Transcript Nanotechnology in Mechanical Engineering

Nanotechnology
in
Mechanical Engineering
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Outline of the Presentation
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Lecture
In-class group activities
Video Clips
Homework
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Course Outline
Lecture - I
Introduction to NanoTechnology in Engineering
 Basic concepts
 Length and time scales
 Nano-structured materials
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Lecture – II
Nano-Mechanics
Nanoscale Thermal
and FlowPhenomena
Experimental
Techniques
- Nanocomposites
- Nanotubes and nanowire
Modeling and
Applications and Examples Simulation
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Lecture Topics
We will address some of the key issues of nanotechnology in Mechanical Engineering.
Some of the topics that will be addressed are
nano-structured materials; nanoparticles and
nanofluids, nanodevices and sensors, and
applications.
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Major Topics in Mechanical Engineering
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Mechanics:
 Design of machines and
Statics : Deals with forces, Moments, structures
equilibrium of a stationary body
Dynamics system, sensors
Dynamics: Deals with body in
and controls
motion - velocity, acceleration,
 Robotics
torque, momentum, angular
Computer-Aided Design
momentum.
(CAD/CAM)
Structure and properties of
Computational Fluid
material (Including strengths)
Dynamics (CFD) and
Finite Element Method
Thermodynamics, power
 Fabrication and
generation, alternate energy
Manufacturing processes
(power plants, solar, wind,
geothermal, engines)
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Diesel Engine Simulation Model
Fuel Cell Design
and Development
Flow in micro channel
Bipolar Plates
Electron flow
DC power Supply
(+)
(-)
2e 
H
Anode
Electrode
Cathode
Electrode
No slip
x = 250 mm
condition
x = 10 mm
H2
Electrolyte membrane
MEAs
x = 1000
750 mm
Slipx =Conditions
mm
x = 500 mm
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Length Scales in Sciences and
Mechanics
Regimes of Mechanics
Quantum
Mechanics
s
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Molecular
Mechanics
Nanomechanics
Micromechanics
MacroMechanics
Quantum Mechanics:
Deals with atoms Molecular Mechanics:
Molecular Networks Nanomechanics:
Nano-Materials Micromechanics:
Macro-mechanic:
108
106
103
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Continuum
substance
Length Scales (m)
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Quantum and Molecular Mechanics
 All substances are composed molecules or atoms in
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random motion.
For a system consisting of cube of 25-mm on each side
and containing gas with 1020 atoms.
To specify the position of each molecule, we need to
three co-ordinates and three component velocities
So, in order to describe the behavior of this system
form atomic view point, we need to deal with at least
6  1020 equations.
This is quite a computational task even with the most
powerful (massively parallel multiple processors)
computer available today.
There are two approaches to handle this situations:
Microscopic or Macroscopic model
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Microscopic Vs Macroscopic
Approach -1: Microscopic viewpoint based on
kinetic theory and statistical mechanics
 On the basis of statistical considerations and probability theory,
we deal with average values of all atoms or molecules and in
connection with a model of the atom.
Approach – II Macroscopic view point
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Consider gross or average behavior of a number of molecules
that can be handled based on the continuum assumption.
We mainly deal with time averaged influence of many molecules.
These macroscopic or average effects can be perceived by our
senses and measured by instruments.
This leads to our treatment of substance as an infinitely divisible
substance or continuum.
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Breakdown of Continuum Model
 To show the limit of continuum or macroscopic model, let us
consider the concept of density:
 Density is defined as the mass
per unit volume and expressed as

m
lim / V
V  V
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V /
V
Where
is the smallest volume for which substance can be
assumed as continuum.
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Volume smaller than this will lead to the fact that mass is not
uniformly distributed, but rather concentrated in particles as
molecules, atoms, electrons etc.
Figure shows such variation in density as volume decreases below
the continuum limit.
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Macroscopic Properties and
Measurement
Pressure
Pressure is defined as the
average normal-component
of force per unit area and
expressed as
F
Fn
P  lim
Fn
/ A
A  A
A
Where A/ is the smallest
volume for which substance can
be assumed as continuum.
Unit: Pascal (Pa) or N 2
m
Pressure
Measurement
P
Gas
Tank
Pressure
Gauge
For a pressure gauge, it is the
average force (rate of change of
momentum) exerted by the
randomly moving atoms or
molecules over the sensor’s area.
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Introduction- Nanotechnology
 Nanoscale uses “nanometer” as the basic unit of
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measurement and it represents a billionth of a
meter or one billionth of a part.
Nanotechnology deals with nanosized particles
and devices
One- nm is about 3 to 5 atoms wide. This is very
tiny when compared normal sizes encounter dayto-day.
- For example this is 1/1000th the width of human
hair.
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Any physical substance or device with structural
dimensions below 100 nm is called nanomaterial
or nano-device.
Nanotechnology rests on the technology that
involves fabrication of material, devices and
systems through direct control of matter at
nanometer length scale or less than 100 nm.
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Nanoparticles can be defined as building blocks of
nanomaterials and nanotechnology.
Nanoparticles include nanotubes, nanofibers, fullerenes,
dendrimers, nanowires and may be made of ceramics,
metal, nonmetal, metal oxide, organic or inorganic.
At this small scale level, the physical, chemical and
biological properties of materials differ significantly from
the fundamental properties at bulk level.
Many forces or effects such inter-molecular forces,
surface tension, electromagnetic, electrostatic, capillary
becomes significantly more dominant than gravity.
Nanomaterial can be physically and chemically
manipulated to alter the properties, and these properties
can be measured using nanoscale sensors and gages.
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A structure of the size of an atom represents one of the
fundamental limit.
Fabricating or making anything smaller require
manipulation in atomic or molecular level and that is
like changing one chemical form to other.
Scientist and engineers have just started developing new
techniques for making nanostructures.
The nanoscience is matured.
Nanoscience
Nanofabrication
Nanotechnology
The age of nanofabrication is
here.
The age of nanotechnology that is the practical use of
nanostructure has just started.
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Nanotechnology in Mechanical
Engineering
New Basic
Concepts
NanoMechanics
Nano-Scale
Heat Transfer
Nano-fluidics
Applications
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Applications
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Structural materials
Nano devices and sensors
Coolants and heat spreaders
Lubrication
Engine emission reduction
Fuel cell – nanoporous
electrode/membranes/nanocatalyst
Hydrogen storage medium
Sustainable energy generation - Photovoltaic cells for
power conversion
Biological systems and biomedicine
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Basic Concepts
Energy Carriers
Phonon: Quantized lattice vibration energy with wave
nature of propagation
- dominant in crystalline material
Free Electrons:
- dominant in metals
Photon: Quantized electromagnetic energy with wave
nature of propagation
- energy carrier of radiative energy
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Length Scales
Two regimes:
I. Classical microscale size-effect domain – Useful for
microscale heat transfer in micron-size environment.
Lc
 O(1)
m
Where
 m  mean free path length of the substance
Lc 
characteristic device dimension
II. Quantum nanoscale size-effect domain –
More relevant to nanoscale heat transfer
Lc
 O(1)
c
Where
 c  characteristic wave length of the electrons
or phonons
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This length scale will provide the guidelines for
analysis method- both theoretical and
experimental methods:
classical microscale domain or nanoscale
size-effect domain.
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Flow in Nano-channels
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The Navier –Stokes (N-S) equation of continuum model fails when the
gradients of macroscopic variables become so steep that the length scale is of
the order of average distance traveled by the molecules between collision.
Knudsen number ( Kn  L ) is typical parameter used to classify the length scale
and flow regimes:
Kn < 0.01:
0.01<Kn<0.1:
0.1<Kn<10:
Kn > 10 :
Continuum approach with traditional Navier-Stokes
and no-slip boundary conditions are valid.
Slip flow regime and N-S with slip boundary
conditions are applicable
Transition regime – Continuum approach completely
breaks – Molecular Dynamic Simulation
Free molecular regime – The collision less Boltzman
equation is applicable.
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Time Scales
Relaxation time for different collision process:
Relaxation time for phonon-electron
interaction: O (1011 s)
Relaxation time for electron-electron
interaction: O (1013 s)
Relaxation time for phonon-phonon
interaction: O (1013 s)
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Nanotechnology: Modeling
Methods
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Quantum Mechanics
Atomistic simulation
Molecular Mechanics/Dynamics
Nanomechanics
Nanoheat transfer and Nanofluidics
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Models for Inter-molecules Force
- Inter-molecular Potential
Model
- Inverse Power Law Model or
Point Centre of Repulsion
Model
- Hard Sphere Model
- Maxwell Model
- Lennard-Jones Potential
Model
Force
Inter-Molecular Distance
Inter-molecular
Potential Model
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Nanotools
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Nanotools are required for manipulation of matter at
nanoscale or atomic level.
Certain devices which manipulate matter at atomic or
molecular level are Scanning-probe microscopes,
atomic force microscopes, atomic layer deposition
devices and nanolithography tools.
Nanolithography means creation of nanoscale structure
by etching or printing.
Nanotools comprises of fabrication techniques, analysis
and metrology instruments, software for
nanotechnology research and development.
Softwares are utilized in nanolithography, 3-D printing,
nanofluidics and chemical vapor deposition.
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Nanoparticles and Nanomaterials
Nanoparticles:
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Nanoparticles are significantly larger than individual
atoms and molecules.
Nanoparticles are not completely governed by either
quantum chemistry or by laws of classical physics.
Nanoparticles have high surface area per unit volume.
When material size is reduced the number of atoms on
the surface increases than number of atoms in the
material itself. This surface structure dominates the
properties related to it.
Nanoparticles are made from chemically stable metals,
metal oxides and carbon in different forms.
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Carbon -Nanotubes
 Carbon nanotubes are hollow
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cylinders made up of carbon atoms.
The diameter of carbon nanotube is
few nanometers and they can be
several millimeters in length.
Carbon nanotubes looks like rolled
tubes of graphite and their walls are
like hexagonal carbon rings and are
formed in large bundles.
Have high surface area per unit
volume
Carbon nanotubes are 100 times
stronger than steel at one-sixth of the
weight.
Carbon nanotubes have the ability to
sustain high temperature ~ 2000 C.
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There are four types of carbon
nanotube: Single Walled Carbon
Nanotube (SWNT), Multi Walled
Xarbon nanotube (MWNT), Fullerene
and Torus.
SWNTs are made up of single
cylindrical grapheme layer
MWNTs is made up of multiple
Grapheme layers.
SWNT possess important electric
properties which MWNT does not.
SWNT are excellent conductors, so finds
its application in miniaturizing
electronics components.
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Nanocomposites
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Formed by combining two or more
nanomaterials to achieve better
properties.
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Gives the best properties of each
individual nanomaterial.
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Show increase in strength, modulus of
elasticity and strain in failure.
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Interfacial characteristics, shape,
structure and properties of individual
nanomaterials decide the properties.
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Find use in high performance,
lightweight, energy savings and
environmental protection applications
- buildings and structures, automobiles
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 Examples of
nanocomposites include nanowires
and metal matrix composites.
 Classified into multilayered structures and inorganic or
organic composites.
 Multilayered structures are formed from self-assembly of
monolayers.
 Nanocomposites may provide heterostructures formed from
various inorganic or organic layers, leading to multifunctional
materials.
 Nanowires are made up of
various materials and find its
application in microelectronics for semiconductor devices. 30
Nanostructured Materials
 All the properties of nanostructured
are controlled by changes in atomic
structure, in length scales, in sizes
and in alloying components.
 Nanostructured materials are
formed by controlling grain sizes and Different behavior of atoms
creating increased surface area per at surface has been observed
than atom at interior.
unit volume.
 Decrease in grain size causes
Structural and
compositional differences
increase in volumetric fraction of
between bulk material and
grain boundaries, which leads to
changes in fundamental properties of nanomaterial cause change
in properties.
materials.
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 The size affected properties are color, thermal conductivity,
mechanical, electrical, magnetic etc.
 Nanophase metals show increase in hardness and modulus
of elasticity than bulk metals.
 Nanostructured materials are produced in the form of
powders, thin films and in coatings.
 Synthesis of nanostructured materials take place by Top –
Down or Bottom- Up method.
- In Top-Down method the bulk solid is decomposed into
nanostructure.
- In Bottom-Up method atoms or molecules are
assembled into bulk solid.
 The future of nanostructured materials deal with controlling
characteristics, processing into and from bulk material and32
Nanofluids
Nanofluids are engineered colloid formed with stable
suspemsions of solid nano-particles in traditional base
liquids.
Base fluids: Water, organic fluids, Glycol, oil, lubricants
and other fluids
Al 2 O 3
Nanoparticle materials:
ZrO 2 SiO2
Fe3O 4
- Metal Oxides:
- Stable metals: Au, cu
- Carbon: carbon nanotubes (SWNTs, MWNTs),
diamond, graphite, fullerene, Amorphous Carbon
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- Polymers : Teflon
Nanofluid Heat Transfer
Enhancement
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Thermal conductivity enhancement
- Reported breakthrough in substantially increase
( 20-30%) in thermal conductivity of fluid by
adding very small amounts (3-4%) of suspended
metallic or metallic oxides or nanotubes.
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Increased convective heat transfer
characteristic for heat transfer fluids as
coolant or heating fluid.
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Nanofluids and Nanofludics
Nanofluids have been investigated
- to identify the specific transport mechanism
- to identify critical parameters
- to characterize flow characteristics in macro,
micro and nano-channels
- to quantify heat exchange performance,
- to develop specific production, management
and safety issues, and measurement and
simulation techniques
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Nano-fluid Applications
 Energy conversion and energy storage system
 Electronics cooling techniques
 Thermal management of fuel cell energy systems
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Nuclear reactor coolants
Combustion engine coolants
Super conducting magnets
Biological systems and biomedicine
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Nano-Biotechnology
 When the tools and processes of nanotechnology are
applied towards biosystems, it is called nanobiotechnology.
 Due to characteristic length scale and unique properties,
nanomaterials can find its application in biosystems.
 Nanocomposite materials can play great role in
development of materials for biocompatible implant.
 Nano sensors and nanofluidcs have
started playing an
important role in diagnostic tests and drug delivering system
for decease control.
 The long term aim of nano-biotechnology is to build tiny
devices with biological tools incorporated into it diagonistic
and treatment..
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National Nanotechnology Initiative
in Medicine
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Improved imaging (See: www.3DImaging.com)
Treatment of Disease
Superior Implant
Drug delivery system and treatment using
Denrimers, Nanoshells, Micro- and Nanofluidics
and Plasmonics
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In order to improve the
durability and bio-compatibility,
the implant surfaces are modified
with nano-thin film coating
(Carbon nano-particles).
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- An artificial knee joint or hip
coated with nanoparticles bonds to
the adjacent bones more tightly.
-Nano-particles delivers
treatment to targeted area or
targeted tumors
- Release drugs or release
radiation to heat up and destroy
tumors or cancer cells
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Self Powered Nanodevices and
Nanogenerators
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Nanosize devices or machined need nano-size power
generator call nanogenerators without the need of a
battery.
Power requirements of nanodevices or nanosystems are
generally very small
– in the range of nanowatts to microwatts.
Example: Power source for a biosensor
- Such devices may allow us to develop implantable
biosensors that can continuously monitor human’s
blood sugar level
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Waste energy in the form of vibrations or even the human pulse
could power tiny devices.
Arrays of piezoelectric could capture and transmit that waste energy
to nanodevices
There are many power sources in a human body:
- Mechanical energy, Heat energy, Vibration energy,
Chemical energy
A small fraction of this energy can be converted into electricity to
power nano-bio devices.
Nanogenerators can also be used for other applications
- Autonomous strain sensors for structures such as bridges
- Environmental sensors for detecting toxins
- Energy sensors for nano-robotics
- Microelectromecanical systems (MEMS) or
nanoelectromechanical system (NEMS)
- A pacemaker’s battery could be charged without
requiring any replacement
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Nano-sensor and Nano-generator
Nanosensor Capacitor
Nanogenerator
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Example: Piezoelectric
Nanogenerator
Piezoelectric Effect
Some crystalline materials generates electrical voltage
when mechanically stressed
A Typical Vibration-based Piezoelectric Transducer
- Uses a two-layered beam with one end fixed
and other end mounted with a mass
- Under the action of the gravity the beam is bent with
upper-layer subjected to tension and lower-layer
subjected to tension.
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Conversion of Mechanical Energy to Electricity
in a Nanosystem
Tension
Compression
Nanowire
Array of
nanowires (Zinc
Oxide) with
piezoelectric and
semiconductor
properties
Tension
Compression
Nanowire
Gravity do not play
any role for motion
in nanoscale.
Nanowire is flexed
by moving a ridged
from side to side.
Rectangular electrode
with ridged underside.
Moves side to side in
response to external
motion of the
structure
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Example: Thermo Electric Nano-generator
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Thermoelectric generator relies on the Seebeck Effect
where an electric potential exists at the junction of
two dissimilar metals that are at different temperatures.
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The potential difference or the voltage produced is
proportional to the temperature difference.
- Already used in Seiko Thermic Wrist Watch
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Bio-Nano Generators
Questions:
1. How much and what different kind of energy
does body produce?
2. How this energy source can be utilized to
produce power.
3. What are the technological challenges?
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