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Identifier

000465954

Title

Colloidal gels tuned with magnetic field

Alternative Title

Αλλάζοντας τις μηχανικές ιδιότητες κολλοειδών πηκτωμάτων μέσω μαγνητικού πεδίου

Author

Μαθιουδάκης, Εμμανουήλ

Thesis advisor

Πετεκίδης, Γεώργιος

Reviewer

Βλασσόπουλος, Δημήτριος
Benoit Loppinet

Abstract

Colloidal gels are a class of soft materials. They are characterized as functional materials that exhibit solid-like properties through the formation of a network formed by interconnected colloidal particles dispersed within a medium. Due to their distinctive structural and mechanical properties, these materials have become increasingly relevant for applications in food science, pharmaceuticals and materials engineering. Magnetorheological Fluids (MRFs) are a class of smart colloidal materials, with a variety of applications, such as shock absorbers, that upon the application of an external magnetic field, exhibit a rapid and reversible transition from liquids to soft yield stress solids with columnar and ring structures being formed. Their mechanical properties and microstructure can be studied with the use of rheology and optical microscopy/imaging or scattering. Fumed silica particles have uses in many industry and everyday applications such as raw materials for the effects of purity composition in optical fibers, as rheological additives for anti-sedimentation, for personal care products, adhesives sealants and many more. They also function as effective thickening and thixotropic agents that can stabilize and modify the rheological response of a variety of systems, while based on the grade of fumed silica, hydrophobic or hydrophilic, and the chemical nature of the solvent, polar or non-polar, can form stable sols or gels with space-filling network and varying mechanical properties. By combining these two classes of materials we create a colloidal gel mixture to probe the rheological behavior and structure formation of the magnetic particles inside the fumed silica suspensions (gels or sols). Moreover, the mechanical properties of the fumed silica suspensions can also be tuned using both mechanical and magnetic stimuli or their combination. Our experimental approach involves a combination of shear rheology, optical imaging, and the use of an external magnetic field to induce and investigate changes in the mechanical response and microstructure of different sample suspensions.

Language

English

Subject

Fumed silica

Magnetic field effect

Manetorheological fluids

Shear induced changes

Κολλοειδή πηκτώματα

Μαγνητικά συστήματα

Issue date

2024-07-24

Collection