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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. (sigma)=F/Ai (rho)=(rho)'(1+(epsilon))






2. 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






3. High toughness; material resists crack propagation.






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






5. The ability of a material to absorb heat - Quantitatively: The energy required to produce a unit rise in temperature for one mole of a material.






6. - A magnetic field is induced in the material B= Magnetic Induction (tesla) inside the material mu= permeability of a solid






7. Undergo extensive plastic deformation prior to failure.






8. Specular: light reflecting off a mirror (average) - Diffuse: light reflecting off a white wall (local)






9. They are used to assess properties of ceramics & glasses.






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






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






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






13. A three terminal device that acts like a simple "on-off" switch. (the basis of Integrated Circuits (IC) technology - used in computers - cell phones - automotive control - etc) - If voltage (potential) applied to the "gate" - current flows between th






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






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






16. 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.






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






18. Is reflected - absorbed - scattered - and/or transmitted: Io=It+Ia+Ir+Is






19. Flaws and Defects - They concentrate stress locally to levels high enough to rupture bonds.






20. Failure under cyclic stress 1. It can cause part failure - even though (sigma)max < (sigma)c 2. Causes ~90% of mechanical engineering failures.






21. 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






22. 1. General yielding occurs if flaw size a < a(critical) 2. Catastrophic fast fracture occurs if flaw size a > a(critical)






23. Measures Hardness 1. psia = 500 x HB 2. MPa = 3.45 x HB






24. Defines the ability of a material to resist fracture even when a flaw exists - Directly depends on size of flaw and material properties - K(ic) is a materials constant






25. Specific heat = energy input/(mass*temperature change)






26. Not ALL the light is refracted - SOME is reflected. Materials with a high index of refraction also have high reflectance - High R is bad for lens applications - since this leads to undesirable light losses or interference.






27. 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






28. Sigma=ln(li/lo)






29. Loss of image transmission - You get no image - There is no light transmission - and therefore reflects - scatters - or absorbs ALL of it. Both mirrors and carbon black are opaque.






30. 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.






31. 1. Electron motions 2. The spins on electrons - Net atomic magnetic moment: sum of moments from all electrons.






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






33. 1. Fluorescent Lamp - tungstate or silicate coating on inside of tube emits white light due to UV light generated inside the tube. 2. TV screen - emits light as electron beam is scanned back and forth.






34. A measure of the ease with which a B field can be induced inside a material.






35. Occur due to: restrained thermal expansion/contraction -temperature gradients that lead to differential dimensional changes sigma = Thermal Stress






36. 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






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






38. Materials change size when temperature is changed






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






40. 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






41. - 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






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






43. Ohms Law: voltage drop = current * resistance






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






45. Width of smallest feature obtainable on Si surface






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






47. Large coercivities - Used for permanent magnets - Add particles/voids to inhibit domain wall motion - Example: tungsten steel






48. These are liquid crystal polymers- not your normal "crystal" -Rigid - rod shaped molecules are aligned even in liquid form.

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49. Another optical property - Depends on the wavelength of the visible spectrum.






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