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Proceedings Paper

Limiting role of the mass transfer of gases in laser thermochemical reactions on the surface of solids
Author(s): Emil N. Sobol
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Paper Abstract

Growth kinetics of porous layers produced by gas-transfer controlled thermochemical reactions is described. The analysis of heat and mass-transfer problem allows to find the optimal regimes of laser treatment of solids. 1. GROWTH KINETICS OF SURFACE LAYERS The limiting role of gas transfer is characteristic of various processes in volved in the growth of solid layers of a new phase on the exposed surface'' in the course of laser oxidation and reduction of metals and laser synthesis and decomposition of nitrides and other compounds high-temperature superconductors included. When analyzing laser thermochemical reactions taking place in solids and involving the uptake or release of gases the absorbed energy flux q will be considered constant the thermooptical effects2 being disregarded. Let laser radiation incident on the surface of the original substance A give rise to a layer of a new phase B with a thickness of s through which a gas C migrates. We write the pertinent chemical decomposition and synthesis reactions in the form A 4 B + C and A + C ) B respectively. The direction of the reaction is determined by the sign of the Gibbs thermodynamic potential tG /H + TM where tH and tS are the changes of the enthalpy and entropy of the system respectively. According to the chemical equilibrium theory the pressure at the chemical reaction front is related to temperature by the Arrenius law:

Paper Details

Date Published: 1 October 1990
PDF: 7 pages
Proc. SPIE 1352, 1st Intl School on Laser Surface Microprocessing, (1 October 1990); doi: 10.1117/12.23726
Show Author Affiliations
Emil N. Sobol, Research Ctr. for Laser Technology (Russia)


Published in SPIE Proceedings Vol. 1352:
1st Intl School on Laser Surface Microprocessing

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