Effects of layer orientation of CFRP strengthened steel hollow members

This paper reveals the effects of layer orientation on structural behaviour of three layers configured (LHL, HHL, LLH) CFRP strengthened circular hollow section (CHS) members subjected to bending. The beams were loaded to failure under four-point bending. The structural behaviour of the CFRP strengthened tubular steel beams with various layer orientations were presented in terms of failure load, stiffness, composite beam action and modes of failure. The LHL and LLH layers oriented strengthened beams perform slightly better than HHL layers oriented strengthened beams. The LHL and LLH layers oriented treated beams showed very similar structural behaviour.

Influence of seed layer orientation on the growth and physical properties of SnS nanostructures

Stoichiometric tin (II) sulfide (SnS) nano-structures were synthesized on SnS(010)/glass substrates using a simple and low-temperature chemical solution method, and their physical properties were investigated. The as-synthesized SnS nanostructures exhibited orthorhombic crystal structure and most of the nanocrystals are preferentially oriented along the <010> direction. These nanostructures showed p-type electrical conductivity and high electrical resistivity of 93 Omega cm. SnS nanostructures exhibited a direct optical band gap of 1.43 eV. While increasing the surrounding temperature from 20 to 150 degrees C, the electrical resistivity of the structures decreased and exhibited the activation energy of 0.28 eV.

Experimental and numerical investigation of the behaviour of CFRP strengthened CHS beams subjected to bending

This paper presents the results of an experimental and numerical program to investigate the circular hollow section (CHS) beams, strengthened using Carbon Fibre Reinforced Polymer (CFRP) sheets. The circular hollow shaped steel beams bonded with different CFRP layer orientations were tested under four-point bending. The mid-span deflection, service load and failure load were recorded. The LHL (where L, first inner longitudinal layer, H, second hoop layer and L, third outer longitudinal layer) and LLH (where L, first inner longitudinal layer, L, second longitudinal layer and H, third outer hoop layer) layer oriented strengthened beams perform slightly better than HHL (where H, first inner hoop layer, H, second hoop layer and L, third outer longitudinal layer) layer oriented strengthened beams. The LHL and LLH layer oriented treated beams showed very similar structural behaviour. Numerical analyses were then conducted on the CFRP strengthened steel CHS beams. The validity of the models has been assessed by comparing the failure loads and mid-span deflections. The effects of various parameters such as bond length, section types, tensile modulus of CFRP, adhesive layer thickness and adhesive types have been studied.

The growth of gamma-LiAlO2 layer with a highly-preferred orientation on (0001) sapphire

Using vapor transport equilibration (VTE) technique we succeeded in the fabrication of single-phase gamma-LiAlO2 layer on (0001) sapphire substrate. X-ray diffraction indicated that the as-fabricated layer was highly textured with [100] orientation at proper VTE treatment temperature range from 1050 degrees C to 1100 degrees C. The main factors affecting the quality of the gamma-LiAlO2 layer were investigated by SEM and transmission spectra. These results reveal the possibility of fabricating gamma-LiAlO2 (100)//sapphire (0001) composite substrate for GaN-based epitaxial film by VTE.

Origin of the vertical-anticorrelation arrays of InAs/InAlAs nanowires with a fixed layer-ordering orientation

InAs/In0.52Al0.48As nanowire multilayer arrays were grown on (001) InP substrate by molecular-beam epitaxy. The structural property of the arrays was investigated by transmission electron microscopy. The results clearly showed the formation of InAs nanowires, evolution of InAs/InAlAs interface, and composition and thickness modulations in the InAlAs spacer layer. A fixed spatial ordering of InAs/InAlAs nanowires was revealed for all the samples. Regardless of the change in InAlAs spacer thickness of different samples, (i) the nanowires of one InAs layer are positioned above the nanowire spacing in the previous InAs layer and (ii) the layer-ordering orientation angle of nanowires is fixed. The results were explained from the viewpoint of the growth kinetics. The effect of InAlAs spacers is suggested to play an important role on the spatial ordering of the nanowire arrays. (C) 2002 American Institute of Physics.

InAs/ln(0.52)Al(0.48)As quantum wire structure with the specific layer-ordering orientation on InP(001)

Quantum wires were formed in the 6-period InAs/In0.52Al0.48As structure on InP(0 0 1) grown by molecular beam epitaxy. The structure was characterized with transmission electron microscopy. It was found that the lateral periodic compositional modulation in the QWR array was in the [1 (1) over bar 0] direction and layer-ordered along the specific orientation deviating from the [0 0 1] growth direction by about 30 degrees. This deviating angle is consistent with the calculation of the distribution of elastic distortion around quantum wires in the structure using the finite element technique. (C) 1999 Elsevier Science B.V. All rights reserved.

Orientation dependent molecular friction on organic layer compound crystals

High resolution friction force maps of the benzylammonium terminated crystalline surface of a layer compound are presented. The lateral force map acquired with an atomic force microscope, reveals a significant contrast between different molecular orientations yielding molecular rows which differ from their neighboring ones. The single crystals are formed by stacks of copper oxalate sheets sandwiched between stereoregular organic cations, resulting in highly organized surface structures. Single molecular defects are observed at small loads. The experimental results are compared with numerical calculations which indicate a transition from an unperturbed state at small loads to a distorted state at higher loads. (C) 2011 American Institute of Physics.

Influence of smectite suspension structure on sheet orientation in dry sediments : XRD and AFM applications

The structure-building phenomena within clay aggregates are governed by forces acting between clay particles. Measurements of such forces are important to understand in order to manipulate the aggregate structure for applications such as dewatering of mineral processing tailings. A parallel particle orientation is required when conducting XRD investigation on the oriented samples and conduct force measurements acting between basal planes of clay mineral platelets using at. force microscopy (AFM). To investigate how smectite clay platelets were oriented on silicon wafer substrate when dried from suspension range of methods like SEM, XRD and AFM were employed. From these investigations, we conclude that high clay concns. and larger particle diams. (up to 5 μm) in suspension result in random orientation of platelets in the substrate. The best possible laminar orientation in the clay dry film, represented in the XRD 0 0 1/0 2 0 intensity ratio of 47 was obtained by drying thin layers from 0.02 wt.% clay suspensions of the natural pH. Conducted AFM investigations show that smectite studied in water based electrolytes show very long-range repulsive forces lower in strength than electrostatic forces from double-layer repulsion. It was suggested that these forces may have structural nature. Smectite surface layers rehydrate in water environment forms surface gel with spongy and cellular texture which cushion approaching AFM probe. This structural effect can be measured in distances larger than 1000 nm from substrate surface and when probe penetrate this gel layer, structural linkages are forming between substrate and clay covered probe. These linkages prevent subsequently smooth detachments of AFM probe on way back when retrieval. This effect of tearing new formed structure apart involves larger adhesion-like forces measured in retrieval. It is also suggested that these effect may be enhanced by the nano-clay particles interaction.

Oblique-Shock-Wave/Boundary-Layer Interaction Using Near-Wall Reynolds-Stress Models

A synthesis is presented of the predictive capability of a family of near-wall wall-normal free Reynolds stress models (which are completely independent of wall topology, i.e., of the distance fromthe wall and the normal-to-thewall orientation) for oblique-shock-wave/turbulent-boundary-layer interactions. For the purpose of comparison, results are also presented using a standard low turbulence Reynolds number k–ε closure and a Reynolds stress model that uses geometric wall normals and wall distances. Studied shock-wave Mach numbers are in the range MSW = 2.85–2.9 and incoming boundary-layer-thickness Reynolds numbers are in the range Reδ0 = 1–2×106. Computations were carefully checked for grid convergence. Comparison with measurements shows satisfactory agreement, improving on results obtained using a k–ε model, and highlights the relative importance of redistribution and diffusion closures, indicating directions for future modeling work.

Conformation and orientation of alkyl chains in the layered organic-inorganic hybrids: (CnH2n+1NH3)(2)PbI4 (n=12,16,18)

Layered organic inorganic hybrids based on perovskite-derived alkylammonium lead halides have been demonstrated as important new materials in the construction of molecular electronic devices. Typical of this class of materials are the single-perovskite slab lead iodides of the general formula (CnH2n+1NH3)(2)PbI4. While for small n, these compounds are amenable to single-crystal structure determination, the increasing degree of disorder in the long chain (n = 12,14...) compounds makes such an analysis difficult. In this study, we use powder X-ray diffraction, and vibrational and C-13 NMR spectroscopies to establish the conformation, orientation and organization of hydrocarbon chains in the series of layered alkylammonium lead iodides (CnH2n+1NH3)(2)PbI4 (n = 12,16,18). We find that the alkyl chains adopt a tilted bilayer arrangement, while the structure of the inorganic layer remains invariant with respect to the value of n. Conformation-sensitive methylene stretching modes in the infrared and Raman spectra, as well as the C-13 NMR spectra indicate that bonds in the methylene chain are in trans configuration. The skeletal modes of the alkyl chain in the Raman spectra establish that there is a high degree of all-trans conformational registry for the values of n studied here. From the orientation dependence of the infrared spectra of crystals of (CnH2n+1NH3)(2)PbI4 ( n = 12,16), we find that the molecular axis of the all-trans alkyl chains are tilted away from the interlayer normal by an angle of 55degrees. This value of this tilt angle is consistent with the dependence of the c lattice expansion as a function of n, as determined from powder X-ray diffraction.

Permeability of two-layer soils

The equivalent coefficient of permeability of a stratified soil system calculated theoretically has been observed to be not the same as that directly measured, when the flow is normal to the orientation of the bedding planes. A hypothesis has been proposed in this investigation to explain this deviation according to which the permeability of the exit layer controls whether the measured permeability is greater or lesser than the theoretically calculated value. The proposed hypothesis has been used to successfully and satisfactorily explain the experimental observations made with the two-layer systems. It has been shown that the coefficient of permeability of a soil in a layered system cannot be considered as its property and that it depends upon the permeabilities of adjoining layers, their thicknesses, and the flow direction.

Effect of lattice orientation on crack tip constraint in ductile single crystals

In this work, the effect of lattice orientation on the fields prevailing near a notch tip is investigated pertaining to various constraint levels in FCC single crystals. A modified boundary layer formulation is employed and numerical solutions under mode I, plane strain conditions are generated by assuming an elastic-perfectly plastic FCC single crystal. The analysis is carried out corresponding to different lattice orientations with respect to the notch line. It is found that the near-tip deformation field, especially the development of kink or slip shear bands is sensitive to the constraint level. The stress distribution and the size and shape of the plastic zone near the notch tip are also strongly influenced by the level of T-stress. The present results clearly establish that ductile single crystal fracture geometries would progressively lose crack tip constraint as the T-stress becomes more negative irrespective of lattice orientation. Also, the near-tip field for a range of constraint levels can be characterized by two-parameters such as K-T or J-Q as in isotropic plastic solids.

InAs0.3Sb0.7 films grown on (100) GaSb substrates with a buffer layer by liquid-phase epitaxy

The growth of InAsxSb1-x films on (100) GaSb substrates by liquid-phase epitaxy (LPE) has been investigated and epitaxial InAs0.3Sb0.7 films with InAs0.9Sb0.09 buffer layers have been successfully obtained. The low X-ray rocking curve FHWM values of InAs0.3Sb0.7 layer shows the high quality of crystal-orientation structure. Hall measurements show that the highest electron mobility in the samples obtained is 2.9 x 10(4) cm(2) V-1 s(-1) and the carrier density is 2.78 x 10(16)cm(-3) at room temperature (RT). The In As0.3Sb0.7 films grown on (10 0) GaSb substrates exhibit excellent optical performance with a cut-off wavelength of 12 mu m. (c) 2007 Elsevier B.V. All rights reserved.

Analysis on the spin reorientation of GdFeCo/DyFeCo exchange-coupled double-layer films

In this paper, GdFeCo/DyFeCo exchange-coupled double-layer films used for center aperture type magnetically induced super resolution were investigated through experiments and theoretical calculation. The samples were prepared by magnetron sputtering method. The polar Kerr effect was measured to prove the spin reorientation of the readout layer. Theoretical study of magnetization profiles was performed on the basis of the mean-field theory and the continuum model. The theoretical results showed that the magnetization orientation of the readout layer changed gradually from in-plane to out-of-plane with the rise of the temperature. Theoretical analysis explained the experimental results successfully. (c) 2005 Elsevier B.V. All rights reserved.