1、Fundamental of Materials Science and Engineering Introduction u Chapter 1 Atomic Bondingu Chapter 2 Crystal Structuresu Chapter 3 Defectsu Chapter 4 Glass structureu Chapter 5 Phase diagramu Chapter 6 Processingu Chapter 7 Formingu Chapter 8 Sinteringu Chapter 9 Mechanical propertiesu Chapter 10 The
2、rmal propertiesu Chapter 11 Electrical propertiesu Chapter 12 Optical properties-2-References:1.William F.Smith&Javad Hashemi:Foundations of Materials Science and Engineering2.William D.Callister,Jr.:Materials Science and Engineering:An introduction(本科生专业外语教材)Chapter 1:Atomic Bonding1.1 Atomic struc
3、tures electronNucleus-Atom consists of a nucleus(positive charged)and electrons(negative charged)-Electrons are characterized by four quantum numbersPrinciple quantum number:n=1,2,.K,L,M,N,O,Orbital quantum number:l=0,1,n-1s,p,d,fMagnetic quantum number:m=l,.,1,0,-1,-l Spin quantum number:s:1/2 and-
4、1/2 -3-n:determines the position of the shell.l:determines the shape of orbitals or subshells in each shell.m:represents the orientation/number of the orbitals within each shell.s:represents the direction of spin.lmnumber of orbitals0,s011,p+1，0，-132,d+2，+1，0，-1，-253,f+3，+2，+1,0,-1,-2,-37Pauli exclu
5、sion principle:no electron can have the same set of four quantum numbers-4-nlm#of orbitalMaximum#of electrons10011s20101,0,-1132s2p3201201,0,-12,1,0,-1,-21353s3p3d262610818Electron#in each shell:2n2-5-Relative energy level of orbitals6s5p4d5s4p3d4s3p3s2p2s1sEnergyEach orbitalconsists of 2 electrons.
6、-6-Electrons fill the orbitals with lowest energy first.Examples(electronic structure notation):H(1):1s1B(5):1s22s22p1C(6):1s22s22p2N(7):1s22s22p3O(8):1s22s22p4Na(11):1s22s22p63s1Mg(12):1s22s22p63s2Al(13):1s22s22p63s23p1Si(14):1s22s22p63s23p2Cl(17):1s22s22p63s23p5Fe(26):1s22s22p63s23p63d64s2Only tho
7、se electrons which occupy the outermost shell will involve in chemical reaction;called valence electrons.-7-1.2 Bonding-Metallic bondingThe valence electrons are freely shared by all theatoms in the structureElectrons repulse each other keep atoms in certain distanceElectron and nuclei attract each
8、other bondingCharacters:Close-packed structures in pure metalsDuctilityHigh electric and thermal conductivity Shiny-8-Ionic bondingAtom gives up one or more electrons positive charge(Cation)Atom accepts one or more electrons negative charge(Anion)Coulombic attraction force source of ionic bondingE.g
9、.:NaCl Na(11):1s22s22p63s1Cl(17):1s22s22p63s23p5For pure ionic bonding,it would be nondirectionalclose-packed.-9-The packing pattern of ionic bonding structures:determined by(i)electrical neutrality(ii)sizes of ionsCoordination number(CN):the number of nearest neighbor atoms/ions surrounding an atom
10、/ion Not stableStableDetermined by the ratio of radius of ions-10-The packing tends to have as more CN as possible2(C+A)2=(2A)2+(2A)2(C+A)2=2A2(C+A)/A=21/2=1.414 C/A=0.414Example:NaCl:R+=1.02;R-=1.81;R+/R-=1.02/1.81=0.564 CN=6MgO:R+=0.72;R-=1.40;R+/R-=0.72/1.40=0.514 CN=6SiO2:R+=0.40;R-=1.40;R+/R-=0
11、.40/1.40=0.286 CN=4-11-Covalent bondingTwo or more atoms share electrons such that each achieves a stable structureUnlike metallic and ionic bonding,covalent bonding is directional due to shape of orbitalDirectionalNot close-packedsp3 hybrid orbital:one s orbital and 3 p orbitals are mixed together
12、to form four new orbitals.Each orbital points to one corner of tetrahedral and form angle of 109.5o between them.HybridizationpsC,N,O,Cl-12-sp2 hybrid orbital:one s orbital and 2 p orbitals are mixed together to form three new orbitals.The remaining p orbital is unaffected.Three sp2 orbitals are on
13、the same plane and form angle of 120o between each other.The unaffected p orbital perpendicular to the plane pssp1 hybrid orbital:one s orbital and one p orbitals are mixed together to form two new orbitals.The remaining two p orbitals are unaffected.Two sp1 orbitals are on the same line and form an
14、gle of 180o between them.ps-13-Bonding strength/forcenm-14-The first term is attractive,and the second is repulsive.At r ro,the equilibrium value,the repulsive force dominates and U rises.The force F is given by the rate of change of energy with distance dU/dr and is zero at r=ro.-Ionic and covalent bond combinationCaSO4O(8):1s22s22p4S(16):1s22s22p63s23p4Ca(20):1s22s22p63s23p64s2Forming covalent bond between:S and O Forming ionic bond between SO4 and Ca-15-Van der Waals BondingWeaker bond other than metallic,ionic and covalent bondsMolecular polarizationHCl-16-+-
