1. CHAPTER 1
Part 1
MATERIAL STRUCTURE
AND
BINARY ALLOY SYSTEM

2. Atomic Structure
nucleus
Electron : charge magnitude : -1.60x10-19 C
Proton : + 1.60x10-19 C
Neutron : neutral, no charge
• Is the basic unit of matter.
• 3 basic particles of atoms are : ELECTRON, PROTON AND NEUTRON
Remember an atom will contain equal number of P and E !!

3. Element structure
• Is the substance that is made up from one type of atom.
• Cannot be broken down into any simpler substances by chemical
method.
• Has its own atomic mass.
• Has equal number of protons and number of electrons.
Example : Hydrogen is made up of one type of atom containing 1
proton and 1 electron.

4. MOLECULE AND COMPOUND
MOLECULE : 2 OR more atoms that are chemically joined together.
Example : H2, O2 , H20
COMPOUND : contains more than 1 type element. ( at least 2
different elements)
Example : H20 , CO2, NH3
Remember : All compounds are molecules but not all molecules are
compounds!!
H2 O2 H20
Molecules but not
compound because each
is composed of a single
element
Molecule and compound

7. The Periodic Table
• Is a tabular arrangement of chemical elements.
• Is organized on the basis of their atomic number,
electron configuration and recurring chemical
property.
• Elements are presented in order of increasing atomic
number ( number or proton)>> row
• Elements arrayed in similar electron structure as well
as chemical and physical properties >> column

9. HOW TO FIND NUMBER OF PROTON , ELECTRON
AND NEUTRON OF AN ELEMENT ?
6
C
CARBON
12.011

10. Try this

11. CRYSTALLINE STRUCTURES
• Atoms in crystalline solids : positioned in an order and repeated pattern.
• The repetitive entities in such structure is called the unit cells.
• Most common metals exists in at least one of three relatively simple crystal
structures; which is
a) BCC – body centered cubic b) FCC – face-centered cubic
b) HCP – hexagonal close-packed

12. Example : Atomic Radii and Crystal Structure for
few metals

13. BCC Structure
• Has cubic unit cell with atoms located at all 8 corners and a single atom at the cube
center
• Has two atoms per unit cell, one in the center and 1/8 of each of the 8 corner atoms.
• Lattice parameter @ length of unit cell can be calculated by using the following formula.
cellt2atoms/uni1)(18)
8
1
(atomsofNumber 
a
a
R 3
4R
a 
Where,
R = atomic radius
a = unit cell length

15. FCC Structure
• Has atoms located at each of the corners and centers of all the cube faces.
• Has 4 atoms per unit cell, one-half at each of six faces and 1/8 of each of the 8
corner atoms.
• Lattice parameter @ length of unit cell can be calculated by using the following
formula , where, a=unit cell length and R= atomic radius.
cellt4atoms/uni)
2
1
(68)
8
1
(atomsofNumber 
a
a
4R
R
22Ra 

16. HCP Structure
• Has a unit cell that is hexagonal.
• The top and bottom faces consists 6 atoms that form a regular hexagons
and surround a single atom in the center.
• Another plane consists 3 additional atoms which is situated in the middle.
• Has 6 atoms per unit cell, 1/6 of each of the 12 top and bottom face corner
atoms, ½ of each of the center face atoms and 3 midplane interior atoms.
Where a and c
represents the short
and long unit cell
dimensions
respectively

17. Terms in Recrystallization Process
• Is the formation of a new set of strain-free grains within a
previously cold-worked material usually by an annealing heat
treatment.
• Crystal structure – the manner in which atoms/ions are arrayed in
space.
• Space lattice – the regular geometrical arrangement of atoms
Lattice Not Lattice

18. Space Lattice and Crystal

19. Terms in Recrystallization Process
2 different
orientations
of grains
Grain Boundary
•Grain – an individual crystal in a polycrystalline metal or ceramic.
•Grain Boundary – the interface separating two adjoining grains
having different crystallographic orientations.

20. Atomic Bonding in Solids
• Atomic bonding is the interatomic forces that bind the atoms
together.
• There are primary and secondary bonds found in solids:
Primary / Chemical Bonding > stronger bonds
 3 types of primary bond:-
 Ionic
 Covalent
 Metallic
Secondary / Physical Bonding > weaker bonds
 2 types of secondary bond:-
 Van der Waals
 Hydrogen

21. Ionic Bonding
• Electrically charged ions are formed by the transfer of electron
from one atom to another.
• Found in compounds composed of both metallic and nonmetallic
elements.
• Example : NaCl , MgO
• Characteristics :
stable, hard, brittle,
electrically and
thermally insulative.
Tendency to lose outermost
electrons
( donor > +ve ion)
Tendency to gain
electrons
(acceptor > -ve ion)

22. Covalent Bonding
• Involving sharing of electrons between adjacent atoms.
• 2 atoms that are covalently bonded will each contribute at least 1e
to the bond.
• Nonmetallic elemental molecules ( H2, Cl2, F2) and molecules
containing dissimilar atoms ( CH4, H2O, HNO3, HF) are covalently
bonded.
• Characteristics : Varies
Diamond ( strong, hard, high melting temperature)
Bismuth ( very weak, low melting temperature)
(Methane)

23. • Valence electrons form a “sea of electrons” that is uniformly dispersed
around the metal ion cores and act as a form of glue for them.
• Found in metals and their alloys. Ex: Fe (iron), W (tungsten)
• Characteristics:
 Good electrical and thermal conductors due to their free valence electrons
 Opaque neither transparent (allowing all light to pass through) nor
translucent (allowing some light to pass through)
 Ductile (material's ability to deform under tensile stress(stretched into a wire)
Metallic Bonding
Metal ions / Ion cores
Sea of electrons /
Electron cloud

24. • Van der Waals
 resulted from attractive forces between electric dipoles.
 Weakest bond
 Exists between all atoms or molecules, inert gas (which has
stable e structure, and between covalently bonded molecules.
 Ex : Ar, Cl2
• Hydrogen bonding
 Most common in covalent bonded molecules.
 Found to exist between some molecules that have hydrogen as
one of the constituents.
 Ex : NH3, H2O
Secondary Bonding
+ - + -
Atomic or molecular dipoles
Van der Waals
bonding
between two
dipoles

25. THE END