Ceramic
A ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. If later heat-treatments cause this glass to become partly crystalline, the resulting material is known as a glass-ceramic. .Both are valued for their abrasion resistance, and hence find use in applications such as the wear plates of crushing equipment in mining operations. 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.
Details of these processes are described in the two books listed below.) A few methods use a hybrid between the two approaches. Non-crystalline ceramics, being glasses, tend to be formed from melts. Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the non-crystalline glasses. The earliest ceramics were pottery objects made from clay, either by itself or mixed with other materials.
Ceramic forming techniques include shaping by hand (sometimes including a rotation process called throwing ), slip casting, tape casting (used for making very thin ceramic capacitors, etc.), injection moulding, dry pressing, and other variations. 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 silicon nitride. A glass is often not understood as a ceramic because of its amorphous (non-crystalline) character.
Ceramic materials are brittle, hard, strong in compression, weak in shearing and tension. Ceramics now include domestic, industrial and building products and art objects.
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. In the 20th century, new ceramic materials were developed for use in advanced ceramic engineering; for example, in semiconductors. 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. For convenience, ceramic products are usually divided into four sectors; these are shown below with some examples: Technical ceramics can also be classified into three distinct material categories: Each one of these classes can develop unique material properties because ceramics tend to be crystalline. A ceramic material is often understood as restricted to inorganic crystalline oxide material.
They withstand chemical erosion that occurs in other materials subjected to acidic or caustic environment. (See also Ceramic forming techniques.
The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Advanced ceramics are also used in the medicine, electrical and electronics industries. Crystalline ceramic materials are not amenable to a great range of processing.
Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). Methods for dealing with them tend to fall into one of two categories - either make the ceramic in the desired shape, by reaction in situ, or by forming powders into the desired shape, and then sintering to form a solid body.
It is solid and inert.
