Interaction forces between chemically modified hydrophobic surfaces evaluated by AFM-The role of nanoscopic bubbles in the interactions

Naoyuki Ishida, Ko Higashitani

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

The interaction forces between a hydrophobic silicon plate and a silica particle in an aqueous solution were investigated with an atomic force microscope (AFM). The surfaces were hydrophobized chemically by a silane coupling agent, and the hydrophobicity (contact angle θ) of the surfaces was varied. The interactions were long-ranged at θ > 90° with a discontinuous step appearing in the approaching and separating force curves respectively. The range and magnitude of the interaction were decreased with decreasing θ. On the other hand, the interactions at θ = 80° was unstable and no long-range attraction was observed. When the gas phase on the surfaces was removed by flushing organic solvents between the surfaces, the interactions became short-ranged at θ > 90°, and the interaction was described DLVO theory at large distances at θ = 80°. A large number of nano-size domain structures were found on the surfaces by tapping-mode AFM. These results imply that the bridging of nanobubbles is the main origin of the long-range force between chemically hydrophobized surfaces and that the size of the bubble has critical effect on the range and magnitude of the attractive force. The short-range interactions without bubbles were found to consist of an electrostatic repulsive force at larger distances and an attractive force, which was sufficiently longer-ranged than the van der Waals force, at smaller distance.

Original languageEnglish
Pages (from-to)719-725
Number of pages7
JournalMinerals Engineering
Volume19
Issue number6-8
DOIs
Publication statusPublished - May 2006
Externally publishedYes

Fingerprint

bubble
Microscopes
domain structure
Silanes
Van der Waals forces
Electrostatic force
Coupling agents
hydrophobicity
Silicon
Hydrophobicity
flushing
Silicon Dioxide
Organic solvents
silicon
Contact angle
aqueous solution
silica
Gases
Silica
gas

Keywords

  • Fine particle processing
  • Flotation kinetics
  • Surface modification

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Geochemistry and Petrology
  • Geotechnical Engineering and Engineering Geology

Cite this

Interaction forces between chemically modified hydrophobic surfaces evaluated by AFM-The role of nanoscopic bubbles in the interactions. / Ishida, Naoyuki; Higashitani, Ko.

In: Minerals Engineering, Vol. 19, No. 6-8, 05.2006, p. 719-725.

Research output: Contribution to journalArticle

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