Midterm Review
Chapter 2
Quantum Number:
Principle Quantum Number
n
1,2,3,4,... K,L,M,N,...
Subshells
l
s, p, d, f
Number of Energy States
\(m_{l}\)
1,3,5,7
Spin
\(m_{s}\)
+1/2, -1/2
Example
Electron Configuration
Ground State
Electron configuration of an atom (ground state)
Ion electron configuration
Pauli Exclusion Principle:
Each electron state can hold no more than two electrons, which must have opposite spins.
Bohr model vs. Wave-mechanical model
Primary Bonding
Ionic
Electrons move from element to element
Covalent
Electrons are shared between elements
Metallic
Valence forms an electron cloud, shared by all ion cores
Secondary bonding
Van der Waals
Hydrogen bonding
% ionic character \( = 1 - exp^{{-(0.25)(X_{A} - X_{B})}^2}x100 \)
Example
Chapter 3
Crystalline vs. crystal structure
Unit Cell
Display
Draw: BCC, FCC, BCC (100), FCC (100), FCC (111)
Display
This is a picture of BCC crystal structure
This is a picture of FCC crystal structure
Atomic Packing Factor: APF = \( \large {{volume\ of\ atoms\ in\ a\ unit\ cell} \over {total\ unit\ cell\ volume}}\)
Example
Planar Density: PD = \( \large {{Area\ of\ atoms\ centered\ on\ a\ plane} \over {area\ of\ plane}}\)
Linear Density: LD = \( \large {{Length\ occupied\ by\ atoms\ centered\ on\ a\ direction\ vector} \over {length\ of\ direction\ vector}}\)
Theoretical Density
\( \quad \large {\rho = {n*N_{A}\over V_{uc}A}}\)
Example
Crystal Systems
What are the parameters defining crystal systems?
How many crystal systems are there?
Single Crystal vs. Polycrystalline
Grain Boundary
Anisotropic vs. Isotropic
Why might a specimen with grains that are anisotropic, still have isotropic properties?
Chapter 4
Point Defects
Imperfections
Vacancies
Self-interstitials
Impurities
Substitution
Interstitial
\(N_{v} = N exp^{ \large ({-Q_{v}\over kT})}\)
Composition (Concentration)
Linear Defects
Edge Dislocation
b \(\perp\) to dislocation line
Screw Dislocation
b // to dislocation line
Burgers vector b
Interfacial Defects
Surface atoms are not bonded to the maximum number of nearest neighbors*, and are therefore in a higher energy state than the atoms at interior positions
Grain Boundaries
Grain Size
Line intercept method
Average Grain Diameter
ASTM Method
Grain Size Number
Chapter 5
Diffusion Types
Interdiffusion (impurity diffusion)
Self-diffusion
Vacancy diffusion
Interstitial diffusion
Diffusion flux
\(\quad J = {M \over At}\)
Concentration gradient = \(dC \over dx \)
Fick's first law
\( \quad J = -D {dC \over dx}\)
Driving force: that which compels a reaction to occur
Diffusion factors
Effects on diffusion coefficient, D
Empty adjacent atomic sites
Vacancy vs. interstitical diffusion coefficients
Sufficient Energy
\(D=D_{0}exp^{\large ({-Q_{d} \over RT})} \)
Chapter 6
Three principle ways in which a load may be applied:
Engineering Stress/Strain
True Stress/Strain
\(\sigma = {F \over A_{0}}\)
\(\sigma _{T} = {F \over A_{i}}\)
\(\epsilon = {l_{i} - l_{0} \over l_{0}} = {\Delta l \over l_{0}}\)
\(\epsilon_{T} = ln({l_{i} \over l_{0}})\)
Hooke's Law
\(\sigma = E \epsilon \)
Mechanical Design Properties
Stiffness
Strength
Ductility
Toughness
Hardness
Poisson's Ratio
\(\nu = - \large {{\epsilon _{x} \over \epsilon_{z}} = - {\epsilon_{y} \over \epsilon_{z}}} \)
Proportional Limit
Yield Strength
Tensile Strength
%EL = \( \Large {(} \)\( \large{l_{f} - l_{0} \over l_{0}})\) x 100
%RA = \(\large {({A_{0} - A_{f} \over A_{0}})}\) x 100