scholarly journals Extracting grain-orientation-dependent data fromin situtime-of-flight neutron diffraction. I. Inverse pole figures

2014 ◽  
Vol 47 (6) ◽  
pp. 2019-2029 ◽  
Author(s):  
G. M. Stoica ◽  
A. D. Stoica ◽  
K. An ◽  
D. Ma ◽  
S. C. Vogel ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
National Laboratory ◽  
Inverse Pole Figure ◽  
Face Centered Cubic ◽  
Oak Ridge ◽  
Weighting Factors ◽  
Quasi Monte Carlo ◽  
Grain Orientations ◽  
Engineering Materials

The problem of calculating the inverse pole figure (IPF) is analyzed from the perspective of the application of time-of flight neutron diffraction toin situmonitoring of the thermomechanical behavior of engineering materials. On the basis of a quasi-Monte Carlo (QMC) method, a consistent set of grain orientations is generated and used to compute the weighting factors for IPF normalization. The weighting factors are instrument dependent and were calculated for the engineering materials diffractometer VULCAN (Spallation Neutron Source, Oak Ridge National Laboratory). The QMC method is applied to face-centered cubic structures and can be easily extended to other crystallographic symmetries. Examples include 316LN stainless steelin situloaded in tension at room temperature and an Al–2%Mg alloy, substantially deformed by cold rolling andin situannealed up to 653 K.

scholarly journals Distinct Recrystallization Pathways in a Cold-Rolled Al-2%Mg Alloy Evidenced by In-Situ Neutron Diffraction

2018 ◽  
Vol 2 (3) ◽  
pp. 17 ◽  
Author(s):  
Grigoreta Stoica ◽  
Luc Dessieux ◽  
Alexandru Stoica ◽  
Sven Vogel ◽  
Govindarajan Muralidharan ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Texture Evolution ◽  
Deformation Texture ◽  
Mg Alloy ◽  
Scanning Calorimetry ◽  
Los Alamos ◽  
Oak Ridge ◽  
Quasi Monte Carlo ◽  
Cold Rolled

The time-of-flight neutron diffraction data collected in-situ on Oak Ridge National Laboratory’s (ORNL, Oak Ridge, TN, USA) VULCAN and Los Alamos National Laboratory’s (LANL, Los Alamos, NM, USA) High-Pressure-Preferred-Orientation (HIPPO) diffractometers have been analyzed complementarily to show the texture evolution during annealing of a cold-rolled Al-2%Mg alloy. The texture analysis aimed to identify the components present in the initial rolling (or deformation) texture and in the thermally-activated recrystallization texture, respectively. Using a quasi-Monte-Carlo (QMC) approach, a new method has been developed to simulate the weighted texture components, and to obtain inverse pole figures for both rolling and normal directions. As such, distinct recrystallization pathways during annealing in isochronal conditions, can be revealed in terms of the evolution of the texture components and their respective volume fractions. Moreover, the recrystallization kinetics associated with the cube and random texture components are analyzed quantitatively using a similar approach developed for differential scanning calorimetry (DSC).

Designing and Validating Parallel Wire Suspension Bridge Wire Strands for Neutron Diffraction Stress Mapping

2017 ◽  
Vol 905 ◽  
pp. 123-130
Author(s):  
Adrian Brügger ◽  
Seung Yub Lee ◽  
İsmail Cevdet Noyan ◽  
Raimondo Betti
Keyword(s):  
Neutron Diffraction ◽  
Steel Wire ◽  
National Laboratory ◽  
Suspension Bridge ◽  
Galvanized Steel ◽  
Element Analysis ◽  
Parallel Wire ◽  
Oak Ridge ◽  
Contact Points ◽  
Suspension Bridge Cables

Suspension-bridge cables are constructed from strands of galvanized steel wire. They are failure-critical structural members, so a fundamental understanding of their mechanics is imminently important in quantifying suspension bridge safety. The load-carrying capabilities of such strands after local wire failures have been the subject of many theoretical studies utilizing analytical equations and finite-element analysis. Little experimental data, however, exists to validate these models.Over the past five years we have developed a methodology for measuring stress/strain transfer within parallel wire strands of suspension bridge cables using neutron diffraction [1,2]. In this paper we describe the design and verification of parallel cable strands used in our studies. We describe the neutron diffraction strain measurements performed on standard 7-wire and expanded 19-wire models in various configurations at both the Los Alamos National Laboratory Spectrometer for Materials Research at Temperature and Stress (LANL SMARTS) and at the Oak Ridge National Laboratory VULCAN Engineering Materials Diffractometer (ORNL VULCAN). Particular attention is placed on the challenges of aligning and measuring multibody systems with high strain gradients at body-to-body contact points.

scholarly journals Preface: Special Topic on Advances in Modern Neutron Diffraction at Oak Ridge National Laboratory

2018 ◽  
Vol 89 (9) ◽  
pp. 092601
Author(s):  
Katharine Page ◽  
Bianca Haberl ◽  
Leighton Coates ◽  
Matthew Tucker
Keyword(s):  
Neutron Diffraction ◽  
National Laboratory ◽  
Special Topic ◽  
Oak Ridge ◽  
Oak Ridge National Laboratory

Neutron macromolecular crystallography

2018 ◽  
Vol 2 (1) ◽  
pp. 39-55 ◽  
Author(s):  
Matthew P. Blakeley ◽  
Alberto D. Podjarny
Keyword(s):  
Neutron Diffraction ◽  
Fluorescent Proteins ◽  
National Laboratory ◽  
Direct Determination ◽  
Drug Binding ◽  
Proton Accelerator ◽  
Biological Macromolecules ◽  
Macromolecular Crystallography ◽  
Neutron Sources ◽  
Oak Ridge

Neutron diffraction techniques permit direct determination of the hydrogen (H) and deuterium (D) positions in crystal structures of biological macromolecules at resolutions of ∼1.5 and 2.5 Å, respectively. In addition, neutron diffraction data can be collected from a single crystal at room temperature without radiation damage issues. By locating the positions of H/D-atoms, protonation states and water molecule orientations can be determined, leading to a more complete understanding of many biological processes and drug-binding. In the last ca. 5 years, new beamlines have come online at reactor neutron sources, such as BIODIFF at Heinz Maier-Leibnitz Zentrum and IMAGINE at Oak Ridge National Laboratory (ORNL), and at spallation neutron sources, such as MaNDi at ORNL and iBIX at the Japan Proton Accelerator Research Complex. In addition, significant improvements have been made to existing beamlines, such as LADI-III at the Institut Laue-Langevin. The new and improved instrumentations are allowing sub-mm3 crystals to be regularly used for data collection and permitting the study of larger systems (unit-cell edges >100 Å). Owing to this increase in capacity and capability, many more studies have been performed and for a wider range of macromolecules, including enzymes, signalling proteins, transport proteins, sugar-binding proteins, fluorescent proteins, hormones and oligonucleotides; of the 126 structures deposited in the Protein Data Bank, more than half have been released since 2013 (65/126, 52%). Although the overall number is still relatively small, there are a growing number of examples for which neutron macromolecular crystallography has provided the answers to questions that otherwise remained elusive.

Development of a compact in situ polarized 3He neutron spin filter at Oak Ridge National Laboratory

2014 ◽  
Vol 85 (7) ◽  
pp. 075112 ◽  
Author(s):  
C. Y. Jiang ◽  
X. Tong ◽  
D. R. Brown ◽  
S. Chi ◽  
A. D. Christianson ◽  
...  
Keyword(s):  
National Laboratory ◽  
Neutron Spin ◽  
Spin Filter ◽  
Oak Ridge ◽  
Oak Ridge National Laboratory

Towards cryogenic neutron crystallography on the reduced form of [NiFe]-hydrogenase

2020 ◽  
Vol 76 (10) ◽  
pp. 946-953
Author(s):  
Takeshi Hiromoto ◽  
Koji Nishikawa ◽  
Seiya Inoue ◽  
Hiroaki Matsuura ◽  
Yu Hirano ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Active Site ◽  
National Laboratory ◽  
Reduced Form ◽  
Desulfovibrio Vulgaris ◽  
X Rays ◽  
Oak Ridge ◽  
Fe Complex ◽  
Cryogenic Conditions

A membrane-bound hydrogenase from Desulfovibrio vulgaris Miyazaki F is a metalloenzyme that contains a binuclear Ni–Fe complex in its active site and mainly catalyzes the oxidation of molecular hydrogen to generate a proton gradient in the bacterium. The active-site Ni–Fe complex of the aerobically purified enzyme shows its inactive oxidized form, which can be reactivated through reduction by hydrogen. Here, in order to understand how the oxidized form is reactivated by hydrogen and further to directly evaluate the bridging of a hydride ligand in the reduced form of the Ni–Fe complex, a neutron structure determination was undertaken on single crystals grown in a hydrogen atmosphere. Cryogenic crystallography is being introduced into the neutron diffraction research field as it enables the trapping of short-lived intermediates and the collection of diffraction data to higher resolution. To optimize the cooling of large crystals under anaerobic conditions, the effects on crystal quality were evaluated by X-rays using two typical methods, the use of a cold nitrogen-gas stream and plunge-cooling into liquid nitrogen, and the former was found to be more effective in cooling the crystals uniformly than the latter. Neutron diffraction data for the reactivated enzyme were collected at the Japan Photon Accelerator Research Complex under cryogenic conditions, where the crystal diffracted to a resolution of 2.0 Å. A neutron diffraction experiment on the reduced form was carried out at Oak Ridge National Laboratory under cryogenic conditions and showed diffraction peaks to a resolution of 2.4 Å.

Sign in / Sign up

Export Citation Format

Share Document