Sm（0.5）Sr（0.5）Co（0.4）M（0.6）O3（M=Co,Mn,Fe）作为IT-SOFCs阴极的结构与性能

通过X射线衍射(XRD)、热重、热膨胀、电导率以及交流阻抗等测试方法,研究了Sm0.5Sr0.5Co0.4M0.6O3(M=Co,Mn,Fe;分别简写为SSCC,SSCM,SSCF)作为中低温固体氧化物燃料电池(IT-SOFCs)阴极的结构与性能.研究表明,同相法合成的Sm0.5Sr0.5Co0.4M0.6O3均为正交钙钛矿型结构,材料的结构参数和性能都与M元素半径及M-O的键能有关.晶胞参数随着Co、Mn、Fe的顺序增大.材料的氧空位浓度、热膨胀系数、电导率、电极催化活性随着Co、Fe、Mn的顺序降低.同时由于SSCM较低的氧空位浓度,使得电极反应受到氧在电极内的扩散过程控制,具有较差的电极催化性能,而SSCC和SSCF较高的氧空位浓度,电极反应同时受到电极表面氧还原反应和氧离子在电极中的扩散过程混合控制.由于SSCF具有较高的氧扩散系数,使得700 ℃以上SSCF电极表面氧还原电阻(ASR)也低于SSCC的,因而出现了SSCF的总电极催化活性高于SSCC的现象.     

The reaction mechanism of a M (M = Mn,Fe, Co and Ni) atom inserted into a Fe8O12 cage

Research on Chemical Intermediates - The reaction process of a M (M?=?Mn, Fe, Co and Ni) atom associated and then interpolated into a Fe8O12 cage is calculated by using a PBE...     

Hydrothermal Synthesis and Magnetic Properties ofSmCr0.5M0.5O3(M=Fe and Mn) Micro-plates

Nanostructured B-site Fe and Mn doped SmCrO₃ was prepared by mild hydrothermal growth. The as-prepared crystals are mainly micrometer-scale plates, ranging from rhombus(SmCr_0.5Fe_0.5O₃) to elongated he- xagonal(SmCr_0.5Mn_0.5O₃), and finally to well-edged rectangular(SmCr_0.17Mn_0.5Fe_0.33O₃) plates. Fe and Mn doped SmCrO₃ crystals are indexed into Pbnm space group. The cell parameters of SmCr_0.5Fe_0.5O₃ are slightly smaller than that of pristine SmCrO₃. Binding energy analysis of Cr, Mn and Fe in SmCr_0.17Mn_0.5Fe_0.33O₃ sample indicates that they all possess +3 oxidation states. Temperature dependent magnetization of the as-prepared samples presents obviously stronger ferromagnetic interactions than the undoped counterparts. This work represents a remarkable development for hydrothermal synthesis into fabricating perovskite oxide crystals with uniform distribution of doping ions.     

Sr3Mn2O6 and Sr3FeMnO6 for oxygen and hydrogen evolution electrocatalysis

Journal of Solid State Electrochemistry - Quasi-two-dimensional oxides Sr3Mn2O6 and Sr3FeMnO6 have been synthesized and their bifunctional electrocatalytic activity toward both half-reactions of...     

Analogues of the Lavallo-Grubbs compound Fe3(C8H8)3: equilateral, isosceles, and scalene metal triangles in trinuclear cyclooctatetraene complexes M3(C8H8)3 of the first row transition metals (M = Ti, V, Cr, Mn, Fe, Co, and Ni)

The trinuclear derivative Fe(3)(C(8)H(8))(3) was synthesized in 2009 by Lavallo and Grubbs via the reaction of Fe(C(8)H(8))(2) with a bulky heterocyclic carbene. This fascinating structure is the first example of a derivative of the well-known Fe(3)(CO)(12) in which all 12 carbonyl groups have been replaced by hydrocarbon ligands. The density functional theory predicts a structure having a central Fe(3) equilateral triangle with ～2.9 ? Fe-Fe single bonded edges bridged by η(5),η(3)-C(8)H(8) ligands. This structure is close to the experimental structure, determined by X-ray crystallography. The related hypoelectronic M(3)(C(8)H(8))(3) derivatives (M = Cr, V, Ti) are predicted to have central scalene M(3) triangles with edge lengths and Wiberg bond indices (WBIs) corresponding to one formal single M-M bond, one formal double M═M bond, and one formal triple M≡M bond. For Mn(3)(C(8)H(8))(3), both a doublet structure with one Mn═Mn double bond and two Mn-Mn single bonds in the Mn(3) triangle, and a quartet structure with two Mn═Mn double bonds and one Mn-Mn single bond are predicted. The hyperelectronic derivatives M(3)(C(8)H(8))(3) have weaker direct M-M interactions in their M(3) triangles, as indicated by both the M-M distances and the WBIs. Thus, Ni(3)(C(8)H(8))(3) has bis(trihapto) η(3),η(3)-C(8)H(8) ligands bridging the edges of a central approximately equilateral Ni(3) triangle with long Ni···Ni distances of ～3.7 ?. The WBIs indicate very little direct Ni-Ni bonding in this Ni(3) triangle and thus a local nickel environment in the singlet Ni(3)(C(8)H(8))(3) similar to that observed for diallylnickel (η(3)-C(3)H(5))(2)Ni.     

Mössbauer study of Al6 (Fe,Mn) formation in Al-rich Al−Fe−Mn alloys

Al–Fe–Mn alloys containing 0.5 wt. % iron and 0–3.0 wt. % manganese were prepared at different cooling rates from 0.1 to 500 K/s and studied by Mössbauer spectroscopy. Beyond the usual phase analysis, it was found that the presence of manganese is responsible for the decrease of the quadrupole splitting and isomer shift of the Al₆(Fe,Mn) phase, compared to those of Al₆Fe. It was also shown that the Mössbauer parameters are characteristic of the average manganese content of Al₆(Fe,Mn) only if there are no substantial fluctuations of the Fe/Mn ratio in the Al₆(Fe,Mn) phase. Accurate Mössbauer parameters for the Al₆Fe phase were also determined.     

Magnetic properties of the layered compounds Ca2Mn3O8 and Cd2Mn3O8

Ca₂Mn₃O₈ and Cd₂Mn₃O₈, which contain Mn⁴⁺ monolayers, have been prepared and characterized. Their magnetic susceptibility and electron paramagnetic resonance (EPR) behavior have been examined in detail. The Mn⁴⁺ moments in both Ca₂Mn₃O₈ and Cd₂Mn₃O₈ order antiferromagnetically near 60 and 10°K, respectively. Although the Néel temperature in Ca₂Mn₃O₈ is in reasonable agreement with molecular-field theory, that in Cd₂Mn₃O₈ is well below its expected value. It is proposed that these results, as well as those in the calcium manganite series CaMnO₃ → Ca₂MnO₄, may reflect the chemical influence of the divalent cation in modifying the MnO covalent mixing.     

Die Kristallstrukturen von Mn5O8 und Cd2Mn3O8

The crystal structures of Mn₅O₈ and Cd₂Mn₃O₈ are determined from single crystal and high resolution X-ray powder data. Both structures have very similar monoclinic unit cells, space group C–C2/m, and are isotypic: Hence, the true formula of Mn₅O₈ is MnMnO₈. The crystal structure consists of pseudohexagonal Mn^IV sheets (bc) with similar oxygen sheets on either side, giving a distorted octahedral coordination to the Mn^IV. As every fourth Mn^IV is missing in these “main layers”, their composition becomes Mn₃O₈, and chains of coordination octahedra linked by common edges become distinct. Above and below the empty Mn^IV sites are either Mn^II or Cd^II completing the composition MnMnO₈ or Cd₂Mn₃O₈ respectively. Examples of similar “double layer” structures are given.     

A structural analysis of {M4O4} cubanes where M = Mn and Fe

The structures of the M4O4 units found in manganese and iron cubanes are analysed. The model used is that established previously for cobalt and nickel cubanes based on a distortion of the cube by compression of the oxygen atoms along a body diagonal. Further distortion which maintains a S4 or, less frequently, a C3 axis is generally seen. In spite of the distortion, average M-M distances in a cubane are quite constant for a given oxidation state and generally decrease as the metal is oxidised. The angles at the oxygen atoms increase from 90 degrees for the ideal cube to around 97 degrees . For metal oxidation states above or equal to +iii micro3-hydroxo ligands transform to micro3-oxo ligands. Ligands such as carboxylates which can bridge diagonal faces of the cube are generally seen with higher oxidation states.     

水合石榴石Sr3Fe2(OH)12的温和水热合成与M(o)ssbauer谱研究

在温和水热体系中合成出单相水合石榴石Ｓｒ３Ｆｅ２（ＯＨ）１２．产物在５７３Ｋ左右经历快速的与Ｓｒ最近邻的ＯＨ－断裂与分解过程，在空气或氧气中焙烧出现从Ｆｅ（Ⅲ）到Ｆｅ（Ⅳ）的氧化．骨架Ｆｅ离子价态变化直接决定分解过程及产物的结构类型．采用Ｍｏｓｓｂａｕｅｒ谱联用ＸＰＳ法测出Ｓｒ－Ｆｅ水合石榴石晶格中存在２种八面体Ｆｅ（ＯＨ）６．     

半水榴石型化合物Sr_6Sb_4M_3O_(14)(OH)_(10)(M=Co,Mn)的合成、结构与性质

在强碱性水热条件下合成了两种新化合物Sr6Sb4Co3O14(OH)10(SSC)与Sr6Sb4Mn3O14(OH)10(SSM).采用粉末X射线衍射数据,通过Rietveld方法进行了结构分析,讨论了金属离子的拓扑结构.两种化合物均为石榴石-水榴石相关结构,空间群I43d,晶胞参数a分别为1.30634(2)nm(SSC)和1.31367(1)nm(SSM).结构中,SbO6八面体与MO4(M=Co,Mn)四面体共顶点连接,Sb5+-M2+(M=Co,Mn)离子表现为ctn即C3N4型的拓扑结构.拓扑结构中,Sb5+为三连接,过渡金属离子M2+(M=Co,Mn)为四连接.Sb5+离子的拓扑结构为体心立方,而M2+(M=Co,Mn)分布呈类风扇状,相互连接形成thp型拓扑结构(即Th3P4中Th原子之间连接关系).过渡金属离子的分布与化合物表现出的磁性质密切相关,Co2+(Mn2+)间存在反铁磁相互作用.Sr6Sb4Co3O14(OH)10在低温下表现出反铁磁倾斜有序.Sr6Sb4Co3O14(OH)10和Sr6Sb4Mn3O14(OH)10在高温下发生分解,产物主相为双钙钛矿Sr2(Sb,M)2O6(M=Co,Mn).     

La0.8Sr0.2Mn1-xNixO3微波吸收特性

采用溶胶-凝胶法制备La0.8Sr0.2Mn1-xNixO3(y=0.12,0.14),用X射线,扫描电镜对样品结构和形貌进行了表征,用HP8722型矢量网络分析仪测定样品2~18 GHz损耗角正切及微波吸收特性曲线,发现y=0.14,样品厚度2.0 mm,吸收峰值达到了14 dB,10 dB以上吸收带宽达到了3.5 GHz。对该材料的电磁损耗机理进行了研究,发现在频率12.08 GHz附近有突变发生,2~12.08 GHz频段损耗主要以介电损耗为主,12.08~18 GHz频段损耗是以磁损耗为主。     

Synthesis and structural characterization of high spin M/Cu (M = Mn, Fe) heterobimetallic and Fe/Cu2 trimetallic phosphinoamides

The heterobimetallic complexes [Mn((i)PrNPPh(2))(3)Cu((i)PrNHPPh(2))] (1) and [Fe((i)PrNPPh(2))(3)Cu((i)PrNHPPh(2))] (2) have been synthesized by the one pot reaction of LiN(i)PrPPh(2), MCl(2) (M = Mn, Fe), and CuI in high yield. Addition of excess CuI into 2 or directly to the reaction mixture led to the formation of a heterotrimetallic [Fe((i)PrNPPh(2))(3)Cu(2)((i)PrNPPh(2))] (3) in good yield. Complexes 1-3 have been characterized by means of elemental analysis, paramagnetic (1)H NMR, UV-vis spectroscopy, cyclic voltammetry, and single crystal X-ray analysis. In all three complexes, Mn or Fe are in the +2 oxidation state and have a high spin electron configuration, as evidenced by solution Evans' method. In addition, the oxidation state of Fe in complex 3 is confirmed by zero-field (57)Fe M?ssbauer spectroscopy. X-ray crystallography reveals that the three coordinate Mn/Fe centers in the zwitterionic complexes 1-3 adopt an unusual trigonal planar geometry.     

Syntheses and Crystal Structures of Ca3Fe2(SeO3)6 and Sr3Fe2(SeO3)6

The new compounds M₃Fe₂(SeO₃)₆ (M = Ca, Sr) were obtained as crystalline precipitates from aqueous solutions of the respective ions, kept in Teflon-coated vessels at a temperature of 227(2)°C for several days. The crystal data are: space group R3 c, a = 8.531(2), 8.802(2) Å; c = 38.89(1), 39.00(1) Å; V = 2451.1, 2616.7 ų, Z = 6. The crystal structures have been refined by single-crystal X-ray diffraction methods to R1 = 0.021, 0.023; wR2 = 0.038, 0.039. The framework structure is built up by two types of FeO₆ octahedra as well as by MO₈ groups and SeO₃ trigonal pyramids by corner- and edge-linkage of the polyhedra.