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Proceedings Paper

Laser Synthesis Of Powders From Large Molecules
Author(s): G. W. Rice; R. L Woodin
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Paper Abstract

Much of the early work in laser-driven powder synthesis has employed as reactants small molecules (especially hydrides) which have a limited range of potential reaction products. We have been interested in powder synthesis reactions beginning with larger molecular species, in order to access a wider range of reactivity and material compositions, and have found that the broader range of gaseous and solid products obtained provides insight into the details of the laser-driven synthesis process. We have dealt mainly with organosilicon compounds, using a cw CO2 laser for material synthesis and a pulsed CO2 laser to probe the reaction kinetics at short times. The cw reactions are carried out on a flowing gas stream at 145-4000 W/cm2 and an exposure time of 20 ± 10 msec. The pulsed experiments are done in a static cell at low pressure using laser pulse widths of 0.5 psec and intensities of 1 MW/cm2. The pulsed experiments provide data on the initial bond-breaking steps which occurs the reactant molecules heat up. We find that, even at ultimate reaction temperatures of 1500 K in cw experiments, the kinetics of the first reaction steps are important to product formation. We also find that quenching in the cw experiments is sufficiently rapid to allow back-calculation of the pyrolysis temperature from the composition of the light hydrocarbon products. The implications of these results for laser driven powder synthesis are discussed in terms of a general mechanism for reaction initiation, powder growth, and reaction quenching.

Paper Details

Date Published: 31 May 1984
PDF: 10 pages
Proc. SPIE 0458, Applications of Lasers to Industrial Chemistry, (31 May 1984); doi: 10.1117/12.939418
Show Author Affiliations
G. W. Rice, Exxon Research and Engineering (United States)
R. L Woodin, Exxon Research and Engineering (United States)

Published in SPIE Proceedings Vol. 0458:
Applications of Lasers to Industrial Chemistry
Richard L. Woodin; Andrew Kaldor, Editor(s)

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