What are Ceramics?
Definition: Ceramics are the nonmetallic and inorganic materials that are generally electrical and thermal insulators, brittle and are composed of more than one element (e.g two elements in Al2O3).
Ceramic materials have specific properties due to which they are used in various applications including; electric insulation, corrosion resistance, high heat capacity & low heat conduction, artificial joints, etc.
Well, this was just a simple overview. But there are a lot more things about ceramic materials that you should know.
Let’s dive right into it!
What are Ceramics made of?
In simple words, ceramics are made up of a mixture of clay, sand, flint, quartz, silicates and other earthen elements.
But in terms of material science and engineering, ceramics are made up of mixed, ionic and covalent bonding of elements.
The covalent bond between the elements involves the sharing of valence electrons with each other, while the ionic crystals involve cations like alkalis and alkaline earth metals, and anions like oxygen or halogens.
On the basis of crystal structure, the Ceramics are divided into two groups.
- Crystalline ceramics
- Amorphous ceramics
Crystalline ceramics: In crystalline ceramics, the atoms (or ions) are arranged in a regular repeating pattern and they have long range order.
Amorphous ceramics: In amorphous ceramics, the atoms (or ions) generally have only short range order.
Now further, the classification of ceramics based on composition is discussed below for your perfect understanding.
Classification of ceramics based on composition
On the basis of composition, there are 4 types of ceramics;
- Silicate ceramics
- Oxide ceramics
- Non oxide ceramics
- Glass ceramics
Let’s see what these ceramics are made of!
#1) Silicate ceramics
Silicate ceramics contain silicon and oxygen in it.
The silicon atom is surrounded by four large oxygen atoms (see above image).
Silicon and oxygen elements are found in abundance in the earth’s crust.
Also the combination of silicon and oxygen is found in soils, rocks, clays, sand, etc.
They are combined with weak ionic bonds having Si4+ and O2- ions.
There are two types of silicate ceramics.
- Alumino silicates
- Magnesium silicates
Alumino silicates are included in clay based ceramics like porcelain, stoneware, etc. While magnesium silicates are included in talc based ceramics like steatite, cordierite, forsterite, etc.
#2) Oxide ceramics (Aluminum oxide, Al2O3)
Oxide ceramics are made of a combination of metallic or metalloids elements with oxygen.
These oxides ceramics also have a tendency to combine with nitrogen to form oxy-nitride ceramics and with carbon to form oxy-carbide ceramics.
Oxide ceramics have various properties like;
- Higher melting temperatures
- Low wear resistant
- Various electrical properties
#3) Non oxide ceramics
Various non oxide ceramics includes;
- Silicides, etc.
Non oxide ceramics are used in various applications like;
- Cutting tool tips
- Rocket nozzles
- Hard abrasives
- Electrodes for heating or melting metals, etc.
During the manufacturing of non-oxide ceramics, they must undergo high temperature processing in the inert atmosphere to prevent its oxidation.
Also liquid phase sintering and reaction bonding techniques are required for densification.
Out of many other non oxide ceramics, Silicon carbide (SiC) is the most important and widely used non-oxide ceramic material.
#4) Glass ceramics
Glass ceramics are made up of polycrystalline materials and are manufactured by controlled crystallization of base glass.
The glass ceramics possess the properties of both glass as well as ceramics.