Sc6MTe2 (M = Mn, Fe, Co, Ni): members of the flexible Zr6CoAl2-type family of compounds

The compounds Sc6MTe2 (M = Mn, Fe, Co, Ni) have been prepared by high-temperature solid-state techniques and their structures determined to be hexagonal P62m (No. 189), Z = 1, a = 7.662(1) A, 7.6795(2) A, 7.6977(4) A, 7.7235(4) A and c = 3.9041(9) A, 3.8368(2) A, 3.7855(3) A, 3.7656(3) A for M = Mn, Fe, Co, and Ni, respectively. Crystal structures were refined for M = Fe and Ni, while M = Mn and Co were assigned as isostructural on the basis of powder diffraction data. The Sc6MTe2 compounds belong to a large family with the Zr6CoAl2-type structure, an ordered variant of the Fe2P structure. The structure contains confacial tricapped trigonal prisms of scandium centered alternately by the late transition metal or tellurium atoms. The Sc6MTe2 compounds are the electron-poorest examples of this structure type. Extended Hückel band calculations for M = Fe and Ni show that both compounds exhibit largely 1D metal-metal bonding and are predicted to be metallic.     

From nitrides to carbides: topotactic synthesis of the eta-carbides Fe3Mo3C and Co3Mo3C

The molybdenum bimetallic interstitial carbides Fe(3)Mo(3)C and Co(3)Mo(3)C have been synthesized by temperature-programmed reaction (TPR) between the molybdenum bimetallic interstitial nitrides Fe(3)Mo(3)N and Co(3)Mo(3)N and a flowing mixture of CH(4) and H(2) diluted in Ar. These compounds have been characterized by X-ray diffraction, laser Raman spectroscopy, elemental analysis, energy dispersive analysis of X rays, thermal analysis (in air) and scanning electron microscopy (field emission). Their structures have been refined from X-ray powder diffraction data. These carbides crystallize in the cubic system, space group Fd3m[a= 11.11376(6) and 11.0697(3)[Angstrom] for Fe and Co compounds, respectively].     

常温常湿条件下Au/MeO~x催化剂上CO氧化性能

利用共沉淀法制备了Au/MeO~x催化剂(Me=Al,Co,Cr,Cu,Fe,Mn,Ni,Zn)。在常温常湿条件下,考察了不同氧化物负载的金基催化剂的CO氧化性能。结果表明,氧化物种类对催化剂的活性和稳定性均有较大的影响。Cu,Mn,Cr等氧化物负载的金基催化剂的活性较差,而Zn,Fe,Co,Ni,Al等金属氧化物负载的金基催化剂可将CO完全氧化,又具有一定的稳定性,在相同反应条件下,CO完全转化时的稳定性顺序为Au/ZnO>Au/α-Fe~2O~3>Au/Co~3O~4>Au/γ-Al~2O~3≈Au/NiO。还发现水对Au/MnO~x催化剂的活性和稳定性有负作用,而对180℃焙烧制备的Au/ZnO-180催化剂的活性和稳定性均有明显的湿度增强作用。     

CO氧化反应中H2O对MOx和Au/MOx催化性能的影响

过渡金属氧化物［1,2］及负载型贵金属催化剂［3～13］是催化氧化消除CO的有效催化剂,一直是研究的热点. 虽然对MOx和Au/MOx上CO的氧化性能研究得较多,但大多是在无水条件下进行的;涉及催化剂抗水性能的报道较少［3,9,10］,且仅限于对催化剂活性的研究. Haruta等［3］对Au/Fe2O3,Au/Co3O4和Au/TiO 2等体系开展了一些工作, 认为水对CO氧化活性有促进作用. 本文重点考察了水对MOx(M=Al,Ca,Co,Cr,Cu,Fe,La,Mn,Ni和Zn)催化剂上CO氧化活性的影响,以及水对Au/MOx 催化剂活性及稳定性的影响.     

REMGa3Ge and RE3Ni3Ga8Ge3 (M = Ni, Co; RE = rare-earth element): new intermetallics synthesized in liquid gallium. X-ray, electron, and neutron structure determination and magnetism

New quaternary intermetallic phases REMGa(3)Ge (1) (RE = Y, Sm, Tb, Gd, Er, Tm; M = Ni, Co) and RE(3)Ni(3)Ga(8)Ge(3) (2) (RE = Sm, Gd) were obtained from exploratory reactions involving rare-earth elements (RE), transition metal (M), Ge, and excess liquid Ga the reactive solvent. The crystal structures were solved with single-crystal X-ray and electron diffraction. The crystals of 1 and 2 are tetragonal. Single-crystal X-ray data: YNiGa(3)Ge, a = 4.1748(10) A, c = 23.710(8) A, V = 413.24(2) A(3), I4/mmm, Z = 4; Gd(3)Ni(3)Ga(8)Ge(3), a = 4.1809(18) A, c = 17.035(11) A, V = 297.8(3) A(3), P4/mmm, Z = 1. Both compounds feature square nets of Ga atoms. The distribution of Ga and Ge atoms in the REMGa(3)Ge was determined with neutron diffraction. The neutron experiments revealed that in 1 the Ge atoms are specifically located at the 4e crystallographic site, while Ga atoms are at 4d and 8g. The crystal structures of these compounds are related and could be derived from the consecutive stacking of disordered [MGa](2) puckered layers, monatomic RE-Ge planes and [MGa(4)Ge(2)] slabs. Complex superstructures with modulations occurring in the ab-plane and believed to be associated with the square nets of Ga atoms were found by electron diffraction. The magnetic measurements show antiferromagnetic ordering of the moments located on the RE atoms at low temperature, and Curie-Weiss behavior at higher temperatures with the values of mu(eff) close to those expected for RE(3+) free ions.     

Thermodynamic analysis of (Ni,Fe)3Al formation by mechanical alloying

(Ni, Fe)₃Al intermetallic compound was synthesized by mechanical alloying (MA) of Ni, Fe and Al elemental powder mixtures of composition Ni₅₀Fe₂₅Al₂₅. Phase transformation and microstructure characteristics of the alloy powders were investigated by X-ray diffraction (XRD). The results show that mechanical alloying resulted in a Ni (Al, Fe) solid solution. By continued milling, this structure transformed to the disordered (Ni, Fe)₃Al intermetallic compound. A thermodynamic model developed on the basis of extended theory of Miedema is used to calculate the Gibbs free-energy changes. Final product of MA is a phase having minimal Gibbs free energy compared with other competing phases in Ni–Fe–Al system. However in Ni–Fe–Al system, the most stable phase at all compositions is intermetallic compound (not amorphous phase or solid solution). The results of MA were compared with thermodynamic analysis and revealed the leading role of thermodynamic on the formation of MA product prediction.     

纳米Co-Sn金属间化合物的合成、表征及电化学吸放锂行为

用溶剂热法合成了三种纳米尺寸的Co-Sn金属间化合物, 即CoSn2、CoSn和Co3Sn2, 并研究了它们作为锂离子二次电池新型负极材料的电化学性能. 合成的粉末经过了X射线衍射(XRD), 透射电镜(TEM)和场发射扫描电镜(FESEM)的表征. 研究发现, 这三种金属间化合物均显示出较高的充放电稳定性. 由于低的锂离子扩散速率, 在嵌锂过程中锂离子不能深入到晶粒内部, 导致它们的电化学活性较低, 尤其是Co3Sn2, 其首次充电容量仅为 93 mAh•g−1.     

LiCl-KCl-LaCl3熔盐体系中La(III)的电化学行为

在773 K条件下,研究了La（III）在LiCl-KCl熔盐中W和Ni电极上的电化学行为。La（III）还原反应是一步三电子转移的准可逆反应;通过在Ni电极上直接电沉积La的方法可以获得La-Ni金属间化合物;恒电位电解可以获得含三种金属间化合物（LaNi₅、La₇Ni₁₆和La₂Ni₃）的La-Ni合金层,并且通过X射线衍射仪（XRD）和扫描电镜-能谱分析仪（SEM-EDS）确定物相并表征结构。采用开路计时电位法估算了LaNi₅金属间化合物的标准生成吉布斯自由能。揭示了恒电位电解方法是制备La-Ni镀层合金以及提取熔盐中La的有效方法。     

Preparation and characterization of Fe_3O_4/Au composite particles

Colloid gold with different sizes has been widely used in immunoassay and nucleic acid detection mainly because of their properties for immobilization of biomolecules, such as antibodies and oligonucleo-tides, through chemical reactions via active group SH on the biomolecules. Magnetic particles modified with various chemical groups on their surface can not only exhibit good magnetic responsiveness to an external magnetic field but also immobilize biomolecules through these chemical groups. As…     

Wasserstoffaufnahme und magnetisches Verhalten der intermetallischen Phasen Ti2(Ni,Co) und Ti2(Ni,Fe)

Hydrogen absorption by the intermetallic compounds Ti₂(Ni,Co) and Ti₂(Ni,Fe) with Ti₂Ni-structure (O _h ⁷ -Fd3m) is accompanied by an increase of the volume of the unit cell without any structural change, while the maximum value of absorbed hydrogen is practically independent of the alloy composition. By taking up hydrogen, the intermetallic compounds, showingPauli spin paramagnetism with complex temperature dependence, become either temperature independent paramagnetic [hydrides of Ti₂(Ni,Co)] or strongly temperature dependent paramagnetic, following a modifiedCurie-Weiss-Law [hydrides of Ti₂(Ni,Fe)], respectively.

Herrn Prof. Dr.H. Bittner zum 60. Geburtstag gewidmet.     

有序介孔碳负载Fe、Co、Ni纳米晶的软模板合成及其表征

报道了在有序介孔碳基体中一步合成负载Fe、Co、Ni纳米晶的方法. 以间二苯酚和甲醛为碳源, F127为模板剂, Fe、Co、Ni的硝酸盐为前驱体, 通过软模板组装路线在酸性条件下合成了负载型有序介孔碳复合材料. 采用X射线衍射(XRD)、透射电镜(TEM)和氮气吸附等手段对所合成材料进行了表征. 结果表明: 合成的材料具有类似于SBA-15的有序介孔结构, 有序介孔碳负载Fe、Co、Ni纳米晶复合材料的比表面积分别为586、626和698 m²·g^-1. XRD和TEM表征结果证实了金属物种以高分散纳米晶的形式分布在介孔碳基体中.     

链霉亲和素-异硫氰酸荧光素偶联核壳型Fe_3O_4/Au纳米晶的合成及性质

采用改进的Polyol合成法,以PEO-PPO-PEO为表面活性剂制备了链霉亲和素-异硫氰酸荧光素偶联的Fe3O4/Au纳米粒子;利用透射电镜和X射线衍射仪分析证实了Fe3O4/Au的核壳型纳米结构,确定了其粒径和分布;采用紫外-可见吸收光谱仪和荧光光谱仪测定了所制备的纳米粒子的光学活性和荧光特性,并采用振动样品磁强计(VSM)测量了其磁化率.结果表明,所制备的Fe3O4/Au纳米粒子具有光学活性和荧光特性,以及优异的磁性.     

Site-preferential design of itinerant ferromagnetic borides: experimental and theoretical investigation of MRh6B3 (M = Fe, Co)

Single-phase polycrystalline samples of the compounds MRh(6)B(3) (M = Fe, Co) as well as single crystals of CoRh(6)B(3) have been synthesized by arc-melting the elements under a purified argon atmosphere in a water-cooled copper crucible. The characterization of the new phases was achieved by using single-crystal and powder X-ray diffraction as well as EDX measurements. The two phases are isotypic and crystallize in the hexagonal Th(7)Fe(3) structure type (space group P6(3)mc, no. 186, Z = 2). In this structure, the magnetically active atoms (Fe, Co) are preferentially found on only one of the three available rhodium sites, and together with rhodium they build a three-dimensional network of interconnected (Rh/M)(3) triangles. Magnetic properties investigations show that both phases order ferromagnetically below Curie temperatures of 240 K (for FeRh(6)B(3)) and 150 K (for CoRh(6)B(3)). First-principles DFT calculations correctly reproduce not only the lattice parameters but also the ground state magnetic ordering in the two phases. These calculations also show that the long-range magnetic ordering in both phases occurs via indirect ferromagnetic coupling between the iron atoms mediated by rhodium. This magnetic structural model also predicts the saturation magnetizations to be 4.02 μ(B) for FeRh(6)B(3) (3.60 μ(B) found experimentally) and 2.75 μ(B) for CoRh(6)B(3). Furthermore, both phases are predicted to be metallic conductors as expected for these intermetallic borides.     

Heteroatomic deltahedral clusters: synthesis and structures of closo-[Bi3Ni(4)(CO)6]3-, closo-[Bi4Ni4(CO)6]2-, the open cluster [Bi3Ni6(CO)9]3-, and the intermetalloid closo-[Nix@[Bi6Ni6(CO)8)]4-

Reactions of ethylenediamine solutions of K4Bi5 with Ni(PPh3)2(CO)2 yielded four novel hetero-atomic Bi/Ni deltahedral clusters. Three of them, the 7-atom pentagonal bipyramidal [Bi3Ni4(CO)6]3-, the 8-atom dodecahedral [Bi4Ni4(CO)6]2-, and the Ni-centered or empty 12-atom icosahedral [Nix@[Bi6Ni6(CO)8]4-, are closo-species according to both electron count and shape. The centered icosahedral cluster resembles packing in intermetallic compounds and belongs to the emerging class of intermetalloid clusters. The shape of the fourth cluster, [Bi3Ni6(CO)9]3-, can be derived from the icosahedral Ni-centered [Ni@[Bi6Ni6(CO)8]4- by removal of three Bi- and one Ni-atoms of two neighboring triangular faces. The clusters were structurally characterized by single-crystal X-ray diffraction in compounds with potassium cations sequestered by 2,2,2-crypt or 18-crown-6 ether. They were also characterized in solution by electrospray mass spectrometry.     

Au/FeOx催化3-硝基苯乙烯加氢反应

采用沉积-沉降法制备了负载型Au/γ-Fe2O3、Au/α-Fe2O3和Au/Fe3-O4催化剂,并利用X射线粉末衍射技术对催化剂进行了表征。 在不同反应介质（水、乙醇和无溶剂）中,研究了Au/FeOx催化剂催化3-硝基苯乙烯加氢反应,考察了反应温度以及载体对催化剂活性的影响。 实验结果表明,在介质水中3-硝基苯乙烯的转化率要远高于乙醇中或无溶剂条件下的转化率,且随温度的升高而增大,而其加氢产物3-氨基苯乙烯的选择性无显著变化。 不同氧化铁载体负载的Au催化剂在水中的活性顺序为Au/γ-Fe2O3＞Au/α-Fe2O3＞Au/Fe3O4,其活性的差异被认为来自于不同氧化铁载体与Au之间的相互作用。     

Fe3O4/Polypyrrole/Au nanocomposites with core/shell/shell structure: synthesis, characterization, and their electrochemical properties

Uniform Fe3O4 nanospheres with a diameter of 100 nm were rapidly prepared using a microwave solvothermal method. Then Fe304/polypyrrole (PPy) composite nanospheres with well-defined core/shell structures were obtained through chemical oxidative polymerization of pyrrole in the presence of Fe3O4; the average thickness of the coating shell was about 25 nm. Furthermore, by means of electrostatic interactions, plentiful gold nanoparticles with a diameter of 15 nm were assembled on the surface of Fe3O4/PPy to get Fe3O4/PPy/Au core/shell/shell structure. The morphology, structure, and composition of the products were characterized by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The resultant nanocomposites not only have the magnetism of Fe3O4 nanoparticles that make the nanocomposites easily controlled by an external magnetic field but also have the good conductivity and excellent electrochemical and catalytic properties of PPy and Au nanoparticles. Furthermore, the nanocomposites showed excellent electrocatalytic activities to biospecies such as ascorbic acid (AA).     

Electronic and Geometric Structure of Bimetallic Clusters: Density Functional Calculations on [M(4){Fe(CO)(4)}(4)](4-) (M = Cu, Ag, Au) and [Ag(13){Fe(CO)(4)}(8)](n)(-) (n = 0-5)

The results of all-electron density functional calculations on the bimetallic cluster compounds [M(4){Fe(CO)(4)}(4)](4-) (M = Cu, Ag, Au) and on the corresponding naked species M(4)Fe(4) are reported. The trends within the triad have been investigated. The bare metal clusters exhibit a strong magnetization which is quenched on addition of CO ligands. The bonding in the bare clusters is different for the silver derivative compared to that of copper and gold, resulting in comparatively weaker Ag-Fe and Ag-Ag bonds. This can be rationalized in terms of the different d-sp mixing, which for Cu and Au is larger than for Ag. Relativistic effects act to increase the 4d-5s mixing in Ag and to strengthen the intermetallic bond with Fe. In the carbonylated clusters a charge transfer from the metal M (M = Cu, Ag, or Au) to the Fe(CO)(4) groups occurs so that the atoms M can be considered in a formal +I oxidation state, rationalizing the nearly square-planar geometry of the metal frame. In fact, the local coordination of the M atoms is almost linear, as expected for complexes of M(I). The addition of extra electrons results in a stabilization of the clusters, indicating the electron-deficient nature of these compounds. Similar features have been found for the largest cluster synthesized so far for this class of compounds, [Ag(13){Fe(CO)(4)}(8)](n)(-), (n = 0-5). The nature and localization of the unpaired electron in the tetraanion is also discussed.     

Molecule-based magnets formed by bimetallic three-dimensional oxalate networks and chiral tris(bipyridyl) complex cations. The series [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion)

The synthesis, structure, and physical properties of the series of molecular magnets formulated as [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion) are presented. All the compounds are isostructural to the [Ru(bpy)3][ClO4][MnCr(ox)3] member whose structure (cubic space group P4(1)32 with a = 15.506(2) A, Z = 4) consists of a three-dimensional bimetallic network formed by alternating MII and CrIII ions connected by oxalate anions. The identical chirality (lambda in the solved crystal) of all the metallic centers determines the 3D chiral structure adopted by these compounds. The anionic 3D sublattice leaves some holes where the chiral [Z(bpy)3]2+ and ClO4- counterions are located. These compounds behave as soft ferromagnets with ordering temperatures up to 6.6 K and coercive fields up to 8 mT.     

镍钴锌纳米铁氧体的制备及磁热性能

以乙酰丙酮盐为前驱体,三乙二醇为溶剂,采用多元醇法制备了纳米Ni0.5-xCoxZn0.5Fe2O4(x=0,0.1,0.2,0.3和0.4)铁氧体.通过X射线衍射仪(XRD)、透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FTIR)和振动样品磁强计(VSM)等对样品的结构、形貌和磁性能进行了表征.结果表明,所得纳米Ni0.5-xCoxZn0.5Fe2O4铁氧体的分散性较好,尺寸均一.在室温下产物的剩磁和矫顽力均较小,表现出亚铁磁性.纳米Ni0.3Co0.2Zn0.5Fe2O4铁氧体的饱和磁化强度达到41.34 A·m2·kg-1,其在交变磁场中升温可达到55℃,表现出较好的磁热性能.     

Formation of a tetragonal Cu3Au alloy at gold/copper interfaces

A gold–copper alloy with a nominal composition of Cu₃Au but with a tetragonal (c = 4a) structure is observed to form at Au/Cu interfaces of gold/copper multilayers deposited on amorphous substrates by d.c. magnetron sputtering. The formation of this non‐equilibrium structure (tentatively D0₂₃) under‐ambient conditions is detected by secondary ion mass spectrometry, x‐ray diffraction and high‐resolution cross‐sectional transmission electron microscopy. Co‐sputtering of Au and Cu under similar conditions produces only conventional fcc Cu₃Au alloy phases, suggesting that interfacial confinement plays a significant role in producing the novel Cu₃Au alloy phase in gold/copper multilayers. Copyright © 2003 John Wiley & Sons, Ltd.