2001 Fiscal Year Final Research Report Summary
Observation of Hydrothermal Synthesis of Metal Oxide Fine Particle in Supercritical Water by Diamond Anvil Cell
| Project/Area Number |
12650744
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
化学工学一般
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
SMITH Richard Lee Jr. Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (60261583)
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| Co-Investigator(Kenkyū-buntansha) |
INOMATA Hiroshi Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (10168479)
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| Project Period (FY) |
2000 – 2001
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| Keywords | HDAC / Hydrothermal synthesis / Phase equilibria / AlOOH / Pressure control |
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| Research Abstract |
The objective of this research was to develop a simple technique for measuring pressure for a hydrothermal diamond anvil cell (HDAC) and to use the technique with a HDAC to visually study formation of oxides in supercritical water.
Hydrothermal reaction of Al(NO_3)_3 in water was investigated at temperatures up to 421 ℃ and pressures up to 850 MPa with the diamond anvil cell system. A number of gelatinous phase transitions were observed that seemed to play a key role in boehmite (AlOOH) formation. At high Al(NO_3)_3 concentrations (0.32 M) and high densities (1060 kg/m^3), high pressure induced formation of a gel-like phase and the phase formed seemed to be much less reactive than solutions at lower densities (400 to 670 kg/m^3). At densities closer to the critical density of water, as heating occurred, the gelatinous material precipitated and redissolved into solution prior to intense precipitation around the apparent critical point. A model for the aluminum hydroxocomplexes in solution was developed that showed that cationic species were the main species present at high density conditions. Nitrate ion seemed to play a key role in the gel-like phase formation and boehmite particle production. We followed up on this with additional batch experiments and found that for the supercritical case, that nitrate does not form in the crystallized boehmite phase.
We found that boehmite nanocrystals can be prepared without nitrate impurities under supercritical hydrothermal conditions in contrast with the other results, which suggested that hydrothermally produced boehmites produced from nitrate starting materials were contaminated with difficult to remove nitrates.
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Research Products
(12 results)
