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Ceramics are inorganic non-metallic materials. Porcelain,
glass, bricks and refractory materials are examples of
traditional ceramics. Silicon nitride (Si3N4), silicon
carbide (SiC), alumina (Al2O3) and zirconia (ZrO2) are examples of
industrial ceramics.
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Typical properties
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Hard, high-temperature resistant materials, which do not
deform plastically. Ceramics can either be very strong or very
weak. Typical properties are good corrosion resistance and low
electrical conductivity and low thermal conductivity. There are
however ceramics with high thermal conductivity and/or high
electrical conductivity.
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Manufacturing
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Ceramics can be produced by compacting powders to a body. The
powder body is sintered at high temperatures. During sintering
the body shrinks, the grains bond together and a solid material
is produced.
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Machining
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After sintering, ceramics often have high wear-resistance and
high hardness making them difficult to machine. The powder body
therefore is formed as near the net shape as possible before
sintering.
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Forming
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Powder bodies with simple geometrical shapes are formed by
pressing. Complicated shapes can be formed by slip casting or
injection moulding. Foreign particles or other defects introduced
in the forming process influence the ceramics' strength after
sintering.
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High temperature properties
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For use in air temperatures above 1000°C, ceramics are the only
suitable materials for industrial purposes. High temperature
properties, however, are extremely dependent on the methods of
manufacturing.
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Some interesting combinations of properties
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- High wear-resistance combined with low density
- Wear-resistance in corrosive environments
- Corrosion resistance at high temperatures
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