1987 Fiscal Year Final Research Report Summary
Chemical Engineering Aspects of Production of Extremely Fine Particles by Liquid-Phase Reactions
| Project/Area Number |
61550705
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
化学工学
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| Research Institution | Kyoto University |
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Principal Investigator |
KUMAZAWA Hidehiro Faculty of Eng., Kyoto Univ.・Associate Professor, 工学部, 助教授 (70023281)
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| Co-Investigator(Kenkyū-buntansha) |
SADA Eizo Faculty of Eng., Kyoto Univ.・Professor, 工学部, 教授 (60023024)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Particle size and shape control / Goethite / Needle-like shape crystal / Magnetite / Alkoxides / Hydrolysis / Silica / チタニア |
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| Research Abstract |
The formation of goethite particles by air oxidation of alkaline suspensions of Fe(OH)_2 was carried out using two types of bubble columns. The formation of goethite particles is composed of the formation step of ferric hydroxo-complex by oxidation of HFeO_2,the formation step of goethite by hydrolysis of the ferric hydroxo-complex, and the deposition step of goethite particles. The oxidation reaction has been found to complete in the liquid filmaround the gas bubble, while the formation of goethite has been found to mainlyoccur in the bulk liquid phase. The oxidation reaction was apparently zero-order with respect to Fe(II) and first-order with respect to dissolved oxygen. The prepared goethite particles are needle-like shapes whose size ranges from 0.15 to 0.30 <micrn>m. As the oxidation reaction rate increases, the meansize of the needle-like particles becomes small and the size distribution becomes sharp.
The hydrolysis of teraethyl orthosilicate (TEOS; Si(OC_2H_5)_4 in ethanol to p
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roduce spherical silica particles, was performed using a strred vessel. This reaction system was selected because the information on reaction kinetics was essential to establishment of the methodology of particle size and shape control. The formation of spherical silica particles is composed of hydrolysis and polycondensation. The polymerization reaction was found to be first-order in TEOS, NH_3 as a basic catalyst and H_2O, respectively. In the earlier stage of reaction, hydrolysis of TEOS takes place and very fine particles of nearly uniform size (host particles) are deposited. Successively, spherical particles are grown by further deposition of silicate monomer on the surface of the host particles while the number of the host particles is kept constant. The mean particle diameter can be controlled in the range of 0.03 to 0.30 <micrn>m, keeping the isze distribution narrow by changing the concentration of NH_3. Larger sperical particles can be prepared in different solvents such as acetone and dioxane. Spherical titania fine particles are also formed by controlled hyddrolysis of Ti(OC_2H_5)_4 in the similar mechanism and kinetics. Less
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Research Products
(4 results)
