The effect of heating synthetic microcrystalline goethite at 60°, 80°, and 105°C was studied by X-ray powder diffraction, electron microscopy, weight-loss measurements, and Mössbauer spectroscopy. Heating led to no detectable changes in the unit-cell parameters or crystallite size (210, 150, and 170 Å in the [020], [110], and [120] directions, respectively), however, some of the X-ray diffraction lines were broadened due to an increase in microstrain in these crystallographic directions. The superferromagnetic transition temperature increased from 43° to 46°, 53°, and 54°C after heating to 60°, 80°, and 105°C, respectively, showing that the desorption of water from the surfaces led to an enhanced magnetic coupling among the crystallites.

The aging behavior of precipitation hardenable 17-4 PH stainless steel is studied by analyzing the changes in microstrain, crystallite size, and dislocation density derived from the modified Williamson–Hall (mWH) method and the Fourier analysis of XRD profiles. Aging treatment of this steel at 380, 430, and 480 °C for 0.5, 1, and 3 h durations leads to changes in the microstrain due to precipitation and substructural changes caused by dislocation annihilation. The microstrain estimated from the mWH method is dominated by the precipitate-induced effects. The influence of precipitates and dislocations on the mean squared strain 〈ε2(L)〉 are separated by fitting the variation of 〈ε2(L)〉 with an expression P0 + P1/L + P2/L2, where the parameter (P0)0.5 and P1 are shown to be related to the precipitate-induced and dislocation density-induced microstrain, respectively. The study shows that the XRD profile analysis can be used to separate the combined effects of precipitation and dislocation annihilation.

Crystal structure determination on the basis of powder diffraction data frequently involves the question how the given diffraction data with some appreciably hkl-dependent line broadening should be interpreted. In many cases, such line broadening may either: (i) reasonably well be reconciled with a certain high-symmetry structure model or (ii) with a variant of the former with lower symmetry crystal family, which frequently will give a somewhat better fit in Rietveld refinement. In this work, it is shown mathematically that symmetry reduction induced reflection spitting masked by other line broadening contributions, thus leading to some reflection splitting-induced line broadening, shows a similar hkl dependence as typically adopted for anisotropic microstrain broadening with respect to the high-symmetry structure. This implies that Rietveld refinement on the basis of the low-symmetry model (including typically isotropic line broadening) and on the basis of the high-symmetry model with anisotropic microstrain broadening can both lead to similar qualities of the fit. Hence, the refinement results for both possibilities should be carefully considered in combination with possibly available additional information (e.g. results of first-principles calculations) to arrive at adequate conclusions concerning the true symmetry of the material under investigation.

In present investigation, effect of modulation and machining parameters on deformation level of the chips produced during modulation assisted machining (MAM) has been studied. It is shown that disruption in tool-chip contact during modulation assisted machining helps in the formation of discrete chips. Size and shape of the particles produced in MAM can be controlled by varying modulation and machining conditions. Particulates of different shapes and sizes ranging from 100 µm to 5 mm with an aspect ratio of ~10 were produced using MAM. The morphology of the particulates produced was characterized by scanning electron microscope (SEM). Deformation in chip particulates was investigated using X-Ray diffraction. The crystallite size and internal strain in particulates were evaluated using Scherrer and Williamson-Hall methods respectively. The crystallite size of the particulates was found to decrease with decrease in their size, whereas internal strain in particulates was observed to increase with decrease in their size. Furthermore, the length of particulates was observed to decrease with an increase in the ratio of frequency of modulation (fm) to frequency of workpiece rotation (fw). However, the corresponding change in microstrain and crystallite size was insignificant with change in this ratio.

The nanostructural features of the gas-phase displacement reaction 2Mg(g)+SiO2→2MgO(s)+{Si}, where SiO2 is in the form of diatom shells were studied via X-ray diffraction and Fourier methods. Diatomaceous powder heated to 700 °C in a sealed graphite cell in the presence of Mg vapor formed MgO via a displacement reaction. Warren-Averbach analysis performed on samples reacted for different times showed an initial sharp MgO grain size distribution which broadened with time. New MgO crystallization was shown to occur until about 60 min, whereafter only MgO grain growth occurred. Median MgO crystallite size increased from 7.5 to 24.9 nm during this period, whereas microstrain decreased dramatically past 60 min annealing time.