Radial Texture Research Articles

Selected Physical Properties of Expanded Extrudates from the Blends of Hazelnut Flour-Durum Clear Flour-Rice

Blends of durum clear flour, partially defatted hazelnut flour (PDHF) and rice grit were extruded through a single-screw extruder to form expanded products. The extrudates were analyzed for physical properties, namely radial expansion ratio, colour, and instrumental texture. The radial expansion ratios measured for all the extruded samples ranged between 3–4.5. Breaking strengths of the extrudates varied between 0.387–0.854 N mm−2. The measured values of the colour parameters of extruded blends varied in the range from 48.72–72.24 for lightness (L), 1.95–5.79 for redness (a), and 13.79–15.26 for yellowness (b).

Strong stray fields in magnets with a nonuniform distribution of the magnetization

Stray fields produced by magnets in the form of a cylinder in which the vector of magnetization at each point is directed along the cylinder radius have been calculated. It was assumed that this distribution of magnetization was achieved due to the presence of a radial crystalline texture and the related magnetic anisotropy with a large field of the uniaxial anisotropy HK. It has been shown that the greatest stray fields are reached on the surface of the magnet at points that are located near its axis, and the limiting value of the point field is equal to 4πMSln(a/r). It has been established that in magnets with a radial magnetization the region of localization of strong fields H > 4πMS substantially exceeds that characteristic of the systems of magnets with a uniform magnetization.

Surface metrics: an alternative to patch metrics for the quantification of landscape structure

Modern landscape ecology is based on the patch mosaic paradigm, in which landscapes are conceptualized and analyzed as mosaics of discrete patches. While this model has been widely successful, there are many situations where it is more meaningful to model landscape structure based on continuous rather than discrete spatial heterogeneity. The growing field of surface metrology offers a variety of surface metrics for quantifying landscape gradients, yet these metrics are largely unknown and/or unused by landscape ecologists. In this paper, we describe a suite of surface metrics with potential for landscape ecological application. We assessed the redundancy among metrics and sought to find groups of similarly behaved metrics by examining metric performance across 264 sample landscapes in western Turkey. For comparative purposes and to evaluate the robustness of the observed patterns, we examined 16 different patch mosaic models and 18 different landscape gradient models of landscape structure. Surface metrics were highly redundant, but less so than patch metrics, and consistently aggregated into four cohesive clusters of similarly behaved metrics representing surface roughness, shape of the surface height distribution, and angular and radial surface texture. While the surface roughness metrics have strong analogs among the patch metrics, the other surface components are largely unique to landscape gradients. We contend that the surface properties we identified are nearly universal and have potential to offer new insights into landscape pattern–process relationships.

In situ synthesis of polyamide 6/MWNTs nanocomposites by anionic ring opening polymerization

AbstractIn situ anionic ring opening polymerization is used to prepare monomer casting polyamide 6 (MCPA6)/carbon nanotubes (CNTs) nanocomposites, whereby water is used as auxiliary dispersing agent of hydroxyl functionalized multiwalled carbon nanotubes (MWNTs‐OH) and ε‐caprolactam (CL) monomer. The MWNTs‐OH were dispersed homogenously in MCPA6 matrix when being observed through transmission electron microcopy. The well dispersed MWNTs‐OH existed at the center of many radial texture phases in MCPA6 matrix. Polarizing microscope analysis showed that these radial texture phases were MCPA6 spherulitic crystallities. Differential scanning calorimetry analysis revealed that the crystallization temperature of the MCPA6/MWNTs‐OH nanocomposites had been improved by adding only 0.2 wt % MWNTs‐OH when compared with pure MCPA6. The influence of MWNTs‐OH on the thermal stability of MCPA6 under nitrogen and air environments was also investigated by thermal gravimetric analysis (TGA). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Hydrothermal synthesis of hematite spherules and jarosite: Implications for diagenesis and hematite spherule formation in sulfate outcrops at Meridiani Planum, Mars

We synthesized hematite spherules whose mineralogic, chemical, and crystallographic properties are strikingly similar to those for the hematite-rich spherules in lag deposits on the surface and embedded in outcrops at Meridiani Planum, Mars. The spherules were synthesized in the laboratory along with hydronium jarosite and minor hydronium alunite from Fe-Al-Mg-S-Cl acid-sulfate solutions under hydrothermal conditions. The reaction sequence was (1) precipitation of hydronium jarosite; (2) jarosite dissolution and precipitation of hematite spherules; and (3) precipitation of hydronium alunite upon depletion of hydronium jarosite. The spherules exhibit a radial growth texture with the crystallographic c axis aligned along the radial direction, so that thermal emission spectra have no hematite emissivity minimum at ~390 cm−1. Our experiments show that hydrothermal, acid-sulfate solutions are a pathway for formation of jarosite and the hematite spherules at Meridiani Planum, Mars.

Modelling on-axis microdiffraction to investigate crystallographic texture within high-performance polymer fibres

Radial crystallographic texture in high-performance polymeric fibres is a common structural feature. Quite why such preferred orientation should exist and how it impacts upon the mechanical properties of the fibre is still not fully understood. This study reports the use of a modelling approach to investigate radial texture in the poly(p-phenylene benzobisoxazole) fibre type. The model allows azimuthal scattering profiles to be calculated corresponding to an on-axis microdiffraction geometry. The results show that, in order to model experimental data successfully, an offset is required between theaunit-cell axis and the fibre radial direction. The origin of this offset is tentatively attributed to solvent outflow during coagulation, which aligns the planar molecular chains. Meanwhile, textural differences between different fibre types can be explained by processing differences.

On-axis microbeam wide- and small-angle scattering experiments of a sectioned poly(p-phenylene terephthalamide) fiber

Poly(p-phenylene terephthalamide) fiber sections of ∼15μm length were prepared by a laser microdissection system. On-axis mesh scans by combined small- and wide-angle x-ray scattering using a micron-sized synchrotron radiation beam confirms a radial texture of crystalline domains with orientational order differing for skin, central core and intermediate layers. A skin-core variation in small-angle scattering demonstrates the evolution of fiber structure due to the heat-treatment process.

The permanent magnet systems generating strong stray fields with large localization region

Three systems of permanent magnets, which produce strong magnetic stray fields (SFs) with H> B r=4 πM r were studied in this work. Remarkable feature of the developed systems is localization of the strong fields in large region with linear dimension Δ r comparable to characteristic magnet dimension a. The first system composed of uniformly magnetized magnets generates sufficiently homogeneous strong SFs, which amounts up to 1.5 of magnets induction B r. The second system with nonuniform magnetization is represented by cylindrical and hemispheric magnets their magnetization vector directed at every point along the radius. Such distribution of magnetization is assumed to be the consequence of magnet radial crystal texture resulting in a high uniaxial anisotropy field H K . It is shown that maximal SFs can exist on the flat surface of cylindrical magnet at the distance r from its axis and their limiting value equals to 4 πM r ln(2 a/r). Here, the localization region of the fields is comparable to diameter of cylindrical magnet Δ r≈2 R. As for the hemisphere its SFs are less than corresponding SFs for the cylinder. The third so-called quasi-nonuniform system consists of uniformly magnetized cylindrical sectors their magnetization vector is directed along the sector bisectrix. The strong SFs and their localization region are calculated in details for this case. The passage to radial magnetized cylinder is considered.

Effect of Texture on Anisotropic Creep of Pressurized Zr-2.5Nb Tubes

In this paper we report the stress dependence of the diametral and axial creep rates of cold-worked Zr-2.5Nb tubes with three different combinations of texture and microstructure in biaxial tests at 623K. One type of tube has a predominantly radial texture and it exhibits a high diametral creep rate and negative long term axial creep rate. A second type, with a predominantly transverse texture and a very fine elongated grain structure exhibits an intermediate diametral strain rate and a positive axial strain rate. The third type, with predominantly transverse texture and coarser elongated grain structure exhibits the lowest diametral creep and a positive axial strain rate. The stress exponents for the diametral creep are in the range 5-7, but those for axial creep vary from 0.7 to 7.3. The creep anisotropies were calculated with the polycrystalline model SELFPOLY-7, assuming that slip is the strain producing mechanism. The calculations give qualitative agreement with the experimental results.

EBSP measurements of hydrogenated Zircaloy-2 claddings with stress-relieved and recrystallized annealing conditions

Precipitation behavior of zirconium hydrides and microscopic texture in three kinds of Zircaloy-2 fuel claddings with stress-relieved and recrystallized annealing conditions have been examined by electron backscattering diffraction patterns (EBSP). The microscopic texture data obtained by EBSP were consistent with the macroscopic X-ray data. The zirconium basal plane was observed to have a more radial texture in the case of the recrystallized tube as compared to the stress-relieved tube, even though both tubes had the same tube reduction path. In the recrystallized tubes, the frequency of precipitation and stable growth sites in inter-granular hydrides were about twice as high as that in intra-granular sites. In the stress-relieved tubes, this value was not calculated because of the almost equivalent sizes of hydrides and smaller zirconium matrix grains. The observation frequency of the habit planes of hydrides, which was statistically derived based on pole figure analysis of EBSP between hydrides and surrounding zirconium matrix grains, decreased in the order (0 0 0 1) α ∥{1 1 1} δ ≫ {1 0 1 ¯ 7} α ∥{1 1 1} δ > {1 0 1 ¯ 1} α ∥{1 1 0} δ .

Computational study of the texture formation in mesophase pitch‐based carbon fibres

This paper studies the thermal relaxation phenomena after melt‐extrusion of a rigid discotic uniaxial nematic mesophase pitch using mathematical modelling and computer simulation. The Ericksen and Landau–de Gennes continuum theories are used to investigate the structure development and texture formation across mesophase pitch‐based carbon fibres. The two‐dimensional model captures five types of transverse patterns, which match the commonly observed textures for mesophase pitch‐based carbon fibres. They are: random, zig‐zagged radial, radial, quasi‐onion and onion. These textures represent the various combinations possible from the interplay between structure (i.e. texture) development and cooling during the fibre spinning process. During the thermal relaxation after the cessation of extensional flow the discotic nematic molecules store elastic free energy decays. The distorted nematic molecular profiles reorient to release the stored elastic free energy. The difference in time scales for molecular reorientation and thermal relaxation result in different transverse textures. The rate at which the fibres are cooled is the main factor in controlling the structure development. A slow cooling rate would permit the nematic discotic molecules to reorient to a well‐developed (radial or onion) texture. The random texture is a result of rapid quenching. The numerical results are consistent with published experimental observations.

Classification of wood surface texture based on Gauss-MRF model

The basal theory of Gauss-MRF is expounded and 2–5 order Gauss-MRF models are established. Parameters of the 2–5 order Gauss-MRF models for 300 wood samples’ surface texture are also estimated by using LMS. The data analysis shows that: 1) different texture parameters have a clear scattered distribution, 2) the main direction of texture is the direction represented by the maximum parameter of Gauss-MRF parameters, and 3) for those samples having the same main direction, the finer the texture is, the greater the corresponding parameter is, and the smaller the other parameters are; and the higher the order of Gauss-MRF is, the more clearly the texture is described. On the condition of the second order Gauss-MRF model, parameter B1, B2 of tangential texture are smaller than that of radial texture, while B3 and B4 of tangential texture are greater than that of radial texture. According to the value of separated criterion, the parameter of the fifth order Gauss-MRF is used as feature vector for Hamming neural network classification. As a result, the ratio of correctness reaches 88%.

Highly graphitized carbon fiber prepared from poly (p-phenylene-benzo-bis-oxazole) fiber

Commercially available PBO (poly (p-phenylene-benzo-bis-oxazole)) fibers were carbonized and heat-treated at 3000°C without mechanical treatements. The structure and texture of the 3000°C-treated PBO fibers were investigated by SEM observations and XRD and magnetoresistance measurements. The SEM images of the carbon fibers reveal carbon layers extending clearly along the fiber axis. Two types of textures in the cross sections were found. One is a radial texture and another is that like a palm-leaf fan spreading the carbon layers from a point near the periphery of the cross section. Average misorientation angle of carbon layers along the fiber axis was evaluated to be ±2° from the 002 X-ray diffraction. The interlayer spacing d002 and lattice constant along a-axis ao were 0.3355nm and 0.2461nm, respectively, and the crystallite sizes Lc and La exceeded 100nm. The average crystallite transverse magnetoresistance (Δρ/ρ) cr, and magnetoresistance anisotropy ratios rTL and γTL measured at 77K and in a magnetic field of 1T for the single filaments were 46%, and 0.007 and 0.68, respectively. The 3000°C-treated PBO fiber, therefore, can be characterized as a highly graphitized and highly oriented carbon fiber.

Degradation of the type II collagen network early in the degeneration of cartilage

Type II collagen has been characterized as being present in joint tissues subjected to compression rather than tension. The purposes of this study were to investigate the distribution and ultrastructural changes in the type II collagen fibrillar network in the early stage of degeneration of cartilages. Softened cartilage which represents the early stage of degeneration was obtained from the tibial surfaces of a cow. Normal control cartilage was obtained from the femoral condyles in the same joint. Nomarski light microscopy and transmission electron microscopy (TEM) were performed respectively for structural and ultrastructural studies. Confocal light micrscopy was applied for imaging the staining of collagen type II in normal and softened matrices by immunohistochemical studies. The results demonstrated that in normal cartilage the extracellular matrix was characterized by a fine ”ground-glass-like” amorphous texture. This reflects the fact that individual fibril elements in their repeatedly interconnecting configuration present a fineness of structure that is beyond the limits of optical resolution. The normal matrix observed by TEM was shown to have a pseudo-randam fibrillar architecture. The extracellular matrix in the softened cartilage was characterized by a distinct fibrous texture strongly aligned in the radial direction. This optically resolved structural feature of the softened matrix reflects a tendency for individual collagen flbrils to aggregate into relatively large fibrillar bundles strongly aligned in the radial direction as observed under TEM. The type II collagen-labeled images obtained from the normal matrix exhibited a fine texture. By contrast, staining of the softened matrix exhibited a relatively coarse granularity with a distinctly radial texture in the deeper zones. It was concluded that the degeneration of cartilage begins with degeneration of the extracellular matrix, and the decrease in collagen fibrillar interactions is mainly caused by the loss of cross-linking in type II collagen. This is the first report to correlate ultrastructural changes of the fibrillar network with confocal imaging of the type II collagen distribution in the process of cartilage degeneration.

Orientation and dimensional changes in mesophase pitch-based carbon fibers

The dimensional changes and microstructure evolution of AR-mesophase pitch fibers are reported as a function of heat treatment temperatures (HTTs) that ranged from 300 to 3000 °C. The length measurements for AR fibers indicate that starting from an oxidized state, there is partial relaxation of orientation in the range of 600–900 °C, and the length of the fibers shrinks about 8% relative to that in the stabilized state. Above 900 °C, the fiber length does not decrease; instead, it increases slightly. Thus, fibers heat treated to 2400 °C on average have a length that is bigger than those heat-treated to 900 °C. The small increase in length of fibers heat treated to high temperatures (>900 °C) is likely a consequence of alignment of the graphene layer planes along the fiber axis that can result in an expansion along the longitudinal direction. The small minimum in the length profile at 900 °C corresponds to a small maximum in the misorientation angle of the graphene layer planes measured by wide-angle X-ray diffraction on the fiber bundles. Single filament orientation measurements, using monochromated synchrotron radiation, show a similar maximum misorientation at 600 °C. The fiber microstructure, characterized by scanning electron microscopy, also reveals that the first major change is observed at 900 °C, where a radial texture is observed. At higher HTTs, the development of radial texture is more pronounced and by 2400 °C the graphene-layer planes are seen very clearly.

The size of cryofracture figures in the network of segmented polyurethane elastomers

Cross-linked segmented polyurethanes were broken below brittle - ductile transition and their fracture surfaces were analysed by optical and electron microscopy. Shapes of polygonal appearance were present on the whole surface of the broken sample, and a radial texture with the fracture origin in the middle of polygons was observed. The average distance between cryofracture and origins (L) was measured for each polyurethane studied. The swelling degree was measured and junction-point density calculated. A correlation between L and the junction-point density, v, has been found to exist.

Quiescent crystallization kinetics and morphology of i-PP resins for injection molding. II. Nonisothermal crystallization as a function of molecular weight

The quiescent nonisothermal crystallization kinetics of polypropylene resins was studied as a function of their molecular weight, Mw. Differential scanning calorimetry and polarized light optical microscopy were used to follow this kinetics. It was observed that a modified Hoffman and Lauritzen equation could describe with accuracy their nonisothermal behavior. Also it was found that the polypropylene nonisothermal growth rates, Gn, were similar to their corresponding isothermal rates, G, and also decreased with the increase in Mw. The use of a prior isothermal nucleation procedure allowed to obtain data at higher temperatures and to compare these data at higher cooling rates than the ones found in the literature. The morphology of all the samples revealed a fine and radial spherulitic texture. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1733–1740, 1999

Quiescent crystallization kinetics and morphology of i‐PP resins for injection molding. II. Nonisothermal crystallization as a function of molecular weight

The quiescent nonisothermal crystallization kinetics of polypropylene resins was studied as a function of their molecular weight, Mw. Differential scanning calorimetry and polarized light optical microscopy were used to follow this kinetics. It was observed that a modified Hoffman and Lauritzen equation could describe with accuracy their nonisothermal behavior. Also it was found that the polypropylene nonisothermal growth rates, Gn, were similar to their corresponding isothermal rates, G, and also decreased with the increase in Mw. The use of a prior isothermal nucleation procedure allowed to obtain data at higher temperatures and to compare these data at higher cooling rates than the ones found in the literature. The morphology of all the samples revealed a fine and radial spherulitic texture. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1733–1740, 1999

Texture dependence of the Rayleigh instability in discotic mesophase fibres

Classical theories of liquid crystalline (LC) materials are used to develop a new model that describes the effect of texture on the Rayleigh instability of discotic mesophase cylindrical fibres; these LC fibres arise in the fabrication of carbon fibres by melt spinning of mesophase precursors. The thermodynamic model identifies the new contributions to elastic storage due to the liquid crystal orientational order present in discotic mesophase fibres. The two classical radial and onion textures found in discotic fibres are associated with pure splay and bend elastic modes, respectively. It is found that the radial texture always promotes the Rayleigh fibre instability because droplet formation decreases the bend energy. On the other hand the onion texture contains two competing elastic modes: the splay mode is stabilizing and the bend mode is destabilizing. The net effect on the fragmentation of the onion texture fibre into an array of droplets thus depends on the elastic anisotropy of the mesophase. Surprisingly, when the weighted elastic ratio is equal to one, the Rayleigh instability criteria hold.

Calculating Radial Textures in Bushes* Made of the Alloy Mn-Al-C Upon Upsetting Into a Container

The alloy Mn–Al–C (magnetic τ-phase) has a face-centered tetragonal crystal lattice with the superstructure L10 (Shangurov et al., 1990). The tetragonal crystal axes c (the directions 〈001〉 of easy magnetization) of the grain lattices of a polycrystal permanent magnet having a form of a bush must be preferably oriented along the corresponding bush radius. Such bushes with a pronounced radial texture are used, for example, as stators of micromotors. In the present paper the forming of this radial texture (001) in bushes made of the alloy Mn–Al–C is investigated theoretically. Texture inhomogeneity is taken into account by solving the boundary value problem of plasticity.