Ti-47Al-1.2Ce合金显微组织及稀土相

ＴｉＡ1金属间化合物以其低密度 ,高比强度和比弹性模量 ,良好的抗蠕变及抗氧化能力等特点 ,已成为航天、航空、能源及汽车工业极具竞争力的高温结构材料。虽然ＴｉＡｌ基合金有众多优点 ,但仍存在室温塑性较低、成形性差、性能不平衡等问题 ,还需要深入研究ＴｉＡｌ基合金的合金化及制备工艺等方面技术 ,以此来控制并改善合金的显微组织 ,提高ＴｉＡｌ基合金的综合性能[1～ 4 ] 。合金化是改善ＴｉＡｌ基合金显微组织和性能的重要途径之一 ,通常添加的合金元素有Ｖ ,Ｃｒ ,Ｎｂ ,Ｗ ,Ｍｏ ,Ｓｉ ,Ｂ等[5～ 7] 。稀土元素一般被用来细化材料…     

Additive telluromolybdates. Structure and catalysis in oxidation

Additive telluromolybdates, MoO₃·2TeO₂ and M^IIO·TeO₂·MoO₃ (M^IITeMoO₆; M^II = Co, Mn, Zn), converted ethyl lactate selectively to pyruvate in a vaporphase fixedbed flow system at 250–300 °C. A synergy in activity was observed for binary TeO₂–MoO₃, and crystalline Te₂MoO₇ was suggested as the active species. The Rietveld analysis of powder XRD patterns of ternary CoTeMoO₆ revealed the layer structure quite different from that of the reference Te₂MoO₇, but tellurium was again located adjacent to molybdenum linked through lattice oxygen.     

钇对金属陶瓷力学性能和组织的影响

研究了添加钇对Ｔｉ（Ｃ，Ｎ）基金属瓷力学性能和组织的影响。结果表明，加入适量的钇能提高Ｔｉ（Ｃ，Ｎ）基金属陶瓷的抗变强度和硬度，其原因是由于钇与杂质硫起反应在化合物，净化了陶瓷相－金属相，陶瓷相－陶瓷相界面提高子界面结合强度     

Surface characterization of macroporous glycidyl methacrylate based copolymers by inverse gas chromatography

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), PGME, with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine, EDA. Inverse gas chromatography at infinite dilution was used for the determination of adsorption properties of PGME, and copolymer modified with ethylene diamine, PGME-en. Thermodynamic parameters of adsorption, dispersive components of the surface free energies, and the acid/base constants for the copolymer samples were calculated. The calculated dispersive surface energy values, , for PGME and PGME-en are comparable with the literature data for nonconductive polymers.     

Catalytic oxidation of CO,hydrocarbons, and ethyl acetate over perovskite-type complex oxides

The catalytic activity of M^IM^IIO₃] perovskite-type complex oxides (M^I = La, Y, Nd, Yb; M^II = Co, Mn, Ni) in the oxidation of CO, propylene, benzene, ethylbenzene,o-xylene, and ethyl acetate was investigated. The Co-containing catalysts were shown to be more active in the oxidation than the Mn-containing catalysts. A relationship between the catalytic and adsorption properties was established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 602–605, April, 1994.     

A density functional study on magnetic exchange interaction between Mn(II) ion and nitronyl nitroxide radical in <Emphasis Type="Italic">trans</Emphasis>-and <Emphasis Type="Italic">cis</Emphasis>-metal-radical complexes

The magneto-structural correlation between a Mn(ll) ion, coordinated in an octahedral environment, and two nitronyl nitroxide radical ligands in trans- and cis-metal-radical complexes is investigated by the broken symmetry (BS) approach within density functional theory (DFT). The dependences of coupling constants J on three structural parameters: (i) bond angle θ (Mn-O-N (nitroxide)); (ii) rotating angle ψ, defined by the nitronyl nitroxide radical plane rotating around the axial Mn-O (nitroxide); (iii) bond distance R (Mn-O (nitroxide)) are directly calculated. Our calculations showed that both trans- and cis-Mn(ll)-radical complexes behave a stronger antiferromagnetic interaction, consistent with experiments. In view of molecular orbital theory, the direct exchanges, including σ-type and π-type exchanges, are responsible for the magnetic exchange pathways. There is a preferable linear correlation between the calculated coupling constants J and the overlap integral squares S b between the local magnetic orbitals at the various rotating angle ψ at the fixed bond angle θ and bond distance R, in both trans- and cis-Mn(ll)-radical complexes.     

共沉淀浸渍法制备由合成气直接合成二甲醚的Cu-Mn催化剂

采用共沉淀浸渍法,制备了直接合成二甲醚的Cu-Mn-Zn催化剂,通过对组成成分及其配比的研究,发现Cu含量一定的条件下,n(Zn)/n(Mn)摩尔比对催化剂性能有较大的影响,当n(Zn)/n(Mn)=1/3～1/2时,催化剂对CO的转化率和对二甲醚的选择性达到最佳,分别为53.6%和63.5%；如锰添加比例过大,对催化剂催化合成二甲醚有微弱抑制；添加锌比例过大,会大大降低CO的转化率。载体Y分子筛的含量对催化剂性能也有影响,用量过大将降低催化剂的活性和对二甲醚的选择性,当其含量为33%时,催化剂上CO转化率和选择性可分别达到66%和68%,且催化剂活性随分子筛含量减少不再有明显的变化。     

用MES及XRD研究FT合成催化剂的活性结构

采用穆斯堡尔谱及Ｘ光衍射法研究了共沉淀法制备的不同Ｆｅ／Ｍｎ比催化剂在焙烧、合成气还原及ＦＴ反应后体系相结构的变化。结果表明：锰助剂的加入使催化本相由铁磁性逐渐转化为超顺磁性，相应使催化剂还原逐渐难，Ｍｎ助剂促进了ＦＴ合成反应进行。反应性能与Ｆｅ／Ｍｎ尖晶石（Ｆｅ１－ｙＭｎｙ）３Ｏ４组成含量及式中ｙ大小密切相关，与ＭｎＣｏ３及ＭｎＯ的存在也有一定关系。富铁催化剂中Ｍｎ主要起电子助剂作用，而富锰催化     

CH bond activation in the presence or absence of oxygen or nitrous oxide

The reaction of C₂H₆with lattice oxygen, O^2- (in the absence of gaseous oxygen), or “adsorbedℍ oxygen (in the presence of gaseous oxygen) over NiMoO₄ catalysts has been performed and compared to C₃H₈ activation. The results obtained indicate that adsorbed oxygen exhibits a higher reactivity to C₂H₆, while lattice oxygen is more reactive relative to C₃H₈. Kinetic studies of these two reactions in presence of molecular oxygen have indeed shown that the ethane oxidative dehydrogenation (ODH) is dependent on the oxygen partial pressure, whilst on the contrary propane ODH is not. In order to confirm the presence of “adsorbed” oxygen for ethane activation, ODH tests have been performed with N₂O. On increasing temperature, the O^- adsorbed species enhances the mild oxidation of ethane. The activation energy of ethane consumption E_C2H6, relative to propane (E_C3H8 = 133 kJ/mol) is 145 kJ/mol. A possible mechanism is proposed for the oxidative dehydrogenation of ethane. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis, structure and physical properties of Ru ferrites: BaMRu5O11 (M=Li and Cu) and BaM′2Ru4O11 (M′=Mn, Fe and Co)

The synthesis, structure, and physical properties of five R-type Ru ferrites with chemical formula BaMRu₅O₁₁ (M=Li and Cu) and BaM′₂Ru₄O₁₁ (M′=Mn, Fe and Co) are reported. All the ferrites crystallize in space group P6₃/mmc and consist of layers of edge sharing octahedra interconnected by pairs of face sharing octahedra and isolated trigonal bipyramids. For M=Li and Cu, the ferrites are paramagnetic metals with the M atoms found on the trigonal bipyramid sites exclusively. For M′=Mn, Fe and Co, the ferrites are soft ferromagnetic metals. For M′=Mn, the Mn atoms are mixed randomly with Ru atoms on different sites. The magnetic structure for BaMn₂Ru₄O₁₁ is reported.