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Full-Text Articles in Physical Sciences and Mathematics
Density Functional Study Of The Structure And Water Adsorption Activity Of An Al$_{30}$O$_{30}$ Star-Shaped Alumina Nanocage, Mehdi Zamani
Density Functional Study Of The Structure And Water Adsorption Activity Of An Al$_{30}$O$_{30}$ Star-Shaped Alumina Nanocage, Mehdi Zamani
Turkish Journal of Chemistry
Molecular and electronic structures of a novel Al$_{30}$O$_{30}$ star-shaped alumina nanocage (SANC) were studied using the recently developed CAM-B3LYP density functional method. Comparison of the stretching vibrational modes of this compound with the corresponding modes related to an Al$_{20}$O$_{30}$ perfect cage and Al$_{50}$O$_{75}$ tubular alumina nanomaterials showed a shift to lower frequencies, while the bending modes moved to higher frequencies. The highest occupied molecular orbital (HOMO) of the SANC had 65% nonbonding character, whereas the lowest unoccupied molecular orbital (LUMO) was 72% antibonding. The HOMO and LUMO of the SANC arose mostly from Al 3s and 2p atomic orbitals. The …
An Indirect Model For Sintering Thermodynamics, Yüksel Sarikaya, Müşerref Önal
An Indirect Model For Sintering Thermodynamics, Yüksel Sarikaya, Müşerref Önal
Turkish Journal of Chemistry
A model was proposed and used to calculated the changes in enthalpy $(\Delta H^{o})$, entropy $(\Delta S^{o}),$ and Gibbs energy $(\Delta G^{o})$, as well as equilibrium constant $(K)$ relating to the sintering of alumina compacts. Specific nanopore volume $(V)$ of the compacts was assumed as a thermodynamic variable. A hypothetical equilibrium constant $(K_{h})$ and corresponding Gibbs energy $(\Delta G_{h}^{o})$ were calculated depending on the $V$ value measured after each sintering. The thermodynamic relationships with the SI units were respectively evaluated for the initial-stage $(i)$ sintering between 1000 and 1200 $^{\circ}$C and final-stage $(f)$ sintering between 1200 and 1600 $^{\circ}$C in …