nature and properties of materials

1. SUBMITTED TO:
SUBMITTED BY:
Nature and
properties of
materials
Mr. Kamal Sanguri
H.O.D. Mechanical Dept.
GEHU Bhimtal
Saurabh Negi
M.E. V Sem
2061443 (02)

2. Content:
• History and Evolution of Materials
• Classification of materials
• Macroscopic Structures of Matter
• Imperfections (Defects) in Crystals
• Iron
• ferrous alloys
• Ceramics
• Polymers
• Polymer classification
• Smart materials
• Shape Memory alloys
• Optical fibers

3. History and Evolution of Materials
STONE AGE(15000-2000 BC):
•Stone age was coined in late 20th century which uses
Wood, Bones and Stones were used as Tool.
BRONZE AGE(3500-500BC):
•Bronze age was the beginning of thre metal working.
•Copper was mixed with tin to create new alloy
BRONZE.
IRON AGE(3000 years ago):
•Iron age was the last stage of Archeological Sequence.
•Witnessed Industrial Revolution .
•Use of iron in huge amount started.

4. Iron pillar of Delhi:
•Solid rod of wrought iron (high phosphorous
content), about 7m long, 0.4 m diameter ,
weighing over 6000 kg.
•High resistant to corrosion result from layer
of crystalline iron hydrogen phosphate
hydrate which serves to protect it from severe
Delhi climate.

5. Classification of Materials:
METALS &
ALLOYS
NON
METALS
Gases-H2,N2
CEREMICS
AL2O3
SiC
diamond
POLYMER
S
Silk
PVC
Nylon
Bakelite
COMPOSITE
S
Wood
Concrete
Fiber GlassFERROU
S
Iron
Steel
NON
FERROUS
Aluminium
Copper
Zinc

6. Metals:
•They can conduct electricity and heat.
•They can be formed easily.
•They have a shiny appearance.
•They have a high melting point.
•Examples of metals
are aluminium, copper, iron, tin, gold.
Non Metals:
•They are poor conductor electricity and
heat.
•Brittle if solid.
•Non Ductile.
•Examples are hydrogen,
helium, oxygen, nitrogen, fluorine

7. Ceramics:
A ceramic is an inorganic, non-metallic, solid material
comprising metal and non-metal.
Formed by action of heat and subsequent cooling.
General properties are:
•High melting temperature
•High hardness
•Poor conductivity
•Chemical resistance

8. Polymers:
A polymer is a large molecule,
or macromolecule, composed of many
repeated subunits.
Polymers range from familiar synthetic
plastics such as polystyrene to
natural biopolymers such
as DNA and proteins

9. Composite :
composite material is a material made from two or
more constituent materials with significantly
different physical or chemical properties .
The individual components remain separate and
distinct .
composites are stronger, lighter, or less expensive
when compared to traditional materials.

10. Macroscopic Structures of Matter
Atoms and molecules are the building blocks of more
macroscopic structure of matter .
When materials solidify from the molten state, they tend
to close ranks and pack tightly, arranging themselves into
one of two structures:
− Crystalline
− Noncrystalline

11. Crystalline Structure
Structure in which the atoms are located at regular and
recurring positions in three dimensions .
Unit cell - basic geometric grouping of atoms that is
repeated .
The pattern may be replicated millions of times within a
given crystal .
Characteristic structure of virtually all metals, as well as
many ceramics and some polymers.
Three types of crystal structures in metals: -
(a) body centered cubic
(b) face centered cubic
(c) hexagonal close packed

12. Imperfections (Defects) in Crystals:
Imperfections often arise due to inability of solidifying material to
continue replication of unit cell, e.g., grain boundaries in metals .
Imperfections can also be introduced purposely; e.g., addition of
alloying ingredient in metal .
Types of defects:
1. Point defects
2. Line defects
3. Surface defects

13. Noncrystalline
(Amorphous) Structures:
an amorphous or non-crystalline solid is a solid that
lacks the long-range order that is characteristic of
a crystal.
− Water and air have noncrystalline structures
A metal loses its crystalline structure when melted .
Polymers are often amorphous. Other types of
amorphous solids include gels, thin films, and
nanostructured materials such as glass.

14. Iron:
Iron is a chemical element with symbol Fe (from Latin: ferrum) and atomic
number 26.
It is the fourth most common element in the Earth's crust.
Allotropes of iron:
T<770 ˚C= ferrite(α-iron), ferromagnetic,BCC crystal structure.
770<T<912 ˚C=β iron,paramagnet , BCC structure.
912<T<1394 ˚C=γ- iron(Austenite), FCC crystal structure.
1394<T<1538 ˚C=δ-iron, BCC crystal structure.

15. ferrous alloys:
Carbon steels are ferrous alloys that contain carbon and small
levels of other alloying elements, such as manganese or
aluminum.
Alloy steels contain low to high levels of elements such as
chromium, molybdenum, vanadium and nickel.
Stainless steels are highly corrosion resistant, ferrous alloys that
contain chromium and/or nickel additions.
Cast iron, a ferrous alloy, contains high amounts of carbon.
Ductile iron, gray iron and white cast iron grades are types of cast
iron.

16. Plain carbon steel:
Carbon steel, or plain-carbon steel, is a metal alloy . It is a combination of two
elements, iron and carbon. Other elements are present in quantities too small to affect
its properties. The only other elements allowed in plain-carbon steel
are: manganese (1.65% max), silicon (0.60% max), and copper (0.60% max).
Types of carbon steel:
Mild (low carbon) steel:
approximately 0.05% to 0.25% carbon content with up to 0.4% manganese content (e.g. AISI 1018
steel). Less strong but cheap and easy to shape; surface hardness can be increased
through carburizing.

17. Medium carbon steel:
approximately 0.29% to 0.54% carbon content with 0.60 to 1.65% manganese
content(e.g. AISI 1040 steel). Balances ductility and strength and has good wear
resistance; used for large parts, forging and car parts.
High carbon steel:
approximately 0.55% to 0.95% carbon content with 0.30 to 0.90% manganese
content. Very strong, used for springs and high-strength wires.

18. cast iron:
Cast iron is a ferrous alloy that is made by re-melting pig iron in a cupola furnace
until it liquefies.
How is cast iron classified?
Based on the alloying elements added, the variation in the solidification of the cast iron and heat
treatment used, the microstructure of the cast iron can vary. Depending upon the application and
the preferred mechanical properties, iron castings can be classified into the following:
White cast iron
Grey cast iron
Malleable cast iron
Ductile cast iron

19. Types of cast iron:
White/Chilled cast iron:
No graphite , Carbon in form of carbides.
Formed by rapid cooling of melted iron.
Very hard ,wear and corrosion resistant.
Grey cast iron:
Carbon content varies from 2.5- 4 wt %C.
Graphite consist in form of flakes.
Graphite gives self lubricating properties and vibration damping properties.

20. Malleable cast iron:
The malleable cast iron is obtained from
white cast iron by a suitable heat treatment process(800-900’C),leads to
decomposition of cementite ,forming graphite in form of clusters.
Highly shock resistant and tough.
Applications – connecting rods,transmission gears etc
Ductile cast iron:
Obtained by adding small amount of magnesium to molten grey
C.I. leading to formation of graphite in form of spheres.
Tough, wear resistant.
Good machinability and weldability.

21. Ceramics:
ceramics materials are the inorganic crystalline materials made from
compounds of a metal and a non metal primarily held by ionic and
covalent bonds.
Common characteristics are:
Hard and brittle
Strong in compression weak in tension.
Chemically inert.
Insulators of heat and elecrticity (except diamond and graphite)
High and well defined melting points.

22. Abrasives:
Use to grind or cut away other relative softer materials.
Possesses high strength and wear resistance.
Typical examples are:
Silicon carbide, tungsten carbide, Al2O3, silica sand.
Refractories:
Usually used in furnaces operation around 1500 degree C.
Withstand high temperature without melting.
Remains unreactive and inert under severe environment.
Examples: alumina ,silica,bricks,magnese, BeO.

23. Piezoelectric electric ceramics:
Piezoelectric effect was discovered by Jacques and Pierre Curie in 1888.
Direct piezoelectric effect is the ability of some materials to create an electric
potential in response to applied mechanical stress.
The applied stress changes the polarization density within the material's volume
leading to the observed potential.
Some of the commonly used/known piezoelectric materials are quartz (SiO2),
zinc oxide (ZnO), polyvinylidenefluoride (PVDF) and lead zirconate titanate,
(PZT or Pb(Zr,Ti)O3).

24. Polymers:
A polymer is a large molecule of many repeated units.
Natural polymer: shellac(bio-adhesive),cotton, silk, natural rubber,
leather etc.
Synthetic polymer: synthetic rubber,bakelite,nylon,polystyrene,PVC.
Most polymers are made from oil, which is a non-renewable resource.
They are made by a chemical reaction called polymerization.
There are two main types of polymer:
thermosets and thermoplastics.

25. Polymer classification:
Molecular
structure:
•Linear
•Branched
•Cross linked
•network
Origin:
•Natural
•synthetic
Polymerization
Reaction:
•Chain
•step
Thermo physical
behavior:
•Thermoplastics
•thermosets
End use of
application:
•Plastics
•Elastomers
•Fibers
•Coatings
•Adhesives
•Films

26. Molecular structure:
Linear structure:
Units are joined together end to end in chains.
Soluble and fusible
Branched structure:
Side branch chains are connected to main ones.
More soluble and fusible.
Cross linked structure:
Adjacent linear chains are joined one to another at various positions by covalent bond.
Insoluble and infusible.
Network structure:
High cross linking and 3D structure
Insoluble and infusible.

27. Thermoplastic Polymers:
Heat sensitive-soften and flows upon heating.
Remains soluble and fusible under many cycles of heating and
cooling ,thus recyclable.
Most linear polymer and those having some branched structures
with flexible chains are thermoplastics.
Unlimted self life-wont undergo polymerization during storage.
Disadvantages: prone to creep.
Examples: polyethylene , polystyrene , polyvinyl chloride.

28. Thermosetting polymers:
They are network polymers.
Creep resistant.
Attains permanent hardness due to cross linking and then do
not soften and flows upon heating.
Excellent thermal and chemical stable once polymerized.
Disadvantages: brittle and non-recyclable.
Example : Bakelite , urethane etc.

29. Smart materials:
Smart materials are designed materials that have one or
more properties that can be significantly changed in a
controlled fashion by external stimuli, such
as stress, temperature,
moisture, pH, electric or magnetic fields.
his change is reversible and can be repeated many times.
Self sensing and actuating.

30. Piezoelectric materials : materials that produce a voltage when stress is applied.
Magnetostrictive materials : exhibit change in shape under the influence of magnetic field..
Phase transition dependent: Remembers its original shape after being deformed returns its original
shape when heated.
Electro magneto rheological materials : changes its viscosity in response to electo/magnetic field.
Self-healing materials: have the intrinsic ability to repair damage due to normal usage, thus
expanding the material's lifetime.

31. Shape Memory alloys:
Certain classes of metallic alloys have a special
ability to memorize their shape at a higher
temperature and recovers large deformation
imparted at a low temperature on thermal
activation.
The recovery of strains imparted to the
materials at a lower temperature as a result of
heating is called the shape memory effect.

32. SME was first observed in 1932 in gold cadmium alloys.
Three types of SMA are currently popular:
Cu Zn Al
Cu Al Ni
Ni Ti
The last one is commercially available as nitinol.
There are two common shape memory effect-one way and
two way effect.
In one way effect the materials remembers only the shape
at parent stage
In two way effect, the material is trained to remember two
shapes, one at the parent austenite phase and the other at
martensite phase.

33. Optical fibers:
Medium for carrying information from one
point to another in form of light.
Fiber optics is not electrical in nature unlike
copper form of transmission.
It has been calculated that it would require
30000 kg of copper to transmit the same
amount of information as only 0.1 kg of
optical fiber material.