Types, Properties and Uses of Ceramics

What are Ceramics?

Ceramics are defined as hard, inorganic, nonmetallic, and heat-resistant materials (like clay, glass and even cement) which had been shaped, and fire-hardened at high temperatures in a kiln, and subsequently cooled.

Ceramics include substances like clay products, glass and cement which are used in making pots, dinnerware, porcelain, bricks, tiles and many other finished products.

Ceramics can be put into various types. These are explained below:

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• Traditional Ceramics

These are made primarily from natural clay minerals. They are crafted from naturally occurring raw materials like clay, quartz, sand, and feldspar; and are fired at high temperatures to create a variety of strong and durable products. Examples include our everyday products such as household tableware, pottery, bricks, and even tiles.

Note: Traditional ceramics are fired at temperatures between 900^oC and 1400^oC. The exact temperature depends entirely on the type of clay and the firing stage. This makes them porous since they are made of natural, earthen clays that are hardened by heat.

• Earthenware

These are porous ceramics made from clay which had been baked or fired at temperatures between 900^oC to 1,150^oC. The firing of earthenware at such a relatively low temperature make them easier to shape than porcelain or stoneware. Due to their porosity, they naturally absorbs liquids, and are typically coated with a ceramic glaze to make it watertight and beautiful. For this reason, they are often used as decoratives in vases, flower pots, and terracotta.

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• Stoneware

These are clay products made primarily from stoneware clay, quartz, and feldspar; and are fired at high temperatures between 1100^oC and 1300^oC. As a result, stonewares are dense, durable, vitreous (glass-like) and nonporous processed clay products often used for household diningwares, kitchenwares and decorative vases.

• Porcelain

These are white colored and translucent processed ceramic products that are hard, fine-grained, and non-porous. The raw materials for making porcelain (that is: kaolin clay) are heated in a kiln at very high temperatures of about 1200^oC to 1460^oC. This massive heat causes the materials to vitrify (that is; fuse together like glass), thus making them very strong, durable, highly resistant to stress, stains and chemicals.

Examples of products made of porcelain include traditional plates, tea cups, tumblers, bowls, soup tureens, and platters.

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• Advanced (Engineering) Ceramics

These are synthetic nonmetallic ceramic materials engineered for specific functions which could be electrical, thermal, or mechanical. In this regard, they have great mechanical strength, thermal stability, and electrical insulation.

Advanced engineering ceramics are generally classified into oxides and non-oxides. Below are oxide examples of advanced engineering ceramics:

• Aluminum Oxide (Al₂O₃) or Alumina: Al₂O₃ is considered the most common advanced engineered ceramic. It is characterized by great durability, hardness, and absolute electrical insulation. It is particularly used in the production of high-voltage insulators and various cutting tools. It can also be used as a warfare armor, and as biomedical implants.

• Zirconium Dioxide (ZrO₂) or Zirconia: ZrO₂ are advanced oxide engineered ceramics known for their durability, flexibility and resistance to thermal shock. They are applied in the manufacture of dental crowns in tooth, oxygen sensors and ceramic knives.

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Examples of non-oxides advanced engineered ceramics include the following:

• Silicon Carbide (SiC): These ceramics shows great durability, hardness, and thermal conductivity. Thay are applied in the production of rocket nozzles and mechanical seals.

• Silicon Nitride (Si₃N₄): They have high tensile strength and great thermal shock resistance. Their low density make less bulky when compared to other ceramics. They are applied in  the manufacture of high-speed engine parts, rotors, and high-precision bearings.

• Aluminum Nitride (AlN): They serve as good conductors of heat and bad conductors of electricity. They are applied in the manufacture of parts of heat and semiconductor components.

• Boron Nitride (BN): These ceramics are characterized with a layered crystal structure. As a result, they can withstand high temperatures without fracturing. They also have high chemical stability. Boron nitrides are used in the manufacture of crucibles where metals are melted. They can also serve as electrical insulators in vacuum systems.

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Properties of Ceramics

• They are very hard and tough, making them highly wear-resistant and ideal for cutting tools and abrasives.

• They are refractory. This means they can endure extremely high temperatures without melting, making them useful in the manufacture of cookingwares and heat shields. They therefore have a very high melting point.

• They are excellent heat and electrical insulators.

• They can be compressed without breaking or fracturing. In this regard, they are very durable.

• When compressed with a greater tensile strength (force), they will rather fracture, crack or shatter rather than bend. This makes them brittle under great tensile strength.

• They are highly resistant to corrosion. This is as a result of their inert molecules which makes them unreactive to the atmospheric gases, bases and acids respectively.

• They have low thermal expansion. This imply that they do not expand or contract significantly with temperature change.

Please read more on the characteristics of ceramics here.

Uses of Ceramics

• Ceramic products such as mugs, teacups, plates, pots and bowls are used as tableware and kitchenwares because they are heat-resistant and non-reactive.

• Products of ceramics like clay, bricks, cement and concrete blocks are used for building the foundational structures and pillars of engineering constructions.

• Abrasive tools and heavy-duty cutting instruments are manufactured from ceramic materials; for example, silicon carbide.

• Products of ceramics such as tiles and terracotta are used for floor, walls and roof finishing in homes.

• Ceramics products can be applied in medicines as artificial bone support, and as durable dental implants since they don't react adversely with the human tissue.

• Non-porous porcelain and stoneware are used as toilet bowls, washbasins and bathtubs.

• Ceramic products such as spark plugs and high-voltage electrical poles serve as excellent electrical insulators with great tensile strength and durability.

• Ceramics are applied in electronic panels and computer chips where they serve as substrates for resistors and capacitors.

• Advanced tensile ceramics are applied in the manufacture of body armor and bulletproof vests.

• Highly heat-resistant ceramics are required for shielding spaceships and space shuttles from extreme temperatures.

You can read more on the types of ceramics here.

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