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1、Fundamental of Materials Science and Engineering,Fundamental of Materials Scien,Introduction,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 prope
2、rties 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 Ch
3、apter 1 Atomic,Chapter 1: Atomic Bonding,1.1 Atomic structures,Atom consists of a nucleus (positive charged) and electrons (negative charged) Electrons are characterized by four quantum numbers,Principle quantum number: n = 1, 2, .K, L, M, N, O, Orbital quantum number: l = 0, 1, , n-1s, p, d, fMagne
4、tic quantum number: m = l, ., 1, 0, -1, -l Spin quantum number: s:1/2 and -1/2,-3-,Chapter 1: Atomic Bonding1.1 A,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: represen
5、ts the direction of spin.,Pauli exclusion principle: no electron can have the same set of four quantum numbers,-4-,n: determines the position of,Electron # in each shell: 2n2,-5-,nlm# of orbitalMaximum # 10011,Relative energy level of orbitals,6s5p4d5s4p3d4s3p3s2p2s1s,Energy,-6-,Electrons fill the o
6、rbitals with lowest energy first.,Relative energy level of orbit,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):1s22s22p
7、63s23p63d64s2,Only those electrons which occupy the outermost shell will involve in chemical reaction; called valence electrons.,-7-,Examples (electronic structure,1.2 Bonding,- Metallic bonding,The valence electrons are freely shared by all theatoms in the structureElectrons repulse each other keep
8、 atoms in certain distanceElectron and nuclei attract each other bondingCharacters: Close-packed structures in pure metalsDuctilityHigh electric and thermal conductivity Shiny,-8-,1.2 Bonding- Metallic bondingT,- Ionic bonding,Atom gives up one or more electrons positive charge (Cation)Atom accepts
9、one or more electrons negative charge (Anion)Coulombic attraction force source of ionic bondingE.g.: NaCl,Na(11):1s22s22p63s1,Cl(17):1s22s22p63s23p5,For pure ionic bonding, it would be nondirectionalclose-packed.,-9-,- Ionic bondingAtom gives up o,The packing pattern of ionic bonding structures:dete
10、rmined by (i) electrical neutrality(ii) sizes of ionsCoordination number (CN): the number of nearest neighbor atoms/ions surrounding an atom/ion,Not stable,Stable,Determined by the ratio of radius of ions,-10-,The packing pattern of ionic b,The packing tends to have as more CN as possible,2(C+A)2 =
11、(2A)2 + (2A)2,(C+A)2 = 2A2,(C+A)/A = 21/2 = 1.414 C/A = 0.414,Example:,NaCl: R+ = 1.02; R- = 1.81; R+/R- = 1.02/1.81 = 0.564 CN = 6,MgO: R+ = 0.72; R- = 1.40; R+/R- = 0.72/1.40 = 0.514 CN = 6,SiO2: 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
12、bonding,Two or more atoms share electrons such that each achieves a stable structureUnlike metallic and ionic bonding, covalent bonding is directional due to shape of orbital,DirectionalNot close-packed,sp3 hybrid orbital: one s orbital and 3 p orbitals are mixed together to form four new orbitals.
13、Each orbital points to one corner of tetrahedral and form angle of 109.5o between them.,Hybridization,p,s,C, N, O, Cl,-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
14、orbitals are on the same plane and form angle of 120o between each other. The unaffected p orbital perpendicular to the plane,sp1 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 sam
15、e line and form angle of 180o between them.,p,s,-13-,sp2 hybrid orbital: one s orbi,- Bonding strength/force,-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
16、 with distance dU/dr and is zero at r =ro.,- Bonding strength/force-14- T,- Ionic and covalent bond combination,CaSO4,O (8):1s22s22p4S (16): 1s22s22p63s23p4Ca (20): 1s22s22p63s23p64s2,Forming covalent bond between : S and O,Forming ionic bond between SO4 and Ca,-15-,- Ionic and covalent bond comb,- Van der Waals Bonding,Weaker bond other than metallic, ionic and covalent bonds,Molecular polarization,HCl,-16-,- Van der Waals BondingWeaker,
