Thermal properties by bonding 1.Heat capacity and melting point Hooke'slaw:F=kc,k↑mlf↑ Ceramics:strong bonds and light atoms.For small x,f is big.high Cp and Tm. 2.Thermal expansion Deep and narrow well in ceramics:small expansion 3.Heat conduction Spring network 义 Phonon:wave travel at the speed of sound.The result of particle vibrations,T↑(<400℃)，f↑A↑ 必 Phonon scatter:porous,amorphous↑，simple↓ Photon:absorption and emission of photon at the speed of light. Especially important in transparent and porous materials 必 Electron
Thermal properties by bonding 1. Heat capacity and melting point Hooke's law: F=kx, k↑ m ↓f ↑ Ceramics : strong bonds and light atoms. For small x, f is big. high Cp and Tm. 2. Thermal expansion Deep and narrow well in ceramics: small expansion 3. Heat conduction Spring network Phonon: wave travel at the speed of sound. The result of particle vibrations, T ↑(<400 ℃), f ↑ A↑ Phonon scatter: porous, amorphous ↑, simple ↓ Photon: absorption and emission of photon at the speed of light. Especially important in transparent and porous materials Electron
Application example *Exterior:high purity amorphous silica fibers. highest temperatures zone:added layer of high- emittance glass.tolerate temperatures up to 1480 C for short time. 955° 315° 650° Temperatures are ir maximum 1465° Celsius degrees. Temps marked witl 1480 exposure an signify ascent temperature temperatures. Temp *1175° (C) 料25° 980° 660 T(Aluminum) mp *430° *405° *420° 175 0.0 3.5 Tile Thickness (in)
Application example Exterior: high purity amorphous silica fibers. highest temperatures zone: added layer of highemittance glass. tolerate temperatures up to 1480 ℃ for short time. 955 1175 430 405 425 420 980 1465 650 315 T emperatures are in Celsius degrees. T emps marked with an * signify ascent temperatures. * * * * * maximum exposure temperature 1480 Temp ( C) 660 175 0.0 Tile Thickness 3.5 T (Aluminum) mp (in)
Electrical behavior insulators semiconductors metals 10 20 1016 10 -12 108 104 100 109 108 eorlis pesnp C35T5 wnjuewIe Ieddos Conductivity (ohm cm-1 -1
Electrical behavior
Electrical behavior Energy band Keug Energy band gap Energy band Interatomic Equilibrium separation interatomic spacing Energy band, band gap Valence band, 9899989899898 0江 conduction ◆ Metals Semiconductors band E Insulators
Electrical behavior Energy band, band gap Valence band, conduction band E Metals Semiconductors Insulators
metallic conductors:many partially and fully unoccupied levels with similar energies.large number of mobile charge carriers &Semiconductors:T↑，e→conduction band,move and conduct electricity.band gap↓e↑↑conduction band. *Insulators:no e -conduction band Superconductors:Tc,Ic,Bc *Ion conductor,electric insulator -fuel cells nonsuperconductors Electrical Resistivity ◆-superconductdrs Tc Temperature (K)
metallic conductors: many partially and fully unoccupied levels with similar energies. large number of mobile charge carriers Semiconductors: T ↑, e → conduction band, move and conduct electricity. band gap ↓e ↑↑conduction band. Insulators: no e → conduction band Superconductors: Tc, Ic, Bc Ion conductor, electric insulator → fuel cells T emperature (K) T c superconductors nonsuperconductors Electrical Resistivity