Structure and electrochemical properties of carbon aerogels polymerized in the presence of Cu

Copper-loaded organic aerogels were prepared by sol–gel polymerization of resorcinol and formaldehyde in a solution of Cu(NO₃)₂. Carbon aerogels derived from the heat-treatment of the organic precursor kept their particulate structure, according to TEM observations. The particle size in Cu-loaded carbon aerogel samples becomes larger with a higher concentration of Cu incorporated into their texture, due to the presence of Cu²⁺ rather than the pH conditions in the sol–gel process. The nitrogen adsorption measurement of Cu-loaded samples showed their characteristic pore structure, i.e., a combination of microporosity and mesoporosity both developed in their texture. Especially, their advanced microporosity, which was still found after carbonization at 1273 K, was very unique, considering that micropores in organic aerogels often decreased in size during heat-treatment around this temperature range. This microporosity could be related to their stacking structure of aromatic layers revealed by STAC–XRD analysis, indicating a looser packing of aromatic layers in their structure. Application of Cu-loaded samples to electric double-layer capacitor is also discussed from the viewpoint of the amount of Cu as well as the pore structure of the samples.     

Growth and morphology of the CuGaS2, CuAlSe2, CuGaSe2 and CuInS2 ternary compounds

Monocrystals of the ternary compounds CuGaS₂, CuAlSe₂, CuGaSe₂, and CuInS₂ were grown from their elements by transport reactions; their cell parameters and melting temperature were determined. The character of the phase transition in these compounds was found out and also the boundary conditions of growing the monocrystals as well as their dislocation structure (by etching).     

Mechanical activation of precursors for nanocrystalline materials

Nanostructured materials win big scientific interest and increasingly economic meaning through their specific exceptional properties. Precursors that were compacted by pressing and sintering are normally used preparation of materials. In present work, the influence of mechanical activation by grinding on the structure as well as on compacting and sintering behavior of oxides from magnesium, aluminium and silicon has been investigated. Starting materials for each metal oxide differ in microstructure, dispersity, and porosity. The influence of mechanical activation on the destruction of crystalline structure to nanocrystalline, as well as to the amorphous stage and the compaction of powders with nano‐particles, as well as structures with nanoscale pores have been compared. The possibilities of the consolidation of nanostructured materials were investigated. The mechanical activation took place in a disc vibration mill. The mechanical activated materials as well as their pressing and their sintering products were characterized by density, particle‐sizedistribution, specific surface, pore‐structure, microstructure, and crystallite size by X‐ray powder diffraction (XRD). The mechanical activation of the model‐substances led, in most cases, to an improvement of the compaction properties; thus, this improvement can be achieved with subsequent sintering densities up to 98% of the theoretical density. From these experiments, generalizations transferable to other materials can be made.     

Anisotropic properties of Nd:ReCOB (Re=Y,Gd):A low symmetry self-frequency doubling crystal

The anisotropy of low symmetry Nd:YCOB and Nd:GdCOB crystals, including their linear and nonlinear optical properties, as well as their laser and SFD properties, are discussed in detail, for the first time, in this paper. We have found the optimum directions of doubling-frequency for these crystals are not in the principle planes.     

Growth of ZnO bulk crystals: A review

A critical review is proposed of the different techniques of bulk growth of ZnO crystals for their use as a substrate in the homoepitaxial growth of this attractive compound. The crystals are assessed from their structural and electrical properties and from the structural properties and purity of homoepitaxial films grown on them by various techniques such as plasma-assisted molecular beam epitaxy, pulsed laser deposition, magnetron sputtering, chemical vapor deposition, metalorganic chemical vapor epitaxy, liquid phase epitaxy.     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.     

Diophantine laws for nets of the highest symmetries

The theoretical-numerical properties of the square and the hexagonal nets are presented as well as their characteristic triads of integers—the Denis numbers—applicable to the practical X-ray diffraction analysis of single crystals.     

Crystal chemistry of silicates with three-layer <Emphasis Type="Italic">TOT</Emphasis> and <Emphasis Type="Italic">HOH</Emphasis> modules of layered,chainlike, and mixed types

In view of new data on the chemical composition and structure of a series of natural layered silicates containing three-layer blocks and their corresponding microporous minerals with related fragments, their structural features; the structural conditionality of their properties; their transformation in the presence of isomorphism, decationation, and hydration; and the problems related to typomorphism and some other questions urgent for modern mineralogy have been considered. The structures are described in terms of threelayer modules of different forms and dimensions that are present in these structures. The composition and design of the general structural base of related series—three-layer modules forming layered or linear radicals—are also discussed. The minerals of these families differ in chemical composition, symmetry, and unit-cell parameters, as well as in the topological features associated with the type of condensation of the Si tetrahedra into layers or ribbons and the degree of condensation of M polyhedra in the central part of blocks: from layers and octahedral ribbons of different widths to chains and isolated polyhedra.     

Anisotropy of Electric Properties in Binary Cholesteric Mixtures

Dielectric permittivity and electric conductivity anisotropies were determined for cholesterol laurate, cholesterol caprilate as well as for their mixtures 25:75%, 50:50% and 75:25% (by weight). Connection between anisotropies of pure substances and their mixtures were found. The mixtures 75:25% and 25:75% have positive conductivities anisotropies within the cholesteric range as for the initial esters; the sign of the dielectric anisotropy is the same as for the prevailing ester. Within the smectic range the dielectric anisotropy is negative for both mixtures and pure compounds, in accordance to Carr's hypothesis with reference to the conduction mechanism in smectics.

The phase transitions are revealed in most cases by maxima or minima of the dielectric anisotropies.     

Liquid Crystalline Catalysis, 31, Monomolecular Rearrangements of Terpene Derivatives in Liquid Crystalline Solvents

The ability of limonene and linalool to rearrange in mesomorphic media is apparently determined by the constraints exerted by the solvent structure on the translational diffusions of the reactant solute molecules. Selective conversions seem to be promoted by the different media. Alkylcyclohexyl- and alkylbicyclohexyl-carboxylic acids and their mixtures with toluic acid have been used as solvents. The B structure of their smectic phases has been demonstrated by X-ray diffraction studies.     

A topological approach to studies of ordered structures of absorbed gases in host lattices (I). The structure of γ-PdD0.5

A graph-theoretical method is proposed which describes the deformation caused in the host lattice by absorbed gas atoms, as well as their ordering. The method predicts correctly the ordered γ-phase of PdD_0,5.     

Inference of Mechanical Properties from Instrumented Depth Sensing Indentation at Tiny Loads and Indentation Depths

Different hardness measures as Vickers, Brinell and Meyer hardness are discussed with respect to their physical interpretation. Meyer hardness is found to be best suited as a measure of plastic properties. The outline of a depth sensing nanoindentation experiment is described, and particular emphasis is given to the correct deduction of the contact area from indenter penetration data. Experimental complications, as phase transformations, finite machine compliance, thermal and pieco drift, and sample creep are detailed with, and their impact on the calculation of hardness and elastic modulus is shown. Furthermore the onset of yielding in dependence on critical load, indenter curvature and yield strength is discussed.     

The Influence of the X-ray Wavelength on the Behaviour of Polar Kossel Reflections

The Kossel effect permits a determination of polar directions in non-centrosymmetrical structures. To identify polar reflections unambiguously, differences — as large as possible — in their fine structures are necessary. These differences considerably depend on both the diffraction geometry and the characteristic X-ray wavelength applied. The reasons of such behaviour are deliberated upon hereinafter and a good harmony achieved of theoretical predictions and experimental findings.     

Comparison of growth methods for Si/SiO2 nanostructures as nanodot hetero-emitters for photovoltaic applications

Two different growth mechanisms are compared for the fabrication of Si/SiO₂ nanostructures on crystalline silicon (c-Si) to be used as hetero-emitter in high-efficiency solar cells: (1) The decomposition of substoichiometric amorphous SiO_x (a-SiO_x) films with 0 < x < 1.3 and (2) the dewetting of thin amorphous silicon (a-Si) layers.The grown layers are investigated with regard to their structural properties, their passivation quality for c-Si wafer substrates and their electrical properties in order to evaluate their suitability as a nanodot hetero-emitter. While by layer decomposition, no passivating nanodots could be formed, the dewetting process allows fabricating nanodot passivation layers at temperatures as low as 600 °C. The series resistance through Ag/[Si-nanodots in SiO₂]/c-Si/Al structures for dewetting is similar to nanostructured silicon rich SiO_x films. Still, a nanodot hetero-emitter which exhibits both a satisfying passivation of the substrate and induces a high band bending by doping at the same time could not be fabricated yet.     

PEG-6000对Mn-Zn铁氧体纳米粉体烧结特性的影响

利用化学共沉淀回流法制备Mn-Zn铁氧体纳米粉体的过程中,加入适量PEG-6000,试图通过在纳米颗粒表面形成一保护层以起到抑制其团聚的目的.研究结果表明,PEG-6000的加入不仅减小了纳米粒子的尺寸,还有效缓解了它们的团聚.将这些纳米Mn-Zn铁氧体粉体进行成型烧结,材料的起始磁导率随烧结温度的升高呈抛物线规律变化,并于1200 ℃达到最大值.而且添加PEG-6000的样品起始磁导率比未添加的提高了约20;.导致这一变化的原因应归咎于纳米粉体稳定性的改善以及烧结后材料内部组织均匀度的提高和晶粒尺寸的减小.     

Lattice vibrations of glasses

Measurements of the thermal conductivity of glasses have led to a model of their lattice vibrations. They are not described as waves, as they are in crystals, but as uncorrelated harmonic motions of individual atoms. The lattice vibrations of fully cerammed, crystalline glass ceramics have been found to be either waves, as in crystals, or vibrations of individual atoms, as in glasses. The understanding of the cause for this different behavior has been aided by studies of systematically doped crystals.     

Properties of freely suspended liquid crystal films and their applications

We report the review on the physical properties of the liquid crystal freely suspended films. The importance of the freely suspended films for the study of the fundamental problems of the self-confined systems as well as their practical implementations are demonstrated.     

Dielectric Spectroscopy of Side Chain Siloxane Liquid Crystal Copolymers

Side chain siloxane liquid crystal polymers (LCPs) are being investigated as potential optical storage media. Dielectric relaxation spectroscopy has been used to examine the real and imaginary components of permittivity as a function of frequency and temperature. The spectra obtained are discussed from the standpoint of both their molecular significance and their device implications. Spectra of liquid crystal homopolymers and a particular class of copolymers have been found to exhibit different features due to the larger free volume available to the mesogenic moieties in the copolymers. The relaxation behaviour of five LC copolymers is discussed and then two equivalent pairs of homopolymer and copolymer LCPs are considered in more detail. One pair shows anomalous relaxation behaviour and extra relaxation processes are attributed to internal reorientations.     

退役三元锂离子电池正极材料高效清洁回收技术研究进展

锂离子电池因其能量密度高、循环性能好、自放电低等优势在各个领域得到了广泛的应用。近年来,退役三元锂离子电池数量急剧增长,从保护环境和节约资源的角度来看,开展退役锂离子电池回收再生工艺研究是必要的。本文综述了退役三元锂离子电池回收再生技术的研究现状,指出对衰减程度不同的锂电池正极材料需采取灵活的梯级回收工艺路线,并详细介绍了退役锂电池正极材料的湿法冶金回收工艺和物理法修复再生技术,分析了它们的优缺点和存在的技术难点。最后,展望了退役锂离子电池回收利用的前景和发展方向。     

Zn2+掺杂对TiO2相变温度和晶粒尺寸的影响

采用溶胶-凝胶法制备了不同含量Zn2 掺杂的氧化钛粉体,利用TG-DTA、XRD测试技术检测了锌离子掺杂对锐钛矿和金红石相变及其晶体尺度的影响。试验结果表明,锌离子的掺入抑制了锐钛矿和金红石的相变,使相变温度提高,而且显著阻碍晶体的生长,从而获得纳米晶体。