You can meet materials in several ways: based on their properties, based on their applications and based on the materials themselves. The book ‘Meet materials’ is made up of various modules, each with its own line of approach.
Overview of the modules
Description of the modules
Materials as such
Materials are the building blocks of everything we see around us. After all, where would smartphones, cars, buildings or solar cells be without the right materials? The microstructure of materials – that is, the structure on a small scale – largely determines the final properties of a material and thus of a product. By turning the right knobs on a small scale, we can improve the product’s properties or find a cheaper manufacturing route. The arrangement of atoms in a material plays an important role in the final properties.
Light and materials
When materials come into contact with light, they can either reflect the light (mirror), let it through (window glass) or absorb it, for example by converting it into heat. The interaction between the light and (free) electrons in the material is important in this respect: in order to be transparent, a material must not conduct electricity. Materials themselves can also emit light, for example by driving a strong electric current through them as in the case of the incandescent light bulb. Energy saving lamps convert ‘invisible’ radiation into visible light, and in LED lamps semiconductors emit light when an electric voltage is applied over them.
Temperature and materials
Why do some materials conduct heat very well, and why are others poor thermal conductors? And what it the reason that the inside of a croquette is still glowing hot, while the crispy outside feels a lot cooler? Materials handle high temperatures in very different ways. For example, you can still use ceramic materials at temperatures where metals and polymers have long since given up. And by giving steel the right heat treatment, you can transform it from a soft and easily workable material into an extremely hard and strong one.
Electricity and materials
Different things can happen when a material is subjected to ‘electricity’. For example, in an electrical conductor such as copper and other metals, the mobile charged particles start to flow. An electrical insulator lacks these mobile charged particles – for example, because they are too strongly bound to their place to be free. And that’s a good thing if you want to use such a material to insulate against electric shock, as in the case of plastic sheaths of electric wires. Yet there are insulators that do ‘something’ when you apply an electric field to them – for example piezoelectric materials, which can change shape in response.
Materials under mechanical load
Products – and also the materials of which they are composed – have to endure a lot during their lifetime. If not during their ‘birth’, the production process, then at least during use. Pushing, pulling, bending, bumping, falling, vibrating … materials are subjected to many mechanical loads. And different materials respond to these loads in different ways. Sometimes the material yields, sometimes nothing (apparently) happens, and sometimes the material breaks. Whereas a stone cup usually breaks when you drop it on the floor, a rubber bouncing ball bounces back.
Materials from the beginning to the end (and beyond)
If you want to make a product ‘from scratch’ out of raw materials, you have to go through a number of manufacturing steps. First you have to extract the raw materials and convert them into a workable material, which you then shape and refine in one or more steps – for example with a protective coating – before you have the final object. And for products that consist of multiple materials, there are also merging or joining steps. Sooner or later, materials become impractical, due to wear, deterioration (such as corrosion) or fracture. You can extend the life by making the material stronger or self-healing, or give a used material a second life by recycling it.
Materials in IT
Even in wireless communication, materials are indispensable. The trend towards increased mobility calls for light, compact devices such as notebooks, tablets and smartphones – whose batteries you don’t throw away but which recharge every night. Magnetic materials are the backbone of hard disk drives in datacenters, and semiconductors are in the heart of every microprocessor. The transport of light through glass fibres is used as a very fast means of communication. Data can be sent digitally into the fibre by switching an LED or a laser on and off at lightning speed to generate bits (‘ones’ and ‘zeros’) – the Morse code of the 21st century.
Energy and materials
The skyline in the Netherlands is no longer what it used to be. In the early days there were windmills and now, apart from high-rise buildings … ‘windmills’ again! But with a different purpose: wind turbines to produce electricity. Solar cells convert energy from sunlight into useful electrical energy – the reverse of an LED lamp. In fuel cells, a controlled chemical reaction occurs that produces electricity – in a way, a modern version of the car’s combustion engine. Rechargeable lithium ion batteries are the work horses of today that power notebooks, tablets and smartphones, and that also literally and figuratively boost electric cars and bicycles.
Materials and transport
To reduce fuel consumption, you want a vehicle to be as light as possible. Of course, this can be achieved by clever design – for example, by using hollow instead of solid tubes. But light metals like magnesium and aluminium have also become more common – in land vehicles as well as in aircraft. Porous asphalt on motorways ensures that rainwater runs off quickly – a relief for the cars that race over it. And what is the difference between a summer tyre and a winter tyre, actually?
Materials in and around the house
Clay is literally the main ‘raw’ material for traditional ceramics. It cannot be a coincidence that houses and other buildings are largely based on ceramic materials such as concrete, bricks and roof tiles. In and around the house, you have to deal with countless materials. Polystyrene foam, for example, has excellent thermally insulating properties. The clothes that you wear can be either natural or synthetic. A few questions out of the kitchen: is aluminium or steel the most ideal material for a pan? And why are glasses, metal cutlery and ceramic plates already dry when you open the dishwasher after running it, while plastic cups are often still wet? These practical ‘questions of life’ are answered in this book.
Besides their excellent electrical conductivity – just think of copper as a live wire – metals are also ideal materials from a mechanical point of view: stiff, strong and tough. They owe their popularity to the relative ease with which they can be shaped into products. Metals can also be made (more) strong through various processes. In general, metal needs to be well protected against corrosion.
Ceramics and glass
Ceramics can withstand compressive loads, and the materials are also wear-resistant, hard and stiff. Whereas traditional ceramics are based on clay, pure high-quality powders form the basis for advanced ceramics. The Achilles’ heel of ceramics – and of its transparent brother glass – is its brittle fracture behaviour. Just think of the irresistible attraction that glass exerts on soccer-playing youngsters …
Polymers, also known as plastics, are particularly popular because you can usually shape products in one step, without reworking them. They are light and relatively flexible – and sometimes elastic like rubbers. Historically, polymers do not conduct electricity, so they are well suited, for example, as sheaths for live wires. In recent years, however, conductive polymers have been on the rise, especially in consumer electronics.
An elegant way to obtain even better materials is to combine two existing materials, with the idea that the properties of the original materials strengthen each other. Well-known composites are reinforced concrete and glass fibre-reinforced plastics. Inspiration for composites comes from nature, with wood and bone as examples.