Classification of Engineering Materials

Basic Classification of Engineering Materials Basically Engineering Materials Can be classified into two categories- Metals N...

Basic Classification of Engineering Materials

Basically Engineering Materials Can be classified into two categories-

  1. Metals
  2. Non-Metals

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:

Non-Metals

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.

Other classification of engineering materials:


Engineering materials can also be classified as below-

  1. Metals and Alloys
  2. Ceramic Materials
  3. Organic Materials

Metals and Alloys


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


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.

Organic Materials


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.

Materials used in the field of Electrical Engineering are called the Electrical Engineering materials. Based on properties and area of applications, Electrical Engineering materials can be classified as below-

  1. Conductors

  2. Semiconductors

  3. Insulators

  4. Magnetic material

Conductors


Conductors are the materials which have very high conductivity. The number of free electrons are very high in conductor at room temperature, which is basic reason of high conductivity of conductors. Examples: Silver, Copper, Gold, Aluminum etc.
The number of free electrons are very high in silver, which makes the silver a best conductors of electricity. The binding force on these free valance electrons by nucleus is very low. Due to which these electrons can be easy freed from the nucleus and can participate in flow of electricity.

Semiconductors


Semiconductors are have the conductivity between conductors and insulators. Semiconductors are the elements of group-III, group-IV and group-IV elements. Semiconducting materials are having covalent bond. At normal temperature the conductivity of semiconductors is very low. With increase of temperature the conductivity of semiconductors increase exponentially. Example: Germanium, Silicon, Gallium Arsenic etc.

Insulating Materials


The conductivity of insulating materials is very low. These material are having very high resistivity which makes them very suitable to insulate the current carrying parts from earthed metallic structure. In insulating materials the elections are tightly bounded with nucleus. Due to which that cannot be freed for movement in materials. Due to which the resistivity of insulating materials is very high. Example:- Plastics, Ceramics, PVC etc.

Magnetic Materials


These materials play an important role for existence of various electrical machines. The magnetic materials having high permeability are used for building the core to from the low reluctance path for magnetic flux. Magnetic materials can be further divided in following categories

  • Ferromagnetic materials

  • Paramagnetic material

  • Diamagnetic materials

  • Antiferromagnetic materials

  • Ferrites

Ferromagnetic Materials


These materials are having very large and positive susceptibility to external magnetic field. They are having a strong attraction to external magnetic field and are able to retain magnetism even after remove of external magnetic field. This property of materials is called magnetic hysteresis. Example: Iron, Cobalt, Nickel.

Paramagnetic Material


These materials are having very small and positive susceptibility to external magnetic field. In the presence of external magnetic field, these materials attains very small magnetism. Example: Aluminum, Platinum, oxygen, Air etc.

Diamagnetic materials


These materials are having very weak and negative magnetic susceptibility to external magnetic field. On application of external magnetic field these are repelled slightly by external magnetic field. These materials does not retains the magnetism after removal of external magnetic field. Mostly all metals i.e. silver, copper, gold, hydrogen etc. are diamagnetic materials.

Antiferromagnetic materials


These materials are having very small and positive susceptibility to external magnetic field. In the presence of external magnetic field these materials get slightly magnetized in the direction of external magnetic field. In these materials, atoms are having mixed parallel and anti parallel aligned magnetic dipole movement. Example: Cr, MNO, FeO, CoO, NiO, Mn etc.

Ferrites


These materials are having very large and positive magnetic susceptibility like ferromagnetic materials. These materials are generally compound which are having more complex crystal structures than a pure material. As compare to ferromagnetic materials, ferrites are having lower magnetic saturation. Example: Fe3O4, BaO.6Fe2O3 etc.

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Electrical for Us: Classification of Engineering Materials
Classification of Engineering Materials
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