材料科學(xué)專(zhuān)業(yè)英語(yǔ)課件1

1、Correction“Principle quantum number” should be corrected as“Principal quantum number”.-1-Correction“Principle quantum nAtomic Structure Atomic structures electronNucleus Atom consists of nucleus (positive charged) and Electrons (negative charged)H (1): 1s1C (6):1s22s22p2O (8):1s22s22p4Si (14):1s22s2

2、2p63s23p2 Only those electrons which occupy the outermost shell will involve in chemical reaction; called valence electrons The outer shell need to be fully filled for being stable Pauli exclusion principle: only two electrons can occupy the same orbital -2-Atomic Structure Atomic struct Atomic bond

3、s- Metallic bondingThe valence electrons are freely shared by all the atoms in the structure.- Ionic bondingAtom give up one or more electrons positive charge (Cation)Atom accept one or more electrons negative charge (Anion)Coulombic attraction force source of ionic bonding- Covalent bondingTwo or m

4、ore atoms share electrons such that each achieves stability.covalent bonding is directional-3- Atomic bonds- Metallic bondinChapter 2: Crystal Structures Crystalline structure: regular, long range order Amorphous (glass) structure: no long range order-4-Chapter 2: Crystal Structures - Close-Packed S

5、tructures Crystalline structure-5-Close-PackedNon-Close-Packed- Close-Packed Structures Cry- Close-Packed Structures Position aPosition b Crystalline structureLayer ALayer B-6- Close-Packed Structures PosiClose-packed cubic structure-FCC ABCABCFirst Layer ASecond Layer BThird Layer C-7-Close-packed

6、cubic structure-FClose-packed hexagonal structure-HCPFirst Layer ASecond Layer BThird Layer AABAB-8-Close-packed hexagonal structuIn cubic structure, if atom C is shifted to the position circled by the dash line, fcc stacking may be converted to the hcp stacking.-9-In cubic structure, if atom C Latt

7、ice Parameters of the unit cell: axial lengths (a, b, and c)angles between axes(, and )-10- Lattice: means a three-dimensional array of points coinciding with atom positions (or sphere centers).- Unit cell: the smallest group of atoms that shows the geometry of the structure. Lattice Parameters of t

8、he uni- 7 possible unit cell geometriesdistinguish from each other by length of unit cell edges and the angles between the edges-11- 7 possible unit cell geometr-12-12- PositionThe position of an atom is described with reference to the axes of the unit cell and the unit dimensions of the cell E.g. F

9、CC structureabcdea: 0,0,0b: 0,0,1c: 0,1,1d: 1,1,1e: ff:-13- PositionThe position of an a- Crystallographic Directions and Planes (Miller indices) xyz110111112Define direction and planes in unit cellDirection, hkl Draw a vector from original point along the direction to be defined Project it on three

10、 axes multiple three number to get minimum integers Equivalent direction -14- Crystallographic Directions xyzPlanes: (hkl)(111)(110)(010) Find intercepts with x, y, z Get reciprocals Multiple the reciprocals to get minimum integers Equivalent plane -15-xyzPlanes: (hkl)(111)(110)(010- HCP structure M

11、iller indices- Direction uvtwt= - (u+v)-16- HCP structure Miller indicConversion from 3-index system to 4-index system010 in 3-index system becomes 1120 in 4-index system.-17-Conversion from 3-index system- HCP structure Miller indices- Planes (hkil)Basal plane :(0001)Prism plane: (1010)(0110); (110

12、0)i= - (h+k)-18- HCP structure Miller indicDetermination of Miller Indices for a Plane Within a Hexagonal Unit CellTherefore the (hkil) indices are (1101 ).-19-Determination of Miller Indic- Linear density (LD) and close packed directionExample 1: FCC structure110 direction: If the radius of atom is

13、 r:100 direction: 110 is close packed direction(001) plane-20- Linear density (LD) and closExample 2: BCC structure111 direction: If the radius of atom is r:100 direction: 111 is close packed direction(110) plane110 direction: -21-Example 2: BCC structure111 Example 3: simple cubic structure100 is c

14、lose packed direction(100) plane110 direction: 100 direction: -22-Example 3: simple cubic structExample 4: HCP structure(0001) Basal planea1, a2, a3 are close packed directionsa1, a2, a3 directions: a1a2a3c(2110)c = 1.633 a0001 direction-23-Example 4: HCP structure(0001)- Planar density and close pa

15、cked planeExample 1: FCC structure(111) is close packed plane(001) plane(111) plane(011) plane-24- Planar density and close pacExample 2: BCC structure(110) plane(100) plane(110) Has higher planar density than (100)Example 2: BCC structure(110) Example 3: HCP structure(0001) Basal plane(0001) is clo

16、se packed planea1a2a3c(1010) Prism plane Example 3: HCP structure(0001)- Packing densityVolume occupied by atoms/unit cell volume - FCC/HCP structure (they are the same)- BCC structure- Simple cubic structure- Packing densityVolume occupi- Plane spacing: Different crystal has different equation Cubic: - Hexagonal: : d = a : :The distance between