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Title: Morphological characterisation of porous materials for fuel cell technology
Author: Hihinashvili, Rebecca
ISNI:       0000 0004 2741 7498
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Porous materials play an important role in many applications, e.g. fuel cells, bone transplants and CO2 storage. The current thesis is motivated by the challenges faced in fuel cell technology with regard to the design and manufacture of porous electrodes. The macroscopic, observable properties of porous materials are determined by their microstructure. However, the challenge still remains in finding and formulating relations between the microstructure and the macroscopic properties. This work tests and develops further a recent method that aims at deriving such relations. The method consists of first quantifying the microstructure in terms of volume elements called quadrons. This description is then used in an entropy-based statistical mechanical formalism that makes it possible to derive macroscopic properties. We apply the quadron description to numerically generated structures: planar granular packs and 3D tetrahedral cellular structures. We find that the quadron statistics are sensitive to the microstructure. Especially, they capture information about the pores, a microstructural feature that grain-based volumes such as Voronoi cells do not capture. We evaluate the compactivity – an analog to temperature – of the planar packs using different methods. All the methods give the right relation between the compactivities of the packs. In addition, the volume distributions of the quadrons decay exponentially. These results lend support to the statistical mechanical formalism. We compare the quadron statistics of different 3D cellular structures including examples of relevant microstructural features such as the throats – the openings between two pores. Applying the reciprocity defined within the quadron description, we link between grain shapes, the number of grain contacts and the length of the TPB, which is a key property of fuel cells electrodes. This reproduces an established phenomenon in granular materials, however, this result is obtained here using cellular structures and the quadron description only.
Supervisor: Blumenfeld, Raphael Sponsor: Imperial College London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral