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The Structure of Solids
Published in Joseph Datsko, Materials Selection for Design and Manufacturing, 2020
The smallest particles that must be considered in the above context are atoms. The manner in which atoms are arranged in a solid material determines its crystal structure. The crystal structure and the type of interatomic bonding forces determine the strength and ductility of the material.
An Introduction to Crystal Structures
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
To understand the solid state, we need to have some insight into the structure of simple crystals and the forces that hold them together, so it is here that we start this book. Crystal structures are usually determined by the technique of X-ray crystallography. This technique relies on the fact that the distances between the atoms in the crystals are of the same order of magnitude as the wavelength of X-rays (of the order of 1 Å or 100 pm): a crystal thus acts as a three-dimensional diffraction grating to a beam of X-rays. The resulting diffraction pattern can be interpreted to give the internal positions of the atoms in the crystal very precisely, thus defining interatomic distances and angles. (Some of the principles underlying this technique are discussed in Chapter 2, where we review the physical methods available for characterising solids.) Most of the structures discussed in this book would have been determined in this way.
Crystalline Structure of Metals
Published in Zainul Huda, Metallurgy for Physicists and Engineers, 2020
Ideally, a crystal is a repetition of identical structural units in a three dimensional space. A unit cell is the smallest repeating pattern of atomic arrangement in a crystal structure. A lattice refers to the periodicity in the crystal. The terms “crystal lattice” and “crystal structure” may be used interchangeably. A unit cell can be described in terms of the lengths of three adjacent edges (a, b, and c) and the angles between them (α, β, and γ) (see Figure 2.2).
Characterization of the chemical shift and asymmetry indices of praseodium, neodymium, samarium, gadolinium, and terbium compounds by wavelength dispersive X-ray fluorescence (WDXRF)
Published in Instrumentation Science & Technology, 2023
Sevil (Porikli) Durdağı, Fatma Güzel
Atoms, molecules, or ions that are periodically arranged are said to be in a crystal structure. When the coordinates of the atomic centers are marked in space, a lattice structure consisting of repeating point clusters is formed that is known as the crystal lattice. The repeatability of point meshes results in simple geometries called unit cells that are used for descriptions. The types of unit cells include cubic, hexagonal, monoclinic, orthorhombic, rhombohedral, tetragonal, and triclinic. Table 2 shows that Nd2(CO3)3.xH2O is oriented in a symmetrical orthorhombic structure based on the L transitions, while NdCl3 is in asymmetrical trigonal prismatic structure. The X-ray emission lines of the hexagonal Nd2O3 and Nd2(C2O4)3 suggest asymmetrical structures.
Effect of concentrated solar radiation on the morphology of the silver nanoparticles and its antibacterial activity
Published in Indian Chemical Engineer, 2019
Sai Krishna C. Sastry, Nilesh L. Jadhav, Sarjerao B. Doltade, Dipak V. Pinjari
X-Ray Diffraction study was done to find out the crystal structure. The synthesised nanoparticles were loaded on the XRD grid. Figure 8 is an overlay of x-ray diffraction pattern of PVP-Ag NPs. All the samples had peaks at nearly the same 2- theta angle. For sample yellow paper, the reflections from (111), (200), (220) and (311) planes resulted in peak formations at 2θ = 37.8°, 43.9°, 64.1° and 72.4°. This data divulges that the synthesised nanoparticles are Ag NPs and are crystalline in nature. All the samples had FCC (Face-Centred-Cubic) lattice structure. The values are in accordance with the JCPDS (Joint Committee on Powder Diffraction Standard) file No. 04-078. Synthesised PVP-Ag NPs samples, were subjected to FTIR spectroscopy. The FTIR peaks are the testimony that the product has a PVP coating. In Figure 9, the peaks at 1633 and 1701 cm−1 depicts the amide bonding which is present in PVP. The peak at 1417 cm−1 indicates the CH2-CH2 bonding present in the aromatic ring of PVP. The peak at 736 cm−1 indicates the aliphatic chain which persists in PVP. The peaks coincided with the previous study in which PVP-Ag NPs were synthesised via thermal reduction and chemical reduction methods [20].
Performance of AlTiBN and AlTiTaN coatings during milling of titanium
Published in Surface Engineering, 2018
J. Y. Yi, K. H. Chen, Y. C. Xu, C. J. Zhu
The nanohardness of the coatings was tested by a CSM nano-hardness tester. The scratch-adhesion test employed a CSM scratch-measurement system, using an indenter with a tip radius of 50 μm. The load rate was 25 N/min and total scratch length was 2 mm. The morphologies, together with the components of the coatings, were studied by scanning electron microscope (SEM). The chemical compositions of the coatings were determined using electron probe microanalysis (EMPA). The crystal structures were identified by means of X-ray diffraction (XRD). The measurements were performed using Cu Kα-radiation in the ω/2θ mode for all samples. In order to test the oxidation resistance behaviour of the coating, the coated polycrystalline Al2O3 substrates were treated using a tube furnace in ambient atmosphere.