By employing dark-field X-ray microscopy (DFXM), a 3D imaging technique for nanostructures, the work investigates the potential in characterizing novel epitaxial gallium nitride (GaN) structures atop GaN/AlN/Si/SiO2 nano-pillars for potential use in optoelectronics. Independent GaN nanostructures are meant to coalesce into a highly oriented film using the nano-pillars as a medium, this being possible due to the SiO2 layer becoming soft at the GaN growth temperature. Different nanoscale sample types were examined using DFXM, yielding results that show extremely well-oriented GaN lines (standard deviation of 004) and highly oriented material over zones up to 10 square nanometers. This growth technique demonstrated notable efficacy. Using high-intensity X-ray diffraction at a macroscale, the coalescence of GaN pyramids demonstrates a misorientation of silicon in nano-pillars, suggesting the intended process of pillar rotation during coalescence. This growth strategy, crucial for micro-displays and micro-LEDs that necessitate minuscule, high-quality GaN islands, is impressively demonstrated by these two diffraction techniques. It also offers a novel avenue to enhance our understanding of optoelectronically essential materials at the highest possible spatial resolution.
Pair distribution function (PDF) analysis presents a valuable method for gaining a deep understanding of atomic scale structure in materials science. High spatial resolution structural information, from particular locations, is attainable from electron diffraction patterns (EDPs) using transmission electron microscopy; X-ray diffraction (XRD)-based PDF analysis, however, lacks this localized specificity. This research details a novel software instrument for periodic and amorphous structures, resolving several practical challenges in the computation of PDFs from EDPs. This program's key features encompass accurate background subtraction via a nonlinear iterative peak-clipping algorithm, seamlessly converting diverse diffraction intensity profiles into PDF format without any external software dependency. Furthermore, the present research investigates the consequences of background subtraction and the elliptical distortion of EDPs on PDF profiles. Analysis of atomic structure in crystalline and non-crystalline materials is facilitated by the dependable EDP2PDF software.
The critical parameters for thermal treatment, pertaining to template removal in an ordered mesoporous carbon precursor produced via a direct soft-templating procedure, were revealed through the utilization of in situ small-angle X-ray scattering (SAXS). Temporal analysis of SAXS data yielded the lattice parameter of the 2D hexagonal structure, the diameter of cylindrical mesostructures, and a power-law exponent describing interface roughness. Detailed information on the contrast changes and pore lattice order was derived from a separate analysis of the integrated SAXS intensity, specifically isolating Bragg and diffuse scattering components. Ten distinct thermal regions, observed during heat treatment, were analyzed, focusing on the prevailing mechanisms at play. Evaluating the influence of temperature and the O2/N2 ratio on the ultimate structure's formation, specific parameter ranges were pinpointed to achieve optimal template removal with minimal matrix disturbance. The results show that the final structure and controllability of the process are at their best when the temperature is between 260 and 300 degrees Celsius and the gas flow includes 2 mole percent oxygen.
Neutron powder diffraction was used to investigate the magnetic order of W-type hexaferrites, which were synthesized with varied Co/Zn ratios. While SrZn2Fe16O27 displays the usual uniaxial (P63/mm'c') magnetic ordering, a planar (Cm'cm') arrangement was found in the SrCo2Fe16O27 and SrCoZnFe16O27 compounds, deviating from the typical W-type hexaferrite pattern. Non-collinear terms were observed in the magnetic structure of each of the three tested samples. The shared non-collinear term in the planar ordering of SrCoZnFe16O27 and the uniaxial ordering in SrZn2Fe16O27 may be an indication of an impending alteration to the magnetic structure's configuration. Thermomagnetic measurements on SrCo2Fe16O27 and SrCoZnFe16O27 indicated magnetic transitions at 520K and 360K, respectively. These materials also showed Curie temperatures at 780K and 680K, respectively. In contrast, SrZn2Fe16O27 displayed a single Curie temperature of 590K without any observable transitions. By precisely regulating the Co/Zn stoichiometry in the sample, the magnetic transition can be modulated.
The crystallographic relationships between parent and child grains in polycrystalline materials undergoing phase transformations are typically described by (calculated or experimental) orientation relationships. This paper introduces a new technique for dealing with the complexities of orientation relationships (ORs), specifically concerning (i) estimating ORs, (ii) evaluating the fit of a single OR to the data, (iii) determining if a set of children originates from a common parent, and (iv) reconstructing the parent or grain boundaries. Bioethanol production An extension of the well-regarded embedding approach for directional statistics, this approach is situated within the crystallographic context. The method inherently produces precise probabilistic statements, being statistical in nature. Coordinate systems, explicit and defined, are not employed, and arbitrary thresholds are not used.
To achieve the definition of the kilogram by counting 28Si atoms, the measurement of silicon-28's (220) lattice-plane spacing using scanning X-ray interferometry is indispensable. The implication is that the measured lattice spacing is indicative of the bulk, unstrained crystal value forming the interferometer analyzer. While analytical and numerical studies of X-ray propagation in bent crystals exist, these suggest that the observed lattice spacing could potentially be attributed to the analyzer's surface. This comprehensive analytical model explains the operation of a triple-Laue interferometer with a bent splitting or recombining crystal, supporting both the results of these studies and experimental explorations facilitated by phase-contrast topography.
The thermomechanical processing applied during the manufacturing of titanium forgings frequently creates microtexture heterogeneities. Comparative biology Characterized as macrozones, these areas frequently measure millimeters in length. Grains with comparable crystallographic orientations contribute to lower resistance to the advancement of cracks. Since the link between macrozones and diminished cold-dwell-fatigue performance of rotating components in gas turbine engines was confirmed, efforts have been proactively dedicated to the classification and detailed characterization of macrozones. The electron backscatter diffraction (EBSD) technique, widely utilized for texture analysis, provides a qualitative macrozone overview; however, subsequent processing is vital for determining the boundaries and disorientation spread within individual macrozones. Current strategies frequently incorporate c-axis misorientation criteria, but this can occasionally lead to a wide disparity in disorientation values within a macrozone. A computational tool, developed and applied in MATLAB, automatically identifies macrozones from EBSD datasets using a more cautious approach that considers both c-axis tilting and rotation, as detailed in this article. Employing disorientation angle and density-fraction criteria, the tool enables macrozones detection. The clustering efficiency is shown to be valid using pole-figure plots, and the effects of disorientation and fraction, the key macrozone clustering parameters, are considered. This tool effectively addressed both the fully equiaxed and bimodal microstructures in titanium forgings.
Neutron imaging with phase contrast, employing a polychromatic beam and propagation-based phase retrieval, is showcased. This process allows for the visualization of specimens exhibiting minimal absorption distinctions and/or enhances the signal-to-noise ratio, which aids, for instance, Caerulein Measurements of time-varying phenomena. To illustrate the technique, a metal sample, nearly identical to a phase-pure object, and a bone sample with partially deuterated water-filled channels were utilized. Phase retrieval was used to process the results of polychromatic neutron beam imaging on these samples. Significant improvements in signal-to-noise ratios were observed for both samples. Furthermore, in the bone sample, phase retrieval facilitated the isolation of bone from D2O, proving critical for in situ flow studies. Deuteration contrast, eliminating the need for chemical enhancements, positions neutron imaging as a valuable supplementary technique alongside X-ray bone imaging.
Synchrotron white-beam X-ray topography (SWXRT) in back-reflection and transmission configurations was utilized to characterize two wafers from one 4H-silicon carbide (4H-SiC) bulk crystal, one cut from the segment close to the seed and the other from a segment close to the cap, to explore the growth-related dislocation formation and extension. Full wafer mappings, captured for the first time using a CCD camera system in 00012 back-reflection geometry, provided a detailed understanding of dislocation arrangements, encompassing dislocation type, density, and uniform distribution. Moreover, the method's resolution, comparable to that of conventional SWXRT photographic film, permits the identification of individual dislocations, including single threading screw dislocations, which manifest as white spots with diameters ranging from 10 to 30 meters. The examined wafers exhibited a similar dislocation pattern, implying a steady and consistent progression of dislocations during the crystal growth phase. A systematic study of crystal lattice strain and tilt in different dislocation configurations across selected wafer areas was performed using high-resolution X-ray diffractometry reciprocal-space map (RSM) measurements in the symmetric 0004 reflection. Variations in dislocation arrangement within the RSM corresponded to variations in diffracted intensity distribution, which was dependent on the dominant dislocation type and its density in each particular region.