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15 Cards in this Set

  • Front
  • Back
Electronic materials are classified according to _________.
conductivity
Metals
Semiconductors
Insulators
properties controlled by energies and shapes of orbitals, particularly band gap
band gap
separation b/w valence band and conduction band

small amt of energy needed to move e- from VB to CB
semiconductor types:
intrinsic
doping: n-type, p-type
pure-silica (4 e-)

negative-replace some w/ phosphorus (5 e- makes excess)

positive-replace some w/ aluminum (3 e- makes deficiency)
superconductors
transmit electricity w/o resistance--materials become superconducting at low temperatures
band gap energies for semiconductors, insulators
~50-300 kJ/mol
< 350 kJ/mol
types of insulators
ionic solids, complex network solids, organic cpds
ceramics--inorganic ionic solids
ceramics--types
oxides (oxygen and metals)
carbides (carbon and metals)
nitrides (nitrogen and metals)
silicates (silica with metal oxides)
aluminates
ceramics--properties
hard, brittle
resistant to heat, corrosion, wear, do not deform under stress, less dense than metals
semiconductors--types
silicon, germanium, carbon in graphite form
inorganic cpds with valence electron count of four
bonding is covalent-network, ionic, or combination
plastics
thermoplastic
termosetting plastic
elastomer
materials that can be formed into various shapes

can be reshaped

shaped through irreversible chemical processes

exhibits rubbery or elastic behavior
making polymers:

addition polymerization

condensation
coupling of monomers through their pi bonds

elimination of small molecule like water
crystallinity
cross-linking
vulcanization
degree of ordering in polymer

forming bonds b/w chains--stiffens

adding sulfur to natural rubber cross-links chains together
making ceramics
sol-gel process forms fine particles of uniform size
materials for optics

liquid crystals
intermediate liquid crystalline phase-classifications
nematic-one dimensional ordering along long axis

smectic-two-dimensional ordering along long axes and in layers (ends line up)

cholesteric-aligned along long axes but in flat planes rotated at different angles for a screwlike spiral (changes in temp and pressure change the order and hence the color)