Antiplane shear of a strip containing a staggered array of rigid line inclusions

Motivated by the increased use of fibre-reinforced materials, we illustrate how the effective elastic modulus of an Isotropic and homogeneous material can be increased by the insertion of rigid inclusions. Specifically, we consider the two-dimensional antiplane shear problem for a strip of material. The strip is reinforced by introducing two sets of ribbon-like, rigid inclusions perpendicular to the faces of the strip. The strip is then subjected to a prescribed uniform displacement difference between its faces, see Figure 1. It should be noted that the problem posed is equivalent to that of the uniform antiplane shear problem for an infinite two-dimensional material containing a staggered array of rigid inclusions (see [1] for a review of antiplane problems in the literature). The problem is reduced in standard fashion [2–6] to a mixed boundary value problem in a rectangular domain, whose closed form solution given in terms of integrals of Weierstrassian Elliptic functions, is obtained via triple sine series techniques. The effective shear modulus of the reinforced strip can now be calculated and compared with the shear modulus of a strip without inclusions. Also obtained are the stress singularity factors at the end tips of the inclusions. Numerical results are presented for several different reinforcement geometries.     

Some cluster and condensed-phase properties of light elements: B to P

Attention is first drawn to disordered condensed phases of Si and C. Amorphous Si, with clear-cut tetrahedral coordination, is treated by combining sp³ hybridization with a random network model of structure, X-ray and electron diffraction experiments confirm both electron density and structural models. Recent work using the Car-Parrinello technique is then reviewed, with the aim of comparing and contrasting amorphous C and Si and their liquid phases. After a brief review of the structure and bonding in clusters of Al and P atoms, some results on clusters of Na are presented and related to cohesion in the condensed metallic phase. Then, fission of doubly charged Na clusters is treated at some length and, in particular, is related to quantum chemical procedures. A short summary concerning π-bands in graphitic and boron nitride layers is followed by a discussion of BN alternants, both buckytubes and octahedral symmetry cages being considered, along with C analogs. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 695–707, 1997     

Ion Conducting Polyethylene Oxide-Based Polymer Electrolyte Dopped with Ionic Liquid-Trifluoromethanesulfonic Chloride

In last few decades, polymer electrolyte is the most promising candidate for the fabrication of electrochemical devices. In current work, the influence of adding the room-temperature ionic liquid (trifluoromethanesulfonic chloride – CClF3O2S) in polyethylene oxide (PEO): ammonium iodide (NH4I) polymer electrolyte has been studied. The IL-doped polymer electrolyte films are synthesized by solution casting method with varying stoichiometric ratios. Several experimental techniques including optical polarizing microscope, impedance spectroscopy, X-ray diffraction, Linear sweep voltammetry, Ionic transference number thermal analysis, and electrical conductivity measurements at room temperature have been studied in detail. The complex material's maximum conductivity has been determined to be 3.3 × 10⁻⁵ S cm⁻¹ at room temperature. The POM images show the increase in amorphous region which further confirm the improvement in ionic conductivity. Ionic transference number 0.96 shows the system is purely ionic in nature. The ESW of the IL doped polymer electrolyte is also sawed to be 3.32 V which is suitable for the fabrication of electrochemical devices.     

Ni-Ce-P非晶态合金催化剂用于氯代硝基苯液相加氢制氯代苯胺

 采用化学还原法制备了Ni-Ce-P非晶态合金催化剂,用X射线能谱、 X射线衍射、 选区电子衍射、 透射电子显微镜和差热分析等方法对催化剂的组成、结构、形貌及热稳定性进行了表征,讨论了Ni-Ce-P非晶态合金催化剂的催化性能和结构的关系,并以氯代硝基苯液相加氢合成氯代苯胺为探针反应考察了所制备催化剂的加氢性能. 研究结果表明,在不加脱卤抑制剂的情况下,在110 ℃下反应时所选4种反应物的转化率均可达99.8%, 脱卤率小于1.8%, 且Ni-Ce-P非晶态合金的活性为Ni-P非晶态合金催化剂的2倍,表现出较高的加氢性能和抑制脱卤性能.     

Photoelectrochemical Behaviour of Hydrogenated Amorphous Silicon(a-Si:H) Films

Photoelectrochemical techniques have been employed in the investigation of p-type, n-type and intrinsic hydrogenated amorphous silicon(a-Si:H) films. The results show that the photocurrent response of the films strongly depends on the doped type electrolyte solution and the redox potential of the redox couples. Intrinsic a-Si:H film yields a stable photocurrent much higher than the p- and n-type ones. Based on the measurements, the energy levels and flatband potential of the intrinsic a-Si:H film are given, and the mechanisms of charge transfer in photoelectrochemical cell (PEC) are discussed.     

Photocatalytic Crystalline and Amorphous TiO2 Nanotubes Prepared by Electrospinning and Atomic Layer Deposition

In this work core/shell composite polymer/TiO₂ nanofibers and from those TiO₂ nanotubes were prepared. First, poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) fibers were synthetized by electrospinning. They were covered with a 100 nm thick amorphous TiO₂ layer by atomic layer deposition at 50 °C. Later the polymer core was removed by two different methods: dissolution and annealing. In the case of dissolution in water, the as-prepared TiO₂ nanotubes remained amorphous, while when annealing was used to remove the polymers, the TiO₂ crystallized in anatase form. Due to this, the properties of amorphous and crystalline TiO₂ nanotubes with exactly the same structure and morphology could be compared. The samples were investigated by SEM-EDX, ATR-IR, UV-Vis, XRD and TG/DTA-MS. Finally, the photocatalytic properties of the TiO₂ nanotubes were studied by decomposing methyl-orange dye under UV light. According to the results, crystalline anatase TiO₂ nanotubes reached the photocatalytic performance of P25, while amorphous TiO₂ nanotubes had observable photocatalytic activity.     

Fe-W非晶镀层的磷化及在NaCl溶液中的腐蚀行为

ＦｅＷ非晶态合金镀层在酸性溶液中具有高耐蚀性能,但在中性和碱性溶液,特别是在氯化钠溶液中耐蚀性能差［１］,如在３０℃、１ｍｏｌ／ＬＨＣｌ溶液中,ＦｅＷ非晶镀层的腐蚀速率约为不锈钢ＳＵＳ３０４的１／１５;在６０℃、０５ｍｏｌ／ＬＨ２ＳＯ４溶液中约...     

Mapping of chemically accessible regions in semicrystalline polymers

Important chemical and mechanical properties in semicrystalline polymers are determined by the noncrystalline or nonordered regions. Hence, characterizing these regions is important in developing a morphological model to better define and predict the chemical and mechanical behavior of polymeric materials. With this objective, preferential tagging was accomplished by covalent linking of a heavy element to poly(ethylene terephthalate) (PET). In scanning transmission electron microscopy (STEM), contrast was obtained using a low concentration of thallium (0.4%), the tagging element, thus providing a map of the more accessible regions within the semicrystalline structure. Differential scanning calorimetry (DSC) and wide-angle x-ray scattering (WAXS) were used to characterize the PET film. Elemental analysis using energy dispersive x-ray analysis (EDAX) was used to confirm the presence of the heavy element in the tagged regions. The STEM imaging results were then compared with the characterization results from the DSC and WAXS measurements to gain an understanding of the domains and their size ranges in the semicrystalline microstructure of PET. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1443–1450, 1998     

Polymorphic crystal forms and morphology of syndiotactic polystyrene in miscible states

X-ray diffraction and optical microscopy characterization were performed to evaluate the phenomenon of alteration of polymorphism of syndiotactic polystyrene (s-PS) in the presence of other blending miscible polymers: poly(2,6-dimethyl-p-phenylene oxide) (PPO) or atactic polystyrene (a-PS). Both α and β crystal forms were observed in the neat s-PS sample, but only β-form crystal was found in miscible blends of s-PS with a-PS or PPO. The order and neighboring chain segments of neat s-PS are different from those of s-PS/PPO or s-PS/a-PS blends; thus, it is plausible that the greater randomness in the melt state of s-PS/a-PS or s-PS/PPO blends might be unfavorable for formation of α-form crystals from melts. The final spherulitic morphology the s-PS/a-PS or s-PS/PPO blends suggests that the amorphous-state miscibility of does not change much the spherulitic structure of s-PS. The radial growth rate is, in general, depressed with the presence of blending miscible polymers in s-PS of equal T_g or PPO of higher T_g. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2725–2735, 1998     

Verification of the microdomain model of crystallinity in polyvinyl chloride by electron microscopy

A study of the fine scale microstructure of PVC was carried out using a combination of high resolution transmission electron microscopy and digital image analysis techniques. The images obtained contained a degree of order of the approximate size and distribution as predicted by the microdomain model of crystallinity in PVC. The microdomain model for crystallinity in PVC has been built up from previous studies using various analytical techniques including wide- and small-angle x-ray diffraction and differential scanning calorimetry. Earlier studies using transmission electron microscopy did not find any direct evidence supporting this model. Significant advances in both electron microscope and image processing technology had taken place since the earlier microscopic studies. The TEM imaging and image analysis procedures that have been utilized in this research may be applicable to the imaging of very fine scale ordering in other polymers. © 1996 John Wiley & Sons, Inc.