t3s201s04 - EMSE 201 Introduction to Materials Science...

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19 April 2004 Name: S O L U T I O N Department of Materials Science and Engineering 1 of 6 Case Western Reserve University Test #3 — 50 minutes; 100 points; 6 questions; 6 pages; 10% of course grade No calculators or formula sheets are allowed. Use the backs of these sheets if necessary. 1) a) (10 points) Given the mechanical and thermal properties of the following ceramic materials, calculate their thermal shock resistance parameter (TSR) and rank them from highest to lowest. (Even without calculators, you should be able to give one significant digit and the correct order of magnitude.) Material Thermal conductivity, κ (W m –1 K –1 ) Coefficient of linear thermal expansion, α (10 –6 K –1 ) Young’s modulus, E (GPa) Fracture strength, σ f (MPa) sintered silicon nitride 30 3.0 300 600 zirconia with 3 mol% Y 2 O 3 2.0 10 200 1000 SiO 2 glass 1.4 0.4 70 100 TSR ≡σ f κ /E α , units: W m –1 (3 pts formula, 1 pt units) silicon nitride: TSR = 600 × 30/(300 × 3) = 20 × 10 3 (2 pts calculation) zirconia: TSR = 1000 × 2/(200 × 10) = 1 × 10 3 (2 pts calculation) silica glass: TSR = 100 × 1.4/(70 × 0.4) = 5 × 10 3 (2 pts calculation) silicon nitride > silica glass > zirconia b) (12 points) For each material, briefly discuss which properties have the greatest influence on its TSR. For these materials as a group, which category of properties has a greater influence on TSR — thermal properties, or mechanical properties? The moderately high strength of the silicon nitride, coupled with its high thermal conductivity, gives it the highest TSR (3-4 pts). The silica glass, though lowest in conductivity and strength, benefits from a low modulus and a very low thermal expansion coefficient. These properties give it a moderate TSR (3-4 pts). Somewhat paradoxically, the material with the highest fracture strength (zirconia) has the lowest TSR. That is because this material has the highest thermal expansion of the three, coupled with a thermal conductivity almost as low as that of glass (3-4 pts). In these cases, the thermal properties have a greater influence on the TSR than the mechanical properties (1-2 pt).
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19 April 2004 Department of Materials Science and Engineering 2 of 6 Case Western Reserve University 2) In the table below, provide the requested information for the following net electrochemical reaction: Fe + 1 2 O 2 + H 2 O ?? Fe 2 + + 2 OH - a) (4 points) Determine the two electrode reactions (also known as half-cell reactions) from the standard EMF series that, when added together, give this net reaction. b)
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t3s201s04 - EMSE 201 Introduction to Materials Science...

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