Material Science : Chapter 1: Introduction

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June 27, 2017

 

1. Historical Perspective

1.1 Stone age
1.2 Bronze age
1.3 Iron age
1.4 Steel age
1.5 Golden age
1.6 Electronics age
1.7 Space age

2. Material science

2.1 Why study about material science

3. Classification of materials

3.1 Metals
3.2 Ceramics
3.3 Polymers
3.4 Composite materials
3.5 Semiconductors
3.6 Biomaterials

4. Important materials use
5 FAQs

1. Historical Perspective

Materials are very important in human civilization. This is evident from the names given to the early civilization based on the materials used.

1.1 Stone age

  • Natural materials like stone, clay and wood etc..
  • Need of better quality materials led to exploration of new material and thus the periods are named after these materials.

1.2 Bronze(Copper + Tin) age

  • Found copper and alloying the same to make it harder.

1.3 Iron age

  • Use of iron which is abundant in nature and available to everyone, Because of this, Iron gained the name Democratic material.
  • This brought told and utensils into use.

1.4 Steel age

  • This is produced by alloying the iron.
  • This is a strong and corrosive resistant which revolutionized the use of materials in everyday life.
  • This brought railroads, infrastructure and industrial revolution.

1.5 Golden era

  • Introduction of plastics revolutionized 20th century.

1.6 Electronics age

  • Invention of materials which are mainly used in electronic gadgets.
  • Examples are semiconductors and superconductors.
  • Silicon (Si) is the heart of every electronic component.

1.7 Space age

  • Stronger and lighter materials are developed by using technology.
  • Examples are composites, high temperature ceramics (for space voyage).
  • This age is contemporary to the electronics age.

Flow chart {1}

Below diagram represents improvement in strength of different materials with time periods

2. Material Science

  • Different materials behave in different ways and they also differ in properties.So it is imperative to study materials at atomic level to understand them well.
  • That is the reason that Material Science can be broadly defined as correlation between microstructure and properties

Important components of the subject Materials Science are structure, properties, processing, and performance

  • Application dictates the performance of the material which in turn depends on the properties of the materials.
  • But again properties can be known only by understanding the structure.By knowing above all, suitable process should be chosen to manufacture materials to meet desired performance.

2.1 Why study material science and engineering?

  • Innovation in engineering often means the clever use of a new material for a specific application.
  • For example: plastic containers in place of age-old metallic containers.
  • So it is vital that the professional engineer should know how to select materials which best fit the demands of the design – economic and aesthetic demands, as well as demands of strength and durability

3. Classification of materials

These are classified in groups, like any other things to reduce complexity on our brain. Below are important type of classification

3.1 Metals

  • Characterized by high thermal and electrical conductivity
  • Strong yet deformable under applied mechanical loads
  • Shiny if polished
  • Atoms are connected by metallic bonds and weaker Van Der waals forces
  • Alloy – mixing of a metal with another metal, is a specialty of the metals to get desired strength
  • Eg: Aluminium, Steel, Iron etc..

3.2 Ceramics

  • Inorganic compounds[FAQ 1] (materials without carbon atoms), usually made either of oxides, carbides, nitrides or silicates of metals
  • Partly crystalline(clearly defined shape) and partly amorphous(no clearly defined shape)
  • Atoms are bound by Coulomb forces[FAQ 2]
  • High strength under compression
  • Low ductility
  • Usually insulators to hear and electricity
  • Eg: glass, porcelain, and many minerals

3.3 Polymers

  • Thermo-plastics consist of molecules that have
    • covalent bonding within each molecule
    • van der Waals forces between the molecules.
    • Eg:nylon, polyethylene, polyvinyl chloride, rubber, etc.
  • Thermo-sets consist of
    • Network of covalent bonds.
    • They are based on H, C and
    • Other non-metallic elements.
    • Eg: epoxy, phenolics,
  • Polymers are amorphous, except for a minority of thermoplastics.
  • Due to the kind of bonding, polymers are typically electrical and thermal insulators.
  • Conducting polymers can be obtained by doping, and conducting polymer-matrix composites can be obtained by the use of conducting fillers.

3.4 Composite materials

  • These are multiphase materials
  • Obtained by artificial combination of different materials to attain properties that the individual components cannot attain.
  • Famous example is reinforced cement concrete, a structural composite obtained by combining cement, sand, gravel, and thick steel fibers.
  • In general, composites are classified according to their matrix materials.
  • The main classes of composites are metal-matrix, polymer-matrix, and ceramic-matrix.

3.5 Semiconductors

  • These are covalent in nature.
  • Their atomic structure is characterized by the highest occupied energy band [FAQ 3].
  • Their electrical properties depend extremely strongly on minute proportions of contaminants.
  • They are usually doped[FAQ 4] in order to enhance electrical conductivity.
  • They are used in the form of single crystals without dislocations because grain boundaries and dislocations would degrade electrical behavior.
  • They are opaque to visible light but transparent to the infrared.
  • Eg: silicon (Si), germanium (Ge), and gallium arsenide (GaAs, a compound semiconductor).

3.6 Biomaterials

  • To damaged or diseased human body parts.
  • they must be biocompatible with body tissues, and must not produce toxic substances(primary requirement)
  • Typical applications involve heart valves, hip joints, dental implants, intraocular lenses.
  • Eg: Stainless steel, Co-28Cr-6Mo, Ti-6Al-4V, ultra high molecular weight poly-ethylene, high purity dense Al-oxide, etc.

4. Important materials and their applications

  • Aluminium – automobile cylinder blocks and cylinder head
  • Ni based superalloys – high temperature applications like in aircraft engines
  • Si(silicon) – in every electronic component
  • Zone refining – metallurgical process to produce high purity Si

5. FAQs

1.What is the difference between organic and inorganic compounds?

Ans: The primary difference between organic compounds and inorganic compounds is that organic compounds always contain carbon while most inorganic compounds do not contain carbon. Also, nearly all organic compounds contain carbon-hydrogen or C-H bonds.

2. What is Coulomb force?

Ans: Coulomb force, also called electrostatic force or Coulomb interaction. This is an attraction or repulsion of particles or objects because of their electric charge.

Two like electric charges, both positive or both negative, repel each other along a straight line between their centres. Two unlike charges, one positive, one negative, attract each other along a straight line joining their centres.

3. What is meant by highest occupied energy band? 

Ans: The valence band(where the valence electrons reside energetically) is full such that the energy gap between the top of the valence band and the bottom of the empty energy band (the conduction band) is small.

4. What is the meaning of doping in semiconductors?

Ans: Doping means the introduction of impurities into a semiconductor crystal to the defined modification of conductivity

Normally Trivalent and Pentavalent elements are used to dope Silicon and Germanium

 

References

  1. William D. Callister, Jr.David G. Rethwisch: Materials Science and Engineering: An Introduction, Wiley publication, 2014
  2. NPTEL material science material by Satish Vasu Kailas (IISc)

6 Comments

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  3. vishant sharma says:

    is these topics are enough for prelims …..or i have to refer more book

  4. wrishiraj sharma says:

    plzz add more if possible

  5. yogendra singh says:

    Sir It is mentioned in 3.2 that Inorganic compounds Inorganic compounds are materials without carbon atoms and example given Carbides. But My doubts is Carbides are made up of Carbon So if Inorganic compounds are materials without carbon atoms then how can we consider carbides in it?

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