Contributions to Materials Science and Engineering

Abstract

The regulations for the award of the degree of Doctor of Science of the University of Ulster require that this statement be prepared "showing the relationship between the various studies and indicating how far and in what respect the contributions appear to him to advance the study of his subject". The work compiled in this thesis consists of as a series of contributions to Materials Science and Engineering (MS&E). In order to place the work in context and to appreciate the fashion in which the various contributions relate to each other, it is useful to review briefly the foundations and emergence of materials science as a discipline. In a recent monograph, Robert Cahn (Robert Cahn, "The Coming of Materials Science", Pergammon, pp. 360, 2001) has traced the emergence of materials science from its origins in solid-state physics, condensed matter physics, physical chemistry, physical metallurgy and polymer science. These core subjects provide the firm intellectual foundation on which the discipline is established. As its origins suggest, materials science is an inherently multidisciplinary and interdisciplinary activity of considerable scope and reach.

The core academic activity at the center of the pentahedron is the search for new knowledge and a better fundamental understanding of how the macroscopic properties of matter are related to microscopic structure. At the basic science level there is, in common with chemistry and physics, the drive to understand the nature of matter overa range of distance and energy scales. However, a key differentiating, perhaps even defining, element of materials science is that the subject concentrates on processing and producing new forms of matter that are enabling or have enhanced performance in engineering applications. This applied dimension anchors the materials science and engineering approach firmly in the industrial and applied science arena. In this sense it could be argued that MS&E is characterized not so much by what is done, for in operational detail that is largely the chemistry, physics, polymer science, etc., the classical core disciplines, but rather how the work is driven and how it is executed. It is driven, i.e. funded, by the need to produce a material-based solution to an operational need. Interdisciplinary teams, often through the collaboration of university, government and industrial laboratories, execute it. Materials science and engineering provides what might be termed a "systems" approach that integrates teams in particular specialties towards an engineering goal. Good (Mary L. Good, "Materials through Chemistry" American Chemical Society, pp. 217, 1998) has pointed out the degree to which the materials research enterprises now embraces a large cross-section of research activity ranging from synthetic organic chemistry through statistical mechanics and thermodynamics to chemical engineering and process control.

For example, in aerospace applications there is a ubiquitous requirement to produce lighter materials from which to fabricate airframes and spacecraft. Engine development is already far advanced; arguably mature, and expected gains in the thrust/weight ratio from increasing the thrust through better aerodynamic designs are only of the order of 10%. However, new polymers with fiber reinforcements have the potential to halve the weight of powered craft, hence the high importance placed on materials development in the aerospace field.

Another example from the author's laboratory is the development and processing of new lightweight polymeric materials for application in large (>100 m diameter) space borne mirrors, a prototype of which is shown in Figure 3. Such mirrors will allow us to see to almost the start of time from observatories in outer space; like the Hubble observatory, only very much larger. Glass mirrors of this size are much too heavy to launch into orbit, but one might think of a large inflatable polymeric mirror as shown in Figure 3 (the men in the figure are included to give a sense of scale) that is folded during launch and deployed on station when needed. If the polymer is coated with reflective materials and has just the right mechanical response to form the required parabolic profile when deployed then these concepts might be used to produce exceedingly large space-based optics or even very cheap large aperture telescopes for the terrestrial amateur astronomer. Of course, similar structures could be used as solar energy collectors and concentrators at the earth's surface.

Telescopes based on these concepts will provide an unprecedented look back in time but they will require the development of fundamentally new sorts of adaptive soft matter for active control of the reflective surface. These advanced applications require novel structures of matter that have performance characteristics far in excess of current capabilities. Similar examples could be selected from a number of fields. In the broadest sense MS&E represents the work of human minds expressed by human hands to add value to create wealth from the natural resources of the earth. The subject is concerned with how to turn the very "dirt" of the earth, the metal ores, the crude oil, into the automobiles, aircraft, aircraft engines, computers, materials, medicines and all the other accoutrements expected of our advanced civilization. This process to be successful requires the accumulated interdisciplinary knowledge of generations of scientists and engineers and represents the real or bedrock "knowledge environment" on which our economy is based and against which progress can and should be measured.

In order to produce these materials in the required quantities and qualities and cost it is necessary to:

a) Develop materials characterization techniques that probe the relevant structural properties of matter over appropriate energy and momentum domains;

b) Explore theoretical and computer modeling approaches that can help rationalize observed behavior and response and, more importantly, predict materials response in situations where direct measurement would be very difficult or even impossible;

c) Integrate the experimental and theoretical knowledge gathered in respect of (a) and (b) above, providing a seamless transfer of this knowledge into the engineering and manufacturing environment using advanced techniques such as computational methods coupled with artificial intelligence.

The papers presented in this thesis have been selected to illustrate the author's contribution to the above areas.

Date of Award	Mar 2004
Original language	English