Ceramics

History of ceramics[?]

Ceramics as a domain of materials science

Ceramics is the term used for the study of ceramic materials, both in the traditional sense of pottery, and in a modern sense of oxide- or nitride-based materials.

Examples of Ceramic Materials

• Silicon nitride (Si₃N₄), which is used as an abrasive powder.
• Boron carbide (B₄C), which is used in some helicopter and tank armor
• Silicon Carbide (SiC), which is used as a succeptor in microwave furnaces and as a refractory material
• Aluminum diboride (AlB₂), which may become a leading reinforcement material in metal matrix composites.
• Zinc oxide (ZnO), which is used as a material in a diode for its electrical properties.
• Ferrite (Fe₃O₄), which is magnetic and is used in the core of electrical transformers.
• Steatite is used as an electrical insulator.
• Bricks (mostly aluminum silicates ), used for construction.
• Uranium Oxide (UO₂), used as fuel in nuclear reactors.

Properties of Ceramics

Ceramic materials are usually hard and strong. However, imperfections in the ceramic make them brittle. Under some conditions, such as extremely low temperature, some ceramics exhibit superconductivity.

Some ceramic materials can withstand extremely high temperatures without losing their strength. These are called refractory materials. They generally have low thermal conductivities, and thus are used as thermal insulators. For example, the belly of the Space Shuttles are made of ceramic tiles which protect the spacecraft from the high temperatures caused during reentry.

A couple of decades ago, Toyota researched on producing a ceramic engine which can run at a temperature of over 6000°. Ceramic engines do not require a cooling system and hence a major weight reduction in fuel-efficient vehicles. Fuel efficiency of the engine is also higher at high temperature. In conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. Despite all the desirable properties, such engines are not in production because the manufacturing of ceramic parts is difficult. Imperfection in the ceramic leads to cracks. Such engines are possible in laboratory research, but manufacturing difficulties prevent them from becoming reliable products.

Processing of Ceramic Materials

Most ceramics must either be processed at high temperatures or by chemical methods. A common form of ceramic processing is Sintering a method of forming ceramic objects by mixing a ceramic powder with a binder and water to form a slurry, Spray Drying it, compressing the spray dried powder in a mold to form a "Green Body, and then heating it until atoms from the ceramic particles have diffused from one to another forming bridges between each particle and its neighbors.