Information About NEw Engineering MAterials

1. NEW ENGINEERING MATERIALS

2. Metallic Glasses
• It is the newly developed engineering materials. It share the
properties of both metals and alloys.
• Most metals and alloys are crystalline. In contrast, a glass is an
amorphous (non crystalline) brittle and transparent solid.
• Thus, metallic glasses are the metal alloys that are amorphous.
That is, they do not have a long range atomic order.
• Advantages:
1. homogeneous composition
2. strong and
3. superior corrosion resistance.

3. • To have this particular property, the metallic glasses are to be made
by cooling a molten metal so rapidly at a rate of 2 x 106°Cs-1. during
this process of solidification, the atoms do not have enough time or
energy to rearrange for crystal nucleation. Thus, the liquid upon
reaching the glass transition temperature Tg solidifies as a metallic
glass. Again, upon heating metallic glasses show a reversible glass-liquid
transition at Tg.

4. Types of Metallic Glasses
• Metallic glasses are of two types based on their base
material used for the preparation.
1. Metal-metal glasses, Exam Ni-Nb, Mg-Zn and Cu- Zr
2. Metal- Metalloid glasses. Transition metal like Fe, Co,
Ni and metalloid like B, Si, C and P are used.

5. Preparation
• Various rapid cooling techniques such as
• 1) spraying,
• 2) spinning and
• 3) laser deposition

6. • In this technique, there is spinning disc made of copper. In order to
prepare a metallic glass of a particular type a suitable combination of
metal-metal or metal-metalloid alloy in their stoichiometric ratio are
taken in a refractory tube having a fine nozzle at its bottom. The
nozzle side of the tube is placed just over the spinning disc.
• An induction heater attached to the refractory tube melts the alloy.
This melt is kept above its melting point till it gets transformed into a
homogeneous mixture. An inert gas such as helium is made to flow
through the tube containing the homogeneous mixture. As a results,
the melt gets ejected through the nozzle. The ejected melt is cooled at
a faster rate with the help of spinning cooled copper disc. The ejection
rate can be increased by increasing the pressure of the inert gas.
Thus, a glassy alloy ribbon starts getting formed over the spinning
disc.
• The thickness of the glassy ribbon may be varied by increasing or
decreasing the speed of the spinning disc.

7. The other techniques
• The other techniques used for producing ribbons of metallic
glasses include.
1. Twin roller system
In this technique a molten alloy is passed though two rollers
rotating in opposite directions.
2. Melt extraction system
In this technique the fast moving roller sweeps off
molten droplet into a strip from a solid rod.

8. Properties
• The strength of metallic glasses are very high (nearly twice that of
stainless steel) lighter in weight.
• They are ductile, malleable, brittle and opaque. The hardness is
very high.
• The toughness is very high, i.e., the fracture resistance is very high
(more than ceramics).
• They have high elasticity. i.e., the yield strength is very high.
• They have high corrosion resistance.
• They do not contain any crystalline defects like point defects,
dislocation, stacking faults etc.
• They are soft magnetic materials. As a result, easy magnetization
and demagnetization is possible.

9. • Magnetically soft metallic glasses have very narrow hysteresis loop
as shown in figure. Thus, they have very low hysteresis energy
losses.
• They have high electrical resistivity which leads to a low eddy
current loss.

10. Applications
1. Metallic glasses are used as transformer core material in high
power transformers.
2. Because of their high electrical resistivity and nearly zero
temperature coefficient of resistance, these materials are used in
making cryothermometers, magnetoresistance sensors and
computer memories.
3. As the magnetic properties of the metallic glasses are not affected
by radiation they are used in making containers for nuclear waste
disposal.
4. These materials are used in the preparation of magnets for fusion
reactors and magnets for levitated trains etc.

11. 5. Metallic glasses can also be used for making watch cases to
replace Ni and other metals which can cause allergic reactions.
6 The excellent corrosion resistance property makes these materials
to be ideal for cutting and in making surgical instruments. They can
be used as a prosthetic material for implantation in the human
body.
7 In future, the usage of metallic glasses in the electronic field can
yield, stronger, lighter and more easily moulded castings for
personal electronics products.
8 Metallic glasses are used in tap recorder as heads, in
manufacturing of springs and standard resistances.

12. Shape memory alloys
• Shape memory alloys (SMA’s) are metals which exhibit two very
unique properties,
1 shape memory effect and
2 pseudo elasticity or super elasticity (SE).
• These alloys are a unique class of materials, which remember their
shape even after severe deformation. i.e., when a SMA is ones
deformed in the cold shape (martensite) these materials will stay
deformed until heated; where, upon heating they will spontaneously
return to their original pre-determined hot shape (austenite).
• It is observed that, the structural changes at the atomic level
contributes to this unique properties of the materials.

13. Types of shape memory alloys
There are two types of Shape memory alloys (SMA’s)
1. The one way shape memory alloy
2. The two way shape memory alloy
• The materials which exhibit shape memory effect (i.e., taking their
own shape) only upon heating are said to have one way shape
memory.
• In contrast, some of the materials exhibit shape memory effect both
during heating and cooling. Hence, these materials are said to have
two shape memory

14. Crystal structure of shape memory alloy
• The shape memory alloys are said to have two distinct crystal
structure or phases. The effect of temperature and internal stresses
determines the crystal structure or the phase that the SMA will have
at particular instant.
• The phase which exists at high temperature is called the austenite
phase (microscopically they possess small platelets structure).
highly symmetric structure such as the one in cubic system
• The other phase which is found to exists at low temperature is called
the martensite phase (microscopically they possess needle like
structure). Less Symmetric like monoclinic.

15. Classification of shape memory
alloys
• The shape memory materials could be broadly
classified into three types
1. Temperature induced shape memory
2. Stress induced shape memory
3.Ferro-magnetic shape memory materials.

16. Temperature Induced Transformation
• The phase transformation takes place in SMA’s not at a particular
temperature but over a range of temperature. This transformation is
called the temperature transformation.

17. • The temperature induced transformation is characterized by four
temperatures, Ms and Mf during cooling and As and Af during heating.
• Ms And Mf indicate the temperature at which the transformation from
the parent phase austenite into martensite starts and finishes
respectively.
• Similarly As and Af indicate the temperature at which the reverse
transformation from martensite to austenite starts and finishes upon
heating.
• Thus, it is observed that, the overall transformation has a
temperature range of 10-15°C depending on the chemical
composition of the alloy. This overall transformation is found to
exhibit hysteresis in which, the transformations on heating and
cooling do not overlap. This hysteresis H is found to depend on the
composition of the alloy system.

18. Stress Induced Transformation
• The stress induced transformation takes place at a constant
temperature. At a temperature above the Af temperature, the
martensite phase can be induced by applying stress over the
austenite phase.

19. • When stressed above a certain value the austenite
phase undergoes a large elastic deformation. Stressing
beyond the elastic limit will result in permanent plastic
strains. On the removal of the stress, the material almost
completely recovers to the parent austenite phase at a
much lower value of stress.

20. Functional Properties
• The SMA’s are characterized by two important properties.
1. Shape Memory Effect (SME)
2. Super Elasticity (pseudoelasticity).
1. Shape memory effect
The SME is the phenomena in which a specimen apparently
deformed at lower temperature reverts to its undeformed original
shape when heated to higher temperature.
This SME is a consequence of a crystallographically reversible
martensitic phase transformation occurring in the solid state.
Schematically, the crystallographic formation of martensite and
reversion to austenite on heating.

22. • From the figure it is seen that, the high temperature austenitic
structure undergoes twinning as the temperature is lowered, this
twinned structure having microscopically needle like structure is
called martensite. This phase is relatively soft and easily deformed
phase of SMA which exists at lower temperatures.
• This phase upon deformation (i.e., on applying external stress)
takes on a particular shape called the deformed (detwinned)
martensite, and in the process undergoes a large elastic strain. If
heated in this condition, the deformed martensite returns to the
stable austenite structure and in the process recovers the elastic
strain. Thus, the shape memory phenomenon is seen.
• This SME is being implemented in making coffee pots,
• thermostats,
• vascular stents
• hydraulic fitting for air planes.

23. 2. Super elasticity (Pseudoelasticity)
Super elasticity (Pseudoelasticity) refers to the ability of SMA
to return to its original shape upon unloading after a substantial
deformation. This SE based on stress induced martensitic (SIM)
transformation. This SE in SMA’s occurs at a constant temperature
when the alloy is completely compose of austenite phase
(temperature is grater than Af).
The stress on the SMA is increased until the austenite phase
becomes transformed in to a martensite phase simply due to
loading. But, as soon as the loading is decreased the martensite
begins to transform back to austenite since, the temperature is still
above Af. As a result, it comes back to its original shape.
This effect, which causes the material to be extremely elastic is
known as pseudoelasticity or superelasticity. This SE is non linear it
is temperature and strain dependent. This SE is a mechanical type
of behavior of SMA’s.

25. • At a temperature above Af, the austenite phase is found to have
much higher yield and flow stresses. But, the martensite is easily
deformed to several percent strain at quite a low stress.
• This martensite phase is found to come back to the austenite phase
upon heating after removing the stress as shown by the dashed line.
But, no such shape recovery is found in the austenite phase upon
staining and heating, because no phase change occurs. The above
two behaviors are called as thermo mechanical behaviors.
• The superelasticity behaviour is applied in making
1. eye glass frames,
2. medical tools,
3. cellular phone antennae’s and
4. orthodontic arches.

26. Applications of shape memory alloys
1. Aircraft and space industry
fine-tuned helicopter blades
in antenna opening
hubble telescope and
in triggering devices.
2. Automobile industry
making spring acuators,
clutch systems,
thermostats,
oil pressure control unit
and high pressure sealing plugs.

27. 3. Medical field
1. as dental arch wires. These wires will make the misaligned teeth
gradually to return to their original shape exerting a small and
nearly constant force on the misaligned teeth.
2. They are also used as blood clot filter.
3. Nitinol needle wire localizers are used to locate and mark breast
tumours so that subsequent surgery can be more exact and less
invasive.
4. tweezers to remove foreign objects through small incisions.
5. guide wires for catheters through blood vessels.
6. in designing micro surgical instruments and
7. micro grippers etc.

28. 4. Consumer products
• SMA’s are used in making eye glass frames which offers improved
comfort and flexibility and in cellular phone antenna.
• Nitinol is used in robotic actuators and micro manipulators to
simulate human muscle motion.
• Ni-Ti springs in coffee pots.
• toys and ornamental goods.
• couplers and fasteners.
• fixed safely valves
• instantly restrict water flow in shower or sinks.
• safely valves that provide emergency shutdown of process control
lines that handle flammable and toxic fluid and gases.

29. • Advantages of SMA’s
biocompatibility,
diverse fields of application and
good mechanical properties.
• Disadvantages of SMA’s
highly expensive to manufacture and machine it.

30. Biomaterials
• The biomaterials are defined as “the materials with novel
chemical, physical, mechanical or “intelligent” properties
produced through processes that mimic biological
phenomena.”

31. Biomedical Compatibility of Ti-Al-Nb
Alloys for Implant Applications
• Over the last 30 years, biocompatible Ti alloy have been made use
of to replace human bones and teeth as these alloys are strong,
lightweight and biocompatible.
• The material of choice used in implant is titanium-vanadium-aluminium
(Ti-V-Al) alloys because of their
• excellent biocompatibility and
• high specific strength,
• corrosion resistance,
• low density,
• good ductility and elastic modulus.

32. BIOMATERIALS

33. Definition
• ‘Materials with novel chemical,
mechanical, physical or intelligent
properties that mimic biological
phenomena.’
• ‘Any substance (other than drugs) or
combination of substances synthetic or
natural in origin which can be used for any
period of time, as a whole or as a part of a
system, which treats, augments, or
replaces any tissue organ or function of
the body.’

34. Need for Biomaterials
• The need for biomaterials stems from an
inability to treat many diseases, injuries
and conditions with other therapies or
procedures
– replacement of body part that has lost
function (total hip, heart)
– correct abnormalities (spinal rod)
– improve function (pacemaker, stent)
– assist in healing (structural, pharmaceutical
effects: sutures, drug release)

35. History
• Historically, biomaterials consisted of
materials common in the laboratories of
physicians, with little consideration of
material properties.
• Early biomaterials :
– Gold: Malleable, inert metal; used in dentistry
by Chinese, Aztecs and Romans--dates 2000
years
– Iron, brass: High strength metals; rejoin
fractured femur (1775)
– Glass: Hard ceramic; used to replace eye
(purely cosmetic)

36. – Wood: Natural composite; high strength to
weight; used for limb prostheses and artificial
teeth
– Bone: Natural composite; uses: needles,
decorative piercings
– Sausage casing: cellulose membrane used
for early dialysis (W Kolff)
– Other: Ant pincers. Central American Indians
used to suture wounds

37. Essential factors
• Biofunctionality :
– The functions of these
materials mainly concern :
• Load transmission
• Stress distribution
(bone replacements)
• Light transmission
(implanted lenses)
• Sound transmission
(cochlear implant)
• Control of blood flow
(heart related implants)
– Based on these the
following need to be
considered while
seleting a biomaterial :
• Cost effectiveness
• Production rate
• Mechanical properties
(strength, toughness,
fatigue etc.)
• Physicochemical
properties (corrosion,
durability, electric and
thermal conductivity)

38. • Biocompatibility :
– A material is said to be
biocompatible if it does
not undergo a
degradation in its
properties within the
environment of the body
and does not cause
adverse reactions
– Possible outcomes if this
factor is overlooked are :
• Corrosion
• Swelling
• Leaching
• Dissolution
• Wear
• Modification of
chemical properties
etc.

39. Classification
Biomaterials
Naturally-derived Semi-synthetic Synthetic
Metals and Alloys
Polymers
Ceramics
Composites

40. Natural biomaterials
• These materials are derived
from living things itself i.e.
from plants and animals,
for example – collagen,
keratin, cellulose, chitin
• They offer several
advantages like preventing
risk of toxicity, which is the
problem arising in case of
synthetic implants.

41. Synthetic biomaterials
• Metal and alloy
biomaterials (biometal)
– Used due to mechanical
strength and toughness
– Used for load bearing
implants
– Include simple wires,
screws, plates, total joint,
prostheses
– Common ones :
• stainless steel, cobalt
alloys, titanium alloys

44. – Applications :
• Bone plates,
stents, orthodontic
wires
(Ni-Ti)
• Bone and joint
replacement
(Co-Cr-Mo)
• Heart valves,
Dental implants
(Cr-Ni-Cr-Mo)
Artificial
knee
joints
Artificial wrist
joint

45. Bone plates, to
assist in the
healing of
skeletal fractures,
• Fracture fixation, stents
(stainless steel)
• Antibacterial agents
(silver products)
• Dental restoration
(gold alloys and Hg-Ag-
Sn amalgam)

46. • Polymers :
– these have properties most similar to natural
tissues.
– Their properties depend on their composition,
structure and arrangement of constituent
molecules
– examples :
silicones, polyethylene, polyvinyl chloride,
polyurethanes, polylactides

47. – Over a period of time these degrade, which
could be :
• Controlled degradation
– Here material is designed to serve this process
– They get broken down into smaller fragments and are
later eliminated from the body by normal metabolic
processes of the body
• Unintentional degradation
– Occur due to reactions like oxidation or hydrolysis
– Release chemicals that trigger host immune reactions, of
severe nature

48. – Applications :
• Joint lining
• Wound
dressing
• Intraocular lens
replacement
• Tendon
replacement

50. • Ceramics (bioceramics):
– Out of the wide range of ceramics available,
only a few are biocompatible
– These can be :
bioinert, bioactive, biodegradable
– These materials have :
1. Great stiffness
2. high resistance to corrosion
3. excellent wear resistance
4. low density

51. A titanium hip prosthesis, with a ceramic head and
polyethylene acetabular cup

52. – Applications:
1. dental, and bone implants
Artificial teeth, and bones
are relatively commonplace
2. Surgical cements are used
regularly
3. Joint replacements are
commonly coated with
bioceramic materials to
reduce wear and
inflammatory response.
Other examples are in
pacemakers, kidney dialysis
machines, and respirators.

53. • Composites :
– ‘Composite materials are solids which contain two or
more distinct constituent materials or phases, on a scale
larger than the atomic. The term “composite” is usually
reserved for those materials in which the distinct phases
are separated on a scale larger than the atomic
– For example –
• reinforced plastics such as fiberglass
• natural materials such as bone , wood, dentin
• A foam is a composite in which one phase is empty
space.
– Natural biological materials tend to be composites.
Natural foams include lung, cancellous bone, cartilage,
skin and wood
– Natural composites often exhibit particulate, porous,
and fibrous structural features

54. – Properties :
1. Low density
2. High strength
(Properties such as the elastic modulus are significantly
altered in comparison with those of a homogeneous
material.)
– Applications :
• Dentistry – dental filling composites(dental cement),
restorative material
• Prosthetic limb
• bone cement
• orthopedic implants with porous surfaces

55. synthetic cellular solids
(a) open-cell polyurethane,(b) closed-cell
polyethylene, (c) foamed nickel, (d) foamed
copper, (e) foamed zirconia, (f) foamed
mullite, (g) foamed glass, (h) polyester foam
with both open and closed cells.
natural cellular solids:
(a) cork, (b) balsa wood, (c) sponge, (d)
cancellous bone, (e) coral, (f) cuttlefish
bone, (g) iris leaf, (h) plant stalk.

56. PHOTO CONDUCTIVITY
hc
E
1.24
( )
c
g
c
g
m
E eV
l =
l = m

57. Photo voltaic cell
Popularly known
as Solar cell

58. Solar cell
working

63. Parameters
1.Open Circuit Voltage
2.Short Circuit Current
3.Fill Factor
4.Conversion Efficiency

64. Isc
The short-circuit current is the
current through the solar cell
when the voltage across the
solar cell is zero (i.e., when the
solar cell is short circuited).
The short-circuit current is
the largest current which
may be drawn from the solar
cell.
I
Vm
Im
Pm
Voc
X
I = I ( e qV /
kT - 1)
- I
total 0 L At V=0  Itotal = -IL= Isc
V

65. The open-circuit voltage
corresponds to the amount of
forward bias on the solar cell
junction due to illumination.
V kT I
= +
ln( L 1)
q I
65
Voc
The open-circuit voltage, Voc, is
the maximum voltage available
from a solar cell, and this occurs
at zero current.
Isc
I
Vm
Im
Pm
X
Voc
I = I ( e qV /
kT - 1)
- I
total 0 L oc
by setting Itotal = 0 0

66. Pm
Isc
I
Vm
Im
Pm
X
Voc
Power
Power out of a solar cell
increases with voltage,
reaches a maximum (Pm)
and then decreases again.
Pm = Im x Vm
Remember we get DC power from a solar cell

67. FF
Isc
I
Ideal diode curve
Vm
Im
Voc
Pm
The FF is defined as the ratio
of the maximum power from
the actual solar cell to the
maximum power from a
ideal solar cell
Graphically, the FF is a
measure of the "squareness"
of the solar cell
FF Max power from real cell V I
m m
oc sc
= =
Max power from ideal cell V I

68. η
Efficiency is defined as the ratio
of energy output from the solar
cell to input energy from the sun.
Max Cell Power V I
Incident light Intensity P
. m m
in
h = =
Isc
I
Pm
X
Vm
Im
Voc
Power
V I FF
oc sc
P
in
h =
The efficiency is the most commonly used parameter to compare the
performance of one solar cell to another.
Efficiency of a cell also depends on the solar spectrum, intensity of
sunlight and the temperature of the solar cell.

69. Isc
I
Im
Power
10/22/14 © IIT
Bombay, C.S. Solanki
Efficiency is defined as the ratio of energy
output from the solar cell to input energy from
the sun.
Max Cell Power V I
Incident light Intensity P
h =
Solar Photovoltaic
Technologies
69
Efficiency: η
. m m
in
h = =
Pm
X
Vm
Voc
V I FF
oc sc
P
in
The efficiency is the most commonly used parameter to compare the
performance of one solar cell to another.
Efficiency of a cell also depends on the solar spectrum, intensity of sunlight
and the temperature of the solar cell.

70. Applications

74. Fuel cell
A fuel cell is a device that
converts the chemical energy
from a fuel into electricity through
a chemical reaction with oxygen
or another oxidizing agent
Hydrogen is the most common fuel, but
hydrocarbons such as natural gas and
alcohols like methanol are sometimes
used. Fuel cells are different from
batteries in that they require a constant
source of fuel and oxygen/air to sustain
the chemical reaction; however, fuel
cells can produce electricity continually
for as long as these inputs are
supplied.

76. The most important design features in
a fuel cell are :
The electrolyte substance. The electrolyte substance
usually defines the type of fuel cell.
The fuel that is used. The most common fuel is hydrogen.
The anode catalyst breaks down the fuel into electrons and
ions. The anode catalyst is usually made up of very fine
platinum powder.
The cathode catalyst turns the ions into the waste
chemicals like water or carbon dioxide. The cathode catalyst
is often made up of nickel but it can also be a nanomaterial-based
catalyst.

77. A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load.
Voltage decreases as current increases, due to several factors:
Activation loss
Ohmic loss (voltage drop due to resistance of the cell components and
interconnections)
Mass transport loss (depletion of reactants at catalyst sites under high loads,
causing rapid loss of voltage).