HIGH PERFORMANCE MATERIALS - PowerPoint PPT Presentation

Loading...

PPT – HIGH PERFORMANCE MATERIALS PowerPoint presentation | free to download - id: 6e78f4-MGUyN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

HIGH PERFORMANCE MATERIALS

Description:

The melt flows through the annular gap and solidifies at the exit in a cold water bath. ... Techniques The Chemicals Modified Chemical Vapour Deposition (MCVD) ... – PowerPoint PPT presentation

Number of Views:47
Avg rating:3.0/5.0
Slides: 68
Provided by: RAMACHANDRAN
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: HIGH PERFORMANCE MATERIALS


1
HIGH PERFORMANCE MATERIALS
Developments
1926- 1990 Synthetic rubber. Polyvinyl
chloride (PVC). New molding and extrusion
techniques for plastics. Polystyrene.
Polyethelene. continuous casting of steel,
Plexiglass. Nylon in 1938. Teflon discovered by
Roy Plunkett. Fiberglass. Foam glass insulating
material. Plastic contact lens. Vinyl floor
covering. Aluminum-based metallic yard. Ceramic
magnets. Basic oxygen process to refine steel
making. Karl Zeigler invents new process for
producing polyethelene. Dacron, plasticized PVC,
and silicones manufactured by Dow Corning.
Polypropylene (petroleum-based). Superpolymers
(heat resistant). 1964 - Acrylic paint . Carbon
fiber (used to reinforce materials in high
temperature environment). Beryllium (hard metal)
developed for heat shields in spacecraft, animal
surgery, aircraft parts, etc. Sialon (ceramic
material for high-speed cutting tools in metal
machining). Soft bifocal contact lens in 1983.
Synthetic skin.
New composites and lightweight steel
2
  • SMART MATERIALS- which adjust to the requirements
  • "smart materials" also called intelligent
    materials or active materials describes a group
    of material systems with unique properties.
  • The technological field of smart materials is
    not transparent or clearly structured. It has
    evolved over the past decades with increasing
    pace during the 1990s to become what it is today.
  • Smart materials, Intelligent Materials, Active
    Materials, Adaptive Materials and to some extent
    actuators and sensors are almost always used
    interchangeably.
  • Active materials - two groups.
  • 1. The classical active materials as
    viewed by the academic community and is
    characterized by the type of response these
    materials generate.
  • 2. Consists of materials that respond to
    stimuli with a change in a key material property,
    eg.electrical conductivity or viscosity
  • Mention of medicines, packed items which will
    indicate the life with change in time,
    environment, decay etc dress materials which
    will adjust with the human conditions etc. etc.

3
  • Self diagnostic materials
  • Optic fibres composite Smart
    composites Smart tagged composites
  • Temperature changing materials
  • Thermoelectric materials
  • Thickness changing fluids
  • Magneto-Rehological fluids (MRFs)
  • References
  • Intelligent Materials Smart materials workshop

4
Smart Materials
Colour changing materials Light emitting Materials Moving materials Photochromic materials Thermochromic materials Electroluminescent materials Fluorescent materials Phosphorescent materials Conducting polymers Dielectric elastomers Piezoelectric materials Polymer gels Shape memory alloys (SMA)
A smart material with variable viscosity may turn
from a fluid which flows easily to a solid. A
smart fluid developed in labs at the Michigan
Institute of Technology
5
Smart Materials
Also termed as Responsive Materials
  • "Smart" materials respond to environmental
    stimuli with particular changes in some
    variables. Also called responsive materials.
    Depending on changes in some external
    conditions, "smart" materials change either their
    properties (mechanical, electrical, appearance),
    their structure or composition, or their
    functions. Mostly, "smart" materials are
    embedded in systems whose inherent properties can
    be favorably changed to meet performance needs.

6
  • Self diagnostic materials
  • Optic fibres composite Smart
    composites Smart tagged composites
  • Temperature changing materials
  • Thermoelectric materials
  • Thickness changing fluids
  • Magneto-Rehological fluids (MRFs)
  • References
  • Intelligent Materials Smart materials workshop

7
Shape Memory Alloys (SMA)
  • Shape memory alloys (SMA's) are metals, which
    exhibit two very unique properties,
    pseudo-elasticity, and the shape memory effect.
    Arne Olander first observed these unusual
    properties in 1938 (Oksuta and Wayman 1938), but
    not until the 1960's were any serious research
    advances made in the field of shape memory
    alloys. The most effective and widely used alloys
    include NiTi (Nickel - Titanium), CuZnAl, and
    CuAlNi

8
Shape Memory Alloys (SMA)
  • Shape memory alloys (SMA's) are metals, which
    exhibit two very unique properties,
    pseudo-elasticity, and the shape memory effect.
  • The most effective and widely used alloys include
    NiTi (Nickel - Titanium), CuZnAl, and CuAlNi

9
Applications of Shape Memory Alloys
  • Aeronautical Applications
  • Surgical Tools
  • Muscle Wires

10
SHAPE MEMORY EFFECT
  • Implemented in
  • Coffee pots
  • The space shuttle
  • Thermostats
  • Vascular Stets
  • Hydraulic Fittings (for Airplanes)

11
SHAPE MEMORY EFFECT
  • Implemented in
  • Coffee pots
  • The space shuttle
  • Thermostats
  • Vascular Stets
  • Hydraulic Fittings (for Airplanes)

12
Microscopic and Macroscopic Views of the Two
Phases of Shape Memory Alloys
13
Microscopic Diagram of the Shape Memory Effect
14
How Shape Memory Alloys Work
The Martensite and Austenite phases
15
Applications of Shape Memory Alloys
  • Aeronautical Applications
  • Surgical Tools
  • Muscle Wires

16
(No Transcript)
17
The Dependency of Phase Change Temperature on
Loading
18
Pseudo-elasticity
Applications in which pseudo-elasticity is used
are Eyeglass Frames Under garments Medical
Tools Cellular Phone Antennae Orthodontic
Arches
Load Diagram of the pseudo-elastic effect
Occurring
19
Advantages and Disadvantages of SMAs
  • Bio-compatibility
  • Diverse Fields of Application
  • Good Mechanical Properties (strong, corrosion
    resistant)

Relatively expensive to manufacture and machine.
Most SMA's have poor fatigue properties this
means that while under the same loading
conditions (i.e. twisting, bending, compressing)
a steel component may survive for more than one
hundred times more cycles than an SMA element
20
Ferromagnetic Shape Memory Alloys (FSMA)
  • Ferromagnetic Shape Memory Alloys (FSMA) Recently
    discovered class of actuator material,
    Magnetically driven actuation (field intensity
    varies, about 3KG and larger) and
  • large strains (around 6).
  • FSMA are still in the development phase
  • Alloys in the Ni-Mn-Ga ternary.
  • FSMAs are ferromagnetic alloys which also support
    the shape memory effect.

21
OPTICAL FIBRE
  • Made of extremely pure silica.
  • Thinner than a human hair and stronger than a
    steel fibre of similar thickness. It can carry
    thousands of times more information than a copper
    wire!
  • Optical fibre cables have the advantage of being
    lighter and taking less space than copper wire
    cables for the same information capacity.

22
Fabrication of Optical Fibres
  • The best cakes are made of the best ingredients.
  • To make a good optical fibre, we need to start
    with good quality materials, that is highly
    purified materials.
  • The presence of impurities alter the optical
    properties of the fibre.
  • There are several ways to manufacture optical
    fibres
  • Directly drawing the fibre from what is called a
    preform.
  • The fibre is then drawn from the preform
  • i) Direct Techniques
  • Two methods can be used to draw a fibre directly
  • Double Crucible method
  • Rod in Tube method

23
1. Double Crucible
The molten core glass is placed in the inner
crucible. The molten cladding glass is placed in
the outer crucible. The two glasses come
together at the base of the outer cucible and a
fibre is drawn. Long fibres can be produced
(providing you don't let the content of the
crucibles run dry!). Step-index fibres and
graded-index fibres can be drawn with this
method.
24
2. Rod in Tube
A rod of core glass is placed inside a tube of
cladding glass. The end of this assembly is
heated both are softened and a fibre is drawn.
Rod and tube are usually 1 m long. The core rod
has typically a 30 mm diameter. The core glass
and the cladding glass must have similar
softening temperatures. This method is
relatively easy just need to purchase the rod
and the tube. However, must be very careful not
to introduce impurities between the core and the
cladding.
25
ii) Deposition Techniques
  • Most optical fibres are made from preforms. The
    preforms are made by deposition of silica and
    various dopants from mixing certain chemicals
    the fibre is then drawn from the preform.
  • Many techniques are used to make preforms. Among
    them
  • Modified Chemical Vapour Deposition or MCVD
  • Plasma-Enhanced Modified Chemical Vapour
    Deposition or PMCVD
  • Outside Vapour Deposition or OVD
  • Axial Vapour Deposition or AVD

26
The Chemicals
  • Oxygen (O2) and silicon tetrachloride (SiCl4)
    react to make silica (SiO2).
  • Pure silica is doped with other chemicals such as
    boron oxide (B2O3), germanium dioxide (GeO2) and
    phosphorus pentoxide (P2O5) are used to change
    the refractive index of the glass.

27
Modified Chemical Vapour Deposition (MCVD)
28
  • The chemicals are mixed inside a glass tube that
    is rotating on a lathe.
  • They react and extremely fine particles of
    germano or phosphoro silicate glass are deposited
    on the inside of the tube.
  • A travelling burner moving along the tube
  • causes a reaction to take place and then
    fuses the deposited material.
  • The preform is deposited layer by layer starting
    first with the cladding layers and followed by
    the core layers.
  • Varying the mixture of chemicals changes the
    refractive index of the glass.
  • When the deposition is complete, the tube is
    collapsed at 2000 C into a preform of the purest
    silica with a core of different composition.
  • The preform is then put into a furnace for
    drawing.

29
Plasma-Enhanced Modified Chemical Vapour
Deposition (PMCVD)
Plasma-Enhanced Modified Chemical Vapour
Deposition is similar in principle to MCVD. The
difference lies in the use of a plasma instead of
a torch. The plasma is a region of electrically
heated ionised gases. It provides sufficient heat
to increase the chemical reaction rates inside
the tube and the deposition rate. This technique
can be used to manufacture very long fibres (50
km). It is used for both step index and graded
index fibres.
30
Outside Vapour Deposition (OVD)
The chemical vapours are oxidised in a flame in a
process called hydrolysis. The deposition is
done on the outside of a silica rod as the torch
moves laterally. When the deposition is complete,
the rod is removed and the resulting tube is
thermally collapsed
31
Axial Vapour Deposition (AVD)
The deposition occurs on the end of a rotating
silica boule as chemical vapors react to form
silica. Core preforms and very long fibres can
be made with this technique. Step-index fibres
and graded-index fibres can be manufactured this
w
32
From Preform to Fibre
  • All these deposition techniques produce preforms.
    These are typically 1 m long and have a 2 cm
    diameter but these dimensions vary with the
    manufacturer.
  • The preform is one step away from the thin
    optical fibre. This step involves a process
    called drawing.

33
Fibre Drawing and Spooling
  • During this last step of the fabrication process,
    many things will happen to the fibre
  • the fibre is drawn from the preform.
  • it is quality checked
  • it is coated for protection
  • it is stored on a spool (just like a
    photographic film).

34
  • The tip of the preform is heated to about 2000C
    in a furnace. As the glass softens, a thin
    strand of softened glass falls by gravity and
    cools down.
  • As the fibre is drawn its diameter is constantly
    monitored
  • A plastic coating is then applied to the fibre,
    before it touches any components. The coating
    protects the fibre from dust and moisture.
  • The fibre is then wrapped around a spool.

35
Fabrication of an Optical Fibre
Heating the preform
Drawing the fibre
36
Piezoelectric Materials
1. When a piezoelectric material is deformed, it
gives off a small but measurable electrical
discharge
2. When an electrical current is passed through a
piezoelectric material it experiences a
significant increase in size (up to a 4 change
in volume)
Most widely used as sensors in different
environments
To measure fluid compositions, fluid density,
fluid viscosity, or the force of an impact
Eg Airbag sensor in modern cars-
senses the force of an impact on the car and
sends and electric charge deploying the airbag.
37
Electro-Rheostatic (ER) and Magneto-Rheostatic
(MR) materials
These materials are fluids, which can experience
a dramatic change in their viscosity
Can change from a thick fluid (similar to motor
oil) to nearly a solid substance within the span
of a millisecond when exposed to a magnetic or
electric field the effect can be completely
reversed just as quickly when the field is
removed.
38
  • THERMOPLASTICS
  • THERMOSETTING PLASTICS
  • ELASTOMERS
  • printouts shall be supplied

39
  • ABOUT
  • METALLIC COATINGS
  • DIFFUSION COATINGS
  • ANODISING
  • POWDER COATING
  • THERMOPLASTICS
  • THERMOSETTING PLASTICS
  • ELASTOMERS printouts shall be supplied

40
  • Self diagnostic materials
  • Optic fibres composite Smart
    composites Smart tagged composites
  • Temperature changing materials
  • Thermoelectric materials
  • Thickness changing fluids
  • Magneto-Rehological fluids (MRFs)
  • References
  • Intelligent Materials Smart materials workshop

41
Ferromagnetic Shape Memory Alloys (FSMA)
  • Ferromagnetic Shape Memory Alloys (FSMA) Recently
    discovered class of actuator material,
    Magnetically driven actuation (field intensity
    varies, about 3KG and larger) and
  • large strains (around 6).
  • FSMA are still in the development phase
  • Alloys in the Ni-Mn-Ga ternary.
  • FSMAs are ferromagnetic alloys which also support
    the shape memory effect.

42
Advantages and Disadvantages of SMAs
  • Bio-compatibility
  • Diverse Fields of Application
  • Good Mechanical Properties (strong, corrosion
    resistant)

Relatively expensive to manufacture and machine.
Most SMA's have poor fatigue properties this
means that while under the same loading
conditions (i.e. twisting, bending, compressing)
a steel component may survive for more than one
hundred times more cycles than an SMA element
43
  • THERMOPLASTICS
  • THERMOSETTING PLASTICS
  • ELASTOMERS
  • printouts shall be supplied

44
CAST IRON
  • GRAY C.I.
  • DUCTILE C.I
  • WHITE C.I.
  • MALLEABLE IRON
  • COMPACTED GRAPHITE IRON
  • Also by stress levels as
  • ferritic, Pearlitic, Quenched and tempered,
    Austempered

45
Unit Operations in Polymer Processing
  • Thermoplastic and thermoset melt processes may be
    broken down into
  • Preshaping
  • Shaping
  • Shape Stabilization

46
Unit Operations in Polymer Processing
  • Preshaping steps
  • Solids handling and conveying most processes
    usually involve feed in particulate form
  • Plastication The creation of a polymer melt from
    a solid feed.
  • Mixing often required to achieve uniform melt
    temperature or uniform composition in compounds
  • Pumping The plasticated melt must be
    pressurized and pumped to a shaping device
  • Shaping
  • The polymer melt is forced through the shaping
    devices to create the desired shape.
  • The flow behavior (rheology) of polymer melts
    influences the design of the various shaping
    devices, the processing conditions and the rate
    at which the product can be shaped.
  • Shape stabilization
  • Involves the solidification of the polymer melt
    in the desired shape, through heat transfer

47
The Single Screw Plasticating Extruder
  • Regions 1, 2, 3 Handling of particulate solids
  • Region 3 Melting, pumping and mixing
  • Region 4 Pumping and mixing
  • Regions 34 Devolatilization (if needed)

48
Product Shaping / Secondary Operations
EXTRUSION
Final Product (pipe, profile)
  • Secondary operation
  • Fiber spinning (fibers)
  • Cast film (overhead transparencies,
  • Blown film (grocery bags)

Shaping through die
  • Preform for other molding processes
  • Blow molding (bottles),
  • Thermoforming (appliance liners)
  • Compression molding (seals)

49
Annular (Tubular) Dies
  • In a tubular die the polymer melt exits through
    an annulus. These dies are used to extrude
    plastic pipes. The melt flows through the annular
    gap and solidifies at the exit in a cold water
    bath.

50
Profile dies
  • Profiles are all extruded articles having
    cross-sectional shape that differs from that of a
    circle, an annulus, or a very wide and thin
    rectangle (such as flat film or sheet)
  • To produce profiles for windows, doors etc. we
    need appropriate shaped profile dies. The
    cross-section of a profile die may be very
    complicated

51
Secondary Shaping
  • Secondary shaping operations occur immediately
    after the extrusion profile emerges from the die.
    In general they consist of mechanical stretching
    or forming of a preformed cylinder, sheet, or
    membrane. Examples of common secondary shaping
    processes include
  • Fiber spinning
  • Film Production (cast and blown film)

52
Fiber Spinning
  • Fiber spinning is used to manufacture synthetic
    fibers. A filament is continuously extruded
    through an orifice and stretched to diameters of
    100 mm and smaller. The molten polymer is first
    extruded through a filter or screen pack, to
    eliminate small contaminants. It is then extruded
    through a spinneret, a die composed of multiple
    orifices (it can have 1-10,000 holes). The fibers
    are then drawn to their final diameter,
    solidified (in a water bath or by forced
    convection) and wound-up.

53
Fiber Spinning
  • Melt spinning technology can be applied to
    polyamide (Nylon), polyesters, polyurethanes and
    polyolefins such as PP and HDPE.
  • The drawing and cooling processes determine the
    morphology and mechanical properties of the final
    fiber. For example ultra high molecular weight
    HDPE fibers with high degrees of orientation in
    the axial direction have extremely high stiffness
    !!
  • Of major concern during fiber spinning are the
    instabilities that arise during drawing, such as
    brittle fracture and draw resonance. Draw
    resonance manifests itself as periodic
    fluctuations that result in diameter oscillation.

54
Cast Film Extrusion
  • In a cast film extrusion process, a thin film is
    extruded through a slit onto a chilled, highly
    polished turning roll, where it is quenched from
    one side. The speed of the roller controls the
    draw ratio and final film thickness. The film is
    then sent to a second roller for cooling on the
    other side. Finally it passes through a system of
    rollers and is wound onto a roll.
  • Thicker polymer sheets can be manufactured
    similarly. A sheet is distinguished from a film
    by its thickness by definition a sheet has a
    thickness exceeding 250 mm. Otherwise, it is
    called a film.

55
Sheeting Dies
  • One of the most widely used extrusion dies is
    the coat-hanger or sheeting die. It is used to
    extrude plastic sheets. It is formed by the
    following elements
  • Manifold evenly distributes the melt to the
    approach or land region
  • Approach or land carries the melt from the
    manifold to the die lips
  • Die lips perform the final shaping of the melt.
  • The sheet is subsequently pulled (and cooled
    simultaneously) by a system of rollers

56
Blown Film Extrusion
  • Film blowing is the most important method for
    producing Polyethylene films (about 90 of all PE
    film produced)
  • In film blowing a tubular cross-section is
    extruded through an annular die (usually a spiral
    die) and is drawn and inflated until the frost
    line is reached. The extruded tubular profile
    passes through one or two air rings to cool the
    material.
  • Most common materials LDPE, HDPE, LLDPE

57
Coextrusion
  • In coextrusion two or more extruders feed a
    single die, in which the polymer streams are
    layered together to form a composite extrudate.

58
Molding Processes
  • Molding techniques for polymers involve the
    formation of three-dimensional components within
    hollow molds (or cavities)
  • Injection Molding
  • Thermoforming
  • Compression Molding
  • Blow Molding
  • Rotational Molding

59
Injection Molding
  • Injection molding is the most important process
    used to manufacture plastic products. It is
    ideally suited to manufacture mass produced parts
    of complex shapes requiring precise dimensions.
  • It is used for numerous products, ranging from
    boat hulls and lawn chairs, to bottle cups. Car
    parts, TV and computer housings are injection
    molded.
  • The components of the injection molding machine
    are the plasticating unit, clamping unit and the
    mold.

60
Injection Molding Cycle
  • Injection molding involves two basic steps
  • Melt generation by a rotating screw
  • Forward movement of the screw to fill the mold
    with melt and to maintain the injected melt under
    high pressure
  • Injection molding is a cyclic process
  • Injection The polymer is injected into the mold
    cavity.
  • Hold on time Once the cavity is filled, a
    holding pressure is maintained to compensate for
    material shrinkage.
  • Cooling The molding cools and solidifies.
  • Screw-back At the same time, the screw retracts
    and turns, feeding the next shot in towards the
    front
  • Mold opening Once the part is sufficiently cool,
    the mold opens and the part is ejected
  • The mold closes and clamps in preparation for
    another cycle.

61
Injection Molding Cycle
  • The total cycle time is tcycletclosingtcooling
    tejection.

62
Thermoforming
  • Thermoforming is an important secondary shaping
    operation for plastic film and sheet. It consists
    of warming an extruded plastic sheet and forming
    it into a cavity or over a tool using vacuum, air
    pressure, and mechanical means. The plastic sheet
    is heated slightly above the glass transition
    temperature for amorphous polymers, or slightly
    below the melting point, for semi-crystalline
    polymers. It is then shaped into the cavity over
    the tool by vacuum and frequently by plug-assist.

63
Thermoforming
  • Thermoforming is used to manufacture refrigerator
    liners, shower stalls, bathtubs and various
    automotive parts.
  • Amorphous materials are preferred, because they
    have a wide rubbery temperature range above the
    glass transition temperature. At these
    temperatures, the polymer is easily shaped, but
    still has enough melt strength to hold the
    heated sheet without sagging. Temperatures about
    20-100C above Tg are used.
  • Most common materials are Polystyrene (PS),
    Acrylonitrile-Butadiene-Styrene (ABS), PVC, PMMA
    and Polycarbonate (PC)

64
Compression Molding
  • Compression molding is the most common technique
    for producing moldings from thermosetting
    plastics and elastomers.
  • Products range in size from small plastic
    electrical moldings and rubber seals weighing a
    few grams, up to vehicle body panels and tires.
  • A matched pair of metal dies is used to shape a
    polymer under the action of heat and pressure.

65
Blow Molding
  • Blow molding produces hollow articles that do
    not require a homogeneous thickness distribution.
    HDPE, LDPE, PE, PET and PVC are the most common
    materials used for blow molding. There are three
    important blow molding techniques
  • Extrusion blow molding
  • Injection blow molding
  • Stretch-blow processes
  • They involve the following stages
  • A tubular preform is produced via extrusion or
    injection molding
  • The temperature controlled perform is transferred
    into a cooled split-mould
  • The preform is sealed and inflated to take up the
    internal contours of the mould
  • The molding is allowed to cool and solidify to
    shape, whilst still under internal pressure
  • The pressure is vented, the mold opened and the
    molding ejected.

66
Extrusion Blow molding
  • In extrusion blow molding, a parison (or tubular
    profile) is extruded and inflated into a cavity
    with a specified geometry. The blown article is
    held inside the cavity until it is sufficiently
    cool.

67
Injection Blow Molding
  • Injection blow molding begins by injection
    molding the parison onto a core and into a mold
    with finished bottle threads. The formed parison
    has a thickness distribution that leads to
    reduced thickness variations throughout the
    container. Before blowing the parison into the
    cavity, it can be mechanically stretched to
    orient molecules axially (Stretch blow molding).
    The subsequent blowing operation introduces
    tangential orientation. A container with biaxial
    orientation exhibits higher optical clarity,
    better mechanical properties and lower
    permeability.
About PowerShow.com