1. 5 LOOKING INSIDE MATERIALS Determining atomic and molecular dimensions oExplain how an STM, AFM and SEM work oDetermine resolution, magnification and atomic dimensions from microscope data oEstimate molecular size from experimental data

2. Cotton wool SEM 150x Space shuttle tile SEM 2000x

6. World’s smallest advertisement: STM of xenon atoms

7. STM of iron on copper

8. STM of iron on copper: “The atomic corral”

9. Making the corral

10. STM of metal surface showing instrumentally-induced distortion of atom shapes

11. AFM

13. AFM image of gold 111

14. AFM of rhodium screw dislocations

15. Say hallo to “carbon monoxide man” (STM image)

16. AFM of DNA strand

17. SEM

18. SEM of fruit fly head. Be afraid........... Be very afraid..........

19. SEM of solar spiderWill he catch the fruit fly?

20. SEM of ant

21. SEM of snowflake

22. Fracture behaviour oLearn how to calculate fracture energy oDistinguish between strength and toughness in terms of fracture behaviour of materials oExplain why metals are tough

23. Energy stored in stretched material Energy stored = area under graph = ½ x F x e = ½ x (k x e) x e = ½ x k x e 2

29. Fracture surfaces in metals Which shows ductile fracture, and which shows brittle fracture?

30. Fracture of CFRP in a tennis racquet

32. Composite materials Know the meaning of the term composite material For a range of composite materials (ferroconcrete, bone, CFRP etc.), explain how creating a composite can improve on the properties of the individual components

34. Composite materials Investigate properties of composite materials based on ice and/or jelly

35. Metal microstructures Recognise the various atomic-level structural features present in metals

37. Grain boundaries

38. A dislocation: an incomplete row of atoms

39. Metal microstructures Explain the effects that micro structural features have on the properties of metals

42. Questions on modifying the properties of metals 1. Draw diagrams to illustrate the following: (a) the pinning of a dislocation by a foreign atom (b) a large substitutional impurity atom in a crystal (c) an interstitial atom 2. What common effect(s) on the metal’s properties do all of the modifications described in Q1 have? 3. How can excessive work hardening of a metal be reduced? 4. A metal contains large crystal grains. How could you change the crystal grain size to create smaller grains? 5. Now try Questions 70X from Folio Views

43. Heat treatment of steel Investigate and explain how various heat treatments of steel can affect its properties

44. Stiffness and elasticity Explain stiffness and elasticity in metals, ceramics and polymers

54. Comparisons of materials of different classes(metals, ceramics, polymers) See p112-3 Give an example of a material with (a) giant covalent structure; (b) an ionic structure; (c) metallic structure Explain why ceramics, salts and metals are all stiff, but only metals are ductile and tough Why are polymers generally much less stiff than metals? How can some polymers be made stiffer? Why does rubber get stiffer the more it is stretched?

55. Electrical conductivity Investigate and explain the temperature dependence of the conductivity in metals, semiconductors and insulators

56. copper.swf nichrome.swf