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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. 1. Insulators: Higher energy states NOT ACCESSIBLE due to gap 2. Semiconductors: Higher energy states separated by a smaller gap.






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






3. Diffuse image






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






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






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






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






8. -> fluorescent light - electron transitions occur randomly - light waves are out of phase with each other.






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






10. Second phase particles with n > glass.






11. Ability to transmit a clear image - The image is clear.






12. Light Amplification by Stimulated Emission of Radiation






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






14. Allows flow of electrons in one direction only (useful to convert alternating current to direct current) - Result: no net current flow






15. - 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






16. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






17. 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.






18. Width of smallest feature obtainable on Si surface






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

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20. 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.






21. High toughness; material resists crack propagation.






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






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






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






26. Because of ionic & covalent-type bonding.






27. Metals are good conductors since their _______is only partially filled.






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






29. 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)






30. 1. Diamagnetic (Xm ~ 10^-5) - small and negative magnetic susceptibilities 2. Paramagnetic (Xm ~ 10^-4) - small and positive magnetic susceptibilities 3. Ferromagnetic - large magnetic susceptibilities 4. Ferrimagnetic (Xm as large as 10^6) - large m






31. Is analogous to toughness.






32. 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






33. Stress concentration at a crack tips






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






35. 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






36. Cracks propagate along grain boundaries.






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






38. Sigma=ln(li/lo)






39. 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






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






41. A parallel-plate capacitor involves an insulator - or dielectric - between two metal electrodes. The charge density buildup at the capacitor surface is related to the dielectric constant of the material.






42. Cracks pass through grains - often along specific crystal planes.






43. Without passing a current a continually varying magnetic field will cause a current to flow






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






45. 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






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. No appreciable plastic deformation. The crack propagates very fast; nearly perpendicular to applied stress. Cracks often propagate along specific crystal planes or boundaries.






48. 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






49. Different orientation of cleavage planes in grains.






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