What do we mean by ‘materials’? The simplest definition is ‘stuff’. There is natural stuff - wood, bone, straw, wool, cotton - and there is man-made stuff - steel, pottery, plastic, semiconductors, concrete, textiles, paper. People interested in materials are usually fascinated by two questions: ‘Why does each material behave the way it does?’ and ‘How can I exploit the properties of a material to make something better or cheaper?’ The people who concentrate on the ‘Why?’ are material scientists, and those who focus on the ‘How?’ are material engineers. Both types of specialists need to know what properties each material has and how they might be changed. Only very rarely can the answers be deduced using our bare hands and the naked eye, so the study of materials inevitably involves testing materials - - measuring their properties - and looking at their microstructure - using a microscope. The aim is then to deduce how the properties (strength, transparency, flexibility, conductivity, and so on) are related to the structure (crystal size, alignment of fibres, etc.). And the challenge is to use this knowledge to design and manufacture materials which have better properties for our purpose. Examples of this approach include the development of alloys which can be used at higher and higher temperatures in turbine engines and the development of plastics so resistant to breaking when bent that they can be used as hinges. We could not do these things fifty years ago, yet today they are commonplace.
In materials science, rather than haphazardly looking for and discovering materials and exploiting their properties, the aim is instead to understand existing materials so that new ones with desired properties can be designed. Materials science relates desired properties and performance of a material in a certain application to the structure of the atoms and phases in that material through characterisation. The major determinants are its constituent chemical elements and the way in which a material has been processed into its final form. These, taken together and related through the laws of thermodynamics, govern a material’s microstructure and, thus, its properties. Every day we come into contact with many thousands of manufactured objects that are essential to modern life: the vehicles that we travel in; the clothes that we wear; the machines in our homes and offices; the sport and leisure equipment we use; the computers and phones that we can’t live without; and the medical technology that keeps us alive. However, everything we see and use is made from materials derived ultimately from the Earth: metals; polymers; ceramics; semiconductors; and composites. To develop the new products and technologies that will make our lives safer, more convenient, more enjoyable and more sustainable we must understand how to make best use of the materials we already have and how to develop new materials that will meet the demands of the future. Materials science involves the study of the structure, properties and behaviour of all materials, the development of processes to manufacture useful products from them and research into recycling and environmentally friendly disposal. The basic building block of all matter is the atom and there are 94 different types that occur naturally on Earth. These are ‘the elements’ and include hydrogen, carbon, oxygen, aluminium, silicon, iron and copper. All materials are made up of these atomic building blocks but differ in their microstructure: the types of atom they contain; the pattern in which the atoms are arranged; and the way in which the atoms are joined together. The central concept in materials science is that the properties and behaviour of every material are dependant on microstructure and that microstructure can be controlled by the way in which the material is made and processed. Material scientists test the mechanical, physical, chemical and electrical properties of materials and explore how these depend on the microstructures they engineer and observe using high powered microscopes. This knowledge allows us to select the most appropriate material and manufacturing process for any given application, to predict how a component will perform in service and to investigate how and why materials fail. The technological advances that have transformed our world over the last 20 years have been founded on developments in materials science. Materials are evolving faster today than at any time in history, enabling engineers to improve the performance of existing products and to develop innovative technologies that will enhance every aspect of our lives. Materials science has become a key discipline in the competitive global economy and is recognised as one of the technical disciplines with the most exciting career opportunities.
– how the atoms fit together. For crystalline materials, then this involves the size and shape of the crystals (usually called grains).
– structure on a small scale so that a microscope is needed to see it.
– measured behaviour, such as strength, electrical conductivity, stiffness or colour
– changing the shape or properties of a piece of material, for instance by heating it, rolling it or stretching it.
– usually called plastics
– brittle non-conductors such as pottery