Ceramics

 

What are ceramics?

Ceramics are hard and strong materials. They are made by heating a soft material in a very hot oven called a kiln. The kiln can change its temperature for different kinds of clay and can go up to more than 1300 °C.

The soft materials can be shaped before they are heated. Clay is one example of a soft material.

When the soft materials are heated, they become harder materials that we call ceramics.

Clay is shaped on a potter’s wheel.

 

The firing process has three stages:

 

• The clay loses water as it gets hotter.
• The material changes its composition because of chemical reactions.
• Some of the substances in the clay melt and become hard when the ceramic cools down.

 

Clay is heated to very high temperatures in a kiln.

 

Properties of ceramics

Common properties of ceramics include:

 

• Hardness.
• Strength under compression.
• Brittleness (ceramics can shatter when struck).
• Resistance to heat.

 

Uses of ceramics:

Ceramics have a wide range of uses including:

 

• Structural: Ceramics are strong materials that can be used for building products. For example, bricks are made by heating shaped clay in a kiln.
• Household items: Ceramics can have any shape and a smooth (porous) surface that does not let liquids in. This makes them hygienic and prevents germs from spreading. For example, ceramics are used for making dishes, toilets, and tiles.
• Technical: Ceramics are light and heat-resistant materials that are useful for engineering. For example, a ceramic structure with many holes supports the metals that make the chemical reactions faster in catalytic converters, which are in car exhaust systems.
• Decorative: Terracotta is a type of ceramic that is used for decoration. It is heated at lower temperatures and not glazed, so the colour of the clay shows. It is often used for making sculptures.

 

The Terracotta Army Source: kevinmcgill from Den Bosch, Netherlands - KAM_5111

 

🏺 Knowledge Check: Ceramics

Test your knowledge on the properties and science of ceramic materials based on the guide.

1. Which of the following is a key physical property of most ceramics?

• They are flexible and easy to bend.
• They are hard and brittle.
• They are excellent conductors of electricity.

2. What happens to clay when it is heated to a high temperature in a kiln?

• It melts into a liquid that stays soft forever.
• Chemical reactions occur that make the clay hard and strong.
• It turns into a metal lattice structure.

3. Ceramics are described as insulators. This means they are very poor at:

• Resisting chemicals.
• Supporting weight.
• Conducting heat and electricity.

4. Why do ceramics have high melting points?

• They contain a lot of water.
• They have strong chemical bonds in a giant structure.
• They are made of soft minerals.

5. Glass is a type of ceramic. What is the main raw material used to make most glass?

• Pure clay
• Sand (silica)
• Limestone

Click to Reveal Answers

1. Hard and brittle (Ceramics shatter rather than bend when stressed).
2. Chemical reactions occur (The heat permanently changes the clay's structure).
3. Conducting heat and electricity (They lack free electrons to carry energy).
4. Strong chemical bonds (A lot of energy is needed to break the bonds in the lattice).
5. Sand (silica) (Sand is melted and cooled to produce glass).

 

Summary:

 

• Ceramics are made from soft materials that become hard and brittle when they are heated.
• Ceramics have many properties that make them useful for different purposes.
• Some of the uses of ceramics are easy to see, like cups for coffee, but some are hidden, like parts of car engines.