MSE 250 EXAM WITH COMPLETE SOLUTIONS 100% VERIFIED
ionic bonding - ANSWER btw metallic and nonmetallic
non-directional
dissimilar en's
requires valence electron transfer
high bonding energies
high melting points
low conductivities
spatial distribution of atoms is detrermined through geometric arrangement of ions only
(lattice, crystal structure)
covalent bonding - ANSWER small diff in en
shared e's
directional bonding
nonmetallic elements or molecules
bonding energies range
magnitude of ionic bond character formula - ANSWER %IC = { 1-exp[-.25(Xa-Xb)^2] } x
100
crystal structure in ceramics - ANSWER spatial distribution of atoms is detrermined
through geometric arrangement of ions only (lattice, crystal structure)
atomic radii affects ionic radius and electric charge
more stable to surround cation with max # anions
must maintain charge neutrality (reflected in chem. formula AmXp)
,<0.155 - ANSWER CN = 2
0.155 - 0.225 - ANSWER CN = 3
0.225 - 0.414 - ANSWER CN = 4
0.414 - 0.732 - ANSWER CN = 6
0.732 -1 - ANSWER CN = 8
octahedral sites CN - ANSWER CN = 6
tetrahedral sites CN - ANSWER CN =4
FCC sites number - ANSWER 4 octahedral
8 tetrahedral
cubic sites CN - ANSWER CN = 8
Rock Salt Crystal Structure - ANSWER CN = 6
Zincblende CS - ANSWER CN = 4
every other tetrahedral site filled
Fluorite CS - ANSWER CN = 8
cation in every second interstitial
, density computation - ANSWER n' = number of formula units within the unit cell
sums of atomic weights of all cat/anions
Vcell = unit cell vol.
Na = avogadro's number
Avogadro's number - ANSWER 6.02 x 10^23
Cesium Chloride CS - ANSWER CN = 8
how to improve creep resistance - ANSWER increase grain size
choose mat. w/higher Tm
precipitation hardening
Schottky defect - ANSWER cation vacancy and anion vacancy
Frenkel defect - ANSWER a cation vacancy-cation interstitial pair
k - ANSWER Boltzman's constant
1.38E-23
Cesium Chloride CS - ANSWER CN = 8
equal number cat and anions
gamma - ANSWER = deltaX/Y = tan(theta)
nu - ANSWER Poisson's ratio
v = -ex/ez
ionic bonding - ANSWER btw metallic and nonmetallic
non-directional
dissimilar en's
requires valence electron transfer
high bonding energies
high melting points
low conductivities
spatial distribution of atoms is detrermined through geometric arrangement of ions only
(lattice, crystal structure)
covalent bonding - ANSWER small diff in en
shared e's
directional bonding
nonmetallic elements or molecules
bonding energies range
magnitude of ionic bond character formula - ANSWER %IC = { 1-exp[-.25(Xa-Xb)^2] } x
100
crystal structure in ceramics - ANSWER spatial distribution of atoms is detrermined
through geometric arrangement of ions only (lattice, crystal structure)
atomic radii affects ionic radius and electric charge
more stable to surround cation with max # anions
must maintain charge neutrality (reflected in chem. formula AmXp)
,<0.155 - ANSWER CN = 2
0.155 - 0.225 - ANSWER CN = 3
0.225 - 0.414 - ANSWER CN = 4
0.414 - 0.732 - ANSWER CN = 6
0.732 -1 - ANSWER CN = 8
octahedral sites CN - ANSWER CN = 6
tetrahedral sites CN - ANSWER CN =4
FCC sites number - ANSWER 4 octahedral
8 tetrahedral
cubic sites CN - ANSWER CN = 8
Rock Salt Crystal Structure - ANSWER CN = 6
Zincblende CS - ANSWER CN = 4
every other tetrahedral site filled
Fluorite CS - ANSWER CN = 8
cation in every second interstitial
, density computation - ANSWER n' = number of formula units within the unit cell
sums of atomic weights of all cat/anions
Vcell = unit cell vol.
Na = avogadro's number
Avogadro's number - ANSWER 6.02 x 10^23
Cesium Chloride CS - ANSWER CN = 8
how to improve creep resistance - ANSWER increase grain size
choose mat. w/higher Tm
precipitation hardening
Schottky defect - ANSWER cation vacancy and anion vacancy
Frenkel defect - ANSWER a cation vacancy-cation interstitial pair
k - ANSWER Boltzman's constant
1.38E-23
Cesium Chloride CS - ANSWER CN = 8
equal number cat and anions
gamma - ANSWER = deltaX/Y = tan(theta)
nu - ANSWER Poisson's ratio
v = -ex/ez
