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

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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

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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)

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What Students May Bring

• Calculator
• Any size 3 ring notebook
• A writing instrument

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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

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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

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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

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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

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Main Focus

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

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Classification of Pure Substances
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Types of Solids
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Materials Characteristics
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Materials Characteristics
? Density
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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
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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
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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
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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.

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Materials Properties

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

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Materials Performance

• Stress Vs. Strain relationship

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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
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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
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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

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Yield Strength
Rubber
Glass
Polymers
True Elastic Behavior vs. Elastic Region
Vable, M. Mechanics of Materials Mechanical
properties of Materials. Sept. 2011
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Nano World
The size regime of the nano world is 1 million
times smaller than a millimeter.
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Units of length
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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
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Surface area to volume ratio
Surface Area
Volume
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Consequences of Large Surface Area to Volume ratio
Gas law P nRT
V
As volume decreases, SA increases as does
pressure
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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

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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

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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)

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Crystal Structure
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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.

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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.
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Simple Cubic
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Body Centered Cubic
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Body Centered Cubic
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Face Centered Cubic
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Face Centered Cubic
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Characterizing a Crystal
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Wave Particle Interaction
Interference in Scattered Waves
X-ray Diffraction in Crystalline Solids
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Braggs Law
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Diffraction Patterns
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Common X-Ray Wavelengths
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X-Ray Powder Diffraction Patterns
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Miller Indices
Understanding crystal orientation
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http//www.doitpoms.ac.uk/tlplib/miller_indices/pr
intall.php
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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

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Creep Rate

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

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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.
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Fatigue Limit

• Maximum fluctuating stress a material can endure
  for an infinite number of cycles
• Determined from a stress/cycles curve

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Shear Modulus

•  

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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

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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

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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

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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.

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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

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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

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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

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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

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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

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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

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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
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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?

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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

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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

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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.

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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