-
amorphous
- No long range order
- Possible short range order
- not periodic
-
crystalline
- long range order
- position repeated over and over
-
Atomic packing factor
- vol of atoms in cell / cell volume
- n*4/3*pi*R^3/a^3
- n= number or atoms in unit cell
- relate a and R to solve using geometry bases on sc,bcc, or fcc
-
superstitual impurity
lattice site taken up by another element
-
vacancy
lattice site missing atom
-
self interstitual
same element not on a lattice site
-
impurity interstitual
another element not on a lattice site
-
two dislocations or line defects?
edge and screw dislocations
-
4 point defects?
- vacancy
- self interstitual
- impurity interstitual
- superstitual impurity
-
coordination #
- number of nearest neighbors
- bcc = 6
- bcc = 8
- fcc = 12
-
Theoretical density
- P = (n*A)/(Vc*Na)
- n = number of atoms/cell
- A= atomic weight
- Vc = a^3 = volume of unit cell
- Na = avagadros number
-
rank densities of materials in general
- metal
- ceramics
- polymers, composites
-
isotropic
- uniform crystal structure
- equiaxed
-
Anisotropic
- crystal structure not uniform in all directions
- lenticular and irregulararly oriented
-
Polymorph
single element material changes its structure as a function of temp
-
alatroph
when a compound changes its structure as a function of temp
-
Planar density
# of atoms centered on a plane / area of plane
-
Linear density
# of atoms centered on direction vector/ length of dir. vector
-
equixed
- uniform grain boundries
- strong
-
lenticular/columnar
- elongated grain boundries
- not as strong as equiaxed
-
Intrinsic
Natural property of material
-
extrinsic
man controlled property
-
Quantum numbers
- n = energy shell level (1 2 3 4..)
- l = orbitals (s p d f)
- Ml = magnetic or number of electrons in orbital*2 (1 3 5 7)
- Ms = spin (+-1/2)
-
Bond energy
En = Er + Ea = -A/r + B/rn
-
ionic covalent mixed bonding equation
1 - (e^((Xa-Xb)^2/4))*100%
- Xa and Xb are elements electronegativity
- only good for mixtures of two elements
-
primary bonding
matallic, ionic and covalent
-
secondary bonding
dipole - dipole or vand er waals
-
metallic bonding
material shares/ floats electrons as a whole. barely covered...
-
covalent bonding
sharing electrons
-
ionic
giving and recieving electrons creating charged atoms that then are attracted to eachother.
-
alpha
coefficient of thermal expansion
-
-
-
ceramic
- large E0
- large Tm
- small alpha
- brittle, glassy
- non conductors
-
metals
- moderate Tm
- moderate E0
- moderate alpha
- high thermal and electrical conductivity
- strong ductile
-
polymers
- small E0
- small Tm
- large alpha
- soft, ductile
- thermal and electrical insulators
-
Solidification
Result of casting of molten material
-
Equilibrium concentration of point defects
Nv/N = e^(-Qv/kT)
- Nv = no of defects
- N = no of potential defect sites
- Qv = activation energy
- k = boldamins constant
- T =temperature
-
substitutional solid solution conditions
- atmoic radius difference less than 15%
- proximity in periodic table/similar electro neg
- same crystal structure for pure metals
- Valancey - a metal will be more likely to disolve element of higher valancey than lower.
-
edge dislocation
- extra partial plane of atoms inserted in crystal structure
- perpindicular to dislocation line
-
screw dislocation
- spiral planar ramp
- due to shear deformation
- parallel to dislocation line
-
single crystal
material with no grain boundries
-
polycrystal
- multiple crystal structures in material
- multiple grain boundries
-
grain boundry properties
- high diffusion
- high mobility
- high chemical reactivity
-
cold mount
- cheap
- can see sample
- take a supstaintial amount of time to harden
-
-
hardness
- materials resistance to plastic deformation
- intrinsic property
-
solute and solvent roles
- solute dissolved into solvent
- solvent is larger quantity
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