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C O U R S E 
Materials Science: 10 Things Every Engineer Should Know
James Shackelford, University of California, Irvine
C O U R S E   L E C T U R E 
The Six Categories of Engineering Materials
Notes taken on January 8, 2016 by Edward Tanguay
six categories of engineering materials
nearly all materials used for modern applications come from these six categories
1. metals
metallic bond
adjacent atoms share electrons in a non-directional way
metal pan
can't see through it
electrons that provide the metallic bonding are reflecting any proton light rays from the environment
gives us the characteristic shiny luster
can conduct electricity, since bonding electrons are mobile
power cord
metal is providing the conductivity
polymer sheathing that is providing the safety and insulation
2. polymers
covalent bond
directional bond
electron sharing between adjacent atoms
have a stable balance
plastic spatula
good structural integrity
carbon-to-hydrogen bonding
electrons are being shared by the two adjacent atoms
electrons are thus spoken for, good insulator
3. ceramics
ionic bond
non-directional bond
electron sharing from one atom to another
involves the electrostatic attraction between oppositely charged ions
atoms that have lost one or more electrons (known as cations) and atoms that have gained one or more electrons (known as anions)
from a metallic cation to a negative anion, very often oxygen
Coulombic forces
the magnitude of the electrostatic force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distance between them
common ceramic coffee mug
electrons are spoken for, therefore electrical insulating
first three categories are based on the three different kind of electron bonding: metallic, covalent, and ionic
4. glass
a subset of ceramics
the key distinction between the ceramic and glass
glass: random atomic arrangement of ions
ceramic: crystalline formation
common drinking glass
optically transparent
because of the nature of the ionic bonding
silicon ions and oxygen ions, a common silicate material
5. fiberglass
best of both worlds
the ductility of a polymer
ductility: when a solid material stretches under tensile stress
like the plastic spatula
harder structure
from microscopic glass fibers
a few microns in diameter
stacking chairs
6. semiconductors
small piece of silicon
microscopic and submicroscopic
can control the conductivity in a very powerful way