Milind Arbatti

1
Nanocomposites

• By
• Milind Arbatti
• Instructor Dr. Tzeng
• 7970

2
Introduction

• What are Composite materials?
• Theory behind Composites
• Limitations of Composite materials
• Welcome to the world of nanocomposites!
• Theory behind nanocomposites
• Making of nanocomposites
• Properties of nanocomposites
• Applications
• Limitations
• Questions

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Definition of Composite Materials

• Multiphase material
• Usually exhibits properties of both phases
• Usually improves performance over either
  individual phase
• Composites have already been discussed
• Multiphase metal alloys, or ceramics or polymers
• Example, pearlitic steels, alt. layers a Fe3C
• There are also composites spanning materials
  classes (e.g. ceramic and metals)

mse.iastate.edu/mate271/lectures/
720-20Composites.ppt
4
Theory!

• Composites often have only two phases
• Matrix phase
• continuous - surrounds other phase
• Dispersed phase
• discontinuous phase

Matrix (light) Dispersed phase (dark)
mse.iastate.edu/mate271/lectures/
720-20Composites.ppt
5
Classification of Artificial Composites
Composites
Particulate
Fiber
Structural
Laminates
Sandwich
Large
Dispersion
Panels
Particle
Strengthened
Continuous
Discontinuous
Aligned
Random
mse.iastate.edu/mate271/lectures/
720-20Composites.ppt
6
Properties of Composites

• Dependent on
• constituent phases
• relative amounts
• geometry of dispersed phase
• shape of particles
• particle size
• particle distribution
• particle orientation

• For a given matrix/dispersed phase system
• Concentration
• Size
• Shape
• Distribution
• Orientation

mse.iastate.edu/mate271/lectures/
720-20Composites.ppt
7
Parameters
mse.iastate.edu/mate271/lectures/
720-20Composites.ppt
Concentration
Orientation
Distribution
Size
Shape
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Rule of Mixtures
Actual Values
Upper bound


E - particulate



E- matrix


Lower bound
conc. of particulates
http//www.eng.umass.edu/plastics/nano.ppt
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Fiber-Reinforced Composites

• Technologically, the most important type of
  composite.
• Characterized in terms of specific strength or
  specific modulus strength (or E) per weight
• usually want to maximize specific strength and
  modulus
• Subclasses
• Short fiber and continuous fiber lengths

• Fiber Phase
• Requirements for the fiber
• The small diameter fiber must be much stronger
  than the bulk material
• High tensile strength
• (Wiskers, Fibres, Wires)
• Matrix Phase
• Function
• Binds fibers together
• Acts as a medium through which externally applied
  stress is transmitted and distributed to the
  fibers
• Protects fiber from surface damage
• Separates fibers and prevents a crack from one
  fiber from propagating through another

http//www.eng.umass.edu/plastics/Composites.ppt
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Influence of Fiber Length

• Mechanical properties depend on
• mechanical properties of the fiber
• how much load the matrix can transmit to the
  fiber
• depends on the interfacial bond between the fiber
  and the matrix
• Critical fiber length - depends on
• fiber diameter, fiber tensile strength
• fiber/matrix bond strength

Critical fiber length - lc lc
sfd/2tc where d fiber diameter tc
fiber-matrix bond strength sf fiber yield
strength
mse.iastate.edu/mate271/lectures/
720-20Composites.ppt
11
Influence of Fiber Orientation

• Fiber parameters
• arrangement with respect to each other
• distribution
• concentration
• Fiber orientation
• parallel to each other
• totally random
• some combination

mse.iastate.edu/mate271/lectures/
720-20Composites.ppt
12
Limitations of Composites

• Properties of material are highly anisotropic due
  to orientation fibers
• Modulus in direction of alignment is a function
  of the volume fraction of the E of the fiber and
  matrix
• Modulus perpendicular to direction of alignment
  is considerably less (the fibers do not
  contribute)
• Loss of transparency
• Loss Optical/Electrical/Chemical (barrier)
  Properties

13
Welcome to the NanoWorld !!!

• A broad class of materials, with microstructures
  modulated in zero to three dimensions on length
  scales less than 100 nm.
• Materials with atoms arranged in nanosized
  clusters, which become the constituent grains or
  building blocks of the material
• Any material with at least one dimension in the
  1-100m range

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Classes of nanostructured materials

• Range, from zero dimensional atom clusters to
  three dimensional equiaxed grain structure.  Each
  class has at least one dimension in the nanometer
  range

zero modulation dimensionality
three
dimensionally modulated
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Properties

• Tiny particels with very high aspect ratio, and
  hence larger surface area.
• Larger surface area enables better adhesion with
  the matrix/surface.
• Improvement in the mechanical performance of the
  parent material.
• Better transparency due to small size(gtwavelength
  of light).

16
Nanoparticles

• A lot of research literature in this area.
• Common in everyday life.
• Examples include film materials, catalyst, ion
  exchangers, nanocrystals, semiconductors -
  quantum dots, molecular diodes.

Source www.kodak.com
http//rescomp.stanford.edu/gcronin/sld007.htm
17
Nanoclays

• Silicates layers separated by an interlayer or
  gallery.
• Silicates layers are 1 nm thick, 300 nm to
  microns laterally.
• Polymers as interlayers.
• Tailor structural, optical properties

http//rescomp.stanford.edu/gcronin/sld0011.htm
18
Nanofibers - Nanotubes

• Nanotubes in metal, metal oxide and ceramic
  matrix have also been fabricated.
• Typical fabrication process is by hot-pressing
  the powdered matrix with the nanotubes.
• Nanotubes in polymer matrices by mixing, then
  curing.
• Most important filler category in nanocpomposites

http//rescomp.stanford.edu/gcronin/sld0012.htm
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Nanocomposites

• Constituents have at least one dimension in the
  nanometer scale.
• Nanoparticles (Three nano-scale dimensions)
• Nanofibers (Two nano-scale dimensions)
• Nanoclays (One nano-scale dimensions)

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Typical Nano-materials
http//rescomp.stanford.edu/gcronin/sld007.htm
21
Characteristics
http//rescomp.stanford.edu/gcronin/sld008.htm
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Characteristics of Polymer Layered Silicates

• Due to the layer orientation, polymer-silicate
  nanocomposites exhibit stiffness, strength and
  dimensional stability in two dimensions (rather
  than one). In addition, because of the length
  scale involved that minimizes scattering,
  nanocomposites are usually transparent.
  Furthermore, PLS Polymer-Layered Silicate
  nanocomposites exhibit a significant increase in
  thermal stability as well as self-extinguishing
  characteristics.
• Uniform dispersion of these nanoscopically sized
  filler particles (or nanoelements) produces
  ultra-large interfacial area per volume between
  the nanoelement and host polymer. This immense
  internal interfacial area and the nanoscopic
  dimensions between nanoelements fundamentally
  differentiate PNCs from traditional composites
  and filled plastics. Thus, new combinations of
  properties derived from the nanoscale structure
  of PNCs provide opportunities to circumvent
  traditional performance trade-offs associated
  with conventional reinforced plastics,
  epitomizing the promise of nano-engineered
  materials.

www.me.berkeley.edu/nti/tan1.ppt
23
Nanocomposites

• Multi-constituent materials.
• Superior overall properties compared to
  constituent properties e.g. optical clarity,
  strength, stiffness, permeability.
• Ability to tailor properties.

www.me.berkeley.edu/nti/tan1.ppt
24
Continued

• From the structural point of view, the role of
  inorganic filler, usually as particles or fibers,
  is to provide intrinsic strength and stiffness
  while the polymer matrix can adhere to and bind
  the inorganic component so that forces applied to
  the composite are transmitted evenly to the
  filler. Meanwhile, the polymer matrix can also
  protect the surface of the filler from damage and
  keep the particle apart to hinder crack
  propagation.
• Nanocomposite materials can achieve much better
  properties than just the sum of its components as
  a result of interfacial interaction between the
  matrix and filler particles.

www.me.berkeley.edu/nti/tan1.ppt
25
Synthesis of Nanocomposites

• Chemical Synthesis 
• Gas Phase Synthesis
• Chemical Vapor Condensation
• Combustion Flame Synthesis
• Liquid Phase Synthesis

• Others
• Mechanical Deformation
• Thermal recrystallization

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Gas Phase Synthesis(Synthesis of ultra pure
metal powders and compounds of metal
oxides(ceramics) )
http//www.rpi.edu/dept/materials/COURSES/NANO/mor
aes/page1.html

• The nano powder formed normally has the same
  composition as the starting material.
• The starting material, which may be a metallic or
  inorganic material is vaporized using some source
  of energy
• The metal atoms that boil off from the source
  quickly loose their energy. These clusters of
  atoms grow by adding atoms from the gas phase and
  by coalescence
• A cold finger is a cylindrical device cooled by
  liquid nitrogen. The nano particles collect on
  the cold finger
• The cluster size depends on the particle
  residence time and is also influenced by the gas
  pressure, the kind of inert gas, i.e. He, Ar or
  Kr and on the evaporation rate of the starting
  material. The size of the nano particle increases
  with increasing gas pressure, vapor pressure and
  mass of the inert gas used.

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Chemical Vapor Condensation
http//www.rpi.edu/dept/materials/COURSES/NANO/mor
aes/page2.html

• the precursor vapor is passed through a hot
  walled reactor. The precursor decomposes and nano
  particles nucleate in the gas phase. The nano
  particles are carried by the gas stream and
  collected on a cold finger. The size of the nano
  particles is determined by the particle residence
  time, temperature of the chamber, precursor
  composition and pressure.

28
Combustion Flame Synthesis
http//www.rpi.edu/dept/materials/COURSES/NANO/mor
aes/page2.html

• Energy to decompose the precursor may be supplied
  by burning a fuel-air mixture with the precursor.
  In order to reduce agglomeration of the particles
  in the flame, the flame is specially designed to
  be low pressure.
• If you have observed the flame of a candle, you
  would have noticed that the flame consist of a
  blue center and a yellow to red periphery. This
  is because the temperature in the flame varies
  with position in the flame. Such a variation in
  the temperature profile of the flame would cause
  nanoparticles of different sizes to grow in the
  different regions of the flame. This is avoided
  by designing the flame to have a 'flat
  temperature profile' i.e. a constant temperature
  across its width.

29
Liquid Phase Synthesis
http//www.rpi.edu/dept/materials/COURSES/NANO/mor
aes/page3.html

• Two chemicals are chosen such that they react to
  produce the material we desire
• An emulsion is made by mixing a small volume of
  water in a large volume of the organic phase. A
  surfactant is added. The size of the water
  droplets are directly related to the ratio of
  water to surfactant. The surfactant collects at
  the interface between the water and the organic
  phase. If more surfactant were to be added,
  smaller drops would be produced and therefore, as
  will become apparent, smaller nano-particles.

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Carbon nanotubes

• Tubular form of carbon with nanoscale diameter
• Folding a 2D sheet of graphene in different
  directions
• Electronic properties depend on direction of
  folding
• Doping of semiconducting carbon nanotubes

From http//www.seas.upenn.edu/mse/images/nanotub
e1.jpg
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Laser ablation method to fabricate carbon
nanotubes

• Laser vaporises target (graphite catalyst)
• Carbon nanotubes from cooling mixture particles
• Proportion of catalyst controls type of nanotubes

http//www.ifw-dresden.de/iff/11/spec/areas/fuller
enes/spec_full_nano.html
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APPLICATIONS
Park et. al., Block copolymer lithography
Periodic arrays of 1011 holes in 1 square
centimeter, Science, 276, 1401-1404, 1997

• Composite Industry
• Drastic improvement in the mechanical
  performance of materials.
• Estimated Modulus

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Barrier Properties
http//www.rpi.edu/dept/materials/COURSES/NANO/mor
aes.html

• The silicate blocks are arranged alternately.
  Imagine a drop of water trying to get through the
  PLS barrier compared to a conventional filled
  polymer. The water drop would face more barrier
  going through the PLS nanocomposites because of
  the layered silicates arrangement.
• Uses 
• Packaging in food, medical and pharmaceutical
  industry

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Thermal Barrier Coatings(TBC) for Aircraft Gas
Turbine Engines

• Protection Required against
• High temperatures (gas T's up to approximately
  2000 C and component T's of approximately 1200
  C!)
• High partial pressures of oxygen
• High heat fluxes
• TBCs such as Alumina, Pt-Aluminide
• Higher gas temperatures gt higher engine
  efficiency
• Lower component temperatures (so they don't fail)
  
• Reduced cooling air requirements
• Moderation of thermal transients
• A decrease in the severity of engine hot spots by
  80-150C below normal values.

http//www.rpi.edu/dept/materials/COURSES/NANO/ste
wart/index.htm
35
Nanocrystalline Diamond Thin Films

• Uses based on Physical Strength
• Cutting Tools
• Protective Coatings
• Composite Additives

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Membranes

• Commonly made from Alumina, (Al2O3 ), Titania,
  (TiO2) , and Zirconia, (ZrO2)
• Membranes made of nanometer sized grains are
  stronger, less brittle and have higher
  temperature resistance than bulk ceramics. Pore
  sizes are on the order of 3-5 nanometers.
• Current uses
• Hemodialysis, Plasmapheresis - Separation of
  blood components and plasma from whole blood
• Potential uses High temp catalytic reactions ,
  solid oxide fuel cells

http//www.rpi.edu/dept/materials/COURSES/NANO/nar
ang/index.html
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Drug Delivery

• Attributes of Nanoparticulate Systems
• provide a better penetration of the particles
  inside the body.
• can be used for intramuscular or subcutaneous
  applications
• minimizes the irritant reactions at the injection
  site.
• exhibit greater stability, in both longer shelf
  storage lives and uptake times.
• and can be designed to elicit the desired
  kinetics, uptake, and response from the body(i.e.
  Biocompatibility).

http//www.rpi.edu/dept/materials/COURSES/NANO/bio
.htm
38
Medical

• Nanoceramics have already shown outstanding
  osteoblast proliferation (Webster et al.).
• If a hierarchical approach that mimics natural
  bone can be created for nanomaterials, these
  cellular interactions may be improved even
  further.
• Additionally, the corresponding increase in
  mechanical properties may allow previously
  unsuitable materials to become viable options for
  future implants.

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Summary of Applications

• Nanocomposite materials and coatings
• Thermal and environmental barriers
• Wear resistant coatings and parts
• Tailored optical barriers
• Flame retardant plastics
• High surface area nanostructures
• Catalysts (molecule specific)
• Energy storage media (nanoparticles, nanotubes)

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Hierarchical Nanostructures

• Ultrahigh-strength, tough structural materials
• Ductile and strong cements
• Net-shape formed ceramic parts
• Magnetic/thermoelectric thermal management
• New materials for MEMS
• Smart materials with embedded sensors and
  actuators

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Limitations!

• To date one of the few disadvantages associated
  with nanoparticle incorporation has concerned
  toughness and impact performance. Nanoclay
  modification of polymers such as polyamides,
  could reduce impact performance.
• Research will be necessary to develop a better
  understanding of formulation/structure/p
  roperty relationships, better routes to platelet
  exfoliation and dispersion etc.
• Economically feasible.

42
My Questions

• Which geometrical factor plays an important role
  in nanocomposites?
• Mention the processes for the synthesis of
  nanocomposites and explain any one of them in
  detail.

43
Questions?
44

• 1.      Date06/20/2003
• 2.      Presenters name Milind Arbatti
• 3.      Title of presentationNanocomposites
• The following is for the class to fill out and
  turn in at the end of each class
•  
• Name of student turning in this form
  _______________________
•  
• 4.      From 1 to 10 (ten being the best), how do
  you grade the materials presented? ______
• 5.      From 1 to 10 (ten being the best), were
  complete references given for each side? ______
• 6.      From 1 to 10 (ten being the best), how
  well is the presentation understandable? _______
• 7.      From 1 to 10 (ten being the best), how
  are the glossary, questions and problems
  presented? ______
• 8.      Suggestion