对氯硝基苯在含镧的镍钼硼奈米触媒上的氢化反应

钼和镧是好的镍硼触媒的促进剂, 对于对氯硝基苯氢化反应有好的效果, 因此同时加入钼和镧在镍硼触媒上应该是有趣的研究题目. 本研究利用化学还原法制备了一系列含有不同量镧的镧钼镍触媒, 醋酸镍、钼酸胺及硝酸镧同时加入含有甲醇的水溶液中. 以X光绕射, 穿透式电子显微镜、高分辨率电子显微镜及X光光电能谱仪鉴定了这些触媒. 对氯硝基苯氢化反应是在批次反应器中于333 K、1.2 MPa氢气压力及500 r/min转速下操作. 即使在镍钼硼中加入很少量的镧, 对提高活性及对氯苯胺的选择性都有显著的效果, 加入适量的镧可以抑制镍钼硼的长范围的结晶排列, 并保持镍钼硼在非结晶状态. 镧以氧化态存在, 其功效为阻隔物, 避免镍钼硼聚集, 但是过量的镧会有相反的效果, 镧和镍的适当比例是0.2.     

Nickel-iron borate coated nickel-iron boride hybrid for highly stable and active oxygen evolution electrocatalysis

The development of efficient and cost-effective electrocatalysts toward anodic oxygen evolution reaction (OER) is crucial for the commercial application of electrochemical water splitting. As the most promising electrocatalysts, the OER performances of nickel-iron-based materials can be further improved by introducing metalloid elements to modify their electron structures. Herein, we developed an efficient hybrid electrocatalyst with nickel-iron boride (NiFeB) as core and amorphous nickel-iron borate (NiFeB_i) as shell (NiFeB@NiFeB_i) via a simple aqueous reduction. The obtained NiFeB@NiFeB_i exhibits a small overpotential of 237 mV at 10 mA/cm² and Tafel slope of 57.65 mV/dec in 1.0 mol/L KOH, outperforming most of the documented precious-metal-free based electrocatalysts. Benefiting from the in situ formed amorphous NiFeBi layer, it shows excellent stability toward the oxygen evolution reaction (OER). These findings might provide a new way to design advanced precious-metal-free electrocatalysts for OER and the application of electrochemical water splitting.     

无电沉积硼化镍材料对水氧化的电催化性能

通过无电沉积/化学镀的方法分别制得石墨烯(Graphene)、 镍网(Ni foam, NF)、 钛网(Ti mesh, TM)、 碳布(Carbon cloth, CC)负载的硼化镍材料. 其中在石墨烯基底上生长的硼化镍层由规则的纳米颗粒构成, 且均匀致密. 对几种材料在碱性条件下(1.0 mol/L KOH电解质中)的水氧化电催化性能进行了研究, 结果表明, 石墨烯基底上生长的硼化镍材料(NiB_x/graphene)具有最佳的水氧化电催化性能. 电流密度达到10 mA/cm²时的过电位仅为277 mV, 相应的Tafel斜率为57 mV/dec. 对石墨烯负载的硼化镍材料进行烧结, 测得过电位为330 mV, 与未烧结的样品相比电催化活性下降. 该方法所制的石墨烯负载的硼化镍材料兼具高电催化活性和稳定性, 为低成本、 高效率的水氧化非贵金属电催化剂的制备提供了新思路.     

Characteristics of sputtered TaBx thin films as diffusion barriers between copper and silicon

Thin films of TaB_x interposed between Cu and Si are examined here as diffusion barriers for Cu metallization. In order to investigate the performance of Cu/TaB_x/Si contact systems, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), sheet resistance measurement, scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM), and Auger electron spectroscopy (AES) depth profile were used. Results of this study indicate that the barrier characteristics are significantly affected by the B/Ta ratio. In addition, the failure mechanism for the Cu/TaB_x/Si contact systems is also discussed herein.     

超导体YB6和LaB6的电子结构研究

本文使用准确的第一原理方法，对超导体YB6和LaB6进行了电子结构比较研究，为进一步的实验研究提供理论参考．     

Nucleation and growth of α-Ti on TiB precipitates in Ti–15Mo–2.6Nb–3Al–0.2Si–0.12B

The microstructure was investigated of a β-stabilized Ti–15Mo–2.6Nb–3Al–0.2Si–0.12B alloy at two different aging temperatures, 540°C/8?h and 660°C/8?h. In particular, the heterogeneous nucleation of α-Ti from TiB particles was studied at these aging temperatures. At the lower aging temperature, α-Ti precipitated as needle-like shapes on the TiB phase. In contrast, the higher aged sample exhibited globular α-Ti morphology around the TiB phase. This difference was rationalized in terms of the coarsening behavior of α-Ti around the TiB phase. Various orientation relationships were observed between these two samples. This difference is because of the precipitation of α-Ti on two different TiB planes. In addition, atom probe analysis confirmed the segregation of alpha and beta stabilizing elements to the respective phases. At the lower aging temperature, it was noted that silicon enriched the α-Ti/β-Ti interface when the α-Ti/β-Ti/TiB were all in contact. Upon α-Ti coarsening, silicon enrichment was observed at the α-Ti/TiB interface at the higher aging temperature.     

LiBC — ein vollständig interkalierter Heterographit

LiBC — A Completely Intercalated Heterographite LiBC is a new compound composed only from light main group elements. LiBC is synthesized from the elements in sealed niobium ampoules at 770 K, and short annealing at 1 770 K, forming hexagonal platelets with golden lustre. According to Li⁺(BC)^?, boron and carbon form planar hetero graphite layers of the isoelectronic hexagonal boron nitride type. The inter-layer regions are completely filled by lithium (P6₃/mmc; a = 275.2 pm; c = 705.8 pm; hP6; ZrBeSi type). The deformation density of the valence electrons prove the π character of the B? C bonds, as well as a polarization according to (BC^?). Chemical and physical properties indicate a certain range of homogeneity x(Li) ≤ 1. The thermal decomposition and chemical reactions lead to BC products not yet characterized. The oxidation of LiBC obviously runs by a mechanism similar to that of graphite.     

Development of very high strength Mo2NiB2 complex boride base hard alloy

A previous investigation revealed that additions of Cr and V to the Mo₂NiB₂ complex boride base hard alloy changed the boride phase crystal structure from orthorhombic to tetragonal and resulted in a remarkable improvement of mechanical properties associated with microstructural refinement. Moreover, an addition of Mn turned out to be effective in further improvement of the mechanical properties in the V-containing alloy. In this investigation, Ni-5B-xMo-12.5V-2.5Mn (mass%) model alloys with four levels of Mo contents corresponding to Mo/B atomic ratio ranging from 1.0 to 1.3 were prepared to study the effect of the Mo/B atomic ratio on the mechanical properties and microstructure. The results indicated that transverses rupture strength (TRS) increased with increasing Mo/B atomic ratio and showed a maximum value of 3.2 GPa at Mo/B=1.2 and then decreased with increasing atomic ratio. Hardness increased linearly from 86.8 HRA to 90.8 HRA with increasing Mo/B atomic ratio.     

熔盐电解合成希土六硼化物的研究——REBO_3、LiBO_2和LiF体系熔盐电解合成RER_6

本文在800℃和空气中电解REBO_3-LiBO_2-LiF(?)盐体系合成了单相的REB_6.石墨川埚兼作容器和阳极.耐火金属棒如Cu和Mo等被悬吊在电解质中作为阴极.根据似二元体系LiBO_2-LiF和LiBO_2-LaBO_3的低熔点组成以La_2O_3、B_2O_3、Li_2CO_3和LiF为原料找到了具有较低熔点的熔盐体系.根据X射线粉末衍射,该熔体是由REBO_3、LiBO_2和LiF三个物相组成.     

Crystal chemistry and physical properties of the ternary compounds R10B9C12 (R = La, Ce, Pr, Nd)

The ternary rare earth boride carbides R₁₀B₉C₁₂ (R = La, Ce, Pr, Nd) were synthesized by reacting the elements at temperatures between 1470 and 1760 K. The crystal structures (Ce₁₀B₉C₁₂ type) were determined from single crystal X-ray diffraction data. For Pr₁₀B₉C₁₂ we found: space group P4₁2₁2, Z = 4, a = 8.4365(3) Å, c = 25.468(1) Å (R1 = 0.023 (wR2 = 0.044) from 2315 reflections with I_o > 2σ(I_o)); for Nd₁₀B₉C₁₂, a = 8.3834(3) Å, c = 25.352(1) Å (R1 = 0.021 (wR2 = 0.044) from 1847 reflections with I_o > 2σ(I_o)). The three-dimensional network of rare earth atoms resulting from a stacking of slightly corrugated square nets has its voids filled with B₄C₄ and B₅C₈ finite chains. The lattice parameters of the isostructural compounds, formed with La and Ce, were refined from powder X-ray diffraction data. Magnetic properties are reported for all compounds. La₁₀B₉C₁₂ is a temperature independent paramagnet down to 6 K. The remaining compounds show a tendency of ferromagnetic ordering at T < 10 K at elevated external fields (induced ferromagnets). The electrical resistivity for Ce₁₀B₉C₁₂ reveals a weak metal-like temperature dependence below room temperature. From heat capacity measurements it can be concluded that the magnetic order is rather a short range type ordering and field induced in the case of Ce₁₀B₉C₁₂ and Pr₁₀B₉C₁₂.