Engineering chemistry II for polytechnic students for easy learning and revising them

2. What is a composite material?
The composite materials are
generally made by placing
the dissimilar materials
together in such a manner
that they work as a single
mechanical unit.
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Composite Steel Aluminium
Weight
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Composite Steel Aluminium
Thermal Expansion

3. Advantageous Properties of the composites over
metals polymers ceramics
 Higher specific strength.
 Lower specific gravity.
 Higher specific stiffness.
 Lower electrical conductivity.
 Better corrosion and oxidation
resistance.
 Can be fabricated easily.
 Lower specific gravity.
 They are tough having good
impact and thermal shock
resistance.

4. Constituents of Composites
Matrix Phase is the continuous
body constituent which encloses
the composite and give it its bulk
form. Matrix phase may be
metal, ceramics (or) polymers.
Dispersed Phase is the
structural constituent which
determines the internal structure
of composite

5. Application of
composite
materials:
Fabrication of roofs and floors.
Communication
antennae, electronic circuit boards,
sport goods, furniture and turbine
engines. They are also extensively
used in automobile industries marine
applications like propellers, spares,
ship parts.

6. Plywood

7. Ceramics
Ceramic is an in-organic non-metallic
materials that are processed at high
temperatures, and subsequent cooling. eg.
ceramic wash basin, ceramic tiles etc.

8. White Pottery
 White ware products consist of
refractory body and glossy'
coating. They are white ceramic
materials that are white in colour.
 The raw materials used for
manufacture of white pottery, are
given below.
 China Clay
Feldspar (KAlSiO2)
Flint(SiO2)

9. MANUFACTURE OF WHITE POTTERY
 Step I Preparation of
body ware
 The raw materials Kaoline
[Al (OH)4 SiO5] and
Feldspar are made into fine
powder and mixed with
water to form a creamIt is
dried and then fired in a
'biscuit' oven to get porous
ware called 'Bisque’

10. Step II Glazing
 In order to make the porous ware
into watertight article, it is covered
with glaze by melting it over the
surface of the body.
 The constituents of glaze material
are quartz, feldspar, little boric acid
and little lead oxide.
 The bisque is dipped in the glaze
slurry and fired again at high
temperature until the glaze
materials melt to form a smooth
glossy surface.
 Step-Ill
 Decoration
 The article is decorated with paints
before glazing or it is decorated with
coloured glass after glazing

11. Purpose of Glazing
 To get decorative effect.
 To make the surface impervious to
liquids.
 To improve appearance of the
article.
 To increase the durability of ceramic
material.
 To get a smooth glossy appearance.
 To protect the surface from
atmospheric action.
 Salt glazing
 In salt glazing, common salt
(sodium chloride) is used for getting
glossy films over earthenware. The
process consists of throwing NaCl
into furnace when the article is in
red-hot condition.

 At high temperature, NaCl melts
and reacts with silica of the article
to form a glossy and impervious film
of 'Sodium Silicate'

12. Uses
 Spark plugs
 Electrical Insulators
 Lab equipments
 Crucibles and dishes etc

13. Refractories
 Refractories are materials,
which can withstand high
temperatures.
 mostly used for linings of
the furnaces, tanks,
converters, kilns, crucibles,
ladles etc

14. Requirements of a good refractory:
 Refractoriness: It is the ability to withstand
very high temperature without deformation
during operation.
 Strength or Refractoriness under load
(RUL): They must
possess high mechanical strength even at very
high temperature and bear maximum possible
load without breakage.
 Thermal expansion: A good refractory
should have low thermal expansion under
normal conditions.
 Thermal conductivity: In general a good
refractory must have low thermal conductivity
to reduce heat losses by radiation. But when
heat is to be supplied from outside the
refractory must possess good conductivity.
 Porosity: A good refractory should have low
porosity. In porous refractory the molten
metal and slag enters and weaken the
structure. But porosity helps in thermal
shock-resistance of refractories.
 Thermal spalling: It is breaking, cracking,
peeling off or
fracturing of the refractory under high
temperature. A good
refractory must have low thermal spalling.
 Chemical composition: A good refractory
must be chemically inert with charge and slag.

15. Classification:
. Acid
refractories
Silica (SiO2
. Basic
refractories
Magnesia (MgO)
2. Dolomite
. Neutral
refractories
Chromite
(Cr2O3)
Alumina (Al2O3)
 Used in furnaces where the charge
and slag are acidic in nature
 Used in furnaces where the charge
and slag are acidic in nature
 Used in furnaces where the charge
and slag are acidic in nature

16. Acid refractories

17. Lubricants
 “Lubricants may be
defined as the Substance
which reduces the
friction between the two
moving surfaces”.

18. Characteristics of Lubricants:
 It should have a high viscosity
index.
 It should have flash and fire
points higher than the operating
temperature of the machine.
 It should have high oiliness.
 The cloud and pour points of a
good lubricant should always be
lower than the operating
temperature of the machine
 The volatility of the lubricating
oil should be low.
 It should deposit least amount
of carbon during use.
 It should have higher aniline
point.
 It should posses a higher
resistance towards oxidation and
corrosion.
 It should have good detergent
quality.

19. Classification of Lubricants:
Solid Lubricants Graphite
Molybdenum
disulphide
Semi – solid
Lubricants
Greases
Vaseline’s
Liquid
Lubricants
Vegetable oils –
eg: palm oil &
castor oil
Animal oils - eg:
Whale oil & lard
oil
Mineral oils – eg:
petroleum
fractions

20. Thank you