Fabrication of monodispersed nickel flower-like architectures via a solvent-thermal process and analysis of their magnetic and electromagnetic properties

Monodispersed Ni flower-like architectures with size of 1–2 μm were synthesized through a facile solvent-thermal process in 1,2-propanediol solution in the presence of polyethylene glycol (PEG) and sodium alkali for electromagnetic absorption application. The Ni architectures are composed of nanoflakes, which assemble to form three dimensional flower-like structure, and the thickness of nanoflakes is about 10–40 nm. A possible formation mechanism for Ni flower-like architectures was proposed and it was confirmed by the control experiments. The Ni architectures exhibited a saturation magnetization (M_s) of 47.7 emu/g and a large coercivity (H_cj) of 332.3 Oe. The epoxy resin composites with 20 vol% Ni sample provided good electromagnetic wave absorption performance (reflection loss <−20 dB) in the range of 2.8–6.3 GHz over absorber thickness of 2.6–5.0 mm.     

环糊精分子管道的制备与应用

环糊精分子管道是一种基于环糊精制备的中空管状聚合物,因其特殊的空腔结构及与客体分子间的选择性组装现象而引起广泛关注。本文综述和比较了环糊精分子管道的主要制备方法,着重阐述了环糊精分子管道与客体分子间的选择性组装现象、机理及影响因素方面的研究成果。对环糊精分子管道的应用现状和潜在的应用价值进行了概括,最后提出了应予以重视...     

Syntheses and Crystal Structures of a Cadmium(Ⅱ) and a Zinc(Ⅱ) Complexes with the Flexible Ligand 1-Acetic Acid-2, 2'-biimidazole

Reactions of NaAcebiim(NaAcebiim = 1-acetic acid-2, 2′-biimidazole monosodium salt) and cadmium or zinc nitrate produce two supramolecular architectures, namely, 1D [Cd(Acebiim)(NO3)(H2O)]n(1) and 0D [Zn(Acebiim)2(H2O)2]·2H2O(2) in acidic aqueous solutions. Single-crystal X-ray diffraction analysis reveals that complex 1 crystallizes in the triclinic system, space group P1, and 2 is of monoclinic system, space group P21/n. In 1, two nitrate groups link two Cd(Ⅱ) ions forming [Cd2(NO3)2(H2O)2] as secondary building units that are interconnected by the Acebiim- ligand into an infinite ladder. In 2, the hydrogen-bonded synthon R22(16) between the N–H moieties and carboxylic acid link [Zn(Acebiim)2(H2O)2], generating a 1D-extended ribbon. Moreover, hydrogen bonds and π-π interactions further stabilize the 3D supramolecular architecture.     

Nanocoral architecture of TiO2 by hydrothermal process: Synthesis and characterization

TiO₂ thin films with novel nanocoral-like morphology were successfully grown directly onto the glass and conducting fluorine doped tin oxide coated glass substrates via multi-step hydrothermal (MSH) process. Titanium chloroalkoxide [TiCl₂ (OEt)₂ (HOEt)₂)] precursor was used in an aqueous saturated NaCl in presence of 1 mM HCl catalyst and HNO₃ peptizer at 120 °C. Reaction time varied from 3 to 12 h. The morphological features and physical properties of TiO₂ films were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Fourier transform IR spectroscopy, Fourier transform Raman spectroscopy, room temperature photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The surface morphology revealed the formation of TiO₂ corals having nanosized (30-40 nm) polyps. The photoelectrochemical properties of the TiO₂ nanocoral electrodes were investigated in 0.1 M NaOH electrolyte under UV illumination. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via controlled thickness of TiO₂ nanocorals and (ii) the substantial increase in short circuit photocurrent (J_sc) due to the improved charge transport through TiO₂ nanocorals prepared via MSH process. This approach would be quite useful for the fabrication of nanocoral architecture that finds key applications in photocatalysis, dye-sensitized solar cells and hybrid solar cells.     

Hydrophobic hydration

The problem of interaction between organic and water moieties (neutral or ionized water molecular species) is of particular interest in chemistry in view of its implications to physico-chemical behavior of chemical and biological systems. Hydration patterns which result from interaction between hydrophilic and hydrophobic species are non trivial in chemistry. The key issue is that water molecules are able to aggregate in extremely large variety of structural modes. Tetrahedral geometry of intermolecular bonding around water molecule is analogous in geometrical terms to that of intramolecular geometry of carbon atom, known as a source of infinite number of organic structures. In general, space filling with hydrogen bonded water molecules is rather low. It may be illustrated in the following way: volume of neonium atoms is comparable to that of water molecules whilst having atomic mass just 10% higher than molecular mass of water. Thus, liquid neonium and liquid water would have similar densities if molecular packing is of comparable efficiency. The real values are much different, however. Liquid neonium at its boiling temperature has density of 1.20 g cm^–3 , thus displaying significantly denser packing that that of water molecules. It certainly means that solid or liquid water has a ‘porous’ structure and may lead to molecular inclusion of foreign (guest) species in the intermolecular space of water framework. This property is not that simple, however, since inclusion of foreign (guest) species is, as a rule, associated with rearrangement of the host framework structure [1]. Anyway, inefficient packing of the mono-component host solid phases may be considered as a prerequisite for its pronounced clathration ability.     

Influence of the molecular architecture of low‐density polyethylene on the texture and mechanical properties of blown films

Three types of low‐density polyethylene materials were investigated with respect to the influence of the molecular architecture on the mechanical and use properties of blown films. The materials were a branched polyethylene synthesized by free‐radical polymerization under high‐pressure (HP‐LDPE), a linear ethylene–hexene copolymer (ZN‐LLDPE) produced by low‐pressure Ziegler–Natta catalysis, and an ethylene–hexene copolymer (M‐LLDPE) from metallocene catalysis. The extrusion and blowing conditions were identical for the three materials, with a take‐up ratio of 12 and a blow‐up ratio of 2.5. The blown films displayed a decreasing puncture resistance in the order M‐LLDPE, ZN‐LLDPE, and HP‐LDPE. In parallel, the tear resistance of the films became increasingly unbalanced in the same order of the polymers. The morphological study showed an increased anisotropy of the films in the same polymer order, the crystalline lamellae being increasingly oriented normal to the take‐up direction. This texturing caused a detrimental effect on the mechanical properties of the films, notably increasing the capacity for crack propagation. The phenomenon was ascribed to the kinetics of chain relaxation in the melt that governed the ability of the chains to recover an isotropic state from the flow‐induced stretching before crystallization. The puncture resistance was examined in terms of both texture and strain‐hardening capabilities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 327–340, 2003     

用于电视跟踪系统的并行体系结构研究

本文从计算机并行体系结构的角度研究了适用于电视跟踪器系统的结构,针对其大数据流量与极高处理速度的特点,提出了多指令流多数据流(MIMD)和双总线的布局,达到了电视信号实时处理的目的,实际使用结果证明分析和设计正确、合理,技术先进.     

基于SystemC的事务级AMBA总线模型的设计与实现

针对目前SoC设计中的时间瓶颈，根据系统建模语言SystemC对SoC进行事务级建模的方法。提出并实现了采用该方法构建基于AMBA规范的SoC片内总线模型的方案．模型采用了SystemC 2．0的接口、端口和通道的概念，这使模型具有很好的开放性和可扩展性．模型各部分间的通信通过调用各接口内定义的函数来进行，模型运行时只使用SystemC自带的轻量级仿真内核．实验结果表明：本总线模型完全符合AMBA2．0规范，可以有效克服目前SoC软硬件协同设计中的时间瓶颈．     

建筑节能薄膜的设计与制备

对介质－金属组合的建筑节能薄膜进行了理论设计，给出双导和三层膜的理论参数，用计算机模拟了大面积薄膜的膜厚均匀性分布，获得了最佳的蒸发源配置，实验上达到了满足实际使用的均匀性要求，最后给出了实际样品的光谱特性。