Exam 1
T - The percent ionic character in Ca F2 is dependant on electronegativites of F an Ca
T - Single walled carbon nanotubes are much stronger than conventional carbon fibers
F - Polymers with higher molecular weight tend to have lower melting temperatures
F - Linear density along [101] is less than along [010] in FCC crystal structure
F - The atomic packing factor of HCP and FCC are not equal
T - Planar density of (101) is greater than (010) in the BCC crystal structure
F – The elastic modulus of a material is proportional to the slope of the repulsive force
Versus the distance evaluated at equilibrium seperation
F- deep energy well is consistent with low elastic modulus, low melt temp, and high exp coeff
T- crystalline order is ceramic materials is determined by both the radius ratio and ion sizes of valence
F- All polymers crystallize in the same crystal structure
Exam 2
Strengthen Materials
Grain size is reduced, grain boundaries block dislocations, each dislocation effects small vol of metal
Cold work increases the density of vacancies and line defects, dislocations block dislocations
Precipitation Hardening- disperses small uniform particles that precipitate from supersaturated solutions
Solid Solutions – Lattice strain field interactions between dislocations and dislocation movement is restricted
Factors Influence Tensile and Yeild Strentgth
Molecular weight- mol weight up, mol entanglements increase and crystallinity
Degree of Crystallinity- increase crystallinity molecules become more tied together
Deformation by drawing Alligns crystalline region perpendicular to draw direction and increse crystallinity
Heat Treating – leads to increase in size, increse in perfection and increase in % crystallinity
Hume Rothery Rules 1) atomic radius diff<15% 2) similar electronegativity 3) same FCC BCC 4)similar valence
Exam 3
T – congruent melting point is a point (or temp) at which the composition of liquid and solid are the same
F – binary phase diagram the progession of phases along an isoterm is 1-2-2-1-1-2-2-1
F – An example of a peritetic reaction in Fe-FeC3 system is upon cooling tranforems to cementite (fe3C)
TF – Hot working metals can only be achieved above the glass transition temperature
T – Resilience is recoverable energy
T – Tensile strength of a polymer increase with its number average molecular weight
F – Modulus and strength of a ceramic material increase as its porosity increase
F – In a binary system an invariant reaction always involves three phases
T – the yield strength of Cu decreases as its grain size increases
T – Cold working or strain hardening increases the vacancies and line defects
T – As the hardness of an alloy increases the yield strength and tensile strengths increase
Chapter 12
V = Voltage volts
I = Current Amps
R = resistance ohms
P = Electrical Resistivity (ohm-m)
l= distance between points m
A= cross sectional area m
= electrical conductivity 1/(ohm-m)
J= Current Density
= Electric Field intensity
= Electron Drifit velocity
= electron mobility constant
n= number of free electrons
|e| = 1.6 E -19
Impurity Resistivity Contribution Electrical Conductivity fore an intrinsic semiconductor
Impurity concentration at%
Volume fractions
Individual resistivities N-type extrinsic Semiconductor