Chapter_3 - Primary bonds & secondary bonds Primary...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Ionic Metallic Covalent Electrons: Lost Free Shared Elements: Positive+negative Metallic small diff. in electronegativity Primary bonds & secondary bonds Primary bonds Chapter 3 ME 201: Materials Science, Z. Hao 1 Orientation: Nondirectional Nondirectional Directional Secondary bonding Bonding force is much weaker than primary bonds ± Fluctuating dipole bonds ± Permanent dipole bonds Lectures are available at: Blackboard.odu.edu Æ use your midas account to log in 3.1 Three metallic crystal structures: BCC, FCC, HCP Chapter 3 Crystal Structures & Crystal Geometries Chapter 3 ME 201: Materials Science, Z. Hao 2 3.2 Cubic Unit Cells ¾ Atomic position, direction indices, and miller indices ¾ Volume, planar atomic, and linear atomic density 3.3 Polymorphism and amorphous materials A few Definitions ± Atoms, arranged in repetitive 3-Dimensional pattern, in long range order (LRO) give rise to a crystal solid or crystalline material . Examples: metals, alloys, and certain ceramic materials (diamond) ± Properties of solids depends on crystal structure and bonding force ± An imaginary network of lines, with atoms at intersection of lines, representing the arrangement of atoms is called space lattice . Chapter 3 ME 201: Materials Science, Z. Hao ± Unit cell: the block of atoms which repeats itself to form space lattice. Unit Cell Space Lattice Lattice constants ± a, b, c ± α , β , γ Types of basic unit cells ± Tetragonal ¾ a =b c ¾ α = β = γ = 90 0 ± Rhombohedral ¾ a =b = c ± Monoclinic ¾ a b c ¾ α = β = γ = 90 0 ± Triclinic ¾ a b c ± Seven different types of basic unit cells are necessary to create all space lattices. Table 3.1 on Page 75 Chapter 3 ME 201: Materials Science, Z. Hao ± Cubic Unit Cell ¾ a = b = c ¾ α = β = γ = 90 0 ¾ α = β = γ 90 0 ± Orthorhombic ¾ a b c ¾ α = β = γ = 90 0 a b ¾ α = β = γ = 90 0 ± Hexagonal ¾ a = b c ¾ α = β = γ = 90 0 Variations in basic unit cells ± Variations of basic unit cells Æ more atoms added in some way ¾ Simple ¾ Body Centered ¾ Face Centered ¾ Base Centered Example: Orthorhombic unit cells Chapter 3 ME 201: Materials Science, Z. Hao Simple Base Centered Face Centered ± Fourteen standard unit cells: describe all possible lattice networks Figure 3.2 on Page 76 Body Centered Three principal unit cells ± Cubic Unit Cell ¾ a = b = c ¾ α = β = γ = 90 0 Body Centered Cubic ( BCC ) Simple Cubic Chapter 3 ME 201: Materials Science, Z. Hao 6 ± Hexagonal ¾ a b c ¾ α = β = γ = 90 0 Simple hexagonal Face Centered Cubic ( FCC ) Hexagonal Close Packed ( HCP )
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 ± 90% of the metals have Body Centered Cubic (BCC), Face Centered Cubic (FCC) or Hexagonal Close Packed (HCP) crystal structure. Principal Metallic Crystal Structures ¾ BCC: α iron, vanadium, tungsten, niobium, and chromium. ¾ FCC: copper, aluminum, lead, nickel, and silver.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

Chapter_3 - Primary bonds & secondary bonds Primary...

This preview shows document pages 1 - 3. Sign up to view the full document.

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