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Chapter 25
Section 2
Ceramics
• Ceramics are materials that are made from dried
clay or clay like mixtures.
• Ceramics can be made from easy to obtain
materials like clay, sand and feldspar. It can also
be made of metallic elements, carbon, nitrogen,
or sulfur.
• After the raw materials are processed the they
are molded into a desired shape and then heated
to temperatures between 1000°C and 1700°C.
• The heating process is called firing.
• When a ceramic is heated it shrinks the spaces
between the particles of the ceramic.
• The entire object shrinks as the spaces
become smaller. This makes the ceramic
strong in some aspects like heat resistance.
• However ceramics are still fragile and can
break if dropped or if the temperature
changes too quickly.
Traditional Ceramics
• Ceramics are known for their chemical
resistance to oxygen, water, acids, bases, salts,
and strong solvents.
• Because of this they are more commonly used
when interacting with any of those
substances. An example would be tableware.
• Ceramics are also used as insulators as it does
not conduct heat or electricity.
Modern Ceramics
• Today ceramics can be manufactured with
properties that non traditional.
• Chromium dioxide is a special ceramic that can be
conductive.
• Some copper based ceramics even have
superconductive properties.
• One use of these special ceramics would be in
airplane windshields. Because they conduct heat
they can transfer heat from inside the cabin to
prevent it from freezing.
• Modern ceramics also have medical uses.
• Many joint replacements such as a hip
replacement are made from ceramics since
they are durable and resistant to body fluids.
• Dentists also use ceramics to repair teeth. If
you have a filling or cap that is white then it
would be a ceramic not the silver mercury
alloy.
Semiconductors
• A semiconductor is a poorer at conducting
than metals, but better than nonmetals.
• These are known as metalloids on the periodic
table.
• Their electrical conductivity can be controlled
by adding other elements to the metalloids.
• An example of controlling conductivity would
be silicon. Pure silicon is stable and allows no
room for electrons to move. However if you
add impurities such as arsenic or gallium then
the electron balance is destabilized. Since
both elements have less electrons than silicon
there is a gap where an electron can now
move to, thus allowing for an electrical flow.
• The process of adding the impurities to a
semiconductor is called doping.
• Depending on the elements added the overall
number of electrons will increase or decrease.
• N-type is when the number of electrons is
increased.
• P-type is when the number of electrons is
decreased.
• By placing n-types and p-types together then you
can make things like transistors and diodes.
• While this was being done the integrated circuit
was also developed.
• An integrated circuit is a tiny chip that contains
millions of semiconducting devices like
transistors. They are also know as microchips.
• These chips were a beak through for technology
and enable a lot of what we enjoy today to work.
Section Check
• What are some uses of ceramics?
• Describe the electrical conductivity of
ceramics.
• What is a semiconductor?
• What is the difference from a n-type and ptype semiconductor?