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The Contribution of Synchrotron X-Ray Powder Diffraction to Modern Zeolite Applications: A Mini-review and Prospects
Abstract not provided
Magnetization distribution in Cu 0.6 Mn 2.4 Ge 2 ferromagnet from polarized and non-polarized neutron powder diffraction aided by density-functional theory calculations
The crystal structure and magnetic properties of Cu 0.6 Mn 2.4 Ge 2 have been re-investigated by a combination of extensive magnetic measurements and neutron scattering experiments, aided by electronic structure calculations. The material is found to be a soft ferromagnet with the ordering temperature T C = 316 K. The magnetocaloric effect evaluated from field-dependent magnetization isotherms is equal to 1.2 J/(kg·K) and 2.5 J/(kg·K) under the maximum applied magnetic field of 2 T and 5 T, respectively. The compound crystallizes in the hexagonal space group P6 3 /mmc. A complex structural disorder necessitated testing of several disorder models against the results of non-polarized and polarized neutron scattering experiments and magnetization measurements. Simulations at the density-functional theory level were also performed to identify the most robust solution that properly described the data observed. The final magnetic structure model reveals non-equal magnetic moments on the Mn1 and Mn2 atoms (2.29(9) µ B and 2.7(1) µ B , respectively) and the presence of vacancies and minor Cu substitution defects in both Mn sites. The work demonstrates how the non-polarized and polarized neutron scattering methods can be combined with electronic structure calculations to establish the microscopic structure of magnetic materials with complex crystallographic disorder.
Fractional densities and character of dislocations in different slip modes from powder diffraction patterns
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Structural analysis of PrBaMn2O5+δ under SOFC anode conditions by in-situ neutron powder diffraction
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Assessment of firing conditions in old fired-clay bricks: The contribution of X-ray powder diffraction with the Rietveld method and small angle neutron scattering
Full characterization of fired-clay bricks is crucial for the improvement of process variables in manufacturing and, in case of old bricks, for restoration/replacement purposes. To this aim, five bricks produced in a plant in Czech Republic in the past have been investigated with a combination of analytical techniques in order to derive information on the firing process. An additional old brick from another brickyard was also used to study the influence of different raw materials on sample microstructure. The potential of X-ray diffraction with the Rietveld method and small angle neutron scattering technique has been exploited to describe the phase transformations taking place during firing and characterize the brick microstructure. Unit-cell parameter of spinel and amount of hematite are proposed as indicators of the maximum firing temperature, although for the latter, limited to bricks produced from the same raw material. The fractal quality of the surface area of pores obtained from small angle neutron scattering is also suggested as a method to distinguish between bricks produced from different raw clays. - Highlights: • Rietveld method helps in describing microstructure and physical properties of bricks. • XRPD derived cell parameter of spinel is proposed as an indicator of firing temperature. • SANS effectively describes brick micro and nanostructure, including closed porosity. • Fractal quality of pore surface is proposed as ‘fingerprint’ of brick manufacturing.
Describing the Influence of Ball-milling on the Amorphization of Flubendazole Using the PDF and RMC Methods with X-ray Powder Diffraction Data
Flubendazole (FBZ) is a poorly water-soluble drug, and different methodologies have been proposed to improve its oral bioavailability. Obtaining the amorphous drug phase is an alternative to improve its water solubility. Several techniques for drug amorphization, such as spray drying, lyophilization, melt quenching, solvent-evaporation, and ball milling, can yield various types of structural disorder and possibly render variations in physicochemical properties. Herein, we focus on evaluating the influence of the ball-milling process on the amorphization of FBZ. The characterization of the average global and local structures before, during, and after the milling process is described by sequential Rietveld refinements, pair distribution function analysis, and the Reverse Monte Carlo method. In conclusion, we show that preserving the local structure (nearest molecules) can be responsible for avoiding the fast structure recrystallization commonly observed when using the solvent-evaporation process for the studied drug.
Some further considerations in powder diffraction pattern indexing with the dichotomy method
Abstract not provided
A practical guide to pharmaceutical analyses using X-ray powder diffraction
Abstract not provided
Robust Nanostructure from High Throughput Powder Diffraction Data
Modern materials under study for next generation technologies in energy conversion and storage, environmental remediation, and health are highly complex, often heterogeneous and nano-structured. Here we refer to these as real materials.
Redox Properties of Hexagonal and Cubic Sr 0.4 Ba 0.6 Mn 0.94 Ti 0.06 O 3−δ Investigated by In Situ Neutron Powder Diffraction
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Ab initio structure solutions from nanocrystalline powder diffraction data via diffusion models
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Calculations of single crystal elastic constants for yttria partially stabilised zirconia from powder diffraction data
Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.