for engineering chemistry

1. COMPOSITE MATERIALS

2. Composites are engineered materials, comprising
of metals, ceramics, glasses and polymers.
The composites obtained using respective material
exhibits unique properties or qualities.
The composites have better characteristic as
compared to those possessed by constituents.
Sometimes all together new/different
characteristics is observed to be possessed by
composite materials which is not present in either
of its constituents.

3. A composite in true sense must show matrix
material surrounding its reinforcing material, in
which the two phases not only exists but acts
together so as to produce desired
characteristics.
Examples: Wood contains cellulose chain
polymers in matrix of lignin, is example of
natural composite.
Synthetic composites such as rain proof cloths
(cloth impregnated with waterproof materials)
and Reinforced concrete, Insulated tape.

4.  Defn_ A multiphase product made by using two or
more existing materials which exhibits properties of
its constituents as well as shows certain unique
properties of its own.
 For Aerospace engineering materials with certain
specific properties are required, Such material should
have properties: Low density, high stiffness, high
strength, High resistance to abrasion.
 All above mentioned properties are contradictory to
each other like to have high strength, density has to
be high, but by combination of low density materials
with high strength material this is possible.


5. Thus two essential constituents of composites are
a) The Matrix phase, b) Dispersed phase

The matrix phase: It is the continuous body
constituent, which encloses the composite and gives
it its bulk form.
Matrix phase may be metal, ceramics or polymer.
When composites are prepared by using these matrix
are known as metal matrix composites (MMC),
ceramic matrix composites (CMC) and polymer
matrix composites (PMC) respectively.
Polymer matrix materials used in composites are
epoxy, polyamide (nylons), phenolics & silicons.

6.  Properties of Matrix phase:
The good matrix phase should be ductile and
corrosion resistant.
It should get bonded to fibre (dispersed phase) very
strongly.
 Elastic modulus of the matrix should be much lower
than that of the dispersed phase.
 Since some ductility is essential, only metals and
polymers are used as the matrix materials. Metals
like Al & Cu, commercial thermoplastic and
thermosetting polymers are generally used as the
matrix materials.

7. Functions of matrix phase:
i) It binds the dispersed phase together.
ii) It acts as a medium by which an externally
applied stress is transmitted and distributed to the
dispersed phase.
 iii) It prevents propagation of brittle cracks.
 iv) It protects the dispersed phase from surface
damage due to mechanical abrasion or chemical
reactions with the environment and keeps in
proper position and orientation during the
application of loads.

8. Dispersed phase:
 It is the structural constituent, which determines
the internal structure of composite. The
important dispersed phases of composites are,
 A) Fiber and B) Particulates
A) Fiber: It is a long and thin filament of any
polymer, metal or ceramic having high length to
diameter ratio. Its diameter nears crystal size
diameter. If matrix is unidirectional, then the
resulting composite is anisotropic.

9. Characteristics of Fiber:
i) The length to diameter ratio is very high (High
aspect ratio).
ii) It has high tensile strength.
iii) It causes lowering of overall density of composite.
iv) It has very high stiffness.
Types
Glass fiber, Carbon fibers and Aramid fibers.


10.  B) Particulate
 They are small pieces of hard solid metallic or
nonmetallic material. The particles are randomly
distributed in a given matrix, thereby resulting in
isotropic composite.
 The advantages of adding particulates to matrix
materials,
 i) Its surface hardness is increased.
 ii) Performance at elevated temperature is improved.
 iii) Abrasion elevated resistance is improved.
 iv) Shrinkage and friction is reduced.
 v) Cost of composite is reduced.
 vi) Its strength is increased.
 vii) Its thermal and electrical conductivities are modified.


11. Large
particle
Laminates
Composites
Structural
Fibre-reinforced
Sandwitch
panels
Particle- reinforced
Dispersion
Strengthened
Continuous
(long) aligned
Aligned
Discontinuous
(Short)
Randomly
oriented

12. Particle re-inforced composites
These composites are made by dispersing
particles of varying size and shape of one
material in a matrix of another material.
There are two types of Particle-reinforced
composites.
 A) Large particle composites
 B) Dispersion strengthened composites

The difference between these is based upon
reinforcement or strengthening mechanism.

13. Large particle composites
 In this type of composite particulate phase
should have following characteristics:
Stiffer and harder as compared to matrix
phase.
It acts as reinforcing material.
It restrains the movement of matrix
surrounding itself.
The bond strength between two phase
governs the mechanical properties of
composites

14. Material Matrix
phase
Particulate
phase
Properties
Concrete Cement Sand &
Gravels
R.C.C is harder than
ordinary cement
Sets well on
surface.
Cermets
Oxide based
Carbide based
Cr Al2O3 Good strength, very
good thermal shock
resistance
Co or Ni WC
TiC
Very hard, Very
high surface
hardness
Co or Ni CrC High abrasion and
corrosion resistance

15. Dispersion strengthened composite
 In this type of composite particle size is smaller
(10 to 100 nm)
 The metal and alloys are made into extremely small
particle size in the given range and are dispersed in
the matrix phase.
 This is achieved by appropriate heat treatment.
 The process is called as precipitation hardening or
age hardening.
 Alloys such as Cu-Sn, Mg-Al are hardened and made
into composite material by ceramics.

16. Fibre Reinforced Composites
These are the composite materials made up of
 a) A Polymer matrix,
 b) A Filament,
 c) A bonding agent.
Commonly used fibers are glass and metallic.
Properties of FRC
i) High tensile strength
ii) High specific gravity
iii) High elastic module
iv) High stiffness
v) They possess lower overall density.

17. Structural composites or
layered composite
This type of composites are of two types:
i) Laminar composites : e.g. Plywood
ii) Sandwich panel : Honeycomb core
Laminar Composites:
i) It consists of panels or sheets which are two
dimensional. These panels possess preferred
direction to achieve high strength.
eg. Plywood in which wood & continuous aligned
fibres reinforced plastics are in preferred
direction.

18. Fibre reinforced layers for laminar
composites

19. ii) such successively oriented layers are arranged
one above other with preferred direction. This
ensures high strength with each successive layer.
iii) Plywood is laminated composites containing
thin layer of woods where layers are alternatively
glued together. This type of layering brings grain
of each layer at right angles of its neighbouring
layer.
iv) Use of fabric material such as cotton, paper or
glass fibres dispersed in suitable plastic matrix is
also in practice to make laminar composite.

20. Properties:
Properties of these composites depends on
i) The properties of its constituents.
ii) The geometrical design.
Such composites are
i) Strong in both direction of reinforcement.
ii) Low shear strength.
Applications: i) Interior in premises
ii) False ceilings for diffused lighting
iii) Furniture making

21. Sandwich panel
 Sandwich panels are designed to be light- weight beams or panels
having relatively high stiffness and strengths.
 A sandwich panel consists of two outer sheets or faces that are
separated by and adhesively bonded to a thicker core.
 Faces are made of a relatively stiff and strong material, typically
aluminium alloys, fiber-reinforced plastics, titanium, steel or plywood.
Functions:
i) They impart high stiffness and strength to the structure.
ii) They must be thick enough to withstand tensile and compressive
stresses that result from loading.
The core material is light-weight has a low modulus of elasticity.
Typical “core” materials include synthetic rubbers, formed polymers,
balsa wood and inorganic cements.

22. Core serves the following structural functions:
i) It separates the “faces” and provides continuous support for the
faces.
ii) They resist any deformations perpendicular to the face plane.
iii) It provides a certain degree of shear rigidity along planes which
are perpendicular to the “faces”.
Core consists of a “honeycomb” structure thin foils that have been
formed into interlocking hexagonal cells, with axes oriented
perpendicular to the face plane.
The honeycomb material is normally either an aluminium alloy or
aramid polymer. Strength and stiffness of honeycomb structures
depend on cell size, cell wall thickness, and the material from which
the honeycomb is made.

23. Schematic diagram showing
construction of honeycomb core
sandwich panel

24. Schematic diagram showing cross section of a sandwich panel

25. 
Properties of sandwich panel:
i) Excellent dimensional stability.
ii) Resistant to abrasion and corrosion.
iii) High tensile strength.
iv) Low density.
v) High elasticity module.

26. Application of sandwich panel
Sandwich panels are used in a wide variety of
applications including roofs, floors, and walls of
buildings; and in aero planes and aircraft (i.e. for
wings, fuselage and tail-plane skins.)

27. Application of composite materials
The composite materials find variety of
application in all those areas where high
mechanical strength, thermal stability,
corrosion resistance, abrasion resistance
etc are desirable. They find application in
following industries:
Construction
Electrical & EXTC
Transportation
Agriculture
Aviation industries
Automobiles
Sports goods
Mobiles

28. Nanomaterials

30. 1. Surface-to-Volume Ratio: They have a high surface area
compared to their volume, making them highly reactive
and useful for catalysis.
2. Melting Point: Nanomaterials often have lower melting
points due to their size, which can be advantageous in
specific applications.
3. These materials are wear resistant, corrosion resistant
and chemically very reactive.
4. These materials are exceptionally strong, hard & ductile
at high temperatures.
5. The inert materials becomes catalysts e.g. Pt
6. The opaque substance becomes transparent. e.g. Cu
7. Insulators becomes conductors e.g. Si
Properties of nanomaterials

31. Types of Nanomaterials
a) Nanoclusters
b) Nanorods
c) Nanotubes
d) Nanowires

32. Nanoclusters
Nanoclusters are atomically precise, crystalline materials most often existing on
the 0-2 nanometer scale.
They are often considered kinetically stable intermediates that form during the
synthesis of comparatively larger materials such as semiconductor and metallic
nanocrystals.
These nanoclusters can be composed either of a single or of multiple elements,
and exhibit interesting electronic, optical, and chemical properties compared to
their larger counterparts
Particles in this sub-2-nm size regime show unique physical and chemical (or
physicochemical) properties, such as strong fluorescence, quantized charging,
discrete redox behavior, molecular magnetism, and optical chirality.

33. Nanorods
Nanorods
In nanotechnology, nanorods are one
morphology of nanoscale objects. Each of
their dimensions range from 1–100 nm.
They may be synthesized from metals or
semiconducting materials.
Standard aspect ratios (length divided by
width) are 3-5.
Nanorods are produced by direct chemical
synthesis.
A combination of ligands act as shape
control agents and bond to different facets
of the nanorod with different strengths.
This allows different faces of the nanorod
to grow at different rates, producing an
elongated object.

34. Nanowire
A nanowire is a nanostructure, with the
diameter of the order of a nanometer (10−9
meters).
It can also be defined as the ratio of the
length to width being greater than 1000.
Alternatively, nanowires can be defined as
structures that have a thickness or diameter
constrained to tens of nanometers or less
and an unconstrained length.
At these scales, quantum mechanical effects
are important — which coined the term
"quantum wires". Many different types of
nanowires exist, including superconducting
(e.g. YBCO), metallic (e.g. Ni, Pt, Au

35. Nanotubes
Generally nanotubes are mainly made of carbon.
Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical
nanostructure.
These cylindrical carbon molecules have unusual properties, which
are valuable for nanotechnology, electronics, optics and other fields
of materials science and technology.
Owing to the material's exceptional strength and stiffness, nanotubes
have been constructed with length-to-diameter ratio of up to
132,000,000:1, significantly larger than for any other material.

36. Nanomaterial Synthesis

37. Precipitation Method Three major Steps: i) chemical reaction, ii) nucleation and
iii) crystal growth.
Step 1:-Preparation of Precursor Solutions:
• Dissolution of Precursor material in a suitable solvent.
•The choice of precursor and solvent depends on the desired nanomaterial
composition and properties.
•The precursor may be a salt, a metal organic compound, or a combination of
reactants.
Step 2:- Precipitation:
• controlled addition of a precipitating agent to the precursor solution.
•Common precipitating agents include acids, bases, salts, or complexing agents.
•The addition of the precipitating agent triggers the nucleation and growth of the
nanomaterial.
Step 3:- Nucleation and Growth:
•Once the precipitating agent is added, nucleation occurs, leading to the formation of
small clusters or nuclei of the desired nanomaterial.
•It is influenced by factors such as temperature, concentration, and reaction kinetics.
•After nucleation, the nuclei grow in size through the continued supply of precursor
species from the solution.
•The growth mechanism can be controlled by adjusting reaction parameters such as
temperature, precursor concentration, and reaction time

38. Step 4:- Isolation and Purification:
• Nanoparticle separation using techniques such as centrifugation, filtration, or
sedimentation.
•These techniques allow for the isolation of the nanomaterial from the solvent and
any remaining reactants or by-products.
•The isolated nanomaterial is then washed and purified to remove any residual
impurities or solvent traces.
Characterization and Application:
•by microscopy, spectroscopy, and diffraction methods.
•These characterizations help verify the desired properties and quality of the
synthesized nanomaterial.
•The synthesized nanomaterial can then be used for various applications based on
its specific properties, such as catalysis, sensing, energy storage, or electronic
devices.

39. Thermolysis Method
Thermolysis is a method commonly used for the synthesis of various types of
nanomaterials.
Decomposition of precursor compounds at elevated temperatures to form nanoscale
particles.
Used to synthesize nanoparticles, nanocrystals, and nanowires.
Step 1:- Selection of Precursor:
 Suitable precursor compound that can decompose thermally to form the desired
nanomaterial.
 The precursor can be an organometallic compound, metal salts, metal complexes,
or other suitable compounds.
 The choice of precursor depends on the desired composition and properties of the
nanomaterial.
Step 2:- Solvent Selection:
 Choose an appropriate solvent or medium for the thermolysis process.
 The solvent should be compatible with the precursor compound and allow for the
dissolution or dispersion of the precursor.
 It should also have a high boiling point or good thermal stability to withstand the

40. Step 3:- Heating and Decomposition:
 Heat the precursor solution or dispersion at several hundred to a few thousand
degrees Celsius temp.
 This temp. is above the decomposition temp. of the precursor compound.
 The precursor undergoes thermal decomposition, leading to the formation of
intermediate species or atoms that further aggregate to form nanoscale particles.
Step 4:- Nucleation and Growth:
 Nucleation involves the formation of small clusters or nuclei from the decomposed
precursor species.
 These nuclei then grow in size through the addition of more precursor species or
atoms, resulting in the formation of nanoscale particles.
 The growth mechanism can be controlled by adjusting the reaction parameters,
such as temperature, precursor concentration, and reaction time.
Step 5:- Cooling and Stabilization:
 Once the desired nanomaterial has formed, the reaction is cooled down to room
temperature to halt further growth or aggregation.
 Rapid cooling or quenching can help preserve the size and morphology of the
nanomaterials.
In some cases, surface passivation or coating with a protective layer may be necessary

41. Hydrothermal Synthesis Method
Hydrothermal synthesis is a widely used method for the synthesis of
nanomaterials under high-pressure and high-temperature conditions in an
aqueous environment.
It involves the reaction of precursor compounds in a closed system,
typically a hydrothermal autoclave.
The hydrothermal method allows for the controlled growth and formation
of various nanomaterials with specific sizes, shapes, and properties.

42. Step 1:- Selection of Precursor:
 Choose suitable precursor compounds that can
react under hydrothermal conditions to form
the desired nanomaterial.
 These precursors can be metal salts, metal
oxides, or other compounds that are soluble or
can undergo hydrolysis in water.
Step 2:- Precursor Dissolution:
 Dissolve the selected precursors in a suitable
solvent, typically water, to prepare a precursor
solution.
 The concentration of the precursor can vary
depending on the desired nanomaterial
properties.
Step 3:-Reaction Vessel Preparation:
 Transfer the precursor solution to a
hydrothermal autoclave, which is a sealed
container capable of withstanding high
pressure and temperature.
 The autoclave is typically made of materials
such as stainless steel or Teflon to ensure

43. Step 4;- Sealing and Heating:
Sealing of hydrothermal autoclave and then heating from 100 to 300°C.
The reaction temperature and duration are crucial for controlling the growth and
formation of nanomaterials.
Step 5:- Reaction and Nucleation:
As the hydrothermal reaction progresses, the precursors undergo hydrolysis,
nucleation, and subsequent growth of nanomaterials.
The high-pressure and high-temperature conditions favour the formation of
homogeneous nucleation sites and controlled growth of nanocrystals or
nanoparticles.
Step 6:- Cooling and Isolation
•After the desired reaction time, autoclave is cooled to room temperature.
•The cooling rate can influence the final size and morphology of nanomaterials.
•Cooling followed by filtration or centrifugation and washing with a suitable
solvent

44. Conducting polymers:
Conducting polymers represent a group of specialty polymers which are electrically
conductive or can be made conductive by doping with an electron donor or acceptor.
They have an extended p- orbital system through which electrons can move from one end
of the polymer to the other. The most common examples are Polyacetylene, Polyaniline etc.
There are following type of conducting polymers
1. Intrinsically conducting polymers (ICP)
2. Doped conducting polymers (DCP)
3. Extrinsically conducting polymers (ECP)
4. Co-ordination conducting polymers (CCP)
Applications of Conducting Polymers
1) Rechargeable batteries
2) Antistatic coatings
3) Solar cells
4) Photovoltaic cells
5) Sensors
6) Transistors
7) Optical fibres.