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A completely novel 3D dissection approach is taken to re-investigate high-density polyethylene (HDPE) crystallized into periodic architectures in a wide range of Tc . This work first discovers that ring bands present in HDPE are crystallized in a quite wide Tc range (90-120 °C) all within regime-III growth. With further detailed analyses of the top-surface-relief patterns and 3D architectures of HDPE spherulites, this work has fully clarified the periodic morphology packed with alternate ways of single-crystal aggregates in correlation with the optical banding patterns. The proposed assembly mechanism sheds light that the periodic bands are actually composed of a cross-hatch grating structure in that the alternately perpendicular orientations from the ridge to valley bands being related to the interior radial to tangential lamellae. Such grating architectures in the interiors of HDPE can be viewed as a mimicry resembling shish-kebab lamellae self-aligned by Archimedean spiral-spins from the nucleus center.

Four β-nucleated polypropylene samples with increasing die draw ratio (DDR) were prepared to modify lamellae arrangement. The DSC, SEM, and 2D-XRD results show that all four cast films had similar crystallinity, high contents of β-crystal but lowering stability of β-lamellae with ascending DDR. Meanwhile, the anisotropy of β-lamellae distribution strengthens gently and the stacked lamellae structure perpendicular to the machine direction (MD) predominates dramatically. Tensile testing at 25 °C and 90 °C were conducted along MD and transverse direction (TD), respectively. The markedly expanding difference of deformation indicates the anisotropy highlighted significantly. Additionally, when the samples stretched along MD, a more homogeneous deformation occurs with ascending anisotropy, which is completely opposite to the β-lamellae stability. But samples deformed more heterogeneous when stretched along TD. The characterization of morphological evolutions during stretching shows that the stacked lamellae debonds uniformly and abundant microvoids formed when the sample stretched along MD with higher anisotropy, resulting in evenly dispersion of stress, consequently making a more uniform distribution of defects and a better isotropic deformation. Moreover, the microfibrils and defects distributed uniformly within higher orientation sample after longitudinal stretching stretched along MD, leading to the dramatic improvement of pore size distribution of the membrane after biaxial stretching. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

Dendritic BaTiO3 ceramic powders (d-BT) were prepared by hydrothermal method in order to improve the dielectric properties of d-BT/P(VDF-TrFE) composites, in which, KOH was used as the branch-directing agent. The effect of hydrothermal time on the branch length of d-BT particle was mainly studied. The results showed that 1.0-2.5 μm d-BT particles were obtained after hydrothermal treating for 12 hours. The particle was composed of two kinds of branches, one was primary branch with about 800 nm in length and another with150-250 nm. A d-BT/P(VDF-TrFE) composites were formed by solution casting, in which d-BT powders as dielectric fillers and the composites exhibited high-energy storage performance. Its maximum energy density reached to 9.78 J/cm3, twice as compared with pure P(VDF-TrFE). The branches of d-BT particles may act as key roles when the composites existed in electric field. Some branches perpendicular to the external electric field provided the increase in the breakdown strength and others parallel to the external electric field brought the enhancement of the dielectric constant, which simultaneously resulted in high energy density of the composites.

In the present work, the dislocation structure evolution around and underneath the spherical indentations in (001) oriented single crystalline strontium titanate (STO) was revealed by using an etch-pit technique and molecular dynamics (MD) simulations. The 3D defect structure at various length scales and subsurface depths was resolved with the help of a sequential polishing, etching, and imaging technique. This analysis, combined with load–displacement data, shows that the incipient plasticity (manifested as sudden indenter displacement bursts) is strongly influenced by preexisting dislocations. In the early stage of plastic deformation, the dislocation pile-ups are all aligned in 〈100〉 directions, lying on {110}45 planes, inclined at 45° to the (001) surface. At higher mean contact pressure and larger indentation depth, however, dislocation pile-ups along 〈110〉 directions appear, lying on {110}90 planes, perpendicular to the (100) surface. MD simulations confirm the glide plane nature and provide further insights into the dislocation formation mechanisms by tracing the evolution of the complete dislocation line network as function of indentation depth.

Large tilt angle (LTA) implantation has been employed in Si manufacturing processes in many applications, such as lightly doped drain and halo implant. The depth profile of boron ions usually consists of only single peak at incident angle of 0° with respect to the perpendicular of the silicon surface. However, an abnormal dual-peak profile was observed at LTA (>40°) with incident energy of 160 keV. By using a Monte Carlo method to simulate the ion implant process, it was found that the projected range of boron ions agrees completely with the formation of the first peak position that is shallower in depth, while the cause for the second peak that corresponds with a depth much deeper in the Si substrate was unknown. During the simulation, it was also found that when the tilt angle was increased, the sputtering yields and Si displacements increased significantly, and this phenomenon indicates that during LTA implantation, Si damage may not be negligible anymore. The Si damage effect that was as due to either low Si density or transient Si displacement in the simulation could have led to partial incident boron ions penetrating much deeper into the Si substrate and thus, caused the emergence of the second peak. Copyright © 2016 John Wiley & Sons, Ltd.

The molecular anisotropy that is developed in microscale, centrifugally spun atactic-polystyrene fibers prepared from the solution state is examined and comparisons are made to electrospun fibers. Utilizing small angle neutron scattering, a ratio of the radius of gyration parallel to-/perpendicular to- the fiber axis is measured and a model of chain anisotropy development in the centrifugal spinning process is described.

Intriguing field emission microscopy (FEM) images reflecting subnanometer-sized structures of emitting sites and/or electronic orbitals have been observed from graphene edges. Graphene emitters with free edges (i.e. open edges) show a striped pattern (dubbed as a ‘lip pattern’) consisting of an array of streaked spots (or oval-shaped spots); the direction of striation is perpendicular to the graphene sheet, and each stripe is divided into two wings by a central dark band running parallel to the graphene sheet. The dark band may be due to the distractive interference of electrons emitted from π orbitals with a phase difference of π on either side of the graphene. From the magnification calibration using FEM images of an aluminum cluster with atomic resolution, the spacing of the streaked spots is found to be close to the distance between adjacent carbon atoms aligned along the zigzag and armchair edges. These observations suggest that the lip pattern reflects the symmetry of π states strongly delocalized at edge atoms. Copyright © 2016 John Wiley & Sons, Ltd.

The effect of molecular weight on the molecular aggregation structure of polymers bearing a pendant perylenediimide (PDI) side chain, designated PAc12PDI, was investigated using synchrotron radiation X-ray diffraction measurements. It was found that depending on molecular weight, either the main chain axis or the side chain axis behaves as the longitudinal axis in fiber samples and was aligned parallel to the fiber axis. A similar phenomenon is present in thin film samples, but was complicated by the additional influence of the interfacial free energy of the side chain group. Even in the case of the polymer with lower molecular weight, the face plane of PDI was found to show both parallel and perpendicular orientations to the substrate (i.e., flat-on and edge-on orientations). On the other hand, if the length of the main chain is sufficiently long with respect to the length of the side chain, the face plane of PDI was oriented perpendicular to the substrate, leading to an edge-on orientation in the thin film. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2275–2283

The boundaries of 1:2 ordered domains in Ba[(Co, Zn, Mg)1/3Nb2/3]O3 perovskite ceramics are comprehensively studied by high-resolution transmission electron microscopy (HRTEM) on the base of atomic position simulation. The atomic configurations for four types of twin boundaries are determined. A-type and B-type boundary, which lie along (001)c and (110)c planes, respectively, are conservative. C-type boundary parallels to (111)c plane, while Г-type boundary is perpendicular to (111)c plane. At C-type and Г-type boundary, atomic intersection leads to a buffer layer, among which the B-site cations are generally disordered. The width of Г-type boundary is larger than that of C-type boundary, so is the perturbation to the system. The energy of four types of twin boundaries is proved to be “A-type & B-type < C-type < Г-type” according to the magnitude of the destabilization to the system. Single antiphase boundary (APB) is considered to be nonconservative. However, when combined with conservative twin boundary, an extra ordered structure with a periodicity of 1.24 nm along [001]c direction and a periodicity of 0.87 nm along [110]c direction forms. The boundary regions are indeed stabilized by the new superlattice.

authoren Abstractauthoren Structuring materials is one mechanism to influence the thermal conductivity and thus thermoelectric efficiency. In order to investigate the scattering of phonons in multilayer structures we developed a beam matching technique, which is based on the concept of individual phonons and their scattering at interfaces. One of the major goals is to efficiently determine the complex band structure of the bulk materials. The complex band structure is determined using selected k-points on a triangulated grid in the complex plane of wave vectors perpendicular to the interface. Matching the phonon modes at an interface is translated to a singular value problem. Its null-vectors provide the coupling coefficients of the phonon modes across the interface. Besides giving explicit access to the modes as they scatter at the interface, the technique provides the transfer matrices, that provide the transmission coefficient of any multilayer structure. The transmission coefficient, in turn, yields the phononic thermal conductance for coherent transport. The knowledge of the matched phonons forms the basis of investigating incoherent transport under the influence of phonon–phonon or impurity scattering.

A subsea flexible pipe containing isotropic poly(vinylidene fluoride) (PVDF) layers is subjected to rapid decompression after being put in pressurized equilibrium with a fluid containing supercritical CO2. The PVDF layers have flowed radially into gaps of adjacent metallic coils forming whitened noses. Microbeam small-angle X-Ray scattering (SAXS) scanning reveals a considerable morphological gradient in the polymer layers. PVDF layers (inner: wear, outer: barrier) in two zones (undamaged and damaged) are scanned. Far from noses and damage zone, the samples are isotropic without voids. Their morphological parameters are determined and compared to virgin material. Approaching the noses, the structure turns into highly oriented microfibrils perpendicular to the local flow into the gaps. Here, voids extend parallel to the microfibrils. At edges of the metallic structure, they turn more perpendicular to the layer. Crystallite orientation extends out to both sides of the whitened nose regions, but in the undamaged samples, tilting of the orientation direction and void-formation are restricted to the white regions: successive mechanisms of cold drawing are mapped into space. Under the damaged spot, voids and crystallite orientation extend through the entire layer. POLYM. ENG. SCI., 2015. © 2015 Society of Plastics Engineers

Silicon nitride (Si3N4) materials with preferentially aligned β-Si3N4 grains were tribologically characterized with respect to their possible application in a high-pressure gasoline pump. Tribological tests were performed under oscillating sliding conditions lubricated with isooctane as a substitute for gasoline using Si3N4 counterbodies. Performance in terms of wear of the aligned materials surpassed that of nonaligned reference Si3N4, as well as that of self-mated silicon carbide, zirconia, alumina, and a steel sliding pair. The plane perpendicular to the extruding direction and parallel to the hot-pressing axis was the most wear resistant.

International audience; Mesh network structures are visualized by peak force tapping atomic force microscopy on cross-linked poly(dimethylsiloxane) (PDMS) at the nanometer length scale. The images directly capture network mesh structures with mesh diameter values, from 10 to 16 nm at the free surface of PDMS. Perpendicular to the free surface, in cross-sectional areas exposed by cryo-fracturing, similar mesh structures are observed. When exposed to uniaxial stress, the circular mesh features become elongated, showing network deformation at the nanoscale, as a result of mechanical stress. Following Soxhlet solvent extraction the mesh-like appearance remains unchanged, but mesh diameter values decrease, which are attributed to the removal of non-crosslinked chains and silica filler.

We have investigated structural, optical, and electrical properties of MgZnO:(Al/Ga) thin films in dependence on Mg and Al/Ga concentrations. For this purpose, thin films with two perpendicular, lateral composition gradients, i.e., the Mg composition is varied in one direction whereas the Al/Ga concentration is varied in a perpendicular direction were grown at by pulsed-laser deposition (PLD) using a threefold segmented PLD target and 2-inch in diameter c-plane sapphire substrates. It has been found that compensation by intrinsic acceptors limits efficient doping to dopant concentrations of about . Further, the electrical data suggests, that the compensating defect is doubly chargeable hinting to the zinc vacancy as microscopic origin. Increasing the dopant concentration above leads to a degradation of electrical and structural properties.

Three dimensional self-consistent field theoretic simulations have been performed to determine the equilibrium morphologies formed by linear ABC triblock polymer melts confined between two parallel plates that favor the middle block. Our primary goal is to elucidate the conditions under which the perpendicular lamella is stabilized, since this morphology plays a central role in many nanotechnology applications. Key factors, namely, the chain architecture, surface energy and the mismatch between the film thickness d and the bulk lamella period, L0, determine the final morphologies, e.g., perpendicular and parallel lamella, perforated lamella and wet substrate with parallel cylinders in the core, have been identified. Overall, our findings are fully consistent with the results of limited experimental studies focused on morphology development in thin films of triblock polymer melts. Finally, we have clearly demonstrated that ABC triblocks hold technological advantages over diblocks for nano-lithographic fabrications.

Nextel™ 610 alumina fibers were heat-treated at 1100°C–1500°C for 1–100 h in air. Grain size distributions (GSDs) and grain orientation distributions (ODs) with respect to the fiber axis were characterized by analysis of TEM images from longitudinal fiber sections. The 2-D GSDs and ODs were characterized as ellipses. 3-D GSDs and ODs were calculated by fitting distributions of oriented oblate ellipsoids to 2-D GSDs and ODs formed by ellipsoid–section-plane intersections. The standard deviations (SDs) of log-normal GSDs consistently increased with grain size, which is not diagnostic of normal grain growth. The grain aspect ratio (α) and the tendency of the short grain axis to orient perpendicular to the fiber axis also increased with grain size, resulting in more textured fibers at larger grain sizes. Average 3-D grain sizes were larger than 2-D sizes for GSDs with small SDs, but smaller for GSDs with large SDs because of under sampling of small grains. 3-D grain growth kinetics had the same 815 kJ/mol activation energy as that found by 2-D analysis, but the grain growth exponent m of 6.0 was larger and the pre-exponential factor much smaller. Expressions for 3-D log-normal GSDs as a function of heat treatment temperature and time were determined. α-distributions and ODs were determined as a function of grain size. Methods for determining 3-D GSDs are discussed.

We present our recent results from constant temperature-pressure (NPT) molecular dynamics (MD) simulations of a bead-spring copolymer model, in which the polymer is confined between two crystalline substrates. Our goal was to study the combined effect of the polymer crosslinking density and the degree of confinement on the glass-transition temperature and the equilibrium structure of the films. In the direction perpendicular to the substrates, the polymer chains are ordered in layers of increasing density towards the substrates, for all crosslinking densities and the degrees of confinement. In the direction parallel to the substrates, the polymer films display an amorphous structure, just like in the bulk. The glass-transition temperature increases with confinement and crosslinking density, with the former having a large effect compared to the later. POLYM. COMPOS., 36:1012–1019, 2015. © 2015 Society of Plastics Engineers

Aligned, uniform fiber matrixes are highly desirable in numerous engineering and physical science applications. Here, modified electrospinning (ES) deposition substrates (paired and in parallel) are explored to achieve rapid preparation of multiple topographies. Three ES substrates with well-defined geometries (rectangular, concave, and E-shaped) were investigated (arranged in parallel) for their impact on fiber size, morphology, orientation, and cell behavior. The results indicate fiber alignment and orientation can be improved and modulated based on the substrate geometry. In addition, altering the interdistance space between various parallel substrates has a clear impact on fiber diameter size and alignment (random, aligned, and perpendicular orientation). Electric field simulations based on substrate geometries show greater probable regions of aligned electric field vectors and distribution, which indicates the most likely deposition attributes of electrospun PCL fibers. Fibrous PCL membranes were biocompatible, and cell growth and guidance were along the fiber path, with evidence of branching at intersecting fibers for multiaxial fibrous topographies. These findings show that the substrate geometry can be optimized to effectively assemble multiaxial layered and well-aligned fibers in a controlled fashion, which is ideal to support several application developments dependent on fiber topography, integrity, and morphology. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44823.

Two kinds of -oriented β-SiC films with pyramidlike and needlelike morphologies were obtained by laser chemical vapor deposition. Their mean grain size ( ) as a function of the distance from substrate (h) follows power laws of ∝ h0.62 and ∝ h0.71, respectively. The planar defects in pyramidlike films were perpendicular to the growth direction, whereas those in needlelike β-SiC films inclined to growth direction, which can be annihilated with meeting of anti-couple defect. This self-vanish of defects would develop a new approach to fabricate high quality -oriented β-SiC.

Shave-off depth profiling uses a Ga focused ion beam micro-machining process to provide highly precise depth profiles with nanometer-scale resolution. This method is a very unique process for acquiring a depth profile using the shave-off scan mode, in which the primary ion beam perpendicular to the direction of depth irradiates the sample. In our previous study, we confirmed by molecular dynamics simulation that the shave-off scan mode has a low mixing effect compared with the conventional scan mode, which uses the normal incident angle. However, the current understanding of measurement using the shave-off scan mode is insufficient. In this study, in order to estimate the sample damage in the shave-off scan mode, we investigated the degree of mixing effects after the primary ion bombardment under shave-off conditions using atom probe tomography. To evaluate the mixing effects, the intermixing of silicon isotope multilayers induced by ion beam irradiation was investigated. The depth of the damage from the sample surface caused by Ga focused ion beams was analyzed for both the shave-off scan mode and the conventional scan mode using the normal incident angle. Results showed that the shave-off scan mode has a significantly smaller mixing effect thanthe conventionalscanmode. Inaddition, results showed that the attenuations of the damage and the Ga concentration exhibited almost the same tendency. Copyright © 2014 John Wiley & Sons, Ltd.

The impact of dislocations on surface topology as well as on quantum well emission in c-plane, semipolar, and nonpolar InGaN/GaN heterostructures is being analyzed by micro-photoluminescence and white-light-interferometry. V-pits with (101) and (10) side facets are identified in a (102) semipolar heterostructure. Hillocks formed by spiral growth around screw dislocations change from hexagonal to triangular to rectangular shape in polar, semipolar, and nonpolar heterostructures, respectively, reflecting the symmetry of the individual surface. The emission in semipolar quantum wells, grown homoepitaxially on bulk GaN substrates, show dark stripes aligned with misfit dislocations. For (112) and (201) orientation, these dark stripes are perpendicular and parallel, respectively, to surface striation.

Block copolymer thin films are highly versatile and accessible materials capable of producing nanofeatures in the size regime of a few to hundreds of nanometers by a simple spin-coating-and-anneal process. Unfortunately, this simple protocol usually leads to parallel microdomains, which limits the applicability of such nanofeatures. A great deal of effort has been put into achieving perpendicular microdomains, but those that incorporate thermal annealing are arguably the most practical and reproducible in the lab and industry. This review discusses the recent ongoing efforts on various thermal approaches to achieving perpendicular microdomains in order to provide the readers with a toolbox to work with.

SiC fiber-bonded ceramics, SA-Tyrannohex®, (SA-THX) with perpendicular and parallel fiber orientations were brazed using Ag-, Ni- and Pd-base brazes, and four Si–X (X: Ti, Cr, Y, Ta) eutectics. Outcomes were variable, ranging from bonded joints through partially bonded to un-bonded joints. Prominent Ti- and Si-rich interfaces developed with Cusil-ABA, Ticusil, and Copper-ABA and Ni- and Si-rich layers with MBF-20. Stress rupture tests at 650 and 750°C on Cusil-ABA-bonded joints revealed a temperature-dependent behavior for the perpendicular joints but not for the parallel joints with failure occurring at brazed interface. Higher-use temperatures can be targeted with eutectic Si–Ti and Si–Cr alloys.

Thin binary blends of poly(styrene-b-methyl methacrylate) (PS-PMMA) block copolymers in films where the lamellar thickness of one domain is controlled while preserving the thickness of the other domain were demonstrated without microphase separation. One of the block copolymers used here was short and symmetric, and the other was long and asymmetric; the molecular weights of the PMMA block chains in the constituents were similar. A random copolymer brush was introduced and film thickness and composition of brush were adjusted to induce perpendicular orientation in thin film. As the blend composition of the long asymmetric block copolymer increased, the PS lamellar thickness increased from 15.8 to 25.1 nm, whereas the PMMA lamellar thickness remained constant at approximately 14 nm (the thickness decreased slightly from 14.0 to 13.3 nm). The domain spacing behavior in thin film was consistent in the bulk. These results were compared with the Birshtein, Zhulina, and Lyatskaya model and the theories for pure block copolymers in the strong segregation limit and in the intermediate segregation regime. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1393–1399

The structural evolution in poly(styrene-b-butadiene) (P(S-b-B)) diblock copolymer thin films during solvent vapor treatment is investigated in situ using time-resolved grazing-incidence small-angle X-ray scattering (GISAXS). Using incident angles above and below the polymer critical angle, structural changes near the film surface and in the entire film are distinguished. The swelling of the film is one-dimensional along the normal of the substrate. During swelling, the initially perpendicular lamellae tilt within the film to be able to shrink. In contrast, at the film surface, the lamellae stay perpendicular, and eventually vanish at the expense of a thin PB wetting layer. During the subsequent drying, the perpendicular lamellae reappear at the surface, and finally, PS blocks protrude. By modeling, the time-dependent height of the protrusions can be quantitatively extracted.

Summary The effect of temperature and type of solvent on the microdomain orientation during solvent-annealing of block copolymer ultrathin films on silicon substrates was investigated using asymmetric polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer. When the solvent-annealing was performed with THF at 20°C, the ultrathin film exhibited a mixed orientation of cylinders parallel and perpendicular to the substrate while at 25°C only parallel cylinders were observed by AFM. The solvent annealing with acetone gave a dot pattern at 20°C and a line pattern at 25°C. On the other hand, in the case of solvent-annealing with toluene perpendicular cylinders were observed at 25°C while at 20°C the morphology was not clear. The orientation and morphology of microdomains as well as the kinetics in PS-b-P2VP ultrathin films on solvent-annealing is significantly affected by temperature and type of solvent. By controlling temperature and selecting the solvent, perpendicular cylinders can be formed predominantly on the substrates.

Summary We applied the microbeam two-dimensional small-angle X-ray scattering (2d-µSAXS) technique in order to characterize orientation of polystyrene (PS) microdomains as a function of the distance from the free surface of a sample sheet down to the surface facing to the substrate, for depth profiling for spontaneous perpendicular orientation of PS cylinders in the matrix of polyethylenebutylene (PEB) in a PS-b-PEB-b-PS triblock copolymer thick sheet as thick as ∼0.5 mm. It has been revealed that near the free surface the cylinders were randomly oriented down to ∼70 µm in depth. Although this might indicate that the surface effect, which preferentially dictates cylinders to be oriented parallel to the surface, can propagate for such a long distance, 70 µm is unusually huge as compared to the general knowledge of the surface effect propagating at most for 1 µm. Experimentally examining further, we finally conclude that the 2d-µSAXS depth profiling overestimates the surface effect. This unfavorable conclusion may be ascribed to surface roughness of the sample sheet subjected to the measurement, and in order to obtain a good result a big effort is required to prepare the surface as flat as possible.

To clarify the mechanism of the deformation and fracture in a low-velocity impact test on the isotactic polypropylene (i-PP) sheet made by injection molding, the change of the style of fracture and the form of deformation was examined while changing the speed of the striker in a low-velocity impact test. In the injection molding sheet, an oriented skin layer of some thickness is formed on the surface of the sample sheet. By the stress perpendicular to the orientation direction of the skin layer, crazes were formed easily in parallel with the orientation direction in this layer, and cracks were formed from there. Because these cracks bring the sample sheet a strong restraint of strain, a high stress concentration occurs at the end of this crack even if the formation of the oriented layer is limited on the surface of the sample sheet only, and the low-velocity impact test leads the sample sheet to a brittle fracture. As a result, the injection molding sheet that forms oriented structure on its surface causes the ductility-brittleness transform at a lower velocity of deformation compared with the nonoriented sheet. POLYM. ENG. SCI., 53:2659–2665, 2013. © 2013 Society of Plastics Engineers

A series of samples consisting of alternating stripes of ZnO grown by molecular-beam epitaxy (MBE) and radio-frequency (rf) sputtered Ga-doped ZnO stripes was laterally microstructured with a self-aligned pattern transfer method. We measured as a function of temperature the Seebeck coefficient S and the electrical resistivity ρ in-plane of the samples with the transport direction perpendicular to the stripe direction. Throughout the series the bar width and hence the number of interfaces was kept constant, but the interface profile was varied yielding different interface lengths and geometries. The dependence of S, ρ and the power factor S2/ρ on the interface length at room temperature were simulated using an empirical network model and it was demonstrated that the macroscopic transport coefficients are very sensitive to the interface region and that even this rather simple modelling yields useful information about the interface region.

For a multitude of high-end applications such as photovoltaics and membranes for fuel cells or gas separation, creating large internal surfaces via fractal structuring during polymer processing can result in unique possibilities for enhancing performance. Structuring is possible even in processing techniques like injection molding. Inspired by microfluidic practice, an optimized splitting and recombining static mixer is realized on the parting surface of a mold. Different geometries are used to multiply, rotate, and add stratified structures. After the obvious structuring of a number of parallel layers, attention is focused on layers perpendicular to the product surface. A combination of the two allows complex hierarchical fractal structures to be obtained. A first demonstration of its feasibility is reported.

The impact of processing-induced chain orientation on the sliding wear behaviour of ultrahigh molecular weight polyethylene (UHMWPE) was investigated. The orientation of the molecular network of UHMWPE was done by means of uniaxial tension up to different residual strains. We found that high residual strain levels (higher than 0.45) enabled the sliding dissipated energy of UHMWPE to be decreased in dry conditions. In particular, oriented UHMWPE with a residual strain of 0.85 exhibited, at 500 000 sliding cycles in dry conditions, a decrease in volumetric wear loss by a factor of 3.3 and 19.4 compared with the reference UHMWPE tested in directions parallel and perpendicular to the chain direction, respectively. It is argued that oriented UHMWPE exhibits less adhesion during interfacial wear than the reference material, and hence orientation of UHMWPE bulk may be an alternative treatment to crosslinking for dry sliding conditions. In the case of sliding testing conducted in Ringer’s solution, the benefit of the initial chain orientation was quite weak due to a lubrication effect of the solution that markedly limited the effect of chain orientation on the sliding behaviour. c � 2012 Society of Chemical Industry

Perpendicular exchange bias (PEB) between [Co 0.3 nm/Pd 0.8 nm]5 multilayers and IrMn antiferromagnetic (AFM) layer is studied as functions of thickness of the interface layer and the AFM layer. It is found that increasing the thickness of a CoFe interface layer up to 2.1 nm could effectively improve the PEB. The achieved PEB field (Hbias) is more than 500 Oe. On the other hand, the coercivity (Hc) exhibits an opposite trend as a function of CoFe interface layer thickness, which might promote the integration of PEB structure with the perpendicular magnetic memory stack. It is also found that PEB is sensitive to the thickness of the AFM layer. The thickness window is only around 2 nm to achieve the largest Hbias. Moreover, for a very thin IrMn layer, a ferromagnetic nature is observed at low magnetic fields, which is likely owing to the net spins at the surface that might have been magnetized by the CoFe interface layer.

The effect of accumulated deformation and deformation routes in the course of equal-channel multiple angular extrusion (ECMAE) on physical and mechanical properties of polyethylene (PE) differed in molecular mass (MM) has been studied. As deformation routes, route C (shear planes are parallel, and the simple shear direction of every deformation zone is changed through 180°) and route E (shear planes are turned through ±45° around the extrusion axis and the normal to the axis, and simple shear direction is changed through 180° or ±90° with respect to the deformation zone) were selected. It has been shown that ECMAE provides the increase of microhardness H, modulus of elasticity E, and tensile strength σT up to 4.5 times with strain at break eb staying practically at the level of eb of the initial material. The value of the effects achieved depends on MM, accumulated deformation and the selected deformation route. The best set of physical and mechanical characteristics was observed in the case of route E. The observed effects are related to the formation of a special orientation order and increased degree of crystallinity of extrudates. According to SEM data, route C results in mostly uniaxial orientation of macrofibrils at an angle of 35° to the direction of extrusion, and formation of a part of tie fibrils and macrofibrils oriented perpendicularly to the main orientation. The route E produces biaxial orientation of macrofibrils. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Chemiresistive polymer composite ribbons that function as chemical detectors were produced from solution-cast films of polymers and carbon composites. An array with multiple polymer sensor threads was exposed to dimethyl methyl phosphonate, a nerve agent simulant, and different interferents in the vapor phase. Principal component analysis was used to differentiate between the analytes. The response of the ribbon sensors as a function of the carbon composite and the host polymer source was investigated. The freestanding threads/sensors were mounted into a cell perpendicular to the gas flow to provide little pressure drop and were imbedded into fabrics to provide an example of a small, low-cost, wearable chemical sensor. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Particle-based simulations using the discrete element method are applied for the sintering of thin ceramic stripes that are constrained by a rigid substrate. The inhibition of lateral particle movement in vicinity of the substrate leads to a preferred shrinkage direction perpendicular to the substrate, which causes shape distortion as well as delamination of the stripe at the interface edges. Multiple processing parameters are varied in simulations to analyze their influence on the mentioned effects. The amount of particle rearrangement and the height to width aspect ratio of the cross-section are identified to be factors that determine the level of shape distortion and edge delamination. The simulation results are compared with measurements of stripes produced by soft micromolding in capillaries. Good accordance is observed regarding parameters like axial and lateral shrinkage or delamination angle.

To understand the toughness enhancement of β-nucleated isotactic polypropylene (iPP) in comparison with iPP, the differences in the micro-deformation mechanisms between the neat iPP and β-nucleated iPP were visualized using the confocal laser scanning microscopy (CLSM). Structure of the α- and β-spherulites situated close to the tip of the sharp starter crack has been investigated during tensile deformation in the viewing field of the CLSM. In the α-spherulite of the neat iPP, highly localized inter- and intra-spherulitic micro-shear bands have been observed. In the β-nucleated iPP, relatively uniform distribution of diffuse shear bands has been observed in the β-phase, while the α-phase remained relatively undeformed exhibiting only narrow intra-spherulitic shear bands in the direction perpendicular to the loading direction. Delocalization of plastic deformation into diffuse shear bands in β-nucleated iPP can explain its enhanced crack resistance compared with the neat iPP exhibiting highly localized shear banding. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

A new LTCC (low-temperature cofired ceramic) system containing Al2O3 platelets instead of conventional Al2O3 particles as a filler material was investigated. As the Al2O3 platelets were arranged parallel to the casting direction during tape casting and had preferred orientation in the green tape, the linear shrinkage of the green body took place mainly in the direction perpendicular to the platelet planes with just a little shrinkage in the horizontal without any external force during sintering. The intended anisotropic shrinkage of the new LTCC system made the constrained sintering of 10-mm-thick ceramic body possible, which decreased the sintering shrinkage tolerance in the x–y directions of the 10-mm-thick ceramic body from 0.5% to 0.05%. The new LTCC system showed equivalent electrical properties and remarkable physical properties in comparison with a conventional LTCC system.

Slow trap charge repositioning processes between the field perpendicular boundaries and field parallel boundaries are put forward to explain the nonlinear to linear change of the I (V) character of CaCu3Ti4O12 (CCTO). Large polarization variations, which obviously behave as a permittivity peak were found in the charge repositioning process. The anisotropic multipole polarization that occurs in the charge repositioning process is suggested to be the reason for the enormous polarization variation and also could be the origin of colossal dielectric constant of CCTO.

Bundles of carbon fibers were successfully coated with alumina by atomic layer deposition via sequential exposures to trimethylaluminum and water at 77°C. Fibers were not damaged by this procedure. Scanning electron microscopy (SEM) images revealed that individual filaments were coated separately with a smooth layer; no bridging of fibers was observed. Transmission electron microscopy (TEM) and SEM images indicate that the coating was conformal and adhered well to the fiber surface. The average deposition rate was 0.25±0.02 nm/cycle, calculated from SEM images obtained at various positions of the fibers and of fibers coated with various numbers of cycles. In addition to image analysis, the coating thickness was as well estimated from the elemental composition of selected parts of a fiber bundle that was coated by 450 cycles. Along the fiber axis, the weight fraction of aluminum of the coated fibers varied from 5.3 to 6.5 wt% and perpendicular to the bundle axis it varied from 4.8 to 7.4 wt%. This translates into a variation of the estimated coating thickness along the fiber from 166 to 126 nm and perpendicular to it from 114 to 183 nm. One can estimate independently an average coating thickness from the analysis of SEM images of this specific bundle of 126 nm. The alumina coating improved oxidation resistance of the carbon fiber significantly. The oxidation onset temperature was 600°C for fibers coated with a 30-nm-thick layer of alumina and increased gradually with increasing coating thickness up to 660°C at a thickness of 120 nm. On the other hand, uncoated fibers started to oxidize already at 300°C.

The polydomain–monodomain (PM) transformation takes place when a polydomain of a smectic-C main-chain liquid-crystalline elastomer (SmC MCLCE) is uniaxially stretched. We present results based on a combination of mechanical and X-ray experiments which show how the domains initially rearrange to finally form a perfect conical layer distribution (monodomain) when the sample is fully stretched. The rearrangement and orientational process of the domains is quantified and compared to the parallel and perpendicular uniaxial stress– strain deformations of a monodomain sample. The stress–strain behaviour of the polydomain lays between the uniaxial deformations, parallel and perpendicular to the director, of the monodomain sample.

The effect of applied thermal history on the rheological properties in a molten state and the electric properties in a solid state is evaluated using mechanically blended samples composed of polycarbonate and multiwalled carbon nanotubes (MWNTs). It is found that MWNTs orient perpendicular to the applied compression direction owing to the squeeze flow at compression molding, which is prominent for the sample compressed at low temperature. The orientation of MWNTs reduces the interparticle contacts between MWNTs and thus decreases the electrical conductivity. Post-processing annealing procedure at high temperature, however, leads to random orientation due to Brownian motion and then improves the electrical conductivity. The transition from an electrical insulator to a conductor by the redistribution process, which is called dynamic percolation, is well detected by the rheological measurements. POLYM. COMPOS., 32:97-102, 2011. © 2010 Society of Plastics Engineers.

The anisotropic mechanical response of oriented polymer glasses is studied through simulations with a coarse-grained model. Systems are first oriented by uniaxial compression or tension along an axis. Then the mechanical response to subsequent deformation along the same axis or along a perpendicular axis is measured. As in experiments, the flow stress and strain hardening modulus are both larger when deformation increases the degree of molecular orientation produced by prestrain, and smaller when deformation reduces the degree of orientation. All stress curves for parallel prestrains collapse when plotted against either the total integrated strain or the degree of molecular orientation. Stress curves for perpendicular prestrains can also be collapsed. The stress depends on the degree of strain or molecular orientation along the final deformation axis and is independent of the degree of orientation in the perpendicular plane.

The effects of magnetic field direction on γ-fiber texture evolution in as-annealed interstitial-free (IF) steel sheet were investigated by means of X-ray diffraction ODF analysis. Specimens cut from cold-rolled IF steel sheets were placed at the center of a 12-T magnetic field, tilted by different angles to the magnetic field direction respectively, and annealed at 750 °C for 30 min. The results show that altering the specimen orientation to the magnetic field direction during annealing does not change the final annealing textures. The average intensity of the γ-fiber texture of specimens annealed under the magnetic field is higher compared to conventionally annealed specimens. The intensity of the main γ-fiber texture components presents a similar periodic variation with respect to the specimen orientation to the magnetic field, i.e., it is weakened as the tilt angle increases from 0°, and subsequently strengthened to a maximum value at 45°, and then weakened again as the tilt angle continues to increase. When the magnetic field is applied in the direction perpendicular to the specimen's rolling plane, the intensity of the main γ-fiber texture components of specimens annealed in the magnetic field is close to that of the specimen annealed without field. This phenomenon might be attributed to the demagnetic effect.

A poly(ester urethane) multiblock copolymer containing poly(epsilon-caprolactone) glycol (PCL) soft segments gives ring-banded spherulite as crystallized from its melted film. Analysis based on polarized light microscopy and atomic force microcopy revealed that the ring-banded structures consist of alternate convex and concave bands as a consequence of rhythmic growth. These convex and concave bands, which are composed of flat-on and edge-on lamellae, show layered terrace-like and fibrillar morphology, respectively. The chain orientation and composition distribution in the ring-banded spherulites were further investigated using FTIR imaging. The convex bands are mainly PCL-rich domains with perpendicular chain orientation to the substrate, and the concave bands are urethane-rich domains, where the PCL chains are perpendicular to the radial growth directions of the spherulite but parallel to the film plane. The formation of different orientations in the convex and concave bands is attributed to the rhythmic growth behavior for the copolymers with composition distribution along the chains. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 541-547, 2010

The detaching process of two parallel surfaces glued together by a single polyethylene chain in vacuo was investigated with a steered molecular dynamics method. Various statistical properties were analyzed in detail, including the mean-square end-to-end distance; parallel and perpendicular mean-square radii of gyration; shape factor; segment density distribution; average percentages of the microstructure of the chain of the tail, train, bridge, and loop; average surface adsorption energy; average total energy; and average pulling force (〈f〉). All these properties depended strongly on the pulling velocity (v). There existed a peak in the curve of 〈f〉 as a function of the detaching distance. Further, the relation between the maximum value of 〈f〉 and v showed three distinctive regions: a region of weak dependence at v 6.50 A/ps. These investigations may provide some insight into the microcosmic principle of the failure process of polymeric adhesives. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The matrix cracking behavior of slurry cast melt-infiltrated SiC matrix composites consisting of Sylramic-iBN fibers with a wide variety of fiber architectures were compared. The fiber architectures included 2D woven, braided, 3D orthogonal, and angle interlock architectures. Acoustic emission was used to monitor in-plane matrix cracking during unload–reload tensile tests. Two key parameters were found to control matrix-cracking behavior: the fiber volume fraction in the loading direction and the area of the weakest portion of the structure, that is, the largest tow in the architecture perpendicular to the loading direction. Empirical models that support these results are presented and discussed.

Micro-sized patterns were created on thin poly(methyl methacrylate) (PMMA) films by the effect of external field, perpendicular to the film surface. The PMMA film, prepared by spin-coating onto Si wafer, was heated to the fluid temperature (275 °C) and a linear pattern was created by the effect of electric field produced by a strip electrode. In another experiment, a round pattern was created as a result of local laser heating of the PMMA film under homogenous electrical field. The created patterns were analyzed by optical microscopy and profile meter. The dependence of the form and size of the created patterns on the intensity of the electric field, exposure time, and initial film thickness was examined. Wave guiding property of a linear pattern, produced by the above technique, was examined in a simple experiment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1131–1135, 2009

Syndiotactic polystyrene (sPS) nanorods with different diameters have been prepared by using anodic aluminum oxide templates, and the orientation of the sPS crystals in the nanorods has been investigated by FT-IR spectroscopy. It is found that the c axis of the β' crystals preferentially oriented perpendicular to the axis of the nanorod, and the degree of orientation is lower as the diameter of the nanorod decreases. This unexpected result is attributed to nuclei formed at the surface of the nanopores and their subsequent growth, in addition to the preferential growth compatible with the pore direction by the nuclei formed in the bulk film and in the nanorods.