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Materials Science (C)

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Materials Science (C) By Linda (Lin) Wozniewski lwoz_at_iun.edu and Mat Chalker chalker7_at_gmail.com – PowerPoint PPT presentation

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Title: Materials Science (C)


1
Materials Science (C)
  • By
  • Linda (Lin) Wozniewski
  • lwoz_at_iun.edu
  • and
  • Mat Chalker
  • chalker7_at_gmail.com

2
Disclaimer
  • This presentation was prepared using draft
    rules.  There may be some changes in the final
    copy of the rules.  The rules which will be in
    your Coaches Manual and Student Manuals will be
    the official rules

3
Safety
  • Students must wear
  • Closed shoes
  • Slacks or skirts that come to the ankles
  • Lab coat or lab apron
  • Indirect vent or unvented chemical splash proof
    goggles. No impact glasses or visorgogs are
    permitted
  • Sleeved Shirt (if wearing a lab apron)

4
What Students May Bring
  • Calculator
  • Any size 3 ring notebook
  • A writing instrument

5
What Supervisors Will Supply
  • Everything the student will need
  • This may include
  • Glassware
  • Reagents
  • Balances
  • Hot plates
  • Thermometers
  • Probes
  • Magnets
  • Stirrers
  • Models
  • Toothpicks and marshmellows

6
What is Material Science?
  • Take the paperclip we have given you
  • Bend it so that the inner part is 180º from the
    outer part
  • Does it break?
  • Bend it back.
  • Does it break?
  • How many times does it take till it breaks?
  • You have just done Material Science

7
Properties
  • Why did the paper clip break?
  • Why didnt all of the paper clips break on the
    same number of bends?
  • What is the difference between how these
    materials behave?
  • What about these?
  • What are properties of materials?
  • Density
  • Deformation under load
  • Stiffness
  • Fatigue
  • Surface area to volume
  • Crystal structure
  • Thermodynamics

8
Material Science
  • Material Science is a relatively new
    interdisciplinary field
  • It merges Metallurgy, Ceramics, and Polymers
  • It merges Chemistry, Physics, and Geology
  • Material Science takes advantage of the fact that
    we can not make pure crystals of anything the
    interesting effects of the impurities.
  • Material Science is a field where many of our
    students will find lucrative employment in the
    future.
  • Material Science also incorporates the
    fascinating area of nano-technology

9
Main Focus
  • Material Performance and Atomic Structure 50
  • Intermolecular Forces and Surface Chemistry 50
  • How to prepare Students
  • Experiment ideas
  • Resources

10
Classification of Pure Substances
11
Types of Solids
12
Materials Characteristics
13
Materials Characteristics
? Density
14
Metals
  • Metals low electronegativity metal cationic
    atoms in a sea of delocalized electrons.
    Metallic bonds from electrostatic interaction -
    different from ionic bonds.
  • Conducts electrons on the delocalaized valence
    level sea of electrons
  • malleable/ductile, hard, tough, can be brittle.

Iron
15
Ceramics
  • Covalent and ionic bonding of inorganic
    non-metals. electrons are localized in bonds -
    poor conductors, brittle and very thermally
    stable.
  • The crystal structure of bulk ceramic compounds
    is determined by the amount and type of bonds.
    The percentage of ionic bonds can be estimated by
    using electronegativity determinations.
    Resistance to shear and high-energy slip is
    extremely high.
  • Atoms are bonded more strongly than metals fewer
    ways for atoms to move or slip in relation to
    each other. Ductility of ceramic compounds is
    very low and are brittle. Fracture stresses that
    initiate a crack build up before there is any
    plastic deformation and, once started, a crack
    will grow spontaneously.

Alumina Al2O3
http//mst-online.nsu.edu/mst/ceramics/ceramics3.h
tm
16
Semiconductors
  • Metalloid in composition (w/ exception).
    Covalently bonded. More elastic than ceramics.
  • Characterized by the presence of a band gap where
    electrons can become delocalized within the
    framework.

Germanium
17
Polymers
  • Macromolecules containing carbon covalently
    bonded with itself and with elements of low
    atomic number
  • Molecular chains have long linear structures and
    are held together through (weak) intermolecular
    (van der Waals) bonds. Low melting temp.

18
Materials Properties
  • Optical properties (Quantum Dots, LEDs)
  • Magnetic properties (ferrofluids)
  • Electronic Properties ( semiconductors)
  • Thermal and Mechanical Properities (plastics,
    metals, ceramics)

19
Materials Performance
  • Stress Vs. Strain relationship

20
Linear DeformationStress Strain
Stress - force applied over a given area. Units
of lbs/in2 or Gigapascals
Strain - Deformation of material as a change in
dimension from initial. Unitless
21
Stress, Strain, Youngs Modulus
  • Youngs Modulus
  • - a measure of material stiffness
  • - E s/e
  • F/A
  • l/L

Hookes Law F k?x spring constant k F/?x
22
Youngs Modulus
  • E s/e (F/Ao)/(?L/Lo)
  • Where
  • E Youngs Modulus
  • s Stress
  • e Strain
  • F Force
  • Ao Initial cross section of material
  • ?L Change in length of material
  • Lo Initial length of material

23
Yield Strength
Rubber
Glass
Polymers
True Elastic Behavior vs. Elastic Region
Vable, M. Mechanics of Materials Mechanical
properties of Materials. Sept. 2011
24
Nano World
The size regime of the nano world is 1 million
times smaller than a millimeter.
25
Units of length
26
SEM, TEM, AFM Images of CdSe Quantum Dots
Picture C.P. Garcia, V. Pellegrini , NEST
(INFM), Pisa. Artwork Lucia Covi http//mrsec.wis
c.edu/Edetc/SlideShow/slides/quantum_dot/QDCdSe.ht
ml http//www.jpk.com/quantum-dots-manipulation.20
7.en.html?imageadf24cc03b304a4df5c2ff5b4f70f4e9
27
Surface area to volume ratio
Surface Area
Volume
28
Consequences of Large Surface Area to Volume ratio
Gas law P nRT
V
As volume decreases, SA increases as does
pressure
29
Surface Tension
  • Depends on attractive forces in fluids
  • Examples
  • How to Measure
  • The force to break a known area free from the
    liquid is measured

30
Contact Angle
  • The relationship between the surface tension of
    the liquid and the attraction of the solid
  • Important if you want ink to stick to film or if
    you dont want water to stick to car or skis
  • Measured by finding angle between surface and
    tangential line drawn from drop contact

31
Surface Tension
  • Tension on thin glass or Pt plate measured
  • Equation
  • l is the wetted perimeter of the plate
  • 2d 2w
  • ? is the contact angle
  • In practice ? is rarely measured.
  • Either literature values are used or complete
    wetting is assumed (? 0)

32
Crystal Structure
33
Space Lattice
  • A lattice is an array of points repeated through
    space
  • A translation from any point through a vector
    Rlmnlambnc, where l, m, n are integers,
    locates an exactly equivalent point. a, b, c
    are known as lattice vectors.

34
Cubic Crystal Lattices
90º
The size and shape of a unit cell is described,
in three dimensions, by the lengths of the three
edges (a, b, and c) and the angles between the
edges (a, ß, and ?). These quantities are
referred to as the lattice parameters of the unit
cell.
35
Simple Cubic
36
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37
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38
Body Centered Cubic
39
Body Centered Cubic
40
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41
Face Centered Cubic
42
Face Centered Cubic
43
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44
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45
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46
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47
Characterizing a Crystal
48
Wave Particle Interaction
Interference in Scattered Waves
X-ray Diffraction in Crystalline Solids
49
Braggs Law
50
Diffraction Patterns
51
Common X-Ray Wavelengths
52
X-Ray Powder Diffraction Patterns
53
Miller Indices
Understanding crystal orientation
54
http//www.doitpoms.ac.uk/tlplib/miller_indices/pr
intall.php
55
Viscosity
  • A measure of resistance of a fluid to deformation
    or flow.
  • Water has a low viscosity. It is thin and flows
    easily
  • Honey has a high viscosity. It is thick and does
    not flow easily
  • Viscosity is measured usually in one of two ways
  • A given volume is timed to fall through a hole
  • Balls are timed falling through a given length

56
Creep Rate
  • Creep is the movement of material under stress
    over time usually at higher temperatures
  • Creep ends when the material breaks

57
Fracture Toughness
  •  

K1 is the fracture toughness
s is the applied stress
a is the crack length
ß is a crack length and component geometry factor that is different for each specimen and is dimensionless.
58
Fatigue Limit
  • Maximum fluctuating stress a material can endure
    for an infinite number of cycles
  • Determined from a stress/cycles curve

59
Shear Modulus
  •  

60
Poissons Ratio
  • ? -etrans/eaxial
  • Where
  • ? Poissons Ratio
  • etrans Transverse Strain
  • eaxial Axial Strain
  • e ?L/Lo
  • ?L Change in length of material
  • Lo Initial length of material

61
Resources
  • For Event Supervisors
  • http//mypage.iu.edu/lwoz/socrime/index.htm
  • For Lesson Plans for classroom use
  • http//mypage.iu.edu/lwoz/socrime/index.htm
  • Miller Indices
  • http//www.doitpoms.ac.uk/tlplib/miller_indices/pr
    intall.php
  • Stress, Strain, etc.
  • http//www.ndt-ed.org/EducationResources/Community
    College/Materials/Mechanical/Mechanical.htm

62
Resources Continued
  • YouTube.
  • LOTS of nice videos on stress, strain, Youngs
    Modulus, etc.
  • Contact Angles
  • http//www.csu.edu/chemistryandphysics/csuphysvan/
    participantactivities/Kondratko.FengertHS.ContactA
    ngleIFTWetting.pdf

63
Workshop Test
  • Unwrap a Hersheys Kiss without hurting the
    wrapper.
  • Flatten the wrapper out completely
  • Draw a circle around the widest part of the kiss
  • Put the Kiss, on the wrapper out in the sun or in
    front of a heat lamp, noting the time
  • After doing each of the next events (10 min), go
    out, note the time, and draw a circle around the
    kiss.

64
Youngs Modulus
  • Form some Play dough into a cylinder
  • Determine the height and radius
  • Attach a dual force sensor with a round tip to
    the calculator.
  • Determine the force of the cylinder resting in an
    empty petri dish balanced on top of the sensor
  • Push down, noting the force
  • Determine the new height

65
Youngs Modulus Continued
  • Stress Force/Area0
  • Determine difference in Force
  • Determine the initial area of the cylinder
  • Divide
  • Strain ?L/L0
  • Determine the difference in the heights
  • Divide the difference by the original height
  • Youngs Modulus
  • Divide Stress by Strain

66
Surface Tension
  • Fill petri dish with water.
  • Use Pasteur pipette to drops of water to slide
    until large enough drop to measure contact angle.
  • Measure width of slide
  • Attach dual force sensor with hook end to
    calculator
  • Attach slide suspended from clamp to hook
  • Determine Force
  • Determine Force when slide just touches water
  • Determine how far up water moves on slide

67
Surface Tension
  • Determine perimeter of water on slide
  • Determine force difference
  • Surface tension is
  • l is the perimeter
  • ? is the contact angle
  • F is the difference in the forces

68
Thickness of a Molecule
  • Fill the pie plate with water
  • Sprinkle chalk dust on top
  • Determine how many drops from the Pasteur pipette
    are required to make 1 ml.
  • Add one drop of soap to the center of the pie
    plate.
  • Determine the radius of the circle of soap
  • Since the soap has a hydrophobic part, it will
    spread out 1 molecule thick on top of the water.
  • Divide the volume of the drop by the area

69
Face Centered Cube
  • Put 4 toothpicks at right angles to each other
    around the middle of one marshmallow.
  • Repeat for 5 more marshmallows
  • Pick 2 of your toothpicked marshmallows add
    marshmallows to the 8 toothpicks
  • These are now 2 of the sides of the cube.
  • The other 4 toothpicked marshmallows are the
    insides of the cube.
  • Put the toothpicks into the edge marshmallows to
    form cube

70
Questions Continued
n? 2d(sin?)
  • Using CuKa radiation (?.154 nm), the 1st order
    reflection for the spacing between the 200
    planes of gold occurs at a 2? angle of 44.5º
  • What is the spacing between the 200 planes?
  • What is the value of a?
  • What is the radius of gold?

 
a.406 nm
r.203 nm
71
Surface Area/Volume Relationship
  • Using your play dough, make a 1 cm cube, 2 cm
    cube, and 3 cm cube.
  • Determine the surface area of each
  • Determine the volume of each
  • Divide the surface area by the volume
  • What trend do you see?

72
Creep Rate
  • Retrieve the kiss
  • Note the time and draw the last circle around the
    bottom
  • Without removing the circle lines, remove the
    kiss.
  • Measure all of the diameters and match them to
    their times
  • Using your calculator, make a spreadsheet of the
    times vs. the diameters.
  • Subtract the original diameter from each diameter

73
Creep Rate
  • Divide the differences in the diameters by the
    original diameter and multiply by 100 to get the
    percent stress
  • Plot the time on the x axis vs. the stress on the
    y axis.
  • Determine the slope of the middle range by
    defining the area of interest and then finding
    the tangent.
  • The creep rate is the slope

74
Deflection
  • Measure the length and diameter of a straightened
    paperclip.
  • Suspend the paperclip across two tall containers
    so the paperclip is resting at its two ends.
    Place a ruler across the containers too.
  • Attach a dual range force sensor with a hook to
    the calculator
  • Pull down in the center of the paperclip until
    the clip is deflected down a measureable amount.
  • Note the deflection and the Force difference.

75
Deflection
  • The formula for deflection is
  • d (Wl3)/(12pr4Y)
  • Solving for Youngs Modulus (Y) we get
  • Y (WI3)/12pr4d)
  • W force added
  • I length of paperclip
  • d deflection
  • r radius of paperclip diameter/2
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