What are Materials?
Materials may be defined as substance of which something
is composed or made.
We obtain materials from earth crust and atmosphere.
Examples : Silicon and Iron constitute 27.72 and 5.00 percentage of
weight of earths crust respectively.
Nitrogen and Oxygen constitute 78.08 and 20.95
percentage of dry air by volume respectively.
Why the Study of Materials is
Production and processing of materials constitute a large part
of our economy.
Engineers choose materials to suite design.
New materials might be needed for some new applications.
Example :- High temperature resistant materials.
- Space station and Mars Rovers should sustain conditions in space.
(* High speed, low temperature, strong but light.)
Modification of properties might be needed for some
Example :- Heat treatment to modify properties.
Materials Science and Engineering
Materials science deals with basic knowledge about the
internal structure, properties and processing of materials.
Materials engineering deals with the application of
knowledge gained by materials science to convert materials
Materials Science and
of Structure and
Type of Material
Most engineering materials are devided into three main or
In addition to the three main classes of materials, the other
two processing or application classes are:
Composed of one or more metallic elements.
(Example:- Iron, Copper, Aluminum)
Metallic element may combine with nonmetallic elements.
(Example:- Silicon Carbide, Iron Oxide)
Inorganic and have crystalline structure.
Good thermal and electric conductors.
Metallic Materials (cont..)
Metals and Alloys
Fig: The aircraft turbine
engine is made principally
of metal alloy.
Polymeric (Plastic) Materials
Organic giant molecules and mostly noncrystalline.
Some are mixtures of crystalline and noncrystalline regions.
Poor conductors of electricity and hence used as insulators.
Strength and ductility vary greatly.
Low densities and decomposition temperatures.
Examples :Poly vinyl Chloride (PVC), Polyester
( Applications :- DVDs, Fabrics etc. )
Metallic and nonmetallic elements are chemically bonded together.
Inorganic but can be either crystalline, noncrystalline or mixture of
High hardness, strength and wear resistance.
Very good insulator. Hence used for furnace lining for heat treating
and melting metals.
Also used in space shuttle to insulate it during exit and reentry into
Other applications : Abrasives, construction materials, utensils etc.
Example:Porcelain, Glass, Silicon nitride.
Composite Materials (cont..)
Mixture of two or more materials.
Consists of a filler material and a binding material.
Materials only bond, will not dissolve in each other.
Mainly two types :o Fibrous: Fibers in a matrix
o Particulate: Particles in a matrix
(Matrix can be metals, ceramic or polymer)
Examples : Fiber Glass ( Reinforcing material in a polyester or epoxy
Concrete ( Gravels or steel rods reinforced in cement and
Applications:- Aircraft wings and engine, construction.
Not major by volume but very important.
Silicon is a common electronic material.
Its electrical characteristics are changed by adding impurities.
Examples:Silicon chips, transistors
Applications :Computers, Integrated Circuits, Satellites etc.
Competition Among Materials
• Materials compete with each other to exist in new market
• Over a period of time usage of different materials changes
depending on cost and performance.
• New, cheaper or better materials replace the old materials
when there is a breakthrough in technology.
Predictions and use of
materials in US automobiles.
Recent Advances and Future
React to environment Stimuli (temperature, strees, light,
humidity and electric and magnetic field).
Change their properties by sensing external stimulus.
Examples: Shape memory alloys – used in the artery stents.
Microelectromechanical systems (MEMS) devices.
Smaller than 100 nm particle size.
Materials have special properties.
Very hard and strong characteristics.
Research in progress.
Example: Carbon nanofiber reinforced plastic: very
light but stronger than metals.
Force between particles
Nucleus of one ion attracts electron of another ion.
The electron clouds of ion repulse each other when they
are sufficiently close.
These two forces will balance each other when the
equilibrium interionic distance, a0, is reached and a bond is
Fig 2.16 The attraction repulsion forces
developed during ionic bonding. Note
that net force is zero when the bond is
Fnet = Fattraction + Frepulsion
Z1,Z2 = number of electrons removed or added during ion formation
= electron charge = 1.6 x 10-19C
= 8.99 x 109 Nm2/C2
= interionic seperation distance
Calculate the force of attraction between Na+ and Cl- ions.
Z1 = +1 for Na+
Z2 = -1 for Cle = 1.60 x 10-19 C
ε0 = 8.85 x 10-12 C2/Nm2
a0 = sum of radii of Na+ and Cl- ions
= 0.095 nm + 0.181 nm
= 2.76 x 10-10 m
(1)(1)(1.60 10 C )
Z Z e
4 a 4 (8.85 x 10 C /Nm2)(2.76 x 10
3.02 109 N
Frepulsion = -nb
n and b = constant
= interionic distance
The repulsion force between Na+(r = 0.095nm and Cl- (r = 0.181nm) ions at
equilibrium is -3.02 x 10-9N. Assume n = 2. Calculate the value of constant
A.G. Guy (1972) Introduction to Material Science, McGraw
J.F. Shackelford (2000). Introduction to Material Science for
Engineers, (5th Edition), Prentice Hall.
W.F. Smith (1996). Priciple to Material Science and
Engineering, (3rd Edition), McGraw Hill.
W.D. Callister Jr. (1997) Material Science and Engineering: An
Introduction, (4th Edition) John Wiley.