170414_NME220_Lecture6_Engineering

170414_NME220_Lecture6_Engineering - Lecture 6 Nanoscale...

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1 Lecture 6: Nanoscale engineering methods Prof. James M. Carothers April 14, 2017 S17 NME 220
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2 How about scales? How do properties scale? Example 1. (Book p. 37) In general: Properties scale with dimensions that matter! Hints: Property we are looking for is Power density, P / V , V is volume Power output (P) = Force ( F ) x velocity ( v = const.) If we express the length dimension as D , then area has dimension D 2 , etc. Force acts on area A , which is the factor that determines P when v is const. Problem: Engine 2 is n -times smaller than engine 1. If we have n engine 2s: Show that n number of engine 2s outperform engine 1 if the output (i.e. number of engines) is scaled.
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3 How about scales? How do properties scale? Example 1. (Book p. 37) In general: Properties scale with dimensions that matter! Problem: Assume that it is possible to greatly reduce the size of an engine. Consider an engine 1 m on a side that produces 10,000 W of power. Using scaling laws, determine the power of 1,000 engines occupying the same volume as the 1 m engine. Hint: Property we are looking for is Power density, P / V , V is volume Power output (P) = Force ( F ) x velocity ( v = const.) Force acts on area A , which is the factor that determines P when v is const.
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4 How about scales? How do properties scale? Example 1. (Book p. 37) In general: Properties scale with dimensions that matter! Problem: Assume that it is possible to greatly reduce the size of an engine. Consider an engine 1 m on a side that produces 10,000 W of power. Using scaling laws, determine the power of 1,000 engines occupying the same volume as the 1 m engine. Small engine 1/1000 of 1 m on a side has sides (D) = 10 cm (cube root of 1000 cm 3 ) = 1/10 of large motor. Power D 2 . Volume D 3 . Power density D 2 / D 3 1/D. Which means that the smaller motors will have 10X the power density of the larger motors in the same total volume = 10 x 10,000 W = 100,000 W. Or, another approach: Power for the smaller motor = 1/ D 2 = 1/10 2 of the larger motor = 10,000 W x 1/10 2 = 100 W per motor. Total power for 1,000 motors x 100 W per motor = 100,000 W.
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5 Nanoscale engineering methods Bottom-up engineering of materials DNA synthesis (PDFs) Nanoparticles Molecules and self-assembly Thin films Multiphase materials (composites, blends, colloids) Top-down engineering of materials Grinding/Milling Machining Lithographic patterning Dye printing Learning objectives: 1. Difference between bottom-up and top-down engineering. 2. Working knowledge of the basic 'cooking' approaches.
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