Crystalline Orientation Distribution Research Articles

Non-volatile magnon transport in a single domain multiferroic

Antiferromagnets have attracted significant attention in the field of magnonics, as promising candidates for ultralow-energy carriers for information transfer for future computing. The role of crystalline orientation distribution on magnon transport has received very little attention. In multiferroics such as BiFeO3 the coupling between antiferromagnetic and polar order imposes yet another boundary condition on spin transport. Thus, understanding the fundamentals of spin transport in such systems requires a single domain, a single crystal. We show that through Lanthanum (La) substitution, a single ferroelectric domain can be engineered with a stable, single-variant spin cycloid, controllable by an electric field. The spin transport in such a single domain displays a strong anisotropy, arising from the underlying spin cycloid lattice. Our work shows a pathway to understanding the fundamental origins of magnon transport in such a single domain multiferroic.

Machining stability improvement in LPBF printed components through stiffening by crystallographic texture control

The quality requirements of functional parts manufactured by the laser powder bed fusion imply post-processing machining operations. These components include thin walls, hollow and complex shapes that can lead to machining instability. This paper presents a strategy to exploit the inherent crystallographic effect as a tool for stiffening and improving machining stability by considering the orientation of machining bending loads and the crystalline orientation distribution. Three samples were manufactured under the same LPBF parameters but different crystallographic orientations. The results show that the optimal crystalline direction increases static and dynamic stiffness and stability, reducing machining chatter risks.

Measurement of the single crystal elasticity matrix of polycrystalline materials

Many engineering metals are polycrystalline, as such the elasticity, crystalline orientation and grain distribution are cardinal factors in determining the physical properties of the material. The grain distribution can be measured using a number of different techniques and the orientation by a subset of these (electron back scatter diffraction, spatially resolved acoustic spectroscopy). These measurements are routinely deployed in materials development. However, the elasticity remains a more difficult parameter to measure and is rarely measured because the existing techniques are slow and cumbersome, with most current techniques requiring the laborious growth or destructive isolation of single crystals. In this work we present a technique that can determine the elasticity, crystalline orientation and grain distribution in a fast and easy measurement. The technique utilises SRAS imaging to provide the raw measurement of single grain velocity surfaces, this is input to a novel inverse solver that mitigates the problem of the inversion being very ill-conditioned, by simultaneously solving for multiple uniquely orientated grains at once in a brute-force approach. This allows simultaneous determination of the elastic constants and crystallographic orientation. Furthermore, this technique has the potential to work on polycrystalline materials with minimal preparation and is capable of high accuracy, with the potential to realise errors in the determination of elastic constants values of less than 1 GPa (∼1). In this work we demonstrate good agreement with EBSD (<6∘ disagreement on average for all Euler angles) and determine elastic constants in line with existing single-crystal values, with an expected accuracy of better than 4 GPa. Experimental results are presented for pure α-Ti (hexagonal), Ni and the more exotic Ni-base alloy CMSX-4 (both cubic). With the proposed method, once the initial measurement has been made, subsequent measurements of the elasticity on the same sample can be made rapidly so that the elasticity can be measured in real time, opening the possibility that on-line measurement of elasticity can be used to monitor processes and enable high-throughput materials screening. The current instrumentation approach is applicable to materials with grain sizes down to 50 µm, with the possibility of improving this to grain sizes of ∼5 µm. Further modifications to instrumentation and acoustic velocity calculation will facilitate greater accuracy in the determination of elastic constants.

From the Editor

Layered silicates present interaction sites at both faces and edges of the nanolayers and silane coupling agents that locate at both sites lead to polymer nanocomposites with superior melt strength and properties. This work’s objective was (a) to investigate the effectiveness of solvent-free, vapor phase, silane treatment of the nanolayers for formulating masterbatches and (b) to compare the mechanical properties of 1mil thick blown films from polypropylene copolymer nanocomposites with such coupling, to films from the neat polypropylene. The nanocomposite blown film tensile modulus and tensile strength improved along both the draw direction and the transverse direction. In addition, their elongation to failure was close to 500% along both directions, in contrast to values of 500% along MD and 170% along TD for the neat PP copolymer. These trends may be understood in terms of the crystalline lamellar orientation distribution in the films. FESEM images revealed that cross-hatched lamellae were absent from the unfilled PP blown film and were pervasive in the nanocomposite blown film. The nanolayers were oriented in the film plane with the longer dimension largely along the MD. The lower extent of lamellar orientation around nanolayers may be attributed to the strong reduction in the polymer chain mobility attached to the nanolayers. Polyaniline and quantum dot-based nanostructures: Developments and perspectives” also by Ayesha Kausar reviews Quantum dots which are 2–5 nm nanoparticles with exceptional optical, electronic, luminescence, and semiconducting properties. Polyaniline is an exclusive conjugated polymer. This article reviews recent efforts, scientific trials, and technological solicitations for polyaniline/quantum dot-based nanocomposites. Polyaniline/quantum dot mixtures form a unique composition for advance materials and applications. Carbon dots, graphene quantum dots, and several inorganic quantum dots have been added to a conducting polymer. A functional quantum dot may develop electrostatic, van der Waal, and p–p stacking interactions with the conjugated polymer backbone. Uniform quantum dot dispersion in polyaniline may result in inimitable morphology, electrical conductivity, electrochemical properties, capacitance, and sensing features. Finally, this review expounds on the many applications for polyaniline/quantum dot nanocomposites including dye-sensitized solar cell, supercapacitor, electronics, gas sensor, biosensor, and bioimaging. And a final thought. “The power of population is so superior to the power of the Earth to produce subsistence for man, that premature death must in some shape or other visit the human race” Thomas Malthus 1798

Efficient Slantwise Aligned Dion-Jacobson Phase Perovskite Solar Cells Based on Trans-1,4-Cyclohexanediamine.

The crystalline orientation and phase distribution are two important parameters for high-performance 2D perovskite solar cells. Therefore, it is essential to understand how the structure of spacer ligands influences the orientation and phase distribution of resulting 2D perovskite films. In this work, a new member of Dion-Jacobson (DJ) phase 2D perovskites based on trans-1,4-cyclohexanediamine (CHDA) is demonstrated and it is found that the crystalline orientation is self-aligned spontaneously, which is different from the well-known graded distribution in controlled sample with its isomer 1,6-diaminohexane (HDA) as spacer ligand. Grazing incident X-ray scattering suggests that the exact alignment is strongly slantwise to the substrate while it is still beneficial for charge transfer along the vertical structure of devices. The devices can achieve high efficiency up to 15.01% for (CHDA)MA3 Pb4 I13 (n= 4), one of the highest efficiencies reported by now. The encapsulated (CHDA)MA3 Pb4 I13 (n= 4) devices can retain 80.7% efficiency for 270 min under continuous maximum power point tracking. (CHDA)MA3 Pb4 I13 (n= 4) devices can retain 96.5% efficiency under 60°C and 74.4% efficiency under 70°C heating for 68 h. The results demonstrate the slantwise aligned DJ phase perovskite solar cells with excellent stability.

Blown films with balanced in-plane properties from polypropylene-clay nanocomposites though silane coupling

Layered silicates present interaction sites at both faces and edges of the nanolayers and silane coupling agents that locate at both sites lead to polymer nanocomposites with superior melt strength and properties. This work’s objective was (a) to investigate the effectiveness of solvent-free, vapor phase, silane treatment of the nanolayers for formulating masterbatches and (b) to compare the mechanical properties of 1 mil thick blown films from polypropylene copolymer nanocomposites with such coupling, to films from the neat polypropylene. The nanocomposite blown film tensile modulus and tensile strength improved along both the draw direction and the transverse direction. In addition, their elongation to failure was close to 500% along both directions, in contrast to values of 500% along MD and 170% along TD for the neat PP copolymer. These trends may be understood in terms of the crystalline lamellar orientation distribution in the films. FESEM images revealed that cross-hatched lamellae were absent from the unfilled PP blown film and were pervasive in the nanocomposite blown film. The nanolayers were oriented in the film plane with the longer dimension largely along the MD. The lower extent of lamellar orientation around nanolayers may be attributed to the strong reduction in the polymer chain mobility attached to the nanolayers.

{111}&lt;110&gt; Orientation Induced Anisotropy of Shape Memory Effect in NiTiNb Pipe Joints

This work aims to clarify the influence of texture type and intensity on the shape memory effect (SME) in NiTiNb shape memory alloy (SMA) pipe joints, especially revealing the causes for the anisotropy of SME via texture changes. Three NiTiNb rods with different intensities of the {111}&lt;110&gt; texture were fabricated, and their microstructures, crystalline orientation distribution functions and inverse pole figures were obtained by X-ray diffraction and electron backscatter diffraction measurements. Simultaneously, the SME was characterized by inner-diameter recoverability of the corresponding pipe joints. For a given intensity of the {111}&lt;110&gt; texture, the SME of the NiTiNb pipe joints strongly depended on the expansion direction due to {111}&lt;110&gt; orientation-induced anisotropy of SME. In addition, both the SME and anisotropy of NiTiNb pipe joints increased with the increased intensity of the {111}&lt;110&gt; texture. Therefore, a suitable expansion direction and strong texture intensity should be considered for high SME in NiTiNb pipe joints.

Imaging the crystal orientation of 2D transition metal dichalcogenides using polarization-resolved second-harmonic generation

We use laser-scanning nonlinear imaging microscopy in atomically thin transition metal dichalcogenides (TMDs) to reveal information on the crystalline orientation distribution, within the 2D lattice. In particular, we perform polarization-resolved second-harmonic generation (PSHG) imaging in a stationary, raster-scanned chemical vapor deposition (CVD)-grown WS₂ flake, in order to obtain with high precision a spatially resolved map of the orientation of its main crystallographic axis (armchair orientation). By fitting the experimental PSHG images of sub-micron resolution into a generalized nonlinear model, we are able to determine the armchair orientation for every pixel of the image of the 2D material, with further improved resolution. This pixel-wise mapping of the armchair orientation of 2D WS₂ allows us to distinguish between different domains, reveal fine structure, and estimate the crystal orientation variability, which can be used as a unique crystal quality marker over large areas. The necessity and superiority of a polarization-resolved analysis over intensity-only measurements is experimentally demonstrated, while the advantages of PSHG over other techniques are analysed and discussed.

Study and classification of the Crystallographic Orientation Distribution Function of a non-grain oriented electrical steel using computer vision system

This article discusses a fast and efficient classification of non-grain oriented electrical steel and its electromagnetic efficiency based on the analysis of the images of the Crystalline Orientation Distribution Function (CODF). The study was carried out on samples of a non-grain oriented electrical steel, semi-processed with 1.28% silicon, cold rolled with thickness reductions of 50.0% and 70.0%, and annealed at 730°C for 12h. The material was also subjected to annealing heat treatment for grain growth at temperatures of 620°C, 730°C, 840°C and 900°C for 1, 10, 100 and 1000min at each temperature. The database used was comprised of 32 images. The extractors Gray Level Co-occurrence Matrix (GLCM), Local Binary Patterns (LBP), Central Moments, Statistical Moments, and Hu's Moments were combined with the following classifiers: Bayes, k-Nearest Neighbor (kNN) with 1, 3, and 5 nearest neighbors, MultiLayer Perceptron (MLP) with two configurations, Support Vector Machines (SVM) with four different kernel types (linear, polynomial, radial basis function (RBF) and sigmoid). For all the using cases the method of partitioning data Hold Out. Measurements of precision, sensitivity, specificity and positive predictive values, as well as the confusion matrix were used to evaluate the classifiers. The SVM with polynomial using the GLCM extractor had the highest accuracy rate of 89.00%, specificity of 86.93%, sensitivity of 80.69% and positive predictive values of 80.34%. The time required for this combination, which was the best, was only 0.6ms. The results showed that this approach generated a new methodology for the analysis of non-grain oriented electrical steels.

Characterization of Crystallographic Structures Using Bragg-Edge Neutron Imaging at the Spallation Neutron Source

Over the past decade, wavelength-dependent neutron radiography, also known as Bragg-edge imaging, has been employed as a non-destructive bulk characterization method due to its sensitivity to coherent elastic neutron scattering that is associated with crystalline structures. Several analysis approaches have been developed to quantitatively determine crystalline orientation, lattice strain, and phase distribution. In this study, we report a systematic investigation of the crystal structures of metallic materials (such as selected textureless powder samples and additively manufactured (AM) Inconel 718 samples), using Bragg-edge imaging at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS). Firstly, we have implemented a phenomenological Gaussian-based fitting in a Python-based computer called iBeatles. Secondly, we have developed a model-based approach to analyze Bragg-edge transmission spectra, which allows quantitative determination of the crystallographic attributes. Moreover, neutron diffraction measurements were carried out to validate the Bragg-edge analytical methods. These results demonstrate that the microstructural complexity (in this case, texture) plays a key role in determining the crystallographic parameters (lattice constant or interplanar spacing), which implies that the Bragg-edge image analysis methods must be carefully selected based on the material structures.

Mechanical study of crystalline orientation distribution in Ti-6Al-4V: An assessment of micro-texture induced load partitioning

Microtextured regions are known to have a detrimental effect on the fatigue performance of near α and α/β titanium alloys. Due to the elastic anisotropy of α titanium, stress heterogeneities are expected to result from such microstructural features. The present work is an assessment of their influence on the elastic stress field, using Fast Fourier Transform-based computations on a 2D extruded aggregate built from a real microstructure. The contribution of the microtextured regions was then isolated by comparing simulations obtained on a synthetic aggregate with similar grain morphology and texture but removed microtextured regions through a redistribution of crystalline orientations. The analysis of the computed fields revealed that the average stress experienced by α grains is only weakly affected by the neighborhood and mostly determined by the elastic anisotropy of α titanium. Nevertheless, complex mechanical interactions between microtextured regions were evidenced. Indeed, load partitioning and non-local influence on the stress field were found to result from the presence of microtextured regions. The implications on fatigue crack initiation are discussed in light of these results.

The Influence of Crystallographic Texture and Niobium Stabilisation on the Corrosion Resistance of Ferritic Stainless Steel

The objective of this work is to investigate the influence of the crystallographic texture on the corrosion resistance of 16% Cr ferritic stainless steel. Samples of ASTM S43000 ferritic stainless steel, both niobium-stabilised and non-stabilised, were used. The samples were subjected to crystallographic characterisation (EBSD) and analysed using an inverse pole figure (IPF) and a crystalline orientation distribution function (CODF). The samples also underwent anodic potentiodynamic polarisation tests (deaeration by high-purity argon gas) in 3.56% NaCl and 1N H2SO4 solutions, and the surface was examined by SEM after the tests. The results showed a clear influence of the crystallographic texture on the corrosion resistance. The niobium decreases the amount of the preferred orientation and thus the influence of the texture on the corrosion resistance, although the corrosion resistance of the stainless steel is increased as niobium carbides are formed.

A direct correlation of x-ray diffraction orientation distributions to the in-plane stiffness of semi-crystalline organic semiconducting films

Large charge mobilities of semi-crystalline organic semiconducting films could be obtained by mechanically aligning the material phases of the film with the loading axis. A key element is to utilize the inherent stiffness of the material for optimal or desired alignment. However, experimentally determining the moduli of semi-crystalline organic thin films for different loading directions is difficult, if not impossible, due to film thickness and material anisotropy. In this paper, we address these challenges by presenting an approach based on combining a composite mechanics stiffness orientation formulation with a Gaussian statistical distribution to directly estimate the in-plane stiffness (transverse isotropy) of aligned semi-crystalline polymer films based on crystalline orientation distributions obtained by X-ray diffraction experimentally at different applied strains. Our predicted results indicate that the in-plane stiffness of an annealing film was initially isotropic, and then it evolved to transverse isotropy with increasing mechanical strains. This study underscores the significance of accounting for the crystalline orientation distributions of the film to obtain an accurate understanding and prediction of the elastic anisotropy of semi-crystalline polymer films.

Determination of all elastic and plastic parameters for sheets of cubic metals only by uniaxial tension tests

Most of sheet metals belong to orthorhombic aggregates of cubic crystallites. Since both the elasticity tensor and the yield function of sheet metals depend on the crystalline orientation distribution, some correlations between elasticity and plasticity must exist. Employing the correlations, herein we derive the computational expressions of determining all elastic and plastic parameters in the elasticity tensor and the general Hosford yield function only by the data of uniaxial tension tests. By the elastic FEM numerical simulations and the plastic Taylor-Bishop-Hill model's numerical simulations, we verify the correlations and the computational expressions, and compare the general Hosford yield function with the Hill quadratic yield function and the Hill 1990 yield function. The main goal of this paper is to give a method of determining all the elastic and plastic parameters in the elasticity tensor and the general Hosford yield function only by uniaxial tension tests.

Microstructure and Properties of Deformation Processed Polycrystalline Ni47Ti44Nb9 Shape Memory Alloy

The objective of this work was to investigate the relationships between process and microstructure and property in polycrystalline Ni47Ti44Nb9 alloy. Three processes: (1) hot-forged, (2) cold-drawn, and (3) cold-rolled were investigated. The microstructure was tested by means of optical microscope, x-ray diffraction, and electron backscatter diffraction, and then crystalline orientation distribution functions and inverse pole figures were measured. The results indicated that hot-forging eliminated dendritic microstructure and fined the eutectic structure. It also induced a 〈113〉 fiber texture, which paralleled to the axial direction. The cold drawing and cold-rolling had a further effect in grain refinement. And the cold-drawn specimens contained a strong 〈111〉 fiber texture paralleling to the deformation direction, while the cold-rolled tubes formed 〈111〉 crystalline directions paralleling the axial direction and 〈110〉 crystalline directions of crystalline arranged along the circumferential direction. The notably distinctive recoverability of different processed materials was observed and discussed.

Enhanced orientation of the water‐assisted injection‐molded ipp in the presence of nucleating agent

AbstractThe nucleated isotactic polypropylene (iPP) was molded by water‐assisted injection molding. The crystalline morphology and orientation distribution were studied. The results show that shear brought by melt filling and pressurized water penetration can separately induce the formation of oriented structures in skin region (i.e., the region near mold cavity wall) and the water channel region. For virgin iPP, slightly oriented lamellae appear exclusively in the above aforementioned regions. However, shish‐kebab structure occurs not only in skin and water channel region of the iPP containing moderate content of nucleator (0.2 wt%) but also in the whole region of the iPP containing a higher content of nucleator (1 wt%). It is well known that nucleator cannot directly induce the development of shish‐kebab in the absence of shear, thus the results indicate: shear flow actually distributes over a much broader range than expected; in shear field, nucleator is significantly helpful for the shear which is not sufficient to solely induce oriented structure to promote the formation of the oriented structure. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Moving through the Phase Diagram: Morphology Formation in Solution Cast Polymer–Fullerene Blend Films for Organic Solar Cells

The efficiency of organic bulk heterojunction solar cells strongly depends on the multiscale morphology of the interpenetrating polymer-fullerene network. Understanding the molecular assembly and the identification of influencing parameters is essential for a systematic optimization of such devices. Here, we investigate the molecular ordering during the drying of doctor-bladed polymer-fullerene blends on PEDOT:PSS-coated substrates simultaneously using in situ grazing incidence X-ray diffraction (GIXD) and laser reflectometry. In the process of blend crystallization, we observe the nucleation of well-aligned P3HT crystallites in edge-on orientation at the interface at the instant when P3HT solubility is crossed. A comparison of the real-time GIXD study at ternary blends with the binary phase diagrams of the drying blend film gives evidence of strong polymer-fullerene interactions that impede the crystal growth of PCBM, resulting in the aggregation of PCBM in the final drying stage. A systematic dependence of the film roughness on the drying time after crossing P3HT solubility has been shown. The highest efficiencies have been observed for slow drying at low temperatures which showed the strongest P3HT interchain π-π-ordering along the substrate surface. By adding the "unfriendly" solvent cyclohexanone to a chlorobenzene solution of P3HT:PCBM, the solubility can be crossed prior to the drying process. Such solutions exhibit randomly orientated crystalline structures in the freshly cast film which results in a large crystalline orientation distribution in the dry film that has been shown to be beneficial for solar cell performance.

Anisotropic Mechanical Behavior of Ni-base Alloy Weld Metal Considering Crystal Orientation Distribution

Microscopic stress distribution in cladded weld metal of Ni-base alloy was calculated. Simulation model of a columnar grain aggregate was generated based on a crystal orientation measurement result by electron backscatter diffraction method. Microscopic stress much higher than applied macroscopic stress was observed when load was applied along transverse direction of columnar grain growth direction. On the other hand, homogeneous microscopic stress was obtained in a columnar grain model when macroscopic stress was applied in columnar grain growth direction. The difference caused from anisotropic crystalline orientation distribution of weld metal, and is important in the evaluation of microscopic stress distribution in weld metal.

Influence of the Crystallographic and the Morphological Texture on the Elastic Properties of Fcc Crystal Aggregates

In this contribution, the prediction of the self-consistent homogenization method with regard to the effective material response of cubic crystal aggregates is analyzed and compared to results from full field simulations. The influence of the crystalline orientation distribution but also the effect of the grain shape on the macroscopic elastic response of sheet metals is especially emphasized.

Direction-dependent functions of physical properties for crystals and polycrystals

Some physical properties of crystals differ in direction n because crystal lattices are often anisotropic. A polycrystal is an aggregate of numerous tiny crystallites. Unless the polycrystal is an isotropic aggregate of crystallites, the physical properties of the polycrystal vary with n. The direction-dependent functions (DDF) for crystals and polycrystals are introduced to describe the variations of the physical properties in direction n. Until now there are few papers dealing systematically with relations between the DDF and the crystalline orientation distribution. Herein we give general expressions of the DDF for crystals and polycrystals. We discuss the applications of the DDF in describing the physical properties of crystals and polycrystals.