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Unformatted text preview: 1 Introduction to Materials Science Jan2010 PSMMY 1 BEFORE… n Atomic Structure: quantum numbers, energy levels, valence electrons n Atomic Bondings • Metallic: metals e.g. Cu, Fe, Na, Al, Cr, etc. b/w same atoms, non-directional, sharing of delocalised e • Ionic: metal with non-metal e.g. NaCl, CaBr , etc Jan2010 PSMMY 2 2 b/w dissimilar ions, non-directional, e transfer • Covalent: CH 4 , polymers similar and dissimilar atoms, directional, e sharing • Secondary bonding: physical bonds dipole force, polar interaction, van der Waals - if involving H,hydrogen bonding OVERVIEW FOR TODAY Jan2010 PSMMY 3 n Atomic arrangements n Crystal structures ¡ BCC, FCC, HCP n Theoretical density Learning Outcomes Today… what do I want you to learn? To describe the difference in atomic/molecular structure between crystalline and noncrystalline materials. To draw unit cells for face-centered cubic (FCC), body centered cubic (BCC) and hexagonal close-packed (HCP) crystal Jan2010 PSMMY 4 structures. To derive the relationship between unit cell edge length and atomic radius, for FCC and BCC crystal structures. To calculate the atomic packing factor for FCC and BCC. To compute the densities for metals having FCC and BCC crystal structures given their unit cell dimensions. STRUCTURE OF MATERIALS m Can be examined at 4 levels: m atomic structure: bondings m atomic arrangement: ordering Jan2010 PSMMY 5 m microstructure:tiny features m macrostructure:observable features ATOMIC ARRANGEMENT m Determines the microstructure and behaviour of solids....
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This note was uploaded on 03/20/2010 for the course IMSE tb1073 taught by Professor Musharaf during the Spring '10 term at University of Malaya.
- Spring '10