Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ORIENTATION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

A study of the oriented composites with the conductive segregated structure obtained via solid-phase processing of the UHMWPE reactor powder mixed with the carbon nanofillers

Electrically conductive oriented polymer nano-composites of different compositions, based on the reactor powder of ultra-high-molecular-weight polyethylene (UHMWPE) with a special morphology, filled with particles of nanostructured graphite (NG), multi-walled carbon nanotubes (MWCNTs), and electrically conductive carbon black (CB), were investigated. Polymer composites were obtained via compaction of the mechanical mixture of the polymer and filler powder, followed by uniaxial deformation of the material under homogeneous shear (HS) conditions (all of the processing stages were conducted at room temperature). Resulted composites possess a high tensile strength, high level of the electrical conductivity and low percolation threshold, owing it to the formation of the segregated conductive structure, The influence of the type of nanosized carbon filler, degree of the deformation under HS condition, temperature and etc. on the electrical conductivity and mechanical properties of strengthened conductive composites oriented under homogeneous shear conditions was investigated. Changes in the electrical conductivity of oriented composite materials during reversible “tension–shrinkage” cycles along the orientation axis direction were studied. A theoretical approach, describing the process of transformation of the conductive system as a response on polymer phase deformation and volume change, was proposed, based on the data received from the analysis of the conductivity behavior during the uniaxial deformation and thermal treatment of composites.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

TOWARD AN EMPIRICAL THEORY OF PULSAR EMISSION. XI. UNDERSTANDING THE ORIENTATIONS OF PULSAR RADIATION AND SUPERNOVA “KICKS”

Two entwined problems have remained unresolved since pulsars were discovered nearly 50 yr ago: the orientation of their polarized emission relative to the emitting magnetic field and the direction of putative supernova “kicks” relative to their rotation axes. The rotational orientation of most pulsars can be inferred only from the (“fiducial”) polarization angle of their radiation, when their beam points directly at the Earth and the emitting polar fluxtube field is ∥ to the rotation axis. Earlier studies have been unrevealing owing to the admixture of different types of radiation (core and conal, two polarization modes), producing both ∥ or ⊥ alignments. In this paper we analyze some 50 pulsars having three characteristics: core radiation beams, reliable absolute polarimetry, and accurate proper motions (PMs). The “fiducial” polarization angle of the core emission, we then find, is usually oriented ⊥ to the PM direction on the sky. The primary core emission is polarized ⊥ to the projected magnetic field in Vela and other pulsars where X-ray imaging reveals the orientation. This shows that the PMs usually lie ∥ to the rotation axes on the sky. Two key physical consequences then follow: first, to the extent that supernova “kicks” are responsible for pulsar PMs, they are mostly ∥ to the rotation axis; and, second, most pulsar radiation is heavily processed by the magnetospheric plasma such that the lowest altitude “parent” core emission is polarized ⊥ to the emitting field, propagating as the extraordinary (X) mode.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Localization and orientation of heavy-atom cluster compounds in protein crystals using molecular replacement

A new approach is presented that allows the efficient localization and orientation of heavy-atom cluster compounds used in experimental phasing by a molecular replacement procedure. This permits the calculation of meaningful phases up to the highest resolution of the diffraction data. Heavy-atom clusters (HA clusters) containing a large number of specifically arranged electron-dense scatterers are especially useful for experimental phase determination of large complex structures, weakly diffracting crystals or structures with large unit cells. Often, the determination of the exact orientation of the HA cluster and hence of the individual heavy-atom positions proves to be the critical step in successful phasing and subsequent structure solution. Here, it is demonstrated that molecular replacement (MR) with either anomalous or isomorphous differences is a useful strategy for the correct placement of HA cluster compounds. The polyoxometallate cluster hexasodium α-metatungstate (HMT) was applied in phasing the structure of death receptor 6. Even though the HA cluster is bound in alternate partially occupied orientations and is located at a special position, its correct localization and orientation could be determined at resolutions as low as 4.9 Å. The broad applicability of this approach was demonstrated for five different derivative crystals that included the compounds tantalum tetradecabromide and trisodium phosphotungstate in addition to HMT. The correct placement of the HA cluster depends on the length of the intramolecular vectors chosen for MR, such that both a larger cluster size and the optimal choice of the wavelength used for anomalous data collection strongly affect the outcome.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Synthesizing pseudo-Kossel lines from neutron transmission data. I. An analytical approach for recovering single-crystal orientation

The energy-dispersive neutron spectra transmitted through single crystals are characterized by sharp Bragg dips at specific wavelengths, where Bragg's law is being fulfilled for certain crystallographic planes. This phenomenon allows for developing methods for crystal-orientation determination techniques similar to electron backscatter diffraction and X-ray diffraction microscopy. This work presents a new procedure to recover the orientation matrix for single crystals using transmission spectra recorded during rotation of a crystal about an axis perpendicular to a polychromatic neutron beam. The proposed method consists of an initial transformation of the as-collected wavelength–rotation maps to a wavevector $\textit{K}$ space, resulting in linear pseudo-Kossel lines that are suitable for analysis and indexing using image-processing procedures. Further, simulated neutron transmission spectra through a copper crystal with known orientations were used to set and prove the numerical approach. This technique may be expanded for cases where the neutron beam intersects multiple single-crystal grains with different orientations.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Engineering Controlled Spalling in (100)-Oriented GaAs for Wafer Reuse

Controlled spalling offers a way to cleave thin, single-crystal films or devices from wafers, particularly if the fracture planes in the material are oriented parallel to the wafer surface. Unfortunately, misalignment between the favored fracture planes and the wafer surface preferred for photovoltaic growth in (100)-oriented GaAs produces a highly faceted surface when subject to controlled spalling. This highly faceted cleavage surface is problematic in several ways: (1) it can result in large variations of spall depth due to unstable crack propagation; (2) it may introduce defects into the device zone or underlying substrate; and (3) it consumes many microns of material outside of the device zone. We present the ways in which we have engineered controlled spalling for (100)-oriented GaAs to minimize these effects. We expand the operational window for controlled spalling to avoid spontaneous spalling, find no evidence of dislocation activity in the spalled film or the parent wafer, and reduce facet height and facet height irregularity. Resolving these issues provides a viable path forward for reducing III-V device cost through the controlled spalling of (100)-oriented GaAs devices and subsequent wafer reuse when these processes are combined with a high-throughput growth method such as Hydride Vapor Phase Epitaxy.

100 orientation↗
DOE OSTI2015

Growth of twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7} {sub −x} films

YBa{sub 2}Cu{sub 3}O{sub 7−x} films of b orientation have been grown on the surface of (100)SrLaGaO{sub 4} crystal. It is demonstrated that the films pass to the superconducting state at a temperature of 89 K. In the nonsuper-conducting region, the film resistance decreases linearly with a decrease in temperature at a rate of 30 Ω per 100°C. According to the X-ray diffraction data on the crystallographic structure of the YBa{sub 2}Cu{sub 3}O{sub 7−x} films, they are single-crystal and b-oriented. It is shown that the films contain no domains of other crystallographic orientations, including a-oriented domains. Therefore, the films are free of structural twins.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Tailoring Vanadium Dioxide Film Orientation Using Nanosheets: a Combined Microscopy, Diffraction, Transport, and Soft X‐Ray in Transmission Study

Abstract Vanadium dioxide (VO 2 ) is a much‐discussed material for oxide electronics and neuromorphic computing applications. Here, heteroepitaxy of VO 2 is realized on top of oxide nanosheets that cover either the amorphous silicon dioxide surfaces of Si substrates or X‐ray transparent silicon nitride membranes. The out‐of‐plane orientation of the VO 2 thin films is controlled at will between (011) M1 /(110) R and (−402) M1 /(002) R by coating the bulk substrates with Ti 0.87 O 2 and NbWO 6 nanosheets, respectively, prior to VO 2 growth. Temperature‐dependent X‐ray diffraction and automated crystal orientation mapping in microprobe transmission electron microscope mode (ACOM‐TEM) characterize the high phase purity, the crystallographic and orientational properties of the VO 2 films. Transport measurements and soft X‐ray absorption in transmission are used to probe the VO 2 metal–insulator transition, showing results of a quality equal to those from epitaxial films on bulk single‐crystal substrates. Successful local manipulation of two different VO 2 orientations on a single substrate is demonstrated using VO 2 grown on lithographically patterned lines of Ti 0.87 O 2 and NbWO 6 nanosheets investigated by electron backscatter diffraction. Finally, the excellent suitability of these nanosheet‐templated VO 2 films for advanced lensless imaging of the metal–insulator transition using coherent soft X‐rays is discussed.

Le, Phu Tran Phong↗
DOE OSTI2021

Orientational Ordering within Semiconducting Polymer Fibrils

Abstract Due to a general paucity of suitable characterization methods, the internal orientational ordering of polymer fibrils has rarely been measured despite its importance particularly for semi‐conducting polymers. An emerging tool with sensitivity to bond orientation is polarized resonant soft X‐ray scattering (P‐RSoXS). Here, P‐RSoXS reveals the molecular arrangement within fibrils (if type I or type II fibrils), the extent of orientation in the fibril crystal, and an explicit crystal‐amorphous interphase. Neat films as well as binary blends with a fullerene derivative are characterized for three different polymers, that are prototypical materials widely used in organic electronics applications. Anisotropic P‐RSoXS patterns reveal two different fibril types. Analysis of the q ‐dependence of the anisotropy from simulated and experimental scattering patterns reveal that neat polymer fibrillar systems likely comprise more than two phases, with the third phase in addition to crystal and amorphous likely being an interphase with distinct density and orientation. Intriguingly, the fibril type correlates to the H‐ or J‐aggregation signature in ultraviolet‐visible (UV–vis) spectroscopy, revealing insight into the fibril formation. Together, the results will open the door to develop more sophisticated structure‐function relationships between chemical design, fibril type, formation pathways and kinetics, interfacial ordering, and eventually device functions.

Mukherjee, Subhrangsu↗
DOE OSTI2015

Non‐invasive imaging of cellulose microfibril orientation within plant cell walls by polarized Raman microspectroscopy

ABSTRACT Cellulose microfibrils represent the major scaffold of plant cell walls. Different packing and orientation of the microfibrils at the microscopic scale determines the macroscopic properties of cell walls and thus affect their functions with a profound effect on plant survival. We developed a polarized Raman microspectroscopic method to determine cellulose microfibril orientation within rice plant cell walls. Employing an array of point measurements as well as area imaging and subsequent Matlab‐assisted data processing, we were able to characterize the distribution of cellulose microfibril orientation in terms of director angle and anisotropy magnitude. Using this approach we detected differences between wild type rice plants and the rice brittle culm mutant, which shows a more disordered cellulose microfibril arrangement, and differences between different tissues of a wild type rice plant. This novel non‐invasive Raman imaging approach allows for quantitative assessment of cellulose fiber orientation in cell walls of herbaceous plants, an important advancement in cell wall characterization. Biotechnol. Bioeng. 2016;113: 82–90. © 2015 Wiley Periodicals, Inc.

Sun, Lan↗
DOE OSTI2017

100-Fold Enhancement of Charge Transport in Uniaxially Oriented Mesoporous Anatase TiO 2 Films

Mesoporous semiconductor films are of considerable interest for applications in photoelectrochemical devices, however, despite intensive research till now, their charge transport properties remain significantly lower than their single-crystal counterparts. Herein, we report a novel low-temperature template-free technique for growing high surface area mesoporous anatase TiO2 films with a preferred [001] crystalline-orientation on FTO-coated glass substrate. Compared to mesoporous films that comprised of randomly oriented crystallites, the uniaxial orientation enables a 100-fold increase in the rate of electron transport. The uniaxially oriented mesoporous anatase TiO2 films exhibit should greatly facilitate the development and application of photoelectrochemical and electrochemical devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Photonic devices fabricated from (111)‐oriented single crystal diamond

Abstract Diamond is a material of choice in the pursuit of integrated quantum photonic technologies. So far, the majority of photonic devices fabricated from diamond are made from (100)‐oriented crystals. In this work, we demonstrate a methodology for the fabrication of optically active membranes from (111)‐oriented diamond. We use a liftoff technique to generate membranes, followed by chemical vapor deposition of diamond in the presence of silicon to generate homogenous silicon vacancy color centers with emission properties that are superior to those in (100)‐oriented diamond. We further use the diamond membranes to fabricate microring resonators with quality factors exceeding ~ 3000. Supported by finite‐difference time‐domain calculations, we discuss the advantages of (111)‐oriented structures as building blocks for quantum nanophotonic devices. image

Regan, Blake↗
DOE OSTI2025

In Situ 4D‐STEM Imaging of the Orientation of Lamellar Clusters in Polymer Crystallization

In semi‐crystalline polymeric materials, the initial stages of nucleation and the growth path of crystalline domains can determine the final performance. Here, in this work, we used four‐dimensional scanning transmission electron microscopy (4D‐STEM) imaging to analyze the changes in lamellar orientation in high‐density polyethylene (HDPE) during heating and cooling. This method allowed us to quantitatively detect the formation of lamellae clusters with different in‐plane orientations, which are not visible with traditional methods. Our analysis provided detailed insights into the orientation and size changes of crystalline domains. Additionally, this technique enabled direct observation of lattice structures in hierarchical lamellae and the growth of crystals, confirming the local variability in lamellar orientation. This innovative approach significantly improves our understanding of polymer crystallization, linking changes in morphology and lattice structures at different length scales.

4D-STEM↗
DOE OSTI2020

Preferred Void Orientation in Uniaxially Pressed PBX 9502

Ultra- and small-angle neutron scattering techniques were used to study the morphology of voids in directions parallel and perpendicular to the compaction plane of a uniaxially pressed cylinder of PBX 9502. Two-dimensional scattering patterns from samples cut parallel to the compaction plane had circular equal-intensity contours, implying that along this view the voids are circular or randomly oriented. Identical measurements of samples cut perpendicular to the compaction plane produced elliptical equal-intensity contours, indicating preferred orientation of voids. Analysis of the two dimensional scattering patterns confirmed that the voids are non-spherical with an average aspect ratio of 1.20, flattened so that the larger dimensions of the voids lie within the compaction plane. Model analysis of the combined ultra- and small-angle neutron scattering curves revealed that the PBX 9502 porosity is interconnected, in the form of aggregates comprised of non-spherical, primary voids. The volume dimension was found to be the same in both directions, indicating that the aggregate is randomly oriented throughout the sample, and that it is the primary voids that are preferentially oriented. Furthermore, void interfaces with the surrounding matrix were found to be rough or polydisperse, with a common roughness dimension or polydispersity in all directions.

42 ENGINEERING↗
DOE OSTI2025

V‐Groove Si Nanopatterning for the Direct Epitaxy of Orientation‐Patterned III–V Nonlinear Optical Crystals

Orientation‐patterned (OP) III–V semiconductors—used as quasi‐phase‐matched crystals for nonlinear optics applications—are typically epitaxially grown on expensive III–V substrates using a complex process requiring three separate epitaxy steps. In this work, a method is demonstrated for growing orientation‐patterned III–V crystals on Si substrates through V‐groove nanopatterning and a single epitaxial growth. V‐groove Si allows for suppression of random antiphase domain formation that is typical of III–V growth on (001)‐oriented Si through the use of (111)‐faceted trenches patterned on (001)‐oriented Si substrates. By alternating the directions of the V‐groove trenches between [110] and [10], antiphase boundaries can be selectively induced at the boundaries between the two directions of trenches due to the difference in symmetry between the III–V material and Si. This approach allows for a greatly simplified process for growing OP‐III‐Vs and more broadly is a new, robust approach for precisely patterning antiphase boundaries of arbitrary shape and length scales down to 50 nm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Fabrication of oriented crystals as force measurement tips via focused ion beam and microlithography methods

Detailed knowledge of the forces between nanocrystals is very crucial for understanding many generic (e.g., random aggregation/assembly and rheology) and specific (e.g., oriented attachment) phenomena at macroscopic length scales, especially considering the additional complexities involved in nanocrystals such as crystal orientation and corresponding orientation-dependent physicochemical properties. Because there are a limited number of methods to directly measure the forces, little is known about the forces that drive the various emergent phenomena. Here we report on two methods of preparing crystals as force measurement tips used in an atomic force microscope (AFM): the focused ion beam method and microlithography method. The desired crystals are fabricated using these two methods and are fixed to the AFM probe using platinum deposition, ultraviolet epoxy, or resin, which allows for the orientation-dependent force measurements. These two methods can be used to attach virtually any solid particles (from the size of a few hundreds of nanometers to millimeters). We demonstrate the force measurements between aqueous media under different conditions such as pH.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2025

Methodologies and strategies for detecting fiber orientation in polymeric fiber-reinforced composites

In this review paper different methods and techniques for representing fiber orientation in advanced polymer matrix composites are presented. A description of the effect of fiber orientation on processing, fabrication and mechanical properties of a composite material is presented. The paper discusses the mathematical modeling and modeling techniques for fiber structure representation in polymeric composites, with an emphasis on fiber orientation in a composite part. The paper is divided into two sections; namely—destructive techniques and non-destructive techniques. The capabilities and limitations of each technique with respect to fiber orientation detection and measurements are discussed.

composites↗
DOE OSTI2019

Build Orientation Effects on Texture and Mechanical Properties of Selective Laser Melting Inconel 718

The production of components via selective laser melting (SLM) metal additive manufacturing results in microstructures unique to the process that are highly dependent on laser processing parameters and orientation of part geometry relative to the build direction. This study investigates the variation in tensile properties of SLM Inconel 718 at varying angles with respect to build direction. ASTM E8 tensile specimens were built in XY, Z, and B+45 from Z orientations to near-net shape, HIP and heat treated, and tensile tested at room temperature. Orientation dependence of mechanical properties was observed; Z samples had the lowest strength and highest elongation, while XY samples had the highest strength and lowest elongation. Optical, SEM, and EBSD analysis were conducted to probe for microstructure variation that could be the cause of the difference in mechanical properties. Analysis of pole figures and grain maps suggests a preferred grain texture and twinning orientation that aligns with the build direction, which may contribute to the anisotropic enhancement in ductility.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Subgroup analysis of efficacy and safety of orantinib in combination with TACE in Japanese HCC patients in a randomized phase III trial (ORIENTAL)

A randomized, phase III trial of orantinib in combination with transcatheter arterial chemoembolization (TACE) did not prolong overall survival (OS) over placebo (ORIENTAL study). A subgroup analysis was conducted to evaluate the efficacy and safety of orantinib in Japanese patients enrolled in the ORIENTAL study. The data of Japanese patients from this study were analyzed. The overall survival (OS), time to progression (TTP), and time to TACE failure (TTTF) were compared between orantinib and placebo arms using stratified log-rank test. Since TTTF in patients with Barcelona Clinic Liver Cancer stage B (BCLC-B) showed favor outcome in this study, the OS and TTTF according to BCLC staging system were also analyzed. The subgroup analysis consisted of 219 and 213 patients in the orantinib and placebo arms. Median OS was 32.5 vs 33.0 months (p = 0.906), median TTP was 4.7 vs 3.1 months (p = 0.011), and median TTTF was 25.3 vs 18.2 months (p = 0.160) in the orantinib and placebo groups, respectively. Patients with BCLC-B in the orantinib and placebo groups showed a median OS of 33.7 and 30.1 months, respectively (p = 0.260), while the corresponding median TTTF were 25.3 and 14.0 months (p = 0.125). The Japanese population safety profile was similar to all over population in the ORIENTAL study. No significant differences were observed in the OS and TTTF though the TTP was significantly improved in the orantinib arm. The OS and TTTF showed a tendency to be prolonged following orantinib treatment of Japanese HCC patients with BCLC-B in the ORIENTAL study.

62 RADIOLOGY AND NUCLEAR MEDICINE↗