Ceramics

• Ceramics are made from soft substances, which when heated become hard and brittle.
• Ceramics have many uses which can be linked to their properties.
• Some uses are clearly visible, such as coffee mugs, but other uses are less visible, such as in car engines.

Ceramics are materials which are hard and durable. They are made by baking a starting material in a very hot oven called a kiln. The temperature of kilns is adjustable for firing different clays and can reach temperatures of over 1300 °C.

The starting materials are soft and malleable, meaning they can be shaped. Clay is an example of a starting material.

These soft materials are shaped and then heated to make harder materials which we call ceramics.

These new hard ceramic materials have a fixed shape and cannot be bent.

There are three stages in the firing process.

1. Water that is in the clay evaporates as the material is heated up.

2. Chemical reactions occur changing the composition of the material.

3. Some of the substances in the clay melt and when the ceramic is cooled these harden.

Did you know?

Human beings have been making ceramics for over 20,000 years. A ceramic artefact of a statuette of a woman was dated as early as 28,000 BC.

Ceramics have a wide range of uses, linked to their properties.Common properties of ceramics include:

• hardness
• strong under compression
• brittle, meaning they can shatter when struck
• heat resistant

Ceramic materials are strong, so they can be used for structural products. For example, bricks are ceramic materials made by baking moulded clay.

Advantages of bricks include:

• they are hard so don’t scratch easily
• they are strong under compression, meaning houses aren’t crushed under their own weight

However, a disadvantage is:

• bricks are brittle, meaning they can break if handled carelessly during construction

Ceramics can be made into almost any shape, and glazed to give them a non-porous surface. This makes them useful for purposes where hygiene is important, because liquids containing microbes cannot soak into the ceramic and spread diseases.

For example, everything from cooking dishes to toilets is made from ceramics.

Advantages of using ceramics in the kitchen and bathroom include:

• the starting clay materials are malleable so can be made into different shapes
• ceramics are heat-resistant so won’t break in the oven

However, a disadvantage is:

• ceramics are brittle, meaning ceramics such as plates tend to break when dropped

Ceramics can also be painted with colourful glazes to make artistic and decorative items such as teacups and ornaments.

Ceramics are useful engineering materials as they are light and can be heated.

For example, a honeycomb shaped ceramic structure is used to support the metals which speed up the chemical reactions in catalytic converters, which are found in car exhaust systems.

Advantages of ceramics in engineering include:

• they have a low density which means they are light compared to their size
• ceramics are heat resistant so can be heated to high temperatures without breaking

Did you know?

The turbine blades of jet engines are coated in a specially engineered ceramic.

This is because ceramics are thermal insulators, meaning they stop the turbines from overheating when they spin thousands of times per minute.

Terracotta is an example of a ceramic material which is used for decorative purposes. It is heated to lower temperatures and left unglazed so the colour of the clay is visible. It has often been used in sculptures.

The Terracotta Army is a collection of terracotta sculptures made to protect the first Emperor of China in the afterlife.