Thermal Conductivity of Plasma-Sprayed Aluminum Oxide—

Thermal Conductivity of Plasma-Sprayed Aluminum Oxide—

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Thermal Conductivity of Plasma-Sprayed Aluminum Oxide— Multiwalled Carbon Nanotube Composites Srinivas R. Bakshi, Kantesh Balani, and Arvind Agarwal w Department of Mechanical and Materials Engineering, Florida International University, Miami, Florida Aluminum oxide nanocomposites reinforced with multiwalled car- bon nanotubes (MWNT) were prepared by atmospheric plasma spraying of blended and spray-dried powders. Thermal conduc- tivity was measured using the laser flash technique for tempera- tures between 25 1 and 300 1 C. An aluminum oxide—4 wt% MWNT nanocomposite prepared from the blended powder showed the highest conductivity, followed by aluminum oxide without nanotubes, 8 and 4 wt% MWNT composite prepared from spray-dried powder in that order. The thermal conductivity values obtained are rationalized taking into account the crystallite size, porosity, MWNT content, microstructure, and the interfaces and metastable c -Al 2 O 3 content present in the nanocomposite. I. Introduction T HERMAL conductivity is an important physical property, which is required in modeling heat transfer through solids and structures. It has also been used as a quality control pa- rameter in the production and performance of nuclear fuels 1 and thermal barrier coatings. 2 Carbon nanotubes have shown excel- lent mechanical, thermal, and electrical properties due to which they have been proposed for a myriad number of applications. 3 Multiwalled carbon nanotubes (MWNT) have also shown 4 very high thermal conductivities in excess of 3000 W ± (m ± K) ÿ 1 . Hence, they serve as a ±rst choice of materials as ±llers for ther- mal conductivity enhancement in thermal management materi- als. The thermal conductivity of dense aluminum oxide has been reported 5 to be between 27 and 35 W ± (m ± K) ÿ 1. In our previous work, 6 it has been shown that addition of carbon nanotubes to aluminum oxide resulted in a 43% increase in the fracture toughness. Addition of MWNT is also expected to increase the thermal conductivity of the composites, which is bene±cial for many applications like electronic packaging. It is generally dif±cult to predict the thermal conductivity of plasma-sprayed coatings because of its complicated microstructure, which con- sists of splats, porosity, and interfaces. The goal of this paper is to study the thermal conductivity of plasma-sprayed aluminum oxide—MWNT nanocomposites and rationalize them by taking into account the crystallite size, porosity, MWNT content, ma- trix microstructure, interfaces, and metastable g -Al 2 O 3 content present in the coatings. II. Experimental Procedure (1) Plasma Spraying The samples were fabricated using DC arc plasma spraying with a Praxair SG-100 gun (Praxair Inc., Danbury, CT). The powders were fed internally into the plasma using argon as a carrier gas.
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This note was uploaded on 03/18/2012 for the course PHYSICS 303 taught by Professor Ihn during the Spring '12 term at Swiss Federal Institute of Technology Zurich.

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Thermal Conductivity of Plasma-Sprayed Aluminum Oxide—

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