MSE 230 Structure Bonding Chapter 3 part 2 Aisling Coughlan Chapter 3 so far Introduced 3 types of packing Simple cubic Body Centered Cubic Face Centered Cubic Atomic Packing Factor Density Radius In General rmetals rceramics rpolymers Why Metals have close packing metallic bonding often large atomic masses Ceramics have less dense packing often lighter elements Polymers have low packing density often amorphous lighter elements C H O Composites have intermediate values Metals Alloys Graphite Ceramics Semicond Polymers Composites fibers 30 20 Platinum Gold W Tantalum 10 Silver Mo Cu Ni Steels Tin Zinc 5 4 3 2 1 0 5 0 4 0 3 Titanium Aluminum Magnesium Based on data in Table B1 Callister GFRE CFRE AFRE are Glass Carbon Aramid Fiber Reinforced Epoxy composites values based on 60 volume fraction of aligned fibers in an epoxy matrix Zirconia Al oxide Diamond Si nitride Glass soda Concrete Silicon Graphite PTFE Silicone PVC PET PC HDPE PS PP LDPE Glass fibers GFRE Carbon fibers CFRE Aramid fibers AFRE Wood Crystals Atoms that are bound together do so in a way that minimizes their energy This most often leads to a periodic arrangement of the atoms in space If the arrangement is purely periodic we say that it is crystalline Polymorphism Metals non metals that have more than 1 crystal structure Crystal Systems Geometry Space lattices Crystal Structures Symmetry Point Group Space Group Crystal Lattice motif basis An atom or group of atoms associated with each lattice point Lattice Translationally periodic arrangement of points in space Space Lattice An array of points such that every point has identical surroundings In Euclidean Space infinite array c a 90 90 90 Pyrite Galena Halite Fluorite Garnet Diamond ISOMETRIC 90 a b c Unique Symmetry Four 3 fold axes a b a Wulfenite Zircon Chalcopyrite Rutile 90 TETRAGONAL 90 a b c c a Unique Symmetry One 4 fold axis a 90 90 b a a b a 120 Apatite Graphite Unique Symmetry One 6 fold axis Corumdum Ruby Sapphire 90 90 Quartz Beryl Emerald c a Sulfur Barite Olivine Topaz 90 90 90 ORTHORHOMBIC c a 90 a b c Unique Symmetry Three 2 fold axes a b a 90 90 90 MONOCLINIC c a 90 90 a b c Unique Symmetry One 2 fold axis a b a Unique Symmetry None TRICLINIC 90 a b c 90 90 b a a 90 System Isometric Tetragonal Hexagonal Orthorhombic Monoclinic Triclinic Axes Angles Unique Symmetry Diagram Examples Crystallographic Points Direction and Planes
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