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1
Nanotechnology in
Mechanical Engineering Presented By
Pradip Majumdar Professor
Department of Mechanical Engineering Northern Illinois University
DeKalb, IL 60115
UEET 101 Introduction to Engineering
2
Outline of the Presentation
n Lecture n In-class group activities n Video Clips n Homework
3
Course Outline Lecture - I Introduction to Nano- Technology in Engineering
§ Basic concepts § Length and time scales § Nano-structured materials
- Nanocomposites - Nanotubes and nanowire § Applications and Examples
Lecture – II Nano-Mechanics Nanoscale Thermal and FlowPhenomena Experimental Techniques Modeling and Simulation
4
Lecture Topics
We will address some of the key issues of nano-technology in Mechanical Engineering.
Some of the topics that will be addressed are
nano-structured materials; nanoparticles and nanofluids, nanodevices and sensors, and applications.
5
Major Topics in Mechanical Engineering n Mechanics: Statics : Deals with forces, Moments,
equilibrium of a stationary body Dynamics: Deals with body in
motion - velocity, acceleration, torque, momentum, angular momentum.
n Structure and properties of material (Including strengths)
n Thermodynamics, power generation, alternate energy (power plants, solar, wind, geothermal, engines)
§ Design of machines and structures §Dynamics system, sensors and controls § Robotics §Computer-Aided Design (CAD/CAM) §Computational Fluid Dynamics (CFD) and Finite Element Method § Fabrication and Manufacturing processes
6
x = 10 mm x = 250 mm x = 500 mm x = 750 mm x = 1000 mm
DC power Supply
(-) (+)
Cathode Electrode Anode
Electrode
Electron flow
Electrolyte membrane
+H
-e2
2H
Bipolar Plates
MEAs
Diesel Engine Simulation Model
Fuel Cell Design and Development
No slip condition
Slip Conditions
Flow in micro channel
7
Length Scales in Sciences and Mechanics
1010- 810- 610-
Quantum Mechanics
Molecular Mechanics
Nano-mechanics
310-
Micro- mechanics
010
Macro- Mechanics
Regimes of Mechanics
Length Scales (m)
Quantum Mechanics: Deals with atoms - Molecular Mechanics: Molecular Networks - Nanomechanics: Nano-Materials - Micromechanics:
Macro-mechanic:
Continuum substance
8
Quantum and Molecular Mechanics § All substances are composed molecules or atoms in
random motion. n For a system consisting of cube of 25-mm on each side
and containing gas with atoms. n To specify the position of each molecule, we need to
three co-ordinates and three component velocities n So, in order to describe the behavior of this system
form atomic view point, we need to deal with at least equations. n This is quite a computational task even with the most
powerful (massively parallel multiple processors) computer available today.
n There are two approaches to handle this situations: Microscopic or Macroscopic model
20106 ´
2010
9
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 n Consider gross or average behavior of a number of molecules
that can be handled based on the continuum assumption. n We mainly deal with time averaged influence of many molecules. n These macroscopic or average effects can be perceived by our
senses and measured by instruments. n This leads to our treatment of substance as an infinitely divisible
substance or continuum.
10
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 Where is the smallest volume for which substance can be
assumed as continuum. n 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.
n Figure shows such variation in density as volume decreases below the continuum limit.
Vmlim
/VVdd
=rd®d
/Vd
r
Vd
11
Macroscopic Properties and Measurement
Pressure Pressure is defined as the average normal-component of force per unit area and expressed as Where is the smallest
volume for which substance can be assumed as continuum.
AFP n
/AAlim d
d=
d®d
/Ad
Ad
Fd
nFd
P
Pressure Gauge
Gas Tank
Pressure Measurement
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. Unit: Pascal (Pa) or 2m
N
12
Introduction- Nanotechnology
§Nanoscale uses “nanometer” as the basic unit of measurement and it represents a billionth of a meter or one billionth of a part.
n Nanotechnology deals with nanosized particles and devices
n One- nm is about 3 to 5 atoms wide. This is very tiny when compared normal sizes encounter day-to-day.
- For example this is 1/1000th the width of human hair.
13
n Any physical substance or device with structural dimensions below 100 nm is called nanomaterial or nano-device.
n 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.
14
n Nanoparticles can be defined as building blocks of nanomaterials and nanotechnology.
n Nanoparticles include nanotubes, nanofibers, fullerenes, dendrimers, nanowires and may be made of ceramics, metal, nonmetal, metal oxide, organic or inorganic.
n At this small scale level, the physical, chemical and biological properties of materials differ significantly from the fundamental properties at bulk level.
n Many forces or effects such inter-molecular forces, surface tension, electromagnetic, electrostatic, capillary becomes significantly more dominant than gravity.
n 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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n A structure of the size of an atom represents one of the fundamental limit.
n Fabricating or making anything smaller require manipulation in atomic or molecular level and that is like changing one chemical form to other.
n Scientist and engineers have just started developing new techniques for making nanostructures.
Nanoscience
Nanofabrication Nanotechnology
The nanoscience is matured.
The age of nanofabrication is here.
The age of nanotechnology - that is the practical use of nanostructure has just started.
16
Nanotechnology in Mechanical Engineering
New Basic Concepts
Nano-Mechanics Nano-Scale
Heat Transfer Nano-fluidics
Applications
17
Applications
§ Structural materials § Nano devices and sensors § Coolants and heat spreaders § Lubrication n Engine emission reduction n Fuel cell – nanoporous
electrode/membranes/nanocatalyst n Hydrogen storage medium n Sustainable energy generation - Photovoltaic cells for
power conversion n Biological systems and biomedicine
18
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
19
Length Scales Two regimes: I. Classical microscale size-effect domain – Useful for
microscale heat transfer in micron-size environment.
=cL
=lm
Where
characteristic device dimension
mean free path length of the substance )1(O
mcL
<l
II. Quantum nanoscale size-effect domain – More relevant to nanoscale heat transfer Where characteristic wave length of the electrons or phonons
)1(OccL
<l
=lc
20
n This length scale will provide the guidelines for analysis method- both theoretical and experimental methods:
classical microscale domain or nanoscale size-effect domain.
21
Flow in Nano-channels n 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.
n Knudsen number ( ) is typical parameter used to classify the length scale
and flow regimes:
LKn l
=
Kn < 0.01: Continuum approach with traditional Navier-Stokes and no-slip boundary conditions are valid. 0.01<Kn<0.1: Slip flow regime and N-S with slip boundary conditions are applicable 0.1<Kn<10: Transition regime – Continuum approach completely breaks – Molecular Dynamic Simulation Kn > 10 : Free molecular regime – The collision less Boltzman equation is applicable.
22
Time Scales
Relaxation time for different collision process: Relaxation time for phonon-electron interaction: Relaxation time for electron-electron interaction: Relaxation time for phonon-phonon interaction:
)s 1110( O -
)s 1310( O -
)s 1310( O -
23
Nanotechnology: Modeling Methods
n Quantum Mechanics n Atomistic simulation n Molecular Mechanics/Dynamics Nanomechanics Nanoheat transfer and Nanofluidics
24
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
Inter-Molecular Distance
Force
Inter-molecular Potential Model
25
Nanotools n Nanotools are required for manipulation of matter at
nanoscale or atomic level. n Certain devices which manipulate matter at atomic or
molecular level are Scanning-probe microscopes, atomic force microscopes, atomic layer deposition devices and nanolithography tools.
n Nanolithography means creation of nanoscale structure by etching or printing.
n Nanotools comprises of fabrication techniques, analysis and metrology instruments, software for nanotechnology research and development.
n Softwares are utilized in nanolithography, 3-D printing, nanofluidics and chemical vapor deposition.
26
Nanoparticles and Nanomaterials Nanoparticles: n Nanoparticles are significantly larger than individual
atoms and molecules. n Nanoparticles are not completely governed by either
quantum chemistry or by laws of classical physics. n Nanoparticles have high surface area per unit volume. n 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.
n Nanoparticles are made from chemically stable metals, metal oxides and carbon in different forms.
27
Carbon -Nanotubes § Carbon nanotubes are hollow
cylinders made up of carbon atoms. n The diameter of carbon nanotube is
few nanometers and they can be several millimeters in length.
n Carbon nanotubes looks like rolled tubes of graphite and their walls are like hexagonal carbon rings and are formed in large bundles.
n Have high surface area per unit volume
n Carbon nanotubes are 100 times stronger than steel at one-sixth of the weight.
n Carbon nanotubes have the ability to sustain high temperature ~ 2000 C.
28
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.
29
§ Formed by combining two or more nanomaterials to achieve better properties.
§ Gives the best properties of each
individual nanomaterial. § Show increase in strength, modulus of
elasticity and strain in failure. § Interfacial characteristics, shape,
structure and properties of individual nanomaterials decide the properties.
§ Find use in high performance,
lightweight, energy savings and environmental protection applications
- buildings and structures, automobiles and aircrafts.
Nanocomposites
30
§ 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.
31
§ 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 creating increased surface area per unit volume. § Decrease in grain size causes increase in volumetric fraction of grain boundaries, which leads to changes in fundamental properties of materials.
Nanostructured Materials
Different behavior of atoms at surface has been observed than atom at interior. Structural and compositional differences between bulk material and nanomaterial cause change in properties.
32
§ 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 and in new manufacturing technologies.
33
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 Nanoparticle materials: - Metal Oxides: - Stable metals: Au, cu - Carbon: carbon nanotubes (SWNTs, MWNTs), diamond, graphite, fullerene, Amorphous Carbon - Polymers : Teflon
3O2Al 2ZrO 2SiO 4O3Fe
34
Nanofluid Heat Transfer Enhancement
n 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.
n Increased convective heat transfer characteristic for heat transfer fluids as coolant or heating fluid.
-
35
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
36
Nano-fluid Applications
§ Energy conversion and energy storage system § Electronics cooling techniques § Thermal management of fuel cell energy systems n Nuclear reactor coolants n Combustion engine coolants n Super conducting magnets n Biological systems and biomedicine
37
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..
38
National Nanotechnology Initiative in Medicine
n Improved imaging (See: www.3DImaging.com) n Treatment of Disease n Superior Implant n Drug delivery system and treatment using
Denrimers, Nanoshells, Micro- and Nanofluidics and Plasmonics
39
-Nano-particles delivers treatment to targeted area or targeted tumors
- Release drugs or release radiation to heat up and destroy tumors or cancer cells
- In order to improve the durability and bio-compatibility, the implant surfaces are modified with nano-thin film coating (Carbon nano-particles).
- An artificial knee joint or hip coated with nanoparticles bonds to the adjacent bones more tightly.
40
Self Powered Nanodevices and Nanogenerators
n Nanosize devices or machined need nano-size power generator call nanogenerators without the need of a battery.
n Power requirements of nanodevices or nanosystems are generally very small
– in the range of nanowatts to microwatts. n Example: Power source for a biosensor - Such devices may allow us to develop implantable
biosensors that can continuously monitor human’s blood sugar level
41
n Waste energy in the form of vibrations or even the human pulse could power tiny devices.
n Arrays of piezoelectric could capture and transmit that waste energy to nanodevices
n There are many power sources in a human body: - Mechanical energy, Heat energy, Vibration energy, Chemical energy n A small fraction of this energy can be converted into electricity to
power nano-bio devices. n 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
42
Nano-sensor and Nano-generator
Nano-sensor Capacitor
Nano-generator
43
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.
44
Conversion of Mechanical Energy to Electricity in a Nanosystem
Tension Compression
Nanowire
Tension Compression
Nanowire
Rectangular electrode with ridged underside.
Moves side to side in response to external motion of the structure
Array of nanowires (Zinc Oxide) with piezoelectric and semiconductor properties
Gravity do not play any role for motion in nanoscale.
Nanowire is flexed by moving a ridged from side to side.
45
Example: Thermo Electric Nano-generator
§ Thermoelectric generator relies on the Seebeck Effect where an electric potential exists at the junction of two dissimilar metals that are at different temperatures.
§ The potential difference or the voltage produced is
proportional to the temperature difference. - Already used in Seiko Thermic Wrist Watch
46
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?