Basically Engineering Materials Can be classified into
two categories-
2. Non-Metals
Metals are polycrystalline bodies which are having number of differentially
oriented fine crystals. Normally major metals are in solid states at normal
temperature. However, some metals such as mercury are also in liquid state at
normal temperature. All metals are having high thermal and electrical
conductivity. All metals are having positive temperature coefficient
of resistance. Means resistance of metals increase with increase of
temperature.
Examples of metals – Silver, Copper, Gold, Aluminum,
Iron, Zinc, Lead, Tin etc.
Metals can be further divided into two groups-
2. Non-Ferrous Metals- All non-ferrous metals are having very low permeability. Example: Silver, Copper, Gold, Aluminum etc.
Non-Metal materials are non-crystalline in nature. These exists
in amorphic or mesomorphic forms.
These are in both solid & gases forms at normal temperature.
Normally all non-metals are bad conductor of heat and electricity.
Examples: Plastics, Rubber, Leathers, Asbestos etc.
As these non-metals are having very high resistivity which makes them suitable for insulation
purpose in electrical machines.
|
|
Property |
Metals |
Non-Metals |
|
1. |
Structure |
All metals are having crystalline
structure |
All Non-metals are havingamorphic & mesomorphic structure |
|
2. |
State |
Generally metals are slid normal temperature |
State varies material to material. Some are
gas state and some are in solid state at normal temperature. |
|
3. |
Valance electrons and conductivity |
Valance electrons are free to move with in metals
which makes them good conductor of heat & electricity |
Valence electrons are tightly bound with
nucleus which are not free to move. This makes them bad conductor of heat
& electricity |
|
4. |
Density |
High density |
Low density |
|
5. |
Strength |
High strength |
Low strength |
|
6. |
Hardness |
Generally hard |
Hardness is generally varies |
|
7. |
Malleability |
Malleable |
Non malleable |
|
8. |
Ductility |
Ductile |
Non ductile |
|
9. |
Brittleness |
Generally non brittle in nature |
Brittleness varies material to material |
|
10. |
Lustre |
Metals possess metallic lustre |
Generally do not possess metallic lustre
(Except graphite & iodine) |
Engineering materials can also be classified as below-
2. Ceramic Materials
3. Organic Materials
Metals are polycrystalline bodies which are have number of differentially
oriented fine crystals. Normally major metals are in solid states at normal
temperature. However, some metals such as mercury are also in liquid state at
normal temperature.
Pure metals are having very low mechanical strength, which sometimes does not
match with the mechanical strength required for certain applications. To
overcome this draw back alloys are used.
Alloys are the composition of two or more metals or metal and
non-metals together. Alloys are having good mechanical strength, low temperature
coefficient of resistance. Example: Steels, Brass, Bronze, Gunmetal, Invar.
Super Alloys etc.
Ceramic materials are non-metallic solids. These are made of
inorganic compounds such as Oxides, Nitrides, Silicides and
Carbides. Ceramic materials possess exceptional Structural, Electrical,
Magnetic, Chemical & Thermal properties. These ceramic materials are now
extensively used in different engineering fields.
Examples: Silica, glass, cement, concrete, garnet, Mgo, Cds, Zno, SiC etc.
All organic material are having carbon as a common element. In
organic materials carbon is chemically combined with oxygen, hydrogen and other
non-metallic substances. Generally organic materials are having complex
chemical bonding.
Example: Plastics, PVC, Synthetic Rubbers etc.