The role of long-range forces in the formation of thin liquid films on metals
White-light multiple beam interference is used to study the drainage of aqueous electrolytes from vertically optically smooth platinum and gold plates. Bulk liquid is in contact with the bottom of the metal plate. For short times following the lowering of the bulk liquid level, the change in the film profile agrees with that expected from viscous drainage. However, at long times, the film profile deviates from that expected and eventually becomes independent of time at a thickness between 0.08 and 0.25 micrometers. These profiles are best represented by a function dependent on the inverse cube root of height. The thickness of the equilibrium film profiles with increasing electrolyte concentration. A model based on long range van der Waals interactions resulting in a repulsive force between the interfaces of the film is shown to predict the correct profile shape, and for dilute electrolytes, the correct film thickness. This model also predicts increasing film thickness for increasing electrolyte concentration. The strength of this interaction is characterized by the Hamaker constant which can be calculated from the dielectric functions evaluated at imaginary frequencies of the film and substrate. For metals, this function is generated from spectral absorption data, limiting behavior for low and high frequencies, and by use of the Kramers-Kronig transformation. Hamaker constants calculated from the dielectric functions generated in this manner agree well with those derived from film profiles for dilute electrolytes.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6165082
- Report Number(s):
- LBL-23698; ON: DE87014133
- Resource Relation:
- Other Information: Thesis (Ph.D.). Portions of this document are illegible in microfiche products. Thesis submitted by Gyory, J.R
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
42 ENGINEERING
AQUEOUS SOLUTIONS
DRAINAGE
ELECTROLYTES
LIQUIDS
THIN FILMS
ELLIPSOMETRY
GOLD
LAYERS
METALS
PLATES
PLATINUM
SURFACE TENSION
THICKNESS
VAN DER WAALS FORCES
DIMENSIONS
DISPERSIONS
ELEMENTS
FILMS
FLUIDS
MEASURING METHODS
MIXTURES
PLATINUM METALS
SOLUTIONS
SURFACE PROPERTIES
TRANSITION ELEMENTS
640400* - Fluid Physics
420400 - Engineering- Heat Transfer & Fluid Flow