Chapters 1-2

Introduction of Material Science

Teaching General Chemistry, A Materials Science Companion, by A.B. Ellis, M.J. Geselbracht, B.J. Johnson, G.C. Lisensky, W.R. Robinson, ACS, Washington, D.C., 1993

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Metallurgy:Some General Considerations

An ore is a solid deposit containing a sufficiently high percentage of a mineral to make extraction of a metal economically feasible.

Native ores are free metals and include gold and silver. Oxides include iron, manganese, aluminum, and tin. Sulfides include copper, nickel, zinc, lead, and mercury. Carbonates include sodium, potassium, and calcium. Chlorides (often in aqueous solution) include sodium,

potassium, magnesium, and calcium.

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Extractive Metallurgy

Metallurgy is the general study of metals. Extractive metallurgy focuses on the activities

required to obtain a pure metal from one of its ores.

oresconcentration & physically separatingwaste rock

roasting

reductionslag

refininglow purity metal

high purity metal

metal oxide

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Techniques for characterization of materials

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Elemental analysis- Combustion analysis- ICP-AES, XPS, EDX (Energy dispersive X-ray spectroscopy )

Crystalline structure- Single crystal & Powder X-ray diffraction (XRD)- Neutron diffraction

Oxidation state & Coordination- X-ray absorption spectra- X-ray photoelectron spectra (XPS & Auger)- Solid state NMR ( mainly coordination)- IR & Raman ( mainly coordination)- UV-Vis spectra

Morphology- SEM, TEM, AFMSurface area & Pore size

- N2 adsorption-desorption isotherm- Mercury Intrusion Porosimetry

Elemental Analysis of C, H, N, S

Combustion analysis

Example:

C6H5NH2 + 35/2 O2 6 CO2 + 7/2 H2O + NO2Slide 9 of 55

Atomic Emission Spectra of Some Elements

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Inductively Coupled Plasma (ICP)- Excitation of the Sample for Elemental Analysis

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The Photoelectric Effect

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Albert Einstein considered electromagnetic energy to be bundled in to little packets called photons.

Energy of photon = E = hv Photons of light hit surface electrons and transfer their energy

hv = B.E. + K.E.

The energized electrons overcome their attraction and escape from the surface

Photoelectron spectroscopy detects the kinetic energy of the electron escaped from the surface. XPS X-ray as the light source, core electrons escaped UPS UV as the light source, valence electrons escaped

hve- (K.E.)

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Ek = h Eb = work function

Ek(KL1L2) = [Eb(K) Eb(L1)] Eb(L2)

X-ray

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Braggs Law

2d sin = n

X-Ray Diffraction

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Thermal energy

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Anatase638

515 395

200400600800

Rutile445

608

200400600800

Fig. 3.2 FT-Raman spectra of TiO2 of anatase and rutile phases: (a) lab-made, and after calcination at (b) 400 , (c) 700 , in comparison to (d) ) commercially available.

(a)(a)

(b)(b)

(c) (c)(d)

(d)

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(scanning transmission electron microscope)

By using different analytical capabilities with SEM, one can correlate properties of a material. Here, a topographical image of CdTe (left micrograph) is correlated with a cathodoluminescence image (right micrograph), to indicate those areas that are active (brighter areas) and those that represent recombination centers (darker areas).

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Two HRTEM (high-resolution TEM) images. The left image reveals a buried hexagonal phase in cubic CdTe. The right image shows the atomic structure of planar defects in thin-film silicon: a twin defect (in which the upper layers are rotated 180o from the lower layers), an intrinsic stacking fault (ISFin which adjacent layers are shifted slightly), and an extrinsic stacking fault (ESFin which there is an intervening layer between two layers slightly shifted from each other).

[National Renewable Energy Lab, USA]

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Piezoelectric crystalPiezoelectricity is the ability of certain crystals to generate a voltage in response to applied mechanical stress.

Compressed Net dipole

Equilibrium

Opposite voltage compression of crystal

Applied voltage expansion of crystal

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Materials

Quartz crystals were the first commercially exploited piezoelectric material .

many other materials exhibit the effect, including quartz analogue crystals like berlinite (AlPO4) and gallium orthophosphate (GaPO4), ceramics with perovskite or tungsten-bronze structures (BaTiO3, SrTiO3, Pb(ZrTi)O3, KNbO3, LiNbO3, LiTaO3, BiFeO3, NaxWO3, Ba2NaNb5O15, Pb2KNb5O15).

Bone exhibits some piezoelectric properties, due to the apatite (Ca5(PO4)3(OH, F, Cl) ) crystals.

Polyvinylidene fluoride, PVDF, exhibits piezoelectricity several times larger than quartz.

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Applications

High-voltage sourcesgenerate potential differences of thousands of volts

Sensorsphysical dimension, sound, weight

Actuatorspositioning objects with extreme accuracy.

Frequency standardemploy a tuning fork made from quartz that uses a combination of both direct and converse piezoelectricity to generate a regularly timed series of electrical pulses that is used to mark time.

Piezoelectric motors Types of piezoelectric motor include the well-known travelling-wave motor used for auto-focus in reflex cameras, inchworm motors for linear motion, and rectangular four-quadrant motors with high power density (2.5 watt/cm) and speed ranging from 10 nm/s to 800 mm/s.

Ultrasonic transducers Ultrasonic transducers can inject ultrasound waves into the body, receive the returned wave, and convert it to an electrical signal (a voltage). Most medical ultrasound transducers are piezoelectric.

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Electron mobility

Atomic vibration

Law of Dulong & Petit

Heat capacity of Solids

For ideal gas, Cv = E/T = 3/2 R3 degree of freedom in translational movement

Equipartition theorem:At equilibrium, there is on average RT of energy for each independent degree of freedom in a chemical system.

For a crystal of metal atoms, there are 6 degree of freedom: 3 for three-dimensional kinetic energy and 3 for three-dimensional potential energy.C = 6 x ( R ) = 3R = 3x8.314J 25J mol-1K-1

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For polyatomic solids, C = p x (3R)

p: number of atoms in the chemical formula of the solid

p = 2 for NaF, KCl, MgO, CaOMolar heat capacity = 6R 50 J mol-1K-1

p = 3 for CaF2, SiO2Molar heat capacity = 9R 75 J mol-1K-1

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Ceramic Materials

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Ceramic parts made of Si3N4

Thermal Insulating Ceramic Tilesfor space shuttle

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Superconductor

(Zero Resistance)()

Conductor

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(K)

(K)(K)

00

00

Semiconductor

?!

1911Kamerlingh-Onnes()4.2 K

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High- temperature Superconductor

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ABCDEF

Meissner Effect- excluding the magnetic field lines

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Slide 42 of 55diamagnetism : systems contain no unpaired electrons

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Preparation of ferrofluids

A. 2 FeCl3 + FeCl2 + 8 NH3 + 4 H2O Fe3O4 (s) + 8 NH4Cl (aq)

B. Add cis-oleic acid [CH3(CH2)7CH=CH(CH2)7COOH ] in oil

C. Remove water

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A ferrofluid, influenced by a magnet underneath.

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http://upload.wikimedia.org/wikipedia/commons/e/e1/Ferrofluid-1.JPG

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Electrorheological fluid suspension of particles in a liquid medium whose viscosity can be tuned by an applied electric field

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An ER fluid consists of fine polarizable particlessuspended in a fluid of lower dielectric constant.

Typically such fluids are assembled with a continuous hydrophobic liquid phase (e.g. silicone oil) containing hydrophilic particles (e.g. zeolite).

The density of the particles is matched as closely as possible with that of the oil to ensure good dispersion upon mixing of the ER fluid.

An applied electric field aligns the dipoles of water molecules trapped in particles, thus polarizing the particles. Particle polarization changes their organization in the fluid and causes changes in fluid rheologicalproperties.

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silicone oil -dimethylpolysiloxane hydrolyzate

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zeolite - crystalline aluminosilicate with open structures

Type A

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Carbon fiber Each carbon filament is made out of long, thin sheets of carbon similar to graphite. A common method of making carbon filaments is the oxidation and thermal pyrolysis of polyacrylonitrile (PAN). The carbon fiber usually contains 93-95% carbon. Carbon heated in the range of 1500-2000 C (carburizing) exhibits the highest tensile strength (820,000 psi or 5,650 MPa or 5,650 N/mm), while carbon fiber heated from 2500-3000 C (graphitizing) exhibits a higher modulus of elasticity (77,000,000 psi or 531 GPa or 531 kN/mm).

http://upload.wikimedia.org/wikipedia/commons/4/44/Kohlenstofffasermatte.jpg

Carbon fiber reinforced plastic or (CFRP or CRP), is a strong, light and very expensive composite material or fiber reinforced plastic. Similar to glass-reinforced plastic, which is sometimes simply called fiberglass.

The plastic is most often epoxy, but other plastics, such as polyester, vinylester or nylon, are also sometimes used.

Applications are mainly in aerospace, automotive fields, as well as in sailboats, and notably in modern bicycles, where strong and light qualities are of importance. It is becoming increasingly common in small consumer goods as well, such as laptop computers, tripods, fishing rods, racquet sports frames, stringed instrument bodies, classical guitar strings, and drum shells.

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Epoxy or polyepoxideEpoxy group

Diepoxy prepolymers, n 25

crosslinkingdiamine

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Vinylester Resins

Polyester Resins

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Chapters 1-2Metallurgy:Some General ConsiderationsExtractive MetallurgyTechniques for characterization of materialsElemental Analysis of C, H, N, SAtomic Emission Spectra of Some ElementsThe Photoelectric Effect