What is Ceramic?

Definition of Ceramic

A ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (a glass).

Explanation of Ceramics

The word ceramic comes from the Greek word κεραμικός (keramikos) meaning pottery, which is said to derive from the Indo-European word ker, meaning heat. Ceramic may be used as an adjective describing a material, product or process; or as a singular noun, or, more commonly, as a plural noun, ceramics.

The earliest ceramics were pottery objects made from clay, later it has been used for manufacturing domestic, industrial and building products and art objects as well. In the 20th century, new ceramic materials were developed for use in advanced ceramic engineering e.g. in semiconductors.

Types of Ceramic Products

Ceramic products are divided into four categories including:

Structural Ceramic including bricks, pipes, floor and roof tiles.

Refractories including kiln linings, gas fire radiants, steel and glass making crucibles.

Whitewares Ceramic including tableware, wall tiles, pottery products, and sanitary ware

Technical Ceramic is also known as Engineering, Advanced, Special, and in Japan, Fine Ceramics. Such items include tiles used in the Space Shuttle Program, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets, bio-medical implants, jet engine turbine blades, and missile nose cones. Frequently the raw materials do not include clays.

Technical ceramics are further classified into three distinct material categories:

1- Oxides: Alumina, Zirconia.
2- Non-oxides: Carbides, Borides, Nitrides, Silicides.
3- Composites: Particulate reinforced combinations of oxides and non-oxides.

Each one of these classes can develop unique material properties.

Types of Ceramic Material

A ceramic material is often understood as restricted to inorganic crystalline oxide material. It is solid and inert. Ceramic materials are brittle, hard and strong in compression, weak in shearing and tension. They withstand chemical erosion that occurs in other materials subjected to acidic or caustic environment. Ceramics generally can withstand very high temperatures such as temperatures that range from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F). Exceptions include inorganic materials that do not include oxygen such as silicon carbide or silicone nitride.

A glass is often not understood as a ceramic because of its amorphous (non-crystalline) character. However, glass making involves several steps of the ceramic process and its mechanical properties are similar to ceramic materials.

Traditional ceramic raw materials include clay minerals such as kaolinite, whereas more recent materials include aluminium oxide, more commonly known as alumina. The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance, and hence find use in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medicine, electrical and electronics industries.

Crystalline Ceramics

Crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with crystalline ceramics tend to fall into one of two categories including making the ceramic in the desired shape, by reaction in situ and by "forming" powders into the desired shape, and then sintering to form a solid body.

Ceramic forming technique include shaping by hand (including a rotation process called "throwing"), Slip casting, tape casting (for making thin ceramic capacitors), injection moulding, dry pressing, and other variations.

Non-Crystalline Ceramics

Non-crystalline ceramics, being glasses, tend to be formed from melts. The glass is shaped when either fully molten, by casting, or when in a state of toffee-like viscosity, by methods such as blowing to a mold. If later heat-treatments cause this glass to become partly crystalline, the resulting material is known as a glass-ceramic.