1. Materials Science at a Glance
Atomic Structure
Sina Askarinejad
1/1
3/25/2016

2. Materials Science and Engineering
Fundamental
Structures
Crystallography
Bonding
Properties
Processing
1mm
Atomic structure
(Angstrom) [1]
Nano-structure
(1-10 nm)
Macrostructure
(1mm- meter)
Micro-structure
(100 nm-1 mm)
[1] A. Navrotsky (1998). "Energetics and Crystal Chemical Systematics among Ilmenite, Lithium Niobate, and Perovskite Structures". Chem. Mater. 10(10): 2787. doi: /cm

3. Materials in Industry Metals:
Hard, opaque, shiny, good thermal and electrical conductivity, heavy.
Ceramics: Inorganic crystalline material, compounded of a metal and a non-metal.
Stiff, brittle, usually not conductive (there are semiconductors and superconductors), light, high-temperature resistance
Glass: A non-crystalline ceramic.
Transparent, brittle, highly resistant to chemical attack, light.
Polymers: Large molecules or macromolecules, composed of many repeated subunits.
Low strength, low stiffness.
Composites: A material made of two or more constituent materials with very different properties.

4. Askeland, D. R. , & Phulé, P. P. (2003)
Askeland, D. R., & Phulé, P. P. (2003). The science and engineering of materials.

5. Atomic Structure of Materials
Structure of atoms:
Electrons (9.11 e-28 gr)
Protons and Neutrons (1.67 e-24 gr each)
Avogadro number: e23 (The number of atoms or molecules in 1 mole)
1 mole of carbon= 1 mole of (6 protons + 6 Neutrons)= 12gr

6. Orbitals and Energy Levels
Shell
Sub-shell K L M N P

7. Electronegativity: The tendency of atoms to absorb electron.

8. Atomic Bonding
Metallic Bonds
Covalent Bonds
Ionic Bonds
Van der Waals

9. Metallic bonds

10. Covalent

11. Ionic Bond
Different atoms

12. Van der Waals Induced dipole & Induced dipole London forces
Debye interaction
Induced dipole & Permanent dipole
Keesom Interaction
Permanent dipole & Permanent dipole

13. Hydrogen bond is a special type of Keesom interaction
Hydrogen bond is a special type of Keesom interaction. It is between hydrogen and N or O or F.
Van der Waals forces are responsible for physical properties of materials such as melting point, glass transition temperature and surface tension.
high melting point and surface tension of water is due to the hydrogen bonding.

14. Mixed Bonding
Usually, the bond between atoms is a mix of different atomic bonds.
Bonds between Iron atoms are a mixture of metallic and covalent bonding.
Bonds between two metallic atoms is intermetallic bond which is a mixture of metallic and ionic bond.

15. Structure and mechanical properties

16. Carbon! One of the most interesting materials in nature
Has allotropes:
Diamond
Graphite
Buckyballs
Carbon nanotubes

17. Diamond Each atom has 4 covalent bonds.
One of the highest melting point materials known: 3550 °C.
One of the highest know thermal conductivity: 2000 W/mk.
Stiffest material in the world: 1100 GPa.
Electrical insulator.
One of the hardest materials in the world. So it is used in cutting tools.

18. Graphite Three covalent bonds and one van der Waals.
High melting point due to the strong covalent bonds.
Lower density than diamond.
It is electrically conductive due to the one free electron.

19. Buckyballs (C60) Each carbon has two single bonds and one double bond.
Extremely strong and superconductive.

20. Carbon Nanotubes (CNT)
Rolled version of a single layer graphite (graphene).
Reinforcement in polymers.
Electrically Conductive.

21. Short-range and long-range order

22. Lattice structures

23. When materials can have more than one crystal structure:
For pure materials: Allotropy (Iron, titanium)
For compound materials: Polymorphism (Silica, Zirconia)

24. Diffraction Techniques
When a beam of x-ray with same magnitude and wavelength, strikes a crystal, it scatter in all directions. Most of these scattered waves will cancel others, however, in specific angles for specific crystallographic structures, they reinforce each other. This is called diffraction.
Bragg’s law: