Atomic Bonding and Structure

1
Atomic Bonding and Structure

• MSE 2034/Lecture 3

2
Material Classifications

• Bonding
• Phase Behavior
• Liquid/Solid/Gas
• Crystalline/Amorphous
• Material Classes
• Functional Performance
• Conductor, Insulator, High or Low Permeability,
  Stiff, Compliant, Weak, Strong

3
Bonding

• Ionic
• Covalent
• Metallic
• Secondary Bonding
• Hydrogen Bonding
• Electrostatic Bonding

4
Phase Behavior

• Three Common States of Material Form
• Solid
• Liquid
• Gaseous
• Transitions at Melting Point, Boiling Point
• Heat Capacity Changes without temperature change
  for pure materials

5
Phase Behavior

• Materials as either crystalline or
  non-crystalline based on atomic structure and the
  level of defects in the structure
• Over the next week, we will go more in depth
  regarding specific crystal structures

6
Material Classes Metals

• Classified primarily by metallic bonding
• Al, TI, Fe-C, W, C, Ni, Zn, Pt, Au, Ag
• Generally stiff and strong relative to polymers
  and more ductile than ceramics normally tested at
  room temperature
• Generally good thermal and electrical conductors
  due to metallic bonding

7
Material Classes Ceramics

• Generally formed by ionic bonding
• Sodium Chloride
• Other Salt Crystals
• Silica(SiO2), sand, quartz, glass
• Alumina (Al2O3), sapphire
• K2O, Na2O, BeO
• Strong and brittle, poor thermal and electrical
  conductors

8
Material Classes Polymers

• Examples Polyethylene, Polypropylene,
  Polystyrene
• Carbon Covalent along backbone
• Electrostatic and other secondary forces holding
  chains into a larger agglomeration
• Generally good insulating capacity
• Mechanical properties, a fct. Of material
  processing but lower E than metals, ceramics

9
Scale and Structure

• Individual atomic level
• Clustering of Atoms as in a crystal
• Agglomerations of crystals as in a bulk phase
• Stuff!