The introduction of artificial ±b/3 stacking faults into well-crystallized kaolinite by intercalating and removing hydrazine had no observable effect on the solid-state 29Si nuclear magnetic resonance spectrum of kaolinite. Also, the introduction of such stacking faults did not alter the hydroxyl-stretching region of the infrared spectrum, implying no change in the hydrogen bonding between the displaced layers. Calculations of Si...H distances and Si-O...H angles from reported structures for kaolinite indicated that the resolution of the two Si chemical environments was due to differences in hydrogen-bonding at the surface of the silicate sheet.

A comparative study is reported in which kaolinite has been hydrothermally synthesized at several pH conditions. The syntheses were carried out at 220 °C for 3 to 10 d with distilled water or acidic solutions using a mixture of silica-gel derived from alkoxide and gibbsite with a Si/Al ratio of 1:1 as the starting material. Use of acidic solution for the synthesis promotes the dissolution of the starting materials and leads to kaolinitization at an earlier stage of the reaction. However, the rate of kaolinitization is found to be rather slow, in comparison to the reaction with distilled water. The synthetic kaolinite was characterized by X-ray powder diffraction pattern. Kaolinite synthesized with distilled water was poorly grown for direction of the stacking. For example, crystallite size along the c*-axis = 155 Å, whereas kaolinite synthesized with acidic solution gave a higher crystallite size along the c*-axis, such as 253 Å in the case of the synthesis with 0.1 N HCl. Hinckley index of the synthetic kaolinite was varied from 0.35 to 0.80 by the acidity of the reaction. Different kaolinitization processes are implied by differences observed in the rate of kaolinitization, which has an influence on the nature of the stacking faults of the kaolinite.

Although structural disorder in kaolinite has been investigated extensively, it is still not understood properly. To investigate the problem, a kaolinite specimen of sedimentary origin from Capim, Brazil, was examined, mainly by transmission electron microscopy (TEM). Selected-area electron diffraction (SAED) along the Xi ([100], [110], and []) directions shows various features, from completely discrete patterns to heavily streaked ones along the c* direction, suggesting that the degree of stacking disorder is variable among individual grains. High-resolution TEM images indicate that stacking faults are mainly caused by disorder of alternating t1 (~ −a/3) and t2 (−a/3 +b/3) layer displacements. Furthermore, stacking faults have been observed (1) as isolated stacking faults (e.g. insertion of an isolated t2 `fault' in an ordered sequence with t1 layer displacement) and (2) as interstratification of two kinds of multilayer blocks having regular t1 and t2 layer displacements. A mixture of grains with various degrees and modes of disorder with alternating t1 and t2 layer displacements may explain the experimental profile of the 02, 11 X-ray diffraction band.

Faults related to displacement of the octahedral vacancy and/or to layer rotation were also observed in HRTEM images. The SAED patterns along the Yi ([010], [310], and []) directions occasionally have extra spots and/or streaks, suggesting the presence of stacking sequences with (±60°, 180°) mutual layer rotation and/or with (0, ±b/3) layer displacements. The local dickite or nacrite-like fragments formed by these faults are in qualitative agreement with recent low-temperature FTIR results from this sample, where distinct ν(OH) absorption bands reflect multiple interlayer O-H⋯O environments that are possibly ascribed to dickite and nacrite.

Group III nitrides are promising materials for light emitting diodes (LEDs). The occurrence of structural defects strongly affects the efficiency of these LEDs. We investigate the optical properties of basal plane stacking faults (BFSs), and the assignment of specific spectral features to distinct defect types by direct correlation of localized emission bands measured by cathodoluminescence in a scanning electron microscope with defects found in high resolution (scanning) transmission electron microscopy and electron beam induced current at identical sample spots. Thus, we are able to model the electronic structure of BSFs addressing I1, I2, and E type BSFs in GaN and AlGaN with low Al content. We find hints that BSFs in semipolar AlGaN layers cause local changes of the Al content, which strongly affects the usability of AlGaN as an electron blocking layer in nitride based LEDs.

Thermomechanical fatigue (TMF) tests have been carried out in a nickel-based single crystal TMS-82 superalloy, and the dynamic evolutions of dislocations and stacking faults have been studied in detail. It is found that the reversible formation of stacking faults is always associated with the loading orientation. Specifically, stacking faults expand under compression and shrink under tension due to the disappearance and appearance of dislocations during the TMF process. Stacking faults result from shear of γ′ precipitates by 1/3<112> dislocations, which arise from the decomposition of 1/2<110> matrix dislocations. The calculations of critically resolved shear stress to push dislocations that glide in the γ′ particles confirm the expansion of stacking faults under compression. However, under tension, dislocations in γ channel prevent 1/2<110> dislocations to enter γ′ cuboids and consequently, stacking faults shrink. Appearance and disappearance of dislocations during TMF cycling are associated with plastic deformation and annealing process, respectively.

Microstructures of 3C–SiC grown by chemical vapor deposition (CVD) technique on undulant silicon substrate and a further developed technique called switch-back epitaxy (SBE) were studied using transmission electron microscopy (TEM). In case of the CVD sample, the density of the stacking faults was found to be significantly decreasing along growth direction. Sites of collision of stacking faults were observed using high-resolution transmission electron microscopy. Some of the stacking faults were observed to have disappeared after colliding into each other. The stacking faults were identified to be on the same type of plane and had the same type of displacement vector not only in CVD and SBE but also in the epitaxial layer on the SBE SiC samples.