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361.
《Analytical letters》2012,45(8):1553-1564
Abstract The reaction of Di-2-pyridyl-ketone 2-furoylhydrazone (DPFH) with scandium in an aqueous ethanolic medium (4% v/v of ethanol) has been studied. A spectrofluorimetric method based on the formation of a fluorescent complex is proposed for the determination of scandium. With excitation at 387 nm, the scandium (III) chelate has an emission maximum at 492 nm; the reaction is carried out at pH 6.5–7.5. The accuracy and precision of the method are demonstrated by the analysis of synthetic mixtures containing various amounts of scandium. 10 – 140 ng/ml of scandium can be determined with a relative error of ±1.3%. 相似文献
362.
La0.8Sr0.2Fe1-xScxO3-δ催化剂的制备、表征及甲烷催化燃烧性能 总被引:1,自引:0,他引:1
采用甘氨酸-硝酸盐溶液燃烧法制备了钙钛矿型氧化物催化剂La0.8Sr0.2Fe1-xScxO3-δ (LSFS, x=0, 0.3,0.4, 0.5, 0.6, 0.8, 1), 利用X射线衍射(XRD)、H2程序升温还原(H2-TPR)、扫描电子显微镜(SEM)和比表面积测试等手段对催化剂进行了系统表征, 并在常压微型固定床反应器上考察了催化剂对甲烷燃烧的催化性能. 结果表明, 经空气气氛下900 °C煅烧5 h制备的LSFS均具有单一的钙钛矿结构, 在La0.8Sr0.2FeO3-δ (LSF)中掺杂Sc有助于改善催化剂的抗烧结性能, 提高催化剂的比表面积. 当LSF 中的Sc 掺杂量为0.4-0.6 时, 所形成的LSFS表现出良好的甲烷催化燃烧活性, 其中Sc 掺杂量为0.5 时, 其起燃温度(T10)和完全转化温度(T90)分别为406和563 °C, 与La0.8Sr0.2FeO3-δ和La0.8Sr0.2ScO3-δ相比, T10分别降低了14和87 °C; T90分别降低了59和95 °C. 相似文献
363.
Frédéric-Georges Fontaine 《Journal of organometallic chemistry》2006,691(22):4595-4600
Reaction of 2 equiv. of (C4Me4P)Li(tmeda) (tmeda = tetraethylenediamine) with 1 equiv. of ScCl3(THF)3 gave the new compound (η5-C4Me4P)2ScCl2Li(tmeda) (1), which was characterized by X-ray crystallography. A phospholyl moiety in 1 is labile, as demonstrated by reactions of 1 with LiCH(SiMe3)2 and Cp∗Li (Cp∗ = C5Me5) to afford, respectively, (η5-Me4C4P)Sc[CH(SiMe3)2]Cl2Li(tmeda) (4) and (η5-Me4C4P)Cp∗ScCl2Li(tmeda) (5). Attempts to generate alkyl derivatives of the general type (η5-C4Me4P)2ScR (R = alkyl) were unsuccessful. 相似文献
364.
Da-Chun Pan 《Journal of solid state chemistry》2006,179(4):1016-1021
Two new ternary bismuthides, La3MgBi5 and LaLiBi2, have been prepared by solid-state reactions of the corresponding pure metals in welded niobium tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. La3MgBi5 crystallizes in the hexagonal space group P63/mcm (No.193) with cell parameters of , , , and Z=2. LaLiBi2 belongs to tetragonal space group P4/nmm (No.129) with cell parameters of , ,, and Z=2. The structure of La3MgBi5 is of the ‘‘anti’’ Hf5Sn3Cu type, and features 1D linear Bi− anionic chains and face-sharing [MgBi6/2]7− octahedral chains. The structure of LaLiBi2 is isotypic with HfCuSi2, and is composed of 2D Bi− square sheets and 2D LiBi layers with La3+ ions as spacers. Band calculations indicate that both compounds are metallic. 相似文献
365.
Tae-Soo You 《Journal of solid state chemistry》2010,183(6):1258-214
Reported are the synthesis and the structural characterization of four new polar intermetallic phases, which exist only with mixed alkaline-earth and rare-earth metal cations in narrow homogeneity ranges. (Sr1-xCax)5In3Ge6 and (Eu1-xYbx)5In3Ge6 (x≈0.7) crystallize in the orthorhombic space group Pnma with two formula units per unit cell (own structure type, Pearson symbol oP56). The lattice parameters are as follows: a=13.109(3)-13.266(3) Å, b=4.4089(9)-4.4703(12) Å, and c=23.316(5)-23.557(6) Å. (Sr1-xCax)3In2Ge4 and (Sr1-xYbx)3In2Ge4 (x≈0.4-0.5) adopt another novel monoclinic structure-type (space group C2/m, Z=4, Pearson symbol mS36) with lattice parameters in the range a=19.978(2)-20.202(2) Å, b=4.5287(5)-4.5664(5) Å, c=10.3295(12)-10.3447(10) Å, and β=98.214(2)-98.470(2)°, depending on the metal cations and their ratio. The polyanionic sub-structures in both cases are based on chains of InGe4 corner-shared tetrahedra. The A5In3Ge6 structure (A=Sr/Ca or Sr/Yb) also features Ge4 tetramers, and isolated In atoms in nearly square-planar environment, while the A3In2Ge4 structure (A=Sr/Ca or Eu/Yb) contains zig-zag chains of In and Ge strings with intricate topology of cis- and trans-bonds. The experimental results have been complemented by tight-binding linear muffin-tin orbital (LMTO) band structure calculations. 相似文献
366.
Thomas Harmening Leo van Wüllen Hellmut Eckert Prof. Dr. Ute Ch. Rodewald Rainer Pöttgen Prof. Dr. 《无机化学与普通化学杂志》2010,636(6):972-976
The metal‐rich silicide Sc4Pt7Si2 was synthesized by arc‐melting. Sc4Pt7Si2 crystallizes with its own structure type, space group Pbam. The structure was refined from single‐crystal X‐ray diffractometer data: a = 647.6(1), b = 1617.1(3), c = 398.96(9) pm, wR2 = 0.0495, 807 F2 values and 42 variables. Sc4Pt7Si2 is an intergrowth structure of slightly distorted ScPtSi (TiNiSi type) and ScPt (CsCl type) related slabs. The silicon atoms have the typical coordination number 9 (4 Sc + 5 Pt) in the form of a tricapped trigonal prism. Together, the platinum and silicon atoms build up a complex three‐dimensional [Pt7Si2] network with short Pt–Si (238–246 pm) and Pt–Pt (282–303 pm) distances. The scandium atoms fill distorted square prismatic or pentagonal prismatic voids within this network, also with short Sc–Pt distances (276–308 pm). The structural difference of these two scandium species is reflected by substantial discrepancies in 45Sc chemical shifts. The quadrupolar interaction parameters that were estimated from the nutation behavior of the two signals were used for an assignment to the two sites. 相似文献
367.
The electronic structure and magnetic properties of the Heusler compound Co2ScP have been investigated by the generalized gradient approximation based on density functional theory. The results show that the ground state phase of the Co2ScP compound possesses AlCu2Mn-type crystal structure and exhibits half-metallic ferrimagnetism. The total spin moment is 2 μB at the equilibrium lattice constant a0=5.83 Å, which agrees with the Slater–Pauling rule. The spin-up electrons are metallic, but the spin-down bands are semiconductor with a gap of 0.55 eV, and the spin-flip gap is of 0.07 eV. 相似文献
368.
Zhexin Tang Tongtong Shang Han Xu Ting Lin Ang Gao Weiguang Lin Xinyan Li Shiyu Wang Botao Yu Fanqi Meng Qinghua Zhang Xuefeng Wang Dong Su Qingbo Meng Lijun Wu Lin Gu Ce-Wen Nan 《Angewandte Chemie (International ed. in English)》2023,62(7):e202216898
Physical properties of materials are mainly determined by valence electron configurations, where different valence shells would induce divergent phenomena. In compounds containing Sc2+, 3d electron occupancy is expected, the same as other transition metal atoms like Ti3+. But this situation still awaits experimental verification in inorganic materials. Here, we selected ScS to measure the valence electron density and orbital population of Sc2+ through delicate quantitative convergent-beam electron diffraction. With the absence of 3d orbital features around Sc-atom sites and the nearly bare population of t2g orbital, the unintuitive occupation of 4s orbital in Sc2+ is concluded. It should be the first time to report such a special electron configuration in a transition metal compound, in which 4s rather than 3d orbital is preferred. Our findings reveal the distinct behavior of Sc and probable ways to modulate material properties by controlling electron orbitals. 相似文献