Ti-48Al-2M~1-2M~2(M~1=Nb,V;M~2=Mn,Cr,V)合金电子结构

用紧束缚能带计算方法(EHT)研究了标题多元合金的能带及电子结构。发现少量的多种元素在γ-TiAl中掺杂,对合金中电荷分布的影响,具有单种元素掺杂的叠加性;选择适当的合金元素就能达到多种掺杂的性能互补。多种元素掺杂能更有效地使成键电子云趋势于球形化,Peierls力均称为化,有利于增加γ-TiAl合金的塑性和变形性。     

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…     

TiO2调变对MoO3／γ—Al2O3和CoO—MoO3／γ—Al2O3表面结构及还原 …

采用气相流动吸附法制ＴｉＯ２／γ－Ａｌ２Ｏ３，复合载体，浸渍法担载一定量ＭｏＯ３或ＣｏＯ－ＭｏＯ３，用ＸＲＤ，ＬＲＳ和ＴＰＲ等技术考察了Ｍｏ或Ｃｏ－Ｍｏ催化剂的表面结构和还原性能。结果表明，覆盖在γ－Ａｌ２Ｏ３上的ＴｉＯ２能减弱ＭｏＯ３与γ－Ａｌ２Ｏ３之间的相互作用，明显改善Ｍｏ催化剂的表面结构，促进ＭｏＯ３的还原。     

磷酸三丁酯色层分离—电感耦合等离子体原子发射光谱法测定U3Si2

本法对Ｕ３Ｓｉ中２２个微量杂质元素的测定，进行了较系统的实验研究，取样１００ｍｇ时，Ａｌ、Ｃａ、Ｃｄ、Ｃｒ、Ｃｕ、Ｆｅ、Ｈｆ、Ｉｎ、Ｍｇ、Ｍｎ、Ｍｏ、Ｎｂ、Ｎｉ、Ｐｂ、Ｓｎ、Ｔａ、Ｔｉ、Ｖ、Ｙ、Ｚｎ和Ｚｒ的测定范围５μｇ／ｇ－８００μｇ／ｇ，回收率为９４％－１０５％，ＲＳＤ（ｎ＝８）０．４％－１．２％。     

金属-金属氧化物-载体相互作用研究:混合C4烷烃脱氢

以混合Ｃ４烷烃脱氢反应研究了Ｐｔ（Ｐｄ，Ｒｈ，Ｉｒ）－金属氧化物（Ｓｎ，Ｉｎ，Ｓｂ，Ｔｉ，Ｖ，Ｍｏ，Ｍｎ，Ｆｅ的氧化物）－载体的相互作用发现Ｐｔ－Ｉｎ（Ｓｎ）／γ－Ａｌ２Ｏ３，Ｐｔ－Ｆｅ／ＳｉＯ２脱氢性能较好。并根据可变价金属氧化物的特性，金属氧化物含量存在最佳值及载体的性质对“夹心”结构模型进行了讨论。     

Mn－Ag／γ－Al_2O_3催化剂中氧的性能

本文运用ＴＰＲ、ＴＰＤ－ＭＳ、ＸＲＤ等技术研究了Ｍｎ－Ａｇ／γ－Ａｌ_２Ｏ_３催化剂的还原性能和再氧化能力．结果表明，Ｍｎ－Ａｇ／γ－Ａｌ_２Ｏ_３中银物相由Ａｇ￣０和Ａｇ_２Ｏ组成，锰物相由β－ＭｎＯ_２和Ｍｎ２Ｏ_３组成．Ｍｎ／γ－Ａｌ_２Ｏ_３催化剂的ＴＰＲ有二个还原峰，分别是ＭｎＯ_２和Ｍｎ_２Ｏ_３的还原．Ａｇ促使ＭｎＯ_２和Ｍｎ_２Ｏ_３的还原明显向低温方向移动，而且ＭｎＯ_２和Ｍｎ_２Ｏ_３的还原峰融合成一个还原峰．Ｍｎ－Ａｇ／γ－Ａｌ_２Ｏ_３的ＴＰＤ有三个脱氧峰，随着Ａｇ含量增加，峰Ⅰ向高温方向移动，Ｍｎ￣（４＋）２ｐ３／２的电子结合能增加，并且催化剂的再氧化能力增强．催化剂ＣＯ的氧化活性与催化剂的再氧化能力有很好的对应关系．     

TiO_2调变对MoO_3/γ-Al_2O_3和CoO-MoO_3/γ-Al_2O_3表面结构及还原性能的影响

采用气相流动吸附法制ＴｉＯ２／γ－Ａｌ２Ｏ３，复合载体，浸渍法担载一定量ＭｏＯ３或ＣｏＯ－ＭｏＯ３，用ＸＲＤ，ＬＲＳ和ＴＰＲ等技术考察了Ｍｏ或Ｃｏ－Ｍｏ催化剂的表面结构和还原性能。结果表明，覆盖在γ－Ａｌ２Ｏ３上的ＴｉＯ２能减弱ＭｏＯ３与γ－Ａｌ２Ｏ３之间的相互作用，明显改善Ｍｏ催化剂的表面结构，促进ＭｏＯ３的还原。适量ＣｏＯ助剂的加入能促进ＭｏＯ３在载体表面的分散。     

Co-Mo/TiO2和Co-Mo/γ-Al2O3加氢脱硫催化剂的研究

本文考察了ＣｏＭｏ／ＴｉＯ２和ＣｏＭｏ／γ－Ａｌ２Ｏ３催化剂的加氢脱硫性能及表面结构变化和处理条件对其活性的影响，担体ＴｉＯ２（Ａ）和ＴｉＯ２（Ｂ）分别采用ＴｉＯＳＯ４水解法制备，结果表明，催化剂的活性顺序为ＣｏＭｏ／ＴｉＯ２（Ａ）＞ＣｏＭｏ／ＴｉＯ２（Ｂ）＞ＣｏＭｏ／γ－Ａｌ２Ｏ３，催化剂的预处理条件对催化剂的加氢脱硫和加氢活性有很大影响，ＴｉＯ２担体上Ｍｏ物种主要以八面体配位构型存在，Ｍｏ＾－     

Cu－Ag－Mn－Ce－O／γ－Al_2O_3催化剂对CH_3OH及CO深度氧化时各元素的相互作用

Ｃｕ－Ａｇ－Ｍｎ－Ｃｅ－Ｏ／γ－Ａｌ_２Ｏ_３催化剂对ＣＨ_３ＯＨ及ＣＯ深度氧化时各元素的相互作用王金安，许勇，汪仁（华东理工大学工业催化研究所，上海２００２３７）关键词Ｃｕ－Ａｇ－Ｍｎ－Ｃｅ－Ｏ／γ－Ａｌ_２Ｏ_３催化剂，深度氧化，甲醇，一氧化碳，相互?..     

钇对陶瓷刀具材料Al2O3/TiCN的强韧化效应

在已 研制的含烯土Ａｌ２Ｏ３／ＴｉＣＮ陶瓷刀具材料的基础上，采用ＳＥＭ，ＴＥＭ和能谱分析等方法探讨了Ｙ的强韧化效应。稀土增强Ａｌ２Ｏ３／ＴｉＣＮ陶瓷刀具材料力学性能改善的原因在于，Ｙ的添加能在一定程度上积聚杂质，Ｗ，Ｆｅ和Ｃｒ等，从而起到清洁界面、提高界面结合强度的作用。     

Electronic Structure of TiAl-2M(M=V,Nb,Ta,Cr,Mo,W,Mn) Alloy

1INTRODUCTIONTitaniumaluminidesbasedonY-TiAlarereceivingconsiderableattentionaspo-tentialcandidatesformaterialsinhightemperatureaerospaceapplication.Theirlowdensity,hightemperaturescreepresistance,highoxidationresistanceandstrengthmakesthemexcellentpotentialenginematerials.Howevertheirlowductilityandlowfracturetoughnessatroom'temperaturesaremajorhindrancestotheirpracticaluti-lization.TheTiAlalloymayhaveanelongationabout2%t'},furtherimprovementisnecessarybeforethesematerialscouldbeusedin…     

Electronic and magnetic properties of all 3d transition‐metal‐doped ZnO monolayers

Stable geometries, electronic structures, and magnetic properties of the ZnO monolayer doped with 3d transition‐metal (TM) (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) atoms substituting the cation Zn have been investigated using first‐principles pseudopotential plane wave method within density functional theory (DFT). It is found that these nine atomic species can be effectively doped in the ZnO monolayer with formation energies ranging from ?6.319 to ?0.132 eV. Furthermore, electronic structures and magnetic properties of ZnO monolayer can be modified by such doping. The results show that the doping of Cr, Mn, Fe, Co, Ni, and Cu atoms can induce magnetization, while no magnetism is observed when Sc, Ti, and V atoms are doped into the ZnO monolayer. The magnetic moment is mainly due to the strong p–d mixing of O and TM (Cr, Mn, Fe, Co, Ni, and Cu) orbitals. These results are potentially useful for spintronic applications and the development of magnetic nanostructures. © 2013 Wiley Periodicals, Inc.     

Inverted-sandwich-type and open-lantern-type dinuclear transition metal complexes: theoretical study of chemical bonds by electronic stress tensor

We study the electronic structure of two types of transition metal complexes, the inverted-sandwich-type and open-lantern-type, by the electronic stress tensor. In particular, the bond order $b_\varepsilon$ measured by the energy density which is defined from the electronic stress tensor is studied and compared with the conventional MO-based bond order. We also examine the patterns found in the largest eigenvalue of the stress tensor and corresponding eigenvector field, the ??spindle structure?? and ??pseudo-spindle structure??. As for the inverted-sandwich-type complex, our bond order $b_\varepsilon$ calculation shows that relative strength of the metal-benzene bond among V, Cr, and Mn complexes is V?>?Cr?>?Mn, which is consistent with the MO-based bond order. As for the open-lantern-type complex, we find that our energy density-based bond order can properly describe the relative strength of Cr?CCr and Mo?CMo bonds by the surface integration of the energy density over the ??Lagrange surface?? which can take into account the spatial extent of the orbitals.     

Nb元素影响TiAl金属间化合物键合特征的第一原理计算

采用第一原理方法, 研究了Nb元素对TiAl金属间化合物电子结构及其对Ti, Al和O原子键合作用的影响. 研究结果表明, Nb元素对富Ti和富Al的TiAl金属间化合物体系电子结构及键合作用的影响不同. 对于富Ti的TiAl金属间化合物体系, Nb原子取代Ti晶格位置后, 减小了Ti费米能级处的电子密度, 削弱了Ti原子与O原子间的相互作用; 同时增强了Al原子中s电子和O原子中p电子的相互作用. 而Nb原子对富Al的TiAl金属间化合物体系中Ti/Al与O的相互作用影响较小. 同时, 向TiAl金属间化合物中掺杂Nb元素, 增大了TiO2的生成能垒, 减小了Al2O3的生成能垒, 有利于促进抗氧化膜Al2O3的生成. 因此, 添加合金化元素Nb有利于提高TiAl金属间化合物的抗氧化性能, 这与实验报道相一致.     

Reactions of first-row transition metal ions with propargyl alcohol in the gas phase

The gas-phase reactions with propargyl alcohol (PPA) of all the singly charged ions of the first-row transition metals, generated by laser ablation in an external ion source, were studied by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS.). The reactivities of the metal ions change irregularly across the periodic table, and the reactivity of each ion is a function of its electronic configuration and corresponding metal-oxygen (M-O) bond energies. The 10 metal ions were classified into three categories according to their reactivities: Sc(+), Ti(+) and V(+) are the most reactive ions which react with PPA to give many kinds of oxygen-rich products due to stronger M-O bonds; Fe(+), Co(+) and Ni(+) are less reactive; Cr(+), Mn(+), Cu(+) and Zn(+) are the most unreactive ions, due to the half and completely occupied valence electronic configurations. The order of reactivity is Ti(+) > V(+) > Sc(+) > Co(+) > Fe(+) approximately Ni(+) > Zn(+) > Cr(+) approximately Mn(+) approximately Cu(+).     

The site preference and doping effect on mechanical properties of Ni3Al-based γ′ phase in superalloys by combing first-principles calculations and thermodynamic model

The fundamental aspects of site preference of alloying elements on sublattice of the strengthen γ′ phase with L1₂ structure have not been well understood, which hinders the optimized design of advanced Ni-based high-temperature alloys. In this contribution, the temperature- and composition-dependent site occupying preferences of the binary, ternary, and quaternary of Ni₃Al-based γ′ phase alloyed with M_i where M_i represents the additional transitional metals Co, Cr, Cu, Fe, Mn, Mo, Re, Ta, Ti, V, or W atoms (arranged in alphabetical order) chosen frequently, were studied using a two-sublattice thermodynamic model (Ni, Al, M_i)_1a(Ni, Al, M_i)_3c. The site occupying fractions (SOFs) were calculated based on a thermodynamic database established in this work, where the thermodynamic data of the end-members involved were obtained using first-principles calculations and phonon spectrum calculations. The calculated SOFs results show that there is an obvious site preference for stoichiometry binary Ni₃Al, and its site configuration changes from (Al)_1a(Ni)_3c at room temperature to (Al_0.9984Ni_0.0015)_1a (Al₀Ni_0.9994)_3c at 1273 K. For the γ′ phase with the composition 78Ni-26Al-4M_i (atom ratio and x_Ni/x_Al = 3:1), Mo atoms always preferred to occupy the 1a sublattice (Al site), Co, Mn, and Ti atoms always prefer the 3c sublattice (Ni site) in the whole temperature range, while the site preference of Cr, Cu, Fe, Re, Ta, V, or W atom is affected by temperature. For example, when the heat treatment temperature is lower than 700 K, Cr, Cu, Fe, Ta, V, and W atoms occupy the 1a and 3c sublattice randomly, and Re atoms prefer to 3c sublattice, while when the heat treatment temperature is higher than 1273 K, Cr, Cu, and W atoms prefer 3c sublattice, Fe and Ta atoms prefer to 1a sublattice, while all Re atoms occupy the 3c sublattice exclusively, and all V atoms occupy the 1a sublattice exclusively, respectively. Likewise, the site preference of the quaternary system with selective compositions 78Ni-26Al-2 M₁-2 M₂ was also predicted. Based on calculated SOFs results, the mechanical and thermodynamic properties were studied at the ground state. It has been revealed that Cr, Re, and V doping can improve the microhardness of Ni₃Al alloys; in particular, the effect of Cr is extraordinary; and all elements, except Mn, Mo, and Ti, would enhance the bulk modulus of Ni₃Al-based γ′ phase, in which Mn have the greatest influence on reducing the bulk and shear modulus, respectively. Furthermore, all the B/G ratios of the computed Ni₃Al-based γ′ phase are >1.75, showing inherent ductility. Only Cr doping significantly enhances the Debye temperature of the Ni₃Al-based γ′ phase.     

Energetics and structure of single Ti defects and their influence on the decomposition of NaAlH(4)

The energetics and structure of various types of single extrinsic Ti defects in NaAlH(4) bulk and (001) slab at the hydriding/dehydriding critical point environment were studied systematically. It is found that the most favorable situation is Ti substituting Al at the subsurface (Ti(Al)(2nd)), which has the highest coordination number for extrinsic Ti ions. The most stable Ti defect in the 1st layer is located at the Al rich interstitial site, namely Ti(i)(1st), accompanied with remarkable strength of Ti-H/Al bond and local geometry deformation at the 1st layer around Ti. Deeper insight of the formation mechanism of Ti defects is obtained by dividing the formation enthalpy of Ti defects into three terms, which are contributed from the cost of removing a substituted host atom if necessary, the cost of structure deformation, and the gain of bonding between Ti and its surrounding ions in the formation of the defects. This associates the formation energy directly with the local structure of Ti defects. For the first time, we adopt H(f)(H), H(f)(H-H), H(f)(AlH(3)) and H(f)(Na) to discuss the hydrogen release ability of the Ti doped NaAlH(4). We find that TiAl(4)H(20) and TiAl(3)H(12) complexes are formed around Ti(Al)(2nd) and Ti(i)(1st) respectively, which significantly promotes the dehydriding ability of NaAlH(4). What is more, the catalyst mechanism of Ti on the decomposition of NaAlH(4) is linked to the AlH(3) mechanism according to our calculations.     

Al、Co和Mn掺杂对LiNiO2结构的影响

本文采用XRD和EXAFS研究Al、Co和Mn原子掺杂对LiNiO₂材料结构的影响。XRD结果表明掺杂材料具有与LiNiO₂相同的晶体结构，都属于R3m点群，但是晶胞略微缩小，LiNiO₂的层状结构得到改善,阳离子有序度增强。从EXAFS数据拟合结果可以看出，引入掺杂原子Al、Co和Mn减弱了Jahn-Teller畸变，使得NiO₆八面对称性提高。掺杂Al和Co使得第一壳层Ni-O配位键长减小，掺杂Mn原子影响不明显。Al、Co和Mn掺杂使第二壳层Ni-Ni配位键长减小，Co和Mn掺杂使得第二壳层局域有序度提高，而Al的引入使得第二壳层局域有序度降低。     

Calculated and experimental geometries and infrared spectra of metal tris-acetylacetonates: vibrational spectroscopy as a probe of molecular structure for ionic complexes. Part II

Following on from our previous work on Sc, Fe, Cr, and Al (Part I; see J. Phys. Chem. A, 105 (2001) 238), the geometries and infrared spectra of the trivalent metal tris-acetylacetonate complexes (M[O2C5H7]3; M = Ti, V, Mn, Co) have been studied both experimentally and theoretically using nonlocal hybrid density functional theory with a split-valence plus polarization basis for the ligand and valence triple-zeta for the metal. Unlike the D3 complexes studied in Part I, those of Ti, V and Mn are candidates for Jahn-Teller distortion due to fractional d-shell occupancy. Using scale factors transferred from Part I, our calculated frequencies are in very good agreement with experimentally observed fundamentals. Our investigation shows that the V and Mn complexes distort to C2 ground states, but D3 Ti tris-acetylacetonate is stable. Further investigation of the weak band observed around 800 cm(-1) in the Fe complex (and present in almost all studied first-row transition metal tris-acetylacetonates), which we were unable to assign theoretically in Part I, supports the argument that this band is not a fundamental but is due to Fermi resonance.