Plasma-scan sintering of aluminosilicate sol–gel films

The high temperatures and velocities of plasma jets give them uniquely high heat transfer coefficients and the ability for extremely rapid heat transfer. These characteristics have been applied to use plasma scanning to sinter aluminosilicate films prepared by sol–gel processing. The critical thickness, up to which crack-free films can be obtained, was found to be significantly lower for plasma-scan sintering than for conventional furnace sintering. However, crack-free films above the critical thickness were produced by multiple dipping to produce individual layers below the critical thickness and plasma scanning after each dip. Multilayered aluminosilicate films deposited on steel substrates and plasma-scan sintered for 3 min at 600 °C showed the same microstructure and scratch resistance as that of conventionally furnace-sintered films after 60 min at 600 °C. A process model has been developed for the plasma-scan sintering process that can predict temperature profiles within the film–substrate system and form a basis for process control.