Browsing by Author "Moon, J"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- ItemDetermination of the elastic properties of amorphous materials: case study of alkali-silica reaction gel(Elsevier, 2013-12-01) Moon, J; Speziale, S; Meral, C; Kalkan, B; Clark, SM; Monteiro, PJMThe gel formed during Brillouin spectroscopy reaction (ASR) can lead to cracking and deterioration of a concrete structure. The elastic properties of the ASR gel using X-ray absorption and Brillouin spectroscopy measurements are reported. X-ray absorption was used to determine the density of the gel as a function of pressure, and the result yields an isothermal bulk modulus of 33 ± 2 GPa. Brillouin spectroscopy was applied to measure isentropic bulk (24.9–34.0 GPa) and shear moduli (8.7–10.1 GPa) of the gel. The range of values obtained is attributed to the variable composition of samples that were collected under field conditions. Results suggested that amorphous silica becomes expanded and compressible as it absorbs water molecules and alkali ions. This could explain high gel migration rates through the complex pore structures in concrete. © 2013, Elsevier Ltd.
- ItemUnderstanding ion transport phenomena in heterostructured yttria-stabilized zirconia with respect to coordination chemistry(International Conference on Neutron Scattering, 2017-07-12) Lee, D; Sterbinsky, G; Soon, A; Stampfl, APJ; Kim, J; Moon, JYttria-stabilized zirconia (xY -(1-x)ZrO , YSZ) has been exploited as a fast oxygen-ion conductor at elevated temperature, which is benefited from the formation of oxygen vacancies upon the stabilization of zirconia by yttria doping. Oxygen ion conduction in YSZ takes place by exchanging oxygen ions and vacancies within the cubic/tetragonal crystal framework, therefore, the coordination chemistry of a Zr ion by oxygen are of key importance in terms of crystal structure and crystal field to understand the origin of fast ionic conduction in YSZ. Herein, the Zr-Ometal-ligand interactions are modulated by heterostructuring of YSZ with Smdoped ceria, by which the vibrational properties of Zr-O bonding are altered.The coordination chemistry of the heterostructures is studied by X-ray absorption spectroscopy on Zr L edges, which is combined with neutron diffraction and inelastic neutron scattering studies. The coordination chemistry model for the heterostructures is suggested in conjunction with ab initio calculations.