Classification of Materials

1. Classification ofMaterials

2. What is Materials Science and Engineering? What are the fundamental relationships between the apices of the "MSE tetrahedron" AND how can we exploit them to "build a better mousetrap"? Structure (Composition) Processing Performance Properties

3. What is Materials Science and Engineering? Processing How do you make a material? How do you make it in a specific shape? How do you make it do what you want? Structure (Composition) How do you get the structure you want? Every material has a hierarchy of structural levels. How do you characterize these? Properties Why do materials have the properties they do? How can you exploit these? How do you ensure these get transferred to technologies? Performance How to ensure that materials don’t limit technology? How long do materials last? How do materials fail?

4. Learn This You Have 20 Seconds!!! C A = = F G = = E = D = I = B H = =

5. Easier??

6. Material • Webster’s Definition: • The elements or substance or the parts of which something is composed or can be made “Solid Stuff”

7. Material Science

8. History and Materials • Stone Age • 3300BC – 2000BC • Started shaping stone to use as tools and weapons • Bronze Age • 3300BC – 1100BC • Began to use metals • Smelt it to form weapons and tools • Iron Age • 1300BC - 500AD • Began forging Iron and Steel • What age are we in now??????

9. General physical properties of metals, ceramics and polymers……. • State • Magnetism • Density • Viscosity Solid, liquid or gas Physical attraction for iron Mass per unit volume (d = m/v) Resistance of a material to flow. ***Can change with temperature

10. Mechanical Properties……….. • Malleability • Ductility • Strength • Tensile Strength • Hardness • Toughness Ability to be reshaped in all directions without failure. Ability of a material to be stretched Ability to stand up to a force without bending or breaking. Maximum tension that material can absorb before snapping Resistance to being permanently deformed or bent***Brinell Scale (http://en.wikipedia.org/wiki/Brinell_scale ) Shock resistance……how it responds to sudden blows.

11. Mechanical properties cont. 7. Brittleness 8. Elasticity Absence of ductility or failure by sudden fracture Ability to absorb a force and flex in different directions, returning to its original position once force is removed.

12. Electrical Properties • Conductivity • Resistivity Measure of how easily a material allows an electrical current to flow through it Opposite of conductivity. The measure of a materials resistance to the flow of electricity.

13. Chemical properties • Toxicity • Corrosion Resistance • Combustibility Ability to damage living tissue through contact, inhalation, ingestion, or injection. A material's ability to resist deterioration caused by exposure to an environment How easily a material will catch fire and burn

15. Thermal Properties The extent to which a material will expand or contract Thermal Expansion Thermal Conductivity Melting point Glass transition temperature Measure of the rate at which heat will flow through a material. Temperature at which a solid starts to turn into a liquid Point at which a polymer or glass changes from a rigid solid to a viscous fluid.

16. What is Materials Science?

18. Notebook Entry 1: • Name 3 metals 2. List two things each metal is used for. 3. List a few properties of that metal that make it a good choice for the job.

19. METALS and ALLOYS Examples include: Aluminum Steel Cast Iron Titanium Copper

20. Characteristics of Metals • Good electrical conductors • * Allow electricity to flow through easily • Good thermal energy conductor. • * Allow heat energy to pass through easily • High strength • **the resistance to fracture of a material when stressed • High stiffness • * the material's ability to resist elastic deformation • Ductile • * have the ability to be drawn into thin, cohesive strands (wires) • Malleable • * can be flattened (hammered or rolled) into thin sheets.

21. Metals continued….. Alloy – combination of two metals * Usually more desirable characteristics than the parent metals Downside of metals: 1. Usually react with oxygen (oxidizes……rusts) 2. Higher densities 3. Strength weakened as it is heated.

23. Where do metals come from? Native metals – found as pure metals in nature. ex. Gold, Silver, and Copper . (only) Ore – type of rock that contains important elements like metals. ** Must be mined and then have the metal extracted. Lead Ore Iron Ore

24. How to get the metal out of the rock?????? 1. Smelting – the use of heat and a chemical reducing agent to decompose the ore and drive off elements as gasses or slag and leaving just the metal behind.

25. Silicon Smelting… Silicon does not exist on its own in nature. Most of it is bound with oxygen in materials like sand and quartzite and granite rock. The silicon-oxygen bond in quartz is so stable it can only be broken by white heat! Silicon producers reduce high-grade quartz sand to elemental silicon via a carbo-thermic smelting process:

26. Bonding 4 types: a. Metallic b. Ionic c. Covalent d. Intermolecular forces

27. Metallic Bonding: Metallic bond is the reaction between molecules within metals called alkali reactive force. It involves the sharing of free electrons among a lattice of metal atoms.

28. Ionic Bonding: An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions Giving and taking of electrons……

29. Covalent Bond: A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms.

30. Intermolecular Forces: Intermolecular forces are the forces of attractions that exist between molecules in a compound

32. Types of Bonding

33. Types of Bonding

34. Crystalline Structure: The particular repeating arrangement of atoms ( molecules or ions) throughout a material. Crystal structure Unit Cell: The smallest structure that is repeated over and over again in a crystalline material Unit Cell

35. Amorphous Having no long range crystalline pattern or structure Amorphous Crystalline

36. Types of Amorphous materials: Gel Glass Thin Films Nanostructures

37. Unit Cell Definitions Lattice – the regular repetitive, grid-like pattern of atoms in a material. Lattice Point - A point at the intersection of two or more grid lines Coordination Number – the number of atoms touching a particular atom, or the number of nearest neighbors.

38. Example of Lattices Lattice Point

39. Determining number of atoms in a Unit Cell The figure at the right shows the face-centered cubic unit cell of a cubic-close packed lattice. How many atoms are contained in a unit cell? Each corner atom is shared with eight adjacent unit cells and so a single unit cell can claim only 1/8 of each of the eight corner atoms. Similarly, each of the six atoms centered on a face is only half-owned by the cell. The grand total is then (8 × 1/8) + (6 × ½) = 4 atoms per unit cell.

40. Determining number of atoms in a Unit Cell Corners = 1/8 point Body Centered = 1 point Face Centered = ½ point 1 1 2 4

41. Types of Unit Cells: Simple Cubic The simple cubic unit cell is a cube (all sides of the same length and all face perpendicular to each other) with an atom at each corner of the unit cell # of atoms per cell = 1 Coordination number = 6 Ex. Pyrite (Fool’s Gold)

42. Body Centered Cubic (BCC) The body-centered cubic unit cell is a cube (all sides of the same length and all face perpendicular to each other) with an atom at each corner of the unit cell and an atom in the center of the unit cell. # of atoms per cell = 2 Coordination number = 8

43. Face Centered Cubic (FCC) The face-centered cubic unit cell is a cube (all sides of the same length and all face perpendicular to each other) with an atom at each corner of the unit cell and an atom situated in the middle of each face of the unit cell. # of atoms per cell = 4 Coordination number = 12

44. Hexagonal Close Packed Structure ( HCP) The HCP crystal structure is created when atoms of neighboring layers “nest” in the crevices of the layer below them. This nesting creates a crystal that is tightly packed and has few slip planes. Coordination number = 12 Number of atoms = 6 Three spheres are completely contained (100%);two spheres are 50% contained12 spheres are 1/6 contained.

45. HCP Hexagonal Close Pack

46. HCP is more tightly packed….more space efficient

47. NaCl crystal structure:

48. Review……. Coordination number? Number of nearest neighbors (12) Type of unit cell? Face centered cubic (fcc) Number of atoms in this unit cell? 1/8 x 8 = 1 ½ x 6 = 3 Total = 4

49. Review……2 1. What type of crystal structure has the tightest packing? HCP 2. What type of bond is this 3. What type of bond is the weakest? Inter-molecular 4. In a crystal, a point of intersection is called a …. Lattice point

50. Review……..3 • What type of bonding occurs in ceramics? • What type of elements use a metallic bond to stick together? • Give two properties of elements that form using ionic bonds • What word describes a solid with no real crystal pattern? • What type of material is mostly non-crystalline and held together with covalent bonds? • What is the name of the regular repetitive, grid-like pattern of atoms in a material? amorphous Brittle High melting temps Non conductors Don’t corrode metals ionic polymer lattice