mse lecture 1

8/11/2019 MSE Lecture 1

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Lecture 1: Chapter 1

James P. Schaffer, Ashok Saxena,

Stephen D. Antolovich, Thomas H.

Sanders, Jr. and Steven B.

Warner, The Science and Desig n

of Engin eering Materials,

Second Edition, Irwin, Chicago,

IL, 1999.

Materials Science and

Engineering Types of materials

Structure-Property-Process

relationships


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Role of Materials

Technology determines prosperity and power Breakthroughs in technology are linked to the

development of new materials and processes[examples: weapons (from swords to modern energetic materials to shock absorbing materials),

electronics (Si-based transistors in computers, phones, play stations), aircraft and space shuttles

(efficient engines, lightweight frames, temperature insulation), telecommunications (optical fibers),

solar cells, etc.]

Stone Age

Bronze Age

Iron Age

Silicon Age & Polymer Age

Without courtesy of the owner


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Other viewpoints

Organic materials, vs. Inorganic materials

Crystalline vs. Amorphous

Application: Electronic materials, Magnetic materials, Opticalmaterials, Structural materials, Bio materials etc.

1. Major classes of materials (our textbook)

Metals

Ceramics

Polymers

Semiconductors

Composites


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Structure of Materials

All matters are composed of atoms

All atoms are composed ofnucleus and electrons

Properties of an atom are determined by:

(1) number of electrons or protons in a neutral atom;

(2) mass;

(3) distribution of electrons in orbits;

(4) energy of electrons;

(5) ease of adding or removing electrons to create a charged ion

All nuclei consist of protons and neutrons

Properties of materials depend on what atoms they are made of and how

these atoms are arranged


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Structure of Materials How atoms are held together?

By primary (ionic, covalent, metallic) or

secondary (van der Waals) bonds

What is the difference between primary and secondary bonds?

Primary bonds involve either the transfer of electrons from

one atom to another or sharing electrons between atoms

Secondary bonds occur only due to interaction between

electrical dipoles (center of positivecharge is different from the center of

negative charge; the dipole can be

either permanent, induced, or temporary)

Primary bonds are much stronger

Can we predict the bonding type?

Yes, will discuss next time

Is bonding important for understanding

materials? Yes, it will determine materials properties


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Metals Copper (used for over 7,000 years initially as tools

and now as cables and heat conductors)

Gold (used for over 7,000 years as jewelry, coins,and now cables and heat conductors)

Silver (used for over 6,000 years as coins, jewelry,cables, medicine)

Iron (used for over 3,000 years as tools and weapons)

Aluminum (used for over 200 years: cables,rockets, airplanes, cans)

Titanium (used for over 60 years: rockets,

airplanes, marines, armor, consumer, etc)

time

Stone age(tools from stones,

wood, bones)

Bronze age(Copper-tin alloy produced

By melting Cu over fire: it

is harder & stronger thanpure Cu)

3300 BC 1200 BC

Iron age(harder and stronger

than bronze)

? 500,000 BC 20th century

Si age(electronics)

???


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Metals

Iron Gold

Common properties

Mechanical: Strong and tough, but have high density Metals resist brittle fracture by deformation - ductile

Thermal: Could be good thermal conductors (e.g. Cu, Au) Moderate temperature resistance (melting T: Al 660, Ag 900;

Au 1060, Cu 1080, Fe 1540, Ti 1670, and Mo 2625C)

Electrical: Structure has free electrons making metals goodelectrical conductors

Structural: Atoms are located in regularly defined, repeatingpositions - a crystal:


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Metals

Ion cores of2+ charge

Delocalized cloud

of valence electrons

Part of the electrons are delocalized and shared by all the atoms, forming

a cloud or sea of free electrons

Free electrons are responsible for high conductivity of metals

Electron cloud shields positively charged atomic cores from each other

and repulsive forces do not develop during high impact stress, preventive

fractures and making metals ductile (will discuss later)


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Ceramics Sand

Cements (used for over 8,000 years, now

believed that tops of Egyptian pyramids

were cast from cement)

Clays (used for over 25,000 years

for sculpture, pottery, bricks, tiles)

Glass (used for over 5,000 years)

Thermal & electrical insulation

Graphite Mica?X2Y46Z8O20(OH,F)4

in whichXis K, Na, or Ca or less commonly Ba, Rb, or Cs;

Yis Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.;

Zis chiefly Si or Al but also may include Fe3+ or Ti.


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Common properties

Mechanical: Strong, have moderate density

Ceramics bend little before they break - brittle

Thermal: Could have high (AlN) or low (ZrO2) thermal conductivity High temperature stability, chemically resistant

Electrical: Structure has no free electrons thus poor electricalconductivity (used as insulators)

Structural:

Ceramics

Combination of metallic and non-metallic atoms

Many but not all ceramics are crystalline:

SiO2: disordered

(glass) or ordered

(crystal) structure


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Polymers Amber (mineralized resin, used for

over 6,000 years as jewelry)

Latex (used for over 3,000 years byMayan who discovered methods for

treating natural rubber that were not

reproduced until 19th century; modern

use: over 200 years)

Cellulose (wood fiber; used in paper and textiles)

Polystyrene (used since 1931 for a variety of objects as fairly rigid,economical plastic, as a foam it is used in virtually all meat and poultry trays)

Nylon (used since 1939 for fishing line, toothbrush bristles, stockings, trackpants, shorts, swimwear, active wear, windbreakers, bedspread and draperies)

Teflon (used since 1946 for coating on cookware, soil and stain repellantfor fabrics and textiles, chemical industries).

Kevlar (used since 1965 for body armor, bicycles: five times stronger thanthe same weight of steel)
http://upload.wikimedia.org/wikipedia/commons/4/41/Amber.pendants.800pix.050203.jpghttp://upload.wikimedia.org/wikipedia/commons/4/41/Amber.pendants.800pix.050203.jpg


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Common properties

Mechanical: Low density

Can be ductile or brittle Commonly relatively low strength

Thermal: Commonly low thermal conductivity Temperature sensitive

Electrical: Most polymers electrical insulators;

Structural:

Polymers

Long chain molecules with repeating groups

Easy to form into complex shapes

Disordered or semi-crystalline


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Composites

2 or more materials are combined to achieve unique

combination of properties (e.g. rigidity, strength, and

low density)Adobe brick (straw is mixed with mud or clay, an adhesive with strong compressivestrength to achieve smaller and uniform more cracks in the clay, greatly improving the

strength).

Plywood (used for over 5500 years: thin slabs of wood held together by a strong

adhesive, making the structure stronger than just the wood itself)

Carbon/Carbon (used for over 30 years: highly-ordered graphitic carbon fibers embeddedin a carbon matrix to achieve lightweight material with low thermal expansion coefficient,

thus highly resistant to thermal shock, or fracture due to rapid and extreme changes in

temperature)

Carbon/Epoxy (used for over 30 years: highly-ordered graphitic carbon embedded in

epoxy dramatically improve its mechanical properties, including strength and toughness)

Cermet (composite of ceramics and metal: high temperature electronic components,

resistors, capacitors)

McLAREN F1: all Carbon-Carbon

composite car body structure


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Composites

Carbon composite body panels of Porsche 980


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Semiconductorsis the materials that have

1. a completely filled valence band at 0 K

2. a band gap smaller than 2.5 eV.

Silicon (the 2nd most abundant element in the earths crust; used in semiconductor devices, incl.integrated circuits)

Germanium (in 1871 Dmitri Mendeleev predicted it to exist as a missing analogue to Si; the elementwas discovered in 1886; originally used in transistor industry instead of Si; now employed in infrared

spectroscopes and other optical equipment which require extremely sensitive infrared detector)

GaAs(used in diodes incl. light-emitting diodes (LEDs), transistors, integrated circuits (ICs), and analog

devides such as oscillators and amplifiers)

CdTe (used in solar cells, as an infrared optical material for optical windows and lenses)

SiC (used in high temperature high power electronics, as substrates for nitrides growth, in cutting tools,as abrasives, in jewelry)

Bonding similar to ceramics

Mechanical properties similar to ceramics


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material types

From: D. R. Askeland, The Science and Engineering of Materials


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Increase in Strength-to-Density Ratio over time

Committee on Materials Science and Engineering, Solid State Sciences Committee, Board on Physics and Astronomy, Commission on PhysicalSciences, Mathematics, and Resources, and National Materials Advisory Board, Commission on Engineering and Technical Systems, NationalResource Council. (1989). Materials science and engineering for the 1990s: maintaining competitiveness in the age of materials.Washington, DC: National Academy Press. Retrieved September 5, 2006, from http://www.nap.edu/books/0309039282/html/index.html

Increasing sophistication of human manipulation of materials


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Structure-Property-Process

relationship Structure

Atomic / Nano / Micro / Macro

Property Mechanical

Physical (electrical, magnetic, optical, thermal,

elastic, chemical)

Process Material history

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The Periodic Table

mse lecture 1

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