1998 Fiscal Year Final Research Report Summary
Molecular-level in-situ investigation of adhesion mechanism of colloidal particles
| Project/Area Number |
09450285
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | KYOTO UNIVERSITY |
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Principal Investigator |
HIGASHITIANI Ko KYOTO UNIV., CHEM.ENG., PROFESSOR, 工学研究科, 教授 (10039133)
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| Co-Investigator(Kenkyū-buntansha) |
KANDA Yoichi KYOTO UNIV., CHEM.ENG., INSTRUCTOR, 工学研究科, 助手 (60243044)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Atomic force microscope / Adsorbed layer / Adhesion force / Surface / Surface modification / Particle |
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| Research Abstract |
Interaction forces between a silica particle and a mica or silica plate are measured by using atomic force microscope. Following results are found :
<Adhesion force in non-aqueous media>
An extremely large adhesion force appears at a relative water concentration in alcohols as the water-soluble media. The similar results are found in other media having different hydrophilic group. It is considered that this adhesion force will be decided by the competition between the bridging force because of phase separation of water and the surface-active effect by media molecule itself. The result of molecular dynamics simulation has confirmed the existence of the big peak of adhesion force at a relative water concentration.
The adhesion force in alkane liquid increases extremely with existing trace amount of water and decreases with mixing alcohols by their surface-active effect. The addition of non-ionic surfactant of low HLB value invites similar results. For the surfactant of high HLB value, a lon
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g-range attractive force appears and there is a steric repulsion force by their adsorbed layer near the surfaces.
<Surface property and interaction force>
The attractive force appears even between little hydrophobic surfaces in surfactant aqueous solution but does not appear between modified surfaces until contact angle becomes over 80 degree. This difference will be due to not only the difference of domain structure of adsorbed layer but also the influence of surfactant.
A hysteresis appears in the measuring of interaction force between modified surfaces by using normal continuous mode but does not appear by the measuring of static method. This suggests that so-called hydrophobic interaction force will be due to a dynamic mechanism.
<Surface roughness>
Adhesion forces between mica plate and AFM probe, 4 mum silica particle or 9 mum, are similar magnitude each other. According to the investigation of AFM images, it is considered that the adhesion force will depend on rather the microscopic feature of the surface contacting each other than the macroscopic particle diameter. Less
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