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Materials Science (C) By Linda (Lin) Wozniewski lwoz@iun.edu and Mat Chalkerchalker7@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 Calculator Any size 3 ring notebook Any size 3 ring notebook A writing instrument 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 didn’t 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 Material Science is a relatively new interdisciplinary field It merges Metallurgy, Ceramics, and Polymers’ It merges Metallurgy, Ceramics, and Polymers’ It merges Chemistry, Physics, and Geology 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 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 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 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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ρ ≡ 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. http://mst-online.nsu.edu/mst/ceramics/ceramics3.htm Alumina Al 2 O 3 Al 2 O 3

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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 Deformation–Stress & Strain Stress - force applied over a given area. Units of lbs/in 2 or Gigapascals Strain - Deformation of material as a change in dimension from initial. *Unitless

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Stress, Strain, & Young’s Modulus Young’s Modulus Young’s Modulus - a measure of material “stiffness” - a measure of material “stiffness” - E = σ/ε - E = σ/ε = F/A = F/A l/L l/L Hooke’s Law: F = k ∗ Δ x spring constant: k = F/ Δ x

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Young’s Modulus E = σ/ε= (F/A o )/(ΔL/L o ) Where E = Young’s Modulus σ = Stress ε = Strain F = Force A o = Initial cross section of material ΔL = Change in length of material L o = Initial length of material

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Yield Strength Vable, M. Mechanics of Materials: Mechanical properties of Materials. Sept. 2011 Rubber Glass Polymers True Elastic Behavior vs. Elastic Region

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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.wisc.edu/Edetc/SlideShow/slides/quantum_dot/QDCdSe.html http://www.jpk.com/quantum-dots-manipulation.207.en.html?image=adf24cc03b304a4df5c2ff5b4f70f4e9cc03b304a4df5c2ff5b4f70f4e9

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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 As volume decreases, SA increases as does pressure V

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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 don’t 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 – θ is the contact angle In practice θ is rarely measured. Either literature values are used or complete wetting is assumed (θ = 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 R lmn +la+mb+nc, 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 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 (α, β, and γ). These quantities are referred to as the lattice parameters of the unit cell. 90º

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Simple Cubic

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Body 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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Bragg’s 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/printall.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 K1K1 is the fracture toughness σis the applied stress αis the crack length βis 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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Poisson’s Ratio ν = -ε trans /ε axial Where ν = Poisson’s Ratio ε trans = Transverse Strain ε axial = Axial Strain ε= ΔL/L o ΔL = Change in length of material L o = Initial length of material

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Resources For Event Supervisors – http://mypage.iu.edu/~lwoz/socrime/index.htm http://mypage.iu.edu/~lwoz/socrime/index.htm For Lesson Plans for classroom use – http://mypage.iu.edu/~lwoz/socrime/index.htm http://mypage.iu.edu/~lwoz/socrime/index.htm Miller Indices – http://www.doitpoms.ac.uk/tlplib/miller_indices/printall.php http://www.doitpoms.ac.uk/tlplib/miller_indices/printall.php Stress, Strain, etc. – http://www.ndt- ed.org/EducationResources/CommunityCollege/Materials/ Mechanical/Mechanical.htm

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Resources Continued YouTube. – LOTS of nice videos on stress, strain, Young’s Modulus, etc. Contact Angles – http://www.csu.edu/chemistryandphysics/csuphys van/participantactivities/Kondratko.FengertHS.Co ntactAngleIFTWetting.pdf

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Workshop Test Unwrap a Hershey’s 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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Young’s 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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Young’s Modulus Continued Stress = Force/Area 0 – Determine difference in Force – Determine the initial area of the cylinder – Divide Strain = ΔL/L 0 – Determine the difference in the heights – Divide the difference by the original height Young’s 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 – θ 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 Using CuK α radiation (λ=.154 nm), the 1 st order reflection for the spacing between the {200} planes of gold occurs at a 2θ angle of 44.5º – What is the spacing between the {200} planes? – What is the value of a? – What is the radius of gold? nλ = 2d(sinθ) 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 = (Wl 3 )/(12πr 4 Y) Solving for Young’s Modulus (Y) we get: – Y = (WI 3 )/12πr 4 d) – W = force added – I = length of paperclip – d = deflection – r = radius of paperclip = diameter/2

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Materials Science Chapter 8 Deformation and Fracture.

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