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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
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  • Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. ...occurs in bcc metals but not in fcc metals.






2. The ability of a material to be rapidly cooled and not fracture






3. As the applied field (H) increases the magnetic domains change shape and size by movement of domain boundaries.






4. heat flux = -(thermal conductivity)(temperature gradient) - Defines heat transfer by CONDUCTION

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5. 1. Metals: Thermal energy puts many electrons into a higher energy state. 2. Energy States: Nearby energy states are accessible by thermal fluctuations.






6. Materials change size when temperature is changed






7. Because of ionic & covalent-type bonding.






8. Plastic means permanent! When a small load is applied - bonds stretch & planes shear. Then when the load is no longer applied - the planes are still sheared.






9. - Metals that exhibit high ductility - exhibit high toughness. Ceramics are very strong - but have low ductility and low toughness - Polymers are very ductile but are not generally very strong in shear (compared to metals and ceramics). They have low






10. Increase temperature - increase in interatomic separation - thermal expansion






11. Liquid polymer at room T - sandwiched between two sheets of glass - coated with transparent - electrically conductive film. - Character forming letters/ numbers etched on the face - Voltage applied disrupts the orientation of the rod- shaped molecule






12. 1. Yield = ratio of functional chips to total # of chips - Most yield loss during wafer processing - b/c of complex 2. Reliability - No device has infinite lifetime. Statistical methods to predict expected lifetime - Failure mechanisms: Diffusion reg






13. Transmitted light distorts electron clouds - The velocity of light in a material is lower than in a vacuum - Adding large ions to glass decreases the speed of light in the glass - Light can be "bent" (or refracted) as it passes through a transparent






14. Hardness is the resistance of a material to deformation by indentation - Useful in quality control - Hardness can provide a qualitative assessment of strength - Hardness cannot be used to quantitatively infer strength or ductility.






15. Reflectiviy is between 0.90 and 0.95 - Metal surfaces appear shiny - Most of absorbed light is reflected at the same wavelength (NO REFRACTION) - Small fraction of light may be absorbed - Color of reflected light depends on wavelength distribution of






16. Dramatic change in impact energy is associated with a change in fracture mode from brittle to ductile.






17. 1. Tc= critical temperature- if T>Tc not superconducting 2. Jc= critical current density - if J>Jc not superconducting 3. Hc= critical magnetic field - if H > Hc not superconducting






18. Growth of an oxide layer by the reaction of oxygen with the substrate - Provides dopant masking and device isolation - IC technology uses 1. Thermal grown oxidation (dry) 2. Wet Oxidation 3. Selective Oxidation






19. Resistance to plastic deformation of cracking in compression - and better wear properties.






20. Found in 26 metals and hundreds of alloys & compounds - Tc= critical temperature = termperature below which material is superconductive.






21. With Increasing temperature - the saturation magnetization diminishes gradually and then abruptly drops to zero at Curie Temperature - Tc.






22. For a metal - there is no ______ - only reflection






23. Emitted light is in phase






24. Undergo little or no plastic deformation.






25. Increase temperature - no increase in interatomic separation - no thermal expansion






26. Allows you to calculate what happened G=F' x cos(lambda) - F=F' x cos(phi)






27. Heat capacity.....- increases with temperature -for solids it reaches a limiting value of 3R






28. Process by which metal atoms diffuse because of a potential.






29. A high index of refraction (n value) allows for multiple internal reactions.






30. Process by which geometric patterns are transferred from a mask (reticle) to a surface of a chip to form the device.






31. Impurities added to the semiconductor that contribute to excess electrons or holes. Doping = intentional impurities.






32. Superconductors expel magnetic fields - This is why a superconductor will float above a magnet.






33. 1. Ductility- % elongation - % reduction in area - may be of use in metal forming operations (e.g. - stretch forming). This is convenient for mechanical testing - but not very meaningful for most deformation processing. 2. Toughness- Area beneath str






34. Occur when lots of dislocations move.






35. 1. Hard disk drives (granular/perpendicular media) 2. Recording tape (particulate media)






36. 1. Impose a compressive surface stress (to suppress surface cracks from growing) - Method 1: shot peening - Method 2: carburizing 2.Remove stress concentrators.






37. These materials are relatively unaffected by magnetic fields.






38. The magnetic hysteresis phenomenon: Stage 1: Initial (unmagnetized state) Stage 2: Apply H - align domains Stage 3: Remove H - alignment remains => Permanent magnet Stage 4: Coercivity - Hc negative H needed to demagnitize Stage 5: Apply -H - align d






39. Energy is stored as atomic vibrations - As temperature increases - the average energy of atomic vibrations increases.






40. Becomes harder (more strain) to stretch (elongate)






41. Dimples on fracture surface correspond to microcavities that initiate crack formation.






42. To build a device - various thin metal or insulating films are grown on top of each other - Evaporation - MBE - Sputtering - CVD (ALD)






43. Measures impact energy 1. Strike a notched sample with an anvil 2. Measure how far the anvil travels following impact 3. Distance traveled is related to energy required to break the sample 4. Very high rate of loading. Makes materials more "brittle."






44. Created by current through a coil N= total number of turns L= length of turns (m) I= current (ampere) H= applied magnetic field (ampere-turns/m) Bo= magnetic flux density in a vacuum (tesla)






45. 1. Imperfections increase resistivity - grain boundaries - dislocations - impurity atoms - vacancies 2. Resistivity - increases with temperature - wt% impurity - and %CW






46. Small Coercivities - Used for electric motors - Example: commercial iron 99.95 Fe






47. - The emission of light from a substance due to the absorption of energy. (Could be radiation - mechanical - or chemical energy. Could also be energetic particles.) - Traps and activator levels are produced by impurity additions to the material - Whe






48. The Magnetization of the material - and is essentially the dipole moment per unit volume. It is proportional to the applied field. Xm is the magnetic susceptibility.






49. Digitalized data in the form of electrical signals are transferred to and recorded digitally on a magnetic medium (tape or disk) - This transference is accomplished by a recording system that consists of a read/write head - "write" or record data by






50. If a material has ________ - then the field generated by those moments must be added to the induced field.