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ss_midterm[1] - E-344 Summer 2006 Name: L4$E~AE Midterm...

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Unformatted text preview: E-344 Summer 2006 Name: L4$E~AE Midterm Exam 13 June, 2006 |D#: Honor Pledge: Use the backs of the pages if you need more space. Clearly label any work there with an appropriate question number. 1'. Titanium dioxide (TiOg) is an insulating ceramic material characterized by a gap energy of 3.2 eV. a) sketch a well-labeled energyuband diagram characteristic of TiOz at 0 Kelvin. l "‘3‘ b) calculate the minimum wavelength of electromagnetic radiation (light) to which pure “('7 TiOg is transparent. ‘ M —~ E?" O {afiéiifity a“‘“’“‘*‘"’“” Z Emu» V Mali \srmb 9’"(7%79’5r‘r’kr’r‘ski/:12 We; {out err-gag yr; 30 “(it rum. 1v xii Uth in \‘s New” '4. \l \‘> \ raw mi"? \‘ ‘7 _;\L'\_ \l T" ..“‘:_.-: l'—*___—_+_— 2. A) Obsidian is an igneous rock formed by the rapid cooling of silica-rich lava to form 4‘; an amorphous solid. Using the viscosity-temperature data in the table below, develop 0y an Arrhenius-type model describing the temperature dependence of obsidian viscosity, and evaluate this viscosity at 1500 K. Viscosity of silica—rich lava B) Obsidian consists of approximately 70% SiOz, and the remaining constituents include NaZO, K20, T (K) n (poise) Al203, and various other oxides. Would you expect “/ the viscosity of obsidian at 2000 K to be higher, , 1852 391810 lower, or the same as that of pure silica (SiOz) at 1667 562300 2000 K? Briefly justify your answer. \- mi ' an EU ' 7L“ R + (D Lbfl‘éxfie L710 * -C. 55 q\o 7. \_ \‘-’-‘O\S¥L “flu-— M ; ® CbrbmxmiB 3Q ESTA “ngozs‘; QHGCQ Acié P\ M \®0 ' \.o"m )4 to“ § 5 «Lbunb ~> wLLVéS‘zB .’ L“ N": \‘x’ 82mm) ‘33 ® WLCZUDO V’ 03000:; E351: kcuki. V331 OQD$\ Bu»; M V332. EAUCA‘ W M>¥NUW Cousth m)? page} M PA Okt‘bl-cg MI” k": womb-t FOBIintD—S . WSW cunt; FEM WMWYJ OWOIOEJS3 Mk N5 MY; 6&8 ‘NE Hakim ammuz \‘o w. wm “5% Mafia Emaxcr \M BESPmS‘z TD NH mum; swag 931mm To Wat gag. 3. The monomer unit for Nylon 6,6 is given in the diagram below. l .r't A) Suppose a sample of solid nylon is produced with an average molecular weight of {3/ 67,500 glmoie. What is the average degree of polymerization. 6 \ B) Estimate the total length of the average molecule in this soiid. / C) Would you expect that the actual distance between the ends of a typical nylon \ molecule in this sample are as far apart as you calculated in part B? Briefly explain youranswer. C ‘1‘; 5'0 \ ,. ‘0 ' QC \7 »< \Z = \W R:-/\orl.% .22 u 22 x \ 7.? H2 H2 [fl H2 H2 H2 H 7 O 2 I“ y NVV‘ 'waN 1 x N 28 n HZHZH HZHQHZ ZN n zzé Z? mouohl'd}. _ _. hm - Lil/mil: I ' l _, \ Not-OWL W68 t u - 57” (Wk " . New “V 7% WW I ® i\ (Na.le kWh-t \‘s H500? O.\<~\ \L) emu-2m ‘20 M CL eons News mu Hz. 9:00? “B6 ’hxwzps\ms_ Wat will \u CC 65; OD isoth \NLL harm-“RR, , Wt kl \Jfich B\$w era Maw” . 1 - .. ‘ r u y g\ “R I gut m mfi * 0‘ . t _ .‘ Si! 8 N“ Comp-me at“ new ‘ 7"“ OLE my Lk CO‘ L" L\ $81 " , ‘i"“-lli.'-2Sri« 4 h _ 'W U Wank) Wt. \“l\h§- ‘0“ “if-33$ " fi_________ ’23, {,- 4. (A) On a cubic unit cell, draw the (111) plane. / (B) The (111) plane contains three <110>-type directions. On your diagram in part (A), “2,, C” indicate these three directions and determine their labels using the [hkl] Miller-index / notation. (N (C) Use the Miller—index notation to describe the close-packed directions in : V (i) an FCC crystal. ' (ii) a 800 crystal? 11”“. ® ~ KO”; (1 or; Sp GA Pave. — 4 I____.___._____ d\ %/ 5. Chromium is metallic material with the BCC crystal structure. Its atomic weight is 51.996 g/mole. Quantitativer show that the density of pure chromium is 7.19 g/cm3. ® Suppose a small amount of vanadium, also 800, is added to the chromium as a substitutional alloying element. Would you expect the density to decrease, increase, or \0 stay exactly the same? Briefly justify your answer. 7 a). m‘wmm m r ‘3 gm,» \m Luke‘s '. Q - 0- \7- SN“ Cr «K wksg 0;» W1 7. *‘WS \N‘ \ w F _ . N ,1 9.61%? W1. my“ Huh “ m 6.0212le ENE-“MEL am? a 023*“??? ' :5.) fl: 3-3": Q,‘3(7,§Mo‘ug,\ EE . @AS (0. as 4n A” 2 {jinn-k Mom 34'} \ lfiitfix: WWI—CL New W7" 0‘?- CfiklcolmtukJ ,m. swam mum E‘i’z‘LW-ox‘sfi Nbsmuwf: NT sum Ruo‘nfl: boas NDT rater; \KCCELW NIL URN-tr V N1 Pr k-xfizmr ‘ o Pane. _ ‘i In the following multiple choice problems, circle the one answer which best completes the sentence. 3 points per problem. No partial credit. A 6. Based on the electron energy-level data given in the 7' adjacent table, a is electron in aluminum can be ionized by a photon whose energy is: a 1442??! 1560 b. e 118 600 eV 73 WV e. noflrle—o‘f the above. Aluminum electron energies Level Energy (eV) Q} 7. A covalent bond is stronger than a hydrogen bond by a factor of about: " a. 0.1; b. 1; 100; . 10,000; e. none of the above \0 8. An example of a defect in an othenivise perfect crystal is: W a. a vacancy; b. a grain boundary; c. an interstitial atom; d. none of the above; , b, 'and c. 9. Few ceramics are shaped by deformation-processing methods such as extrusion, forging, or stamping, because: it} . most ceramics are too brittle; . metal-forming equipment isn’t powerful enough to deform ceramic materials; 0. impurities lower the ceramic viscosity; d. ceramicjypically melt at high temperatures; e. all of th ' above. [f_________ \O 10. Cement \)\. / is a ceramic material; is formed by a series of chemical reactions; uses water as an important chemical constitutent; is strong in compression; all of the above. 09.0 .691 7’ 11. Polymer-based materials are increasingly substituted for metals in transportation 67‘ applications, because polymers typically: a. are stronger; b. are stable to much higher temperatures; have a lower density; ' . are better electrical conductors; 9. none of the above. kg, 12. Below its glass transition temperature, atypical thermoplastic polymer: . is ductile; ' t l is brittle; . can flow easily; d. can undergo a large elastic (recoverable) deformation; e. none of the above. 6'); 13. A gel is: / a. a thermoplastic polymer that can be easily recycled when heated; b. a highly crosslinked polymer that repels water and other solvents; (g) a lightly crosslinked polymer that swells when immersed in a solvent like water; . an example of a block copolymer; e. none of the above. @314. An alloy is: a composite made up of metal and ceramic mixed together; ® a metal that contains other metallic or nonmetallic elements; 0. usually shaped by powder-processing methods; d. all of the above; e. none of the above. r*“““‘“‘ 15. (4.3) A pure insulating ceramic can be distinguished from a pure semiconductor based on their relative: band-gap energies; electrical resistivities; interactions with visible light; electrical conductivities; all of the above. gum 16. (3.3) A good example of a metallic alloy is: “nun—n.- a. a sample of pure aluminum (Al); 0:) a sample consisting of a small amount of pure copper (Cu) dissolved into pure AI; . a sample of aluminum oxide (A1203); d. a single alumium atom; e. none of the above. (2 q» 17. Energy bands form in a polyatomic solid, because: a some materials are metals and others are insulators; electron energy levels split to satisfy the Pauli exclusion principle; 0. empty electron orbitals overlap with filled orbitals; d. all ofthe above e. none of the above. @18. The glass transition temperature of window glass is: l a) the same as the melting temperature; l greater than the melting temperature; @bove room temperature; below room temperature; e) none of the above. ...
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ss_midterm[1] - E-344 Summer 2006 Name: L4$E~AE Midterm...

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