Manipulation of ceramic composite local composition at multiple length scale
File(s)
Author(s)
Jiang, Tianhui
Type
Thesis
Abstract
Emulsion templating has been developed for manipulating porous structures in a wide range of materials with controllable interconnectivity and pore size distribution. There are two main benefits to using emulsions as direct templates for dense composites. Firstly, the local composition can be controlled at the scale of a droplet, down to a few microns, with appropriate processing techniques and the application of surfactants. Secondly, the shaping of the emulsion into 3D objects can be achieved with multiple simple and scalable techniques, allowing for control of both bulk shape and inner structures.
This study explores the application of oil-in-water emulsion templating in the fabrication of inorganic/inorganic composites by dispersing inorganic particles in two phases. As a model system, ~101-μm decane-zirconia droplets are dispersed in aqueous-alumina continuous phase, with PVA as a surfactant. Through rheological studies of the emulsion and its components, it is found that the gelling effect of PVA is important in stabilising the system with two phases having mismatched densities. The slip-cast and sintered emulsion-templated composites exhibit porous structures with the inner wall coated with zirconia particles in the droplet phase. In situ monitoring reveals that the structure results from a multi-stage solvent removal process during slip casting. With the addition of magnetic templating and the replacement of materials in the droplet phase, anisotropic iron-alumina composites have been fabricated. In situ mechanical tests show that the composites are toughened by the iron fibres compared to pure alumina due to crack bridging and deflection.
This study explores the application of oil-in-water emulsion templating in the fabrication of inorganic/inorganic composites by dispersing inorganic particles in two phases. As a model system, ~101-μm decane-zirconia droplets are dispersed in aqueous-alumina continuous phase, with PVA as a surfactant. Through rheological studies of the emulsion and its components, it is found that the gelling effect of PVA is important in stabilising the system with two phases having mismatched densities. The slip-cast and sintered emulsion-templated composites exhibit porous structures with the inner wall coated with zirconia particles in the droplet phase. In situ monitoring reveals that the structure results from a multi-stage solvent removal process during slip casting. With the addition of magnetic templating and the replacement of materials in the droplet phase, anisotropic iron-alumina composites have been fabricated. In situ mechanical tests show that the composites are toughened by the iron fibres compared to pure alumina due to crack bridging and deflection.
Version
Open Access
Date Issued
2024-02-20
Date Awarded
01/06/2024
License URL
Advisor
Saiz, Eduardo
Bouville, Florian
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/P006566/1
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)