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A ceramic is a non-metallic material composed of inorganic molecules, normally prepared by heating and subsequent cooling. Many common ceramics are made up of oxides or nitride compounds and are crystalline with long range molecular order. Other ceramics are partially or fully amorphous, with no long range molecular order; these are typically classified as glassy materials.
This class of material includes plates and cups, bricks, earthenware pots, engineering ceramics, glasses [glasses are non-crystalline and not normally classed as ceramics], and refractory (furnace) materials. Ceramics are made by heating together materials such as silica, chalk and clays. Other chemicals may be included to act as flux and to change colour etc.
Engineering Ceramics Include
Cubic boron nitride
Engineering ceramics are ideally suited for high performance applications where a combination of properties such as wear resistance, hardness, stiffness and corrosion resistance are important. In addition to these properties, engineering ceramics have relatively high mechanical strength at high temperatures. They are good electrical insulators, They often have a close thermal expansion coefficient to metals (they can be bonded to metals - e.g. carbide tipped tools).
Ceramics have been regarded as hard but brittle, however modern ceramics have been developed which are viable alternatives to metals and their alloys in many applications - engineering ceramic parts and components are more durable and have longer life-spans under given operational conditions. Ceramic cutting tools, for instance, require less sharpening or replacement due to wear, and will last at least 60 to 100 times longer than steel blades.
Engineering ceramics are chemically resistant to most acids, alkalis and organic solvents and can withstand high temperatures. Metals weaken rapidly at temperatures above 816 degrees C while engineering ceramics retain a good degree of their mechanical properties at much higher temperatures.
Applications Mechanical components include wear plates and thermal barriers, bearings for high speed and high stiffness spindles, bushes, gears.
Process components include pump shafts, seats, bearing surfaces, gears and even complete pump bodies, valve guides and seats.
Ceramics are used for cutting tools including razor blades for film and tape cutting to 300mm diameter circular slitters for the paper industry.
Ceramic turbine blades are used in most turbochargers providing lighter units than the steel alternatives allowing improved performance at higher temperatures.