טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKigli Avital
SubjectCapillary Bridges Between Solids
DepartmentDepartment of Chemical Engineering
Supervisor Professor Simon Brandon
Full Thesis textFull thesis text - English Version


Abstract

There are many types of solid-liquid-gas three-phase systems at equilibrium, both in natural and in synthetic settings. In this thesis the focus is on generic systems of particles joined via liquid bridges. The spontaneously formed bridges are finite volumes of liquid trapped between particles, forming solid-liquid interfaces, and include menisci (liquid-gas interfaces) whose shapes, assuming nonvolatile liquids, are governed by inter-particle separation, wetting angle and liquid volume.

The bridges act as binders between the solid bodies, where in this study the size of bridges is restricted so they are large enough for adhesion to be dominated by capillary forces (surface tension as well as Laplace pressure), and small enough so that gravity does not impact shapes and forces (as determined by the Bond number).

Pioneering experimental and theoretical studies on capillary bridges classified their shapes formed between two solid and between solid and fluid phases, determined the capillary forces and investigated the effect of their configuration on stability for particular sets of conditions such as particles size, inter-particles gap, wetting angle and the liquid volume. Numerical solutions of the Laplace equation of capillarity for different types of bridges have been discussed with relation to different geometries such as bridges between two spheres, a sphere and a plate, and two crossed cylinders, in most (but not all) cases with respect to non-volatile liquids, and mainly in terms of forces, torques (when relevant) and stability with respect to rupturing of the bridge. Some recent studies discuss thermodynamic stability of bridges in volatile systems exhibiting liquid-gas equilibrium and, in at least one case, involving three phases (a colloidal system) with solid particles and two partially mutually miscible liquids at equilibrium.

In this thesis the conditions for equilibrium states in different types of liquid (or fluid) bridge systems involving general solid particle geometries are presented These conditions are applied in a number of cases where the focus is on the appropriate energy or in some cases stability of a single bridge as compared to multiple bridges coexisting in the same physical system.

Therefore, this research overviews the main studies done so far and expands the knowledge for understanding the stability of colloidal structures by using capillary bridges. This research presents a new way of evaluating the liquid bridges by analyzing the point of critical separation distance between different sets of particles and other physical and geometrical parameters which affect the stability of the bridge.