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What is Materials Science and Engineering?
Structure (Composition)
Properties
PerformanceProcessing
What are the fundamental relationships between the apices ofthe "MSE tetrahedron" AND how can we exploit them to
"build a better mousetrap"?
What is Materials Science and Engineering?
Structure (Composition)
Properties
Performance
Processing
How do you make a material?How do you make a material?How do you make it in a specific shape?How do you make it do what you want?
How do you get the structure you want?How do you get the structure you want?Every material has a hierarchy of structural levels.How do you characterize these?
Why do materials have the properties they do?Why do materials have the properties they do?How can you exploit these?How do you ensure these get transferred to technologies?
How to ensure that materials don’t limit technology?How to ensure that materials don’t limit technology? How long do materials last?How do materials fail?
You Have 20 Seconds!!!
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Webster’s Definition:The elements or substance or the parts of
which something is composed or can be made
“Solid Stuff”
Chem ical Material
G as
S o lid s M eta ls C eram ics P o lym ers C om p os ites
Solids Liquid
Stone Age3300BC – 2000BCStarted shaping stone to use as tools and
weaponsBronze Age
3300BC – 1100BCBegan to use metals
Smelt it to form weapons and tools
Iron Age 1300BC - 500ADBegan forging Iron and Steel
What age are we in now??????
1.State
2.Magnetism
3.Density
4.Viscosity
Solid, liquid or gas
Physical attraction for iron
Mass per unit volume (d = m/v)
Resistance of a material to flow. ***Can change with temperature
1. Malleability
2. Ductility
3. Strength4. Tensile
Strength
5. Hardness
6. Toughness
Ability to be reshaped in all directions without failure.
Ability of a material to be stretched
Ability to stand up to a force without bending or breaking.
Maximum tension that material can absorb before snapping
Resistance to being permanently deformed or bent***Brinell Scale (http://en.wikipedia.org/wiki/Brinell_scale )
Shock resistance……how it responds to sudden blows.
7. Brittleness
8. Elasticity
Absence of ductility or failure by sudden fracture
Ability to absorb a force and flex in different directions, returning to its original position once force is removed.
1. Conductivity
2. Resistivity
Measure of how easily a material allows an electrical current to flow through it
Opposite of conductivity. The measure of a materials resistance to the flow of electricity.
1. Toxicity
2. Corrosion Resistance
3. Combustibility
Ability to damage living tissue through contact, inhalation, ingestion, or injection.
A material's ability to resist deterioration caused by exposure to an environment
How easily a material will catch fire and burn
Thermal Expansion
Thermal Conductivity
Melting point
Glass transition temperature
The extent to which a material will expand or contract
Measure of the rate at which heat will flow through a material.
Temperature at which a solid starts to turn into a liquid
Point at which a polymer or glass changes from a rigid solid to a viscous fluid.
Notebook Entry 1:
1.Name 3 metals
2. List two things each metal is used for.
3. List a few properties of that metal that make it a good choice for the job.
METALS and ALLOYS
Examples include:
Steel
Aluminum
Cast Iron
Titanium
Copper
Characteristics of Metals
1. Good electrical conductors* Allow electricity to flow through easily
2. Good thermal energy conductor.* Allow heat energy to pass through easily
3. High strength**the resistance to fracture of a material when stressed
4. High stiffness* the material's ability to resist elastic deformation
5. Ductile* have the ability to be drawn into thin, cohesive strands
(wires)6. Malleable
* can be flattened (hammered or rolled) into thin sheets.
Metals continued…..
Alloy – combination of two metals* Usually more desirable characteristics than the parent metals
Downside of metals:1. Usually react with oxygen (oxidizes……rusts)2. Higher densities3. Strength weakened as it is heated.
Where do metals come from?
Native metals – found as pure metals in nature.ex. Gold, Silver, and Copper . (only)
Ore – type of rock that contains important elements like metals.** Must be mined and then have the metal extracted.
Iron Ore
Lead Ore
How to get the metal out of the rock??????
1. Smelting – the use of heat and a chemical reducing agent to decompose the ore and drive off elements as gasses or slag and leaving just the metal behind.
Silicon Smelting…Silicon does not exist on its own in nature. Most of it is bound with oxygen in materials like sand and quartzite and granite rock. The silicon-oxygen bond in quartz is so stable it can only be broken by white heat!
Silicon producers reduce high-grade quartz sand to elemental silicon via a carbo-thermic smelting process:
Bonding
4 types:a. Metallicb. Ionicc. Covalentd. Intermolecular forces
Metallic Bonding:
Metallic bond is the reaction between molecules within metals called alkali reactive force. It involves the sharing of free electrons among a lattice of metal atoms.
Ionic Bonding:
An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions
Giving and taking of electrons……
Covalent Bond:
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms.
Intermolecular Forces:
Intermolecular forces are the forces of attractions that exist between molecules in a compound
Type of bonding
Metallic Ionic Covalent Intermolecular
Type of elements involved
Givers &/or takers
of electrons
Description
Type of material formed
Strength of bond
PropertiesProduced
Types of Bonding
Type of bonding
metallic ionic covalent intermolecular forces
Type of elements involved
between metals between metals and nonmetals
between nonmetals
between molecules
Givers &/or takers
of electrons
between givers between givers and takers
between takers
Description e- roam freely between many
atoms (delocalized).
Sea of e- surrounding (+) kernels.
Transfer e- Makes (+) and (-) ions that are
attracted to each other.
Share e- Forms discrete
molecules.
Hold covalently bonded
molecules together as a
solid.
Type of material formed
solid metallic elements and
alloys
ceramics and glass
polymers and some
ceramics/glasses
helps form solid polymers
Strength of bond relatively strong very strong very strong weak
PropertiesProduced
good conductors, workable,
corrode easily, generally high melt temps but
variable
brittle, high melt temps, nonconductors
as solids, don’t corrode
insulators, don’t corrode
Help determine a lot of properties
of covalent compounds (polymers).
soft and plastic
Types of Bonding
Crystalline Structure:
The particular repeating arrangement of atoms ( molecules or ions) throughout a material.
Unit Cell:
The smallest structure that is repeated over and over again in a crystalline material
Unit Cell
Crystal structure
Amorphous Having no long range crystalline pattern or structure
Amorphous Crystalline
Types of Amorphous materials:
GlassGel
Thin Films
Nanostructures
Unit Cell Definitions
Lattice – the regular repetitive, grid-like pattern of atoms in a material.
Lattice Point - A point at the intersection of two or more grid lines
Coordination Number – the number of atoms touching a particular atom, or the number of nearest neighbors.
Example of LatticesLattice Point
Determining number of atoms in a Unit Cell
The figure at the right shows the face-centered cubic unit cell of a cubic-close packed lattice.How many atoms are contained in a unit cell? Each corner atom is shared with eight adjacent unit cells and so a single unit cell can claim only 1/8 of each of the eight corner atoms. Similarly, each of the six atoms centered on a face is only half-owned by the cell. The grand total is then (8 × 1/8) + (6 × ½) = 4 atoms per unit cell.
Determining number of atoms in a Unit Cell
Corners = 1/8 point
Body Centered = 1 point
Face Centered = ½ point
1
Types of Unit Cells:
Simple Cubic
The simple cubic unit cell is a cube (all sides of the same length and all face perpendicular to each other) with an atom at each corner of the unit cell
# of atoms per cell = 1Coordination number = 6
Ex. Pyrite (Fool’s Gold)
Body Centered Cubic (BCC)
The body-centered cubic unit cell is a cube (all sides of the same length and all face perpendicular to each other) with an atom at each corner of the unit cell and an atom in the center of the unit cell.
# of atoms per cell = 2Coordination number = 8
Face Centered Cubic (FCC)
The face-centered cubic unit cell is a cube (all sides of the same length and all face perpendicular to each other) with an atom at each corner of the unit cell and an atom situated in the middle of each face of the unit cell.
# of atoms per cell = 4Coordination number = 12
Hexagonal Close Packed Structure ( HCP)
The HCP crystal structure is created when atoms of neighboring layers “nest” in the crevices of the layer below them. This nesting creates a crystal that is tightly packed and has few slip planes.
Coordination number = 12Number of atoms = 6
Three spheres are completely contained (100%);two spheres are 50% contained12 spheres are 1/6 contained.
HCPHexagonal Close Pack
HCP is more tightly packed….more space efficient
Review…….
Coordination number?
Number of nearest neighbors (12)
Type of unit cell?
Face centered cubic (fcc)
Number of atoms in this unit cell?
1/8 x 8 = 1½ x 6 = 3
Total = 4
Review……2
1. What type of crystal structure has the tightest packing?
2. What type of bond is this
HCP
3. What type of bond is the weakest? Inter-molecular
4. In a crystal, a point of intersection is called a ….
Lattice point
Review……..3
1. What type of bonding occurs in ceramics?2. What type of elements use a metallic bond to stick
together?3. Give two properties of elements that form using ionic
bonds4. What word describes a solid with no real crystal pattern?5. What type of material is mostly non-crystalline and held
together with covalent bonds? 6. What is the name of the regular repetitive, grid-like pattern
of atoms in a material?
ionicmetals
BrittleHigh melting tempsNon conductorsDon’t corrode
amorphous
polymerlattice
Name that crystal structure……
Zinc Sulfide (ZnS)
Zinc
Galena - (Lead (II) Sulfide)
Silver (I) Flouride (AgF)
Crystal Defects
Materials rarely consist of a single perfect crystal formed of one type of atom. The majority of engineering materials are alloys. An alloy is a mixture of atoms of more than one element. Even ‘pure’ metals are rarely more than 99.9% pure.
2 Types * Point Defects - localized imperfections in crystals * Linear Defects - when a crystal structure contains misaligned planes of atoms
Types of Point Defects
1.Vacancyformed when atoms are missing
from the lattice, leaving a hole
2. Substitutional Impurity
** one of the atoms in the lattice is replaced by an outside element.
***The substitute or impurity atom is often larger than the atoms of the host material. This means there are strains imposed on the lattice.
Point Defects cont..
3. Interstitials
** atoms that are squeezed in between regular lattice sites.
Point Defects cont……..
A. Self-Interstitial – an atom of the same type as the lattice is squeezed in.
B. Interstitial Impurity – a foreign (usually smaller) atom fills in the gaps.
Metals Ceramics/Glass
Polymers
Type of Matter
Type of Elements
Type of Structure
Type of Bonding
Element or mixture
Metallic elements
Crystalline
Metallic bonding
Compounds or mixtures of compounds
Metals/semi metals with nonmetals
Ceramics= crystallineGlass = amorphous
Mostly Ionic Bonding
Mostly compounds
Nonmetals
Mostly amorphous
Covalent bonding & weak intermolecular
CeramicsA ceramic is an inorganic, nonmetallic prepared by the action of heat and subsequent cooling.
Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous.
Examples include: brick, glass, tableware, refractories, and abrasives
Properties: 1. Strong 2. Hard 3. Stiff 4. Brittle 5. Poor conductor of heat and electricity
Crystalline - the atoms or molecules are arranged in a regular, periodic manner
Amorphous – no crystalline pattern…. The molecules then have a disordered arrangement
