Solids and Liquids The Microstructure of Solids

The Microstructure of Solids Which one of these is not a crystal?

The Microstructure of Solids Glass is not a crystal but an amorphous solid!

The Microstructure of Solids Condensed matter: Atoms or molecules are closely packed and interact with each other Atoms or molecules do not interact with each other, except for collisions

The Microstructure of Solids Fixed volume No Yes Fixed shape No Yes

The Microstructure of Solids Microstructures microstructrure: the spatial arrangement of atoms and molecules in matter. Solids have one of two possible microstructures Amorphous solid No repeating pattern, or long-range order Crystalline solid Ordered pattern, like bricks in a wall

The Microstructure of Solids Microstructures Solids have one of two possible microstructures Amorphous solid No repeating pattern, or long-range order Crystalline solid Ordered pattern, like bricks in a wall Glasses and most plastics are amorphous solids

The Microstructure of Solids Microstructures Solids have one of two possible microstructures Amorphous solid No repeating pattern, or long-range order Crystalline solid Ordered pattern, like bricks in a wall Glasses and most plastics are amorphous solids Crystalline solids include minerals, gemstones, metals and even some plastics

The Microstructure of Solids Crystals Crystal structures describe: - the distance between atoms or molecules - bond angles between atoms or molecules The salt in your salt shaker is made of little cubic crystals! NaCl crystal

The Microstructure of Solids Water molecules align in six-sided rings The microscopic arrangement of molecules in a crystalline solid can show up in the shape of an object! Snowflakes have six-way symmetry Crystals

The Microstructure of Solids Amorphous solids A-morph-ous “without” “shape” Glasses do not have an ordered structure. Over time, they will sag or deform under their own weight Most glasses are oxide glasses, because they are made mostly of silicon dioxide (silica)

The Microstructure of Solids Amorphous solids A-morph-ous “without” “shape” An amorphous solid is like an “immobile” liquid. As the temperature rises, the amorphous solid becomes softer and behaves more like a liquid. Crystals only melt at one temperature. Glass is an amorphous solid

The Microstructure of Solids Amorphous solids Some solids are metallic glasses By cooling down a metal very, very fast, you can freeze its atoms into a glass. Fancy golf club have heads made of metallic glass, because they transmit energy very well

The Microstructure of Solids Crystal structures A crystal structure describes exactly the 3D repeating pattern of atoms and molecules Some crystals are square (table salt), some are hexagonal (quartz and snowflakes)

The Microstructure of Solids Crystal structures Bravais lattices: fourteen groups of crystal structures used to help group the many different types of crystal structures.

The Microstructure of Solids Crystal structures Calcite, a rhombohedral crystal If they are undisturbed during cooling, crytalline materials tend to form solids along the same geometry as their structure

The Microstructure of Solids Crystal defects Did you know that the beautiful colors in gemstones come from crystal defects? Ruby Sapphire Both sapphires and rubies are crystals of aluminum oxide (Al 2 O 3 ) that contain different types and amounts of impurities

The Microstructure of Solids Crystal defects Crystals are 3-D structures, so defects can occur in up to three dimensions Defects in a crystal structure affect the properties of the crystal

The Microstructure of Solids Crystal defects 0-D defects 1-D defects 2-D defects Point defects (0-D) occur when one atom is different from the rest of the crystal Vacancy: an atom is missing from the crystal structure Interstitial: an extra atom is wedged in between others Substitutional: a different type of atom or molecule from the rest of the crystal structure is present

The Microstructure of Solids Crystal defects 0-D defects 1-D defects 2-D defects The color of ruby comes from chromium (Cr) substitutional defects Substitutional: a different type of atom or molecule from the rest of the crystal structure is present Ruby Al 2 O 3 Chromium atom

The Microstructure of Solids Solids have one of two possible microstructures Amorphous solid No repeating pattern, or long-range order Crystalline solid Ordered pattern, like bricks in a wall