Traditional and Advanced Ceramics

Traditional and advanced ceramics are to be discussed here. A ceramic is a material that is neither metallic nor organic. It may be crystalline, glassy or both crystalline and glassy. Ceramics are typically hard and chemically non-reactive and can be formed or densified with heat. Ceramics are more than pottery and dishes: clay, bricks, tiles, glass, and cement are probably the best-known examples.

Ceramic Materials Applications

Ceramic materials are used in electronics because, depending on their composition, they may be semiconducting, superconducting, ferroelectric, or an insulator. Ceramics are also used to make objects as diverse as spark plugs, fiber optics, artificial joints, space shuttle tiles, cooktops, race car brakes, micro-positioners, chemical sensors, self-lubricating bearings, body armor, and skis.

Ceramic an Inorganic Non-metallic Solid

A ceramic is an inorganic non-metallic solid made up of either metal or non-metal compounds that have been shaped and then hardened by heating to high temperatures. In general, they are hard, corrosion-resistant and brittle.

The Term Ceramics

Traditional ceramics are clay-based, but high-performance or advanced ceramics are being developed from a far wider range of inorganic non-metal materials. Advanced ceramics have the properties of high strength, high hardness, high durability and high toughness. Ceramic comes from the Greek word meaning pottery. The clay-based domestic wares, art objects and building products are familiar to us all, but pottery is just one part of the ceramic world. Nowadays the term ceramic has a more expansive meaning and includes materials like glass, advanced ceramics and some cement systems as well.

Traditional Ceramics

Ceramics of traditional ages are clay based. The categories of pottery shown here are earthenware, stoneware and porcelain. The composition of the clays used, type of additives and firing temperatures determine the nature of the end product.

Major Types of Pottery

The major types of pottery are described as earthenware, stoneware and porcelain.

Earthenware 

Earthenware is used extensively for pottery tableware and decorative objects. It is one of the oldest materials used in pottery. The clay is fired at relatively low temperatures (1,000–1,150°C), producing a slightly porous, coarse product. To overcome its porosity, the fired object is covered with finely ground glass powder suspended in water and is then fired a second time. Faience, Delft and majolica are examples of earthenware.

Stoneware 

Stoneware clay is fired at a high temperature (about 1,200°C) until made glass-like (vitrified). Because stoneware is non-porous, glaze is applied only for decoration. It is a sturdy, chip-resistant and durable material suitable for use in the kitchen for cooking, baking, storing liquids and as serving dishes.

Porcelain 

Porcelain is a very hard, translucent white ceramic. The earliest forms of porcelain originated in China around 1600BC, and by 600AD, Chinese porcelain was a prized commodity with Arabian traders. Because porcelain was associated with China and often used to make plates, cups, vases and other works of fine art, it often goes by the name of fine china. To make porcelain, small amounts of glass, granite and feldspar minerals are ground up with fine white kaolin clay. Water is then added to the resulting fine white powder so that it can be kneaded and worked into shape. This is fired in a kiln to between 1,200–1,450°C. Decorative glazes are then applied followed by further firing.

Advanced Ceramics

Advanced ceramics are not generally clay-based. Instead, they are either based on oxides or non-oxides or combinations of the two:

Typical oxides used are alumina (Al₂O₃) and zirconia (ZrO₂).

Non-oxides are often carbides, borides, nitrides and silicides, for example, boron carbide (B₄C), silicon carbide (SiC) and molybdenum disilicide (MoSi₂).

Production Processes

Production processes firstly involve thoroughly blending the very fine constituent material powders. After shaping them into a green body, this is high-temperature fired (1,600–1,800°C). This step is often carried out in an oxygen-free atmosphere. The high temperature allows the tiny grains of the individual ceramic components to fuse together, forming a hard, tough, durable and corrosion-resistant product. This process is called sintering.

Applications of Advanced Ceramics

Advanced ceramic materials are now well established in many areas of everyday use, from fridge magnets to an increasing range or industries, including metals production and processing, aerospace, electronics, automotive and personnel protection. In modern medicine, advanced ceramics – often referred to as bioceramics – play an increasingly important role. Bioceramics such as alumina and zirconia are hard, chemically inert materials that can be polished to a high finish. They are used as dental implants and as bone substitutes in orthopaedic operations such as hip and knee replacement. Find out more on the uses for advanced ceramics.

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Sources

mse.umd.edu/about/what-is-mse/ceramics

www.sciencelearn.org.nz/resources/1769-what-are-ceramics