硼烯和碱土金属硼化物二维纳米材料的制备、结构、物性及应用研究

随着石墨烯研究的兴起,二维纳米材料得以迅速发展.在众多的二维纳米材料中,硼烯和碱土金属硼化物二维材料由于具有高费米速度、高杨氏模量、高透光性、高延展性、高度的各向异性、大的泊松比和高的化学稳定性等独特的性质,成为研究人员关注的焦点.本文侧重介绍目前硼烯和碱土金属硼化物二维纳米材料的制备工艺、结构、物性和应用情况.首先总结了目前硼烯的主要结构构型和制备及掺杂工艺;其次介绍了碱土金属硼化物二维纳米材料的理论结构构型和可能的制备路线;最后对硼烯和二维碱土金属硼化物纳米材料的物理特性进行归纳总结,同时预测它们未来最可能实现应用的领域.     

Quantitative Depth Profiling Using Online-Laser Ablation of Solid Samples in Liquid (LASIL) to Investigate the Oxidation Behavior of Transition Metal Borides

The increased demand for sustainability requires, among others, the development of new materials with enhanced corrosion resistance. Transition metal diborides are exceptional candidates, as they exhibit fascinating mechanical and thermal properties. However, at elevated temperatures and oxidizing atmospheres, their use is limited due to the fact of their inadequate oxidation resistance. Recently, it was found that chromium diboride doped with silicon can overcome this limitation. Further improvement of this protective coating requires detailed knowledge regarding the composition of the forming oxide layer and the change in the composition of the remaining thin film. In this work, an analytical method for the quantitative measurement of depth profiles without using matrix-matched reference materials was developed. Using this approach, based on the recently introduced online-LASIL technique, it was possible to achieve a depth resolution of 240 nm. A further decrease in the ablation rate is possible but demands a more sensitive detection of silicon. Two chromium diboride samples with different Si contents suffering an oxidation treatment were used to demonstrate the capabilities of this technique. The concentration profiles resembled the pathway of the formed oxidation layers as monitored with transmission electron microscopy. The stoichiometry of the oxidation layers differed strongly between the samples, suggesting different processes were taking place. The validity of the LASIL results was cross-checked with several other analytical techniques.     

类MgB2硼化物晶体电子结构比较研究

应用准确的第一原理方法，对8种类MgB₂超导体结构的二硼化物进行了电子结构 比较研究，发现其中的超导体具有特殊的能带属性.对其在高压下态密度的变化情况做了对照. 关键词： 硼化物 态密度 能带 高压     

Microwave-assisted synthesis of 4-quinolylhydrazines followed by nickel boride reduction: a convenient approach to 4-aminoquinolines and derivatives

Nickel(II) chloride/sodium borohydride combination was employed for the reduction of 4-hydrazinoquinoline derivatives to the corresponding anilines. This reductive protocol was efficiently applied for the reductive cleavage of monosubstituted hydrazines. We described herein the microwave-assisted synthesis of 4-hydrazinoquinolines, which furnished a high yielding and rapid two-step procedure for the synthesis, under mild conditions, of 4-aminoquinolines as antimalarial precursors.     

Ligand-stabilized Nickel and Palladium Boride Colloids

A route to the first ligand stabilized nickel and palladium boride colloids with core diameters of 1.4 and 1.6 nm is described. The particles are formed by reaction of the metal complexes Cl₂M(PR₃)₂ (M = Ni, Pd, PR₃ = PPr₃, PBu₃) with B₂H₆ in toluene at room temperature with 40–70% yield. The characterization of the pyrophoric brown powders occurred by elementary analyses, resulting in smallest formula units, which then could be extended to averaged molecular formulas by mass determinations, using an analytical ultracentrifuge: [Ni₆B₁₀Cl_1.5(PPr₃)]_12.5 ( 1 ), [Ni₆B₁₀Cl_1.5(PBu₃)]_8.5 ( 2 ), [Pd₄B₆Cl(PPr₃)]_16.5 ( 3 ), and [Pd₄B₆Cl(PBu₃)]_16.5 ( 4 ). From the masses of the colloid cores and their roughly calculated densities the size of the boride particles could be estimated. The diameters of 1.6 nm for 1, 3 , and 4 are identical within the experimental error. Only 2 seems to have a slightly reduced diameter of 1.4 nm. 1–4 can be dispersed in inert organic solvents in any concentration. To confirm these relatively uncertain values high resolution transmission electron microscopy has been used. Investigations of 1 and 3 show indeed an averaged particle size of 1.6 ± 0.3 nm in agreement with the data derived from the mass determinations. Surprisingly most of the observed particles appear to have amorphous structure. This finding is supported by X-ray powder diffraction experiments, as no significant reflex data could be registered. ³¹P and ¹¹B NMR measurements have been performed too, however, do not contribute to further characterization.     

A generic approach for the catalytic reduction of nitriles

The scope of nickel boride mediated reduction of nitriles has been extended further to allow the preparation of Boc protected amines via a mild catalytic process. It is noteworthy that the toxicity of this procedure is greatly reduced due to its catalytic nature in nickel(II) chloride used in combination with excess sodium borohydride. The protocol is marked by its resilience towards air and moisture and hence an easy and general practical protocol.     

Synthesis,Characterization, and Crystal Structure of Na3B20, determined and refined from X‐ray and Neutron Powder Data

At 1050 ?C boron combines with sodium forming a boride of formerly unknown composition and crystal structure. The investigation of the homogeneous, monophasic, and crystalline powder was performed using X‐ray (23 ?C) and neutron (–271.5 ?C) diffraction methods. The structure solution led to an unusual arrangement of boron atoms, characterized by two different types of polyhedra, a distorted pentagonal bipyramid and a distorted octahedron. The Rietveld refinement of the crystal structure was carried out in the orthorhombic space group Cmmm (X‐ray: a = 18.6945(6) Å, b = 5.7009(2) Å, c = 4.1506(1) Å, V = 442.35(1) ų, Z = 2; R_wp = 0.087, R_p = 0.067).     

Darstellung,Kristallstruktur und magnetische Eigenschaften von In2Ni21B6

Preparation, Crystal Structure, and Magnetic Properties of In₂Ni₂₁B₆ In₂Ni₂₁B₆ was prepared by solid state reaction of the elements at 1223 K. The single‐crystals, obtained for the first time, exhibit metallic luster and crystallize in space group Fm 3 m (a = 1059.11(2) pm; Z = 4; 128 symmetry independent reflections; R1 = 0.027; wR2 = 0.125). In₂Ni₂₁B₆ is related to the Cr₂₃C₆‐structure and belongs to the structural family of τ‐borides. The compound melts at 1426 K. Polycrystalline samples of In₂Ni₂₁B₆ are ferromagnetic with a Curie‐Temperature of T_C = 596 K and show metallic conductivity in the range from 12 K to 320 K.     

Intergrowth Phases of Tetragonal Rare Earth Boride Carbides

Tetragonal rare earth boride carbides with structure types derived from La₅B₂C₆ and Sc₃C₄, respectively, can intergrow coherently. Slabs of both types with various thicknesses from one unit‐cell parameter up to macroscopic domains may grow together, sharing a common square net of metal atoms. There is a tendency towards phase separation in order to achieve long‐range order. However, phasoid‐like crystallites have also been observed. Long‐range order is also achieved by the formation of ordered intergrowth compounds. They are characterised by a regular periodic sequence of lamellar slabs (each of one or a few unit cells thickness) of both basic structure types.