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Diffraction
Published in Myeongkyu Lee, Optics for Materials Scientists, 2019
Electron diffraction is most frequently used to study the crystal structure and phase of solids. It makes use of the wave nature of electrons. The periodic structure of a crystalline solid acts as a diffraction grating, scattering the electrons in a predictable manner. The de Broglie postulate, formulated in 1924, predicts that particles should also behave like waves. De Broglie’s hypothesis was confirmed some years later with the observation of electron diffraction in two independent experiments by G. Thomson, C. Davisson, and L. Germer. Electron diffraction is usually carried out in a transmission electron microscope (TEM). The electrons in a TEM are accelerated to a velocity comparable to the speed of light. With a relativistic modification made, the electron wavelength is given by () λ=h[2moeV(1+eV2moc2)]−1/2.
Introduction
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
X-ray diffraction is an important technique commonly used to determine the crystal structure of metals, semiconductors, ceramics, polymers, and biological materials. There are other tools available for structural determination, such as neutron diffraction, electron diffraction, and scanning probe microscopy. We can perform neutron diffraction only at nuclear reactor facilities. Electron diffraction is useful for thin samples because of limited electron penetration and must be performed in vacuum. Scanning probe microscopy is applicable to surfaces only. x-ray diffraction can be conveniently applied under a wide range of environmental and ambient conditions.
In, Out, Shake It All About
Published in Sharon Ann Holgate, Understanding Solid State Physics, 2021
As electrons are scattered in air, electron diffraction experiments have to be carried out in a vacuum and in fact nowadays are performed inside electron microscopes. Being charged, electrons can only penetrate short distances into crystals before their energy is completely absorbed by their interactions with the atoms. This means electrons are generally used to study either surfaces or thin films. In fact, one important application of electron diffraction is in the electronics industry, where it is used to assess the surface structure of semiconductors. Two different set-ups are used for this, as we will see later.
Comparison between heat treatment and SPS treatment on CoCrFeMnNi/WC coatings
Published in Surface Engineering, 2022
Yicheng Zhou, Bing Yang, Guodong Zhang
The samples treated with SPS were cut by WEDM, and the microstructure and properties of the longitudinal section were analysed. CuKα radiation X-ray diffractometer (SmartLab, XRD) was used to analyse the elements and phases of the coating. Scanning electron microscopy (SEM) (MIRA 3, LMH, TESCAN Brno, S.R.O.) and its own Energy spectrum analyzer (EDS) (Aztec Energy ES, X-Max 20) are used to detect the microstructure and elemental composition. To further examine the microstructure, thin sheets were cut from the coating area, carefully ground to a thickness of about 50 μm, and then thinned by dual-jet electrolytic polishing. The microstructure of the coating was examined by transmission electron microscope (TEM) (JEM-2100F) operating at 200 kV, and the phase was analysed with selected area electron diffraction (SAED). Electron backscattering diffraction (EBSD) mapping was used to study the texture of the coating at 30 kV with a step size of 0.6–1.5 μm. The sample subjected to EBSD was used for nano-indentation test (Nanotest Vantage Micromaterials), a load of 100 mN was selected in Berkovich indenting mode and held for 2 s. In order to compare with SPS treatment, the specimen was placed in preheated oven, soaked at 1000°C temperature for 90 min and then air cooled to room temperature, according to the requirements of standard HT. And its microstructure and properties were tested simultaneously (called H90).
Effect of various technological parameters on particle morphology and uniformity of α-Ni(OH)2 synthesized via surfactant-free hydrothermal route
Published in Journal of Dispersion Science and Technology, 2021
Morphology of the prepared and calcined samples was examined through a scanning electron microscope (JSM-5910, JEOL). High resolution images and selected area electron diffraction (SAED) pattern was recorded with high resolution transmission electron microscope (JEM-2200FS, JEOL). Powder X-rays diffractometer (PANanalytical, X’pert PRO, Netherlands) with CuK∝ (1.54 Å) radiations source was used for assessing crystallinity of the test materials. Elemental analysis of the desired samples was carried out using energy dispersive X-ray spectrometer (INCA-200, Oxford). Diamond TG/DTA Perkin Elmer analyzer was used for the thermal analysis of the particles in air at heating rate of 5, 15 and 20 °C min−1. For functional group analysis, the samples were subjected to Fourier-transform infrared spectrophotometer (IR Prestige-21 FT-IR-8400, Shimadzu) in the wave number range of 400–4000 cm−1.
Many-beam dynamical scattering simulations for scanning and transmission electron microscopy modalities for 2D and 3D quasicrystals
Published in Philosophical Magazine, 2019
Saransh Singh, William C. Lenthe, Marc De Graef
We have presented models of electron diffraction modalities for 2D and 3D quasicrystalline phases. Higher dimensional crystallography combined with appropriate occupation domains for different atom types are employed in our model. Specifically, forward models for conventional transmission electron diffraction, convergent beam electron diffraction, electron backscatter diffraction and electron channelling are derived. Simulations of different diffraction modalities for realistic quasicrystal structures are presented and compared with experimental diffraction patterns. For the AlNiCo example considered in this paper, the differences between the quasicrystalline and approximant phases manifest themselves in the mutual information value, providing a potentially automated way to classify quasicrystalline and approximant phases based on their EBSD patterns. Furthermore, the predicted diffraction patterns show strong dynamical scattering effects, both in the transmission and scattering microscopy modes. The forward model is used in a dictionary-based method to perform automated orientation mapping for quasicrystals. These models can also be generalised to forward models for defect imaging modalities such as scanning transmission electron microscopy diffraction contrast imaging (STEM-DCI) and electron channelling contrast imaging (ECCI).