Journal of Applied Crystallography最新文献

A new procedure for determining the degree of crystallinity (DOC) has been recently proposed, and it has been verified using experimental and computer-generated powder diffractometry data [Toraya (2023). J. Appl. Cryst.56, 1751–1763]. As an application to real materials like engineering plastics, this procedure is here applied to the DOC determination of plate-like polyphenylene sulfide (PPS) samples, composited with crystalline and non-crystalline fillers. The coexistence of partially crystallized polymer with non-crystalline fillers in target materials makes it difficult to separate the non-crystalline part of the partially crystallized polymer. This problem is here solved by the inverse application of the direct derivation (DD) method for quantitative phase analysis (QPA). The intensity–composition (IC) formula used in the DD method can derive the weight fractions of the individual components from just the total sums of observed intensities and the chemical composition data for these components [Toraya (2016). J. Appl. Cryst.49, 1508–1516]. For the present purpose, the IC formula has been inversely applied to calculate the relative intensity ratios of individual components under the assumption that the chemical compositions and weight fractions of the respective components are known. The total halo intensity could then be separated into the non-crystalline part of the polymer and the non-crystalline filler. Analyzed results of PPS composites in four different DOCs are reported.

Analytical methods with wide field range and high spatial resolution are required to observe the distribution of the crystal structure in micro-regions undergoing macroscopic chemical reactions. A recent X-ray diffraction (XRD) imaging method combines XRD with an X-ray optical device such as a glass polycapillary consisting of a bundle of numerous monocapillaries. The former provides the crystal structure, while the latter controls the shape of the incident or diffracted X-rays and retains the positional information of the sample. Although reducing the monocapillary pore size should improve the spatial resolution, manufacturing technology challenges must be overcome. Here, an anodic aluminium oxide (AAO) film, which forms self-ordered porous nanostructures by anodic oxidation in an electrolyte, is applied as an X-ray optical device. The AAO film (pore diameter: 110 nm; size of the disc: 11 mm; and thickness: 620 µm) was fabricated by anodization in a mixture of oxalic acid and ethylene glycol. The film was incorporated into a laboratory XRD instrument. Compared with using a glass polycapillary alone, using a combination of a glass polycapillary and the AAO film improved the spatial resolution of the XRD imaging method by 40%. This XRD imaging method should not only provide practical analysis in a laboratory environment but also support various observations of the crystal structure distribution.

This study introduces silicon substrates with a switchable magnetic contrast layer (MCL) for polarized neutron reflectometry (PNR) experiments at the solid–liquid interface to study soft-matter surface layers. During standard neutron reflectometry (NR) experiments on soft-matter samples, structural and compositional information is obtained by collecting experimental data with different isotopic contrasts on the same sample. This approach is normally referred to as contrast matching, and it can be achieved by using solvents with different isotopic contrast, e.g. different H₂O/D₂O ratios, and/or by selective deuteration of the molecules. However, some soft-matter systems might be perturbed by this approach, or it might be difficult to implement, particularly in the case of biological samples. In these scenarios, solid substrates with an MCL are an appealing alternative, as the magnetic contrast with the substrate can be used for partial recovery of information on the sample structure. More specifically, in this study, a magnetically soft Fe layer coated with SiO₂ was produced by ion-beam sputter deposition on silicon substrates of different sizes. The structure was evaluated using X-ray reflectometry, atomic force microscopy, vibrating sample magnetometry and PNR. The collected data showed the high quality and repeatability of the MCL parameters, regardless of the substrate size or the thickness of the capping SiO₂ layer. Previously proposed substrates with an iron MCL used an Au capping layer. The SiO₂ capping layer proposed here allows reproduction of the typical surface of a standard silicon substrate used for NR experiments and is compatible with a large variety of soft-matter samples. This application is demonstrated with ready-to-use 50 × 50 × 10 mm substrates in PNR experiments for the characterization of a lipid bilayer in a single solvent contrast. Overall, the article highlights the potential of PNR with an MCL for the investigation of soft-matter samples.

Rotation axes (together with rotation angles) are often used to describe crystal orientations and misorientations, and they are also needed to characterize some properties of crystalline materials. Since experimental orientation data are subject to errors, the directions of the axes obtained from such data are also inaccurate. A natural question arises: given the resolution of input rotations, what is the average error of the rotation axes? Assuming that rotation data characterized by a rotation angle ω deviate from the actual data by error rotations with fixed angle δ but which are otherwise random, the average error of the rotation axes of the data is expressed analytically as a function of ω and δ. A scheme for using this formula in practical cases when rotation errors δ follow the von Mises–Fisher distribution is also described. Finally, the impact of crystal symmetry on the determination of the average errors of the axis directions is discussed. The presented results are important for assessing the reliability of rotation axes in studies where the directions of crystal rotations play a role, e.g. in identifying deformation slip mechanisms.