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






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






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






4. 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






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






6. Cracks propagate along grain boundaries.






7. 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.






8. 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






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






10. 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.






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






12. 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






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






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






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






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






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






18. High toughness; material resists crack propagation.






19. 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.






20. The size of the material changes with a change in temperature - polymers have the largest values






21. Elastic means reversible! This is not a permanent deformation.






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






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






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






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






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






27. The ability of a material to transport heat - Atomic Perspective: Atomic vibrations and free electrons in hotter regions transport energy to cooler regions - Metals have the largest values






28. Materials change size when temperature is changed






29. - 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






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






31. # of thermally generated electrons = # of holes (broken bonds)






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






33. Occur when lots of dislocations move.






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






35. Diffuse image






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






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






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






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






40. 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






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






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






43. 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.






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






45. 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






46. 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.






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






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






49. These materials are relatively unaffected by magnetic fields.






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







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