Technologies for Materials

1. Technologies for Materials

2. Types of Materials • Industrial Chemicals • Metals and alloys • Ceramics and glasses • Polymers and plastic materials • Composite materials • Semi-conductors • Superconductors

3. Some Products that Fulfill Human Needs and Wants Tires http://telstar.ote.cmu.edu/environ/m3/s4/matdecmak.shtml

4. Chemical Substances Required in Large Quantities to Produce Materials that Fulfill Human Needs and Desires http://telstar.ote.cmu.edu/environ/m3/s4/matdecmak.shtml

5. Chemical Industry Broadly defined, the chemical industry accounts for 30-40% of the Gross National Product (GNP) Chenier, Industrial Chemistry, 2nd, VCH, 1992, 5

6. U.S. Production of Top 10 Chemicals (x 109 lb.) - 1997 Sulfuric Acid 95.58 Nitrogen 82.88* Oxygen 64.84* Ethylene 51.08 Lime 42.56 Ammonia 38.39 Propylene 27.53 Phosphoric Acid 26.83 Ethylene Dichloride 26.29 Sulfur 26.24 Total for Top 50 Chemicals 729.36 C&EN, June 29, 1998

7. Metals • Due to reactions with atmospheric O2, most metals occur as cations in ionic substances: Fe2O3 CaCO3,Al2O3 • A pure metal is obtained by its cation gaining electrons (called reduction) • Iron occurs as oxide and is reduced by carbon to produce iron or structural steel (iron with carbon dissolved in it)

8. Production Of Iron and Steel in a Blast Furnace Garland, Chemistry of Our World, MacMillan, NY, 1975, 352

9. Production of Steel Garland, Chemistry of Our World, MacMillan, NY, 1975, 357

10. Electrolytic Production of Al by Hall Process 2 Al2O3 => 4 Al + 3 O2 Garland, Chemistry of Our World, MacMillan, NY, 1975, 351

11. Venugopalan, Chemistry and our World, Harper and Row, NY, 1975, 177

12. Alloys • Solid solutions of elements (usually metals) dissolved in a metal • Alter the properties of the original metal in some desired manner

13. Venugopalan, Chemistry and our World, Harper and Row, NY, 1975, 182

14. Corrosion • Corrosion is oxidation (loss of electrons) of a metal - 20% of iron must be replaced annually due to rusting • Corrosion of iron requires water and O2 • 2 Fe + O2 + 2 H2O => 2 Fe(OH)2 4 Fe(OH)2 + O2 => 2 Fe2O3 + 4 H2O • Prevented by coating iron with paint or Zn (galvanizing) - ZnO more dense

15. Ceramics and Glasses • Ceramics are substances formed by heating mixtures of ionic substances to high temperatures • Frequently involves oxides that are able to resist further oxidation • Most common involve clay Al2O3.2SiO2.2H2O

16. * *Glasses are amorphous (do not have a repeating structure) while ceramics are crystalline (have a repeating structure). Venugopalan, Chemistry and our World, Harper and Row, NY, 1975, 188

17. Ceramic - crystalline structure Glass - amorphous structure Si = red, O = gray, Na = yellow Fine/Beal, Chemistry for Engineers and Scientists, Saunders, NY, 1990, 694

18. Plastics • Long chain-like structures (polymers) composed of individual repeating units (monomers)

19. Polyethylene (polymer) Ethylene (monomer) Tro, 377

20. Polyethylene • Thermoplastic - softens when heated • Addition polymer - monomer units combine without eliminating any atoms • High density (HDPE) has straight chains while low density (LDPE) has branches • Substitution of one or more H atoms produces derivatives with different properties

21. *Recycling is necessary since cannot be broken down by biotic decomposers * Tro, 379

22. Tro, 379

23. Copolymers • Two types of monomers are combined- chains composed of alternating units • Condensation polymer - monomer units combine by expelling a small molecule such as water

24. Nylon Tro, 382

25. Tro, 382

26. Tro, 382

27. Elastomer • Polymer that stretches easily and returns to its original shape (rubber) • Natural rubber is polyisoprene • Vulcanization involves heating rubber with S which cross links chains

28. Natural Rubber Tro, 383

29. Vulcanization - C. Goodyear, 1839 Tro, 383

30. Synthetic Rubber Venugopalan, Chemistry and our World, Harper and Row, NY, 1975, 244

31. Composites • Combination of high strength fibers (of glass, graphite, or ceramics) held together by a polymer • Fiber provides support and polymer protects fibers from breaking • Fiber-glass is glass fiber in polyester - used in car panels, tennis rackets, molded chairs, boat hulls, etc

32. Sports Car with a Composite Body Hill/Kolb, Chemistry for Changing Times, 9th, Prentice Hall, NJ, 2001, 283

33. Semi-conductors • A semiconductor is a substance that conducts electricity to a very limited extent at room temperature, but its conductivity increases with increasing temperature, or when “doped” with appropriate other substances • Si forms covalent bonds with 4 Si atoms around itself and has no electrons free to move and conduct electricity - insulator

34. Si as a Semi-conductor http://electronics.howstuffworks.com/diode1.htm

35. Doping Silicon • Doping (mixing a small amount of another substance into the silicon crystal) increases its electrical conductivity • Elements from 3A and 5A families can be used as dopants for 4A semiconductors

36. 3,5 - Dopants http://electronics.howstuffworks.com/diode2.htm

37. Electron Donor and Acceptor Doped Si-Crystals N-type semi-conductor (negative) P-type semi- conductor (positive) Hill/Kolb, Chemistry for Changing Times, 8th, Prentice Hall, NJ, 1998, 375

38. A diode is the simplest possible semiconductor device. A diode allows current to flow in one direction but not the other. http://electronics.howstuffworks.com/diode3.htm

39. Transistor • A transistor is created by using three doped layers (PNP or NPN) rather than the two layers used in a diode • A transistor can act as a switch or an amplifier - applying a small current to the center layer of the sandwich, causes a much larger current to flow through the sandwich as a whole http://electronics.howstuffworks.com/amplifier1.htm

40. http://electronics.howstuffworks.com/amplifier3.htm

41. http://electronics.howstuffworks.com/amplifier2.htm

42. Silicon Chip • A piece of silicon that can hold thous-ands of transistors • With transistors acting as switches, you can create Boolean gates, and with Boolean gates you can create microprocessor chips and hence computers http://electronics.howstuffworks.com/diode4.htm

43. Superconductors • An element, inter-metallic alloy, or compound that will conduct electricity without resistance below a certain temperature, Tc • Require low temperatures to slow down molecular vibrations sufficiently to facilitate unimpeded electron flow http://superconductors.org/Type1.htmv

44. History of Superconductors Scientific American, January 1994, 18

45. Type 1 superconductor, Tc is 0 - 10 K, consist of metals and metalloids that show some conductivity at room temperature Type 2 superconductor, Tc is 10 - 138 K, consist of metallic compounds and alloys http://superconductors.org/Uses.htm

46. http://superconductors.org/Uses.htm

47. Meissner Effect Meissner effect: The expulsion of all magnetic fields from the interior of a superconductor. Magnetic field induces electric current in the superconductor that produces a magnetic field in the superconductor having same orientation as the magnet. Repulsions of like poles cause the magnet to levitate. External lines of force wrap around the magnet and hold it in place - “magnetic pinning” http://hyperphysics.phy-astr.gsu.edu/hbase/solids/maglev.html

48. The Yamanashi MLX01 MagLev Train A 5-car MLX01 MagLev Train achieved a sustained velocity of 343 miles/hr on 4/14/99 http://superconductors.org/Uses.htm

50. Meissner Effect • When a substance becomes a superconductor, it is repelled by an external magnetic field • If a small magnet is placed on top of a superconductor, the magnet levitates, i.e., it is repelled upward (floats) but is held within the space of the magnetic field (magnetic pinning)