Type Of Preferred Orientation Research Articles

Three-dimensional analysis of load-dependent changes in the orientation of dermal collagen fibers in human skin: A pilot study

The availability of quantitative structural data on the orientation of collagen fibers is of crucial importance for understanding the behavior of connective tissues. These fibers can be visualized using a variety of imaging techniques, including second harmonic generation (SHG) microscopy. However, characterization of the collagen network requires the accurate extraction of parameters from imaging data. To this end, several automated processes have been developed to identify the preferred orientation of collagen fibers. Common methods include fast Fourier transforms and curvelet transforms, but these tools are mostly used to infer a single preferred orientation.The purpose of this pilot study was to develop an easy procedure for comprehensively comparing multiple human skin samples with the goal of analyzing load-dependent changes via SHG microscopy. We created a 3D model based upon 2D image stacks that provide fiber orientation data perpendicular and parallel to the plane of the epidermis. The SHG images were analyzed by CurveAlign to obtain angle histogram plots containing information about the multiple fiber orientations in each single image. Subsequently, contour plots of the angle histogram intensities were created to provide a useful visual plotting method to clearly show the anomalies in the angle histograms in all samples.Our results provided additional details on how the collagen network carries a load. In fact, analysis of SHG images indicated that increased stretch was accompanied by an increase in the alignment of fibers in the loading direction. Moreover, these images demonstrated that more than one type of preferred orientation is present. In particular, the 3D network of fibers appears to have two preferred orientations in the planes both perpendicular and parallel to the plane of the epidermis.

Comparison of rolling texture of austenite and ferrite phases of duplex steel with single-phase austenitic and ferritic steel

In this contribution, the behavior of three types of steel after rolling was investigated. Ferritic and austenitic steels or phases have different mechanical and thermal properties. Due to their mutual influence during plastic deformation, it is possible to suppose the differences between preferred orientations of austenite and ferrite phases in duplex steel and single-phase austenitic and ferritic steels. For this reason, the preferred orientations of austenite and ferrite phases of rolled duplex steel were compared with rolled single-phase austenitic and ferritic steel. The 0–50% reductions of rolled steel plates were selected. Mainly, the strength and type of preferred orientation were compared in the relation to reduction and material. For this purpose, the rolled surfaces were measured by X-ray diffraction. The significant differences between intensities and types of texture components were investigated. For austenite-ferrite interaction during plastic deformation and phase transformation, samples were analysed by electron back-scattered diffraction. The Kurdjumov-Sachs orientation relationship was investigated.

Piezoelectric K0.5Na0.5NbO3 Ceramics Textured Using Needlelike K0.5Na0.5NbO3 Templates

Improved performance by texturing has become attractive in the field of lead‐free ferroelectrics, but the effect depends heavily on the degree of texture, type of preferred orientation, and whether the material is a rotator or extender ferroelectric. Here, we report on successful texturing of K0.5Na0.5NbO3 (KNN) ceramics by alignment of needlelike KNN templates in a matrix of KNN powder using tape casting. Homotemplated grain growth of the needles was confirmed during sintering, resulting in a high degree of texture parallel to the tape casting direction (TCD) and the aligned needles. The texture significantly improved the piezoelectric response parallel to the tape cast direction, corresponding to the direction of the strongest <001>pc orientation, while the response normal to the tape cast plane was lower than for a nontextured KNN. In situ X‐ray diffraction during electric field application revealed that non‐180° domain reorientation was enhanced by an order of magnitude in the TCD, compared to the direction normal to the tape cast plane and in the nontextured ceramic. The effect of texture in KNN is discussed with respect to possible rotator ferroelectric properties of KNN.

Characterization of the texture of silicide films using electron backscattered diffraction

Electron backscattered diffraction (EBSD) was used to characterize the texture of NiSi films. The various texture components (i.e., the types of preferred orientation, e.g., axiotaxy or epitaxy) could be identified, and their volume fraction could be quantified. Moreover, the spatial distribution of texture components could be studied in blanket films. Orientation imaging microscopy using EBSD is a promising technique to study the texture of silicide or germanide films both on blanket and patterned substrates.

An off-normal fibre-like texture in thin films on single-crystal substrates.

In the context of materials science, texture describes the statistical distribution of grain orientations. It is an important characteristic of the microstructure of polycrystalline films, determining various electrical, magnetic and mechanical properties. Three types of texture component are usually distinguished in thin films: random texture, when grains have no preferred orientation; fibre texture, for which one crystallographic axis of the film is parallel to the substrate normal, while there is a rotational degree of freedom around the fibre axis; and epitaxial alignment (or in-plane texture) on single-crystal substrates, where an in-plane alignment fixes all three axes of the grain with respect to the substrate. Here we report a fourth type of texture--which we call axiotaxy--identified from complex but symmetrical patterns of lines on diffraction pole figures for thin films formed by solid-state reactions. The texture is characterized by the alignment of planes in the film and substrate that share the same d-spacing. This preferred alignment of planes across the interface manifests itself as a fibre texture lying off-normal to the sample surface, with the fibre axis perpendicular to certain planes in the substrate. This texture forms because it results in an interface, which is periodic in one dimension, preserved independently of interfacial curvature. This new type of preferred orientation may be the dominant type of texture for a wide class of materials and crystal structures.

Perturbation growth in terms of barotropic alignment properties

AbstractIn order to study the error growth due to initial uncertainties in the model state, this paper examines the alignment dynamics of the perturbation velocity vector in quasi‐geostrophic flows. In a barotropic context, the time evolution of the perturbation velocity field is the sum of two terms: (i) the stretching of the perturbation velocity vector by the basic‐state velocity‐gradient tensor (denoted ∇<OVBAR>u</OVBAR>) and (ii) the perturbation ageostrophic pressure gradient, which also depends on ∇<OVBAR>u</OVBAR>. Different analytical results show that such a system has two types of preferred orientation that induce kinetic‐energy growth: one orientation concerns one eigenvector of ∇<OVBAR>u</OVBAR>, the other one is linked to a fixed point of the orientation equation of the perturbation velocity vector written in strain coordinates. This analytical diagnostic is confirmed by using Monte‐Carlo techniques in a quasi‐geostrophic oceanic‐basin model of a stratified wind‐driven double‐gyre circulation, and these orientations are shown to be the most probable. These preferred orientations are of great importance for diagnosing the most probable kinetic‐energy generation rate at each grid point. An interesting outcome is that the kinetic‐energy error field is localized in regions where the norm of ∇<OVBAR>u</OVBAR> is large. Copyright © 2003 Royal Meteorological Society

Twinning effects in polycrystalline hexaphenyl thin films

A new type of preferred orientation is observed within polycrystalline films of hexaphenyl molecules (C 36 H 26 ). The thin films are prepared by physical vapour deposition in ultra-high vacuum on highly cleaned glass and Al substrates. The preferred orientation is characterised by X-ray diffraction using pole figure and rocking curve measurements. The fibre texture is observed with the (211) crystallographic planes of the hexaphenyl crystallites parallel to the substrate surface. This unusual type of preferred orientation is explained by reflection twinning of the crystallites.

Preferred Orientation of Copper Phthalocyanine Thin Films Evaporated on Amorphous Substrates

A series of copper phthalocyanine thin films were prepared on amorphous substrates using physical vapor deposition at ambient temperature. Different sample preparation conditions were used: the deposition rate was varied, and the substrates was static or rotating. The preferred orientation in the thin film was studied as a function of the deposition conditions. X-ray diffraction analysis was performed using θ/2θ and pole figure measurements. In the case of layers prepared at low deposition rates and using nonrotating substrates, a very strong fiber texture was detected with (100) crystallographic planes oriented preferably parallel to the substrate surface. At higher deposition rates, an additional second type of preferred orientation was observed with (110) planes oriented preferably parallel to the substrate surface. In the case of layers prepared with rotational substrates, the (110) type of preferred orientation was quantitatively more strongly developed. If we consider electronic band structure calculations, these results imply that the electron/hole transport through the thin films is enhanced for films prepared at high deposition rates and rotating substrates.

Neutron Texture Investigations on Natural Mt. Isa Chalcopyrite Ore – Part II: Preferred Orientation of Chalcopyrite After Different Experimental Deformation Conditions

Natural chalcopyrite samples from Mt. Isa, Australia were axially shortened at a constant confining pressure of 300 (400) MPa, at different temperatures from 25–450°C, in the strain rate range of 3 · 10−5 − 6 · 10−8sec−1. Neutron diffraction texture analyses of all deformed samples were carried out and compared to the preferred orientation before the experimental deformation.The preferred orientation of the experimentally undeformed samples consists of three main orientation components, which become weaker with deformation at temperatures to 200°C. One or two new components (A, B) develop with the c‐axes perpendicular to the principal strain direction. At a deformation temperature of 250°C and to slower strain rates at 200°C the relics of the original components are stronger. After deformation at temperatures of 300°C to 450°C in general two different types of preferred orientation were detected. One type (2NF) shows two different new components (A*, C), the original components are completely dissolved. The other type (IN) shows the original components partially more concentrated, especially to slower strain rates, and shifting into the directions of the new components of the type 2NF.

Stress in chemically vapour-deposited silicon films

Stress in silicon films was investigated by X-ray diffraction. Films 0.5–0.6 microm thick were deposited onto single-crystal silicon substrates covered with thermally grown amorphous SiO 2. The investigations were carried out for films deposited over the temperature ranges 500–800°C in a nitrogen atmosphere and 650–1070°C in hydrogen. The influence of the volume ratio of silane to carrier gas on the stress in the silicon films was also examined. All the silicon films were compressively stressed but the stress was not a linear function of the substrate temperature. The experimental data indicate that the structure of the film and the type of preferred orientation have a marked influence on the film stress. The most stressed films were those with an amorphous structure and those with 〈110〉 preferred orientation, irrespective of the atmosphere in which the films were deposited. The least stressed films were randomly oriented polycrystalline and the stress in these decreased as the substrate temperature was increased.

Preferred orientation of silicate spinel inferred from experimentally deformed aggregates of trevorite.

Syntectonic recrystallization experiments have been done on the synthetic fine-grained aggregate of trevorite (NiFe2O4; a spinel type mineral) analogous to the γ-(Mg, Fe)2SiO4 in the upper mantle by means of a constant strain rate apparatus under various physical conditions: strain rates from 10-3 to 10-6 s-1, homologous temperatures from 0.56 to 0.80, and confining pressure of 0.6 GPa. An X-ray pole figure goniometry is employed to describe the quantitative orientation distribution of spinel crystallites in uniaxially deformed aggregates. The obtained inverse pole figures indicate that two types of preferred orientation have been produced during the axial deformations both in compression and tension. The lower temperature and faster strain rate yield the preferred orientation of type I: [1 1 0]//compression axis and [1 0 0]//tension axis, while the higher temperature and slower strain rate yield type II: [1 0 0]//compression axis and [1 0 0]//tension axis. The generation of the two types of preferred orientation is caused by grain rotation due to slip in constituent grains in an aggregate, and syntectonic recrystallization, respectively. The present results suggest (1)γ-(Mg, Fe)2SiO4 has a considerable degree of preferred orientation in the upper mantle, (2) the preferred orientation is probably of type II rather than of type I under the mantle conditions, and (3) the detectable degree of shear wave anisotropy is expected in the spinel layer of the earth's upper mantle as a result of preferred orientation.

Role and control of texture in deep-drawing steels

Since the first scientific paper on the directionality of the mechanical properties of sheet steel was published by Phillips and Dunkle in 1935, much research has been conducted for a basic understanding of this phenomenon and to control the directionality so as to obtain improved properties. Directionality or anisotropy is due to preferred orientation of grains in the fully processed mill-annealed sheet material. Different types of preferred orientation or texture give rise to significant differences in the average plastic anisotropy ratio r, which is a measure of cup drawability. The present paper focuses on the influence of texture on the r-value. The relationship between mechanical anisotropy and crystallography is discussed in detail. Methods of industrial control of texture through suitable modifications in composition and processing parameters are reviewed. The current understanding of the mechanism of texture development in various grades of conventional and new types of deepdrawing steels is also summarized.

Role and control of texture in deep-drawing steels

Since the first scientific paper on the directionality of the mechanical properties of sheet steel was published by Phillips and Dunkle in 1935, much research has been conducted for a basic understanding of this phenomenon and to control the directionality so as to obtain improved properties. Directionality or anisotropy is due to preferred orientation of grains in the fully processed mill-annealed sheet material. Different types of preferred orientation or texture give rise to significant differences in the average plastic anisotropy ratio r, which is a measure of cup drawability. The present paper focuses on the influence of texture on the r-value. The relationship between mechanical anisotropy and crystallography is discussed in detail. Methods of industrial control of texture through suitable modifications in composition and processing parameters are reviewed. The current understanding of the mechanism of texture development in various grades of conventional and new types of deepdrawing steels is also summarized.

Grain Orientation Studies on Polycrystalline Titanium by Means of Electron Channeling Patterns

Preferred orientation textures are known to develop in wrought commercial products, such as rolled sheet or extruded tubing, depending on the material type and on the forming process. Substantial deviations from an arrangement of randomly oriented polycrystalline grains can occur. The amount and type of preferred orientation is customarily determined by x-ray diffraction measurements. That technique averages over a large number (102 to 104) of grains. This paper will describe an investigation of orientation texture in commercial titanium speet on a grain-by-grain basis. Selected area electron channeling patterns (SACP) were obtained from individual grains in the polycrystalline specimens and provided accurate orientation data. Those data were required to explain particular morphological features observed in a recent investigation of the active dissolution of titanium in sulphuric acid.

The Low Temperature Oxidation of Iron

An electron diffraction study of the oxide films formed on abraded iron specimens by heating in air at temperatures ranging from 80° to 260°C has failed to detect structural effects due to a ``critical temperature'' in the neighborhood of 200°C. α-Fe2O3 was found on specimens which were oxidized at any temperature above about 130°C provided the period of oxidation exceeded a minimum value which depends upon the temperature. Thus 1 hour at 180°, 4 hr. at 165°, 13 hr. at 150° or 1000 hr. at 130° are just sufficient to produce an α-Fe2O3 film whose diffraction pattern is well defined. Lower oxidation temperatures or shorter times tend to strengthen the diffraction pattern due to the primary oxide film which is assumed to be γ-Fe2O3 (or Fe3O4) and is detectible immediately after the initial abrasive treatment. The strengthening of the primary oxide pattern is not accompanied by appreciable grain growth, however, and traces of iron are present in the pattern after oxidation periods as long as 1700 hr. at 120°C or below. Based on considerations of the presence of these iron rings it is estimated that the primary oxide film cannot be thicker than about 200A over some portions of the abraded surface. At 193°C and above the development of the first order blue interference color is characterized by the appearance of a new α-Fe2O3 film which is more coarsely crystalline and has a different type of preferred orientation than the first-formed α-Fe2O3 film. It is believed that this secondary film is formed by the outward diffusion of iron through the oxide layer. The axis of preferred orientation of the α-Fe2O3 is always symmetrical about the normal to the surface. This orientation cannot be attributed to pseudomorphism of the oxide crystals on the underlying iron as is the case with the primary oxide.