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RESEARCH PAPERS: Radiative Heat Transfer

Radiative Properties of MoO3 and Al Nanopowders From Light-Scattering Measurements

[+] Author and Article Information
S. M. Begley

Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, Urbana, IL 61801

M. Q. Brewster1

Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, Urbana, IL 61801Brewster@uiuc.edu

1

Corresponding author.

J. Heat Transfer 129(5), 624-633 (Jun 28, 2006) (10 pages) doi:10.1115/1.2712476 History: Received June 15, 2005; Revised June 28, 2006

The combustion behavior of nanometer-scale energetic materials is much different than micron size or larger materials. Burning rates up to 950 m∕s have been reported for a thermite composition of nanosized aluminum and molybdenum trioxide. The energy transport mechanisms in the reactive wave are still uncertain. The relative contribution of radiation has not yet been quantified. To do so analytically requires dependent scattering theory, which has not yet been fully developed. Radiative properties for nanoaluminum and nanomolybdenum-trioxide were obtained experimentally by comparing light scattering measurements on a one-dimensional slab of powder with multiple-scattering simulations using Monte Carlo and discrete ordinate methods. The equivalent isotropic-scattering extinction coefficient for close-packed molybdenum trioxide (MoO3 ) nanopowder was found to be 5900±450cm1; the equivalent isotropic-scattering albedo was 0.97±0.035. Aluminum (Al), which proved to be more difficult to work with, had an albedo of 0.35 and 0.38 from two tests. The radiative conductivity based on the MoO3 results is two orders of magnitude less than the diffusive thermal conductivity, indicating that radiation is not a dominant heat transfer mode for the reactive wave propagation of nanothermites under optically thick conditions.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Overview of experimental setup

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Figure 2

Sample position and angle measurement

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Figure 3

Profilometer measurement for MoO3

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Figure 4

Profilometer measurement for Al

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Figure 5

Latex calibration, L=1mm, d=222nm, fv=0.0032, ω0=0.983

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Figure 6

Bidirectional transmission for MoO3 powder in 0.1-mm glass cell

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Figure 7

Bidirectional reflection for MoO3 powder in 0.1-mm glass cell

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Figure 8

Bidirectional transmissivity/reflectivity for MoO3 deposited on glass slide; test 2: path length 5.6μm

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Figure 9

Bidirectional transmissivity/reflectivity of MoO3 deposited on glass slide; test 3: path length 11μm

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Figure 10

Experimental bidirectional properties of aluminum, test 1

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Figure 11

Experimental bidirectional transmission of aluminum, test 1

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Figure 12

Experimental bidirectional properties of aluminum, test 2

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