The specific surface area reduction and pore size distribution coupled with N2 adsorption-desorption hysteresis isotherm were studied in the temperature range of 1400-1550¢J for periclase MgO powder having 0.1£gm in size and with face-centered cubic structure. The apparent activation energy of such a rapid coarsening-coalescence process for MgO powder was estimated as 181¡Ó3kJ/mol. The minimum temperature for sintering/coarsening/coalescence of submicron MgO particles was estimated to be near 1300¢J based on the extrapolation of steady specific surface area reduction rates to zero.
Pulsed laser ablation (PLA) of periclase MgO powders in water was conducted under Q-switch mode and specified water height and water depth (10 mm) for an accumulation time of 5 and 20 minutes at 10 Hz. Such a PLA process has successfully synthesized nanosized and protonated MgO particles from Mg(OH)2 and lamellar precusors, implying the three phases may co-exist at high pressure and temperature conditions upon dynamic shock loading. A significant internal compressive stress up to 10 GPa was built up for the MgO but not the readily relaxed Mg(OH)2 nanocondensates. The lamellae-derived Mg(OH)2 tended to undergo a dehydroxylation process to become MgO following a specific crystallographic relationship, i.e. lamellar basal layer parallel to Mg(OH)2(0001) and MgO(111). The minimum band gap of the colloidal solution of MgO/Mg(OH)2/lamellae was lowered to ca. 5.2eV after the PLA process.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0704112-155203 |
| Date | 04 July 2012 |
| Creators | Chen, Pei-Ru |
| Contributors | Shuei-Yuan Chen, Pouyan Shen, Dershin Gan, Ker-Chang Hsieh |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0704112-155203 |
| Rights | user_define, Copyright information available at source archive |
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