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While most materials are classified by their properties, ceramics are classified by what they’re not. A ceramic material is any material that is inorganic and non-metallic. They are present in nearly every part of our daily lives and new types of ceramic are constantly being design by material engineers.
There are some that also define ceramics as a ‘refractory’ material, which, in layman’s terms, mean a material that is able to withstand extreme temperature, ph levels and wear resistant. However, this terminology becomes confusing when other forms of ceramic, such as graphite, does not exhibit the same properties as other, more traditional, ceramics. Graphite is sensitive to wear-and-tear and is known to be a good conductor of electricity. Another example of this is diamond, which is also considered a ceramic but has completely different properties to graphite.
The tradition of creating ceramics is something that started thousands of years ago with the invention of pottery, glass, and brick and is something which is continued today. New ceramic materials are being created in order to meet new challenges such as a catalytic converter for a car or superconductors for computers. Because the uses and properties of such ceramics are so varied, material engineers divide ceramics into two categories, traditional ceramics, and engineering ceramics.
Traditional ceramics, such as bricks, porcelain, tiles, and concrete are recognizable and generic materials that are present in everyday objects. Advanced engineering ceramics have very specific applications due to their specialized material properties. Examples of advanced engineering ceramics include silicon nitrides and tungsten carbides which have been designed to be extremely hard and are used for cutting tools. Another example is lithium-silicon oxide. This material used to create nose cones on space rockets due to its exceptional heat resistance.
The atomic scale structure dictates the properties of all-ceramic materials. The manipulation of the types of bonding between atoms and the types of atoms means that ceramics can be created with a wide variety of properties. Most ceramics available are compound, meaning that they are created from more than one element and held together by a chemical bond, like alumina, which is made from aluminum and oxygen.
The majority of ceramics have covalent or ionic chemical bonding which are much stronger than those found in metals. Because of this, ceramics are known to fracture easily in comparison to metals which are more ductile. As mentioned previously, the properties of ceramics vary depending on design and application however, many ceramics are known to have the following properties;
- They are hard, they are not indented easily
- They are wear-resistant and not easily scratched
- They are brittle, meaning they have a low resistance to impact
- They are refractory. This is a very useful property as it means that these materials are resistant to heat, pressure and chemical attack
- They make good thermal insulators
- They do not conduct electricity
- They are nonmagnetic
- They are resistant to oxidation (ie resistant to sealing)
- They are chemically stable
Ceramics have a multitude of applications because of there properties, from buildings, teapots, space rockets and supercomputers. Ceramics are an important part of the modern world and are invaluable to our daily lives.
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