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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. 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.






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. 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)






4. Emitted light is in phase






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






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






7. High toughness; material resists crack propagation.






8. Occur when lots of dislocations move.






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






10. Width of smallest feature obtainable on Si surface






11. Undergo little or no plastic deformation.






12. 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






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






14. 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






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






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






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






18. 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






19. A high index of refraction (n value) allows for multiple internal reactions.






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






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. 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.






23. 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.






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






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






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






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






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

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






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






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






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






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






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






35. Ohms Law: voltage drop = current * resistance






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






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






38. 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."






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






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






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






42. 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






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






44. Cp: Heat capacity at constant pressure Cv: Heat capacity at constant volume.






45. 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.






46. 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






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






48. Light Amplification by Stimulated Emission of Radiation






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






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