材料科学专业英语课件

1、Fundamental of Materials Science and Engineering Fundamental of Materials ScienIntroduction Chapter 1 Atomic Bonding Chapter 2 Crystal Structures Chapter 3 Defects Chapter 4 Glass structure Chapter 5 Phase diagram Chapter 6 Processing Chapter 7 Forming Chapter 8 Sintering Chapter 9 Mechanical proper

2、ties Chapter 10 Thermal properties Chapter 11 Electrical properties Chapter 12 Optical properties-2-References:William F. Smith & Javad Hashemi: Foundations of Materials Science and EngineeringWilliam D. Callister, Jr.: Materials Science and Engineering: An introduction(本科生专业外语教材)Introduction Chapte

3、r 1 AtomicChapter 1: Atomic Bonding1.1 Atomic structures 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,

4、d, fMagnetic quantum number: m = l, ., 1, 0, -1, -l Spin quantum number: s:1/2 and -1/2 -3-Chapter 1: Atomic Bonding1.1 An: 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: r

5、epresents 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 exclusion principle: no electron can have the same set of four quantum numbers-4-n: determines the position of nlm# of orbitalMaximum # of electrons10011s20101, 0, -1132s2p3201201, 0

6、, -12, 1, 0, -1, -21353s3p3d262610818Electron # in each shell: 2n2-5-nlm# of orbitalMaximum # 10011Relative energy level of orbitals6s5p4d5s4p3d4s3p3s2p2s1sEnergyEach orbitalconsists of 2 electrons.-6-Electrons fill the orbitals with lowest energy first.Relative energy level of orbitExamples (electr

7、onic 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 those electrons which occupy the outermost shell will involve in

8、 chemical reaction; called valence electrons.-7-Examples (electronic structure1.2 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 other bondingCharacters: Clos

9、e-packed structures in pure metalsDuctilityHigh electric and thermal conductivity Shiny-8-1.2 Bonding- Metallic bondingT- 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 bond

10、ingE.g.: NaCl Na(11):1s22s22p63s1Cl(17):1s22s22p63s23p5For pure ionic bonding, it would be nondirectionalclose-packed.-9- Ionic bondingAtom gives up oThe packing pattern of ionic bonding structures:determined by (i) electrical neutrality(ii) sizes of ionsCoordination number (CN): the number of neare

11、st neighbor atoms/ions surrounding an atom/ion Not stableStableDetermined by the ratio of radius of ions-10-The packing pattern of ionic bThe 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- =

12、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- = 0.40/1.40 = 0.286 CN = 4-11-The packing tends to have as m- Covalent bondingTwo or more atoms share electrons such that each achieves a stable structureUnlike metallic and ionic bon

13、ding, covalent bonding is directional due to shape of orbitalDirectionalNot close-packedsp3 hybrid orbital: one s orbital and 3 p orbitals are mixed together 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-

14、12- Covalent bondingTwo or more 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 the same plane and form angle of 120o between each other. The unaffected p orbital perpendicular to the p

15、lane 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 angle of 180o between them. ps-13-sp2 hybrid orbital: one s orbi- Bonding strength/force-14- The first

16、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.- Bonding strength/force-14- T- Ionic and covalent bond combinationCaSO4O (8):1s22s22p4S (16): 1s22s22p63s23p4Ca (20): 1s22s22p63s2