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At least 739 records · Page 41

Accurate and Data‐Efficient Micro X‐ray Diffraction Phase Identification Using Multitask Learning: Application to Hydrothermal Fluids

Traditional analysis of highly distorted micro X‐ray diffraction (μ‐XRD) patterns from hydrothermal fluid environments is a time‐consuming process, often requiring substantial data preprocessing and labeled experimental data. Herein, the potential of deep learning with a multitask learning (MTL) architecture to overcome these limitations is demonstrated. MTL models are trained to identify phase information in μ‐XRD patterns, minimizing the need for labeled experimental data and masking preprocessing steps. Notably, MTL models show superior accuracy compared to binary classification convolutional neural networks. Additionally, introducing a tailored cross‐entropy loss function improves MTL model performance. Most significantly, MTL models tuned to analyze raw and unmasked XRD patterns achieve close performance to models analyzing preprocessed data, with minimal accuracy differences. This work indicates that advanced deep learning architectures like MTL can automate arduous data handling tasks, streamline the analysis of distorted XRD patterns, and reduce the reliance on labor‐intensive experimental datasets.

97 MATHEMATICS AND COMPUTING↗

Active-Phase Formation and Stability of Gd/Pt(111) Electrocatalysts for Oxygen Reduction: An In Situ Grazing Incidence X-Ray Diffraction Study

Alloys of platinum and gadolinium present significant activity enhancement over pure Pt for the oxygen reduction reaction (ORR), both in the form of extended electrode surfaces and nanoparticulate catalysts. The active phase consists of a compressed Pt overlayer formed on Pt 5 Gd electrodes upon exposure to the electrolyte by acid leaching. Here, we investigate the formation, strain and correlation lengths of the active Pt overlayer by using in situ synchrotron grazing incidence X–ray diffraction on Gd/Pt(111) single–crystalline electrodes. The overlayer forms upon exposure to electrolyte under open circuit conditions; the compressive strain relaxes slightly upon repeated electrochemical cycling in the potential range 0.6 to 1.0 V versus the reversible hydrogen electrode (RHE). Furthermore, the strain relaxes strongly when exposing the electrode to 1.2 V versus RHE, and the thickness of the crystalline portion of the overlayer increases with potential above 1.3 V versus RHE.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Simulation of the Impact of Point Defects and Edge Dislocations on X-Ray Diffraction in Hexagonal (Ni,Co) 1+2 x Ti 1– x O 3 Thin Films

In this work, a computer code for simulating high-resolution X-ray diffraction (XRD) data from disordered crystals with arbitrary spatial composition and local lattice parameters is developed. Simulated patterns are compared with the experimental data collected on a single phase, highly crystalline (Ni 0.42 Co 0.58 ) 2.22 Ti 0.39 O 3 solid-solution thin film exhibiting a large number of subsidiary minima. As a case study, the edge dislocations in hexagonal (Ni,Co) 3 O 3 thin films with Burgers vector parallel and perpendicular to the a-axis and c-axis, respectively, are modeled. No peak profiles are assumed and thus issues related to profile fitting are avoided. Both macroscopic features, such as film thickness, and atomic-scale structure, such as dislocations, are simultaneously modeled. Simulations are run on a desktop machine. Commonly applied database-based phase identification routines can result in wrong phase identification, unless intensities are properly modeled. Modeling tools of diffractometer manufacturers are compared with the present approach. An example of how simulated reciprocal lattice patterns can be used to choose relevant measurement geometries in defected thin films is given.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Electron Paramagnetic Resonance and X-ray Diffraction of Boron- and Phosphorus-Doped Nanodiamonds

Powders of boron- and phosphorus-doped detonation nanodiamonds and sintered pellets of non-doped nanodiamond powders were studied using electron paramagnetic resonance and x-ray diffraction. Doping of detonation nanodiamond crystals with boron and phosphorus was demonstrated to be possible. These methods could be used to diagnose diamond nanocrystals doped during shock-wave synthesis.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Crystal Structure of Hydrazinium Iodide by Neutron Diffraction

The structure of hydrazinium iodide, [H 5 N 2 ] + ·I - , at 100 K has monoclinic (P2 1 /n) symmetry from single crystal neutron diffraction with a = 7.4599(7) Å, b = 5.3185(6) Å, c = 10.1628(11) Å, β = 103.150(10)°, V = 392.64(7) Å 3 , Z = 4. The refinement converged to R = 0.0575, wR 2 = 0.1602, S = 1.022. Data for the crystal structure was collected on the SNS TOPAZ single-crystal time-of-flight Laue diffractometer. The compound has a one-dimensional structure which displays N–H···N hydrogen bonding. Finally, accurate intra- and intermolecular N–H distances have been determined.

36 MATERIALS SCIENCE↗

Three Dimensional Characterization of Defects by Ultrasonic Time-of-Flight Diffraction (ToFD) Technique

Ultrasonic time-of-flight diffraction (ToFD) technique has high accuracy in locating and sizing discontinuities. The primary reason for this accuracy is the use of time instead of amplitude for measurement of the depth and size of discontinuities. Despite the many advantages of ToFD, it suffers from a number of shortcomings, the most notable one being its two-dimensional character. The goal of this paper is to develop an algorithm, as a prerequisite, to extend ToFD measurements to a three-dimensional space. For this purpose, a combination of multiple transmitting and receiving probes is proposed instead of just one pair commonly used in ToFD measurements. The approach for locating and sizing defects in a 3D space follows the methods used in radar and acoustic positioning systems. Non-iterative techniques are used for positioning a single source (defect) based on signals collected by several transducers. The estimation formula, in the form of a closed-form solution, is derived by linear least-squares minimization. In addition to existing conventional passive algorithms, a new active algorithm is also proposed for the general arrangement of transducers. This algorithm is tested on a steel specimen having an artificially implanted discontinuity and the three-dimensional location of the defect is estimated.

42 ENGINEERING↗

Diffraction of Rayleigh Waves on a Compliant Inclusion in the Elastic Half Space

We consider a three-dimensional dynamical problem of diffraction of Rayleigh plane waves on a circular compliant inclusion in the elastic half space. To solve the problem, we use the method of boundary integral equations. The dynamical stress intensity factors in the vicinities of points of the contour of the inclusion are analyzed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Leontovich–Fock Parabolic Equation Method in the Neumann Diffraction Problem on a Prolate Body of Revolution

This paper continues a series of publications on the shortwave diffraction of the plane wave on prolate bodies of revolution with axial symmetry in the Neumann problem. The approach, which is based on the Leontovich–Fock parabolic equation method for the two parameter asymptotic expansion of the solution, is briefly described. Two correction terms are found for the Fock’s main integral term of the solution expansion in the boundary layer. This solution can be continuously transformed into the ray solution in the illuminated zone and decays exponentially in the shadow zone. If the observation point is in the shadow zone near the scatterer, then the wave field can be obtained with the help of residue theory for the integrals of the reflected field, because the incident field does not reach the shadow zone. The obtained residues are necessary for the unique construction of the creeping waves in the boundary layer of the scatterer in the shadow zone.

97 MATHEMATICS AND COMPUTING↗

To the Calculations of Scattering Amplitudes in Diffraction Problems for Elongated Bodies of Revolution

This paper is a complement to the article “Scattering amplitudes in a neighborhood of limit rays in short-wave diffraction by elongated bodies of revolution”. It contains discussions of some points of the article, which worth of more detailed considerations, such as the influence of the integration limits on the computation result of scattering amplitudes and the estimation of permissible values of scattering angle intervals as functions of parameters of the problems.

97 MATHEMATICS AND COMPUTING↗

Optical diffraction radiation from a dielectric and a metal nanowire excited by a modulated electron beam

The optical diffraction radiation that accompanies the motion of a modulated beam of electrons near a dielectric and silver nanowire scatterers is investigated in the two-dimensional formulation. Our goal is to compute the field in the near and far zones and analyze how it depends on electron beam parameters. We demonstrate the excitation of internal resonances of such a scatterer that can be useful in the design of nanoscale non-invasive beam position monitors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

The effect of dehydration on the position of cesium cations in the structure of CsNaFAU(Y) studied by powder X-ray diffraction and magic-angle spinning NMR spectroscopy

The influence of dehydration on the position of sodium and cesium cations obtained by ion exchange in the structure of FAU(Y) was studied by powder X-ray diffraction using synchrotron radiation and {sup 23}Na and {sup 133}Cs magic-angle spinning NMR spectroscopy. The sodium and cesium cations were found to be mobile in the hydrated samples. In dehydrated zeolites CsNaFAU(Y), cesium is predominantly localized in four crystallographic ion-exchange positions located in the large cavities and sodalite cages.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Structure of sp{sup 2}-carbon fiber prepared by high-temperature thermomechanical treatment of polyacrylonitrile fiber: a Raman and X-ray diffraction study

Structural regularities of the transformation of PAN fibers into high-strength sp{sup 2}-carbon fiber by high-temperature thermomechanical treatment were established using Raman spectroscopy and X-ray diffraction. Radial heterogeneity of the fiber structure was revealed and quantitatively characterized by Raman micro-mapping.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Chiral guest in a chiral framework: X-ray diffraction study

The inclusion compound of zinc lactate terephthalate with R-butan-2-ol, [Zn{sub 2}(R-Bu{sup s}OH) (bdc)(S-lac)]•(R-Bu{sup s}OH) (Bu{sup s}OH is butan-2-ol, H{sub 2}bdc is terephthalic acid, S-H{sub 2}lac is lactic acid), was prepared by soaking crystals of [Zn{sub 2}(dmf)(bdc)(S-lac)]•DMF in pure R-butan-2-ol. The positions of chiral alcohol molecules in voids of the chiral framework and the host–guest contacts were determined by X-ray diffraction. These data provide an explanation for the origin of chiral discrimination of zinc lactate terephthalate toward the R-isomer of butan-2-ol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Diffractive Hyperbola of a Skin Layer

Based on an analysis of physics of the phase transition from the quasistatic state field to the running wave field of elementary electric and magnetic dipoles located in absorbing media, it is concluded that the skin layer is formed at the boundary of this phase transition. The possibility is considered of obtaining the diffractive hyperbola of the skin layer and its subsequent application for sensing of objects in strongly absorbing media.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Three-Dimensional Model of Holographic Formation of Inhomogeneous PPLC Diffraction Structures

A three-dimensional theoretical model of holographic formation of inhomogeneous diffraction structures in composite photopolymer - liquid crystal materials is presented considering both the nonlinearity of recording and the amplitude-phase inhomogeneity of the recording light field. Based on the results of numerical simulation, the kinematics of formations of such structures and their spatial profile are investigated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

In Situ Neutron Diffraction Study of the Influence of Microstructure on the Mechanical Response of Additively Manufactured 304L Stainless Steel

In situ neutron diffraction measurements were completed for this study during tensile and compressive deformation of stainless steel 304L additively manufactured (AM) using a high power directed energy deposition process. Traditionally produced wrought 304L material was also studied for comparison. The AM material exhibited roughly 200 MPa higher flow stress relative to the wrought material. Crystallite size, crystallographic texture, dislocation density, and lattice strains were all characterized to understand the differences in the macroscopic mechanical behavior. The AM material’s initial dislocation density was about 10 times that of the wrought material, and the flow strength of both materials obeyed the Taylor equation, indicating that the AM material’s increased yield strength was primarily due to greater dislocation density. Finally, a ~50 MPa flow strength tension/compression asymmetry was observed in the AM material, and several potential causes were examined.

36 MATERIALS SCIENCE↗

Determination of γ/γ' Lattice Misfit in Ni-Based Single-Crystal Superalloys at High Temperatures by Neutron Diffraction

Constrained γ/γ' lattice misfit as a function of temperature (room temperature, 871 °C, 982 °C, 1093 °C, and 1204 °C) is measured by neutron diffraction on the first-generation Ni-based single-crystal superalloy René N4 and second-generation superalloys René N5, CMSX4, and PWA1484. All the alloys studied show negative misfit at temperatures above 871 °C. For René N4, René N5, and PWA1484, the misfit becomes less negative at temperatures above 1093 °C, possibly due to either the chemistry effect or internal stress relaxation. The magnitude of the misfit shows a qualitative agreement with Caron’s misfit model based on Vegard’s coefficients. The Re-free alloy René N4 was found to have a larger γ lattice parameter and γ/γ' misfit due to higher fractions of Cr, Ti, and Mo. After 100 hours of annealing at high temperatures, René N5 shows a more negative misfit than the misfit after the standard heat treatment.

36 MATERIALS SCIENCE↗