Thermodynamische Untersuchungen im System Gold—Cadmium, 2. Mitt.

Liquidus and solidus curves of the -AuCd phase were determined byDTA measurements. -AuCd has a congruent melting point of 629.5°C at 47 at% Cd with no signs of other minima or maxima in the liquidus curve between 43 and 51 at% Cd. Liquid and solid Au–Cd alloys were investigated by theemf method between 40 and 90 at% Cd and 653–973 K. A consistent set of integral thermodynamic data for liquid and for solid alloys of the entire Au–Cd system were calculated at 1000 and at 700K, resp., using values taken from the literature. Partial molar entropies of Cd of solid -AuCd and of liquid alloys in the same concentration range were compared and discussed with respect to ordering phenomena in solid and liquid alloys.

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Thermodynamische Untersuchungen im System Gold—Cadmium

Zusammenfassung Flüssige und feste Legierungen im System Au–Cd wurden von 60 bis 90 At% Cd zwischen 653° und 873°K mit derEMK-Methode untersucht und thermodynamische Eigenschaften berechnet. Die Aktivitäten von Cd zeigen stark negative Abweichungen vom idealen Verhalten. Die partiellen molaren Enthalpien sind negativ und verschieben sich mit zunehmender Temperatur zu weniger negativen Werten, die partiellen molaren Entropien sind positiv und nehmen mit zunehmender Temperatur zu. Aus eigenen Werten und Literaturdaten wurden integrale thermodynamische Größen für die Schmelzen im gesamten System Au–Cd bei 1000°K berechnet. Für einige feste Cd-reiche Phasen wurden ebenfalls Aktivitäten erhalten und aus den Knickpunkten derEMK-Temperatur-Kurve Temperaturen von Phasenübergängen bestimmt.

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Thermodynamic investigations in theAu–Cd-system

Liquid and solid alloys in the Au–Cd system were investigated between 60 and 90 at % Cd and 653°–873°K by theemf method, and thermodynamic properties were calculated. The activities of Cd exhibit strong negative deviations from ideal behavior. Partial molar enthalpies are negative and become less so with increasing temperature; partial molar entropies are positive and increase with increasing temperature. A consistent set of integral thermodynamic data for liquid solutions of the entire Au–Cd system at 1000°K were calculated using values taken from the literature. Activities for some solid Cd-rich phases were also obtained. From discontinuities in theemf vs. temperature curve temperatures of phase transitions were determined.

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Die Systeme Nickel—Selen und Kobalt—Nickel-Selen

Zusammenfassung Das System Ni–Se wurde thermisch und röntgenographisch untersucht und aus den Resultaten und aus Literaturangaben das Phasendiagramm aufgestellt. Die Hochtemperaturphase -Ni₃Se₂ zersetzt sich peritektisch bei 785 °C, die Verbindung Ni₆Se₅ peritektoidisch bei 647,5 °C. Die B8-(NiAs-)Phase Ni_1–x Se hat einen kongruenten Schmelzpunkt bei 53,5 At% Se und 959 °C und eine maximale Phasenbreite von 50,5 At% Se (785 °C) bis 56,8 At% Se (856 °C). NiSe₂ zerfällt peritektisch bei 853 °C in Ni_1–x Se und eine Se-reiche Schmelze. In Schmelzen mit mehr als 68,0 At% Se tritt oberhalb 856 °C eine Mischungslücke auf. Röntgenographisch konnte die Existenz der vier Verbindungen -Ni₃Se₂, Ni₆Se₅, Ni_1–x Se und NiSe₂ bestätigt werden.Im Dreistoffsystem Co–Ni–Se wurden drei Schnitte untersucht. In den quasibinären Schnitten zwischen den B8-Phasen Ni_1–x Se und Co_1–x Se und zwischen den C2-Phasen NiSe₂ und CoSe₂ sind die Legierungen sowohl im flüssigen als auch im festen Zustand vollkommen mischbar. In beiden Schnitten fallen die Liquidus- und Solidustemperaturen kontinuierlich von der Co-zur Ni-Seite ab. Die ternäre Phase (Co_1–y Ni _y )₁₁Se₈ ist bei 400 °C zwischen 0,9>y>0,5 stabil.

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The systems nickel—selenium and cobalt—nickel—selenium. Transition metal-chalcogen systems, II Übergangsmetall-Chalkogensysteme, 2. Mitt.

The Ni–Se system was investigated by X-ray and thermal analyses and from the results and from published data the Ni–Se phase diagram was constructed. The high temperature phase -Ni₃Se₂ decomposes peritectically at 785°C, the compound Ni₆Se₅ peritectoidically at 647.5°C. The B8 (NiAs) phase Ni_1–x Se has a congruent melting point at 53.5 at% Se and 959°C and a maximum range of homogeneity between 50.5 at% Se (785 °C) and 56.8 at% Se (856 °C). NiSe₂ decomposes peritectically at 853 °C into Ni_1–x Se and a Se-rich melt. Melts with more than 68.0 at% Se exhibit above 856 °C a miscibility gap. X-ray investigations confirmed the existence of the four compounds -Ni₃Se₂, Ni₆Se₅, Ni1– xSe, and NiSe₂.Three sections of the ternary system Co–Ni–Se were investigated. Alloys of the quasibinary sections between the B8 phases Ni_1–x Se and Co_1–x Se and between the C2 phases NiSe₂ and CoSe₂ are completely miscible in the liquid as well as in the solid state. The liquidus and the solidus temperatures in these sections drop continuously from the Co-to the Ni-side of the diagram. The ternary phase (Co_1–y Ni _y )₁₁Se₈ is stable at 400 °C between 0.9<y<0.5.

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Charge correlations in cobaltates La2–xSrx CoO4

We report on an elastic neutron scattering study of the charge correlations in La_2–xSr_x CoO₄ with x = 1/3, 0.4 and 0.5. We found that the checkerboard charge ordering correlations present in the x = 0.5 sample persist in the x = 0.4 and 1/3 materials. These checkerboard charge ordering correlations are robust and explain the occurrence of nano‐phase separation in layered cobaltates for Sr‐concentrations away from half‐doping. The half‐integer reflections then arise from the nanometer‐sized hole‐rich regions (blue areas in title figure) instead of the undoped ones (red areas in title figure). The appearance of nano‐phase separation is an important ingredient for understanding the formation of hour‐glass shaped magnetic excitation spectra in La_2–xSr_x CoO₄.

Nano‐phase separation in La_2–xSr_x CoO₄ (schematically). Red areas: undoped La₂CoO₄ islands, blue areas: checkerboard charge ordered regions; black, green and blue balls represent nonmagnetic Co³⁺ ions, magnetic Co²⁺ ions and oxygen ions, respectively; green arrows indicate Co²⁺ spins [1, 2].     

CaCrO3: an anomalous antiferromagnetic metallic oxide

Combining infrared reflectivity, transport, susceptibility, and several diffraction techniques, we find compelling evidence that CaCrO3 is a rare case of a metallic and antiferromagnetic transition-metal oxide with a three-dimensional electronic structure. Local spin density approximation calculations correctly describe the metallic behavior as well as the anisotropic magnetic ordering pattern of C type: The high Cr valence state induces via sizable pd hybridization remarkably strong next-nearest-neighbor interactions stabilizing this ordering. The subtle balance of magnetic interactions gives rise to magnetoelastic coupling, explaining pronounced structural anomalies observed at the magnetic ordering transition.     

Inelastic neutron-scattering measurements of incommensurate magnetic excitations on superconducting LiFeAs single crystals

Magnetic correlations in superconducting LiFeAs were studied by elastic and by inelastic neutron-scattering experiments. There is no indication for static magnetic ordering, but inelastic correlations appear at the incommensurate wave vector (0.5±δ,0.5-/+δ,0) with δ~0.07 slightly shifted from the commensurate ordering observed in other FeAs-based compounds. The incommensurate magnetic excitations respond to the opening of the superconducting gap by a transfer of spectral weight.     

Nonstoichiometry in B8-Type NiSb

The phase diagram of the nickel-antimony system has been investigated between 40 and 54 at% Sb. The congruent melting point of γ-NiSb (with NiAs-structure) was found at 47 at% Sb and 1432 ± 5 K. Lattice parameters and pycnometric density of this phase were determined as a function of composition; both exhibit a change of slope between 50 and 51 at% Sb rather than exactly at the stoichiometric composition. In the same concentration range a flat minimum was also found in the composition dependence of the magnetic susceptibility measured at room temperature. These effects are explained by the following defect mechanism: Starting at the antimonyrich phase boundary nickel atoms will at first occupy octahedral sites. However, before these sites are completely filled, nickel atoms will start to fill the trigonal-bipyramidal holes (interstitial sites) of the NiAs-lattice.     

Quecksilber-Halogensysteme, 2. Mitt.: Das System Quecksilber-Jod

Zusammenfassung Das System Hg–J₂ wurde thermoanalytisch und visuell untersucht. Im System J₂–HgJ₂ bildet J₂ mit HgJ₂ ein Eutektikum bei 14,5 Mol% HgJ₂ und 101,3°C. Rotes HgJ₂ wandelt sich bei 131,2°C in gelbes HgJ₂ um, welches bei 256,7°C schmilzt. Im System HgJ₂–Hg liegt zwischen HgJ₂ und Hg₂J₂ ein Eutektikum bei 82,7 Mol% HgJ₂ und 231,4°C. Bei erstmaligem Aufheizen schmilzt Hg₂J₂ bei 296°C. Unter Gleichgewichtsbedingungen bildet sich Hg₂J₂ syntektisch bei 241,5°C aus einer HgJ₂-reichen Schmelze mit 79 Mol% HgJ₂ und einer Hg-reichen Schmelze mit<0,5 Mol% HgJ₂. Zwischen diesen beiden Zusammensetzungen erstreckt sich eine Mischungslücke im flüssigen Zustand. Die kritische Temperatur liegt bei 288°C, doch ist die kritische Entmischungskurve zwischen 20 und 60 Mol% HgJ₂ praktisch horizontal. Oberhalb dieser Temperatur herrscht im System J₂–Hg vollkommene Mischbarkeit.Diese Resultate konnten visuell bestätigt werden. Gleichzeitig wurden bei Temperaturänderung charakteristische reversible Farbänderungen beobachtet. Berechnungen der Liquiduskurve ergaben, daß Schmelzen im System J₂–HgJ₂ nahezu ideale Lösungen der Molekülarten J₂ und HgJ₂ darstellen. Bei Zusatz von Hg zu HgJ₂-Schmelzen bilden sich entweder Hg-Atome oder Hg₂J₂-Moleküle. Abschließend werden die Systeme HgX ₂–Hg thermodynamisch diskutiert und mit anderen Metallhalogenid-Metallsystemen verglichen.

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Mercury-halogen systems. II. The mercury-iodine system

The Hg–J₂ system was investigated by thermal analysis and visual observation. In the J₂–HgJ₂ system J₂ forms a eutectic with HgJ₂ at 14.5 mole% HgJ₂ and 101.3°C. Red HgJ₂ transforms at 131.2°C into yellow HgJ₂ which melts at 256.7°C. In the HgJ₂–Hg system a eutectic between HgJ₂ and Hg₂J₂ is observed at 82.7 mole% HgJ₂ and 231.4°C. When heated for the first time Hg₂J₂ melts at 296°C. Under equilibrium conditions Hg₂J₂ is formed by a syntectic reaction at 241.5°C from an HgJ₂-rich melt with 79 mole% HgJ₂ and an Hg-rich melt with<0.5 mole% HgJ₂. A miscibility gap in the liquid state exists between both compositions. The critical temperature is 288°C but the critical immiscibility curve between 20 and 60 mole% HgJ₂ is practically horizontal. Above this temperature the J₂–Hg system is completely miscible. These results could be visually confirmed. Also characteristic reversible color changes with temperature could be observed. From calculations of the liquidus curves it was concluded that the melts in the J₂–HgJ₂ system are nearly ideal solutions of the molecular species J₂ and HgJ₂. Hg dissolves in liquid HgJ₂ either as Hg atoms or as Hg₂J₂ molecules. The HgX ₂–Hg systems are discussed thermodynamically and compared with other metal halogenide-metal systems.

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Extraction of Alkylphenols and Nonylphenol Mono- and Diethoxylates from Water Using Magnetically Modified Adsorbents

An LC-DAD-ESI-MS⁽²⁾ method was developed for simultaneous analysis of major chemical constituents in Shexiang Baoxin Pill (SBP), an important multiherbal formula in traditional Chinese medicine widely used for treating cardiovascular diseases. The chromatographic separation was performed on a Symmetry C₁₈ column (5 μm, 250 × 4.6 mm), whilst water with 0.5% formic acid and acetonitrile were used as mobile phase. On the basis of the characteristic UV absorption profile, the information of molecular weight and structure provided by ESI-MS⁽²⁾, 57 constituents from moschus, radix rhizoma ginseng, calculus bovis, cortex cinnamomi, styrax and venenum bufonis, were detected and 47 of them were identified in this study. The method can be the basis for the quality control of SBP.     

Thermodynamic properties of chromium—Tellurium alloys

Tellurium vapor pressures of chromium—tellurium alloys were determined in the range of NiAs-type structures between 800 and 1,300 K and between 55 and 62 at% Te by an isopiestic method. The partial molar quantities of tellurium were derived, and the results critically compared with data reported in the literature.

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Thermodynamische Eigenschaften von Chrom—Tellur-Legierungen

Zusammenfassung Die Tellurdampfdrücke von Chrom—Tellur-Legierungen wurden mit Hilfe einer isopiestischen Methode im Bereich der Phasen mit NiAs-ähnlichen Strukturen zwischen 800 und 1300 K und zwischen 55 und 62 At% Te bestimmt. Die partiellen molaren Eigenschaften von Tellur wurden daraus abgeleitet, und die Resultate kritisch mit Literaturwerten verglichen.