fs201f06 - EMSE 201 Introduction to Ma teria ls Science and...

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EMSE 201 — Introduction to Materials Science and Engineering 19 December 2006 Department of Materials Science and Engineering 1 of 12 Case Western Reserve University Name: S O L U T I O N Final Exam — 180 minutes; 300 points; 9 questions; 12 pages; 30% of course grade This exam is to be taken closed-book . You may use a calculator, pencils or pens, eraser, and a straight edge. Handwritten notes on both sides of a single 8.5 ″× 11 sheet of paper are permitted. Please turn in your note page with your test. No other form of stored information is permitted. Write all answers on these pages; use the back if more space is needed. Constants : Boltzmann’s constant, k B = 1.381 × 10 -23 J K -1 = 8.620 × 10 -5 eV K -1 gas constant, R : 8.314 J mol -1 K -1 Charge on an electron, | q e | = 1.602 × 10 -19 C Avogadro’s number, N A = 6.023 × 10 23 mol -1 1) (14 points) Glasses exhibit … (check all that apply): … non-crystalline structure (2 p) … properties more like liquids than like solids (3 pts) … no grain boundaries (2 pts) … very long phonon mean free paths (3 pts) … plasticity above T g (2 pts) … brittleness and relatively high modulus below T g (2 p) 2) (16 points) The band structures of two types of metals are indicated schematically in the sketch at right. State whether each of the following four elements is a “metal I” or a “metal II” based on its electron configuration. Justify your answers. Mg: [Ne]3 s 2 Cu: [Ar]3 d 10 4 s 1 Zn: [Ar]3 d 10 4 s 2 Ag: [Kr]4 d 10 5 s 1 filled states unoccupied states "metal I" VB CB "metal II" “metal I:” Cu and Ag. These are metals with partially filled outermost shells in the electron configuration, which become partially filled outermost bands in the solid. ( 2 pts for each correctly identified element; 4 pts for the explanation.) “metal II:” Mg and Zn. These are metals with filled outermost shells (or subshells), which become filled bands in the solid, but which overlap with empty bands in the solid so as to provide available states for conduction electrons. ( 2 pts for each correctly identified element; 4 pts for the explanation.)
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EMSE 201 — Introduction to Materials Science and Engineering 19 December 2006 Department of Materials Science and Engineering 2 of 12 Case Western Reserve University 3) Answer the following questions, using the data tabulated below for pure silicon and copper at 25 °C. Show your work below; write your answers in the appropriate cells in the table. silicon copper atomic mass, g mol –1 28.09 63.55 mass density, g cm –3 2.33 8.94 structure diamond cubic cubic closest-packed electrical conductivity at 25 °C, Ω –1 m –1 4.0 × 10 –4 6.0 × 10 7 mobility, cm 2 V –1 s –1 electron: 1.35 × 10 3 hole: 1.41 × 10 3 (see Note below) 3.2 × 10 1 number of atoms per unit volume (with units) 5.00 × 10 22 cm –3 8.47 × 10 22 cm –3 carrier concentration (with units) intrinsic: 9.0 × 10 9 cm –3 extrinsic: 5.0 × 10
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fs201f06 - EMSE 201 Introduction to Ma teria ls Science and...

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