Related Experiment Video
Updated: Jul 15, 2026
06:16
Fabrication of Spherical and Worm-shaped Micellar Nanocrystals by Combining Electrospray, Self-assembly, and Solvent-based Structure Control
Published on: February 11, 2018
Shear-induced structures formed during thixotropic loops in dilute worm-micelle solutions
Jorge Delgado1, Rolando Castillo
1Instituto de Física, Universidad Nacional Autónoma de México, PO Box 20-364, México DF 01000, Mexico.
Journal of Colloid and Interface Science
|April 10, 2007
Summary
This study reveals that the shear stress response of CTAB/NaSal/water systems depends on shear rate history during up-shear but not down-shear. Shear-induced structures form and persist, with down-shear behavior following an Arrhenius temperature dependence.
Area of Science:
- Rheology
- Soft Matter Physics
- Colloid Science
Background:
- Understanding the shear stress response of complex fluids like surfactant/salt/water systems is crucial for predicting their behavior under flow.
- Thixotropic behavior, characterized by time-dependent shear thinning, is common in such systems and requires detailed investigation.
Purpose of the Study:
- To investigate the shear stress response and thixotropic behavior of the CTAB/NaSal/water system at low concentrations.
- To analyze the influence of shear rate ramping on the formation and evolution of shear-induced structures.
- To develop models describing the up-shear and down-shear curves and extract key parameters.
Main Methods:
- Utilized strain thixotropic loops to study the shear stress response.
- Employed a transparent Couette cell to observe shear-induced structures via scattered light.
- Analyzed the dependence of stress response on ramping rate and temperature.
Main Results:
- Up-shear stress response is dependent on the ramping rate, indicating history dependence.
- Down-shear stress response collapses into a single curve, independent of ramping rate and system history.
- Shear-induced structures form during up-shear and persist until the shear rate reaches zero.
- A decay shear rate constant for down-shear curves was identified and shown to follow an Arrhenius temperature dependence.
Conclusions:
- The CTAB/NaSal/water system exhibits distinct behaviors during up-shear and down-shear processes.
- Thixotropic loops provide valuable insights into the microstructural evolution and flow properties of these systems.
- The observed Arrhenius temperature dependence of the decay shear rate constant offers a pathway for quantitative modeling and prediction.
More Related Videos
Related Concept Videos
01:30Micelles
Micelle formation is an intricate process that hinges on the properties of amphiphilic or amphipathic molecules and the conditions of the system in which they are found. Amphiphilic molecules, which have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, play a critical role in this process.In aqueous environments, these molecules arrange themselves such that their hydrophilic heads are turned towards the water phase, while their hydrophobic tails are oriented away...
03:22Colloids
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
01:15Thin-Walled Hollow Shafts
In analyzing a thin-walled hollow shaft subjected to torsional loading, a segment with width dx is isolated for examination. Despite its equilibrium state, this segment faces torsional shearing forces at its ends. These forces are quantitatively described by the product of the longitudinal shearing stress on the segment's minor surface and the area of this surface, leading to the concept of shear flow. This shear flow is consistent throughout the structure, indicating a uniform distribution of...
01:29The Colloidal State
The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...