Simultaneous structural and dielectric measurement of ammonia storage materials

Hartley, Jon 2015. Simultaneous structural and dielectric measurement of ammonia storage materials. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The principal aims of this thesis are to design, build and experiment with simultaneous measurement systems, designed to measure ammonia adsorption in a wide range of sample materials. These simultaneous measurement systems will integrate dielectric spectroscopy methods with structural analysis techniques in order to obtain a more complete understanding of the dynamic adsorption processes that occur. Some of the new and most promising materials for ammonia storage applications are tested in this thesis in order to understand the possible strengths and weaknesses that these materials have in becoming used in real world applications. Dielectric spectroscopy in this thesis is achieved by using microwave resonant structures. These devices measure permittivity, dielectric losses and electrical conduction by way of the cavity perturbation technique. Structural analysis is conducted by way of neutron and X-ray diffraction, both of these measurement techniques give insight into the crystal structure of materials. With these two measurement techniques, changes in bulk material properties (measured from the dielectric spectroscopy) can be compared and contrasted with changes in the crystal structure (measured from the diffraction techniques). The materials tested within the simultaneous measurement systems were alkali earth and transition metal halides. On introducing gaseous ammonia to these materials, the dielectric properties and molecular structure changed. Using the combined information from multiple measurement techniques, a wide range of physical phenomena was able to be observed and analysed. This included assessment of the total amount of ammonia adsorbed, the amount of chemisorbed ammonia to physisorbed ammonia and if the ammoniated material was stable after the ammoniation process. Phase transformations involving coordination geometry were observed, as well as suppression of hole conduction processes due to ammoniation.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Engineering
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Uncontrolled Keywords:	Microwave cavity resonator; Ammonia storage; Neutron diffraction; Metal halides; Dielectric measurement; Perturbation technique.
Date of First Compliant Deposit:	20 April 2016
Last Modified:	21 Oct 2016 05:36
URI:	https://orca.cardiff.ac.uk/id/eprint/89378

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