Orthonitridoborate Ions [BN3]6 in Oxonitridosilicate Cages: Synthesis, Crystal Structure, and Magnetic Properties of Ba4Pr7[Si12N23O][BN3], Ba4Nd7[Si12N23O][BN3], and Ba4Sm7[Si12N23O][BN3]
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Isolated [BN3]6− ions embedded in an oxonitridosilicate framework structure were observed in the series Ba4Ln7[Si12N23O][BN3] with Ln=Pr, Nd, Sm. Presumably the [BN3]6− ions act as high-temperature stable templates which cause the formation of hexagonal cages in the [Si12N23O] framework structure (see picture). The isotypic title compounds Ba4Pr7[Si12N23O][BN3], Ba4Nd7[Si12N23O][BN3], and Ba4Sm7[Si12N23O][BN3] were prepared by reaction of Pr, Nd, or Sm, with barium, BaCO3, Si(NH)2, and poly(boron amide imide) in nitrogen atmosphere in tungsten crucibles using a radiofrequency furnace at temperatures up to 1650 °C. They were obtained as main products (≈70 %) embedded in a very hard glass matrix in the form of intense dark green (Pr), orange-brown (Sm), or dark red (Nd) large single crystals, respectively. The stoichiometric composition of Ba4Sm7[Si12N23O][BN3] was verified by a quantitative elemental analysis. According to the single-crystal X-ray structure determinations (Ba4Ln7[Si12N23O][BN3], Z=1, P with Ln=Pr: a=1225.7(1), c=544.83(9) pm, R1=0.013, wR2=0.030; Ln=Nd: a=1222.6(1), c=544.6(1) pm, R1=0.017, wR2=0.039; Ln=Sm: a=1215.97(5), c=542.80(5) pm, R1=0.047, wR2=0.099) all three compounds are built up by a framework structure [Si12N23O]23− of corner-sharing SiX4 tetrahedrons (X=O, N). The oxygen atoms are randomly distributed over the X positions. The trigonal-planar orthonitridoborate ions [BN3]6− and also the Ln(3)3+ are situated in hexagonal cages of the framework (bond lengths Si−(N/O) 169–179 pm for Ln=Pr). The remaining Ba2+ and Ln3+ ions are positioned in channels of the large-pored network. The trigonal-planar [BN3]6− ions have a B−N distance of 147.1(6) pm (for Ln=Pr). Temperature-dependent susceptibility measurements for Ba4Nd7[Si12N23O][BN3] revealed Curie–Weiss behavior above 60 K with an experimental magnetic moment of μexp=3.36(5) μB/Nd. The deviation from Curie–Weiss behavior below 60 K may be attributed to crystal field splitting of the J=9/2 ground state of the Nd3+ ions. No magnetic ordering is evident down to 4.2 K. Die Umsetzung der Lanthanoide Pr, Nd bzw. Sm mit Barium-Metall, BaCO3, Si(NH)2 sowie Poly(boramidimid) in Tiegeln aus Wolfram bei Temperaturen bis 1650 °C im Hochfrequenzofen unter Stickstoff-Atmosphäre führte zur Synthese der drei isotypen Verbindungen Ba4Ln7[Si12N23O][BN3] mit Ln=Pr, Nd bzw. Sm. Die Verbindungen wurden als Hauptprodukte (≈ 70 %) eingebettet in außerordentlich harten glasartigen Phasen in Form großer dunkelgrüner (Pr), orange-brauner (Sm) bzw. dunkelroter (Nd) Einkristalle erhalten. Die Zusammensetzung von Ba4Sm7[Si12N23O][BN3] wurde durch quantitative Elementaranalyse bestätigt. Nach Einkristall-Röntgenstrukturanalysen (Ba4Ln7[Si12N23O][BN3], Z=1, P mit Ln=Pr: a=1225.7(1), c=544.83(9) pm, R1=0.013, wR2=0.030; Ln=Nd: a=1222.6(1), c=544.6(1) pm, R1=0.017, wR2=0.039; Ln=Sm: a=1215.97(5), c=542.80(5) pm, R1=0.047, wR2=0.099) liegt in allen drei Verbindungen eine Raumnetzstruktur eckenverknüpfter SiX4-Tetraeder [Si12N23O]23− vor (X=O, N), in der die Sauerstoffatome statistisch auf die X-Positionen verteilt sind. Die trigonal planaren Orthonitridoborat-Ionen [BN3]6− sowie die Ln(3)3+ sind in hexagonalen Käfigen dieses Gerüstes eingelagert (Bindungslängen Si-(N/O) 169–179 pm, für Ln=Pr). Die verbleibenden Ba2+- sowie Ln3+-Ionen finden sich in den restlichen Kanälen der Gerüststruktur. Die trigonal planaren [BN3]6−-Ionen haben B-N-Bindungslängen von 147.1(6) pm (Wert für Ln=Pr). Temperaturabhängige Suszeptibilitätsmessungen an Ba4Nd7[Si12N23O][BN3] ergaben Curie-Weiss-Verhalten oberhalb von 60 K mit einem experimentell bestimmten magnetischen Moment von μexp=3.36(5) μB /Nd. Die Abweichung vom Curie-Weiss-Verhalten unterhalb von 60 K wird auf Kristallfeld-Aufspaltungen des J=9/2 Grundzustands der Nd3+-Ionen zurückgeführt. Bis 4.2 K konnte keine magnetische Ordnung nachgewiesen werden.Keywords:
Stoichiometry
Barium
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For further study on leaf boron forms of rape (Brassica napus L.) with different boron efficient at flowering stage, two boron efficient (9589,9590), two boron inefficient rape cultivars (9141,95105) and their four F 1 hybrid (95105×9589, 95105×9590, 9141×9589, 9141×9590) were used in this pot experiment. The results showed that the water soluble boron(S B) content and bound boron(B B) content in boron efficient cultivars was lower, while the semi bound boron(SB B)content was higher, on the contrary, in the boron inefficient cultivars, and the results in F 1 hybrid were just between that in boron efficient cultivars and in boron inefficient cultivars. A balance of boron forms was established, which showed boron forms had a close relation with boron efficiency, and it may uncover the physiological mechanism of boron efficiency.
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A micro-structuring of the tungsten plasma-facing surface can strongly reduce near surface thermal stresses induced by ELM heat fluxes. This approach has been confirmed by numerical simulations with the help of ANSYS software. For experimental tests, two 10 × 10 mm2 samples of micro-structured tungsten were manufactured. These consisted of 2000 and 5000 vertically packed tungsten fibres with dimensions of Ø240 µm × 2.4 mm and Ø150 µm × 2.4 mm, respectively. The 1.2 mm bottom parts of the fibres are embedded in a copper matrix. The top parts of the fibres have gaps about of 10 µm so they are not touching each others. The top of all tungsten fibres was electro-polished. A Nd:YAG laser with a pulse duration 1 ms and a pulse repetition frequency of 25 Hz was used to simulate up to 105 ELM-like heat pulses. No damage on either of the micro-structured tungsten samples were observed. Neon plasma erosion rate and fuel retention of the micro-structured tungsten samples were almost identical to bulk tungsten samples.
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This paper presents a method in which the content of calcium and barium all be measured with only one test specimen dissolution. Test specimen shall be dissolved with acid. The solution shall be used for analyzing calcium and Barium. Both calcium and barium shall be measwred by EDTA titrametric method.
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Abstract Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or β) is stable at ambient conditions. Through experiment, we quantify the relative stability of α‐boron and β‐boron as a function of temperature. The ground‐state energies of α‐boron and β‐boron are nearly identical. For all temperatures up to 2000 K, the complicated β‐boron structure is more stable than the simpler α‐boron structure at ambient pressure. Below 1000 K, β‐boron is entropically stabilized with respect to α‐boron owing to its partially occupied sites, whereas at higher temperatures β‐boron is enthalpically stabilized with respect to α‐boron. We show that α‐boron only becomes stable on application of pressure.
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