Material Science Exam 1

Metals

Strong, ductile

Ceramics

brittle, glassy, elastic, non-conducting

Polymers

soft, ductile, plastics

Hydrogen bonds

O-N-F

Lattice parameter equation for BCC

sqrt(3)*a=4R

Lattice parameter equation for FCC

a = 2R*sqrt(2)

Coordination number

Number of touching atoms

Isotropic

materials with properties independent of direction 

First three planes of BCC

110 200 211

First three planes of FCC

111 200 220

First three planes of Diamond Cubic

111 220 311

BCC reflection rule

when h+k+l = even number

FCC reflection rule

occurs when h,k,l are all even or all odd numbers

HCP reflection rule

doesn’t occur (h+2k) = 3n, 1 odd

Interstitial Defect

extra atom

Substitution alloy

Atoms are subbed in, atomic radius is within 15%

Interstitial Alloy

solute is much smaller than solvent, within 40%

Schottky defect

cation and anion vacancy

Freckel defect

vacancy and interstitial

Burger Vector

the displacement vector that closes the loop of line defect

Interfacial defects

boundaries that separate regions have different crystal structures

Hexagonal crystal system

a=b=|c, 90 90 120

Tetragonal crystal system

a=b=|c, 90 90 90

Scanning electron microscopy

Small electron beam is scanned repeatedly over the surface area. Variations change strength of beam. Magnification is limited by beam size.

Diffusion flux

How fast diffusion occurs

Elastic stress/strain

reversible

Plastic stress/strain

non-reversible

Tensile strength

max stress on stress-strain curve

Brittle material

Has very little elastic deformation before cracking

Ductile

deforms more before fracture

Toughness

Equal to area under stress-strain curve up to the point of fracture. Same measurement as modulus of resilience

Slip direction and burgers vector

In the same direction

Isotropic-Anisotropic

Anisotropy can be caused by stretching an isotropic material

n-type semiconductor

Doped with elements having more valance electrons then the base material

p-type semiconductor

Doped with elements having less valance electrons then the base material