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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • Match each statement with the correct term.
  • Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. Light Amplification by Stimulated Emission of Radiation






2. 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






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






4. Because of ionic & covalent-type bonding.






5. Occurs at a single pore or other solid by refraction n = 1 for pore (air) n > 1 for the solid - n ~ 1.5 for glass - Scattering effect is maximized by pore/particle size within 400-700 nm range - Reason for Opacity in ceramics - glasses and polymers.






6. - 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






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






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






9. 1. Tensile (opening) 2. Sliding 3. Tearing






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






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






12. Wet: isotropic - under cut Dry: ansiotropic - directional






13. These materials are relatively unaffected by magnetic fields.






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






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






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






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






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






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. Transformer cores require soft magnetic materials - which are easily magnetized and de-magnetized - and have high electrical resistivity - Energy losses in transformers could be minimized if their cores were fabricated such that the easy magnetizatio






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






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






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






26. (sigma)=K(sigma)^n . K = strength coefficient - n = work hardening rate or strain hardening exponent. Large n value increases strength and hardness.






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






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






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






31. 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






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






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






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






35. Emitted light is in phase






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






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






38. 1. Data for Pure Silicon - electrical conductivity increases with T - opposite to metals






39. 1. Necking 2. Cavity formation 3. Cavity coalescence to form cracks 4. Crack propagation (growth) 5. Fracture






40. Diffuse image






41. Measures Hardness - No major sample damage - Each scales runs to 130 but only useful in range 20-100 - Minor load is 10 kg - Major load: 60 kg (diamond) - 100 kg (1/16 in. ball) - 150 kg (diamond)






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






43. Rho=F/A - tau=G/A . Depending on what angle the force is applied - and what angle the crystal is at - it takes different amounts of force to induce plastic deformation.






44. 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."






45. 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.






46. - 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






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






48. 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.






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






50. Growing interconnections to connect devices -Low electrical resistance - good adhesion to dielectric insulators.