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Nanoparticles and Nanomaterials: An Update
Published in Devarajan Thangadurai, Saher Islam, Jeyabalan Sangeetha, Natália Cruz-Martins, Biogenic Nanomaterials, 2023
Anand Ishwar Torvi, Jeyabalan Sangeetha, Arun Kashivishwanath Shettar, Devarajan Thangadurai, Pradeep Rajole
Crystallography is the study of atoms and molecules arrangement in crystal solids. The crystallography of nanoparticles is carried out by a powder X-ray, electron, or neutron diffraction to determine the structural arrangement (Yano et al., 1996).
Introduction
Published in Dong ZhiLi, Fundamentals of Crystallography, Powder X-ray Diffraction, and Transmission Electron Microscopy for Materials Scientists, 2022
The structure–property relationship is one of the key topics in materials research. To understand crystal structure description, and know how to use the theories and methods to determine crystal structures, is important to materials scientists. In the traditional definition, crystals are considered as a periodic arrangement of identical unit cells or building blocks. However, as more and more materials with ordered but aperiodic structures are discovered and synthesized, such as quasicrystals, the crystallography communities classify crystals into periodic crystals and aperiodic crystals, both of which have sharp diffraction peaks (Janssen, 2007). In these lecture notes, I only explain the periodic crystal structure, and I still use the expression “crystal” to represent “periodic crystal”.
Electrical Characterization of Defects Introduced in Epitaxially Grown GaAs by Electron-, Proton- and He-Ion Irradiation
Published in Kazumi Wada, Stella W. Pang, Defects in Optoelectronic Materials, 2021
Defects in the crystal lattice are the consequence of the intentional or unintentional introduction of impurities or damage into the crystal structure. These imperfections introduce electronic states in the band gap which lie further away from the band edges than dopant levels, and these states are commonly referred to as “deep levels”. Deep level defects are present in all semiconductors in concentrations that depend on the semiconductor and the method by which it was grown and processed, and these deep levels affect the electronic properties of semiconductors. Sometimes deep level defects are intentionally introduced in order to modify a specific materials property. For example, it has been shown that radiation induced defects can be used to reduce the lifetime of carriers in Si [8, 9, 33], thereby enhancing the switching time of high frequency oscillators fabricated on it. The challenge in the area of radiation induced materials modification lies in innovative defect engineering through which the deleterious effects of defects can be avoided, and their beneficial effects harnessed to tailor the properties of materials and devices for specific needs and niche applications. Clearly, this requires an intimate knowledge of the properties and behaviour of defects.
Syntheses and structure characterization of seven inorganic-organic hybrids based on N-Brønsted bases and perhalometallates
Published in Inorganic and Nano-Metal Chemistry, 2021
Zhihang Li, Kaikai Hu, Weiqiang Xu, Shouwen Jin, Liqun Bai, Daqi Wang
One of the principal challenges of modern chemistry is that of the crystal engineering of new crystal structures. The ambition of this branch of crystal engineering is to design and prepare novel crystal structures based on molecular building blocks.[1–3] This is a considerable challenge given the immense difficulties of predicting a crystal structure from knowledge of its molecular components. A widely used approach is to exploit the principles of supramolecular chemistry to achieve desired modes of aggregation by well-known synthons.[4,5] Chemists have employed this strategy to create novel structures based on metal complex anions that accept H-bonds and organic cations with H-bond donor capability.[6–11] For this, much attention has been put on organic-inorganic hybrids from metal-halide anions.[12–15] The most typical cations in hybrid crystals were alkylammonium/aromatic ammonium.[16]
Effect of synthetic antioxidant-doped biodiesel in the low heat rejection engine
Published in Biofuels, 2023
Krishna Kumar Pandey, Murugan S
X-ray diffraction (XRD) is the most prominent technique for learning the nature of the materials that are either crystalline or amorphous. It is mostly used to conduct quantitative and qualitative analyses of crystalline-phase materials [35]. Crystalline materials provide the most valuable information on structures, crystal orientation, phases and other parameters like grain size, crystal defects, tension, and crystallinity [36]. Figure 5 shows the XRD pattern of the IPPD antioxidant. All diffractions (203), (800), (511), (512), (204), (513), (613), (214), (713), (415), (715) and (214) are indexed to the structure of IPPD and match well with the Joint Committee on Powder Diffraction Standards (JCPDS), card no. 98-011-6046 [37].
Thermal Transport in Disordered Materials
Published in Nanoscale and Microscale Thermophysical Engineering, 2019
Freddy DeAngelis, Murali Gopal Muraleedharan, Jaeyun Moon, Hamid Reza Seyf, Austin J. Minnich, Alan J. H. McGaughey, Asegun Henry
The taxonomy introduced by Allen and Feldman has provided insights into thermal transport in amorphous materials, and it can be expanded to encompass disordered materials more generally. Here, it does not matter whether the disorder is in the structure or the composition (i.e., strength of the interactions or masses), as any source of disorder in the LD dynamical matrix will affect the modes. In this way, it is useful to note that the changes in mode character/shape occur because of a break in symmetry. In a crystal, all atoms are arranged in a periodic fashion, and there is perfect periodicity in structure, composition and mass. It should be noted that the material does not have to be monatomic i.e., the same mass and species for every atom, as one can have a unit cell with more than one basis atom and still have all propagating modes. Even in such a situation, the normal modes of vibration for the atoms must be described by periodic functions, since no one unit cell in the material is distinguishable from any other. Thus, they must all exhibit the same vibrations as a natural consequence of the symmetry, since the equations of motion will be the same for every copy of the unit cell. However, whenever there is any break in symmetry, such that the dynamical matrix is no longer periodic, the break in symmetry must be reflected in the final solutions to the equations of motion. Thus, whenever any atom or unit cell becomes distinguishable from any or all others, either by experiencing a different atomic environment (e.g., it has different neighboring atoms, or they are located at different distances/angles), or the atom is of a different species (e.g., an alloying element or interstitial, or the atom or its neighbors have a different mass such as an isotope), or if there exist defects, interfaces or other deviations from a perfectly periodic crystal, a change in mode character/shape will be induced [71–75].