- Ca2LiC3H: A new complex carbide hydride phase grown in metal flux
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The reaction of carbon and CaH2 in a calcium/lithium flux mixture produces crystals of the new compound Ca2LiC3H. This phase forms with a new structure type in tetragonal space group P4/mbm (a = 6.8236(1) A, c = 3.7518(1) A, Z = 2, R1 = 0.0151). This is a stuffed variant of the Cs2(NH2)N3 structure, containing hydride anions in octahedral sites; the structure determination by single-crystal X-ray diffraction surprisingly allowed the hydrogen to be detected. The Ca2LiC3H structure also features the rarely seen C34- carbide anion; the protolysis reaction of this compound with ammonium chloride produces C 3H4. The electronic properties of Ca2LiC 3H were studied by quantum-chemical calculations including band structure and electron localization function (ELF) analysis; the phase is a charge-balanced semiconductor with a calculated band gap of 0.48 eV. This is in agreement with 7Li, 13C, and 1H MAS NMR data, which show resonances in the ionic region instead of the Knight shifted region. ELF analysis of the theoretical nonhydrided Ca2LiC3 structure confirms the ability of these calculations to properly locate hydrides and supports the structural model based on X-ray diffraction data.
- Lang, David A.,Zaikina, Julia V.,Lovingood, Derek D.,Gedris, Thomas E.,Latturner, Susan E.
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- Production of calcium carbide from fine biochars
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Rising from the ashes: Fine chars produced from biomass can be used as a feedstock for the production of CaC2 in an autothermal process that operates at a temperature 500 °C lower than the traditional electric arc process and with greatly reduced reaction time (see scheme for the reaction of CaO and C forming CaC2).
- Li, Guodong,Liu, Qingya,Liu, Zhenyu,Zhang, Z. Conrad,Li, Chengyue,Wu, Weize
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- On the coexistence of tetragonal and monoclinic CaC2: Structural and spectroscopic studies on alkaline earth metal acetylides, MC2 (M = Ca, Sr, Ba)
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The alkaline earth acetylides CaC2, SrC2 and BaC2 can be considered to occur in three polymorphic structures each. The monoclinic low-temperature form, the tetragonal form, and the cubic high-temperature form. No deviation from axial symmetry is obtained for the C22- ions in the tetragonal structure determinations, as confirmed by X-ray single-crystal structures and 13C MAS NMR studies. The CaC2 samples prepared by us were always a mixture of monoclinic and tetragonal phase. Their Raman spectra exhibited two distinct C2 streching vibrations. Problems arising from the coexistence of these two phases for the interpretation of 13C MAS NMR spectra are discussed.
- Reckeweg, Olaf,Baumann, Andreas,Mayer, Hermann A.,Glaser, Jochen,Meyer, H. -Jürgen
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p. 1686 - 1692
(2008/10/08)
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- Use of nitric oxide-releasing agents to treat impotency
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A method of treatment for impotency is provided. The method involves the administration of nitric oxide by a nitric oxide-releasing agent capable of providing a penile erection-inducing amount of nitric oxide to the corpus cavernosum of the penis of an impotent male animal. Also provided is a nitric oxide delivery means for use in the method.
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- BEHAVIOUR OF METAL CARBONATES IN SPECTROSCOPIC ARC, I. PRELIMINARIES. ROLE OF INSTABILITY OF CARBONATES
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Seven kinds of metal carbonates of different stability were studied in a.c. polarized arc, in Ar atmosphere, on mixtures with carbon powder of a molar fraction of 0.3 metal carbonate.The higher the thermal stability of the carbonate, the lower quantities of carbon oxides, measured by gas analytical methods were produced in the arc.The less stable carbonates suffer simple thermal decomposition, while in the case of Li2CO3 and BaCO3, carbon powder have a direct reducing effect.Under the conditions of the arc a substantial volume of CO was formed too, mainly according to the equation CO2 + C = 2 CO.Of the less stable carbonates, unstable metal oxides were formed, giving rise to further oxidation reactions.In the case of several carbonates, carbide formation could also be proved by gas analytical methods.Processes proceeding in the arc, their place, the depth of the reaction zone, etc., could be calculated and followed on the basis of data measured.Model substances for further investigations were chosen on the bases of these experiences.
- Szabo, Z. L.,Bertalan, E.,Tatar, E.
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p. 193 - 208
(2007/10/02)
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