Forces between crystalline alumina (sapphire) surfaces in aqueous sodium dodecyl sulfate surfactant solutions

Journal Article · Wed May 01 04:00:00 EDT 1996 · Langmuir

DOI:https://doi.org/10.1021/la950939b· OSTI ID:252931

Xu, Z ^[1]; Ducker, W ^[2]; Israelachvili, J ^[3]

---

1. McGill Univ., Montreal (Canada)
2. Univ. of Otago, Dunedin (New Zealand)
3. Univ. of California, Santa Barbara, CA (United States)

Using the surface forces apparatus, we have studied the adsorption of negatively charged sodium dodecyl sulfate (SDS) surfactant onto positively charged surfaces of Al{sub 2}O{sub 3} and the resulting interactions between these surfaces in aqueous solutions. The adsorbed layer thicknesses, adhesion forces, and long range colloidal interactions were measured at SDS concentrations from 0.01 to 5 mM (below the critical micelle concentration, cmc = 8 mM). Our results show that an SDS bilayer of thickness approximately 3.2 nm forms at bulk concentrations above 1 mM (>=1/10(cmc)) and that beyond bilayer-bilayer contact the measured forces are well described by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory (with a constant surface potential at low surfactant coverage and constant surface charge density at high coverage). With one exception, the results are in good agreement with previous data on similar systems obtained using other techniques. The results clarify how electrostatic binding interactions determine the stepped adsorption of, and transitions between, hydrophobic and hydrophilic surfactant layers. The results also provide a basis for understanding why certain surfactants (under appropriate solution conditions) can be used as effective additives in the colloidal processing of ceramic materials. 27 refs., 7 figs., 1 tab.

• OSTI ID: 252931
• Journal Information: Langmuir, Journal Name: Langmuir Journal Issue: 9 Vol. 12; ISSN LANGD5; ISSN 0743-7463
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
ADSORPTION
ALUMINIUM OXIDES
AQUEOUS SOLUTIONS
CHEMICAL BONDS
MICELLAR SYSTEMS
PROCESSING
SAPPHIRE
SODIUM COMPOUNDS
SURFACTANTS
THIN FILMS