Darstellung, Isolierung und Charakterisierung von Ba@C74
摘要:
For the first time Ba@C-74 has been isolated in pure form. The title compound has been isolated from a raw material, produced in a radio-frequency-furnace, consisting of a mixture of fullerenes and endohedral Bariumfullerenes. Ba@C-74 was separated by two stage sublimation and subsequent high-performance liquid chromatography (HPLC) using a Buckyprep column. The capacity factor for Ba@C-74 is 6.0. Its endohedral character has been deduced from the fragmentation pattern obtained by time-of-night mass spectroscopy while the composition has been confirmed by comparison of calculated and measured isotopic pattern of the parent peak. Further characterization was performed by VIS/NIR-spectroscopy and electron-paramagnetic-resonance spectroscopy (EPR).
Single-step low-temperature synthesis routes for (Ba, Ce, Gd) hexaborides and their thermionic emission properties
作者:Muhammad M. Hasan、Erich Kisi、Heber Sugo
DOI:10.1016/j.jallcom.2022.165474
日期:2022.9
high chemical stability and low work function have recently attracted much interest as promising thermionic cathodes. Their synthesis at low temperatures without post-synthesis purification treatments is still a significant challenge. The present work demonstrates a simple synthesis technique to produce pure barium, cerium and gadolinium hexaborides (BaB6, CeB6, and GdB6). For each hexaboride, a batch
作者:L. G. Sevast'yanova、P. E. Kazin、O. V. Kravchenko、S. A. Kuz'michev、Ya. G. Ponomarev、K. P. Burdina、B. M. Bulychev
DOI:10.1023/a:1026163230359
日期:——
Dense samples of pure magnesium boride and of the compositions Mg((1-x))A(x)B(2) (A = Na, K, Ca, Sr, Ba, Sn, Ti; 0.05 < x < 0.15) were prepared by sintering and using high temperature-high pressure treatment. The lattice parameters of most of the doped MgB2 samples vary only slightly as compared to those of the pure MgB2 irrespective of the sample preparation procedure, high temperature-high pressure treatment conditions, and the amount of dopant, thus indicating the absence of extended solid solution regions. The superconducting transition temperatures of all the samples did not exceed the value characteristic of MgB2 (39 +/- 1 K). The results obtained for the dense MgB2 samples using the Andreev reflection and tunneling spectroscopies confirm the two-gap nature of superconductivity in magnesium diboride and point to analogy between the superconductivity mechanisms in this compound and in cuprates.