3.Metal and ceramic structures

3.Metal and ceramic structures - 8/25/2008 MSE 280:...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
8/25/2008 1 MSE 280: Introduction to Engineering Materials Reading: Chapter 3 Part 1 Metal and Ceramic Structures Defining ordered atoms in crystalline solids. Unit cells, unit vectors, Coordinates, directions, planes, close packing… Densities: Crystal density, Line density, Planar density Crystal symmetry and families Crystallography MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 1 Part 2 Ionic crystals. Lattice energy. Silica & silicates. Carbon ENERGY AND PACKING Non dense, random packing Energy typical neighbor bond length Dense, regular packing r bond length typical neighbor bond energy Energy typical neighbor MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 2 Dense, regular-packed structures tend to have lower energy. bond length typical neighbor bond energy From Cal ister 6e resource CD.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8/25/2008 2 Packing atoms together atoms pack in periodic, 3D arrays Crystalline materials. .. typical of: -metals -many ceramics -some polymers Noncrystalline materials. .. Si Oxygen crystalline SiO 2 Adapted from Fig. 3.18(a), Callister 6e. MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 3 atoms have no periodic packing occurs for: -complex structures -rapid cooling noncrystalline SiO 2 " Amorphous " = Noncrystalline Adapted from Fig. 3.18(b), Callister 6e. Crystalline materials: Unit Cell Unit Cel : The basic structural Unit Cell : The basic structural unit of a crystal structure. Its geometry and atomic positions define the crystal structure. Note : more than one unit cell can be chosen for a given crystal but by MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 4 convention/convenience the one with the highest symmetry is chosen.
Background image of page 2
8/25/2008 3 Unit cells and unit vectors b v c v Lattice parameters axial lengths: a, b, c interaxial angles: α, β, γ unit vectors: In general: a b c α β γ a v b v c v MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 5 a v Unit Cells: Bravais Lattices MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 6
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8/25/2008 4 (trigonal) MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 7 Unit cell types Primitive Face-centered Body-centered End-centered MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 8
Background image of page 4
8/25/2008 5 Number of atoms in a unit cell Simple cubic 8 atoms but each atom is shared by 8 unit cells. 1 atom per unit cell MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 9 Coordination Number Number of nearest neighbor atoms MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 10 Simple cubic: coordination number = 6
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8/25/2008 6 Atomic Packing Factor (APF) Vol. of atoms in unit cell Depends on: • Crystal structure. • How “close” packed the atoms are. APF = Vol. of unit cell MSE280 © 2007, 2008 Moonsub Shim, University of Illinois 11 • In simple close-packed structures with hard sphere atoms, independent of atomic radius Close packing of atoms Consider atoms as hard spheres.
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/20/2011 for the course MATERILA 256 taught by Professor Akh during the Spring '10 term at Universitas Sumatera Utara.

Page1 / 34

3.Metal and ceramic structures - 8/25/2008 MSE 280:...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online