Basics of material science , Crystallography , GATE & ESE , General studies

 Material science

• It deals with investigating the relationship between structures and properties of the materials.
• In contrast material engineering deals with designing the structures by using materials on the basis of structure properties and correlations.

What is material ?

It is the stuff with the help of which we can design something . It consist of matter.

Engineering materials can be classified as 

1. Metals and alloys
2. Ceramics and glasses
3. Organic polymers
4. Composites

Structure

It is the arrangement of components , the structure for the material can be categorised in following ways:

1. Macrostructure : 

• Observed with naked eye or under low level magnification.
• The internal symmetry of atoms can reflect in the macrostructure of material.

2. Microstructure :

• It is the structure which observed with the help of an optical microscope without the loss of information, with an optical microscope , a magnification of approx 1500 times linear is possible.
• The structure observed by a microscope having very high magnification and resolution than optical microscope is known as substructure . for eg with electron microscope a magnification of 1000000 times linear is possible. 

3. Crystal structure : 

• It deals with the arrangement of atoms in crystalline solids . The arrangement of atoms in crystal can be described in terms of a unit cell.

Unit cell: It is defined as the smallest group of atoms by repeating which in all the directions crystal is formed.

4. Electronic structure :

• It deals with arrangements of electron in various orbits of atoms .

5. Nuclear structure :

• It studied with the help of spectroscopic techniques such as Nuclear  magnetic resonance (NMR) and Massbauer studies .

• In nuclear structure we study the number of nucleons present in the nucleus.

Property

It is defined as the material traits in terms of kind and magnitude of response for an external imposed stimulus .

Material properties can be of following types :

• Mechanical property 
• Electric property 
• Magnetic \property 
• Thermal property 
• Optical property 
• Deteriorative property 

Crystallography

• It is a branch of science in which the internal structure of crystals , the properties of crystalline material and the internal and external symmetries possessed by crystalline solids are studied.
• Crystallography methods depend on the analysis of the diffraction pattern of a sample targeted by a beam of x rays , neutrons , electrons.

Crystalline solids

• Atoms are packed in periodic manner.
• Well defined diffraction pattern is observed.
• High density
• Sharp melting point

Non crystalline solids

• Atoms are packed in random manner.
• No such pattern is observed 
• Low density
• Melts over the range of temperature 

Amorphous materials

• Systematic and regular arrangement of atoms over large atomic distances , so these materials are called as amorphous materials or super cooled liquids (as their atomic structures resembles with that of liquid).
• Whether an crystalline solids or an amorphous solid forms it depends on the ease with which random atomic structure in the molten state can be arranged in an ordered state during solidification. Further more rapidly cooling through freezing temperature favours formation of non crystalline solid as little time is allowed for the ordering process.