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Atomic Bonding and Crystal Structure
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
The crystal structure of an ionically bonded material is determined by the number of atoms of each element required for electrical neutrality and the optimum packing based on the relative sizes of the ions. The size of the ions is usually stated in terms of ionic radius. The ionic radius can slightly vary depending on the number and type of oppositely charged ions surrounding an ion. Table 4.1 shows ionic radii for ions with coordination numbers (CNs) of 4 and 6.1,2 A more extensive table of ionic radii is included at the end of the book. The CN or [n] is defined as the number of nearest neighbor atoms or ions surrounding an atom or ion.
Model Concepts for Air, Water, and Solids
Published in Ludwlg Luckner, Wsewolod M. Schestakow, German Migrationsprozesse, Migration Processes in the Soil and Groundwater Zone, 2017
Ludwlg Luckner, Wsewolod M. Schestakow, German Migrationsprozesse
The atomic or ionic radius controls the size of a chemical element [1.66, p. 742; 1.67, p. 56; 1.47]. The ionic radius r of an ion decreases as the positive charge increases. The following are characteristic examples (r in 1010− m):
Degradation mechanism of stainless steel by U-Zr-O molten mixture during core degradation of BWR severe accident
Published in Journal of Nuclear Science and Technology, 2021
Ayumi Itoh, Nathan C. Andrews, David L. Luxat, Randall O. Gauntt, Masaki Kurata, Yoshinao Kobayashi
Here, J/K is the Boltzmann constant and m is the ionic radius of metallic atom. Because the ionic radius depends on the coordination number or ionic valence, it is difficult to specify a unique value. Therefore, the value range was calculated taking a minimum and maximum ionic radius in Eq.5–6. Figure 10 shows calculated the value range of self-diffusion coefficient of liquid U, Zr and Fe. All the metals exhibit the value within 10−5 ~ 10−4 cm2/s at temperature range from 1500 to 2500 K. In this study, the constant value, 510−5 cm2/s, was given as the diffusion coefficient for all the metallic liquid components.
Photocatalytic removal of 2,4-Dichlorophenoxyacetic acid from aqueous solution using tungsten oxide doped zinc oxide nanoparticles immobilised on glass beads
Published in Environmental Technology, 2022
Yahya Zandsalimi, Afshin Maleki, Behzad Shahmoradi, Saeed Dehestani, Reza Rezaee, Gordon McKay
Table 2 shows the cell parameters and density of the nanoparticles. The cell parameters of the doped nanoparticles were smaller than those of the undoped zinc oxide. The reducing cell parameters could be attributed to the small size of tungsten ionic radius (0.6 angstrom). However, the density of the doped nanoparticles was higher than that of the undoped zinc oxide nanoparticles. New peaks were observed in the case of the doped ZnO nanoparticles, but a small displacement was observed in the peak location indicating the presence of tungsten [26]. The results of a study by Mojdi et al. on zinc oxide doped with manganese illustrated that the lattice constant in doped samples was higher and the density of the nanoparticles had fallen [27].
Influence of synthetic temperature on structural and magnetic properties of Dy substituted Ni nanoferrite
Published in Phase Transitions, 2023
Vikas S. Shinde, Ravindra N. Chikhale
As the sintering temperature increases from 400°C to 900°C the X-ray density increases. The decrease in lattice cell volume is responsible for the increase in X-ray density as molecular mass is constant for all samples. As the temperature increases from 700°C to 900°C lattice constant change was found to be very small in NiFe1.95Dy0.05O4 nanoparticles. The substituted Dy3+ ion having an ionic radius of 0.99 nm replaces the Fe3+ ion having an ionic radius of 0.67 nm in the octahedral site. As the concentration of Dy3+ ions is small, this change in the lattice parameter is also very small. Due to this increase in lattice position, the higher intensity (311) peak shifted towards the lower 2θ angle [45].