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

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






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






4. 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






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






6. 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)






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






8. Light Amplification by Stimulated Emission of Radiation






9. These materials are relatively unaffected by magnetic fields.






10. Undergo extensive plastic deformation prior to failure.






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






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






13. - 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






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






15. Second phase particles with n > glass.






16. 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






17. 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






18. 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.






19. 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."






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






21. Is analogous to toughness.






22. Emitted light is in phase






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






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






25. 1. Ability of the material to absorb energy prior to fracture 2. Short term dynamic stressing - Car collisions - Bullets - Athletic equipment 3. This is different than toughness; energy necessary to push a crack (flaw) through a material 4. Useful in






26. Sigma=ln(li/lo)






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






28. 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.






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






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






31. 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






32. 1. Stress-strain behavior is not usually determined via tensile tests 2. Material fails before it yields 3. Bend/flexure tests are often used instead.






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






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






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






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






37. Undergo little or no plastic deformation.






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






39. Typical loading conditions are _____ enough to break all inter-atomic bonds






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






41. High toughness; material resists crack propagation.






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






43. There is always some statistical distribution of flaws or defects.






44. Diffuse image






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






46. 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.






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






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






49. Occur when lots of dislocations move.






50. 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.