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Progress in the Development of a Systematic Nanoperiodic Framework for Unifying Nanoscience
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Donald A. Tomalia, Shiv N. Khanna
The quantized, structure-controlled properties observed for the atomic elements are widely recognized to produce discrete periodic property patterns at the picoscale level. The structure-controlled properties leading to these periodic trends have been referred to as critical atomic design properties (CADPs) (Tomalia, 2009, 2010; Tomalia et al., 1990). Within the context of Mendeleev’s periodic table, these vertical and horizontal periodic trends based on CADPs are as illustrated in Figure 18.8 (Scerri, 2007, 2011).
Structures and Reactions of Compounds Containing Heavier Main Group Elements
Published in Takayuki Fueno, The Transition State, 2019
The heavier atoms contain a large number of electrons, for which relativistic effects become also important.8) Large-scale calculations are generally required for systems of experimental interest. Recent progress in theoretical methods, efficient computer programs and powerful computers have greatly advanced the scope of applicability of ab initio calculations. However, it is important to have a simple conceptual framework before (and even after) extensive calculations. This is exactly the present purpose. In this context the concept of “hybridization” is most helpful for an intuitive and unified understanding of the essential difference in chemical bonding between the lighter and heavier main group atoms.5,9) The primary aim here is to provide systematic insight into the periodic trends of chemical properties of the heavier main group compounds. Since we are most familiar with carbon chemistry, emphasis is put on the heavier homologues (Si, Ge, Sn, and Pb) in group 14 and neighboring atoms (P, As, Sb, and Bi) in group 15.
Color in Metals and Semiconductors
Published in Mary Anne White, Physical Properties of Materials, 2018
When a semiconductor has Eg falling in the energy range of visible light, the color of the material depends on the exact value of Eg. The value of Eg depends on two factors: the strength of the interaction that separates bonding and antibonding orbitals, and the spread in energy of each band. Periodic trends in lattice parameters, bond dissociation energies, and band gap are summarized for one isostructural group of the periodic table in Table 3.1. The shorter, stronger bonds can be seen to give rise to larger values of Eg.
2018 Table of static dipole polarizabilities of the neutral elements in the periodic table*
Published in Molecular Physics, 2019
Peter Schwerdtfeger, Jeffrey K. Nagle
We turn now to a consideration of vertical (group) periodic trends in polarizabilities. For the Group 1 (Figure 4(a)) and Group 2 (Figure 4(b)) elements (s-block elements), polarizabilities increase with increasing period number n for the first six rows of the periodic table. The only exception to this behaviour is the slight decrease in polarizability of Na compared to Li, accounted for by the increased effective nuclear charge of Na due to its filled 2p6 subshell. For the last two rows, the polarizabilities decrease, a result of the large direct relativistic contraction and stabilisation of the 7s and 8s orbitals.
Experimental Study on the Influence of Gas-Solid Heat Transfer in a Mesoscale Counterflow Combustor
Published in Combustion Science and Technology, 2023
Patryk P. Radyjowski, Janet L. Ellzey
The apparatus consists of two major components: the AM core and the support equipment. Figure 2 shows the complete system, while Core design describes reactor core internal designs. The external equipment provides structural support, instrumentation, and flow-controlled premixed air-fuel delivery to the inlet pipe of the core element. This modular approach accommodates various AM printed cores exploring various geometric changes while minimizing external systems variability. The installed AM core rested on two zirconia insulation blocks on the narrow ends, with the hottest middle section suspended. The insulation is provided by a 2-inch-thick kaowool blanket wrapped around the suspended section. There are 18 N-type stainless-steel sheath thermocouples with the data acquired by a computer-based NI PCI-6225 system. Thermocouples are inserted from underneath, penetrating the kaowool and entering dedicated interface holes. The measurement oversampling enabled a 21-bit acquisition precision, which resulted in ±6.75◦C and ±11.5◦C for the 700◦C to 1400◦C reading range, respectively. Furthermore, only the wall temperature was measured to avoid the flame-holding effect of exposed thermocouples. Instead, all thermocouples were positioned flush with the bottom wall surface and inserted via dedicated holes. The exact positioning of thermocouples is dependent on AM core configuration, as explained in Core Design section. Thermocouples are distributed along the two middle channels, which are the least influenced by external heat losses. It is confirmed that the temperature profiles along the length of the measured channels are similar under normal operation. Hence, only a single, averaged profile is presented in this paper. Additionally, eight K-type thermocouples were attached to inlet pipes via ceramic adhesive to monitor inlet conditions. Thermocouple readings are used in the post-processing to establish the steady-state operation period, where the temperature variations are not showing any long-term non-periodic trends, and all variations are within the uncertainty range. The steady-state time window was identified based on this criterion, and a time-averaged temperature reading was recorded.