die Bereitstellung von Mitteln.