Papers by Keyword: Line Profile Analysis

Abstract: TiO₂-based nanotubes are a very promising material with many applications in solar cells, biomedical devices, gas sensors, hydrogen generation, supercapacitors, and lithium batteries, among others. Nanotube thickness is a very important property since it is related to electronic and surface mechanics. In this sense, transmission electron microscopy (TEM) can be used. However, it can be difficult to acquire a good TEM image because the transversal section of the nanotubes needs to be visible. In this work, TiO₂-based nanotubes obtained via hydrothermal synthesis were studied using X-ray line profile analysis. Scherrer and Single-Line methods provided consistent results for the thickness of the nanotubes (≃ 5 nm) when compared with TEM. Additionally, Single-Line method was also applied to estimate the microstrain. The advantage of using XRD is given by the fact that it is a quick and statistically significant analysis when compared with TEM. The results show that XRD can be used as a rapid and reliable alternative for the thickness estimation of nanotubes.

Abstract: X-ray line profile analysis was performed to evaluate the microstructural characteristics of low-cycle fatigued austenitic stainless steel, AISI 316. Strains were frequently applied to the specimens with three levels of the total strain ranges, 0.01, 0.02, and 0.03. The dislocation densities at the number of cycles for each strain condition were obtained by X-ray line profile analysis. In the case that the strain range was small, that is Δε = 0.01, dislocation densities were slightly increased until 53% of life time with the cycles, and then decreased. In the case that the strain ranges were 0.02 and 0.03, the dislocation densities were steeply increased during the first stage of the life time until around 10%. However, the variations after n/N_f ≃ 10% were different each other. In the case of Δε = 0.02, dislocation density did not increase significantly until the end of the life. But in the case of Δε = 0.03, the dislocation density monotonously increased until the end of the life. These tendencies agreed with the variations of stress amplitude. The relationship between dislocation density and stress amplitude could be expressed as Δσ/2 = 1.14ρ^1/2 + 207 (Δσ [MPa], ρ^1/2 [m⁻²]).

Abstract: Microstructure and residual stress in AISI316 stainless steels processed via shot peening (SP) and laser peening (LP) were evaluated using X-ray line profile analysis and residual stress measurements. Although both specimens exhibited similar compressive residual stress profiles in the depth direction, the dislocation density in the SP specimen was greater than that in the LP specimen, while the crystallite size in the SP specimen was less than that of the LP specimen. Thus, the variation in the microstructural features in the samples subjected to the two processes differed.

Abstract: Patterns calculated by applying the Debye function to faulted spherical nanoparticles are used to test the accuracy of modern Line Profile Analysis theory of faulting for small crystallites. The relative deviation of the determined fault density is found to be dependent on the fault position, and on the particle size. The study of the average pattern from systems of 100 particles (D = 9.8nm) shows an overestimated deviation of the determined fault density by as much as 30%.

Abstract: Recent advances in Line Profile Analysis of powder diffraction patterns must be paralleled by increasing attention to the quality and quantity of experimental data. The analysis of simulated data with different noise levels demonstrates the importance of statistical quality to reveal fine details of interest in the analysis of nanocrystalline materials, like the crystallite shape. It is also shown how synchrotron radiation diffraction can improve data quality with respect to laboratory measurements, both in terms of statistical quality and in terms of accessible information.

Abstract: Uniaxial deformed fcc metal samples have been studied by diffraction peak profile analysis. A method that can explain changes in broadening of different peaks by use of a Taylor model has been investigated. It was found that the method qualitatively describes the changes in broadening in nickel and stainless steel samples. It is argued that the differences between predictions and measurements are a feature of how the different samples deform at the microstructural scale.

Abstract: The basics of the Whole Powder Pattern Modeling and its implementation in the PM2K software are briefly reviewed. The main features and functionalities, and most common line broadening models are introduced with the aid of working examples related to the instrumental profile and to a plastically deformed metal. A summary of the main expressions is reported in the appendix, together with a list of useful references.

Abstract: Whole Powder Pattern Modeling (WPPM) is especially useful to study line defects in powder and polycrystalline materials. As a result of recent progresses in this field, dislocation studies can be carried out for any slip system and crystal symmetry of the studied phases. Basic theory and procedures are described with the help of some representative cases of study. The use of the dislocation-related broadening in the PM2K software implementing the WPPM approach is shown with practical examples.

Abstract: The implementation of a physically-sound size broadening model for peak profiles in the Rietveld method is presented. TOPAS macros are provided and the results compared with analogous modelling performed according to advanced analysis methods such as the Whole Powder Pattern Modelling.

Abstract: The recent evolution of powder diffraction line profile analysis toward full pattern methods is discussed. Specific reference is made to the Whole Powder Pattern Modelling (WPPM), as applied to metals and ceramics subjected to strong plastic deformation. Examples concerning three different materials science studies are shown to illustrate features and potentialities of the WPPM approach.